CN109671978B

CN109671978B - High-voltage-resistant solid polymer electrolyte, preparation method and application thereof

Info

Publication number: CN109671978B
Application number: CN201811562050.3A
Authority: CN
Inventors: 晏成林; 刘杰; 钱涛
Original assignee: Suzhou University
Current assignee: Huzhou Dega Energy Technology Co ltd
Priority date: 2018-12-20
Filing date: 2018-12-20
Publication date: 2022-02-11
Anticipated expiration: 2038-12-20
Also published as: CN109671978A

Abstract

The present invention relates to a high-voltage-resistant solid polymer electrolyte, a preparation method and application thereof, comprising a polymer matrix and a lithium salt contained in the polymer matrix, wherein the polymer matrix is a fluorine-containing organic monomer It is prepared by carrying out a polymerization reaction under the action of a catalyst, and the fluorine-containing organic monomer is a fluorine-containing cyclic or unsaturated chain organic monomer. When used in high-voltage solid-state polymer batteries, it can avoid being oxidized and decomposed, so as to achieve long-term stable cycles; the solid-state polymer electrolyte has high room temperature ionic conductivity.

Description

High-voltage-resistant solid polymer electrolyte, preparation method and application thereof

Technical Field

The invention belongs to the field of polymer electrolytes, and relates to a high-voltage-resistant solid polymer electrolyte, a preparation method thereof and application thereof in a solid lithium metal battery.

Background

From intelligent electronic devices such as mobile phones to pure electric/hybrid vehicles, rechargeable lithium batteries are increasingly widely used in various aspects of life. At present, liquid organic carbonate electrolyte is generally adopted by lithium batteries used in large-scale commercialization, and a plurality of potential safety hazards exist, including leakage, flammability, explosion and the like. The solid polymer electrolyte does not contain a liquid solvent, so that the safety performance of the lithium battery can be improved to a great extent. Meanwhile, the lithium metal solid-state battery also has the advantages of high energy density, wide working temperature range, lithium dendrite inhibition and the like, and becomes one of research hotspots.

In addition, with the rapid development of social science and technology, people also put higher demands on the energy density of lithium batteries. The energy density of the battery is improved by improving the specific capacity of the electrode material, and the output voltage of the battery can be improved. However, it has been difficult to achieve a voltage window of 5V or more in solid polymer electrolytes so far, meaning that it is difficult to use these solid electrolytes in electrode materials for high voltage, and thus it is difficult to achieve a solid polymer battery with higher energy density. The biggest reason for this is that solid polymer electrolytes are easily oxidized on the surface of the positive electrode and reduced on the lithium negative electrode, causing continuous decomposition and consumption of the electrolyte, resulting in increasingly poor interfacial and ion transport properties, and ultimately rendering the battery useless. Meanwhile, the solid polymer electrolytes reported in the literature have different problems of low ionic conductivity, poor mechanical strength and the like, thereby affecting the commercial application of the solid polymer batteries.

In summary, although the solid polymer electrolyte has great advantages and application prospects, most of the currently reported solid polymer electrolytes have difficulties in meeting the requirements of high voltage resistance, high ionic conductivity, high mechanical strength and the like. In view of the above, it is desirable to provide a high-performance solid polymer electrolyte with high voltage resistance to overcome the above drawbacks.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a high-voltage-resistant solid polymer electrolyte.

In order to achieve the purpose, the invention adopts the technical scheme that: a high-voltage-resistant solid polymer electrolyte comprises a polymer matrix and lithium salt contained in the polymer matrix, wherein the polymer matrix is prepared by carrying out polymerization reaction on a fluorine-containing organic monomer under the action of a catalyst, and the fluorine-containing organic monomer is a fluorine-containing cyclic or unsaturated chain organic monomer.

Preferably, the fluorine-containing organic monomer is one or more selected from the group consisting of fluoroethylene carbonate (FEC), perfluoro-1, 2-dimethylcyclohexane, perfluoro-1, 3-dimethylcyclohexane, ethyl 4, 4-difluorocyclohexanecarboxylate, 2,3, 3-tetrafluoropropyl methacrylate and 3- (perfluoro-n-octyl) -1, 2-propylene oxide.

Preferably, the lithium salt is a mixture of one or more selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis (oxalate) borate, lithium difluoro (oxalate) borate, lithium bis (trifluoromethanesulfonyl) imide and lithium bis (fluorosulfonyl) imide.

Preferably, the catalyst is a mixture consisting of one or more of stannous isooctanoate, dibutyltin dilaurate, triethylene diamine, dimethyl cyclohexylamine and dimethylamino ethoxy ethanol.

Optimally, the material comprises the following raw material components in percentage by mass:

65-90% of a fluorine-containing organic monomer;

9.9-30% of lithium salt;

0.1 to 5 percent of catalyst.

Further, the mixture of the fluorine-containing organic monomer, lithium salt and catalyst is injected into the porous support material to perform polymerization.

Furthermore, the electrochemical stability window of the material is more than or equal to 6.3V, and the ionic conductivity is 6.5 multiplied by 10^-5～2.5×10^-4S·cm^-1。

Further, the porous support material is a polyethylene microporous membrane, a polypropylene microporous membrane, a cellulose non-woven membrane, a polyimide non-woven membrane or a glass fiber membrane.

Still another object of the present invention is to provide a method for preparing the above high voltage resistant solid polymer electrolyte, which comprises the following steps: (a) dissolving lithium salt and a catalyst in a fluorine-containing organic monomer to obtain a mixture; (b) and directly placing or injecting the mixture into a porous support material to polymerize in a closed environment at the temperature of 60-100 ℃.

The invention further aims to provide an application of the high-voltage-resistant solid polymer electrolyte, a positive electrode and a negative electrode are assembled into a lithium battery, the positive electrode adopts lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium cobalt phosphate or lithium nickel phosphate, and the negative electrode is lithium metal.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages: the high-voltage-resistant solid polymer electrolyte is polymerized by using the fluorine-containing cyclic or unsaturated chain organic monomer and is combined with the lithium salt, so that the high-voltage-resistant solid polymer electrolyte still has strong oxidation resistance under the high-voltage condition, can avoid oxidative decomposition when being applied to the circulation of a high-voltage solid polymer battery, and further realizes long-term stable circulation; the solid polymer electrolyte has higher room temperature ionic conductivity, and the interface between an electrode and the solid electrolyte in the solid battery is improved by adopting an in-situ polymerization method, so that the charge and discharge capacity of the battery is further improved; the solid polymer electrolyte filled with the porous support material has excellent mechanical properties, is beneficial to inhibiting the generation of lithium dendrites in the repeated charging and discharging process of the lithium metal battery, avoids potential safety hazards caused by short circuit of the battery, and obviously improves the safety performance of the lithium metal battery. The energy density of the solid polymer battery is further improved by matching the solid polymer electrolyte with the high-voltage anode material.

Drawings

FIG. 1 is a force-deformation curve of a solid polymer electrolyte provided in example 2;

FIG. 2 is a plot of the voltage windows for the solid polymer electrolyte provided in example 2 and a comparative electrolyte;

FIG. 3 is a comparison of ionic conductivities at different temperatures for the solid polymer electrolyte provided in example 2 and the comparative example electrolyte;

FIG. 4 is a graph showing the cycle performance at 0.1C of a solid polymer battery assembled with the solid polymer electrolyte provided in example 2 and the comparative example electrolyte;

fig. 5 is rate performance and cycle performance at 0.5C of a solid polymer battery assembled with the solid polymer electrolyte provided in example 2;

fig. 6 is a first charge curve of a solid-state polymer battery of the solid-state polymer electrolyte assembly provided in example 10 and a solid-state battery of the comparative example solid-state electrolyte assembly;

fig. 7 is a first charge-discharge curve of a solid polymer battery assembled with the solid polymer electrolyte provided in example 10;

fig. 8 shows cycle performance at 0.2C and 1C of a solid polymer battery assembled with the solid polymer electrolyte provided in example 10.

Detailed Description

The high-voltage-resistant solid polymer electrolyte comprises a polymer matrix and a lithium salt contained in the polymer matrix, and is characterized in that: the polymer matrix is prepared by carrying out polymerization reaction on a fluorine-containing organic monomer under the action of a catalyst, wherein the fluorine-containing organic monomer is a fluorine-containing cyclic or unsaturated chain organic monomer. By using fluorine-containing cyclic or unsaturated chain organic monomers for polymerization and combining lithium salt, the high-voltage solid polymer battery has strong oxidation resistance under the high-voltage condition, can avoid oxidative decomposition when applied to the circulation of the high-voltage solid polymer battery, and realizes long-term stable circulation; the solid polymer electrolyte has higher room temperature ionic conductivity, and the interface between an electrode and the solid electrolyte in the solid battery is improved by adopting an in-situ polymerization method, so that the charge and discharge capacity of the battery is further improved; the solid polymer electrolyte filled with the porous support material has excellent mechanical properties, is beneficial to inhibiting the generation of lithium dendrites in the repeated charging and discharging process of the lithium metal battery, avoids potential safety hazards caused by short circuit of the battery, and obviously improves the safety performance of the lithium metal battery. The energy density of the solid polymer battery is further improved by matching the solid polymer electrolyte with the high-voltage anode material.

The fluorine-containing organic monomer may be one or more selected from fluoroethylene carbonate (FEC), perfluoro-1, 2-dimethylcyclohexane, perfluoro-1, 3-dimethylcyclohexane, ethyl 4, 4-difluorocyclohexanecarboxylate, 2,3, 3-tetrafluoropropyl methacrylate, and 3- (perfluoro-n-octyl) -1, 2-epoxypropane. The lithium salts are conventional ones, such as those selected from lithium hexafluorophosphate (LiPF)₆) Lithium tetrafluoroborate, lithium perchlorate, lithium bis (oxalato) borate, lithium difluoro (oxalato) borate (LiDFOB), lithium bis (trifluoromethanesulfonyl) imide and lithium bis (fluorosulfonyl) imide. The catalyst needs to be compatible with the above-mentioned fluorine-containing organic monomer, and is typically a mixture of one or more selected from stannous isooctanoate, dibutyltin dilaurate, triethylenediamine, dimethylcyclohexylamine, and dimethylaminoethoxyethanol. The high-voltage-resistant solid polymer electrolyte comprises the following raw material components in percentage by mass: 65-90% of fluorine-containing organic monomer, 9.9-30% of lithium salt and 0.1-5% of catalyst. The preferred situation in the present invention is: the fluorine-containing polymer is poly-fluoro ethylene carbonate (namely organic monomer is FEC), and the mass fraction of the fluorine-containing polymer is 75-85%; the lithium salt is LiDFOB or LiPF₆The mass fraction is 15-25%; the catalyst is stannous isooctanoate, and the mass fraction of the catalyst is 1-3%.

The above-mentioned high-voltage resistant solid state polymerizationThe polyelectrolyte injects the mixture formed by the fluorine-containing organic monomer, lithium salt and catalyst into the porous supporting material to carry out polymerization reaction; the porous supporting material is a polyethylene microporous membrane, a polypropylene microporous membrane, a cellulose non-woven membrane, a polyimide non-woven membrane or a glass fiber membrane. The solid polymer electrolyte has excellent mechanical properties: the electrochemical stability window is more than or equal to 6.3V, and the ionic conductivity is 6.5 multiplied by 10^-5～2.5×10^-4S·cm^-1The mechanical strength can reach 2.3 GPa.

The preparation method of the high-voltage-resistant solid polymer electrolyte comprises the following steps: (a) dissolving lithium salt and a catalyst in a fluorine-containing organic monomer to obtain a mixture; (b) and directly placing or injecting the mixture into a porous support material to polymerize in a closed environment (usually 30-60 hours) at the temperature of 60-100 ℃.

In the application of the high-voltage-resistant solid polymer electrolyte, the positive electrode and the negative electrode are assembled into the lithium battery, and the positive electrode adopts lithium nickel manganese oxide (LiNi)_0.5Mn_1.5O₄) Lithium nickel cobalt manganese oxide (LiNi)_1/ ₃Co_1/3Mn_1/3O₄) Lithium cobaltate (LiCoO)₂) Lithium cobalt phosphate (LiCoPO)₄) Or lithium nickel phosphate (LiNiPO)₄) The negative electrode is lithium metal; the method specifically comprises the following steps: (1) preparing a high-voltage electrode material: 90mg of LiCoO was taken₂Or LiNi_0.5Mn_1.5O₄Mixing the high-voltage positive electrode material with 5mg of acetylene black, adding the mixture into 0.5mL of NMP, and stirring the mixture at room temperature at the speed of 400rpm for 2 hours; then adding 5mg of polyvinylidene fluoride binder (PVDF), and stirring at the speed of 400rpm for 2h to obtain prepared slurry; uniformly coating the slurry on an aluminum foil, drying at 80 ℃ for 12 hours, cutting into pole pieces with the diameter of 12mm, and putting into a glove box for later use; (2) sequentially placing prepared LiCoO on the positive shell of the button cell₂Or LiNi_0.5Mn_1.5O₄An electrode, a porous support material containing liquid electrolyte solution (namely the mixture), a metal lithium cathode, a gasket, an elastic sheet and a cathode shell are assembled into a button cell in a glove box; (3) assembled buckle type electric powerThe cell is maintained in an environment of 80 ℃ for 48 hours, so that the liquid electrolyte is fully polymerized.

The present invention will be further illustrated with reference to the following examples.

Example 1

The embodiment provides a high-voltage-resistant solid polymer electrolyte and an application thereof, which specifically include the following:

(1) preparation of high Voltage LiCoO₂An electrode: 90mg of LiCoO was taken₂Mixing the high-voltage positive electrode material with 5mg of acetylene black, adding the mixture into 0.5mL of NMP, and stirring the mixture at room temperature at the speed of 400rpm for 2 hours; subsequently, 5mg of polyvinylidene fluoride binder (PVDF) was added, followed by stirring at 400rpm for 2 hours to obtain a prepared slurry. Uniformly coating the slurry on an aluminum foil, drying at 80 ℃ for 12 hours, cutting into pole pieces with the diameter of 12mm, and putting into a glove box for later use;

(2) 3mg of LiDFOB and 0.03mg of stannous isooctanoate are dissolved in 27mg of FEC, and the mixture is injected into a cellulose non-woven membrane with the diameter of 16mm after being fully and uniformly mixed; then sequentially putting the prepared LiCoO on the positive electrode shell of the button cell₂The button cell comprises an electrode, a cellulose non-woven membrane, a lithium metal cathode, a gasket, an elastic sheet and a cathode shell, which are assembled into a button cell in a glove box;

(3) and (3) maintaining the assembled button cell in an environment of 80 ℃ for 48 hours to ensure that the liquid electrolyte is fully polymerized.

Example 2

This example provides a high voltage resistant solid polymer electrolyte and its use, which is essentially the same as in example 1, except that: in step (2), 4.5mg of LiDFOB and 0.3mg of stannous isooctanoate were dissolved in 25.2mg of FEC, and the mixture was mixed well and injected into a cellulose nonwoven film having a diameter of 16mm (see FIGS. 1 to 5 for specific properties).

Example 3

This example provides a high voltage resistant solid polymer electrolyte and its use, which is essentially the same as in example 1, except that: in step (2), 6mg of LiDFOB and 1.5mg of stannous isooctanoate were dissolved in 22.5mg of FEC, and the resulting solution was mixed well and injected into a cellulose nonwoven film having a diameter of 16 mm.

Example 4

This example provides a high voltage resistant solid polymer electrolyte and its use, which is essentially the same as in example 1, except that: in step (2), 7.5mg of LiDFOB and 0.3mg of stannous isooctanoate were dissolved in 22.2mg of FEC, and the mixture was thoroughly and uniformly mixed and injected into a cellulose nonwoven film having a diameter of 16 mm.

Example 5

This example provides a high voltage resistant solid polymer electrolyte and its use, which is essentially the same as in example 1, except that: in the step (2), 4.5mg of LiDFOB and 0.3mg of stannous isooctanoate were dissolved in 25.2mg of perfluoro-1, 2-dimethylcyclohexane, and the solution was mixed well and injected into a cellulose nonwoven membrane having a diameter of 16 mm.

Example 6

This example provides a high voltage resistant solid polymer electrolyte and its use, which is essentially the same as in example 1, except that: in the step (2), 4.5mg of LiDFOB and 0.3mg of stannous isooctanoate were dissolved in 25.2mg of perfluoro-1, 3-dimethylcyclohexane, and the solution was mixed well and injected into a cellulose nonwoven membrane having a diameter of 16 mm.

Example 7

This example provides a high voltage resistant solid polymer electrolyte and its use, which is essentially the same as in example 1, except that: in the step (2), 4.5mg of LiDFOB and 0.3mg of stannous isooctanoate were dissolved in 25.2mg of ethyl 4, 4-difluorocyclohexanecarboxylate, and the resulting solution was mixed well and injected into a cellulose nonwoven film having a diameter of 16 mm.

Example 8

This example provides a high voltage resistant solid polymer electrolyte and its use, which is essentially the same as in example 1, except that: in the step (2), 4.5mg of LiDFOB and 0.3mg of stannous isooctanoate were dissolved in 25.2mg of 2,2,3, 3-tetrafluoropropyl methacrylate, and the resulting solution was mixed well and injected into a cellulose nonwoven film having a diameter of 16 mm.

Example 9

This example provides a high voltage resistant solid polymer electrolyte and its use, which is essentially the same as in example 1, except that: in the step (2), 4.5mg of LiDFOB and 0.3mg of stannous isooctanoate were dissolved in 25.2mg of 3- (perfluoro-n-octyl) -1, 2-epoxypropane, and the resulting solution was mixed well and injected into a cellulose nonwoven membrane having a diameter of 16 mm.

Example 10

This example provides a high voltage resistant solid polymer electrolyte and its use, which is substantially the same as that of example 2 except that LiNi was used in the step (1)_0.5Mn_1.5O₄The positive electrode is specifically prepared by the following steps: 90mg of LiNi was taken_0.5Mn_1.5O₄Mixing the high-voltage positive electrode material with 5mg of acetylene black, adding the mixture into 0.5mL of NMP, and stirring the mixture at room temperature at the speed of 400rpm for 2 hours; subsequently, 5mg of polyvinylidene fluoride binder (PVDF) was added, followed by stirring at 400rpm for 2 hours to obtain a prepared slurry. The slurry was uniformly coated on aluminum foil, dried at 80 ℃ for 12 hours, cut into 12mm diameter pole pieces, and placed into a glove box for use (see fig. 6-8 for specific properties).

Comparative example

The embodiment provides a polymer electrolyte and an application thereof, and the polymer electrolyte comprises the following components in part by weight: dissolving polyethylene oxide (PEO) and LiDFOB in anhydrous acetonitrile according to the molar ratio of O to Li being 8:1, fully and uniformly stirring, and injecting into a cellulose non-woven membrane; after the acetonitrile is fully volatilized, the acetonitrile is cut into circular slices with the diameter of 16mm (the performances such as room temperature ionic conductivity and the like are compared and shown in a table 1).

TABLE 1 examples 1-9, comparative examples solid Polymer electrolyte Voltage Window, Room temperature Ionic conductivity and LiCoO₂Battery 100-cycle capacity retention rate table

In table 1 the cells were subjected to a linear sweep voltammetry test (LSV) by means of an electrochemical workstation and the voltage windows of the different polymer electrolytes were observed. The room temperature ionic conductivity meter is used for testing the impedance of the battery through an electrochemical workstation, the ionic conductivity at room temperature is calculated by adopting the formula sigma d/RS, wherein sigma is the ionic conductivity of the electrolyte, d is the thickness of the electrolyte in the battery,r is the electrolyte resistance and S is the area of the electrolyte. By testing LiCoO based on different solid polymer electrolytes₂The retention rate of the battery with respect to the initial capacity after 100 cycles of the battery was observed with respect to the cycle at 0.5C rate.

Fig. 1 shows the force-deformation curve of a high voltage resistant solid polymer electrolyte prepared according to example 2, with a modulus of up to 2.3GPa, with high mechanical strength. Fig. 2 shows that the solid polymer electrolyte prepared according to example 2 has an electrochemical stability window of 0-6.3V, whereas the polyethylene oxide solid electrolyte of the comparative example has only an electrochemical stability window of a lower range. Fig. 3 shows that the ionic conductivity of the solid polymer electrolyte prepared according to example 2 was significantly higher than that of the comparative example electrolyte at different temperatures.

FIG. 4 shows LiCoO assembled from two electrolytes (example 2 and comparative example)₂The cycle performance of the solid-state battery is compared under the multiplying power of 0.1C, the extremely high charge-discharge specific capacity is shown, and the charge-discharge capacity of the comparative battery is rapidly attenuated. FIG. 5 is LiCoO assembled from the solid electrolyte of example 2₂Rate capability of solid-state batteries and long-term stable cycling at 0.5C rate. FIGS. 6 and 7 are LiNi based on a comparative example solid electrolyte and the solid electrolyte of example 5, respectively_0.5Mn_1.5O₄The first charge-discharge curve of the solid-state battery shows the decomposition of the comparative example solid-state electrolyte at a voltage of 4.7V and the high voltage stability of the example 5 solid-state polymer electrolyte. FIG. 8 shows LiNi based on a solid polymer electrolyte provided in example 5_0.5Mn_1.5O₄The cycling performance of the solid-state battery at 0.2C and 1C shows the long-term stability performance of the solid-state polymer electrolyte of the present invention at high voltage.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-voltage-resistant solid polymer electrolyte, which is composed of a polymer matrix and a lithium salt contained in the polymer matrix, characterized in that: the polymer matrix is a fluorine-containing organic monomer in a catalyst. It is prepared by carrying out a polymerization reaction under the action of Cyclohexane, ethyl 4,4-difluorocyclohexylcarboxylate, 2,2,3,3-tetrafluoropropyl methacrylate and 3-(perfluoro-n-octyl)-1,2-epoxypropane one or more of;

The high-voltage-resistant solid polymer electrolyte includes the following raw material components by mass percentage:

Fluorine-containing organic monomer 65~90%;

Lithium salt 9.9~30%;

Catalyst 0.1%~5%;

The lithium salt is one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium bis-oxalate borate, lithium difluorooxalate borate, lithium bis-trifluoromethanesulfonimide and lithium bis-fluorosulfonimide. A mixture of one or more compositions; the catalyst is one or more selected from stannous isooctanoate, dibutyltin dilaurate, triethylenediamine, dimethylcyclohexylamine and dimethylaminoethoxyethanol a mixture of species.

2 . The high-voltage-resistant solid polymer electrolyte according to claim 1 , wherein the mixture formed by the fluorine-containing organic monomer, the lithium salt and the catalyst is injected into the porous support material to carry out the polymerization reaction. 3 .

3. The high-voltage-resistant solid polymer electrolyte according to claim 2, wherein the electrochemical stability window of the high-voltage-resistant solid polymer electrolyte is greater than or equal to 6.3V and the ionic conductivity is 6.5 × ^10-5 ~ 2.5 × 10 ^-4 S·cm ^-1 .

4. The high-voltage-resistant solid polymer electrolyte according to claim 2, wherein the porous support material is polyethylene microporous membrane, polypropylene microporous membrane, cellulose nonwoven membrane, polyimide Non-woven membrane or fiberglass membrane.

5. the preparation method of the high-voltage-resistant solid polymer electrolyte described in any one of claim 1 to 4, is characterized in that, it comprises the following steps:

(a) A mixture obtained by dissolving a lithium salt and a catalyst in a fluorine-containing organic monomer;

(b) The mixture can be directly placed or injected into a porous support material to perform polymerization in a closed environment at 60-100°C.

6. The application of the high-voltage-resistant solid polymer electrolyte according to any one of claims 1 to 4, wherein the high-voltage-resistant solid polymer electrolyte is assembled into a lithium battery with a positive electrode and a negative electrode, and the positive electrode is assembled into a lithium battery. Lithium nickel manganese oxide, lithium nickel cobalt manganate, lithium cobalt oxide, lithium cobalt phosphate or lithium nickel phosphate are used, and the negative electrode is lithium metal.