RU2457587C1 - Polymer electrolyte gel for lithium-ion battery - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: base of the polymer electrolyte gel used is a dispersion of a vinyl acetate and acrylate copolymer in organic solvents, with the following ratio of components of the mixture (wt % of dry substance): anhydrous ionic inorganic lithium salt 15-30, anhydrous organic solvent 30-40, vinyl acetate/acrylate copolymer 30-55, wherein the obtained electrolyte has moisture content less than 0.003%.

EFFECT: high adhesion capacity, elasticity, low environmental risk and low production cost.

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Description

The invention relates to the field of production of electrolytes for lithium-ion batteries (LIA).

In the production of lithium-ion batteries, liquid electrolytes based on aprotic dipolar solvents (ADRs), such as dimethyl carbonate (DMC), diethyl carbonate (DEC) and ethylene carbonate (EC), are mainly used [1].

The disadvantages of these electrolytes is the need to use mainly metal cases because of the need to exclude the flow of liquid electrolyte.

Currently, polymer electrolytes are widely used in the production of lithium-ion batteries [2]. The polymers used for the production of electrolytes are capable of incorporating lithium salts into their composition, which is due to the use of such materials in lithium current sources.

Due to their plasticity, polymer electrolytes make it possible to produce lithium-ion batteries with a developed surface and any shape, which significantly increases the manufacturability of production and overall dimensions.

Polymer electrolytes include several large groups that differ in their component composition and properties. The most common are gel electrolytes. They are a spatial network formed by macromolecules or their aggregates, in which a salt solution is distributed in an aprotic dipolar solvent (ADR). Gel-polymer electrolytes have a sufficiently high conductivity, comparable with the conductivity of liquid non-aqueous electrolytes (from 10 ^-3 to 10 ^-4 Ohm ^-1 · cm ^-1 ) and satisfactory mechanical properties.

Various polymers are used as the basis of the gel polymer electrolyte, for example, in the patent [3], polyether urethane diacrylates and crown ethers with a nonaqueous solution of lithium salt were used.

There is no data in the literature on the use of aqueous dispersions of acrylate latexes and their copolymers as a raw material for the production of gel electrolytes. But, it is known that aqueous and non-aqueous [1] solutions of various polymers are used as a binding component of the electrodes of a lithium-ion battery. A known electrode for LIA using as an aqueous binder a solution of polyacrylate [4, 5], aqueous solutions of styrene butadiene latex (SBR latex), nitrile butadiene rubber latex (NBR latex) and methacrylate butadiene rubber latex (MBR latex) [6], aqueous dispersions of a copolymer of butadiene and methyl methacrylate [7].

The salts used for the preparation of electrolytes are mainly [1, 8] lithium hexafluorophosphate (LiPF ₆ ), lithium hexafluoroarsenate (LiAsF ₆ ), lithium perchlorate (LiClO ₄ ), lithium bis (trifluoromethanesulfonyl) imide (LiN (CF ₃ SO ₂ ) ₂ ) and lithium trifluorosulfonate (LiCF ₃ SO ₃ ), or other lithium salts, or salts of another alkali metal, or a mixture thereof.

As a solvent for the preparation of electrolytes, one solvent or a mixture thereof is used [1, 8] from the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl propyl propionate, ethyl propyl propionate, methyl acetate, ethyl acetate, ethyl acetate, ethyl acetate, ethyl acetate, ethyl acetate, ethyl acetate, ethyl acetate, ethyl acetate, ethyl acetate , 3-dioxalan, diglyme (2-methoxyethyl ether), tetraglim, ethylene carbonate, propylene carbonate, γ-butyrolactone, sulfolane.

The patent [9] describes a solid lithium-conducting electrolyte containing a polyacrylonitrile-based polymer matrix and an inorganic ionic lithium salt. Polyacrylonitrite of average molecular weight (0.5-1.2) · 10 ⁵ containing more than 90 wt.% Units of acrylonitrile, in which acrylate or methacrylate units, as well as carboxylic acid units, in the following ratios of components (mol.%): copolymer of polyacrylonitrile 83.3-66.7, ionogenic inorganic lithium salt 16.7-33.3. This electrolyte has a conductivity of at least 10 ^-4 Ohm ^-1 · cm ^-1 at room temperature.

Closest to the claimed invention is a gel-polymer electrolyte, a method for which is described in [10]. The polymer gel electrolyte contains an electrolytic salt solution and a polymer capable of gelation in an electrolytic salt solution. In this case, the polymer gel electrolyte contains from 20 to 60 wt.% Polymer and from 80 to 40 wt.% Electrolytic salt solution. The polymer is a polymer mixture consisting of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) in an amount of from 40 to 95 wt.% And polymethylmethacrylate (PMMA) in an amount of from 60 to 5 wt.%. The solvent for the electrolytic salt solution is ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, N-methylpyrrolidone or γ-butyrolactone, or a two-component or three-component mixture thereof. As the electrolytic salt for the electrolytic salt solution, a lithium salt from the group consisting of LiClO ₄ , LiPF ₆ and LiCF ₃ SO _{3 is used} .

The disadvantages of the known gel-polymer electrolyte include low electrical conductivity, high technological production costs, high cost of components.

The invention solves the problem of using new materials for the production of gel polymer electrolyte for a lithium-ion battery, which simplifies the process, reduces production costs, increases the electrochemical characteristics of the battery, increases the adhesive properties and elasticity of the electrolyte.

The technical result of the invention is to increase the adhesive ability, elasticity, reduce environmental risk and reduce production costs.

The specified technical result is achieved by the fact that the gel polymer electrolyte for a lithium-ion battery, consisting of a dispersion of acrylate and its copolymers, and an organic electrolyte with an inorganic lithium salt, take the dispersion of polyacrylate or a copolymer of vinyl acetate and acrylate in organic solvents as the basis for the electrolyte in the following the ratios of the components of the mixture,% (wt. dry. in-va):

Anhydrous ionogenic inorganic lithium salt 15-30 Anhydrous Organic Solvent 30-40 Polyacrylate or vinyl acetate / acrylate: 30-55,

while the humidity of the obtained electrolyte is less than 0.003%.

As the basis of the gel polymer electrolyte, cheap polymers produced by large parties, such as polyacrylate or copolymers of vinyl acetate and acrylate, are used.

The claimed gel-polymer electrolyte provides an expansion of technological capabilities in terms of the use of various methods of preparation of the electrolyte, which helps to reduce the mass of the battery due to the use of flexible polymer cases instead of metal ones. Cost reduction due to the use of commercially available aqueous dispersions of copolymers of polyacrylates with vinyl acetate, which do not require additional operations to prepare a gel polymer electrolyte.

To prepare the gel polymer electrolyte, aqueous dispersions (acrylate latexes) of vinyl acetate and acrylate copolymers of grades K23 and K65 were used. These acrylate latexes were dried at room temperature for 24 hours with further grinding in a knife mixer. Next, drying was carried out for 12 hours at a temperature of 50 ° C in a vacuum oven at a residual pressure of 0.05 MPa. The moisture content determined by the Fisher method did not exceed 50 ppm. Then, dehydrated polyacrylates were introduced into the electrolyte in an amount of 10-50 wt.%: Solutions of inorganic lithium salts LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiPF ₆ in individual solvents or their mixtures: propylene carbonate (PC), dimethoxyethane (DME) were used as the electrolyte , dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylene carbonate (EC). The salt concentration ranged from 0.075 to 1.2 mol / dm ³ .

The resulting gel electrolytes have high flexibility, the active mass of the electrodes does not deteriorate during cycling. The hydrophilic spatial structure formed using the latexes used has high strength and conductivity.

Unlike gel polymer electrolytes based on pure polyacrylates, electrolytes based on copolymers of polyacrylate with vinyl acetate have lower viscosity and higher electrical conductivity at equal component concentrations, due to the higher solubility of the copolymer in non-aqueous electrolytes.

Tests have shown that lithium-ion batteries made using gel-polymer electrolytes based on copolymers of polyacrylate with vinyl acetate have high specific electrochemical characteristics and do not break down after repeated cycling at current densities up to 2C.

Example 1. In an atmosphere of a dry box was placed 24 g of a copolymer of vinyl acetate / acrylate K23 in 0.1 dm ^{3 of} an electrolyte solution of 1 mol / dm ³ LiClO ₄ PC: DME 7: 3. It was kept in an atmosphere of a dry box (atmospheric moisture content below 100 ppm) for 2 hours. It was stirred on an electric mixer, with simultaneous dispersion on an ultrasonic disperser UZDN-A for 5 minutes. Get a gel-polymer electrolyte composition (%, wt. Dry. In-VA):

LiClO ₄ : 15;

Propylene carbonate: 15;

Dimethoxyethane: 25;

Vinyl acetate / acrylate copolymer K23: 45;

Humidity of the obtained electrolyte, less than 0.003%.

Example 2. In an atmosphere of dry boxing was placed 24 g of a copolymer of vinyl acetate / acrylate K65 in 0.1 DM ³ electrolyte solution 1 mol / DM ³ LiClO ₄ PC: DME 7: 3. It was kept in a dry box atmosphere (atmospheric moisture content below 100 ppm) for 2 hours. It was mixed on an electric mixer, with simultaneous dispersion on an ultrasonic disperser UZDN-A for 5 minutes. Get a gel-polymer electrolyte composition (%, wt. Dry. In-VA):

LiClO ₄ : 15;

Propylene carbonate: 15;

Dimethoxyethane: 25;

Vinyl acetate / acrylate copolymer K65: 45;

Humidity of the obtained electrolyte, less than 0.003%.

Example 3. In an atmosphere of a dry box was placed 24 g of vinyl acetate / acrylate K23 in 0.1 DM ³ electrolyte solution of 1 mol / DM ³ LiClO ₄ PC. It was kept in a dry box atmosphere (atmospheric moisture content below 100 ppm) for 2 hours. It was mixed on an electric mixer, with simultaneous dispersion on an ultrasonic disperser UZDN-A for 5 minutes. Get a gel-polymer electrolyte composition (%, wt. Dry. In-VA):

LiClO ₄ : 15;

Propylene carbonate: 40;

Vinyl acetate / acrylate copolymer K23: 45;

The moisture content of the obtained electrolyte is less than 0.003%.

Example 4. In an atmosphere of a dry box was placed 24 g of vinyl acetate / acrylate K65 in 0.1 DM ³ electrolyte solution of 1 mol / DM ³ LiPF ₆ in EC: DEK 1: 1 (vol.). It was kept in a dry box atmosphere (atmospheric moisture content below 100 ppm) for 2 hours. It was mixed on an electric mixer, with simultaneous dispersion on an ultrasonic disperser UZDN-A for 5 minutes. Get a gel-polymer electrolyte composition (%, wt. Dry. In-VA):

LiPF ₆ : 18;

Ethylene Carbonate: 16;

Diethyl carbonate: 19;

Vinyl acetate / acrylate copolymer K65: 45;

Humidity of the obtained electrolyte, less than 0.003%.

Example 5. In an atmosphere of dry boxing was placed 24 g of a copolymer of vinyl acetate / acrylate K23 in 0.1 DM ³ electrolyte solution of 1 mol / DM ³ LiPF ₆ in EC: DEK 1: 1 (vol.). It was kept in a dry box atmosphere (atmospheric moisture content below 100 ppm) for 2 hours. It was mixed on an electric mixer, with simultaneous dispersion on an ultrasonic disperser UZDN-A for 5 minutes. Get a gel-polymer electrolyte composition (%, wt. Dry. In-VA):

LiPF ₆ : 18;

Ethylene Carbonate: 16;

Diethyl carbonate: 19;

Vinyl acetate / acrylate copolymer K23: 45;

Humidity of the obtained electrolyte, less than 0.003%.

The electrical conductivity of the obtained gel polymer electrolytes was, depending on the composition, from 4.2 · 10 ^-4 to 1.2 · 10 ^-3 Ohm ^-1 · cm ^-1 . The electrical conductivity of gel electrolytes increases almost linearly with increasing temperature in the range from minus 30 to plus 80 ° C, while the temperature coefficient of electrical conductivity is, depending on the electrolyte composition, from 3.4 to 5.5 S / (cm · K).

The use of gel-polymer electrolytes based on copolymers of vinyl acetate and acrylate can increase the specific discharge capacity of LIA, simplify the process by reducing the number of operations and equipment for its implementation, reduce environmental risk and reduce explosion safety and cost of production. The proposed gel-polymer electrolytes make it possible to produce lithium-ion batteries with reproducible high specific electrochemical characteristics; it is also applicable for the manufacture of other primary and secondary ChIT.

Information sources

1. I.A. Kedrinsky, V.G. Yakovlev. Li-ion batteries. Krasnoyarsk .: IPK "Platinum". 2002.266 s.

2. Bushkova OV Structuring and electrical transport in amorphous solid polymer electrolytes [Electronic resource]: dis. ... Dr. chem. Sciences: 02.00.04. - M .: RSL, 2006. - (From the collections of the Russian State Library).

3. A liquid polymerization-capable composition for producing solid electrolytes and a method for curing it. RF patent 2356131. IPC H01M 6/18. Claim 2007.10.15. Publ. 2009.05.20.

4. Positive Electrode For Lithium Secondary Battery, And Nona aqueous Lithium Secondary Battery. Japan patent. JP 2008123824. H01M 4/62; H01M 4/02; H01M 4/04; H01M 4/48; H01M 10/40; H01M 4/62; H01M 4/02; H01M 4/04; H01M 4/48; H01M 10/36. Claim 2006.11.10. Publ. 2008.05.29.

5. Anode For Lithium Battery And Lithium Battery Employing The Same. U.S. Patent. US2008166633 H01M 4/62; H01M 4/62; H01M 4 / 62B; H01M 4 / 04C4; H01M 4/1393; H01M4 / 1395. Claim 2007.01.05. Publ. 2008.07.10.

6. Aqueous Phenolic Resin Composition And Binder. Japan patent. C08L 61/10; C08G 8/00; C08G 8/10; C08L 21/02; C09J109 / 04; C09J109 / 08; C09J 109/10; C09J 161/10; C08L 61/00; C08G 8/00; C08L 21/00; C09J109 / 00; C09J 161/00. Claim 2006.02.02. Publ. 08/08/16.

7. A method of manufacturing electrodes of an electric battery. RF patent 2071621. MKI 6 H01M 4/26, H01M 4/62, H01M 10/28. Claim 1994.11.29. Publ. 1997.01.10.

8. Electrolyte and chemical source of electrical energy. RF patent 2007131385. IPC H01M 4 / 40.3 decl. 2006.01.11. Publ. 2009.02.27.

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Claims (1)

A gel-polymer electrolyte for a lithium-ion battery, consisting of a dispersion of a copolymer of acrylate and vinyl acetate and an organic electrolyte with an inorganic lithium salt, characterized in that the dispersion of a polyacrylate or a copolymer of vinyl acetate and acrylate in organic solvents is taken as the electrolyte base with the following ratios of the components of the mixture, % (mass. dry matter):
Anhydrous ionogenic inorganic lithium salt 15-30 Anhydrous Organic Solvent 30-40 Vinyl Acetate / Acrylate Copolymer 30-55