KR20210102088A - Immobilized selenium in a porous carbon with the presence of oxygen, a method of making, and uses of immobilized selenium in a rechargeable battery - Google Patents

Abstract

In a method for manufacturing an immobilized selenium system or body, a selenium-carbon-oxygen mixture is formed. Next, the mixture is heated to a temperature above the melting temperature of the selenium, and then the heated mixture is cooled to ambient or room temperature to form an immobilized selenium system or body.

Description

IMMOBILIZED SELENIUM IN A POROUS CARBON WITH THE PRESENCE OF OXYGEN, A METHOD OF MAKING, AND USES OF IMMOBILIZED SELENIUM IN A RECHARGEABLE BATTERY}

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Patent Application Serial No. 15/434,655, filed February 16, 2017, and also claims the benefit of U.S. Provisional Patent Application Serial No. 62/802,929, filed February 8, 2019 . The disclosure of the foregoing application is hereby incorporated by reference in its entirety.

field of invention

The present application relates to the field of a lithium secondary battery having a high energy density. More particularly, the present application relates to a method for preparing a carbon-selenium nanocomposite material and its application. The present application also relates to immobilized selenium comprising selenium and carbon. It also relates to methods and usefulness for the preparation of immobilized selenium. One of the uses of immobilized selenium is in rechargeable batteries. The present invention is also capable of substantially recovering electrochemical performance, such as specific capacity, when charged at a low rate such as 0.1C-rate, while at the same time being able to substantially recover fast rates (e.g., 10C-rates) with minimal level of fading. ) to a rechargeable battery capable of performing discharge-charge cycling.

Description of the prior art

As human demand for energy increases, secondary batteries having high mass specific energy and high bulk energy density, such as lithium-sulfur batteries and lithium-selenium batteries, have attracted widespread attention. Group 6A elements of the periodic table, such as sulfur and selenium, exhibited a two-electron reaction mechanism in the course of an electrochemical reaction with lithium. Although selenium's theoretical mass specific capacity (675 mAh/g) is lower than that of sulfur (1675 mAh/g), selenium has a higher density (4.82 g/cm ³ ) ^{than sulfur (2.07 g/cm 3 ).} Therefore, the theoretical bulk energy density of selenium (3253 mAh/cm ³ ) is close to that of sulfur (3467 mAh/cm ³ ). At the same time, compared to sulfur, which is close to the electrically insulating material, selenium is electrically semiconducting and exhibits better electrically conductive properties. Thus, compared to sulfur, selenium exhibits higher levels of activity and better utilization efficiency even at higher loading levels, resulting in high energy and power density cell systems. Moreover, the selenium-carbon composite can further improve the electrical conductivity compared to the sulfur-carbon composite to obtain a higher active electrode material.

As described in Patent Publication No. CN104393304A, by passing hydrogen-selenide gas through a graphene dispersion solution, the heat of solvation oxidizes the hydrogen-selenide to selenium while reducing the graphene oxide to graphene. The selenium graphene electrode material thus prepared was prepared in an ether electrolyte system, 1.5M lithium bi-trifluoromethane sulfonimide (LiTFSI)/1,3-dioxolane (DOL) + dimethyl ether (DME) (volume ratio 1: 1) paired with; The charge specific capacity reaches 640 mAh/g (close to the selenium theoretical specific capacity) in one cycle. However, during the charge-discharge process, polyselenide ions dissolve in the electrolyte and exhibit a significant amount of shuttle effect, which causes subsequent capacity decay. At the same time, the procedure for preparing the graphene oxide raw material used in this process is complicated and not suitable for industrial production.

Patent CN104201389B discloses a lithium-selenium battery cathode material using a nitrogen-containing layered porous carbon composite current collector blended with selenium. In preparing a nitrogen-containing layered porous carbon composite current collector, a nitrogen-containing conductive polymer is first deposited or grown on the surface of a sheet of paper, and then alkali activated and high-temperature carbonized to support itself as a network structure of nitrogen having carbon fibers. -creating a containing layered porous carbon composite current collector; Then, such a nitrogen-containing layered porous carbon composite current collector is further compounded with selenium. The deposition method for producing the conductive polymer is complex and the film formation or growth process is difficult to control. The complexity of the manufacturing process is associated with an undesirable high cost.

Moreover, the demand for long life, high energy density, and high power density rechargeable batteries, with the ability to charge and discharge at a fast rate, is driving the demand for electronic, electric/hybrid automotive, aerospace/drone, submarine, and other industrial, military and It continues to grow in consumer applications. A lithium ion battery is an example of a rechargeable battery in the above-mentioned applications. However, with the development of lithium-ion battery technology, the demand for better performance and cycling ability has not been met with lithium-ion batteries.

Atomic oxygen has an atomic weight of 16 and has the ability to transport two electrons. Lithium-oxygen rechargeable batteries have been studied for the purpose of manufacturing high energy density batteries. The cell has the greatest stoichiometric energy density when it contains an oxygen cathode paired with lithium or sodium metal as the anode. However, most of the technical problems in Li//Na-oxygen cells remain unresolved.

Elemental sulfur also belongs to the oxygen group and has the second highest energy density (after oxygen) when paired with a lithium or sodium metal anode. Lithium-sulfur or sodium-sulfur batteries have been widely studied. However, polysulfide ions (intermediates) formed during Li-S or Na-S cell discharging process dissolve in the electrolyte and migrate from the cathode to the anode. Upon reaching the anode, the polysulfide anion reacts with the lithium or sodium metal, resulting in a loss of energy density, which is undesirable for the cell system. Sulfur is also an insulator, requiring a high loading level of carbon material to achieve a minimum level of electrical conductivity. Due to the extremely low electrical conductivity of sulfur, Li/Na-S rechargeable cells are very difficult to discharge or charge at a fast rate.

Summary of the invention

Disclosed herein is a method for preparing a two-dimensional carbon nanomaterial having a high graphitization degree. A two-dimensional carbon nanomaterial is blended with selenium to obtain a carbon-selenium composite material, which is used as a cathode material paired with an anode material containing lithium, and a lithium-selenium battery with high energy density and stable electrochemical performance. create A similar process can be used to further assemble the pouch cell, which also demonstrates excellent electrochemical properties.

Also disclosed is a method for preparing a selenium-carbon composite material with readily available raw materials and a simple manufacturing procedure.

The selenium-carbon composite material described herein can be obtained from a manufacturing method comprising the steps of:

(1) carbonizing an alkali metal organic salt or alkaline earth metal organic salt at a high temperature, followed by washing with dilute hydrochloric acid or some other acid, and drying to obtain a two-dimensional carbon material;

(2) the two-dimensional carbon material obtained in step (1) is mixed with selenium in an organic solution, heated, and the organic solvent is evaporated, and then the selenium is subjected to a multi-stage heat ramping and soaking process ) to obtain a carbon-selenium composite by combining it with a two-dimensional carbon material.

In step (1), the alkali metal organic salt may be selected from one or several of potassium citrate, potassium gluconate, and sodium sucrose. The alkaline earth metal organic salt may be selected from one or both of calcium gluconate and calcium sucrose. High-temperature carbonization may be carried out at 600 to 1000° C., preferably at 700 to 900° C., with a carbonization time of 1 to 10 hours, preferably 3 to 5 hours.

In step (2), the organic solvent is selected from one or several of ethanol, dimethylsulfoxide (DMSO), toluene, acetonitrile, N,N-dimethylformamide (DMF), carbon tetrachloride, and diethyl ether or ethyl acetate. can be; The multi-stage heat ramping and soaking section is followed by a ramping rate of 2 to 10 °C/min, preferably 5 to 8 °C/min, such that the temperature is between 200 °C and 300 °C, preferably between 220 °C and 280 °C, followed by this immersion at temperature for 3 to 10 hours, preferably 3 to 4 hours; It may then refer to heating to 400 to 600° C., preferably to 430 to 460° C., followed by immersion for 10 to 30 hours, preferably 15 to 20 hours.

Also disclosed herein is a lithium-selenium secondary battery including a carbon-selenium composite material. The lithium-selenium secondary battery may further include a lithium-containing anode, a separator, and an electrolyte.

The lithium-containing anode can be one or several of lithium metal, lithiated graphite anode, and lithiated silicon carbon anode materials (graphite and silicon-carbon anode materials and lithium anodes are assembled into a half-cell cell and discharged to lithiate through making graphite anode and lithiated silicon-carbon anode material). The separator (membrane) can be a commercially available membrane (membrane), such as, without limitation, a Celgard membrane, a Whatman membrane, a cellulose membrane or a polymer membrane. The electrolyte may be one or several of a carbonate electrolyte, an ether electrolyte, and an ionic liquid.

the carbonate electrolyte may be selected from one or several of diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and propylene carbonate (PC); one from lithium hexafluorophosphate (LiPF ₆ ), lithium bis(trifluoromethanesulfonyl) imide (LiTFSI), lithium perchlorate (LiClO ₄ ) and lithium bis(fluorosulfonyl) imide (LiFSI) Or it may be selected from several.

For the ether electrolyte, the solvent may be one or several selected from 1,3-dioxolane (DOL), ethylene glycol dimethyl ether (DME) and triethylene glycol dimethyl ether (TEGDME); one from lithium hexafluorophosphate (LiPF ₆ ), lithium bis-(trifluoromethanesulfonyl) imide (LiTFSI), lithium perchlorate (LiClO ₄ ) and lithium bis-fluorosulfonylimide (LiFSI) Or it may be selected from several.

For ionic liquids, the ionic liquid is one or more room temperature ionic liquids [EMIm] NTf2 (1-ethyl-3-methylimidazolium bis trifluoromethane sulfonimide salt), [Py13] NTf2 (N-propyl -N-methylpyrrolidine bis trifluoromethane sulfonimide salt), [PP13] NTf2 (N-propyl-methylpiperidine alkoxy-N-bis trifluoromethane sulfonimide salt); the solute is selected from at least one selected from lithium hexafluorophosphate (LiPF ₆ ), bis(trifluoromethylsulfonyl) imide (LiTFSI), lithium perchlorate (LiClO ₄ ) and lithium bis fluorosulfonylimide (LiFSI) can be

Also described herein is a lithium-selenium pouch cell battery comprising a carbon selenium composite material.

Compared with the prior art, with respect to the manufacturing method of the selenium carbon composite material disclosed herein, the two-dimensional carbon material is readily available at low cost, the manufacturing method is simple, very practical and suitable for mass production, The obtained selenium carbon composite material has the advantage that it exhibits excellent electrochemical properties.

Also disclosed herein is an immobilized selenium (immobilized selenium body) comprising selenium and a carbon skeleton. The immobilized selenium comprises at least one of: (a) at least 9.5 kJ/mole, at least 9.7 kJ/mole, at least 9.9 kJ/mole, at least 10.1 kJ/mole, for selenium particles to exit the immobilized selenium system; It is necessary to obtain sufficient energy to reach a kinetic energy of at least 10.3 kJ/mole, or at least 10.5 kJ/mole; (b) at least 490°C, at least 500°C, at least 510°C, at least 520°C, at least 530°C, at least 540°C, at least 550°C, or at least 560°C to obtain sufficient energy to exit the selenium system to which the selenium particles are immobilized. A higher temperature is required; (c) a carbon skeleton least 500 m ² / g (with a porosity of less than 20 angstroms), 600 m ² / g or more, 700m ² / g or more, 800 m ² / g or more, 900 m ² / g or more, or have a surface area of at least 1,000 m ^{2 /g;} (d) the carbon backbone has a surface area of 20% or less, 15% or less, 10% or less, 5% or less, 3% or less, 2% or less, 1% or less of the total surface area (for pores between 20 angstroms and 1000 angstroms) has

Also disclosed herein is a cathode or rechargeable battery comprising immobilized selenium. Selenium may be doped with other elements, such as, but not limited to, sulfur.

Also disclosed herein are composites comprising selenium and carbon and comprising a platelet morphology having an aspect ratio of at least 1, at least 2, at least 5, at least 10, or at least 20.

Also disclosed herein is a cathode comprising a composite comprising selenium and carbon and comprising a platelet morphology having an aspect ratio of at least 1, at least 2, at least 5, at least 10, or at least 20. Also disclosed herein is a rechargeable battery comprising a composite comprising selenium and carbon and comprising a platelet morphology having the aforementioned aspect ratio.

Also disclosed herein is a rechargeable battery comprising a cathode, an anode, a separator, and an electrolyte. Rechargeable cells can be charged at 0.1C, 0.2C, 0.5C, 1C, 1.5C, 2C, 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C or faster. The cathode may include an element of at least one of a chalcogen group, such as selenium, sulfur, tellurium, and oxygen. The anode may include an alkali metal, an alkaline earth metal, and at least one element of a Group IIIA metal or metals. The separator may include an organic separator or an inorganic separator, and their surfaces may be optionally modified. The electrolyte may include an alkali metal, an alkaline earth metal, and at least one element of a Group IIIA metal or metals. The solvent in the electrolyte solution may include an organic solvent, carbonate-based, ether-based, or ester-based.

The rechargeable battery may have a specific capacity of at least 400 mAh/g, at least 450 mAh/g, at least 500 mAh/g, at least 550 mAh/g, or at least 600 mAh/g. The rechargeable battery may undergo electrochemical cycling for at least 50 cycles, at least 75 cycles, at least 100 cycles, at least 200 cycles, and the like. Rechargeable cells can be subjected to high C-rate charge-discharge cycling (e.g., 5 cycles at 0.1C, 5 cycles at 0.2C, 5 cycles at 0.5C, 5 cycles at 1C, 5 cycles at 2C, 5 cycles at 5C, and 5 cycles at 10C), greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 70% or greater than 80% ^{of the second (2 nd ) discharge specific capacity at a cycling rate of 0.1C.} Battery specific capacity can be maintained. The rechargeable battery may have a coulombic efficiency of at least 50%, at least 60%, at least 70%, at least 80%, or at least 90%. Rechargeable batteries may be used in electronics, electric or hybrid vehicles, industrial applications, military applications such as drones, aerospace applications, marine applications, and the like.

1 is a 50,000X scanning electron micrograph of the carbon material of Example 1;
2 is a 0.1C charge and discharge curve of the lithium selenium battery of Example 1;
3 is a 0.1C charge and discharge curve of the lithium selenium battery of Comparative Example 2;
4 is an optical image of the pouch cell battery of Example 1;
5 is a 0.05C charge and discharge curve of the pouch cell battery of Example 1;
6 is a flow chart of the immobilized selenium manufacturing process;
7 is a scanning electron microscope image of a carbon skeleton prepared by the method of Example 9;
8 is an X-ray diffraction pattern for a carbon skeleton prepared by the method of Example 9;
9 is a Raman spectrum of a carbon skeleton prepared by the method of Example 9;
10A is a graph of cumulative and incremental surface area for a carbon backbone prepared by the method of Example 9;
10B is a graph of cumulative and incremental pore volumes for carbon backbones prepared by the method of Example 9;
11A is a graph of TGA analysis for immobilized selenium prepared by the method of Example 10;
11B is a graph of TGA analysis for an unimmobilized selenium sample prepared by the method of Example 10 using Se-Super P carbon and Se-graphite;
11C is a graph of TGA analysis of an unimmobilized selenium sample prepared using Se-Super P carbon (FIG. 11B) under a flow of argon gas at heating rates of 16°C/min and 10°C/min;
11D shows two different samples of unimmobilized selenium (Se-Super P complex-solid line) and immobilized selenium prepared by the method of Example 10 (228-110 (dotted line) and 115-82-2 (dashed line). ) is a graph of the rate constant against ;
12 is a graph of the Raman spectrum of immobilized selenium prepared by the method of Example 10;
13 is a graph of the X-ray diffraction pattern for immobilized selenium prepared by the method of Example 10;
14 is an SEM image of immobilized selenium prepared by the method of Example 10;
15 is an exploded view of a coin cell cell including a cathode prepared according to the method of Examples 11 or 13;
16 shows a first lithium-selenium coin cell battery of the type shown in FIG. 15 (0.1C) ( FIG. 16A - left) and a second lithium-selenium coin cell battery (0.1C) prepared by the method of Example 12; 1C) is a graph of cycling test results for ( FIG. 16A - right);
17 is a graph of cycling tests for a lithium-selenium coin cell cell of the type shown in FIG. 15 that was prepared by the method of Example 12 at different cycling rates;
18 is a graph of 0.1C cycling test results for a lithium-sulfur-doped selenium coin cell battery of the type shown in FIG. 15 prepared according to Example 13 with a polymer separator;
19 is a graph of 1C cycling test results for a lithium-sulfur-doped selenium coin cell battery of the type shown in FIG. 15 prepared according to Example 13 with a polymer separator;
20 is a SEM image of a three-dimensional interconnected thin-walled porous carbon nanomaterial produced from glucose;
_{21 is a BET N 2} isotherm (a) and pore size distribution (c) for a three-dimensional interconnected thin-walled porous carbon nanomaterial generated from glucose;
22 is a SEM image of a three-dimensional interconnected thin-walled porous carbon nanomaterial produced from a soybean mill;
_{23 is a BET N 2} isotherm (b) and pore size distribution (d) for three-dimensional interconnected thin-walled porous carbon nanomaterials produced from soybean wheat.

With reference to specific examples, the present invention will be further described below. Unless otherwise specified, the experimental methods in the following examples are all conventional; All reagents and materials are available from commercial sources.

Example 1:

(A) Preparation of selenium carbon composite material

After grinding and milling, an appropriate amount of potassium citrate is calcined at 800° C. for 5 hours under an inert atmosphere, and cooled to room temperature. washed to neutral pH with dilute hydrochloric acid; filtration and drying to provide a two-dimensional carbon nanomaterial (FIG. 1); According to a mass ratio of 50:50, the two-dimensional carbon material and selenium are weighed, then stirred, and uniformly mixed with an ethanol solution of selenium; After evaporation of the solvent, the mixture is dried in a drying oven; The dried mixture was heated to 240° C. at 5° C./min and immersed for 3 hours; then continued heating to 450° C. at 5° C./min; immersion for 20 hours; Cooling to room temperature produced a selenium carbon composite material.

(B) Preparation of selenium carbon composite cathode

The prepared selenium carbon composite was subjected to fixed formulation by pulping, coating, drying and other procedures with water, carbon black Super P (TIMCAL) and binder CMC/SBR (weight ratio 1:1) and to obtain a selenium carbon composite cathode.

(C) Lithium-Selenium Battery Assembly

The prepared selenium carbon composite cathode, lithium foil as an anode, Celgard diaphragm as a separator, and 1M LiPF ₆ in EC/DMC as electrolyte were assembled to be a lithium selenium coin cell battery and a lithium selenium pouch cell battery (FIG. 4).

(D) Lithium-Selenium Battery Test

A constant current charge-discharge test is performed on a lithium-selenium coin cell battery and a lithium selenium pouch cell battery using a charge-discharge device. The test voltage range is between 1.0 V and 3.0 V, and the test temperature is 25°C. The level of discharge specific capacity and charge-discharge current is standardly calculated based on selenium mass. The charge-discharge current is 0.1C or 0.05C. The lithium selenium coin charging and discharging curves are shown in FIG. 2, and the specific test results are shown in Table 1 below. The lithium selenium pouch cell test results are shown in FIG. 5 .

Example 2:

The conditions were the same as in Example 1, except that the raw material carbonized for the two-dimensional carbon was sodium citrate. The cell test results are summarized in Table 1 below.

Example 3:

Conditions were the same as in Example 1, except that the raw material carbonized for the two-dimensional carbon was potassium gluconate. The cell test results are summarized in Table 1 below.

Example 4:

The conditions were the same as in Example 1, except that the high-temperature carbonization temperature for the carbon material was 650°C. The cell test results are summarized in Table 1 below.

Example 5:

The conditions were the same as in Example 1, except that the dried mixture was heated to 300° C. at 5° C./min and immersed at this temperature for 3 hours. The cell test results are summarized in Table 1 below.

Example 6:

The conditions were Example 1 except that the dried mixture was heated to 240° C. at 5° C./min and immersed at this temperature for 3 hours, then continued heating to 600° C. and soaked at this constant temperature for 20 hours. same as in The cell test results are summarized in Table 1 below.

Example 7:

The conditions were the same as in Example 1, except that the lithium-Se battery was packed with a lithiated graphite anode instead of a lithium anode sheet. The cell test results are summarized in Table 1 below.

Example 8:

The conditions were the same as in Example 1, except that the lithium-Se battery was packed with a lithiated silicon carbon anode instead of a lithium anode sheet. The cell test results are summarized in Table 1 below.

Comparative Example 1:

Except for using polyacrylonitrile as a raw material, the conditions were the same as in Example 1. The cell test results are summarized in Table 1 below.

Comparative Example 2:

Conditions are the same as in Example 1, except that a one-step compound method is used to prepare selenium and carbon composites. In this example, the dried selenium carbon mixture was heated to 500° C. at 5° C./min and immersed at this temperature for 23 hours to obtain a selenium carbon composite material. The charge-discharge curve of the battery prepared from the selenium carbon composite material thus obtained is shown in FIG. 3 ; The cell test results are summarized in Table 1 below.

[Table 1] Summarized cell test results

Having thus described a method for producing a selenium carbon composite material, for example, a method for producing immobilized selenium and use of immobilized selenium in a rechargeable battery will be described.

Selenium is an element in the same group as oxygen and sulfur, i.e., Group 6 of the Periodic Table of the Elements. Selenium may be advantageous over oxygen and sulfur in terms of their substantially high electrical conductivity. US 2012/0225352 discloses the preparation of Li-Selenium and Na-Selenium rechargeable batteries with good capacity and cycling capacity. However, certain levels of polyselenide anions are shuttling between the cathode and anode of such cells, resulting in additional electrochemical performance that needs to be significantly improved for practical use. Documents related to this field include:

"Electrode Materials for Rechargeable Batteries", Ali Aboulmrane and Khalil Amine, US Patent Application 2012/0225352, Sept. 6, 2012.

“Lithium-Selenium Secondary Batteries Having non-Flammable Electrolyte,” Hui He, Bor Z. Jang, Yanbo Wang, and Aruna Zhamu, US Patent Application 2015/0064575, March 5, 2015.

"Electrolyte Solution and Sulfur-based or Selenium-based Batteries including the Electrolyte Solution", Fang Dai, Mei Cai, Qiangfeng Xiao, and Li Yang, US Patent Application 2016/0020491, Jan. 21, 2016.

"A New Class of Lithium and Sodium Rechargeable Batteries Based on Selenium and Selenium-Sulfur as a Positive Electrode", Ali Abouimrane, Damien Dambournet, Kerena W. Chapman, Peter J. Chupa, Wei Wang, and Khalil Amine, J. Am. Chem. Soc. 2012, 134, 4505-4508.

"A Free-Standing and Ultralong-life Lithium-Selenium Battery Cathode Enabled by 3D Mesoporous Carbon/Graphene Hierachical Architecture", Kai Han, Zhao Liu, Jingmei Shen, Yuyuan Lin, Fand Dai, and Hongqi Ye, Adv. Funct. Mater. , 2015, 25, 455-463.

"Micro- and Mesoporous Carbide-Derived Carbon-Selenium Cathodes for High-Performance Lithium Selenium Batteries", Jung Tai Lee, Hyea Kim, Marin Oschatz, Dong-Chan Lee, Feixiang Wu, Huan-Ting Lin, Bogdan Zdyrko, Wan Il Chao , Stefan Kaskel, and Gleb Yushin, Adv. Energy Mater. 2014, 1400981.

"High-Performance Lithium Selenium Battery with Se/Microporous Carbon Composite Cathode and Carbonate-Based Electrolyte", Chao Wu, Lixia Yuan, Zhen Li, Ziqi Yi, Rui Zeng, Yanrong Li, and Yunhui Huang, Sci. China Mater. 2015, 58, 91-97.

"Advanced Se-C Nanocomposites: a Bifunctional Electrode Material for both Li-Se and Li-ion Batteries", Huan Ye, Ya-Xia Yin, Shuai-Feng Zhang, and Yu-Guo Guo, J. Mater. Chem. A. , May 23, 2014.

"Lithium Iodide as a Promising Electrolyte Additive for Lithium-Sulfur Batteries: Mechanisms of Performance Enhancement", Feixiang Wu, Jung Tae Lee, Naoki Nitta, Hyea Kim, Oleg Borodin, and Gleb Yushin, Adv. Mater. 2015, 27, 101-108.

“A Se/C Composite as Cathode Material for Rechargeable Lithium Batteries with Good Electrochemical Performance”, Lili Li, Yuyang Hou, Yaqiong Yang, Minxia Li, Xiaowei Wang, and Yuping Wu, RSC Adv. , 2014, 4, 9086-9091.

"Elemental Selenium for Electrochemical Energy Storage", Chun-Peng Yang, Ya-Xia Yin, and Yu-Guo Guo, J. Phys. Chem. Lett. 2015, 6, 256-266.

"Selenium@mesomesoporous Carbon Composite with Superior Lithium and Sodium Storage Capacity", Chao Luo, Yunhua Xu, Yujie Zhu, Yihang Liu, Shiyou Zheng, Ying Liu, Alex Langrock, and Chunsheng Wang, ACSNANO , Vol. 7, No. 9, 8003-8010.

Also disclosed herein is immobilized selenium comprising selenium and carbon. Immobilized selenium may include selenium in elemental form or selenium in compound form. Selenium may be doped with other elements such as, but not limited to, sulfur. Immobilized selenium allows for the localization of electrochemically properly functioning elemental selenium atoms without shuttling between the cathode and anode of the cell. Immobilization of selenium allows elemental selenium atoms to gain two electrons during the discharge process and form selenide anions at the fixed positions of the selenium molecules/atoms. The selenide anion can then donate two electrons during the charging process to form elemental selenium atoms. Thus, immobilized selenium can act as an electrochemically active agent for rechargeable cells with specific capacities that can reach stoichiometric levels, and can have coulombic efficiencies that can be greater than 95%, greater than 98%, or up to 100%, , can achieve substantially-improved sustainable cycling capability.

In cells made of immobilized selenium, the electrochemical behavior of elemental selenium atoms and selenide anions during charging is preferably a properly functioning process. Carbon backbones with Sp ² carbon-carbon bonds have delocalized electrons distributed over conjugated 6-membered-ring aromatic π-bonds over G-band graphene-like local networks bound by D-band carbons. In the presence of a potential, such delocalized electrons can flow with little or no electrical resistance across the carbon backbone. Selenium immobilization can also ^{compress the Sp 2} carbon-carbon bonds of the carbon skeleton, resulting in stronger carbon-carbon bonds, possibly leading to improved electronic conductivity within the carbon skeleton network. At the same time, selenium immobilization can also result in compression of the selenium particles, resulting in stronger selenium-selenium chemical and physical interactions, possibly leading to improved electrical conductivity between the immobilized selenium particles. When selenium immobilization promotes both carbon-carbon bonds and Se-Se bonds, the carbon-selenium interactions are also enhanced by compression in addition to the presence of stabilized selenium moieties to which the carbon skeleton can bind. This moiety of selenium can act as an interface layer to successfully immobilize the carbon skeleton-stabilized selenium moiety. Thus, electrons can flow between the carbon skeleton and immobilized selenium with minimal electrical resistance, and thus the electrochemical charge/discharge process can function efficiently in rechargeable batteries. In turn, this allows the rechargeable battery to have a cycling capacity at virtually any practical rate while maintaining a near stoichiometric specific capacity and with a low level of damage to the electrochemical performance of the cell.

The carbon backbone may be porous and doped with another composition. The pore size distribution of the carbon backbone can range between sub-angstroms and a few microns or reach pore sizes where the pore size distribution instrument can be characterized by using _{nitrogen, argon, CO 2 or other absorbents as probing molecules.} The porosity of the carbon backbone may include a pore size distribution that peaks in the range of at least one of the following: between sub-angstroms and 1000 angstroms, or between 1 angstroms and 100 angstroms, or between 1 angstroms and 50 angstroms, or 1 between Angstroms and 30 Angstroms and/or between 1 Angstroms and 20 Angstroms. The porosity of the carbon backbone may further comprise pores having a pore size distribution having one or more peaks in the ranges described in the preceding remarks. Immobilized selenium may favor a carbon skeleton with a small pore size in which electrons can be quickly transferred and collected with minimal electrical resistance, which allows selenium to function more appropriately electrochemically in rechargeable batteries. The small pore size may also provide a larger carbon skeleton surface area through which the first portion of selenium may form a first interfacial layer to the second portion of selenium immobilization. In addition, the presence in the carbon backbone with certain portions of medium-sized pores and certain portions of large-sized pores also results in the loss of lithium ions coordinated solvent molecules from the bulk solvent medium and small pores where they can be transported to the solid phase lithium selenide. It can be advantageous for effective delivery of solvent lithium ions to the region.

The pore volume of the carbon backbone may be a minimum of 0.01 mL/g and a maximum of 5 mL/g, may be between 0.01 mL/g and 3 mL/g, or may be between 0.03 mL/g and 2.5 mL/g, or It may be between 0.05 mL/g and 2.0 mL/g. A pore volume having a pore size of less than 100 angstroms, or less than 50 angstroms, or less than 30 angstroms, or less than 20 angstroms is the total measurement that can be measured using a BET instrument with _{nitrogen, CO 2 , argon and other probing gas molecules.} more than 30%, or more than 40%, or more than 50%, or more than 60%, or more than 70%, or more than 80% of the possible pore volume. The BET determined surface area of the carbon is greater ^{than 400 m 2} /g, or greater than 500 m ² /g, or greater than 600 m ² /g, or greater than 700 m ² /g, or greater than 800 m ² /g, or greater than 900 m ² /g more than g, or more than 1000 m ² /g.

Carbon may also be substantially amorphous, or may be characterized by a very broad peak centered on a d-spacing of about 5 angstroms.

^{The carbon may comprise an Sp 2} carbon-carbon bond with a Raman peak shift characterized by a D-band and a G-band. In one example, the Sp ² carbon-carbon bond of carbon is centered in the Raman spectrum with the D-band centered at 1364 ± 100 cm ^{-1 at FWHM 296 ± 50 cm -1} and the G-band at FWHM about 96 ± 50 cm ^-1 . It is characterized by being centered at 1589 ± 100 cm ^{-1 .} The ratio of the area of the D-band to the G-band may range from 0.01 to 100, alternatively from 0.1 to 50, alternatively from 0.2 to 20.

Carbon can be of any morphology, eg, platelet, sphere, fiber, needle, tubular, irregular, interconnected, agglomerated, discrete or any solid particle. Platelets, fibers, needles, tubulars, or some morphologies with a certain level of aspect ratio may be beneficial in achieving better interparticle contact to improve electrical conductivity, possibly enhancing rechargeable cell performance.

The carbon can be of any particle size with a median particle size from nanometers to several millimeters, or from several nanometers to less than 1000 microns, or from 20 nm to 100 microns.

The nature of the carbon skeleton can affect selenium immobilization, and the interaction between the carbon skeleton surface and selenium particles can affect the performance of rechargeable batteries. ^{The position of the Sp 2} carbon in the carbon skeleton can help achieve Se immobilization. ^{Sp 2} carbons from small carbon skeleton pores may be preferred, which can be quantified by the NLDFT surface area method as discussed in Example 9 herein. The surface area from the carbon skeleton pores of less than 20 angstroms is at least 500 m ² /g, at least 600 m ² /g, at least 700 m ² /g, at least 800 m ² /g, at least 900 m ² /g, or at least 1,000 m ² It can be greater than /g. The surface from the carbon backbone pores between 20 angstroms and 1000 angstroms can be no more than 20%, no more than 15%, no more than 10%, no more than 5%, no more than 3%, no more than 2%, or no more than 1% of the total surface area of the carbon backbone. .

Immobilized selenium may comprise selenium that vaporizes at a higher temperature than elemental selenium, with reference to the following definition of selenium vaporization: elemental selenium in the Se-Super P composite loses 50% of its weight at a temperature of 480°C and ; Elemental selenium in the Se/graphite composite loses its weight by up to 50% of the selenium contained at a temperature of 471°C. The immobilized selenium is at a temperature greater than 480°C, e.g., 490°C or greater, 500°C or greater, 510°C or greater, 520°C or greater, 530°C or greater, 540°C or greater, 550°C or greater, 560°C or greater, 570°C or greater, or loses 50% of its weight at temperatures above 580°C. Selenium in immobilized selenium is 9.5 kJ/mole or higher, 9.7 kJ/mole or higher, 9.9 kJ/mole or higher, 10.1 kJ/mole or higher, 10.3 or higher to overcome bonding and/or intermolecular forces in the immobilized selenium system and escape into the gas phase. It may require a kinetic energy of at least kJ/mole, or at least 10.5 kJ/mole. In one example, the last portion of immobilized selenium to vaporize may require a kinetic energy of 11,635 J/mol or greater (660° C. or greater) to exit the carbon skeleton, and may be important for selenium immobilization, and may be associated with the carbon skeleton and most It can act as an interfacial material between the immobilized selenium molecules of Therefore, this portion of selenium that requires more than 11,635 J/mole of kinetic energy is called interfacial selenium. The amount of interfacial selenium in the immobilized selenium may be at least 1.5%, at least 2.0%, at least 2.5%, or 3.0% of the total immobilized selenium.

The immobilized selenium may comprise selenium with an activation energy higher than that for conventional (unimmobilized) selenium to overcome for selenium to escape from the immobilized Se—C composite system. The activation energy for unimmobilized selenium (Se-Super P composite system) was determined to be about 92 kJ/mole according to ASTM method E1641-16. The activation energy for selenium in immobilized selenium comprising selenium and carbon is at least 95 kJ/mole, at least 98 kJ/mole, at least 101 kJ/mole, at least 104 kJ/mole, at least 107 kJ/mole, or at least 110 kJ/mole. more than a mole The activation energy for selenium in immobilized selenium containing selenium and carbon is 3% or more, 6% or more, 9% or more, 12% or more, 15% or more, or 18% more than the activation energy for selenium in the Se-Super P composite. bigger than that Immobilized selenium may be more stable than unimmobilized selenium, which is why cells comprising immobilized selenium may cycle better electrochemically, possibly with minimal selenium shuttling between the cathode and anode (or removal) because selenium is immobilized in the Se-C complex.

Immobilized selenium may comprise selenium, which may be Raman-inactive or Raman-active, and typically has a Raman peak at ^{255 ± 25 cm -1} , or 255 ± 15 cm ^-1 , or 255 ± 10 cm ^{-1 .} . The Raman relative peak intensity is defined as the Raman peak area at ^{255 cm -1} to the D-band peak area of the carbon Raman spectrum. The immobilized carbon may comprise selenium having a Raman relative peak intensity of at least 0.1%, at least 0.5%, at least 1%, at least 3%, at least 5%. The immobilized selenium may contain at least 5% selenium, at least 10% selenium, at least 20% selenium, at least 30% selenium, at least 40% selenium, at least 50% selenium, at least 60% selenium, or at least 70% selenium.

The immobilized selenium may contain selenium with a red shift from the Raman peak of pure selenium. The red shift is defined by the positive difference between the Raman peak position for immobilized selenium and the Raman peak position for pure selenium. Pure selenium typically has a Raman peak at ^{about 235 cm −1 .} Immobilized selenium has a red shift of the Raman peak of ^{4 cm -1} or more, 6 cm ^-1 or more, 8 cm ^-1 or more, 10 cm ^-1 or more, 12 cm ^-1 or more, 14 cm ^-1 or more, or 16 cm ^{-1 or more.} It may include selenium having The red shift in the Raman peak suggests that there is compression in the selenium particles.

Immobilized selenium may contain carbon that may be under compression. Under compression, electrons can flow with minimal resistance, which facilitates rapid transfer of electrons from selenium anions to selenium for electrochemical processing during the discharge-charge process for rechargeable cells. The D-band and/or G-band in the Raman spectrum for ^{the Sp 2} carbon-carbon bond of the carbon skeleton comprising immobilized selenium ^{is 1 cm -1} or more, 2 cm ^-1 or more, 3 cm ^-1 or more, 4 cm ^-1 or more or 5 cm ^-1 or more may exhibit a red shift.

Immobilized selenium includes selenium, which may have a higher collision frequency than unimmobilized selenium. Such a high collision frequency may result from selenium in the immobilized Se-C system under compression. The collision frequency of selenium in unimmobilized selenium was determined to be ^{about 2.27×10 5 according to ATSM method E1641-16.} The collision frequencies of selenium in immobilized selenium containing selenium and carbon are 2.5×10 ⁵ or more, 3.0×10 ⁵ or more, 3.5×10 ⁵ or more, 4.0×10 ⁵ or more, 4.5×10 ⁵ or more, 5.0×10 ⁵ or more. , 5.5×10 ⁵ or more, 6.0×10 ⁵ or more, or 8.0×10 ⁵ or more. Immobilized selenium has a collision frequency of 10% or more, 30% or more, 50% or more, 80% or more, 100% or more, 130% or more, 150% or more, 180 % or more, or 200% or more. This could lead to better electron conductivity in the immobilized selenium system because of more collisions between selenium species. The immobilized selenium in the Se-C complex will also have a higher collision frequency against the wall of the carbon host (e.g., the carbon skeleton), which may better transfer or harvest electrons from the carbon skeleton during electrochemical cycling, This can also result in cells (comprising immobilized selenium) with improved cycling performance, such as achieving more cycles and/or cycling at much higher C-rates, which is highly desirable.

Immobilized selenium is 1/5 or less, 1/10 or less, 1/50 or less, 1/100 or less, 1/500 or less, or 1/ less of the kinetic rate constant for unimmobilized/conventional selenium. selenium, which is less prone to leaving its host material (carbon), with a kinetic rate constant of 1000 or less. In an example of the invention, immobilized selenium has a kinetic rate constant (50) ^{of 1×10 -10} or less, 5×10 ^-11 or less, 1×10 ^-11 or less, 5× ^10-12 or less, or 5×10 ^{-13 or less.} selenium with less tendency to leave its host material (carbon).

The immobilized selenium may comprise selenium, which may be amorphous as determined by X-ray diffraction measurements. A diffraction peak with a d-spacing of about 5.2 angstroms is relatively smaller or attenuated than for the carbon backbone, eg, 10% attenuated, 20% attenuated, 30% attenuated, or 40% attenuated.

Immobilized selenium can be prepared by physically mixing carbon and selenium, then melting and homogenizing (or mixing or blending) the selenium molecules to achieve selenium immobilization. Physical mixing can be achieved by ball-milling (dry and wet), mixing with mortar and pestle (dry or wet), jet-milling, horizontal milling, friction milling, high shear mixing in the slurry, regular mixing of the slurry using a blade, etc. can A physically mixed mixture of selenium and carbon may be heated to a temperature above the melting point of selenium and below the melting point of carbon. Heating may be performed in an inert gas environment such as, but not limited to, argon, helium, nitrogen, and the like. The heated environment may include air or a reactive environment. Immobilization of selenium can be accomplished by impregnating dissolved selenium into carbon and then evaporating the solvent. Solvents for dissolving selenium may include alcohols, ethers, esters, ketones, hydrocarbons, halogenated hydrocarbons, nitrogen-containing compounds, phosphorus-containing compounds, sulfur-containing compounds, water and the like.

Immobilized selenium can be achieved by melting a large amount of selenium in the presence of carbon and then removing excess unimmobilized selenium.

The immobilized selenium system or body may comprise at least 30%, at least 40%, at least 50%, at least 60%, at least 70%, at least 80%, or at least 90% of the total amount of selenium in the system or body immobilized selenium. . Unimmobilized selenium can vaporize at a lower temperature than immobilized selenium.

The immobilized selenium system or body may comprise immobilized selenium doped with one or more additional/other element(s) from group 6 of the periodic table, such as, for example, sulfur and/or tellurium. Dopant levels can range from a minimum of 100 ppm by weight to a maximum of 85% of the weight of the immobilized selenium system or body.

An exemplary process for making immobilized selenium is shown in FIG. 6 . In the above process, selenium and carbon are mixed together under dry or wet conditions (S1). After the mixture is optionally dried to a powder (S2), the dried powder can optionally be pelletized (S3). The result of step (S1) and optional steps (S2 and S3) produces a carbon skeleton which is the starting material for step (S4). In step S4, selenium is melted into the carbon skeleton. Drying the molten selenium into the carbon skeleton produces the immobilized selenium of step (S5). The preparation and characterization of immobilized selenium will be described later herein with respect to Example 10.

Immobilized selenium can be used as a cathode material for rechargeable batteries. To prepare the cathode, the immobilized selenium can be dispersed in a liquid medium such as, but not limited to, water or an organic solvent. The cathode comprising immobilized selenium may comprise a binder, optionally another binder, optionally an electrical conductivity promoter and a charge collector. The binder may be inorganic or organic. The organic binder may be, for example, a natural product, such as CMC, or a synthetic product, such as, for example, SBR rubber latex. The electrical conductivity promoter may be of a carbon type, such as graphite-derived small particles, graphene, carbon nano-tubes, carbon nano-sheets, carbon black, and the like. The charge current collector may be, for example, an aluminum foil, a copper foil, a carbon foil, a carbon fabric or other metallic foil. The cathode may be prepared by coating an immobilized selenium-containing slurry (or slurries) onto a charge current collector followed by a typical drying process (air drying, oven-drying, vacuum oven-drying, etc.). The immobilized selenium slurry or slurries may be prepared by high shear mixers, general mixers, planetary mixers, double-planetary mixers, ball mills, vertical attritors, horizontal mills, and the like. A cathode comprising immobilized selenium may be pressed or roller-milled (or calendered) prior to its use in a cell assembly.

A rechargeable battery comprising immobilized selenium may comprise a cathode, an anode, a separator and an electrolyte comprising immobilized selenium. The anode may comprise lithium, sodium, silicon, graphite, magnesium, tin and/or a suitable and/or preferred element or combination of elements from Groups IA, IIA, IIIA, etc. of the Periodic Table of the Elements (Periodic Table). The separator may include an organic separator, an inorganic separator, or a solid electrolyte separator. The organic separator may include, for example, a polymer such as polyethylene, polypropylene, polyester, halogenated polymers, polyethers, polyketones, and the like. The inorganic separator may include a glass or quartz fiber, a solid electrolyte separator. The electrolyte may include a lithium salt, a sodium salt or other salt, a salt of Group 1A of the Periodic Table, a salt of Group IIA of the Periodic Table, and an organic solvent. Organic solvents may include organic carbonate compounds, ethers, alcohols, esters, hydrocarbons, halogenated hydrocarbons, lithium-containing-solvents, and the like.

Rechargeable cells comprising immobilized selenium may be used in electronics, electric or hybrid vehicles, industrial applications, military applications such as drones, aerospace applications, marine applications, and the like.

A rechargeable battery comprising immobilized selenium may have a specific capacity of selenium of an active amount of at least 400 mAh/g, at least 450 mAh/g, at least 500 mAh/g, at least 550 mAh/g, or at least 600 mAh/g. have. Rechargeable cells comprising immobilized selenium may undergo electrochemical cycling for at least 50 cycles, at least 75 cycles, at least 100 cycles, at least 200 cycles, and the like.

Rechargeable cells comprising immobilized selenium can be charged at 0.1C, 0.2C, 0.5C, 1C, 1.5C, 2C, 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C or faster. Very high C-rate charge-discharge cycling for more than 30 cycles (e.g., 5 cycles at 0.1C, 5 cycles at 0.2C, 5 cycles at 0.5C, 5 cycles at 1C, 5 cycles at 2C, 5 cycles at 5C) cycle, and 5 cycles at 10 C), the rechargeable battery comprising immobilized selenium has a second discharge specific capacity greater than 30%, greater than 40%, greater than 50%, greater than 60%, at a cycling rate of 0.1C, A battery specific capacity of more than 70% and more than 80% can be maintained.

The following are some examples for explaining the spirit of the present invention. However, these examples should not be construed in a limiting sense.

Example

Feature analysis method

Scanning electron microscope (SEM) images were collected on a Tescan Vega scanning electron microscope equipped with an energy dispersive analysis X-ray (EDX) detector.

Raman spectra were collected by a Renishaw inVia Raman microscope (confocal). Laser Raman spectroscopy is widely used as a standard for characterization of carbon and diamond, providing easily distinguishable features of each different form (allotrope) of carbon (e.g., diamond, graphite, buckyball, etc.) do. Combined with photoluminescence (PL) technology, it provides a non-destructive way to study various properties of diamond, including phase purity, crystal size and orientation, defect levels and structure, impurity types and concentrations, and stress and strain. . In particular, the width (full-width at half maximum, FWHM) of the primary diamond Raman peak at ^{1332 cm −1} as well as the Raman intensity ratio between the diamond and graphite peaks (D-band at ^{1350 cm −1 and 1600 cm −1} ) G-band) is a direct indicator of the quality of diamond and other carbon materials. In addition, stress and strain levels in diamond or other carbon grains and films can be estimated from diamond Raman peak shifts. It is reported that the diamond Raman peak shift rate under hydrostatic stress is about 3.2 cm ⁻¹ /GPa, and the peak shifts to a lower wavenumber under tensile stress and higher wavenumber under compressive stress. The Raman spectra discussed herein were collected using a Renishaw inVia Raman spectrometer with a 514 nm excitation laser. More information on the use of Raman spectroscopy for diamond characterization is also available in the following references: (1) AM Zaitsev, Optical Properties of Diamond , 2001, Springer and (2) S. Prawer, RJ Nemanich, Phil. Trans. R. Soc. Lond. A (2004) 362, 2537-2565.

Data on the BET surface area and pore size distribution of carbon samples were determined by _{nitrogen uptake and CO 2} uptake using a 3Flex (Mircomeritics) equipped with a Smart VacPrep for sample degassing. Samples are typically degassed in a Smart Vac-Prep for 2 hours at 250° C. under vacuum prior _{to CO 2} and N _{2 uptake measurements.} Nitrogen absorption is used to determine the BET surface area. The pore size distribution of the carbon sample was calculated by combining the nitrogen uptake data and the CO _{2 uptake data. For details on combining both N 2} and CO ₂ absorption data to determine the pore size distribution for carbon materials, see: "Dual gas analysis of microporous carbon using 2D-NLDFT heterogeneous surface model and combined adsorption data of N ₂ and CO ₂ ", Jacek Jagiello, Conchi Ania, Jose B. Parra, and Cameron Cook, Carbon 91 , 2015, page 330-337.

Data for thermogravimetric analysis (TGA) and TGA-differential scanning calorimetry (DSC) for immobilized selenium samples and control samples were measured by a Netzsch Thermal Analyzer. TGA analysis was performed under an argon flow rate of ˜200 mL/min at 16° C./min, 10° C./min, 5° C./min, 2° C./min, 1° C./min and other heating rates. For consistency, a typical amount of immobilized selenium sample used under TGA analysis was about 20 mg.

The activation energy and collision frequency of immobilized and unimmobilized selenium were determined by TGA according to the procedure described in ASTM Method E1641-16.

X-ray diffraction results for different carbon, Se-carbon samples and immobilized selenium were collected on a Philip diffractometer.

Cell cycling performance for rechargeable cells comprising immobilized selenium was tested on a Lanhe CT2001A cell cycling tester. The charge and discharge current of a rechargeable battery containing immobilized selenium is determined by the amount of selenium contained in the immobilized selenium and the cycling rate (0.1C, 0.5C, 1C, 2C, 3C, 4C, 5C, 10C, etc.) became

Example 9: Synthesis and Characterization of the Carbon Backbone

To form the primary residue, a charge of 260 g of potassium citrate was placed in a crucible and the crucible was placed in a quartz tube inside a tubular furnace. A stream of argon gas was flowed into the furnace and the furnace was heated from room temperature (˜20-22° C.) to 600° C. at 5° C./min. After the furnace was held at this temperature for 60 minutes, the furnace was closed and the charge was removed from the crucible after furnace cooling to recover 174.10 grams of processed residue. The same process as described for the primary residue was repeated separately for charges of 420 and 974 grams of potassium citrate to form secondary and tertiary processed residues. The resulting secondary and tertiary processed residues weighed 282.83 grams and 651.93 grams, respectively.

1108.9 grams from these three processed residues were combined together into a crucible and placed in a quartz tube inside a tubular furnace, and a flow of argon gas was flowed into the furnace. The furnace was heated to 800° C. at 5° C./min. The furnace was held at 800° C. for 1 hour. The furnace was allowed to cool, the crucible was removed from the quartz tube, and 1085.74 grams of the primary final residue were then recovered.

Following the same procedure described in this example (800° C.), a charge of 120 grams of potassium residue introduced into the furnace produced about 77 grams of secondary final residue (800° C.).

The combination of the primary and secondary final residues produced approximately 1,163 grams of tertiary final residue.

1,163 grams of the tertiary final residue were then mixed with 400 ml of water to form a slurry, which was divided approximately equally into four 2-liter beakers. The pH of each slurry was determined to be greater than 13. Next, a concentrated hydrochloric acid solution was added to each beaker with an explosion of carbon dioxide, which sank at a pH of less than about 5. More hydrochloric acid solution was added to get a pH of about 1.9. The slurry was then filtered and washed to give a cake, which was dried in an oven at 120° C. for about 12 hours and then vacuum dried at 120° C. for 24 hours to yield 4 carbon skeleton samples, a total of about 61.07 grams. .

These carbon skeleton samples were characterized by SEM, XRD, Raman, BET/pore-size-distribution. The SEM result for one carbon skeleton is shown in FIG. 7 . The surface morphology of typical carbon skeleton particles prepared by the process described in this example has a sheet-like morphology, whose sheet edges are interconnected with a sample thickness of between 500 nm and 100 nm and a sample width (or length) of 0.5 It is between μm and 2 μm and thus the aspect ratio (defined as the ratio of the longest dimension of the sample width (or sheet length) to the sample thickness) is 1 or more, for example, an aspect ratio of 5 or more, or an aspect ratio of 10 or more.

The X-ray diffraction pattern of one carbon skeleton shown in FIG. 8 indicates that the carbon skeleton is substantially amorphous in phase. However, this shows that the broad diffraction peak is centered near 2θ of about 17°, indicating a d-spacing of about 5.21 angstroms.

The results of Raman scattering spectroscopy for one carbon skeleton are shown in Fig. 9, which shows the D-band at about 1365 cm ^-1 (curve 1) and the G ^{-band at about 1589 cm -1 with FWHMs of 296 and 96 cm -1 , respectively. Shows the Sp 2} carbon with a band (curve 2). Both the D-band and the G-band represent a mixture of Gaussian and Lorentian distributions. The D-band has about 33% Gaussian distribution, and the G-band has about 61% Gaussian distribution. The ratio of the area for the D-band to the area for the G-band is about 3.5.

The BET surface area of one carbon skeleton was determined to ^{be 1,205 m 2 /g by nitrogen absorption.} Incremental pore surface area versus pore width is plotted in FIG. 10A using the NLDFT method, indicating a cumulative pore surface area of ^{1,515 m 2 /g.} The discrepancy between the BET surface area and the NLDFT surface area is that the NLDFT distribution is calculated with both _{nitrogen and CO 2 uptake data;} This _{may result from the fact that CO 2} molecules can enter pores that are smaller than those that nitrogen molecules enter. The NLDFT surface area of the pore peak at 3.48 angstroms is 443 m ² /g, at 5.33 angstroms 859 m ² /g and at 11.86 angstroms (up to 20 angstroms) 185 m ² /g, for a total of 1,502 for pores below 20 angstroms. m ² /g, but the NLDFT surface area from pores between 20 angstroms and 1000 angstroms is only 7.5 m ² /g, and the surface area from pores above 20 angstroms is only about 0.5% of the total surface area.

The pore size distribution of the carbon skeleton samples was determined by _{nitrogen uptake and CO 2 uptake.} The absorption results from nitrogen uptake and CO ₂ uptake were combined to produce the pore-size-distribution shown in FIG. 10B . The relationship of incremental pore volume (mL/g) versus pore width (angstroms) indicates that there are three major peaks located at 3.66 angstroms, 5.33 angstroms and 11.86 angstroms; The relationship of cumulative pore volume (mL/g) to pore width (angstroms) is that there are about 0.080 mL/g pores under a peak of 3.66 angstroms and about 0.240 mL/g pores under a peak of 5.33 angstroms and a peak of 11.86 angstroms. about 0.108 mL/g pores under .

Example 10: Preparation and Characterization of Immobilized Selenium

0.1206 grams of selenium (representing the bulk properties of selenium) were included in an agate mortar and pestle set and 0.1206 grams of carbon skeleton prepared according to Example 9 were included in the same agate mortar and pestle. The mixture of selenium and carbon skeleton is manually milled for about 30 minutes and the milled mixture of selenium and carbon skeleton is transferred to a stainless steel die (10 mm diameter). The mixture in the die is compressed to a pressure of about 10 MPa to form pellets of the mixture. The pellets are then loaded into a sealed container in the presence of an inert environment (argon) and the sealed container containing the pellets is placed in an oven. An oven containing a sealed container containing the pellets is heated, for example, to 240° C. (above the melting temperature of selenium) for 12 hours. However, the use of a combination of a temperature above the melting temperature of selenium with a time sufficient to cause the selenium and carbon to react partially or fully to react and form immobilized selenium having some or all of the characteristics described herein is contemplated for use. . Next, the pellets are brought back to room temperature and then the pellets are removed from the container. The pellets taken out were the immobilized selenium of Example 10.

The immobilized selenium of this Example 10 was then characterized by TGA-DSC and TGA. TGA-DSC analysis results were collected for immobilized selenium under a stream of 200 ml/min of argon gas at a heating rate of 10°C/min. There is no observable endothermic DSC peak at a temperature near the melting point of selenium (about 230° C.), which indicates that the immobilized selenium of Example 10 should have a melting point at 230° C. where an endothermic peak should exist. It is different from the bulk-form.

Investigation revealed that the TGA-DSC data were unreliable when the heating temperature reached a point where selenium molecules began to escape from the TGA-DSC sample crucible (graphite or ceramic). Because of this, gaseous selenium molecules (from the sample crucible) appear to enter the stream of argon carrier gas and react with the TGA-DSC platinum sample holder, which distorts the actual TGA-DSC thermochemical behavior. Selenium molecules released from the sample crucible reacting with the platinum sample holder result in lower weight loss in this temperature region. Then, when the heating temperature reaches a point exceeding 800° C., the selenium-platinum complex in the platinum sample holder is released into the gas phase. Complete selenium release can occur at 1000°C. This investigation used most of the immobilized selenium samples of this Example 10. Therefore, a fresh sample (~16 grams) of immobilized selenium was prepared using the same process as described earlier in this Example 10.

The thermochemical behavior of this novel immobilized selenium sample was studied by TGA analysis, which uses a ceramic sample holder covering a very small thermocouple used for TGA analysis. The TGA analysis results for this new immobilized selenium sample were obtained from selenium-carbon composites (50-50 Se-Super P carbon composites and Se-graphite (ground graphite) in the same process as the preparation of immobilized selenium in Example 10). made) are shown in Figure 11a together with the results of TGA analysis (Figure 11b). Super P is a commercial grade carbon black widely used in the lithium-ion battery industry. The pulverized graphite was prepared by pulverizing Poco 2020 graphite. The TGA analysis data are also summarized in Table 2 below.

[Table 2]

The immobilized selenium may have an initial weight loss temperature starting at about 400° C. and for Se-Super P carbon composites and Se-graphite carbon composites may have an initial weight loss temperature starting at about 340° C.; The mid-point weight-loss temperature for immobilized selenium can be about 595° C. versus (vs.) 480° C. for Se-Super P composites and 471° C. for Se-graphite composites; The major weight loss was completed at about 544 °C for Se-Super P composites and Se-graphite composites, and at 660 °C for immobilized selenium. Se-Super P carbon composites and Se-graphite carbon composites show less than 0.6% weight loss between 560°C and 780°C, while immobilized selenium shows about 2.5% of the major weight loss from the bottom (~660°C to 1000°C). % weight loss. These results show that unimmobilized selenium (Se-Super P carbon composite and Se-graphite composite) has no more than 1.2% of the total selenium that can escape from the composite at temperatures above 560°C, whereas immobilized selenium has temperatures above 660°C. suggest that it has about 5.0% of the total selenium that can escape from the carbon skeleton. The following details are provided to give examples that provide an understanding of thermochemical behavior. However, these details should not be construed in a limiting sense.

As an example of thermochemical behavior Using the data of the TGA mid-weight loss temperature, as the heating temperature increased, the kinetic energy of selenium molecules in Se-Super P complex and Se-graphite complex showed that these selenium molecules overcome the intermolecular interactions between selenium molecules and The selenium increases to a level that has enough energy to escape from the liquid phase. where, kinetic energy = 3RT/2, where: R is the gas constant and T is the temperature in Kelvin.

It was observed that the average kinetic energy of the selenium molecule for the Se-Super P complex was measured to be 9,391 J/mol when the selenium molecule escaped from the mixture of the Se-Super P complex. However, immobilized selenium needs to gain more energy in order for selenium to have an average kinetic energy of about 10,825 J/mol for it to leave the carbon skeleton and become a gaseous selenium molecule. It is believed that selenium in immobilized selenium, either in atomic form, in molecular form, or in any form, is capable of chemically interacting with selenium and carbon backbones beyond the intermolecular interactions of selenium. Also, the last portion of selenium exiting the carbon skeleton between 660° C. and 1000° C. has an average kinetic energy of 11,635 J/mole to at least 15,876 J/mole. This suggests that selenium in immobilized selenium is more stable than selenium in conventional selenium-carbon complexes. The stabilized selenium in the immobilized selenium of this Example 10 is found in the atomic, molecular or any form of selenium inside the carbon skeleton during electrochemical processes, such as during charge and discharge cycling of a rechargeable battery containing immobilized selenium. improve the ability to stay. In one example, this last portion of selenium may require a kinetic energy of more than 11,635 J/mole (above 660° C.) to exit the carbon skeleton, and may be important for selenium immobilization, and the carbon skeleton and most immobilized parts of the carbon skeleton. It can act as an interfacial material between selenium molecules. The portion of interfacial selenium in the immobilized selenium may be at least 1.5%, at least 2.0%, at least 2.5%, or 3.0% of the total immobilized selenium.

11A also shows a TGA study for immobilized selenium with a heating rate of 16°C/min, with a temperature of 628°C for mid-point-weight loss of contained selenium. As shown in Fig. 11c, in the case of the Se-Super P composite, the temperature at the mid-weight-loss of Se contained at a heating rate of 16°C/min is 495°C. At different heating rates (e.g., 16°C/min, 10°C/min, 5°C/min, 2.5°C/min, and 1°C/min), the activation energy and collision frequency are ASTM E1641-16 and E2958-14 It can be determined and calculated using known methods such as Temperatures at 15% weight loss for different heating rates are tabulated as shown in Table 3 below.

[Table 3]

It was determined that the activation energy for selenium (unimmobilized or conventional) in the Se-Super P complex was 92.3 kJ/mol and the collision frequency was 2.27×10 ⁵ . The activation energy for selenium in immobilized selenium (228-110 above) was also determined to be ^{120.7 kJ/mol and the collision frequency 12.4×10 5 .} Another sample of immobilized selenium (155-82-2 above) prepared by the same procedure as in Example 10 was also measured to have an activation energy of 120.0 kJ/mol and a collision frequency of ^{18.3×10 5 .}

The kinetic rate constant for selenium is calculated using the Arrhenius equation:

where k is the rate constant, E _a is the activation energy, A is the collision frequency, R is the gas constant, and T is the temperature in Kelvin.

Referring to the determined activation energy and impulse frequency and FIG. 11d , the kinetic rate constant was calculated using the Arrhenius equation at different temperatures. 11D shows that unimmobilized selenium (Se-Super P complex-solid line) is approximately four orders of magnitude higher than immobilized selenium (228-110 (dotted line) and 115-82-2 (dashed line)), for example at 35°C. (four orders of magnitude) and above and about three orders of magnitude higher at 100°C, indicating that it has a much higher rate constant. In one example, at 50 ℃, note the rate constant for the purification of selenium (Super P) is 2.668 × 10 ^-10, whereas the immobilized selenium is 7.26 × 10 ^-14 (155-82-2) and 3.78 × 10 ^-14 It has a rate constant of (228-110). Selenium with a lower kinetic rate constant is less likely to leave the host material (carbon), which may lead to better cell cycling performance.

12 shows the spectrum of immobilized selenium with Raman peaks of the D-band at ^{1368 cm -1 and the G-band at 1596 cm -1} with a ratio of area to D-band to area to G-band of 2.8. . Compared to the Raman spectrum of the carbon skeleton shown in Figure 9, selenium immobilization shifts both Raman peaks to higher wave numbers with ^{about 3 cm −1 red shift for the D-band and 7 cm −1} red shift for the G-band. This suggests that the bond strength of the ^{Sp 2} carbon in the carbon skeleton is enhanced with a red shift of ^{about 4 cm −1 for} the D-band and a red shift of about 8 cm ^{−1 for the G-band.} At the same time, the ratio of area to D-band to area to G-band also decreased from about 3.4 to 2.8, suggesting that the D-band is relatively weaker or the G-band is relatively stronger. A stronger G-band may be desirable, since the G-band may relate to the type of carbon that allows the carbon skeleton to conduct electrons more readily, and when used in rechargeable batteries, the electrochemical Because it can be desirable for performance. Bulk or pure selenium typically exhibits a sharp Raman shift peak at ^{about 235 cm −1 .} For immobilized selenium, the Raman spectrum in FIG. 12 shows a ^{broad Raman peak at about 257 cm −1} (~12.7% of the G-band in area) and a new broad hump at ^{about 500 cm −1 (G-} about 3.0% of the band area). Selenium immobilization is believed to change the Raman properties for both the carbon skeleton and selenium as all Raman peaks shift to higher wavenumbers, indicating that both the carbon-carbon Sp ² bond to the carbon skeleton and the selenium-selenium bond of selenium are suggests that it is under compression.

The compression resulting from selenium immobilization ^{strengthens both the carbon-carbon Sp 2} bond to the carbon backbone and the Se-Se bond to selenium, resulting in stronger selenium-selenium and carbon-selenium interactions. Therefore, greater kinetic energy will be required for selenium to overcome the stronger Se–Se bonding and stronger carbon–selenium interaction, which is the result of TGA analysis of immobilized selenium versus Se–Super P composites and Se–graphite composites. Describe your observations.

Also, under compression, the carbon backbone will then have better electron conductivity at the bonding level; Under compression, the selenium atom or molecule will also have better electron conduction ability.

Stabilized selenium to immobilized selenium with enhanced electronic conductivity across the carbon backbone and selenium, for example, has improved specific capacity for active materials with minimal shuttling levels, improved cycling capacity due to immobilization, higher rates It may be desirable in electrochemical processes such as the ability to be charged and discharged into a furnace. However, this should not be construed in a limiting sense.

The X-ray diffraction pattern for immobilized selenium prepared according to Example 10 shown in FIG. 13 shows a decrease in the intensity of broad diffraction peaks from the carbon skeleton with a d-spacing of about 5.21 angstroms - only about 1/3 intensity. , suggesting that immobilized selenium makes the carbon skeleton more disordered or causes greater destruction according to the order of the carbon skeleton. In one example, it is believed that this is because a ^{compressive force is applied to the carbon-carbon Sp 2 bond.}

14 shows an SEM image of immobilized selenium prepared according to Example 10 showing a sheet-like morphology, similar to the image of FIG. 7 for the carbon skeleton. Although about 50% of selenium is immobilized to the carbon skeleton, there are no observable selenium particles on the surface of the carbon skeleton except that the inter-sheet linkages are broken, which results in many flat sheets with high aspect ratios. Such sheet-like morphologies can be highly desirable for forming oriented coatings aligned along the flat-sheet direction, creating a sheet surface to surface contact, and resulting in improved sheet-to-sheet electrical conductivity, such as in rechargeable batteries. It can lead to good electrical performance for electrochemical processes.

Example 11: Se Cathode Fabrication

56 mg of immobilized selenium prepared according to Example 10 in a mortar and pestle; 7.04 mg of Super P; 182 μL of carboxymethyl cellulose (CMC) solution (each 52 μL of CMC solution contains 1 mg of dry CMC); 21.126 μL of SBR latex dispersion (each 6.036 μL SBR latex dispersion contains 1 mg dry SBR latex); and 200 μL of deionized water. A cathode slurry is produced by manually grinding the particles, binder, and water into a slurry for 30 minutes. The cathode slurry was then coated on one side of an electrically conductive substrate, eg, a piece of foil, and air dried. In one example, the conductive substrate or foil may be an aluminum (Al) foil. However, this should not be construed in a limiting sense as the use of any suitable and/or desirable electrically conductive material in any shape or form is also contemplated. For illustrative purposes only, the use of Al foil to form a selenium cathode will be described herein. However, this should not be construed in a limiting sense.

The slurry coated Al foil is then placed in a drying oven and heated to a temperature of 55° C. for 12 hours to produce a selenium cathode, which consists of a dried sheet of selenium immobilized on one side of the Al foil and the other side of the Al foil. Silver is uncoated, ie bare aluminum.

Selenium cathodes were then punched into cathode disks each having a diameter of 10 mm. Some of these cathode disks were used as cathodes for rechargeable batteries.

Example 12: Li-Se Rechargeable Cell Assembly and Testing

The cathode disk from Example 11 was used to assemble a Li-Se rechargeable coin cell cell in the manner described in the example discussed below and shown in FIG. 15 . In this example, the 10 mm diameter cathode disk 4 from Example 11 was used as the base 2 of a 2032 stainless steel coin cell can serving as the positive case of the coin cell (“positive case” in FIG. 15 ). ) and fixed selenium sheet 5 is facing upward away from the base 2 of the positive case, and the bare Al surface is in contact with the base 2 of the positive case. Next, a battery separator 6 (19 mm in diameter and 25 microns in thickness) was placed on top of the cathode disk 4 in contact with the immobilized selenium sheet 5 . In one example, the battery separator 6 may be an organic separator, or an inorganic separator, or a solid electrolyte separator. The organic separator may be a polymer, such as polyethylene, polypropylene, polyester, halogenated polymer, polyether, polyketone, and the like. The inorganic separator may be made of glass and/or quartz fibers.

_{Next, 240 μL of electrolyte (7) containing LiPF 6} (1 M) in ethylene carbonate (EC) and dimethyl carbonate (DMC) solvent (50-50 weight) was introduced into the positive case (2), and then lithium A foil disk 8 (15.6 mm in diameter and 250 microns in thickness) was placed on the side of the separator 6 opposite the cathode disk 4 . Next, a stainless steel (SS) spacer 10 is placed on the side of the lithium foil disk 8 facing the separator 6, and then on the side of the SS spacer 10 facing the lithium foil disk 8. , for example one or more foam disks 12 made of nickel. A lithium foil (8), SS spacer (10), and/or foam (12) disk may serve as the anode. Finally, the case 14 made from 2032 stainless steel 14, which serves as the negative of the coin cell (“negative case” in FIG. 15 ), is the side of the nickel foam disk 12 opposite the SS spacer 10 . and on the rim of the positive case (2). The positive case 2 and the negative case 14 were then sealed together under high pressure, for example at 1,000 psi. The sealing of the positive and negative cases 2, 14 under high pressure is also (from bottom to top in FIG. 15) cathode disk 4, separator 6, lithium foil 8, SS spacer 10, and Ni It had the effect of compressing together the stack comprising the foam disk(s) 12 . At least 12 coin cell batteries were assembled using the battery separators and fiberglass separators described above. Then, the assembled coin cell battery was tested under the following conditions.

Portions of the assembled coin cell cells were tested at 0.1C and 1C charge-discharge rates using a Lanhe cell tester CT2001A. Each coin cell cell was tested: (1) rest for 1 hour; (2) discharge to 1V; (3) rest for 10 minutes; (4) charging to 3V; (5) rest for 10 minutes; Repeat steps (2) to (5) for repeat cycling test.

16A (left) shows the cathode prepared according to Example 12 using the cathode prepared according to Example 11 showing excellent cycling stability with a specific capacity of 633.7 mAh/g after 313 cycles with 93.4% retention of the initial specific capacity. Cycling test results for a coil cell (313 cycles at a charge-discharge rate of 0.1C) are shown. The primary discharge specific capacity was higher than the stoichiometric value, presumably due to some side reactions on the cathode and anode surfaces. From cycle 2, specific capacity initially decreased with cycling; However, the specific capacity increased slightly from about 30 cycles to about 120 cycles, then remained stable until about 180 cycles and then decreased. 16B (right) also shows another coin cell having a specific capacity of 462.5 mAh/g at 600 cycles, with 66.0% retention of 2 cycle capacity at 0.1C or 80.3% retention of 105 cycle capacity at 1C. It shows excellent cycling stability (100 cycles at 0.1C followed by 500 cycles at 1C). Coulombic efficiencies can be greater than 95%, greater than 98%, or up to 100%, suggesting no detectable amount of selenium shuttling between the cathode and anode. This electrochemical performance is believed to be a result of selenium immobilized at the cathode, which prevents selenium from dissolving and shuttling from cathode 14 to anode 2 .

17 shows the cycling test results at different discharge-charge cycling rates (between 0.1C rate and 10C-rate) for coin cells assembled with the polymer separator described in Example 12. The test protocol was similar to the test described above, except for the cycling rates (0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C); 5 cycles of charging and discharging were performed for each C-rate; The cycling rate was returned to 0.1C cycle. At the 0.1C rate, the cell exhibited a specific capacity near the stoichiometric value. In addition, the cells exhibited excellent stability in cycling to cycling rates of 0.2C, 0.5C, 1C and 2C. The cell also exhibited fast charge and discharge capability and cycled 56% of its stoichiometric capacity at 10 C-rate, albeit with a specific capacity that decreases with cycling. In other words, at the 10C-rate the cell took 3.3 minutes to charge and discharge to/from 56% capacity of the stoichiometric value. Under such fast cycling rates, conventional cells are not expected to withstand.

A Li-Se battery containing immobilized selenium can recover its specific capacity to 670 mAh/g, 98% of its total capacity, when cycled at 0.1 C-rate at the start of the test. This is because (1) stabilization of selenium in the immobilized selenium cathode prevents selenium from leaving the carbon skeleton, which prevents selenium from shuttling between the cathode and anode during cycling, so that the cell has improved cycling performance. can; (2) Sp ² carbon-carbon bonds and carbon skeletons, selenium-selenium bonds, and carbon-selenium interactions can both be under compression, possibly within the carbon skeleton, in selenium particles, and between carbon and selenium interfaces. It results in better electrical conductivity, which is believed to help achieve the cycling performance observed at high C-rates.

An immobilized selenium body comprising selenium and carbon prepared according to the principles described herein may include one or more of the following characteristics:

(a) the kinetic energy required for selenium particles to escape immobilized selenium is at least 9.5 kJ/mole, at least 9.7 kJ/mole, at least 9.9 kJ/mole, at least 10.1 kJ/mole, at least 10.3 kJ/mole, or 10.5 kJ /mole or more;

(b) the temperature required for selenium particles to exit the immobilized selenium may be 490°C or higher, 500°C or higher, 510°C or higher, 520°C or higher, 530°C or higher, 540°C or higher, 550°C or higher, or 560°C or higher ;

(c) carbon has a surface area of at least 500 m ² /g, at least 600 m ² /g, at least 700 m ² /g, at least 800 m ² /g, at least 900 m ² /g, or at least 1,000 m ² /g (20 for pores less than angstroms);

(d) carbon has a surface area (for pores between 20 angstroms and 1000 angstroms) of 20% or less, 15% or less, 10% or less, 5% or less, 3% or less, 2% or less, 1% or less of the total surface area can have;

(e) the carbon and/or selenium may be under compression. Advantages of immobilized selenium with carbon and/or selenium under compression over carbon-selenium systems in which carbon and/or selenium are not under compression may include: improved electron flow, reduced resistance to electron flow , or both, it can facilitate electron transfer from selenium anions to selenium during charging and discharging of a rechargeable battery having a cathode made of immobilized selenium;

(f) Immobilized selenium may comprise selenium with a higher activation energy than that of conventional (unimmobilized) selenium for selenium to escape from the immobilized Se—C composite system. In one example, the activation energy for unimmobilized selenium (Se-Super P composite system) was determined to be 92 kJ/mole according to ASTM method E1641-16. In contrast, in one example, the activation energy for selenium in immobilized selenium comprising selenium and carbon is at least 95 kJ/mole, at least 98 kJ/mole, at least 101 kJ/mole, at least 104 kJ/mole, at least 107 kJ/mole. or more, or 110 kJ/mol or more. In another example, the activation energy for selenium in immobilized selenium comprising selenium and carbon is 3% or more, 6% or more, 9% or more, 12% or more, 15 or more than the activation energy for selenium in the Se-Super P complex. % or more or 18% or more;

(g) Immobilized selenium may comprise selenium having a higher collision frequency than unimmobilized selenium. In one example, the collision frequency for unimmobilized selenium was determined to be ^{2.27×10 5 according to ATSM method E1641-16.} In contrast, in one example, the collision frequency for selenium in immobilized selenium comprising selenium and carbon is at least 2.5×10 ^{5 , at} least 3.0×10 ^{5 , at} least 3.5×10 ^{5 , at} least 4.0×10 ^{5 , and at} least 4.5×10 ⁵ or more, 5.0×10 ⁵ or more, 5.5×10 ⁵ or more, 6.0×10 ⁵ or more, or 8.0×10 ⁵ or more. The immobilized selenium is 10% or more, 30% or more, 50% or more, 80% or more, 100% or more, 130% or more, 150% or more, 180% or more, or It can have a collision frequency of 200% or more; and

(h) immobilized selenium is 1/5 or less, 1/10 or less, 1/50 or less, 1/100 or less, 1/500 or less, or 1/1000 or less of the kinetic rate constant for unimmobilized/conventional selenium; It may contain selenium with a kinetic rate constant. In one example, immobilized selenium has a kinetic rate constant (at 50°C) ^{of 1×10 -10} or less, 5×10 ^-11 or less, 1×10 ^-11 or less, 5×10 ^-12 or less, or 5×10 ^{-13 or less.} ) may contain selenium having.

With carbon and/or selenium of immobilized selenium under compression, the D-band and/or G-band of the Raman spectrum for ^{the Sp 2} CC bond of the carbon of immobilized selenium (or the carbon skeleton as defined by said carbon) is From the carbon feedstock, for example, it may exhibit a red (positive) shift of at ^{least 1 cm −1 , at} least 2 cm ^{−1 , at} least 3 cm ^{−1 , at} least 4 cm ⁻¹ , or at ^{least 5 cm −1 .}

As carbon and/or selenium of immobilized selenium under compression, selenium is ^{derived from the Raman peak of pure selenium (235 cm −1} ), for example 4 cm ⁻¹ or more, 6 cm ⁻¹ or more, 8 cm ⁻¹ or more , 10 cm ⁻¹ or more, 12 cm ⁻¹ or more, 14 cm ⁻¹ or more, or 16 cm ⁻¹ or more red (positive) shift, such a red shift may suggest compression for selenium particles.

The immobilized selenium may be selenium in elemental form and/or selenium in compound form.

Immobilized selenium, including selenium and carbon, can also be defined as one or more additional element(s) from group 6 of the periodic table including, for example, without limitation, sulfur and/or tellurium (hereinafter "additional group 6 element") (s)") may be doped. Dopant levels can range from a minimum of 100 ppm by weight to a maximum of 85% of the immobilized selenium. In one example, the immobilized selenium may comprise 15% - 70% carbon and 30% - 85% selenium and optionally additional group 6 element(s). In one example, the immobilized selenium may comprise a mixture of (1) 15% - 70% carbon and (2) 30% - 85% selenium plus additional group 6 element(s). In a mixture comprising selenium ± additional group 6 element(s), the additional group 6 element(s) may comprise between 0.1% and 99% of the mixture and selenium may comprise between 1% and 99.9% of the mixture have. However, this range of selenium plus additional group 6 element(s) should not be construed in a limiting sense.

The immobilized selenium may comprise at least 5% selenium, at least 10% selenium, at least 20% selenium, at least 30%, at least 40% selenium, at least 50% selenium, at least 60% selenium, or at least 70% selenium.

The immobilized selenium may optionally include another element, such as sulfur, tellurium, and the like.

The immobilized selenium may be Raman-inactive or Raman-active. If Raman-active, immobilized selenium can have a Raman relative peak intensity at ^{255 ± 25 cm -1} , at 255 ± 15 cm ^-1 , or at 255 ± 10 cm ^{-1 .}

The immobilized selenium may comprise selenium having a Raman relative peak intensity of at least 0.1%, at least 0.5%, at least 1%, at least 3%, or at least 5%, wherein the Raman relative peak intensity is the D- of the carbon Raman spectrum. It is defined as the area of the Raman peak at ^{255 cm −1 relative} to the area of the band peak.

Carbon comprising immobilized selenium may serve as a carbon backbone for selenium immobilization. The carbon skeleton includes a Raman D-band located at 1365 ± 100 cm ^-1 and a G-band located at ^{1589 ± 100 cm -1 ;} D-band located at 1365 ± 70 cm ^-1 and G-band located at ^{1589 ± 70 cm -1 ;} D-band located at 1365 ± 50 cm ^-1 and G-band located at ^{1589 ± 50 cm -1 ;} D-band located at 1365 ± 30 cm ^-1 and G-band located at ^{1589 ± 30 cm -1 ; or an Sp 2} -carbon-carbon bond with a D-band located at 1365 ± 20 cm ^-1 and a G-band located at ^{1589 ± 20 cm -1 .}

^{The carbon of immobilized selenium may contain an Sp 2} carbon-carbon bond with a Raman peak characterized by a D-band and a G-band. The ratio of the area of the D-band to the G-band may be 0.01 to 100, 0.1 to 50, or 0.2 to 20.

^{The carbon of immobilized selenium may contain an Sp 2} carbon-carbon bond with a Raman peak characterized by a D-band and a G-band. Each D-band and G-band may be shifted to a higher wavenumber ^{of 1 cm −1} or more, 2 cm ^{−1 or more, or more.}

The carbon of immobilized selenium can be doped with one or more other elements in the periodic table.

The carbon of immobilized selenium may be porous. The pore size distribution of the carbon backbone can range between 1 angstrom and a few microns. The pore size distribution may have at least one peak located between 1 angstroms and 1000 angstroms, between 1 angstroms and 100 angstroms, between 1 angstroms and 50 angstroms, between 1 angstroms and 30 angstroms, or between 1 angstroms and 20 angstroms. The porosity of the carbon backbone may have a pore size distribution with one or more peaks in the aforementioned ranges.

The carbon of immobilized selenium is between 0.01 mL/g and 5 mL/g; between 0.01 mL/g and 3 mL/g; between 0.03 mL/g and 2.5 mL/g; or between 0.05 mL/g and 2.0 mL/g.

The carbon of immobilized selenium may be greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 70%, or greater than 80% of the total measurable pore volume (less than 100 angstroms, less than 50 angstroms, 30 angstroms). less than, or having a pore size of less than 20 angstroms).

The carbon of immobilized selenium is greater than 400 m ² /g, greater than 500 m ² /g, greater than 600 m ² /g, greater than 700 m ² /g, greater than 800 m ² /g, greater than 900 m ² /g, or 1000 surface area greater than m ^{2 /g.}

The carbon of immobilized selenium may be amorphous and may have a broad peak centered on a d-spacing of about 5.2 angstroms.

The carbon of immobilized selenium can be of any morphology, platelet, sphere, fiber, needle, tubular, irregular, interconnected, agglomerated, discrete, or any solid particle. Platelet, fiber, needle, tubular, or some morphologies with a certain level of aspect ratio may be advantageous in achieving better interparticle contact, resulting in enhanced electrical conductivity (beyond immobilized selenium prepared from different aspect ratios); , this may be advantageous for electrochemical cells, such as rechargeable cells.

The carbon of immobilized selenium can be of any particle size, with a median particle size between 1-9 nanometers and 2 millimeters, between 1-9 nanometers and less than 1000 microns, or between 20 nanometers and 100 microns.

The selenium of immobilized selenium may be amorphous, for example, as determined by X-ray diffraction. The diffraction peak of immobilized selenium, which may have a d-spacing of about 5.2 angstroms, may be attenuated than the diffraction peak of the carbon skeleton, e.g., 10% attenuation, 20% attenuation, 30% attenuation, or 40% more attenuation. can be

In one example, a method for preparing immobilized selenium may include:

(a) physically mixing carbon and selenium. Physical mixing can be accomplished by ball-milling (dry and wet), mixing with mortar and pestle (dry or wet), jet-milling, horizontal milling, friction milling, high shear mixing in the slurry, regular mixing of the slurry using a blade, etc. there is;

(b) The physically mixed carbon and selenium of step (a) may be heated above the melting temperature of the selenium. The heating of the carbon and selenium mixture may occur in the presence of an inert gas environment, such as, but not limited to, argon, helium, nitrogen, etc., or in air or a reactive environment;

(c) optionally homogenizing or blending the heated carbon and selenium to achieve selenium immobilization; and

(d) cooling the immobilized selenium of step (c) to ambient or room temperature.

In another example, immobilized selenium can be prepared by dissolving selenium on carbon and then vaporizing it. The solvent for dissolving selenium may be an alcohol, ether, ester, ketone, hydrocarbon, halogenated hydrocarbon, nitrogen-containing compound, phosphorus-containing compound, sulfur-containing compound, water or the like.

In another example, immobilized selenium can be prepared by melting selenium onto carbon and then removing excess or excess unimmobilized selenium.

In one example, a method for preparing immobilized selenium may include:

(a) mixing selenium and carbon together under dry or wet conditions;

(b) optionally drying the mixture of step (a) at an elevated temperature;

(c) optionally pelletizing the dried mixture of step (b);

(d) fusing selenium into carbon to prepare immobilized selenium.

Immobilized selenium can be used as a cathode material for rechargeable batteries. The cathode may comprise an inorganic or organic binder. The inorganic binder may be, for example, a natural product, such as CMC, or a synthetic product, such as, for example, SBR rubber latex. The cathode may include any electrically-conductive promoter, such as, for example, graphite-derived small particles, graphene, carbon nano-tubes, carbon nano-sheets, carbon black, and the like. Finally, the cathode may comprise a charge current collector such as, for example, aluminum foil, copper foil, carbon foil, carbon fabric or other metal foil.

A method for preparing a cathode comprises coating an immobilized selenium-containing slurry on a charge collector, followed by drying the slurry-coated charge collector (eg, air drying, oven-drying, vacuum oven-drying, etc.) may include. The immobilized selenium may be dispersed in the slurry, which may be prepared by a high shear mixer, a normal mixer, a planetary mixer, a double-planetary mixer, a ball mill, a vertical attritor, a horizontal mill, and the like. The slurry can then be coated onto a charge current collector and then dried in air or vacuum. The coated cathode may be pressed or roller-milled (or calendered) prior to use in the rechargeable battery.

Rechargeable cells can be made using the immobilized selenium described herein. The rechargeable battery may include a cathode comprising immobilized selenium, an anode, and a separator separating the anode and the cathode. The anode, cathode, and separator may be immersed in an electrolyte such as _{, for example, LiPF 6 .} The anode may be composed of lithium, sodium, silicon, graphite, magnesium, tin, or the like.

The separator may be composed of an organic separator, an inorganic separator, or a solid electrolyte separator. The organic separator may include, for example, a polymer such as polyethylene, polypropylene, polyester, halogenated polymers, polyethers, polyketones, and the like. The inorganic separator may include glass or quartz fibers, or a solid electrolyte separator.

The electrolyte may comprise a lithium salt, a sodium salt, or other salts from Groups IA, IIA, and IIIA in an organic solvent. Organic solvents may include organic carbonate compounds, ethers, alcohols, esters, hydrocarbons, halogenated hydrocarbons, lithium-containing-solvents, and the like.

Rechargeable batteries may be used in electronics, electric or hybrid vehicles, industrial applications, military applications such as drones, aerospace applications, marine applications, and the like.

The rechargeable battery has at least 400 mAh/g for the active amount of selenium, at least 450 mAh/g for the active amount of selenium, at least 500 mAh/g for the active amount of selenium, and at least 550 mAh/g for the active amount of selenium. or more, or an electrochemical capacity of 600 mAh/g or more with respect to the active amount of selenium.

The rechargeable battery may undergo electrochemical cycling for at least 50 cycles, at least 75 cycles, at least 100 cycles, at least 200 cycles, and the like.

The rechargeable battery can be charged and/or discharged at 0.1C, 0.2C, 0.5C, 1C, 1.5C, 2C, 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C or faster.

Rechargeable cells have high C-rate charge-discharge cycling (5 cycles at 0.1C, 5 cycles at 0.2C, 5 cycles at 0.5C, 5 cycles at 1C, 5 cycles at 2C, 5 cycles at 5C, and 5 cycles at 10C). cycle), it is possible to maintain a cell specific capacity greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 70% or greater than 80% of the second discharge specific capacity at a cycling rate of 0.1C. .

The rechargeable battery may have a coulombic efficiency of 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, or up to about 100% coulombic efficiency.

The coulombic efficiency of a cell is defined as:

where ηc is the coulombic efficiency (%),

Qout is the amount of charge that leaves the cell during the discharge cycle,

Qin is the amount of charge entering the cell during the charge cycle.

Rechargeable cells can be charged at 0.1C, 0.2C, 0.5C, 1C, 1.5C, 2C, 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C or at a faster C-rate. C-rate is a measure of the rate at which a cell discharges in relation to its maximum capacity. For example, a 1C rate means that the discharge current will discharge the entire cell in 1 hour. For example, for a cell with a capacity of 100 Amp-hr, this equals a discharge current of 100 Amp. A 5C rate for this same cell would be 500 Amp and a 0.5C rate would be 50 Amp.

The cathode of the rechargeable battery may include an element of a chalcogen group, such as at least one of selenium, sulfur, tellurium, and oxygen.

The anode of the rechargeable battery may include at least one element of an alkali metal, an alkaline earth metal, and a Group IIIA metal.

The separator of the rechargeable battery may include an organic separator or an inorganic separator.

The electrolyte of the rechargeable battery may include at least one element of an alkali metal, an alkaline earth metal, and a Group IIIA metal; The solvent of the electrolyte may include an organic solvent, carbonate-based, ether-based or ester-based.

The rechargeable battery may have a specific capacity of at least 400 mAh/g, at least 450 mAh/g, at least 500 mAh/g, at least 550 mAh/g, or at least ≧600 mAh/g.

The rechargeable battery may undergo electrochemical cycling for at least 50 cycles, at least 75 cycles, at least 100 cycles, at least 200 cycles, and the like.

Rechargeable cells have high C-rate charge-discharge cycling (5 cycles at 0.1C, 5 cycles at 0.2C, 5 cycles at 0.5C, 5 cycles at 1C, 5 cycles at 2C, 5 cycles at 5C, and 5 cycles at 10C). cycle), it may have a specific capacity of greater than 30%, greater than 40%, greater than 50%, greater than 60%, greater than 70%, or greater than 80% of the second discharge specific capacity at a cycling rate of 0.1C.

The rechargeable battery may have a coulombic efficiency of at least 50%, at least 60%, at least 70%, at least 80%, or at least 90%.

Also disclosed is a composite comprising selenium and carbon, wherein the composite may have a plate-like morphology having an aspect ratio of 1 or more, 2 or more, 5 or more, 10 or more, or 20 or more.

The selenium of the complex may be amorphous as determined by, for example, X-ray diffraction. The diffraction peak of selenium, which may have a d-spacing of about 5.2 angstroms, may be attenuated by, for example, 10% attenuation, 20% attenuation, 30% attenuation, or 40% attenuation, than the diffraction peak for the carbon backbone. have.

In one example, a method for preparing the composite may include:

(a) Physical mixing of carbon and selenium. Physical mixing can be by ball-milling (dry and wet), mixing with mortar and pestle (dry or wet), jet-milling, horizontal milling, friction milling, high shear mixing in the slurry, regular mixing of the slurry with a blade, etc. there is;

(b) the physically mixed carbon and selenium of step (a) may be heated above the melting temperature of the selenium, wherein the heating is performed, for example, in the presence of an inert gas environment such as argon, helium, nitrogen, etc., or air or in a reactive environment;

(c) homogenizing or blending the heated carbon and selenium of step (b) to achieve selenium immobilization.

In another example, the composite can be prepared by dissolving selenium on carbon and then vaporizing it. Solvents for dissolving selenium may include alcohols, ethers, esters, ketones, hydrocarbons, halogenated hydrocarbons, nitrogen-containing compounds, phosphorus-containing compounds, sulfur-containing compounds, water, and the like.

Composites can be prepared by melting selenium onto (or in) carbon and then removing excess or excess unimmobilized selenium.

In one example, a method for preparing the composite may include:

(a) mixing selenium and carbon together under dry or wet conditions;

(b) optionally drying the mixture of step (a) at an elevated temperature;

(c) optionally pelletizing the dried mixture of step (b);

(d) melting selenium in carbon to produce immobilized selenium.

The composite can be used as a cathode material for the cathode of a rechargeable battery. The cathode may comprise an inorganic or organic binder. The inorganic binder may be, for example, a natural product, such as CMC, or a synthetic product, such as, for example, SBR rubber latex. The cathode may include any electrically-conductive promoter, such as, for example, graphite-derived small particles, graphene, carbon nano-tubes, carbon nano-sheets, carbon black, and the like. Finally, the cathode may comprise a charge current collector such as, for example, aluminum foil, copper foil, carbon foil, carbon fabric or other metal foil.

A method for preparing a cathode comprises coating an immobilized selenium-containing slurry on a charge collector, followed by drying the slurry-coated charge collector (eg, air drying, oven-drying, vacuum oven-drying, etc.) may include. The immobilized selenium may be dispersed in the slurry, which may be prepared by a high shear mixer, a normal mixer, a planetary mixer, a double-planetary mixer, a ball mill, a vertical attritor, a horizontal mill, and the like. The slurry can then be coated onto a charge current collector and dried in air or in vacuum. The coated cathode may then be compacted or roller-milled (or calendered) prior to use in a rechargeable battery.

Rechargeable batteries are made using the composites described above. The rechargeable battery can be charged at 0.1C, 0.2C, 0.5C, 1C, 1.5C, 2C, 3C, 4C, 5C, 6C, 7C, 8C, 9C, 10C or faster.

Example 13: Preparation of Immobilized Selenium Doped with Sulfur, Electrodes, and Cells Thereof.

5 atomic percent (at %) selenium, 20 at % selenium, 35 at % selenium, and 50 at% of selenium was separately replaced with sulfur. A sample of sulfur-doped immobilized selenium was synthesized with a carbon skeleton prepared according to the principles and procedures described in Example 9.

[Table 4]

Then, using a sample of immobilized sulfur-doped selenium thus prepared, a plurality of cathodes 4 comprising immobilized sulfur-doped selenium were prepared according to the principles and procedures described in Example 11 for immobilized selenium. prepared.

Then, the cathode comprising immobilized sulfur-doped selenium thus prepared in this Example was used to prepare a coin cell battery according to the principles and procedures described in Example 12.

The coin cell battery assembled in this Example was then tested in the cell tester described in Example 12 according to the same test protocol also described in Example 12 at 0.1C and 1C charge and discharge cycling rates.

The electrochemical cycling results at 0.1 C for a coil cell cell comprising a cathode composed of an immobilized sulfur-doped selenium cathode prepared with an immobilized sulfur-doped selenium sample (Se50S50 in Table 4) are shown in FIG. 18, 2 The 2 ^nd cycle discharge capacity is 821 mAh/g (which is considered good) and has a sustained coulombic efficiency of 95% or more, typically 98% or more (which is also considered good), or up to 100%.

Assuming that selenium has a stoichiometric specific capacity of 675 mAh/g at a 0.1C cycling rate, the specific sulfur capacity would be estimated to be about 1,178 mAh/g (which is considered good for sulfur). Coulombic efficiencies greater than 95%, greater than 98%, or up to 100% indicate that significant amounts of sulfur do not shuttle between the cathode and anode. In immobilized sulfur-doped selenium cells, the sulfur species function well in electrolytes containing carbonates. Typically, sulfur is not expected to function well in Li-S cells with carbonate as electrolyte; Conventional Li-S cells typically use an ether-based electrolyte. Carbonate-based electrolytes are typically used in the present lithium-ion cells. Carbonate-based electrolytes are more economical and much more widely available on the market than ether-based electrolytes.

The electrochemical cycling results at 1 C cycling rate for a coil cell cell comprising a cathode composed of an immobilized sulfur-doped selenium cathode prepared with an immobilized sulfur-doped selenium sample (Se50S50 in Table 4) are shown in FIG. 19 . , the two cycle discharge capacity is 724 mAh/g and has a sustained coulombic efficiency of at least 95%, typically at least 98%, or up to 100%.

Assuming that selenium has a specific capacity of 625 mAh/g at 1C cycling rate, the sulfur specific capacity would be estimated to be about 966 mAh/g (which is also unexpected). Sulfur is an insulator and has very low electrical conductivity. Typically, Li-S cells cannot cycle well at fast cycling rates such as the 1C rate.

As can be seen, when used as a cathode material in rechargeable batteries, immobilized sulfur-doped selenium overcomes two fundamental problems associated with Li-S cells: shuttling effects and low cycling rates. When these two problems are solved, a cell comprising a cathode composed of immobilized sulfur-doped selenium can have high energy density and high power density for practical applications.

As can be seen, in one example, an immobilized sulfur-doped selenium system or body can be formed by a method comprising the steps of: (a) mixing selenium, carbon, and sulfur to selenium-carbon-sulfur forming a mixture; (b) heating the mixture of step (a) to a temperature above the melting temperature of selenium; and (c) allowing the heated mixture of step (b) to cool to ambient temperature or room temperature to form an immobilized sulfur-doped selenium body.

The immobilized sulfur-doped selenium body of step (c) may comprise selenium and sulfur in the carbon skeleton body.

Step (a) may occur under dry or wet conditions.

Step (b) may comprise homogenizing or blending the mixture.

Step (a) may include forming a selenium-carbon-sulfur mixture in the body. Step (b) may include heating the body to a temperature above the melting temperature of selenium. Step (c) may comprise allowing or allowing the body to cool to ambient temperature or room temperature.

Step (b) may comprise heating the mixture for a time sufficient for the selenium and carbon and sulfur to fully or partially react.

In another example, a method of making an immobilized sulfur-doped selenium system or body comprises: (a) forming a carbon backbone; and (b) melting selenium and sulfur into the carbon skeleton.

In another example, a method of forming an immobilized sulfur-doped selenium system or body comprises (a) mixing selenium and carbon and sulfur; and (b) after step (a), allowing selenium and sulfur to dissolve on the carbon to form an immobilized sulfur-doped selenium system or body.

Solvents for dissolving selenium and sulfur may be alcohols, ethers, esters, ketones, hydrocarbons, halogenated hydrocarbons, nitrogen-containing compounds, phosphorus-containing compounds, sulfur-containing compounds, or water. The solvent may be added to one or more of selenium, sulfur, or carbon before step (a), during step (a) or during step (b).

The method may further comprise (c) removing excess unimmobilized selenium, unimmobilized sulfur, or both from the immobilized sulfur-doped selenium system or body.

Also disclosed is a rechargeable battery comprising: a cathode composed of immobilized sulfur-doped selenium disposed on an electrically conductive substrate; a separator disposed in direct contact with the electrically conductive substrate and in contact with immobilized sulfur-doped selenium; and an anode spaced from the cathode by a separator.

The rechargeable battery may further comprise an anode spaced apart from the separator by lithium. In one example, the lithium may be in the form of a lithium foil.

The rechargeable battery may further include a cathode, a separator, an anode, and lithium immersed in an electrolyte.

In rechargeable batteries, immobilized sulfur-doped selenium may comprise a selenium-carbon-sulfur mixture, wherein selenium and sulfur are melted into carbon.

In rechargeable batteries, the separator may be formed from an organic material, an inorganic material, or a solid electrolyte.

The rechargeable battery may have a coulombic efficiency of 95% or greater.

Having thus described a method for preparing a selenium carbon composite material, for example, a method for preparing immobilized selenium in a rechargeable battery and immobilized selenium, immobilized selenium on porous carbon in the presence of a desirable level of oxygen species. The method of making and the use of immobilized selenium in rechargeable batteries will be described.

Note that selenium is one of the chalcogens including sulfur, selenium, tellurium, and the like. The description relating to selenium in the present disclosure is equally applicable to the remaining chalcogen elements, such as sulfur and tellurium.

In the present invention, selenium atoms or molecules are fixed in their oxidized form (in a rechargeable battery as charged state) or in their reduced form as selenide (in a discharged state in a rechargeable battery) as an element, and the selenium atom is localized inside the pores of the porous carbon, allowing the electrochemical reaction of the rechargeable battery to cycle properly during the discharging process and during the charging process. During the discharge process, the elemental selenium atom (neutral, Se) at the cathode is reduced and gains two atoms to become the selenide anion (Se ^{2 −} ), which is typically present as a salt, lithium selenide, Li ₂ Se, still It is ubiquitous at the cathode. The chemical energy of the discharge process is effectively converted into electrical energy in the rechargeable battery with minimal level of conversion into heat due to the presence of the intrinsic internal electrical resistance of the battery. During the charging process of the rechargeable battery, electrical energy is also _{effectively converted into chemical energy as selenide anions in the form of Li 2} Se at the cathode are oxidized and lose two electrons to form elemental selenium atoms still localized at the cathode. If selenium is not immobilized on the porous carbon, intermediate selenium species (typically in the form of polyselenide, as Se _n ² -) can form at the cathode during the electrochemical reduction/oxidation (ReDox) process and dissolve in the liquid electrolyte of the cell system have. The dissolved intermediate polyselenide species is then transported from the cathode to the liquid electrolyte through the battery separator at the anode, where it discovers metallic lithium, reacts with metallic lithium atoms and forms a salt of lithium and selenium on the surface of the lithium anode. Chemical energy generated from the reaction of lithium and intermediate selenium species at the anode is converted into heat instead of electrical energy, which is highly undesirable. Also, the selenium salt formed at the anode can then be even partially converted back to polyselenide anion, which is then dissolved in the electrolyte of the cell and transported back to the cathode, which acquires electrons, consuming additional electrical energy, and elemental selenium is returned back to Converting the electrochemical energy of selenium into heat or consuming additional electrical energy is undesirable even though the rechargeable battery can be cycled due to the undesirably low cycling efficiency. Note that cells with undesirably low cycling efficiencies often do not perform well for the desired number of cycles.

Thus, the present invention embodies that immobilization of selenium in a porous carbon skeleton is desirable to achieve adequate cycling of a rechargeable battery comprising a lithium anode, a selenium cathode, a separator, and an electrolyte. Selenium is anchored to the porous carbon and can be, for example, at least 95 kJ/mole, at least 98 kJ/mole, at least 101 kJ/mole, at least 104 kJ/mole, at least 107 kJ/mole, or at least 110 kJ/mole. It has activation energy. In immobilized selenium containing selenium and porous carbon, selenium and carbon interactions are often more frequent, for example, 2.5×10 ⁵ or more, 3.0×10 ⁵ or more, 3.5×10 ⁵ or more, 4.0×10 ⁵ or more. , 4.5 × 10 ⁵ or greater, 5.0 × 10 ⁵ or greater, 5.5 × 10 ⁵ or greater, 6.0 × 10 ⁵ or greater, or 8.0 × 10 ⁵ or greater collision frequency. The kinetic rate constant (at 50° C.) for immobilized selenium containing selenium and porous carbon is, for example, 1 x 10 ^-10 or less, 5 x 10 ^-11 or less, 1 x 10 ^-11 or less, 5 x 10 ^-12 or less, or 5 x 10 ^-13 or less. The carbon skeleton plays an important role in the proper immobilization of selenium. To achieve immobilization of selenium with desired levels of activation energy, collision frequency, and kinetic rate constant, carbon with a certain amount of microporosity (pore size of 20 angstroms or less) is used to spatially confine selenium inside the micropores of the carbon skeleton. it is preferable The presence of a certain amount of mesoporosity (pore sizes between 20 and 500 angstroms) and/or macroporosity (pore sizes greater than 500 angstroms) in the carbon skeleton is also not critical for immobilization of selenium, but lithium into the cathode during the cell discharge process. It is desirable for successfully transporting ions and exiting the cathode during the cell charging process. The amount of microporosity, mesoporosity, or macroporosity is typically characterized by the amount of pore volume (mL) per weight unit (g) of the carbon backbone. High levels of porosity, including microporosity, mesoporosity, and macroporosity, may be required to spatially confine high levels of selenium in porous carbons. The more selenium loaded into the porous carbon backbone (per gram), the more chemical and electrical energy can be interconverted during the cycling of the rechargeable battery.

The amount of microporosity to porous carbon for selenium immobilization may be 0.3 mL/g or more, 0.4 mL/g or more, or 0.5 mL/g or more. The total porosity, including microporosity, mesoporosity, and macroporosity, is at least 0.4 mL/g, at least 0.5 mL/g, and at least >0.6 mL/g. The proportion of microporosity of the total porosity, including microporosity, mesoporosity, and macroporosity, is between 50% and 99%, between 55% and 97%, and between 60% and 95%.

While a short route is preferred for lithium transport between the bulk of the electrolyte and the position where selenium is immobilized in the micropores, the presence of mesoporosity and macroporosity allows lithium ions to successfully transport in and out to access the selenium immobilized in the micropores. This can be important to ensure that the electrochemical process works properly during the discharging and charging process of the rechargeable battery. One of the particle dimensions of the porous carbon may be preferably as small as 5 μm or less, 2 μm or less, 1 μm or less, 0.5 μm or less, or 0.2 μm or less; The carbon particles may be relatively large in size with interconnected thin walls, or they may be small relative to the particle as a whole. The dimensions of the porous carbon can be characterized by scanning electron microscopy, transmission electron microscopy, optical microscopy, laser-scattering particle size analyzer, and the like.

Selenium is immobilized in the space of micropores of porous carbon particles having porosity including microporosity, mesoporosity, and macroporosity. Selenium is immobilized inside the pores of porous carbon by the strong interaction between selenium and the carbon skeleton. A porous carbon with a large surface area may have more active sites for selenium to interact with the carbon backbone. The porous carbon preferably has a BET surface area of at least ^{600 m 2} /g, at least 800 m ² /g, at least 1,000 m ² /g, at least 1,200 m ² /g, or at least 1,400 m ^{2 /g.}

Selenium is effectively anchored to the porous carbon through chemical interactions between the selenium species and the surface of the carbon skeleton. Oxygen-related functional groups in porous carbon can be a key species claiming strong chemical interactions with selenium. Such strong chemical interactions may result in effective immobilization of selenium resulting in an increase in activation energy, a decrease in the kinetic rate constant, and/or an increase in collision frequency. To achieve the desired level of chemical interaction between the backbone carbon atom and the selenium atom or molecule, an oxygen functional group or oxygen-related species as the interface between the carbon and selenium in the porous carbon is used. The amount of selenium needs to be high enough for the immobilization of selenium to be effective in a rechargeable battery that can function properly during electrochemical discharge and charge cycling processes. The amount of oxygen-related species, or oxygen functional groups, can be characterized as the amount of oxygen content of the porous carbon analyzed by an oxygen analyzer (such as a LECO oxygen analyzer). The oxygen content of the porous carbon can also be measured with gas detectors, such as, but not limited to, mass-specification detectors, thermal conductivity detectors, etc. with the option of a comprehensive cold trap mechanism in other instruments that function similar to LECO instruments, e.g. For example, it can be characterized by temperature-programmed desorption (or thermogravimetric analysis, or TGA).

It is preferred that the porous carbon for selenium immobilization has an oxygen content of at least 2%, at least 3%, at least 5%, or more preferably at least 7%.

Oxygen species in porous carbon can be classified by temperature-programmed desorption (TPD), and can typically be classified and characterized into _{oxygen species that form CO 2} , oxygen species that form CO, and oxygen species that form water. have. In a flow of an inert gas such as helium, nitrogen, or argon as carrier gas, a sample of porous carbon is temperature-programmed to a temperature that can be up to 1,000° C. at a defined heating rate. Oxygen species in the porous carbon sample are destroyed at different temperatures to form CO ₂ , CO, and/or water and are eluted by the carrier gas. For porous carbons compatible with selenium immobilization, _{the ratio of the amount of oxygen associated with CO 2} formation to the amount of oxygen associated with CO formation may be between 0.05 and 0.95, between 0.15 and 0.85, or between 0.2 and 0.8; The _{amount of oxygen associated with CO 2} formation may be at least 2%, at least 3%, at least 5%, or more preferably at least 7%; The amount of oxygen associated with CO formation may be at least 2%, at least 3%, at least 5%, or more preferably at least 7%; The amount of oxygen associated with water formation may be at least 2%, at least 3%, at least 5%, or more preferably at least 7%.

In another aspect, the density of oxygen species in the backbone carbon (micromoles per square meter, or μmole/m ² ) can be important to achieve a sufficient level of chemical interaction between the carbon surface and selenium atoms, which can be used in rechargeable batteries results in satisfactory selenium immobilization for proper cycling of The porous carbon for selenium immobilization has an oxygen content of 0.8 μmole/m ² or more, 1.0 μmole/m ² or more, 1.2 μmole/m ² or more, 1.4 μmole/m ² or more, or more preferably 1.6 μmole/m ² or more. prefer to have; The _{amount of oxygen associated with CO 2} formation is at least 0.8 μmole/m ^{2 , at} least 1.0 μmole/m ^{2 , at} least 1.2 μmole/m ^{2 , at} least 1.4 μmole/m ² , or more preferably at least ^{1.6 μmole/m 2 ;} The amount of oxygen associated with CO formation is at least 0.8 μmole/m ^{2 , at} least 1.0 μmole/m ^{2 , at} least 1.2 μmole/m ^{2 , at} least 1.4 μmole/m ² , or more preferably at least ^{1.6 μmole/m 2 .}

The presence of a sufficient amount of oxygen species in the backbone carbon appears to play an important role in the oxidative stability of the Se-C complex. Under ambient conditions, Se-C composites made of carbon skeletons with a small amount of oxygen species appear to be easily oxidized under ambient conditions; The novel material of such Se-C composites exhibits a temperature-gravimetric behavior similar to that of Se-C composites with a carbon skeleton with a sufficient amount of oxygen species; However, the Se-C composites made of a small amount of oxygen species aged for about 2 years and 3 months under ambient conditions show major exothermal weight loss at a temperature of about 200 to 250° C., where the Se-C composites It was surprising to find that the total weight loss of , when freshly prepared, exceeded the amount of selenium loaded on the carbon; In another example, the amount of weight loss under these temperatures appears to be sufficiently related to the amount of carbon backbone in the Se—C composite: the higher the amount of carbon backbone, the greater the exothermic weight loss at temperatures between 200°C and 250°C. do; In another example, the oxygen species content of an aged (27 months) Se—C composite made of a carbon skeleton with a low amount of oxygen species increases by up to about 24%; In another example, it is also interesting that the density of aged Se-C composites made from a carbon skeleton with a small amount of oxygen species is substantially reduced. Without limiting the scope or spirit of the present invention, the exothermic weight loss is caused by oxidation of the carbon-selenium complex by ambient oxygen species (environmental oxygen and/or moisture under ambient conditions) and/or ambient-oxygen- of carbon by elemental selenium. may involve ambient-oxygen-species-aided oxidation, both of which result in the formation of oxidized carbon species; Oxidation of the Se-C complex can occur near the pore mouth of the complex; Newly formed oxidized carbon species near the pore inlet can form closed porosity; The closed porosity is then inaccessible by probing molecules of helium gas during densitometry, which results in a density decrease for the aged Se-C composite sample made of the carbon skeleton with a small amount of oxygen species. The decomposition products of carbon species oxidized at a temperature between 200° C. and 250° C. under an inert carrier gas such as argon or nitrogen are carbon, selenium and/or oxygen such as carbon dioxide, carbon monoxide, carbon diselenide, carbon oxyselenide. It may be related to aging. It is also noted that free standing carbon skeletons containing small amounts of oxygen species are stable under ambient conditions. Carbon and/or selenium, along with selenium, appear to be susceptible to attack by environmental oxygen species in Se-C composites made of carbon skeletons with a moderate amount of oxygen species. Such oxidative instability can very well translate into poor electrochemical cycling performance of Li-Se rechargeable batteries; The carbon skeleton can be slowly oxidized by elemental selenium under an electrochemical cycling environment as well as the surrounding environment. The formation of oxidized carbon species in Se-C composites is undesirable. The amount of selenium in the oxidized carbon species may not participate in the electrochemical cycling of the rechargeable cell, resulting in a permanent loss of the specific capacity of the rechargeable cell; In addition to hosting selenium for its immobilization, the carbon skeleton also (1) transfers electrons from an external circuit to elemental selenium during the discharge process and (2 ^{) from the selenium anion (Se 2 -} ) to an external circuit during the charging process. It plays an important role in providing an electrically conductive path for harvesting electrons. When a portion of the carbon is oxidized by elemental selenium to form oxidized carbon species, the electrical resistance of the carbon skeleton can be substantially increased, thereby increasing the electrically conductive pathways for electron transport and imparting an electron harvest during each electrochemical cycle. and eventually reach a level at which the rechargeable battery will not function properly, not to mention the heat loss of electrical and chemical energy, which is practically undesirable for rechargeable batteries in terms of (1) low energy efficiency and (2) thermal management. .

On the other hand, Se-C composites made of carbon skeletons with moderate levels of oxygen species show no change in thermogravimetric analysis (TGA) behavior between fresh samples and samples aged under ambient conditions for about two and a half years; There is no exothermic weight loss at a temperature of about 200 to 250°C; Total weight loss of TGA is similar to selenium loading (by weight) when freshly made; Oxygen content does not increase; There is no decrease in density. Therefore, Se-C composites with a carbon skeleton with a sufficient amount of oxygen species can somehow achieve satisfactory levels of oxidative stability by applying strong chemical interactions with interfacial oxygen species between carbon and selenium to improve the oxidation stability of Se-C composites. Selenium immobilization is achieved.

Effective immobilization of selenium in the carbon skeleton can be achieved by the presence of a sufficient amount of oxygen species in the Se—C complex as interfacial species to enable strong chemical interactions between the carbon skeleton and selenium (in any chemical form). The desired amount of oxygen species in the immobilized selenium carbon composite may vary depending on the level of oxygen species in the carbon backbone source and the selenium loading level (by weight) in the Se—C composite. For selenium loadings of 50% or less, the amount of oxygen species in the Se—C complex is at least 0.63 mmol/g, at least 0.94 mmol/g, at least 1.56 mmol/g, or at least 2.19 mmol/g; For selenium loadings between 50% and 60% (including 60%), the amount of oxygen species in the Se-C complex is at least 0.5 mmol/g, at least 0.75 mmol/g, at least 1.25 mmol/g, or at least 1.75 mmol/g. g or more; For a selenium loading of 60% or higher, the amount of oxygen species in the Se—C complex is at least 0.31 mmol/g, at least 0.47 mmol/g, at least 0.78 mmol/g, or at least 1.09 mmol/g.

Note that a sufficient amount of oxygen species in the Se-C composite is not related to the oxygen species associated with exothermic weight loss at temperatures between 200°C and 250°C. Oxygen associated with exothermic weight loss at temperatures between 200° C. and 250° C. can occur very well after post-oxidation of Se—C composites under ambient conditions by oxygen species such as oxygen and/or moisture in air.

The amount of oxygen species in the porous carbon is generally, typically following a carbonization process in which the precursor is converted to carbon at a temperature typically below 700° C., more preferably below 650° C., further preferably below 600° C. is produced during porous carbon manufacturing processes, including activation processes that are activated with porous carbon at temperatures above 700°C, more preferably above 750°C, and possibly above about 800°C. The amount of porosity of the porous carbon depends on the degree of activation. The degree of activation depends on the activation temperature and activation time with different active chemicals such as water steam, CO ₂ , bases (eg NaOH, KOH, etc.), salts (eg K ₂ CO ₃ , Na ₂ CO ₃ , ZnCl _{2 , etc.).} is controlled by The harsher the activation conditions, the more porosity is created for the porous carbon. Activation at a higher temperature, such as 1,000° C. and/or for a certain period of time, results in a porous carbon with a higher level of porosity, which is desirable. However, activation at higher temperatures and/or for longer periods of time results in higher levels of loss of oxygen species to the porous carbon, resulting in lower levels of oxygen species in the porous carbon, which is undesirable. Higher levels of oxygen species may be conserved on the porous carbon by activation at relatively lower temperatures and/or for shorter periods of time, which may result in lower porosity, which is undesirable. The present disclosure is a porous carbon for selenium immobilization, preferably with a high level of selenium loading, characterized by an elevated activation energy, an elevated collision frequency or a reduced level of kinetic rate constant, preferably with a high level of immobilization. Consider the spirit of the present invention with respect to peaks of both the amount of porosity and the amount of oxygen species.

As described in the previous paragraph, higher activation temperatures and/or activation for longer times results in higher levels of oxygen species loss. One compromised approach can be activated at relatively low temperatures, eg, about 800° C. or less, and for relatively long periods of time, eg, 10 minutes or more. The present invention also embodies a post-treatment that results in an enhancement of the amount of oxygen species in the porous carbon in the porous carbon, which preferably has a high level of porosity, resulting from a severe activation process. Such oxygen-species enhanced porous carbon then has a desirable level in both the amount of porosity and the amount of oxygen species as described in the previous paragraph.

The porous carbon may be post-treated with an oxidizing agent. The oxidizing agent may be an oxygen-containing compound. The post-treatment(s) of the porous carbon may be carried out in the liquid phase or in the gas phase. Liquid phase workup of porous carbon can be carried out in an aqueous environment. Liquid phase workup of porous carbon can also be carried out in organic solvents which can be hydrophobic or hydrophilic in nature. Liquid phase workup of porous carbon can also be carried out under salt melting conditions.

The post-treatment of the porous carbon can be carried out with a liquid, for example, at a relatively low temperature below the boiling point of the liquid medium. Under elevated pressure above atmospheric pressure, the post-treatment temperature may be above the atmospheric boiling point of the liquid medium. Under vacuum, the post-treatment temperature needs to be below the atmospheric boiling point of the liquid medium.

Oxidizing agents include nitric acid, hydrogen peroxide, persulfate salts (eg, ammonium persulfate, sodium persulfate, or potassium persulfate), manganese salts, vanadium, chromium, or other transition metal related elements having a high oxidation valence state that permits reduction. can be The oxidizing agent may be oxygen, ozone, or an organic peroxide.

Post-treatment of porous carbon in an aqueous environment can be carried out under acidic conditions, pH-neutral conditions or basic conditions.

The post-treatment porous carbon can be washed and dried. The dried post-treated porous carbon is further treated at an elevated temperature (eg, ≥ 150 °C, ≥ 200 °C, or ≥ 250 °C) under static conditions, a gas flow, more preferably, an inert gas. can be Such heat-treatment may readjust the distribution of oxygen species associated _{with CO 2} formation, oxygen species associated with CO formation, and oxygen species associated with H _{2 O formation.}

Post-treatment of the porous carbon can enhance the amount of oxygen species to 30% or more, 50% or more, 100% or more, or 150% or more.

It may be more desirable to perform the immobilization of selenium at a temperature that conserves oxygen species that can act as important sites for promoting the chemical interaction of selenium with the carbon skeleton. The temperature for melting selenium in the pores of the porous carbon may be higher than the melting point of selenium. Doping with other elements such as S, Te or some other impurities can lower the melting point of selenium.

Selenium (with or without dopant) can be loaded into the carbon backbone by the impregnation method. Selenium can be dissolved in a solvent to form a selenium solution. The selenium solution is then impregnated into the porous carbon, and then the solvent is removed by evaporation, leaving the selenium inside the porous carbon. Such impregnation process may be repeated to achieve a sufficient amount of selenium loading. This method can also substantially lower the temperature of loading selenium into the porous carbon to a level below the melting point of selenium.

Sources for producing porous carbon for selenium immobilization include renewable carbon sources such as, but not limited to, biomass such as sugar, glucose, starch, protein, soybean wheat, nuts, husks (nuts, rice, wheat, etc.), fibers and sawdust from trees, or any carbon source associated with nature. The source for producing porous carbon for selenium immobilization may be a salt comprising carbon as described in the previous section. A source for producing porous carbon for selenium immobilization may be an acid containing carbon, such as citric acid, gluconic acid, or tannic acid. The carbon source may also be derived from a chemical, for example a polyol or a polymer such as polyacrylonitrile or polyphenol.

Description of the carbon manufacturing process.

The carbon material described herein can be obtained from a manufacturing method comprising the steps of:

(1) Mix the other ingredients: inert salt, activator and carbon precursor. The mixing process may include a ball-milling process or a freeze-drying process of solutions of different components; And

(2) The mixture was carbonized at high temperature under an inert atmosphere, and then washed with hot water to remove inorganic salts and dried to obtain a 3D porous material comprising interconnected curved thin carbon layers.

In step (1), the inert salt may be selected from potassium chloride, sodium chloride or sodium carbonate. The activator may be selected from potassium carbonate, potassium bicarbonate or potassium oxalate. The carbon precursor may be selected from the renewable carbon sources described above. In step (2), high-temperature carbonization may be performed at 800 to 900°C, preferably 800 to 850°C, for a carbonization time of 1 to 8 hours, preferably 1 to 4 hours.

The present invention embodies two main processes for making thin wall interconnected porous carbon self-template and extrinsic-template.

The self-moulding process may include the use of salts comprising carbon and capable of being carbonized, for example, potassium citrate, potassium gluconate, potassium tartrate, calcium citrate, sodium citrate, and the like. When the salt is heated, it first undergoes a melting process involving decomposition to form a viscous, odorous oil, such as water, carbon dioxide, carbon monoxide, light hydrocarbons and some tars, which can be oxygenated hydrocarbons; As decomposition proceeds, the cations of the original salt may be in soluble form along with the anions of the newly formed carbonate and/or oxalate and/or other forms of the salt; When the concentration of the newly formed carbonate, bicarbonate, oxalate and/or other anions reaches the saturation point of solubility, conditions for supersaturation of the newly formed carbonate, bicarbonate, oxalate and/or other anions as the decomposition process continues It begins to form; Note that supersaturation of the solubility of salts is thermodynamically metastable; Upon reaching a point of supersaturation where it is no longer (or already) kinetically stable, the newly formed salts of carbonates, bicarbonates, oxalates and/or other anions crystallize. Salts of organic carboxylates containing hydroxyl groups (eg, potassium citrate, potassium gluconate, potassium tartrate, etc.) may be crystallization inhibitors; Such crystallization inhibitors allow for higher levels of supersaturation formation, resulting in large populations of crystallites that are typically small in size. The freshly crystallized carbonate, bicarbonate or any other form of salt can be very uniform in particle size. As the temperature increases and/or the decomposition continues over time, the viscosity of the melt increases, which will uniformly coat the surface of the newly formed crystallites of the newly formed carbonate, bicarbonate, oxalate salt and/or other forms of salt. can The carbon then eventually solidifies at the surface of the newly formed crystallites. This carbon molding process is described in this disclosure as a self-moulding process, a carbonization process. The temperature of the self-moulding process may be less than 700°C. Such a self-moulding process can be performed by ramping the temperature at a constant rate or at various ramping rates. The self-moulding process can also be carried out by keeping the heating temperature constant at a temperature of 700° C. or lower.

As the temperature rises, the newly formed self-templated three-dimensional interconnected thin-walled carbon undergoes an activation process by the newly formed crystallites as an activating chemical. For example, the activation process is essentially a high-temperature redox reaction between carbon and newly formed crystallites, such as K ₂ CO ₃ (from potassium citrate as feedstock), K ₂ CO ₃ + C → K ₂ O + 2CO (which Occurs above about 700°C). Consumption of carbon can create porosity (especially microporosity) in the carbon, resulting in the formation of three-dimensional interconnected thin-walled porous carbon. The activation temperature may be up to 1,100°C. Ramping rates may range from less than 1°C/min up to 100°C/min. A flow of an inert carrier gas such as nitrogen or argon can be used in the porous carbon manufacturing process. Reactive gases such as CO ₂ and vapor may be used separately or together for and during activation.

There may be additional or secondary reactions that may contribute to the creation of porosity of the carbon. Some of these reaction processes may include: i) _{gasification of carbon by CO 2} produced during the carbonization and/or activation process, ii) reduction of metal oxides by carbon (eg, K ₂ O + C → CO + 2 K), iii) insertion of certain newly formed metal species (eg K) into the carbon layer, or iv) catalytic effects involving cations, which are particularly relevant for potassium. Carbon (C+CO ₂ = 2 CO) _{as a result of CO 2} produced by the decomposition of _{unreacted K 2} CO ₃ (K ₂ CO ₃ → K ₂ O + CO ₂ ) that occurs slowly at temperatures above 800 to 850° C. of particular relevance to the gasification of

The exogenous-template process optionally includes exogenous particles, e.g., activators (e.g., salts of alkali metals and carbonates, such as K ₂ CO ₃ , alkali metal hydroxides, optionally together with inert salts (e.g., KCl, NaCl, etc.) , such as KOH) to create a large amount of porosity from the carbon source. The foreign particles may be mixed with the carbon source before or after carbonization, more preferably before the carbonization step. Such mixing of the foreign particles with the carbon source may be accomplished by physical blending, optionally mechanical milling, or recrystallization of the carbon source with the chemical of the foreign particles from an aqueous solution, aqueous slurry or counterpart using an organic liquid medium. The drying process for the recrystallization process may be by evaporation, air-drying, oven-drying, spray-drying or freeze-drying.

When the mixture is heated in an ex-template process, carbonization-activation of the carbon source to the salt template particles occurs similar to that described in the previous paragraph for the self-templating process. During the carbonization process, the carbon source rises in temperature and can somehow melt over time and experience decomposition to form by-products such as CO ₂ , CO, water, light hydrocarbons and some viscous sticky heavy hydrocarbons. The melt viscosity increases and the melt eventually coats and solidifies on the surface of the foreign particle to form an interconnected thin-walled carbon coating on the surface of the foreign particle. As the temperature continues to rise, the activation process begins and porosity develops, which may be essentially based on a high temperature redox reaction, e.g., K ₂ CO ₃ + C → K ₂ O + 2CO, which occurs at temperatures above about 700 °C.

For example, when the foreign particle optionally comprises KC1 as an inert salt as another example, _{the melting point of the activating chemical, such as K 2} CO ₃ , is lowered from 891° C., in another example to about 630° C. _{Due to the formation of the KCI-K 2} CO ₃ liquid phase system at a temperature of the order of about 630° C., the activation of the interconnected thin-walled carbon is presumably due to the activating chemical (eg K ₂ CO _{3 in} this case) and the surface of the interconnected thin-walled carbon. Through a more intimate contact between the carbonized product (interconnected thin-walled carbon) and possibly due to the enhanced reactivity of _{K 2} CO _{3 can be significantly accelerated.} This means that exogenous-templating processes using exogenous particles comprising an activating chemical and optionally an inert salt actually (activation under less harsh conditions, i.e. at lower activation temperatures) produce a sufficient amount of porosity while preserving a sufficient amount of oxygen-containing species. may be a more viable strategy to achieve the synthesis of three-dimensional interconnected thin-walled porous carbons with At the same time, the surface of the carbon surface is isolated by the _{molten KCl-K 2} CO _{3 liquid phase, possibly limiting the diffusion of the formed CO 2} gaseous molecules to the surface of the solidified three-dimensional interconnected thin-walled porous carbon CO ₂ It is possible to prevent secondary reaction of the interconnected thin-walled porous carbon formed with , which is preferable to obtain a higher yield of interconnected thin-walled porous carbon. In addition, the “monolithic” molten KCI-K ₂ CO ₃ liquid phase can also limit the gas phase diffusion of released gases, such as carbon volatiles, which redeposit on the three-dimensional interconnected thin-walled porous carbon. This is desirable, as it can lead to increased yield of thin-walled porous carbon interconnected with the potential to become

Example 14. Three-dimensional interconnected thin-walled porous carbon nanomaterials: carbon preparation and characterization --- by exogenous-templating process: carbon source such as glucose, K ₂ CO ₃ Freeze drying of an aqueous mixture of an activating chemical, such as, and optionally an inert salt, such as KCl.

After dissolving appropriate amounts of KC1, K ₂ CO ₃ and glucose in distilled water, the solution is frozen in liquid nitrogen (-196° C.), then transferred to a lyophilizer, and freeze-dried at a temperature of -50° C. and a pressure of 0.06 mbar. to give a solid mixture of KCl, K ₂ CO _{3 and glucose.} The solid mixture was then carbonized at 850° C. for 1 hour under an inert atmosphere, cooled to room temperature, washed with hot distilled water, filtered, and dried to produce the three-dimensional interconnected thin-walled porous carbon nanomaterials shown in FIG. do.

The surface area of the glucose-derived three-dimensional interconnected thin-walled porous carbon nanomaterial ^{was measured to be 2,316 m 2} /g, with a total pore volume of 1.04 cm ³ /g and a micropore volume of 0.90 cm ³ /g with microporosity. It has about 86% pores described and about 14% pores described as meso and macroporosity. The N ₂ adsorption isotherm and the pore size distribution of the 3D interconnected thin-walled porous carbon nanomaterial are shown in FIG. 21 .

In another example, soy wheat is used instead of glucose. As can be seen in Figure 22, the macroscopic structure of the three-dimensional interconnected thin-walled porous carbon nanomaterial derived from soybean wheat is similar to that derived from glucose. However, this material has a surface area of 2,613 m ² /g, a pore volume of 1.42 cm ³ /g and a micropore volume of 1.0 cm ³ /g, and is described as meso- and macroporous with about 70% of the pores described as microporous. It has about 30% pores. The N ₂ adsorption isotherm and the pore size distribution of this material are shown in FIG. 23 . The amount of mesoporosity of this material derived from soybean wheat is higher than that derived from glucose.

[Table 5]

Table 5 shows precursors; activator/templating agent; precursor/activator/templating agent weight ratio; and a number of different examples of exo-templated three-dimensional interconnected thin-walled porous carbon nanomaterials for various combinations of carbonization ratios - resulting in different combinations of tissue properties and chemical makeup shown, where V _BET = apparent surface area; V _p = total pore volume; and V _fine = micro-pore volume.

Example 15: Three-dimensional interconnected thin-walled porous carbon nanomaterials: capacitor fabrication and performance.

The three-dimensional interconnected thin-walled porous carbon nanomaterial material in Example 14 can be used as an electrode in an electrochemical capacitor. The electrode comprises an organic binder, which may be, for example, PTFE or PVDF. Optionally, the electrode also comprises an electrically-conductive promoter, such as, for example, carbon black, graphene, carbon nanotubes, and the like. In a typical example, a mixture of 85% by weight of active material, 10% by weight of binder and 5% of electrically-conductive promoter is prepared.

The electrode manufacturing method may include preparing a slurry of different components or a dry mixture thereof in a mortar. The slurry can be coated on a current collector or molded into a self-supporting electrode such as a disk electrode. Electrodes may be pressed or roller-milled prior to use in electrochemical capacitors.

Symmetrical electrochemical capacitors can be assembled using the electrodes described above. Two electrodes of equal mass and thickness may be used. The current collector may be made of gold, stainless steel, aluminum, nickel, or the like, depending on the electrolyte used.

The electrolyte may be an aqueous acid solution such as sulfuric or chloric acid, a basic solution such as sodium or potassium hydroxide, a salt such as lithium sulfate, sodium sulfate, potassium sulfate and the like; The electrolyte may be an organic solution, such as an organic salt, for example, tetramethylammonium tetrafluoroborate, tetraethylammoniumtetrafluoroborate, tetrabutylammonium tetrafluoroborate, or the like, or an organic solution, such as an ionic liquid, such as 1- Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylide midazolium tetrafluoroborate, 1-butyl-3-methylimidazolium-tetrafluoroborate, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, etc. or as mentioned above It may be the same pure ionic liquid.

Electrochemical capacitors can be charged at 0.2 A/g, 0.5 A/g, 1 A/g, 5 A/g, 10 A/g, 20 A/g, 50 A/g or faster. The assembled electrochemical capacitors were tested using a computer-controlled potentiometer. The tests consisted of a cyclic voltammetry experiment (CV), an electrochemical impedance spectroscopy study (EIS) and a constant current charge/discharge (CD) cycling test. Cell voltages can be up to 1 V in acid or base solutions, up to 1.5 V in aqueous salt solutions, and up to 3 V in organic and ionic liquid electrolyte solutions.

For example, a 1 MH ₂ SO ₄ solution is used as the electrolyte. Electrochemical capacitors made of glucose-derived three-dimensional interconnected thin-walled porous carbon nanomaterials (also called glucose-based) have cell capacitances of 57 F/g at 0.2 A/g, and soy wheat-based three-dimensional interconnections. Electrochemical capacitors made of interconnected thin-walled porous carbon nanomaterials (called soy mill based) have a capacitance of 60 F/g. At a very large current density of 110 A/g, the cell capacitance is 24 and 31 F/g, respectively.

In another example, a 1 M Li ₂ SO ₄ solution is used as the electrolyte. The glucose-based electrochemical capacitor has a cell capacitance of 37 F/g at 0.2 A/g, and the soy wheat-based electrochemical capacitor is 39 F/g. At a current density of 20 A/g, the cell capacitance is 25 and 29 F/g, respectively.

In another example, a solution of EMImTFSI in acetonitrile (1:1 wt %) is used as the electrolyte. The glucose-based electrochemical capacitor has a cell capacitance of 36 F/g at 0.2 A/g, and the soy wheat-based electrochemical capacitor is 39 F/g. At a current density of 30 A/g, the cell capacitance is 28 F/g and 30 F/g, respectively.

A Ragone-type plot of electrochemical capacitors with different electrolytes is shown in FIG. X8. The robustness of the electrochemical capacitors was tested by long-term cycling at 5-10 A/g over more than 5,000 cycles.

Example 16 Three-dimensional interconnected thin-walled porous carbon nanomaterials: carbon production by ex-template process, carbon source such as sugar, glucose, soybean wheat, or sawdust, activating chemicals such as K ₂ CQ ₃ , and optionally an inert salt such as KC1 (optionally after milling).

Weigh out an appropriate amount of a carbon source such as sugar, glucose, soybean wheat, sawdust (eg, pine sawdust, cherry sawdust, or oak sawdust), activating chemicals such as K ₂ CO ₃ , and optionally inert salts, and the like; After physical mixing, which may include mechanical milling, it is transferred to a crucible that can be made of ceramic, steel, stainless steel, etc. Under a flow of an inert gas (which may be optional), the mixture is heated at a ramping rate of less than 100 °C/min, optionally to an immersion temperature of 700 °C or less or directly to an activation temperature of 700 °C or more for a carbonization period, It is maintained at temperature for a period of time for activation. Through the ramping process, the carbon source is _{decomposed into CO, CO 2} , water, light hydrocarbons, and heavy and sticky oily hydrocarbons that undergo carbonization. During the activation process, CO, CO ₂ , water, and carbon volatiles may continue to form.

After activation, the mixture is mixed with water and optionally neutralized with an acid such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid and the like. The carbon slurry is then filtered and water to a level having a low level of electrical conductivity, e.g., less than 5,000 μS/cm, less than 3,000 μS/cm, less than 1,000 μS/cm, and less than 300 μS/cm, 100 μS Wash optionally with deionized or distilled water to a conductivity of less than /cm, or even less than 50 μS/cm. The filtered cake can be dried in an oven to remove the water.

The resulting three-dimensional interconnected thin-walled porous carbon nanomaterials were then characterized by oxygen content, SEM, XRD, Raman, TGA-DSC, N ₂ and CO ₂ BET surface area and pore size distribution.

The following Table 5 shows three-dimensional interconnected thin-walled porous carbon nanomaterials such as 237-8 (self-templated carbon synthesized from potassium citrate), 237-51A (self-templated carbon from potassium citrate), SKK2 (exogenous-templated carbon) ) versus commercial carbons such as Elite C (available from Calgon Carbon of Pittsburgh, PA); YP-50 (available from Kruray Co. Ltd, Osaka, Japan); Ketjen carbon black (available from Lion Specialty Chemicals Co. Ltd., Tokyo, Japan); Elemental analysis of Maxsorb (available from Kansai Coke and Chemicals Co. Ltd., Hyogo, Japan) is shown.

[Table 6]

Table 6 above shows two groups of carbons, one group being three-dimensional interconnected thin-walled porous carbon nanomaterials such as 237-8 (self-templated carbon synthesized from potassium citrate), 237-51A (exogenous from glucose- with template carbon), 237-101D (self-template carbon synthesized from potassium citrate) and SKK2 (exogenous-template carbon from sugar), oxygen content greater than 1.5 wt%, greater than 2.0 wt%, greater than 3 wt%, or 4.0 more than % by weight. XRD studies show that all of the carbon materials in the table above are amorphous. Raman studies show in the table above that the carbon material is also essentially amorphous and exhibits amorphous carbon signature Raman scattering at both the D-peak and G-peak.

The prepared interconnected thin-walled porous carbon is then used to prepare selenium immobilization. Appropriate amounts of selenium and carbon were mixed together as previously described, followed by melting selenium into interconnected thin-walled porous carbon in the presence of elevated levels of oxygen species to produce the immobilized selenium of the present invention; For the process of making immobilized selenium in the present invention, refer to the previous description. The immobilized selenium is then characterized by oxygen content analysis, XRD, Raman, SEM, TGA-DSC, and the like.

Table: Immobilized Selenium vs. Oxygen Content Less than 1.5 wt% in Three-Dimensional Interconnected Thin Wall Porous Carbon Nanomaterials Having More Than 1.5 wt%, More Than 2.0 wt%, More Than 3 wt%, or More Than 4.0 wt% , analysis of the oxygen content of immobilized carbon-selenium composites prepared with commercially available carbon that is less than 2.0 wt%, less than 3 wt%, or less than 4.0 wt%.

[Table 7]

Table 7 above shows two different groups of immobilized selenium, one group (called group I, ie Ketjen 600JD, 237-8, 237-51A, 237-67, 237-101D and SKK-2) is 3 having an oxygen content ranging from 1% to 10%, 1.5% to 9%, or 2% to 8%, which is approximately half the oxygen content for dimensionally interconnected thin-walled porous carbon nanomaterials with another group (Group II, i.e. Elite C and called Maxsorb MSP20X) have an oxygen content that is at least five times the oxygen content of carbon, or greater than 8%, greater than 9%, or greater than 10%. Note that Ketjen carbon is a non-porous carbon where the carbon-selenium complex is considered unimmobilized selenium; Therefore, its oxygen content is very low, less than 1%.

Oxygen species in group I immobilized selenium may play an important role as interfacial chemical groups in the immobilization of selenium, which allows for strong interactions between carbon and selenium, leading to the interior pore interior of three-dimensional interconnected thin-walled porous carbon nanomaterials. results in tighter packing of selenium atoms or species, which can be demonstrated by the enhanced collision frequency shown as an example of the present invention. Such interactions between the carbon skeleton and selenium atoms or selenium species can also be further demonstrated with higher intrinsic densities.

For example, a three-dimensional interconnected thin-walled porous carbon nanomaterial, e.g., a sample of immobilized selenium made of self-templated carbon synthesized from potassium citrate at a carbon to selenium ratio of 50-50 (by weight) . It was surprising to find that the density was 3.42 g/cm ^{3 .} Note that the density of selenium is 4.819 g/cm ³ . Using 4.819 g/cm ³ , the carbon density in the immobilized selenium composite is calculated to be ^{about 2.8 g/cm 3 .} Also, diamond has a density of 3.5 g/cm ³ ; Graphite has a density of about 2.3 g/cm ³ ; Note that amorphous carbon has a typical density of about 2.0 g/cm ³ .

The immobilized selenium is then prepared by mixing an appropriate amount of immobilized selenium as previously described, an aqueous or organic medium and at least one binder, followed by coating in a charge collector such as, for example, aluminum foil to obtain the immobilized selenium. It is used to manufacture the cathode of a rechargeable battery by creating a cathode comprising Reference is made to the previous description for the process of manufacturing the cathode including immobilized selenium in the present invention.

The resulting cathode comprising immobilized selenium is then used to assemble a rechargeable battery with an anode, eg, lithium, a separator, an electrolyte. For the process of assembling the rechargeable battery including the cathode including immobilized selenium in the present invention, refer to the previous description.

The resulting carbon sample can be further used in the electrode manufacturing process for capacitors or rechargeable batteries.

Embodiments have been described with reference to the accompanying drawings. Modifications and changes will occur to the rest upon reading and understanding of the foregoing embodiments. Accordingly, the above-described embodiments should not be construed as limiting the present disclosure.

Claims (10)

A method for preparing an immobilized selenium body comprising the steps of:
(a) forming a mixture of selenium, exogenous-template carbon, and oxygen;
(b) heating the mixture of step (a) to a temperature higher than the melting temperature of selenium; and
(c) cooling the heated mixture of step (b) to ambient or room temperature to form an immobilized selenium body. The method of claim 1 , wherein for a selenium loading of < 50% at carbon, the amount of oxygen in the mixture is >0.63 millimoles/gram. The method of claim 1 , wherein for selenium loadings between 50% (exclusive) and 60% (inclusive) at carbon (ie 50% < selenium loading ≤ 60%), the amount of oxygen in the mixture is at least 0.5 mmol/gram. The method of claim 1 , wherein for a selenium loading of > 60% on carbon, the amount of oxygen in the mixture is at least 0.31 millimoles/gram. The method of claim 1 , further comprising, prior to step (a), activating the carbon to form pores in the carbon. 6. The method of claim 5, further comprising combining or mixing the activated carbon with an oxidizing agent. 7. The method of claim 6, wherein the oxidizing agent comprises at least one of:
nitric acid;
hydrogen peroxide;
organic peroxides;
Oxygen; and/or
ozone. 7. The method of claim 6, wherein the oxidizing agent comprises at least one of the following in an aqueous environment:
ammonium persulfate;
sodium persulfate;
potassium persulfate;
manganese salts;
vanadium salts, and/or
chromium salt. The method of claim 1 , wherein the exogenous-templated carbon is prepared by a process comprising the steps of:
freezing the liquid carbon-containing solution to form a solid carbon-containing mixture;
carbonizing the solid carbon-containing mixture; and
washing, filtering, and drying the carbonized mixture. An immobilized selenium body comprising a mixture of:
selenium;
exogenous-template carbon; and
Oxygen.

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