CN117327460A - Adhesive, pole piece, electrolyte membrane for lithium ion battery and preparation method - Google Patents

Adhesive, pole piece, electrolyte membrane for lithium ion battery and preparation method Download PDF

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Publication number
CN117327460A
CN117327460A CN202311632701.2A CN202311632701A CN117327460A CN 117327460 A CN117327460 A CN 117327460A CN 202311632701 A CN202311632701 A CN 202311632701A CN 117327460 A CN117327460 A CN 117327460A
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lithium
lithium ion
ion battery
binder
ethylene
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朱高龙
陈宁
刘青青
张庭菽
廖雪梅
吕星瑶
王建
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Sichuan New Energy Vehicle Innovation Center Co Ltd
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Sichuan New Energy Vehicle Innovation Center Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J123/00—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers
    • C09J123/02—Adhesives based on homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Adhesives based on derivatives of such polymers not modified by chemical after-treatment
    • C09J123/04—Homopolymers or copolymers of ethene
    • C09J123/08—Copolymers of ethene
    • C09J123/0846—Copolymers of ethene with unsaturated hydrocarbons containing other atoms than carbon or hydrogen atoms
    • C09J123/0869—Acids or derivatives thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
    • H01M10/0562—Solid materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Chemical & Material Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Inorganic Chemistry (AREA)
  • Organic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention relates to a binder, a pole piece, an electrolyte membrane and a preparation method for a lithium ion battery, and relates to the technical field of lithium ion batteries, wherein the binder comprises an ethylene acrylic ester copolymer, and the content of ester groups in the ethylene acrylic ester copolymer is less than 30% by weight of the ethylene acrylic ester copolymer. The invention ensures that the adhesive has high adhesive force by adjusting the content of ester groups in the ethylene acrylic ester copolymer to be less than 30 weight percent, meets the requirements of preparing battery pole pieces and electrolyte membranes, and can be dissolved in a low-polarity solvent compatible with sulfide solid electrolyte, thereby avoiding adverse effects of the solvent on the performance of the sulfide electrolyte. The ethylene acrylic ester copolymer added with the lithium salt has good lithium ion conduction capability, avoids the situation that the adhesive is coated on the surfaces of the active substances and the solid electrolyte to reduce the lithium conduction capability, and effectively solves the technical difficulty that the performance of the lithium ion battery is deteriorated by using the adhesive.

Description

Adhesive, pole piece, electrolyte membrane for lithium ion battery and preparation method
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a binder, a pole piece, an electrolyte membrane and a preparation method for the lithium ion battery.
Background
Because of the characteristics of higher energy density, low memory effect and the like of the lithium ion battery, the lithium ion battery has been widely applied to the fields of electric automobiles, electronic products, energy storage and the like, but because of the adoption of flammable and easily leaked electrolyte, the existing lithium ion battery has hidden danger of combustion and explosion, and the safety is further required to be improved. In addition, the liquid battery cannot be matched with the high-voltage positive electrode temporarily and the negative electrode with high energy density can be well applied, so that the energy density of the battery cannot be further improved. Therefore, the solid electrolyte with high safety characteristic is used as a substitute for inflammable electrolyte, and is an effective strategy for improving the safety of the battery for current scientific researchers and battery industry.
At present, sulfide-based solid state electrolytes are distinguished by their advantages of high ionic conductivity, good flexibility, and the like. The preparation of the anode and the cathode of the sulfide all-solid-state battery and the electrolyte membrane mainly comprises two main routes: dry and wet methods. The dry process can prepare positive and negative electrodes with high load mainly by a mixing high-pressure pressing mode, but an electrolyte membrane with ideal thickness is difficult to prepare, and the equipment of the current dry process is in a development stage. The wet process mainly adopts a slurry mixing coating mode, the components are dispersed more uniformly by wet mixing, and the diaphragm with proper thickness can be prepared by adjusting the scraper seam. In addition, wet processes are highly compatible with existing liquid process equipment and therefore have industrialization potential.
The wet process needs to disperse sulfide electrolyte, binder, conductive agent and active substance in solvent, the compatibility of the solvent and sulfide electrolyte is important, the solvent with good compatibility with sulfide electrolyte can ensure that the prepared electrolyte membrane has high ionic conductivity, and the prepared pole piece has high specific capacity. The binder is a key material in the wet process, and needs to have high adhesion to adhere the sulfide electrolyte to the current collector as a film, and to adhere the electrode active material, the conductive agent, and the sulfide electrolyte to the current collector. If the binder contains a certain amount of polar oxygen-containing functional groups, the adhesion of the binder is greatly improved; however, with the increase of the oxygen-containing functional group, the binder is not soluble in a low polarity solvent such as toluene, xylene, n-hexane, n-heptane, etc. which has good compatibility with sulfide electrolyte. The non-lithium conductive binder used also has a coating effect on the sulfide electrolyte, and reduces the lithium ion conductivity of the sulfide electrolyte. In view of the above, the invention provides an adhesive, a pole piece, an electrolyte membrane and a preparation method for the lithium ion battery.
Disclosure of Invention
The technical problems to be solved by the invention are as follows: when preparing the sulfide-based all-solid-state battery, there are problems that the viscosity of the binder is insufficient and the sulfide electrolyte is coated, so that the performance of the prepared electrode active material is not fully exerted; the invention provides an adhesive, a pole piece, an electrolyte membrane for a lithium ion battery and a preparation method thereof.
In order to solve the technical problem, a first aspect of the present invention provides a binder for a lithium ion battery, the binder for a lithium ion battery comprising an ethylene acrylate copolymer, wherein the ratio of the weight of ester groups in the ethylene acrylate copolymer to the weight of the ethylene acrylate copolymer is less than 30%.
The beneficial effects of the invention are as follows: the content of ester groups in the ethylene acrylic ester copolymer is regulated to be less than 30 and wt%, so that the adhesive has high adhesive force, the requirements for preparing the battery pole piece and the electrolyte membrane are met, and the adhesive can be dissolved in a low-polarity solvent compatible with sulfide solid electrolyte, thereby avoiding adverse effects of the solvent on the performance of the sulfide electrolyte.
On the basis of the technical scheme, the invention can be improved as follows.
Further, the binder for a lithium ion battery further includes a lithium salt.
The beneficial effects of adopting the further scheme are as follows: according to the invention, the oxygen of the ester group in the ethylene acrylic ester copolymer with high polarity can coordinate with lithium ions in the lithium salt, so that the lithium salt can be easily dissociated, and meanwhile, the chain segment of the ethylene acrylic ester copolymer can move, so that the ethylene acrylic ester copolymer added with the lithium salt has good lithium ion conduction capability, thereby enabling the binder to have lithium conduction capability, avoiding the binder from being coated on the surfaces of active substances and solid electrolyte to reduce the lithium conduction capability, and effectively solving the technical difficulty that the performance of a lithium ion battery is deteriorated by using the binder.
Further, the binder for lithium ion batteries satisfies at least one of the following conditions:
A. the weight of ester groups in the ethylene acrylic ester copolymer is 1-30% of the weight of the ethylene acrylic ester copolymer;
B. the ethylene acrylic ester copolymer comprises any one or a combination of at least two of ethylene methyl acrylate, ethylene ethyl acrylate and ethylene butyl acrylate;
C. the lithium salt comprises any one or a combination of at least two of lithium bis (trifluoromethanesulfonyl imide), lithium bis (fluorosulfonyl imide), lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium trifluoromethanesulfonate, lithium difluorooxalato borate, lithium hexafluoroarsenate and lithium difluorophosphate;
D. the weight ratio of the lithium salt to the ethylene acrylate copolymer is 0.01% -300%.
The beneficial effects of adopting the further scheme are as follows: the content of ester groups in the ethylene acrylic acid ester copolymer is regulated to be 1-30% of the weight of the ethylene acrylic acid ester copolymer, so that the lithium-guiding adhesive has better adhesive force and better lithium-guiding performance after the lithium-guiding adhesive reacts with lithium salt; the lithium salt has higher ionic conductivity and battery performance; the lithium salt accounts for 0.01 to 300 percent of the weight of the ethylene acrylic ester copolymer, so that the battery has better battery performance;
the second aspect of the invention provides a pole piece for a lithium ion battery, wherein the pole piece comprises the binder for the lithium ion battery.
The beneficial effects of adopting above-mentioned scheme are: the pole piece for the lithium ion battery has good lithium ion conduction capability.
The third aspect of the invention provides a method for preparing a pole piece for a lithium ion battery, comprising the following steps:
uniformly mixing the binder for the lithium ion battery with an active substance, a conductive agent, a first solid electrolyte and a first solvent to obtain first slurry;
coating the first slurry on a current collector;
and after the first drying, obtaining the pole piece for the lithium ion battery.
The beneficial effects of adopting above-mentioned scheme are: the invention provides a pole piece for a lithium ion battery, which enables the battery to have better battery performance.
Further, the polarity parameter of the first solvent is less than 3.1, and the active material is a positive electrode active material or a negative electrode active material.
The type of the positive electrode active material is not particularly limited, and conventional ternary positive electrode materials, lithium iron phosphate positive electrode materials, etc. may be used, and when the active material is a positive electrode active material, the prepared electrode sheet is a positive electrode sheet. The negative electrode active material is not particularly limited, and conventional graphite negative electrode materials, silicon carbon negative electrode materials, silicon oxygen negative electrode materials, and the like can be used, and when the active material is a negative electrode active material, the prepared electrode sheet is a negative electrode sheet.
Further, the first solvent includes at least one of toluene, xylene, n-hexane, n-heptane, isobutyl isobutyrate, hexyl acetate, and butyl butyrate;
the weight ratio of the binder for the lithium ion battery to the active material, the conductive agent and the first solid electrolyte is (0.5-5) 100 (0.1-20) 5-30;
in the first drying, the drying temperature is 40 ℃ to 200 ℃, for example, 40 ℃, 50 ℃, 80 ℃, 100 ℃, 150 ℃, 180 ℃, 200 ℃ and the like; the drying time is 10min-48h, for example, 10min,1h,2h,4h,6h,8h,10h,12h,24h,48h.
The first solvent is added in an amount sufficient to dissolve the binder ethylene acrylate copolymer. The first solid electrolyte described above includes Li6PS5Cl, li3PS4, and the like.
A fourth aspect of the present invention provides an electrolyte membrane for a lithium ion battery, comprising the binder for a lithium ion battery described in any one of the above.
The beneficial effects of adopting above-mentioned scheme are: the electrolyte membrane for the lithium ion battery has good lithium ion conduction capability.
In a fifth aspect, the present invention provides a method for producing an electrolyte membrane for a lithium ion battery, comprising the steps of:
uniformly mixing the binder for the lithium ion battery, a second solvent and a solid electrolyte to obtain second slurry;
coating the second slurry on a substrate;
and after the second drying, obtaining the electrolyte membrane for the lithium ion battery.
Further, the second solvent includes at least one of toluene, xylene, n-hexane, n-heptane, isobutyl isobutyrate, hexyl acetate, and butyl butyrate;
the weight ratio of the binder for the lithium ion battery to the second solid electrolyte is (0.5-20): 100;
in the second drying, the drying temperature is 40 ℃ to 200 ℃, for example, 40 ℃, 50 ℃, 80 ℃, 100 ℃, 150 ℃, 180 ℃, 200 ℃ and the like; the drying time is 10min-48h, for example, 10min,1h,2h,4h,6h,8h,10h,12h,24h,48h.
The second solvent is added in an amount sufficient to dissolve the binder ethylene acrylate copolymer. The second solid electrolyte described above includes Li6PS5Cl, li3PS4, and the like.
Drawings
FIG. 1 is an EIS chart of example 4 of the present invention and comparative example 1;
FIG. 2 is a graph showing electrochemical performance of example 6 and comparative example 3 of the present invention;
FIG. 3 is a graph showing electrochemical performance of example 5 of the present invention and comparative example 2.
Detailed Description
The principles and features of the present invention are described below with examples given for the purpose of illustration only and are not intended to limit the scope of the invention. The specific techniques or conditions are not identified in the examples and are described in the literature in this field or are carried out in accordance with the product specifications. The reagents or apparatus used were conventional products commercially available through regular channels, with no manufacturer noted.
Example 1
The embodiment relates to a binder for a lithium ion battery, which comprises an ethylene acrylic ester copolymer and lithium salt, wherein the content of ester groups in the ethylene acrylic ester copolymer is less than 30% by weight of the ethylene acrylic ester copolymer.
Wherein the content of ester groups in the ethylene acrylic ester copolymer accounts for 1 percent of the weight of the ethylene acrylic ester copolymer. Preferably, the ethylene acrylate copolymer comprises any one or a combination of at least two of ethylene methyl acrylate, ethylene ethyl acrylate and ethylene butyl acrylate. Preferably, the lithium salt comprises any one or a combination of at least two of lithium bis (trifluoromethanesulfonyl) imide, lithium bis (fluorosulfonyl) imide, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium trifluoromethanesulfonate, lithium difluorooxalato borate, lithium hexafluoroarsenate and lithium difluorophosphate. The content of the lithium salt accounts for 0.01 percent of the weight of the ethylene acrylic ester copolymer.
Example 2
The embodiment relates to a binder for a lithium ion battery, which comprises an ethylene acrylic ester copolymer and lithium salt, wherein the content of ester groups in the ethylene acrylic ester copolymer is less than 30% by weight of the ethylene acrylic ester copolymer.
Wherein the content of ester groups in the ethylene acrylic ester copolymer accounts for 10 percent of the weight of the ethylene acrylic ester copolymer. Preferably, the ethylene acrylate copolymer comprises any one or a combination of at least two of ethylene methyl acrylate, ethylene ethyl acrylate and ethylene butyl acrylate. Preferably, the lithium salt comprises any one or a combination of at least two of lithium bis (trifluoromethanesulfonyl) imide, lithium bis (fluorosulfonyl) imide, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium trifluoromethanesulfonate, lithium difluorooxalato borate, lithium hexafluoroarsenate and lithium difluorophosphate. The lithium salt accounts for 50% of the ethylene acrylic acid ester copolymer by weight.
Example 3
The embodiment relates to a binder for a lithium ion battery, which comprises an ethylene acrylic ester copolymer and lithium salt, wherein the content of ester groups in the ethylene acrylic ester copolymer is less than 30% by weight of the ethylene acrylic ester copolymer.
Wherein the content of ester groups in the ethylene acrylic ester copolymer accounts for 30 percent of the weight of the ethylene acrylic ester copolymer. Preferably, the ethylene acrylate copolymer comprises any one or a combination of at least two of ethylene methyl acrylate, ethylene ethyl acrylate and ethylene butyl acrylate. Preferably, the lithium salt comprises any one or a combination of at least two of lithium bis (trifluoromethanesulfonyl) imide, lithium bis (fluorosulfonyl) imide, lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium trifluoromethanesulfonate, lithium difluorooxalato borate, lithium hexafluoroarsenate and lithium difluorophosphate. The content of the lithium salt accounts for 300 percent of the weight of the ethylene acrylic ester copolymer.
Example 4: application in electrolyte membranes
The embodiment relates to an electrolyte membrane, which is mainly prepared by the following steps: 0.2g of ethylene methyl acrylate (wherein the content of ester groups accounts for 1 percent of the weight of the ethylene acrylic ester copolymer) is copolymerized, 0.1g of lithium bis (fluorosulfonyl) imide is added into 3.7g of dimethylbenzene and isobutyl isobutyrate mixed solvent (the volume ratio of the solvent is 1:10), and the mixture is stirred for 6 hours to obtain a glue solution; then 0.5g of glue solution is added into 0.5g of sulfide solid electrolyte Li6PS5Cl, the dispersion is uniform, and then the slurry obtained after the dispersion is coated on a substrate, and the electrolyte membrane is obtained by heating and drying at the drying temperature of 40 ℃.
Example 5: application in negative electrode plate
The embodiment relates to a negative electrode plate, which is mainly prepared by the following steps: 0.2g of ethylene ethyl acrylate copolymer (wherein the content of ester groups accounts for 10 percent of the weight of the ethylene acrylic ester copolymer), 0.1g of lithium tetrafluoroborate is added into a mixed solvent of xylene and hexyl acetate (the volume ratio of the solvent is 1:1), and the mixture is stirred for 6 hours to obtain a glue solution; then taking 0.7g of glue solution (wherein the sum of the weight of ethylene-ethyl acrylate copolymer and lithium tetrafluoroborate is 0.015 g), adding 0.035g of conductive agent, 0.14g of sulfide solid electrolyte Li3PS4 and 0.525g of silicon-carbon negative electrode active material, dispersing uniformly, and coating the dispersed slurry on a current collector; and (5) heating and drying at the drying temperature of 100 ℃ to obtain the negative electrode plate.
Example 6: application in positive pole piece
The embodiment relates to a positive pole piece, which is mainly prepared by the following steps: weighing 0.2g of ethylene butyl acrylate copolymer (wherein the content of ester groups accounts for 30% of the weight of the ethylene acrylic ester copolymer), adding 0.2g of lithium bistrifluoromethane sulfonyl imide into a mixed solvent of toluene and butyl butyrate (the volume ratio of the solvent is 1:20), and heating and stirring at 45 ℃ for 6 hours to obtain a glue solution; then taking 0.7g of glue solution (wherein the sum of the weight of ethylene butyl acrylate copolymer and lithium bistrifluoro-methylsulfonyl imide is 0.015 g), adding 0.014g of conductive agent and 0.14g of sulfide solid electrolyte Li6PS5Cl, and 0.511g of positive electrode active material, uniformly dispersing, then coating the dispersed slurry on a current collector, heating and drying at 200 ℃ to obtain the positive electrode plate.
Comparative example 1
In the comparative example, 0.2g of ethylene methyl acrylate (wherein the content of ester groups accounts for 1 percent of the weight of the ethylene acrylic ester copolymer) is copolymerized, 3.7g of dimethylbenzene and isobutyl isobutyrate are added into a mixed solvent (the volume ratio of the solvent is 1:10), and the mixture is stirred for 6 hours to obtain a glue solution; then 0.5g of glue solution is added into 0.5g of sulfide solid electrolyte Li6PS5Cl, the dispersion is uniform, and then the slurry obtained after the dispersion is coated on a substrate, and the electrolyte membrane is obtained by heating and drying at the drying temperature of 40 ℃.
Comparative example 2
The comparative example relates to a negative electrode plate, which is mainly prepared by the following steps: adding 0.2g of ethylene ethyl acrylate copolymer (wherein the content of ester groups accounts for 50 percent of the weight of the ethylene acrylic ester copolymer) into a mixed solvent of xylene and hexyl acetate (the volume ratio of the solvent is 1:1), and stirring for 6 hours to obtain a glue solution; then 0.7g of glue solution is taken, 0.035g of conductive agent, 0.14g of sulfide solid electrolyte Li3PS4 and 0.525g of silicon-carbon negative electrode active material are added, the dispersion is uniform, and then the slurry obtained after the dispersion is coated on a current collector; and (5) heating and drying at the drying temperature of 100 ℃ to obtain the negative electrode plate.
Comparative example 3
The comparative example relates to a positive electrode plate, which is mainly prepared by the following steps: weighing 0.2g of ethylene butyl acrylate copolymer (wherein the content of ester groups accounts for 40 percent of the weight of the ethylene acrylic ester copolymer), adding the copolymer into a mixed solvent of toluene and butyl butyrate (the volume ratio of the solvent is 1:20), and heating and stirring at 45 ℃ for 6 hours to obtain a glue solution; then 0.7g of glue solution is added with 0.014g of conductive agent, 0.14g of sulfide solid electrolyte Li6PS5Cl, 0.511g of positive electrode active material, the mixture is uniformly dispersed, and the dispersed slurry is coated on a current collector, and is heated and dried at a drying temperature of 200 ℃ to obtain the positive electrode plate.
Experimental example
(1) Ion conductivity test
The electrolyte membranes prepared in example 4 and comparative example 1 described above were respectively subjected to an ion conductivity (25 ℃) test, and the test results are shown in fig. 1 below.
Example 4 the electrolyte membrane had an ionic conductivity of 1.45 mS/cm and the electrolyte membrane of comparative example 1 had an ionic conductivity of 0.83 mS/cm, indicating that the ethylene acrylate copolymer to which the lithium salt was added had good lithium ion conductivity.
(2) Battery performance test
The half batteries prepared in example 5, example 6, comparative example 2 and comparative example 3 were selected, and the positive electrode sheet was subjected to electrochemical constant current charge and discharge test at a voltage interval of 2.1 to 3.7V and a rate of 0.5C, and the specific capacity of cyclic discharge was shown in fig. 2. The cathode pole piece is subjected to electrochemical constant current charge and discharge test under the conditions of 2.1-3.7V voltage intervals of 0.1C, 0.2C, 0.5C, 1C and 2C multiplying power, and the charge and discharge curves are shown in figure 3.
Compared with the comparative example 3, the positive electrode plate adhesive in the example 6 has better adhesive force, so that the plate has better stripping force and the cycle stability is improved. In addition, the ethylene acrylic ester copolymer added with lithium salt has better lithium ion conduction capability, and can effectively relieve the situation that the adhesive is coated on the surface of the active material to reduce the lithium conduction capability of the active material, so that the battery has better electrochemical performance.
Compared with comparative example 2, the negative electrode plate binder of example 5 has better adhesion, can relieve the active material drop caused by the volume expansion of the negative electrode in the charge and discharge process, has better cycle stability, and in addition, the ethylene acrylic ester copolymer added with lithium salt in the plate binder has better lithium ion conductivity, can effectively relieve the effect that the binder is coated on the surface of the active material to reduce the lithium conductivity of the active material, so that the battery has better multiplying power performance.
In summary, the content of ester groups in the ethylene acrylic ester copolymer is regulated to be less than 30wt%, so that the adhesive has high adhesive force, the requirements for preparing the battery pole piece and the electrolyte membrane are met, and the adhesive can be dissolved in a low-polarity solvent compatible with sulfide solid electrolyte, thereby avoiding adverse effects of the solvent on the performance of the sulfide electrolyte; and the oxygen of the ester group in the ethylene acrylic ester copolymer with high polarity can coordinate with lithium ions in lithium salt, so that the lithium salt can be easily dissociated, and meanwhile, the chain segment of the ethylene acrylic ester copolymer can move, so that the ethylene acrylic ester copolymer added with the lithium salt has good lithium ion conduction capability, thereby enabling the binder to have lithium conduction capability, avoiding the binder from being coated on the surfaces of active substances and solid electrolyte to reduce the lithium conduction capability, and effectively solving the technical difficulty that the performance of a lithium ion battery is deteriorated by using the binder.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the invention.

Claims (10)

1. A binder for a lithium ion battery, wherein the binder for a lithium ion battery comprises an ethylene acrylate copolymer, and the ratio of the weight of ester groups in the ethylene acrylate copolymer to the weight of the ethylene acrylate copolymer is less than 30%.
2. The binder for a lithium ion battery according to claim 1, wherein the binder for a lithium ion battery further comprises a lithium salt.
3. The binder for a lithium ion battery according to claim 2, wherein the binder for a lithium ion battery satisfies at least one of the following conditions:
A. the weight of ester groups in the ethylene acrylic ester copolymer is 1-30% of the weight of the ethylene acrylic ester copolymer;
B. the ethylene acrylic ester copolymer comprises any one or a combination of at least two of ethylene methyl acrylate, ethylene ethyl acrylate and ethylene butyl acrylate;
C. the lithium salt comprises any one or a combination of at least two of lithium bis (trifluoromethanesulfonyl imide), lithium bis (fluorosulfonyl imide), lithium hexafluorophosphate, lithium perchlorate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium trifluoromethanesulfonate, lithium difluorooxalato borate, lithium hexafluoroarsenate and lithium difluorophosphate;
D. the weight ratio of the lithium salt to the ethylene acrylate copolymer is 0.01% -300%.
4. A pole piece for a lithium ion battery, characterized in that the pole piece comprises the binder for a lithium ion battery according to any one of claims 1 to 3.
5. The preparation method of the pole piece for the lithium ion battery as claimed in claim 4, which is characterized by comprising the following steps:
uniformly mixing the binder for the lithium ion battery with an active substance, a conductive agent, a first solid electrolyte and a first solvent to obtain first slurry;
coating the first slurry on a current collector;
and after the first drying, obtaining the pole piece for the lithium ion battery.
6. The method according to claim 5, wherein the polarity parameter of the first solvent is less than 3.1, and the active material is a positive electrode active material or a negative electrode active material.
7. The production method according to claim 5, wherein the first solvent comprises at least one of toluene, xylene, n-hexane, n-heptane, isobutyl isobutyrate, hexyl acetate, and butyl butyrate;
the weight ratio of the binder for the lithium ion battery to the active material, the conductive agent and the first solid electrolyte is (0.5-5) 100 (0.1-20) 5-30;
in the first drying, the drying temperature is 40-200 ℃ and the drying time is 10min-48h.
8. An electrolyte membrane for a lithium ion battery, characterized in that the electrolyte membrane comprises the binder for a lithium ion battery according to any one of claims 1 to 3.
9. The method for preparing the electrolyte membrane for the lithium ion battery according to claim 8, comprising the following steps:
uniformly mixing the binder for the lithium ion battery, a second solvent and a second solid electrolyte to obtain second slurry;
coating the second slurry on a substrate;
and after the second drying, obtaining the electrolyte membrane for the lithium ion battery.
10. The production method according to claim 9, wherein the second solvent comprises at least one of toluene, xylene, n-hexane, n-heptane, isobutyl isobutyrate, hexyl acetate, and butyl butyrate;
the weight ratio of the binder for lithium ion battery to the second solid electrolyte is (0.5-20): 100;
and in the second drying, the drying temperature is 40-200 ℃ and the drying time is 10min-48h.
CN202311632701.2A 2023-12-01 2023-12-01 Adhesive, pole piece, electrolyte membrane for lithium ion battery and preparation method Pending CN117327460A (en)

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