Non-fluorine binder and application thereof in field of secondary batteries

Abstract

The present invention relates to the technical field of battery binders, and specifically to a non-fluorine binder and an application thereof in the field of secondary batteries. The technical problem to be solved by the present invention is to provide a non-fluorine binder having good solubility in NMP. The binder comprises a modified resin, wherein the modified resin is formed by polymerizing a thermoplastic resin, a functional monomer and a nitrile-group-containing unsaturated monomer. The binder has normal-temperature solubility in an NMP solvent, can improve the high-temperature tolerance of the material in a carbonate electrolyte and the adhesion of the material to a metal foil, and can thus be applied to the fields of edge-coated protective adhesives, conductive dispersion adhesives and positive and negative electrode binders for lithium-ion batteries; and the binder can be used alone or in combination with other binders, has outstanding price and environmental advantages, and can be used in lithium-ion batteries instead of traditional fluorine resins.

Description

Non-fluorinated binders and their applications in secondary batteries

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of and priority to Chinese patent application CN2023117004969, filed on December 12, 2023, and is incorporated herein by reference in its entirety for all other purposes. Technical Field

[0003] The present invention relates to a non-fluorine binder and application thereof in the field of secondary batteries, belonging to the technical field of battery binders. Background Art

[0004] Lithium battery binders are polymer materials that bond powders of positive and negative electrode active materials, conductive agents, and other materials to the current collector (copper or aluminum foil). Their function is to bond the materials together, stabilize the electrode structure, and ensure electronic contact between the electrode active material and the conductive agent, as well as between the active material and the current collector, during the battery reaction. Typically, binder usage accounts for 2% to 5% of the total positive and negative electrode active materials.

[0005] As our understanding of lithium batteries deepens, the basic requirements for adhesives can be met with current technology. Currently, the main issue that needs to be resolved is the conflicting requirements between slurry and electrode processing, electrolyte resistance, and battery performance. For example, PVDF is a relatively traditional and classic positive electrode adhesive material with excellent overall performance. However, with the continuous development of positive electrode materials and the continuous improvement of battery performance requirements, higher requirements are also placed on positive electrode adhesives. When PVDF is used as an adhesive in high-nickel positive electrode materials, the presence of slurry gel and alkali in the production process will cause PVDF molecules to undergo elimination reactions.

[0006] To address these issues, thermoplastic elastomers, rubber, and polyester have become candidates for positive electrode binder materials. However, these three types of materials currently have disadvantages such as insolubility in NMP, poor resistance to electrolyte swelling, or poor electrochemical stability.

[0007] Thermoplastic elastomers have high flexibility and initial adhesion, which can improve the flexibility of coatings and electrodes and prevent gelation during the pulping process, thus meeting electrode processing requirements. However, they are insoluble in NMP, are not resistant to electrolytes, and are not resistant to electrochemical oxidation. Therefore, there is little research on adhesives. Only Dominic Rochefort's research team in Canada used a commercial copolymer of ethylene, acrylate, and maleic anhydride (Lotader 5500) as a binder for lithium iron phosphate positive electrodes. This material demonstrated good electrode processing performance, battery capacity, and cycle performance. However, due to the high content of low-polarity components such as ethylene (thermoplastic resin) in the Lotader series, the polymer resin itself has low polarity and can only be used in low-polarity solvents such as toluene. Currently, all supporting systems in the lithium battery industry use N-methyl-2-pyrrolidone (NMP) as a solvent. Therefore, the adhesive used must have good solubility and fluidity in NMP solvent conditions to meet industry application requirements. Therefore, there is an urgent need to develop binders that dissolve well in NMP at room temperature.

[0008] Summary of the Invention

[0009] The technical problem solved by the present invention is to provide a non-fluorine binder with good solubility in NMP.

[0010] The non-fluorine binder of the present invention includes a modified resin, which is formed by polymerizing a thermoplastic resin, a functional monomer and a nitrile-containing unsaturated monomer. In terms of weight percentage, the thermoplastic resin accounts for 20 to 50%, the functional monomer accounts for 2 to 20%, and the rest is the nitrile-containing unsaturated monomer; and the concentration of the modified resin after being dissolved in NMP at room temperature is greater than or equal to 2wt%; the functional monomer includes at least one of an unsaturated monomer having a carboxyl group (anhydride), an unsaturated monomer having a sulfonic acid group, an unsaturated monomer having an amino group and an unsaturated monomer having a hydroxyl group.

[0011] The present invention graft-modifies a thermoplastic resin to make it soluble in NMP solvent at room temperature. At the same time, the material's high-temperature tolerance in carbonate electrolytes and its adhesion to metal foils are improved, making it applicable to the fields of lithium-ion battery edge coating protective adhesives, conductive dispersion adhesives, and positive and negative electrode binders. The resin can be used alone or in combination with other binders.

[0012] Thermoplastic resins commonly used in battery adhesives in the art are suitable for use in the present invention. In one embodiment of the present invention, the thermoplastic resin includes at least one of an ethylene-acrylic acid copolymer having an acrylic acid monomer content of less than 18%, an ethylene-vinyl acetate copolymer having a vinyl acetate monomer content of less than 33%, an ethylene-methyl acrylate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-butyl acrylate copolymer, and an ethylene-maleic anhydride copolymer.

[0013] Functional monomers can improve the adhesion of the resin to the metal foil. In some embodiments of the present invention, the unsaturated monomer having a carboxyl group (anhydride) includes at least one of (meth) acrylic acid, undecylenic acid, octadecylenic acid, crotonic acid, itaconic acid, fumaric acid, maleic anhydride, 2-ethyl acrylic acid, isocrotonic acid, α-acetoxy acrylic acid, β-trans-aryloxy acrylic acid, α-chloro-β-E-methoxy acrylic acid, and β-diamino acrylic acid, maleic anhydride, acrylic anhydride, methylmaleic anhydride, dimethylmaleic anhydride, methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate.

[0014] The unsaturated monomer having a sulfonic acid group includes at least one of 2-acrylamido-2-methylpropanesulfonic acid, allyloxyhydroxypropylsulfonic acid or allyloxyhydroxypropylsulfonic acid, vinylsulfonic acid, vinylsulfonate, 2-acrylamido-2-methylpropanesulfonic acid, propylenesulfonic acid, and methpropylenesulfonic acid.

[0015] The unsaturated monomer having an amino group includes at least one of dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, 2-(dimethylamino)ethyl methacrylate, and N-(2-aminoethyl)acrylamide.

[0016] The unsaturated monomer having a hydroxyl group includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, and hydroxyethyl caprolactone acrylate.

[0017] In one embodiment of the present invention, the nitrile group-containing unsaturated monomer includes at least one of acrylonitrile, 3-butenenitrile, 3-pentenenitrile, 4-pentenenitrile and methacrylonitrile.

[0018] In a preferred embodiment of the present invention, the thermoplastic resin accounts for 30 to 50%.

[0019] In a specific embodiment of the present invention, the molecular weight of the thermoplastic resin is 50,000 to 400,000.

[0020] The present invention also provides application of the non-fluorine binder of the present invention in the field of secondary batteries.

[0021] The non-fluorine binder of the present invention has comparable performance to PVDF and can replace PVDF for use in lithium-ion batteries, including but not limited to being used as an active material binder, a ceramic binder for electrode edge coating (electrode ear glue), etc.

[0022] The normal temperature described in the present invention is 25°C.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The invention obtains a modified resin by modifying a thermoplastic resin through specific graft copolymerization, so that the modified resin can be well dissolved in NMP, thereby improving the tolerance of the binder to carbonate electrolytes and improving the adhesion of the material to foils.

[0025] The binder of the present invention has room-temperature solubility in NMP solvent and can improve the material's high-temperature tolerance in carbonate electrolytes and its adhesion to metal foils. It can be applied to the fields of lithium-ion battery edge coating protective glue, conductive dispersion glue, and positive and negative electrode binders. It can be used alone or in combination with other binders.

[0026] The non-fluorine binder of the present invention has excellent bonding properties and stable electrochemical properties, does not contain fluorine, has outstanding price and environmental advantages, and can replace traditional fluorine resins for use in lithium-ion batteries. DETAILED DESCRIPTION

[0027] The non-fluorine binder of the present invention includes a modified resin, which is formed by polymerizing a thermoplastic resin, a functional monomer and a nitrile-containing unsaturated monomer. In terms of weight percentage, the thermoplastic resin accounts for 20 to 50%, the functional monomer accounts for 2 to 20%, and the rest is the nitrile-containing unsaturated monomer; and the concentration of the modified resin after being dissolved in NMP at room temperature is greater than or equal to 2wt%; the functional monomer includes at least one of an unsaturated monomer having a carboxyl group (anhydride), an unsaturated monomer having a sulfonic acid group, an unsaturated monomer having an amino group and an unsaturated monomer having a hydroxyl group.

[0028] The present invention graft-modifies a thermoplastic resin to make it soluble in NMP solvent at room temperature. At the same time, the material's high-temperature tolerance in carbonate electrolytes and its adhesion to metal foils are improved, making it applicable to the fields of lithium-ion battery edge coating protective adhesives, conductive dispersion adhesives, and positive and negative electrode binders. The resin can be used alone or in combination with other binders.

[0029] Thermoplastic resins commonly used in battery adhesives in the art are suitable for use in the present invention. In one embodiment of the present invention, the thermoplastic resin includes at least one of an ethylene-acrylic acid copolymer having an acrylic acid monomer content of less than 18%, an ethylene-vinyl acetate copolymer having a vinyl acetate monomer content of less than 33%, an ethylene-methyl acrylate copolymer, an ethylene-ethyl acrylate copolymer, an ethylene-butyl acrylate copolymer, and an ethylene-maleic anhydride copolymer.

[0030] Functional monomers can improve the adhesion of the resin to the metal foil. In some embodiments of the present invention, the unsaturated monomer having a carboxyl group (anhydride) includes at least one of (meth) acrylic acid, undecylenic acid, octadecylenic acid, crotonic acid, itaconic acid, fumaric acid, maleic anhydride, 2-ethyl acrylic acid, isoctonic acid, α-acetoxy acrylic acid, β-trans-aryloxy acrylic acid, α-chloro-β-E-methoxy acrylic acid, and β-diamino acrylic acid, maleic anhydride, acrylic anhydride, methylmaleic anhydride, dimethylmaleic anhydride, methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate.

[0031] The unsaturated monomer having a sulfonic acid group includes at least one of 2-acrylamido-2-methylpropanesulfonic acid, allyloxyhydroxypropylsulfonic acid or allyloxyhydroxypropylsulfonic acid, vinylsulfonic acid, vinylsulfonate, 2-acrylamido-2-methylpropanesulfonic acid, propenesulfonic acid, and methacrylsulfonic acid.

[0032] The unsaturated monomer having an amino group includes at least one of dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, 2-(dimethylamino)ethyl methacrylate, and N-(2-aminoethyl)acrylamide.

[0033] The unsaturated monomer having a hydroxyl group includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, and hydroxyethyl caprolactone acrylate.

[0034] The nitrile-containing unsaturated monomer can improve the solubility of the resin in NMP and its adhesion to metal materials. The nitrile-containing unsaturated monomers commonly used in the art are all suitable for the present invention. In one embodiment of the present invention, the nitrile-containing unsaturated monomer includes at least one of acrylonitrile, 3-butenenitrile, 3-pentenenitrile, 4-pentenenitrile and methacrylonitrile.

[0035] In a preferred embodiment of the present invention, the thermoplastic resin accounts for 30 to 50%.

[0036] In a specific embodiment of the present invention, the molecular weight of the thermoplastic resin is 50,000 to 400,000. The molecular weights mentioned in the present invention are all weight average molecular weights.

[0037] The modified resin of the present invention can be obtained by polymerization using conventional graft copolymerization methods in the art.

[0038] In one embodiment of the present invention, a solution polymerization method is used. A thermoplastic resin is dissolved in a weakly polar solvent, and polymer modification is performed by solution grafting under certain reaction conditions. The polymer is then dried and dissolved in NMP solvent at room temperature. The polymer is applied in the field of lithium battery-related binders.

[0039] In a specific embodiment, the reaction medium of solution polymerization includes, but is not limited to, weak polar solvents such as benzene, toluene, xylene, ethyl acetate, and butyl acetate.

[0040] The present invention also provides the use of the non-fluorine binder of the present invention in the field of secondary batteries. In a specific embodiment, the secondary battery is a lithium ion battery.

[0041] The non-fluorine binder of the present invention has comparable performance to PVDF and can replace PVDF for use in lithium-ion batteries, including but not limited to being used as an active material binder, a ceramic binder for electrode edge coating (electrode lug glue), etc. In a specific embodiment, the secondary battery is a lithium-ion battery.

[0042] The normal temperature described in the present invention is 25°C.

[0043] The following examples further describe the specific embodiments of the present invention, but the present invention is not limited to the scope of the embodiments. The performance test of the products in the examples is carried out using the following method:

[0044] (1) Dissolution test

[0045] The sample to be tested was placed in a beaker with magnetic stirring, NMP was added to dissolve (concentration ≥ 2%), and the mixture was stirred and dispersed at 25° C. for 24 hours. The dissolution state of the sample to be tested in the NMP solvent was observed.

[0046] (2) Electrolyte swelling test (70℃ / 24h)

[0047] In the present invention, the electrolyte swelling degree refers to the swelling degree of the part that is insoluble in the electrolyte when the modified rubber film is immersed in a carbonate electrolyte salt solution at 70°C / 24h. Here, the electrolyte swelling degree of the modified rubber can be specifically calculated by the following method: prepare an NMP solution containing a modified resin, and completely dry the dispersion in a blast oven at 110°C to form a film with a thickness of 0.2 to 0.5 mm. Cut the film into 2.5 mm squares and accurately weigh about 1 g. The mass of the diaphragm obtained by cutting is set to W0. The obtained diaphragm is immersed in 100 g of electrolyte (Shanshan 12663) at 70°C for 24 hours. Then, the diaphragm is removed from the electrolyte, the excess electrolyte components on the surface are wiped off with a dust-free cloth, and the mass of the diaphragm is weighed W1. The mass change is calculated according to the following formula and is used as the electrolyte swelling degree.

[0048] Swelling % = {(W1-W0) / W0}*100

[0049] (3) DMC solvent dissolution test (70℃ / 24h)

[0050] The sample preparation method is the same as above. The modified rubber diaphragm is dried and weighed as M0, then immersed in DMC solvent, sealed, and stored at 70℃ for 24h. After being taken out, the excess solvent on the surface is wiped off with a dust-free cloth, and placed in a 110℃ forced air oven for 5h. The weight of the diaphragm is weighed as M1.

[0051] Dissolution % = {(M0-M1) / M0}*100

[0052] (4) Prepare lithium cobalt oxide positive electrode and test the peeling force between the coating and aluminum foil

[0053] The slurry was prepared according to the following formula and process, wherein the slurry formula is shown in Table 1 and the stirring process is shown in Table 2.

[0054] Table 1

[0055] Table 2

[0056] Pole sheet preparation: The positive electrode slurry is coated on the aluminum foil to make a single-sided surface density of 240g / m 2 , 40mm width pole piece, test 180° coating peeling force.

[0057] Example 1

[0058] In a 500mL four-necked flask, add xylene, add 19g ethylene vinyl acetate (LG, Korea EA28400) resin particles under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 5g 2-acrylamido-2-methylpropanesulfonic acid at one time, and at the same time, add 76g acrylonitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70℃ for 15 hours, and dry the solution at 60℃ for later use.

[0059] Example 2

[0060] In a 500mL four-necked flask, add xylene, add 22.5g ethylene vinyl acetate (LG, Korea EA28400) resin particles under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 10g allyl sulfonic acid at one time, and at the same time, add 67.5g acrylonitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70℃ for 15 hours, and dry the solution at 60℃ for later use.

[0061] Example 3

[0062] In a 500mL four-necked flask, add xylene, add 30g ethylene vinyl acetate (LG, EA28400, South Korea) resin particles under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 20g acrylic acid at one time, and at the same time, add 50g acrylonitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70℃ for 15 hours, and dry the solution at 60℃ for later use.

[0063] Example 4

[0064] In a 500mL four-necked flask, add xylene, add 28.3g ethylene ethyl acrylate EEA (DuPont EEA2116, USA) resin particles under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 15g methacrylic acid at one time, and at the same time, add 56.7g acrylonitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70℃ for 15 hours, and dry the solution at 60℃ for later use.

[0065] Example 5

[0066] In a 500mL four-necked flask, add xylene, add 47.5g ethylene-acrylic acid ((LG, Korea, EAA5080)) resin particles (molecular weight 200,000)) under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 5g N-(2-aminoethyl) acrylamide at one time, and at the same time, add 47.5g acrylonitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70℃ for 15 hours, and then dry the solution at 60℃ for later use.

[0067] Example 6

[0068] In a 500mL four-necked flask, add xylene, add 26g ethylene-maleic anhydride EMAH resin particles (DuPont 21E533, USA) under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 20g hydroxyethyl acrylate at one time, and at the same time, add 54g acrylonitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70℃ for 15 hours, and dry the solution at 60℃ for later use.

[0069] Example 7

[0070] In a 500mL four-necked flask, add xylene, add 30g of ethylene-butyl acrylate EBA resin particles (DuPont AC 34035, USA) under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 8g of maleic anhydride at one time, and at the same time, add 62g of acrylonitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70℃ for 15 hours, and dry the solution at 60℃ for later use.

[0071] Example 8

[0072] In a 500mL four-necked flask, add xylene, add 30g ethylene vinyl acetate EVA (LG, Korea EA28400) resin particles under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 10g undecylenic acid at one time, and at the same time, add 60g 3-butenenitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70℃ for 15 hours, and dry the solution at 60℃ for later use.

[0073] Comparative Example 1

[0074] Unmodified EVA resin (LG, Korea, EA28400)

[0075] Comparative Example 2

[0076] Unmodified EAA resin (Korea LG, EAA5080)

[0077] Comparative Example 3

[0078] In a 500mL four-necked flask, add xylene, add 17g ethylene vinyl acetate (LG, Korea EA28400) resin particles under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 6g acrylic acid at one time, and at the same time, add 77g acrylonitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70℃ for 15 hours, and dry the solution at 60℃ for later use.

[0079] Comparative Example 4

[0080] In a 500mL four-necked flask, add xylene and, while stirring, add 52g of ethylene vinyl acetate (LG, EA28400, South Korea) resin pellets. Dissolve at 65°C to a colorless, transparent solution. Then cool to 60-70°C, add a peroxide or azo initiator, add 5g of acrylic acid all at once, and simultaneously add 43g of acrylonitrile monomer dropwise over 2 hours. Add the peroxide or azo initiator every 3 hours. Keep the reaction at 70°C for 15 hours, and then air dry the solution at 60°C for later use. The synthesis and preparation process are the same as in Example 2, by weight.

[0081] Comparative Example 5

[0082] In a 500mL four-necked flask, add xylene, add 30g ethylene vinyl acetate (LG, Korea EA28400) resin particles under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 1g acrylic acid at one time, and at the same time, add 69g acrylonitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70℃ for 15 hours, and dry the solution at 60℃ for later use.

[0083] Comparative Example 6

[0084] In a 500mL four-necked flask, add xylene, add 30g ethylene-vinyl acetate (LG, Korea EA28400) resin particles under stirring, dissolve at 65℃ to form a colorless transparent solution, then cool to the reaction temperature of 60-70℃, add peroxide or azo initiator, add 21g acrylic acid at one time, and at the same time, add 49g acrylonitrile monomer dropwise within 2 hours. As the reaction proceeds, the emulsion balance deteriorates, gel particles gradually form and precipitate, and the reaction is passively terminated.

[0085] Comparative Example 7

[0086] In a 500mL four-necked flask, add xylene, and under stirring, add peroxide or azo initiator at a reaction temperature of 60-70°C, add 20g of acrylic acid at one time, and at the same time, add 50g of acrylonitrile monomer dropwise within 2 hours, add peroxide or azo initiator every 3 hours, keep the reaction at 70°C for 15 hours, and then dry the solution at 60°C.

[0087] The dried material was mixed evenly with 30 g of ethylene vinyl acetate (LG, Korea, EA28400) resin particles, dissolved in NMP solvent at high temperature, and gelled when cooled to room temperature, which was not suitable for preparing positive electrode slurry.

[0088] Its performance test is shown in Table 3.

[0089] Table 3

[0090] It can be seen that the modified resin of the present invention can be well dissolved in NMP, thereby improving the tolerance of the binder to carbonate electrolytes and improving the adhesion of the material to the foil.

Claims

1. Non-fluorine binder, characterized in that: The binder comprises a modified resin, wherein the modified resin is polymerized from a thermoplastic resin, a functional monomer and an unsaturated monomer containing a nitrile group, and in terms of weight percentage, the thermoplastic resin accounts for 20-50%, the functional monomer accounts for 2-20%, and the rest is the unsaturated monomer containing a nitrile group; and the concentration of the modified resin after being dissolved in NMP at room temperature is ≥2wt%; The functional monomer includes at least one of an unsaturated monomer having a carboxyl group (anhydride), an unsaturated monomer having a sulfonic acid group, an unsaturated monomer having an amino group, and an unsaturated monomer having a hydroxyl group.

2. The non-fluorine binder according to claim 1, characterized in that: The thermoplastic resin includes at least one of ethylene-acrylic acid copolymer with acrylic acid monomer content less than 18%, ethylene-vinyl acetate copolymer with vinyl acetate monomer content less than 33%, ethylene-methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-butyl acrylate copolymer and ethylene-maleic anhydride copolymer.

3. The non-fluorine binder according to claim 1, characterized in that: The unsaturated monomer having a carboxyl group (anhydride) includes at least one of (meth) acrylic acid, undecylenic acid, octadecylenic acid, crotonic acid, itaconic acid, fumaric acid, maleic anhydride, 2-ethyl acrylic acid, isocrotonic acid, α-acetoxy acrylic acid, β-trans-aryloxy acrylic acid, α-chloro-β-E-methoxy acrylic acid, β-diamino acrylic acid, maleic anhydride, acrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride, methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, octadecyl maleate and fluoroalkyl maleate; The unsaturated monomer having a sulfonic acid group includes at least one of 2-acrylamide-2-methylpropanesulfonic acid, allyloxyhydroxypropylsulfonic acid or allyloxyhydroxypropylsulfonic acid, vinylsulfonic acid, vinylsulfonic acid salt, 2-acrylamide-2-methylpropanesulfonic acid, propylenesulfonic acid and methpropylenesulfonic acid; The unsaturated monomer having an amino group includes at least one of dimethylaminoethyl acrylate, diethylaminoethyl methacrylate, 2-(dimethylamino)ethyl methacrylate and N-(2-aminoethyl)acrylamide; The unsaturated monomer having a hydroxyl group includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, and hydroxyethyl caprolactone acrylate.

4. The non-fluorine adhesive according to claim 1, characterized in that: The nitrile group-containing unsaturated monomer includes at least one of acrylonitrile, 3-butenenitrile, 3-pentenenitrile, 4-pentenenitrile and methacrylonitrile.

5. The non-fluorine adhesive according to claim 1, characterized in that: The thermoplastic resin accounts for 30 to 50%.

6. The non-fluorine adhesive according to claim 1, characterized in that: The molecular weight of the thermoplastic resin is 50,000 to 400,000.

7. Use of the non-fluorine binder according to any one of claims 1 to 6 in the field of secondary batteries.

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