CN113948699B - Preparation method of MOF-5 containing six carbonyl functional groups and application of MOF-5 in high Wen Jia ion battery - Google Patents

Abstract

The invention belongs to the technical field of batteries, and relates to a preparation method of MOF-5 containing six carbonyl functional groups and application of the MOF-5 in a high Wen Jia ion battery. The invention discloses a preparation method of MOF-5 containing six carbonyl functional groups, which comprises the following steps: dissolving terephthalic acid and triethylamine in the mixed solution A to obtain solution I; dissolving zinc acetate dihydrate in the mixed solution B to obtain a solution II; and (3) dripping the solution II into the solution I, mixing and stirring to obtain a precipitate, respectively cleaning the precipitate with an organic solvent and an alcohol solvent, and drying to obtain the MOF-5. The invention also discloses a Gao Wenjia ion battery which is prepared by uniformly mixing raw materials containing MOF-5, coating the raw materials on a current collector to prepare a negative electrode, and sequentially assembling a battery negative electrode cover, a counter electrode, a diaphragm, electrolyte, a negative electrode, an elastic sheet and a battery positive electrode cover. And the high Wen Jia ion battery has ultrahigh cycling stability, and after 3000 cycles of cycling under high current density, the attenuation rate of each cycle is only 0.018 percent.

Description

Preparation method of MOF-5 containing six carbonyl functional groups and application of MOF-5 in high Wen Jia ion battery

Technical Field

The invention belongs to the technical field of batteries, and relates to a preparation method of MOF-5 containing six carbonyl functional groups and application of the MOF-5 in a high Wen Jia ion battery.

Background

In the face of fossil fuel depletion and environmental crisis issues, developing high performance energy conversion and storage devices is considered one of the key challenges to deal with the global energy crisis. Currently, in the family of energy storage devices, potassium Ion Batteries (PIBs) are becoming a glaring star because of their ideal high energy density and broad commercial application prospects, with the unique advantages of: compared with lithium, the lithium-ion battery has the advantages that the lithium-ion battery is rich in reserves and lower in cost (2.09 vs 0.0017wt%), and Al foil can be used for replacing Cu foil as a current collector, so that the cost is further reduced; k (K) ⁺ Is weak to form smaller solvated ions and therefore is smaller than Li ⁺ And Na (Na) ⁺ The ionic conductivity is better; the redox potential of PIBs is lower than that of sodium ion batteries (-2.93 vs-2.71V).

However, to date, due to K ⁺ Ions are difficult to rapidly intercalate/deintercalate in the electrode material, causing slow reaction kinetics, and further leading to PIBs still facing a large problem of poor cycling stability. This is mainly due to K ⁺ Is far larger than Li ⁺ And Na (Na) ⁺ Thereby resulting in a radius at K ⁺ A significant change in volume is caused during the intercalation/deintercalation of the electrode material, which in turn leads to a rapid decay of specific capacity. This problem becomes worse under high temperature operating conditions because of K ⁺ The insertion/extraction speed of the battery is remarkably increased, so that the volume is rapidly changed, thereby causing breakage of the electrode structure and deterioration of the battery cycle stability. For example, zhang (chem. Commun. 55, 11311 (2019)) et al reported a KVPO-based ₄ Capable of 50 stable charge and discharge cycles at high temperatures of 55 ℃ and current densities of 100 mA/g; wang (adv. Energy Mater 9, 1802986 (2019)) et al suggested that the use of an azo group as the center of the electrochemical redox reaction enabled PIBs to operate at high temperatures of 60 ℃ and stable 80 cycles at a current density of 310 mA/g with a specific capacity retention of 81%. However, in these reports, the cycle stability and cycle times of high temperature PIBs were very poor. Therefore, to drive the further development of high temperature PIBs, the most important issue is to solve the problem of cycle stability, and the most important issue is to find a suitable potassium storage mechanism and energy storage material.

Disclosure of Invention

The invention aims at solving the problems in the prior art, and provides a preparation method of MOF-5 containing six carbonyl functional groups and application of the MOF-5 in a high Wen Jia ion battery, which can effectively improve the specific capacity of the battery and ensure that the potassium ion battery has excellent cycle stability under the high-temperature condition.

The aim of the invention can be achieved by the following technical scheme:

a method of preparing MOF-5 containing six carbonyl functional groups, the method comprising the steps of:

s1, dissolving terephthalic acid and triethylamine in a mixed solution A to obtain a solution I;

s2, dissolving zinc acetate dihydrate in the mixed solution B to obtain a solution II;

s3, dripping the solution II into the solution I, mixing and stirring to obtain a precipitate, respectively cleaning the precipitate with an organic solvent and an alcohol solvent, and drying to obtain the MOF-5.

Terephthalic acid is a source of carbonyl functional groups, and the added deionized water is used for controlling the morphology of the MOF-5 self-assembly process, so that the circulation stability is improved.

Preferably, the mixed solution A and the mixed solution B are mixed solutions of N, N-dimethylformamide and deionized water.

Further preferably, the volume ratio of N, N-dimethylformamide to deionized water in the mixed solution A is (45-110): 1; the volume ratio of N, N-dimethylformamide to deionized water in the mixed solution B is (60-130): 1.

More preferably, deionized water is added to the first solution and the second solution in the same amount, and the amount is 2-4ml.

Preferably, the mass ratio of terephthalic acid to zinc acetate dihydrate is 1: (3-5).

Further preferably, in step S1, 1-2 ml of triethylamine is added per gram of terephthalic acid, and 80-90 ml of the mixed solution A is dissolved per gram of terephthalic acid; in step S2, zinc acetate dihydrate is dissolved in (25-35) ml of the mixed solution B.

Under the proportion of the raw materials, the prepared MOF-5 has fewer impurities, and is beneficial to realizing the cycle stability of the battery. If the deionized water volume is changed, the materials are agglomerated, scattered and hollow, and the structures are unfavorable for the transmission of electrons and ions.

Preferably, the alcohol solvent is methanol.

The MOF-5 containing six carbonyl functional groups provided by the invention is a saqima-like material with a porous structure, which consists of small particles.

The porous structure can promote the permeation of electrolyte and accelerate the transportation of electrons and ions.

The invention also provides an application of the MOF-5 containing six carbonyl functional groups in a high Wen Jia ion battery, which comprises the following steps: MOF-5, conductive material, binder and N-methyl pyrrolidone are uniformly mixed and then coated on a current collector to prepare a negative electrode, and the negative electrode, a counter electrode, a diaphragm and electrolyte are assembled into the Gao Wenjia ion battery.

Preferably, the mass percentages of MOF-5, conductive material, binder and N-methyl pyrrolidone are 7-9%, 2-3%, 1-2% and 86-90%, respectively.

Further preferably, the loading of MOF-5 on the current collector is 0.85-1.8mg/cm ² 。

The mass percentages of the raw materials of the negative electrode are controlled within the range, so that uniform and sticky slurry can be obtained, and active materials can be better attached to the current collector, thereby improving the stability of the battery in the circulating process. And MOF-5 on the current collector of the higher load, the higher battery power/energy density, but with the increase of load, the electrode thickness is thicker, the diffusion of ions becomes slower, which can cause the rate performance to become low, and the load becomes larger, so that the active material is easy to fall off, resulting in the poor battery cycle performance, so the MOF-5 load is preferably controlled to 0.85-1.8mg/cm ² 。

Preferably, the conductive material comprises one or more of acetylene black, conductive carbon black, graphene, carbon nanotubes and carbon fibers.

Preferably, the binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyvinyl alcohol and fluorinated rubber.

Preferably, the current collector is one or more of aluminum foil, copper foil and tin foil.

Preferably, the separator is a glass fiber separator.

Preferably, the electrolyte is a glycol dimethyl ether solution containing potassium difluorosulfimide.

Further preferably, the concentration of potassium difluorosulfimide is 2 to 4mol/L.

The ethylene glycol dimethyl ether (DME) solution of potassium bis-fluorosulfonyl imide (KFSI) is beneficial to the transmission of metal cations, and the concentration of 2-4mol/L is beneficial to forming a uniform solid electrolyte interface film, so that the stability and specific capacity of the battery are improved.

Preferably, the counter electrode is metallic potassium.

Preferably, the assembly process is performed in a glove box filled with argon.

Further preferably, the content of oxygen and water in the glove box is less than 0.1 ppm.

The electrolyte and counter electrode selected in the present invention are extremely sensitive to water and oxygen, and the preparation and assembly processes must be carried out in a glove box having a water and oxygen content of less than 0.1 ppm.

Preferably, the assembled potassium ion battery is a 2032 type button potassium ion battery.

And (3) carrying out 3-circle constant-current charge-discharge test on the prepared high Wen Jia ion battery at the current density of 100 mA/g, enabling the final state of the battery to be in a complete discharge state, then dismantling the battery in a glove box, taking out the negative electrode, washing with absolute ethyl alcohol, drying, and researching the energy storage mechanism of the battery. The energy storage mechanism of the 2032 button type Gao Wenjia ion battery in the charge and discharge processes is as follows: the charge density around oxygen atoms in carbonyl functional groups in the discharge process is increased, so that the oxygen atoms with high electronegativity can capture electrons more easily, and further the C=O double bond is broken to be connected with K ⁺ Energy storage is realized through combination; during charging, oxygen atoms lose electrons to reduce the charge density around, resulting in strong infrared vibration, so that C-O ⁻ And K ⁺ The bond energy between them is weakened, K ⁺ Back into the electrolyte.

Compared with the prior art, the invention has the following beneficial effects:

1. according to the invention, the porous MOF-5 material containing six carbonyl functional groups is prepared by simple solution mixing and self-assembly, the porous structure of the material can further improve the stability of the potassium ion battery, and the original morphology structure of the material can be maintained after circulation; six carbonyl functional groups provide six electrochemical reaction energy storage centers, so that the specific capacity of the battery is effectively improved.

2. The invention adopts the mechanism of energy storage of carbonyl functional groups through C=O fracture and K ⁺ Bonding ofThe reaction of forming-COOK to realize energy storage avoids the defect of the existing energy storage mechanism, relieves the volume change caused by the electrochemical reaction process, and ensures that the potassium ion battery has excellent cycling stability under the high temperature condition.

3. The 2032 button type Gao Wenjia ion battery with the MOF-5 assembled by the negative electrode has excellent cycle stability, coulombic efficiency and multiplying power performance.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of MOF-5 prepared in example 1 of the present invention.

FIG. 2 is a Transmission Electron Microscope (TEM) image of MOF-5 prepared in example 1 of the present invention.

FIG. 3 is a High Resolution Transmission Electrical (HRTEM) diagram of MOF-5 prepared in example 1 of the present invention.

FIG. 4 is a graph showing the pore size distribution of MOF-5 prepared in example 1 of the present invention.

Fig. 5 is a cyclic voltammogram of a button type Gao Wenjia ion cell of model 2032 constructed in example 2 of the invention.

Fig. 6 is a constant current charge and discharge graph of a 2032 type button Gao Wenjia ion battery constructed in example 2 of the invention.

Fig. 7 is a graph of the rate performance of a button type Gao Wenjia ion battery of type 2032 constructed in example 2 of the invention.

Fig. 8 is a graph of cycle stability and coulombic efficiency at a small current density of 200 mA/g for a button Gao Wenjia ion battery of model 2032 constructed in example 2 of this invention.

Fig. 9 is a graph of cycle stability and coulombic efficiency at a high current density of 500 mA/g for a button Gao Wenjia ion battery of model 2032 constructed in example 2 of this invention.

FIG. 10 is a Fourier infrared (FTIR) chart of a button type Gao Wenjia ion battery of model 2032 constructed by MOF-5 of example 3 of the invention before and after full discharge at a high temperature of 62.5 ℃.

FIG. 11 is a Scanning Electron Microscope (SEM) image of a negative electrode material prepared after cycling of a button type Gao Wenjia ion battery of model 2032 constructed by MOF-5 in example 4 of the invention.

FIG. 12 is a graph of impedance (EIS) before and after cycling of a button Gao Wenjia ion battery model 2032 constructed as MOF-5 in example 4 of the invention.

FIG. 13 is a Scanning Electron Microscope (SEM) image of MOF-5 prepared in comparative example 1 of the present invention.

FIG. 14 is a Scanning Electron Microscope (SEM) image of MOF-5 prepared in comparative example 2 of the present invention.

FIG. 15 is a Scanning Electron Microscope (SEM) image of MOF-5 prepared in comparative example 3 of the present invention.

FIG. 16 is a graph of cycling stability and coulombic efficiency of button Gao Wenjia ion cells constructed from MOF-5 of comparative example 1 of the present invention.

FIG. 17 is a graph of cycling stability and coulombic efficiency of button Gao Wenjia ion cells constructed from MOF-5 of comparative example 2 of the present invention.

FIG. 18 is a graph of cycling stability and coulombic efficiency of button Gao Wenjia ion cells constructed from MOF-5 of comparative example 3 of the present invention.

Detailed Description

The following are specific examples of the present invention, and the technical solutions of the present invention are further described, but the present invention is not limited to these examples.

Example 1

2.5. 2.5 g terephthalic acid, 4ml of triethylamine was dissolved in a mixed solution of 200ml of N, N-Dimethylformamide (DMF) and 3ml of deionized water to obtain solution one. Zinc acetate dihydrate 8.5. 8.5 g was dissolved in a mixed solution of DMF 250ml and deionized water 3ml to give solution two, which was then dropped into solution one, and after mixing and stirring for 3.5 hours, the resulting white precipitate was centrifugally washed with DMF and methanol, and the resulting precipitate was dried at 85 ℃ to obtain MOF-5. The morphology of the prepared MOF-5 as a caramel treats-like material with a porous structure consisting of small particles can be observed by SEM of fig. 1 and TEM of fig. 2. It can be seen from the HRTEM diagram of FIG. 3 that the prepared MOF-5 has good crystallinity and is a polycrystalline material. The pore size distribution diagram of fig. 4 further illustrates that the material has a rich void structure and is a porous material.

Example 2

Preparing a negative electrode:the anode raw materials are MOF-5 and acetylene black, polyvinylidene fluoride and N-methyl pyrrolidone in the embodiment 1, and the raw materials are respectively 8%, 2%, 1.5% and 88.5% by mass percent, and are uniformly mixed and then coated on a copper foil, so that the MOF-5 loading capacity on the copper foil is 0.9mg/cm ² After drying, the copper foil was made into a round plate with a diameter of 12 mm as a negative electrode.

Assembling a potassium ion battery: in a glove box, sequentially assembling a negative electrode, a potassium block, a glass fiber diaphragm and an ethylene glycol dimethyl ether solution containing 3mol/L of potassium bis (fluorosulfonyl) imide into a button potassium ion battery. The performance test is carried out at a high temperature of 62.5 ℃, and the cyclic voltammetry curve is shown in fig. 5, so that other curves except for the first cycle can be observed to be basically completely overlapped, and the battery has smaller polarization and good stability. FIG. 6 is a constant current charge-discharge curve with specific capacities of 210 and 1183 mAh/g, respectively, for the first charge-discharge. Fig. 7 is a graph of the rate performance, and it can be seen that when the current density is changed from 100 to 1000 mA/g, the specific capacity is only changed from 210 to 120 mAh/g, and the battery has better rate performance. Fig. 8 and 9 show the cycle stability and coulombic efficiency at different current densities and can be stably cycled for 3000 cycles at large current densities, each cycle having a specific capacity decay of 0.018%.

Example 3

Preparing a complete discharge product: the high Wen Jia ion battery prepared in example 2 was subjected to 3-cycle constant current charge-discharge test at a current density of 100 mA/g, and the final state of the battery was brought to a fully discharged state, after which the battery was disassembled in a glove box, the negative electrode was taken out, washed with absolute ethanol, and dried at 60 ℃. Fig. 10 is a fourier infrared spectrum (FTIR) of MOF-5 before and after complete discharge, showing that the intensity of carbonyl functional group c=o after complete discharge becomes weaker, indicating that the electrochemical reaction proceeds on the carbonyl functional group, and c=o is an energy storage center of the electrochemical reaction, which is a new energy storage mechanism for the surface functional group.

Example 4

The product after 100 cycles of preparation: the high Wen Jia ion battery prepared in example 2 was subjected to a 100-cycle constant current charge-discharge test at a current density of 2000 mA/g and the final state of the battery was brought to a fully charged state, after which the battery was disassembled inside a glove box, the negative electrode was taken out, washed with absolute ethanol, and dried at 60 ℃. By observing a Scanning Electron Microscope (SEM) image of FIG. 11, it can be found that the structure is not changed significantly compared with that before the reaction, which means that the mechanism of energy storage of the surface functional group can avoid the breakage of the electrode structure caused by the electrochemical process, and improve the cycle stability of the battery. Fig. 12 is an impedance diagram before and after cycling, and it can be seen that the semi-circle diameter before and after cycling does not change significantly, which indicates that the carbonyl functional group energy storage can form a stable electrolyte interface film on the electrode surface, which is beneficial to realizing the stability of battery cycling.

Comparative example 1

The difference compared to example 1 is that no deionized water was added to the first and second solutions. It can be seen from the SEM image of fig. 13 that the morphology at this time is mainly based on scattered particles, and the particles are agglomerated.

Comparative example 2

The difference compared to example 1 is that 2ml deionized water was added. As can be seen from the SEM image of FIG. 14, the morphology at this time is mainly a square structure of different sizes.

Comparative example 3

The difference compared to example 1 is that 4ml deionized water was added. It can be seen from the SEM image of fig. 15 that the morphology at this time is mainly a broken random block structure.

Comparative example 4

The difference compared to example 2 is that MOF-5 was prepared as in comparative example 1. When the performance test was conducted at a high temperature of 62.5℃and the current density of 500 mA/g was observed in FIG. 16, it was found that the specific capacity of the battery was reduced from 165 mAh/g to 0 after 70 cycles, and the cycle stability was poor.

Comparative example 5

The difference compared to example 2 is that MOF-5 was prepared as in comparative example 2. When performance test was conducted at a high temperature of 62.5 ℃, it was found from the observation of FIG. 17 that the specific capacity was initially higher at 310 mAh/g at a current density of 500 mA/g, but rapidly decayed to 10 mAh/g after 60 cycles, and the cycle stability was poor.

Comparative example 6

The difference compared to example 2 is that MOF-5 was prepared as in comparative example 3. Performance testing at 62.5 ℃ at high temperature, observing fig. 18, shows that at a current density of 500 mA/g, the initial specific capacity is 110 mAh/g, but after 40 cycles, the rapid decay is 0 mAh/g, and the specific capacity and the cycling stability are poor.

In conclusion, the MOF-5 containing six carbonyl functional groups prepared by the method has good thermal stability, relieves volume change caused by an electrochemical process, and avoids damage to an electrode structure; and the potassium ion battery assembled by the negative electrode has higher specific capacity, and has excellent cycle stability under the high-temperature condition.

The specific embodiments described herein are offered by way of example only to illustrate the spirit of the invention. Those skilled in the art may make various modifications or additions to the described embodiments or substitutions thereof without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.

Claims (5)

1. A method for preparing MOF-5 containing six carbonyl functional groups, comprising the steps of:

s1, dissolving terephthalic acid and triethylamine in a mixed solution A to obtain a solution I;

s2, dissolving zinc acetate dihydrate in the mixed solution B to obtain a solution II;

s3, dripping the solution II into the solution I, mixing and stirring to obtain a precipitate, respectively cleaning the precipitate with an organic solvent and an alcohol solvent, and drying to obtain the MOF-5;

the mixed solution A and the mixed solution B are both mixed solutions of N, N-dimethylformamide and deionized water;

the volume ratio of N, N-dimethylformamide to deionized water in the mixed solution A is 66.7:1;

the volume ratio of the N, N-dimethylformamide to the deionized water in the mixed solution B is 83.3:1;

the mass ratio of terephthalic acid to zinc acetate dihydrate is 1 (3-5);

in the step S1, 1-2 ml of triethylamine is corresponding to each gram of terephthalic acid, and each gram of terephthalic acid is dissolved in 80-90 ml of mixed solution A;

in the step S2, each gram of zinc acetate dihydrate is dissolved in (25-35) ml of the mixed solution B;

MOF-5 containing six carbonyl functions is a saqima-like material consisting of small particles with a porous structure;

the prepared MOF-5 containing six carbonyl functional groups is used as a cathode material of a high Wen Jia ion battery.

2. A high Wen Jia ion battery, wherein the negative electrode of the potassium ion battery comprises MOF-5 comprising six carbonyl functional groups prepared by the method of claim 1.

3. The potassium-ion battery according to claim 2, wherein the raw material of the anode includes: MOF-5, conductive material, binder and N-methyl pyrrolidone, which are respectively 7-9%, 2-3%, 1-2% and 86-90% by mass.

4. The potassium-ion battery of claim 2, wherein the preparation process of the potassium-ion battery comprises: and uniformly mixing the raw materials of the negative electrode, coating the mixture on a current collector to prepare the negative electrode, and sequentially assembling a battery negative electrode cover, a counter electrode, a diaphragm, electrolyte, the negative electrode, an elastic sheet and a battery positive electrode cover to prepare the Gao Wenjia ion battery.

5. The potassium ion battery of claim 4, wherein the loading of MOF-5 on the current collector is 0.85-1.8mg/cm ² 。

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