Non-fluorine positive electrode binder for lithium-ion battery and positive electrode plate

Abstract

The present invention relates to a non-fluorine positive electrode binder for a lithium-ion battery and a positive electrode plate, and belongs to the technical field of lithium-ion batteries. The technical problem solved by the present invention is to provide a non-fluorine positive electrode binder for a lithium-ion battery. The non-fluorine positive electrode binder for a lithium-ion battery of the present invention comprises a copolymer, wherein the polymerization monomers of the copolymer comprise an acrylonitrile-based monomer, an acrylate-based monomer, an acrylamide-based monomer, and a thiourea group / urea group-based monomer. The non-fluorine positive electrode binder for a lithium-ion battery of the present invention has good flexibility and adhesive strength, can be used in a positive electrode of a lithium-ion battery, meets the processing requirements for battery cell preparation, and exhibits good electrolyte resistance, with low swelling and dissolution in the electrolyte.

Description

Non-fluorinated cathode binder and cathode sheet for lithium-ion batteries

[0001] Cross-reference to related applications

[0002] This application claims the benefit and priority of Chinese patent application CN2025103731242, filed on March 27, 2025, which is incorporated herein by reference and for all other purposes. Technical Field

[0003] This invention relates to non-fluorinated positive electrode binders and positive electrode sheets for lithium-ion batteries, belonging to the field of lithium-ion battery technology. Background Technology

[0004] Currently, commercially available lithium-ion batteries mostly use oil-based polyvinylidene fluoride (PVDF) as a binder for their cathodes. PVDF production conditions are stringent, and its monomers, as fluorides, are strictly controlled. The fluorine atoms in its molecular structure have high electronegativity, making them prone to reacting with positively charged substances, such as metal ions, thus introducing metallic impurities into biomass. Furthermore, fluorinated polymers are difficult to degrade in the environment, can migrate long distances through soil, water, and air, accumulate in organisms, and can build up in terrestrial and aquatic ecosystems, causing negative environmental impacts. Therefore, there is a need to develop new fluorine-free lithium-ion cathode binders.

[0005] Currently, commonly used non-fluorinated cathode binders use NMP as a solvent and various modified polyacrylonitrile (PAN) as the main binder resin. PAN is a highly polar polymer with low swelling and dissolution in electrolytes and good electrochemical stability. Compared with PVDF, PAN-based binders can improve the polarity and bonding strength of electrode materials while reducing material costs. However, PAN-based binders have high glass transition temperatures and insufficient flexibility at room temperature, which cannot fully meet the requirements for electrical processing performance.

[0006] Chinese invention patent application number 201610677774 discloses an acrylonitrile copolymer adhesive using NMP as a solvent, comprising the following structural units by weight percentage: 78-95% acrylonitrile units, 1-10% acrylate units, 2-15% acrylamide units, and 2-8% acrylate units. This adhesive uses PAN as the main component. To increase the flexibility of PAN, acrylate monomers are copolymerized with acrylonitrile as flexible components, but further improvement in flexibility is still needed. Furthermore, the polarity and solubility of acrylate monomers are similar to those of the electrolyte, resulting in excessive swelling of the adhesive in the electrolyte, which degrades the performance of the battery cell.

[0007] Summary of the Invention

[0008] To address the above deficiencies, the technical problem solved by this invention is to provide a non-fluorinated positive electrode binder for lithium-ion batteries.

[0009] The present invention relates to a non-fluorinated positive electrode binder for lithium-ion batteries, comprising copolymers, wherein the monomers of the copolymers include acrylonitrile monomers, acrylate monomers, acrylamide monomers, and thiourea / urea monomers.

[0010] In one embodiment of the present invention, by weight, there are 78-95 parts of acrylonitrile monomers, 1-10 parts of acrylate monomers, 2-15 parts of acrylamide monomers, and 1-30 parts of thiourea / urea monomers.

[0011] In one embodiment of the present invention, acrylonitrile monomers include acrylonitrile or methacrylonitrile;

[0012] The structure of acrylate monomers is: CH2=CR 1 -COOR 2 , where R 1 For -H or -CH3, R 2 It is an alkyl or cycloalkyl group;

[0013] The structure of acrylamide monomers is: CH2=CR 3 CONHR 4 , where R 3 For -H or -CH3, R 4  is -H; alkyl; cycloalkyl or aromatic;

[0014] Thiourea / urea monomers are polymerized from biepoxides, sulfur-containing carbonyl / carbonyl compounds, and amines, with a number-average molecular weight of 400–100,000.

[0015] In some specific embodiments of the present invention, the acrylate monomers are at least one of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, and 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, and 2-ethylhexyl methacrylate; and the acrylamide monomers are at least one of acrylamide, N-methylacrylamide, N-ethylacrylamide, N-butylacrylamide, and 2-methylacrylamide.

[0016] In one embodiment of the invention, the diepoxide compound includes ; ; ; or .

[0017] Sulfur-containing carbonyl / carbonyl compounds include any one of the following monomers: ; ; ; ; ; ; ; ; ; ; ; ; ; S+ S+ S+ S+ S+ S+ .

[0018] Amine compounds are one or two of the following monomers: n1 is an integer from 1 to 10; n2 is an integer from 1 to 10; ; ; ; n3 is an integer from 1 to 10; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; n4 is an integer from 2 to 68; m2 is an integer from 9 to 39; m1 and m3 are integers greater than 0 and 3 ≤ m1 + m3 ≤ 6; n5 is an integer from 5 to 88; n6 is an integer from 1 to 20; n7 is an integer from 1 to 20; n8 is an integer from 1 to 20; ; ; ; ; ; .

[0019] In one embodiment of the present invention, the molar ratio of the diepoxide compound, the sulfur-containing carbonyl / carbonyl compound, and the amine compound is 1:3 to 5:1. Specifically, the molar ratio of the diepoxide compound, the sulfur-containing carbonyl / carbonyl compound, and the amine compound is 1:4:1.

[0020] In one specific embodiment, the thiourea-based / urea-based monomer is prepared using the following method:

[0021] A biepoxide compound, a sulfur-containing carbonyl / carbonyl compound, and an amine compound were added to a solvent and mixed. The mixture was reacted for 10–30 h to obtain product 1. After drying product 1, it was dissolved in a solvent. Then, triethylamine, methacryloyl chloride, and the catalyst 4-dimethylaminopyridine were added and reacted for 10–30 h. The reaction product was purified and dried to obtain thiourea / urea monomers.

[0022] In one embodiment of the present invention, the mass ratio of product 1, triethylamine and methacryloyl chloride is 1-5:2:2; the catalyst is 4-dimethylaminopyridine; and the amount of catalyst used is 0.05-0.2 mol.

[0023] In one embodiment of the present invention, the polymerizing monomer further includes an auxiliary agent, which includes at least one of a chain transfer agent, an emulsifier, and a dispersant.

[0024] In one embodiment of the present invention, the lithium-ion battery non-fluorinated positive electrode binder further includes a solvent, wherein the solvent is NMP.

[0025] The present invention also provides a positive electrode sheet for a lithium-ion battery.

[0026] The present invention relates to a lithium-ion battery positive electrode sheet, comprising a positive electrode material and an adhesive, wherein the adhesive is the non-fluorinated positive electrode binder for lithium-ion batteries described in this invention.

[0027] Commonly used cathode materials in this field are applicable to this invention. The cathode material includes a cathode active material, which may be one or more of lithium cobalt oxide (LCO), lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), or lithium nickel cobalt aluminum oxide (NCA).

[0028] In one specific embodiment, the amount of adhesive used accounts for 0.5 to 3 wt% of the total solid content, preferably 1 wt% of the total solid content. The total solid content referred to in this invention is the content of solids other than solvents in the positive electrode slurry, generally including the total content of positive electrode active material, conductive agent, adhesive, etc.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The non-fluorinated positive electrode binder for lithium-ion batteries of the present invention has good flexibility and bonding strength, can be used in the positive electrode of lithium-ion batteries, meets the processing requirements of cell preparation, and has good electrolyte resistance with low swelling and dissolution in electrolyte. Detailed Implementation

[0031] The present invention relates to a non-fluorinated positive electrode binder for lithium-ion batteries, comprising copolymers, wherein the monomers of the copolymers include acrylonitrile monomers, acrylate monomers, acrylamide monomers, and thiourea / urea monomers.

[0032] In one embodiment of the present invention, by weight, there are 78-95 parts of acrylonitrile monomers, 1-10 parts of acrylate monomers, 2-15 parts of acrylamide monomers, and 1-30 parts of thiourea / urea monomers.

[0033] In one embodiment of the present invention, acrylonitrile monomers include acrylonitrile or methacrylonitrile;

[0034] The structure of acrylate monomers is: CH2=CR 1 -COOR 2 , where R 1 For -H or -CH3, R 2 It is an alkyl or cycloalkyl group;

[0035] The structure of acrylamide monomers is: CH2=CR 3 CONHR 4 , where R 3 For -H or -CH3, R 4  represents -H; alkyl; cycloalkyl or aromatic group.

[0036] In some specific embodiments of the present invention, the acrylate monomers are at least one of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, and 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, and 2-ethylhexyl methacrylate; and the acrylamide monomers are at least one of acrylamide, N-methylacrylamide, N-ethylacrylamide, N-butylacrylamide, and 2-methylacrylamide.

[0037] In one embodiment of the present invention, the thiourea / urea monomer is polymerized from a biepoxide compound, a sulfur-containing carbonyl / carbonyl compound, and an amine compound, wherein the number average molecular weight of the thiourea / urea monomer is 400–100,000.

[0038] Diepoxides include ; ; ; or .

[0039] Sulfur-containing carbonyl / carbonyl compounds include any one of the following monomers: ; ; ; ; ; ; ; ; ; ; ; ; ; S+ S+ S+ S+ S+ S+ Among them, S+ For elemental S and Similarly, for mixtures of S+ For S and A mixture; S+ For S and A mixture of these substances... When these mixtures react, they can generate thiocarbonyl groups.

[0040] Amine compounds are one or two of the following monomers: n1 is an integer from 1 to 10; n2 is an integer from 1 to 10; ; ; ; n3 is an integer from 1 to 10; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; n4 is an integer from 2 to 68; m2 is an integer from 9 to 39; m1 and m3 are integers greater than 0 and 3 ≤ m1 + m3 ≤ 6; n5 is an integer from 5 to 88; n6 is an integer from 1 to 20; n7 is an integer from 1 to 20; n8 is an integer from 1 to 20; ; ; ; ; ; .

[0041] In one embodiment of the invention, the molar ratio of the diepoxide compound, the sulfur-containing carbonyl / carbonyl compound, and the amine compound is 1:3 to 5:1. Preferably, the molar ratio of the diepoxide compound, the sulfur-containing carbonyl / carbonyl compound, and the amine compound is 1:4:1.

[0042] Thiourea-based / urea-based monomers can be prepared using conventional methods in the art. In one specific embodiment, the thiourea-based / urea-based monomer is prepared using the following method:

[0043] A biepoxide compound, a sulfur-containing carbonyl / carbonyl compound, and an amine compound were added to a solvent and mixed. The mixture was reacted for 10–30 h to obtain product 1. After drying product 1, it was dissolved in a solvent. Then, triethylamine, methacryloyl chloride, and the catalyst 4-dimethylaminopyridine were added and reacted for 10–30 h. The reaction product was purified and dried to obtain thiourea / urea monomers.

[0044] This invention can be achieved using commonly used solvents in the field, including but not limited to tetrahydrofuran (THF).

[0045] In one embodiment of the present invention, the mass ratio of product 1, triethylamine and methacryloyl chloride is 1-5:2:2; the catalyst is 4-dimethylaminopyridine; and the amount of catalyst used is 0.05-0.2 mol.

[0046] In one embodiment of the present invention, the thiourea-based / urea-based monomer is prepared by the following method:

[0047] A biepoxide compound and a sulfur-containing carbonyl / carbonyl compound were added to THF. An amine compound was cooled in an ice bath for 0.5 h and then slowly added to the mixture. The reaction was carried out at room temperature for 24 h. The resulting solution was precipitated three times in THF / methyl tert-butyl ether, and the precipitate was dried in a vacuum oven at 40 °C for 12 h. The precipitate was then added to THF and dissolved by stirring at room temperature. Triethylamine, 4-dimethylaminopyridine, and methacryloyl chloride were then added, and the reaction was carried out at room temperature for 24 h. The reaction mixture was poured into water, purified by adding dichloromethane, and dried to obtain thiourea / urea monomers.

[0048] In one embodiment of the present invention, the polymerizing monomer further includes an auxiliary agent, which includes at least one of a chain transfer agent, an emulsifier, and a dispersant.

[0049] In one embodiment of the present invention, the lithium-ion battery non-fluorinated positive electrode binder further includes a solvent, wherein the solvent is NMP.

[0050] The copolymer of non-fluorinated cathode binder for lithium-ion batteries can be prepared using conventional methods in the art. In one embodiment of the present invention, it is prepared using the following method:

[0051] Acrylate monomers are added to the dispersion medium and stirred until dissolved. Then, acrylonitrile, acrylate monomers, acrylamide monomers, and thiourea / urea monomers are added. The mixture is heated to 40–80°C under an inert atmosphere. After the temperature stabilizes, an initiator is added to initiate the polymerization reaction for 2–24 hours, yielding a copolymer dispersion. This copolymer dispersion can be used directly as a non-fluorinated positive electrode binder for lithium-ion batteries. Alternatively, polymer powder can be obtained through precipitation, filtration, washing, drying, pulverizing, and sieving. When using this powder, it can be dispersed evenly with a solvent.

[0052] The present invention also provides a positive electrode sheet for a lithium-ion battery.

[0053] The present invention relates to a lithium-ion battery positive electrode sheet, comprising a positive electrode material and an adhesive, wherein the adhesive is the non-fluorinated positive electrode binder for lithium-ion batteries described in this invention.

[0054] Commonly used cathode materials in this field are applicable to this invention. The cathode material includes a cathode active material, which may be one or more of lithium cobalt oxide (LCO), lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium nickel cobalt manganese oxide (NCM), or lithium nickel cobalt aluminum oxide (NCA).

[0055] In one specific embodiment, the amount of adhesive used accounts for 0.5 to 3 wt% of the total solid content, preferably 1 wt% of the total solid content. The total solid content referred to in this invention is the content of solids other than solvents in the positive electrode slurry, generally including the total content of positive electrode active material, conductive agent, adhesive, etc.

[0056] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the examples described herein.

[0057] Example 1

[0058] 1. Synthesis of thiourea monomer: 1,2,7,8-diepoxyoctane (1 mol) and N,N′-thiocarbonyldiimidazole (4 mol) were added to 200 mL of tetrahydrofuran solution. An amine compound (1 mol) was cooled in an ice bath for 0.5 h and then slowly added to the mixture. The reaction was carried out at room temperature for 24 h. The resulting solution was precipitated three times in THF / methyl tert-butyl ether (30 mL), and the precipitate was dried in a vacuum oven at 40 °C for 12 h. The precipitate (1 g) was then added to THF (100 mL) and dissolved by stirring at room temperature. Triethylamine (0.35 g), 4-dimethylaminopyridine (0.05 mol), and methacryloyl chloride (0.35 g) were then added. The reaction was carried out at room temperature for 24 h. The reactants were poured into water, purified by adding dichloromethane, and dried to obtain the thiourea monomer. The amine compound used was: n2=2. The number-average molecular weight of this thiourea monomer is 4000.

[0059] 2. Synthesis of the copolymer: 900 parts of N-methylpyrrolidone were added to a reaction vessel, stirring was started, and high-purity nitrogen was purged for 1 hour to remove oxygen. Then, 5 parts of methyl acrylate, 5 parts of acrylamide, 80 parts of acrylonitrile, and 10 parts of thiourea-based polymer were added. The mixture was heated to 75°C under an inert atmosphere and held at that temperature. Then, 10 parts of 10% azobisisobutyronitrile (AIBN) were added to initiate the reaction. After each 1-hour reaction, 5 parts of 10% AIBN were added, and this process was repeated 5 times. The mixture was then kept at that temperature for 5 hours. After filtration and drying, a non-fluorinated positive electrode binder for lithium-ion batteries was obtained.

[0060] Example 2

[0061] 1. Synthesis of thiourea monomer: Same as in Example 1, except the amine compound used is... The number-average molecular weight of this thiourea monomer is 1600.

[0062] 2. Synthesis of the copolymer: 900 parts of N-methylpyrrolidone were added to a reaction vessel, followed by 2 parts of lithium methacrylate. Stirring was initiated, and high-purity nitrogen was introduced to remove oxygen for 1 hour. Then, 5 parts of methyl methacrylate, 5 parts of acrylamide, 83 parts of acrylonitrile, and 5 parts of thiourea monomer were added. The mixture was heated to 75°C under an inert atmosphere and held at that temperature. Then, 10 parts of 10% azobisisobutyronitrile (AIBN) were added to initiate the reaction. After each 1-hour reaction, 5 parts of 10% AIBN were added, repeating this process 5 times. The mixture was then kept at that temperature for 5 hours. After filtration and drying, a non-fluorinated positive electrode binder for lithium-ion batteries was obtained.

[0063] Example 3

[0064] 1. Synthesis of urea monomer: 1,2,7,8-diepoxyoctane (1 mol) and 1,1′-carbonyldiimidazole (5 mol) were added to 200 mL of tetrahydrofuran solution. An amine compound (1 mol) was cooled in an ice bath for 0.5 h and then slowly added to the mixture. The reaction was carried out at room temperature for 24 h. The resulting solution was precipitated three times in THF / methyl tert-butyl ether (30 mL), and the precipitate was dried in a vacuum oven at 40 °C for 12 h. The precipitate (1 g) was then added to THF (100 mL) and dissolved by stirring at room temperature. Triethylamine (0.40 g), 4-dimethylaminopyridine (0.05 mol), and methacryloyl chloride (0.40 g) were then added. The reaction was carried out at room temperature for 24 h. The reactants were poured into water, purified by adding dichloromethane, and dried to obtain the urea monomer. The amine compound used was: The number-average molecular weight of this urea monomer is 2000.

[0065] 2. Synthesis of the copolymer: 900 parts of N-methylpyrrolidone were added to a reaction vessel, stirring was started, and high-purity nitrogen was purged for 1 hour to remove oxygen. Then, 5 parts of methyl acrylate, 5 parts of acrylamide, 80 parts of acrylonitrile, and 10 parts of urea monomer were added. The mixture was heated to 75°C under an inert atmosphere and held at that temperature. Then, 10 parts of 10% azobisisobutyronitrile (AIBN) were added to initiate the reaction. After each 1-hour reaction, 5 parts of 10% AIBN were added, and this process was repeated 5 times. The mixture was then kept at that temperature for 5 hours. After filtration and drying, a non-fluorinated positive electrode binder for lithium-ion batteries was obtained.

[0066] Example 4

[0067] 1. Synthesis of urea monomers: Urea polymers were synthesized using the method described in Example 3, the only difference being that the amine compound was replaced with... n6=10. The number-average molecular weight of this urea monomer is 1800.

[0068] 2. Synthesis of the copolymer: 900 parts of N-methylpyrrolidone were added to a reaction vessel, stirring was started, and high-purity nitrogen was purged for 1 hour to remove oxygen. Then, 5 parts of methyl acrylate, 7 parts of acrylamide, 80 parts of acrylonitrile, and 8 parts of urea monomer were added. The mixture was heated to 75°C under an inert atmosphere and held at that temperature. Then, 10 parts of 10% azobisisobutyronitrile (AIBN) were added to initiate the reaction. After each 1-hour reaction, 5 parts of 10% AIBN were added, and this process was repeated 5 times. The mixture was then kept at that temperature for 5 hours. After filtration and drying, a non-fluorinated positive electrode binder for lithium-ion batteries was obtained.

[0069] Example 5

[0070] The copolymer was synthesized using the method of Example 1, with the amine monomer replaced by With n5=3, the number-average molecular weight of this thiourea monomer is 6300.

[0071] Example 6

[0072] The copolymer was synthesized using the method of Example 3, with the amine monomer replaced by With n4=10, the number-average molecular weight of this urea monomer is 12000.

[0073] Example 7

[0074] The copolymer was synthesized using the method of Example 1, with the amine monomer replaced by n4=10, the diepoxide compound is replaced with The number-average molecular weight of this thiourea monomer is 16,000.

[0075] Comparative Example 1

[0076] 1. Synthesis of polythiourea: 0.105 mol of 1,1′-thiocarbonyldiimidazole was added to a 50 mL solution of an amine compound (0.105 mol) in N,N-dimethylformamide. The mixture was stirred at 25 °C for 24 hours. 100 mL of chloroform was added to the solution, and then the diluted mixture was poured into 1.5 L of diethyl ether. The precipitate was dissolved in 50 mL of chloroform, and then the mixture was reprecipitated twice with chloroform / methanol. The insoluble fraction was collected by centrifugation, and the precipitate was dried in a vacuum oven at 140 °C for 12 hours. The resulting precipitate was then dried at 140 °C for 12 hours to obtain polythiourea.

[0077] The amine compounds used are n2=2.

[0078] The number-average molecular weight of this polythiourea is 12,500.

[0079] 2. Synthesis of polyacrylonitrile adhesives:

[0080] Add 900 parts of distilled water to the reaction vessel, start stirring, and purge with high-purity nitrogen to remove oxygen for 1 hour. Then add 5 parts of methyl acrylate, 5 parts of acrylamide, and 85 parts of acrylonitrile. Heat to 60°C under an inert atmosphere and maintain the temperature. Then add 5 parts of 20% ammonium persulfate initiator solution to initiate the reaction, and stop the reaction after 4 hours. After filtration, drying, pulverizing, and sieving, obtain the adhesive.

[0081] 3. Blending: The polythiourea and polyacrylonitrile binder are blended at a mass ratio of 10:90 to obtain a blended non-fluorinated binder for lithium-ion battery cathode.

[0082] Comparative Example 2

[0083] Polyacrylonitrile binders are used as the positive electrode binders for lithium-ion batteries.

[0084] The preparation method of polyacrylonitrile adhesives is as follows:

[0085] 900 parts of N-methylpyrrolidone were added to a reaction vessel, stirring was started, and high-purity nitrogen was purged for 1 hour to remove oxygen. Then, 5 parts of methyl acrylate, 5 parts of acrylamide, and 80 parts of acrylonitrile were added. The mixture was heated to 75°C under an inert atmosphere and kept at that temperature. Then, 10 parts of 10% azobisisobutyronitrile (AIBN) were added to initiate the reaction. After each 1-hour reaction, 5 parts of 10% AIBN were added, and this process was repeated 5 times. The mixture was then kept at that temperature for 5 hours. After filtration and drying, a non-fluorinated positive electrode binder for lithium-ion batteries was obtained.

[0086] Comparative Example 3

[0087] Commercially available PVDF is used as the binder for the positive electrode of lithium-ion batteries.

[0088] Performance testing:

[0089] The binder used in the examples and comparative examples was used to prepare the positive electrode slurry. The specific preparation method is as follows:

[0090] The obtained binder was dissolved in NMP, and then added to conductive carbon black and lithium cobalt oxide in a ratio of 98%:1%:1%. The mixture was stirred at high speed for 4 hours. The resulting slurry was then coated onto aluminum foil using a battery coating machine and dried at 110 °C. The dried electrode sheets were then rolled to achieve an areal density of 240–280 g / m³. 2 The compacted density is 4.2 g / cm³. 3 .

[0091] Film tensile test method:

[0092] Lay the PET film flat on a clean glass plate, and drop a suitable amount of ethanol between the PET film and the glass plate to facilitate a tight adhesion. Using a disposable dropper, take 20 mL of the test adhesive solution (after centrifugation and defoaming) and drop it onto the flat PET film. Adjust the thickness of the adjustable scraper according to the solid content of the adhesive solution to control the thickness of the dried adhesive solution to 0.03 ± 0.005 mm. Scrape the adhesive solution onto the PET film to form a uniform thickness film. Then transfer the sample to a forced-air oven at 110℃ and bake for 60 min (the glass plate must be placed horizontally; otherwise, the adhesive solution will flow during baking, causing uneven sample thickness). Take a uniformly thick film from the dried adhesive film and accurately cut it into strips 100 mm long and 10 mm wide using a double-edged blade. The initial gauge length for the test is 50 mm, the tensile speed is 200 mm / min, and the number of tests is greater than or equal to 3. The ambient temperature is 10–38℃, and the humidity is 25–30% RH.

[0093] Adhesion strength test method:

[0094] Peel strength was measured using a 180° high-precision micromechanical peel strength tester (Shenzhen Kaiqiangli Co., Ltd., China) at a constant displacement rate of 20.0 mm / min, using 25 mm tape (adhered to the active material side). The load and displacement used to peel the active material from the current collector were continuously recorded. National Standard: GB / T2790-1995. Ambient humidity ≤30% RH.

[0095] Solid content test method (instrument model: METTLER TOLEDO, LHS120-A, Mettler Todov Instruments (Shanghai) Co., Ltd.):

[0096] Turn on the power of the rapid drying moisture analyzer and preheat for 1 hour. After calibrating the instrument, select the sample (heated to 150℃), peel it, and press the start button to begin heating the drying pan. After heating stops, wait for the moisture analyzer to cool down until the temperature display on the screen changes to the mass display before performing the moisture content analysis at the required temperature. Use a syringe to draw approximately 2.5 g of sample onto the weighing pan and use a PTFE scraper to level the sample. Close the top cover and wait for the reading to stabilize before pressing the "Start" button to begin the test. When the sample reaches a constant weight at 150℃ (remaining constant for 70 s), the moisture analyzer will automatically stop heating and emit a beep. Record the test data.

[0097] Viscosity testing method (instrument model: DV2TLV, Bollefeld, USA):

[0098] Turn on the power to the thermostat bath and raise the oil temperature to 25°C, maintaining this temperature (temperature fluctuation should not exceed ±0.2°C). Pour approximately 350 g of the sample to be tested into a clean, dry measuring cup, seal it with a rubber stopper fitted with a thermometer, and then place it in the thermostat bath to heat the sample to 25°C (stirring approximately every 5 minutes to ensure uniform concentration and temperature), then maintain this temperature for 10 minutes before testing. Measure the viscosity of the sample at 25°C using a digital viscometer. Use a 64# rotor at a speed of 30 RPM. The test duration is 3 minutes, and data acquisition lasts for 2 minutes.

[0099] Swelling test method:

[0100] Swelling test: Take 1.0g of solid adhesive and spread it on a 50mm thick surface. In a 50mm film-forming mold, the film was dried in a forced-air oven at 60℃ for 12 hours to solidify (to prevent air bubbles), resulting in a uniform and flat film. A square film with a side length of 1cm was cut off. The film was cut before it was fully solidified during baking and dried at 105℃ and a vacuum of ~0.095MPa for 4 hours until its weight no longer decreased, resulting in an absolutely dry film. It was weighed in a drying chamber (25℃, humidity ≤0.5%) and recorded as M1. The film was placed in an aluminum-plastic film bag containing electrolyte and heat-sealed. After being placed in a 70℃ oven for 1 day, the film was unsealed and removed in the drying chamber. The residual electrolyte on the film surface was gently absorbed with dry filter paper until the filter paper was no longer wetted, and then weighed and recorded as M2. The electrolyte swelling degree (Swelling) was:

[0101] Swelling=(M2-M1) / M1×100%.

[0102] Dissolution test:

[0103] Take 1.0g of solid adhesive and spread it on a 50mm thick surface. In a 50mm film-forming mold, the film was dried in a forced-air oven at 60℃ for 12 hours to solidify (to prevent air bubbles), resulting in a uniform and flat film. Square films with sides of 1cm were cut off. The film was cut before complete solidification during baking and dried at 105℃ and a vacuum of ~0.095MPa for 4 hours until its weight no longer decreased, resulting in an absolutely dry film. This film was weighed in a drying chamber (25℃, humidity ≤0.5%) and recorded as M1. It was then placed in an aluminum-plastic film bag containing ethyl methyl carbonate (EMC) and heat-sealed. After being kept in a 70℃ oven for 3 days, the film was unsealed in the drying chamber and placed in an oven at 115℃ and a vacuum below 0.095MPa for 2 hours. It was then removed and cooled to room temperature in a desiccator, and its weight was recorded as M3. The electrolyte dissolution (Dissol.) was:

[0104] Dissol=(M1-M3) / M1×100%.

[0105] The test results are shown in Table 1.

[0106] Table 1

[0107]

[0108] As can be seen, the binder of this invention achieves a compaction density comparable to commercial PVDF, and its elongation at break is higher than that of commercial PVDF and polyacrylonitrile binders. It also exhibits good flexibility and high adhesive strength. Furthermore, its swelling degree in electrolyte and its dissolution rate in solvent are significantly lower than those of the blended binder in Comparative Example 1, indicating that it has good electrolyte resistance.

Claims

1. A lithium-ion battery non-fluorinated cathode binder, characterized in that: The copolymers include copolymers whose polymerizing monomers include acrylonitrile monomers, acrylate monomers, acrylamide monomers, and thiourea / urea monomers.

2. The lithium-ion battery non-fluorinated cathode binder of claim 1, wherein: By weight, 78-95 parts of acrylonitrile monomers, 1-10 parts of acrylate monomers, 2-15 parts of acrylamide monomers, and 1-30 parts of thiourea / urea monomers.

3. The lithium-ion battery non-fluorinated cathode binder of claim 1, wherein: Acrylonitrile monomers include acrylonitrile or methacrylonitrile; The structure of the acrylate monomer is: CH2=CR 1 -COOR 2 , wherein R 1  is -H or -CH3, and R 2  is an alkyl group or a cycloalkyl group; The structure of acrylamide monomer is: CH2=CR 3 CONHR 4 , wherein R 3  is -H or -CH3, R 4  is -H; alkyl; cycloalkyl or aromatic group; Thiourea / urea monomers are polymerized from biepoxides, sulfur-containing carbonyl / carbonyl compounds, and amines; the number average molecular weight of thiourea / urea monomers ranges from 400 to 100,000.

4. The lithium-ion battery non-fluorinated cathode binder of claim 3, wherein: The acrylate monomers are at least one of methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, n-hexyl acrylate, and 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, and 2-ethylhexyl methacrylate; the acrylamide monomers are at least one of acrylamide, N-methylacrylamide, N-ethylacrylamide, N-butylacrylamide, and 2-methylacrylamide.

5. The non-fluorinated positive electrode binder for lithium-ion batteries according to claim 3, characterized in that: The bis-epoxide compounds include ; ; ; or ; Sulphydryl / carbonyl containing compounds include any of the following monomers: ； ； ； ； ； ； ； ； ； ； ； ； ； ； S+ ；S+ ；S+ ；S+ ；S+ ；S+ ； The amine compound is one or both of the following monomers: n1 is an integer from 1 to 10; n2 is an integer from 1 to 10; ； ； ； n3 is an integer from 1 to 10; ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； n4 is an integer from 2 to 68; m2 is an integer from 9 to 39; mi and m3 are integers greater than 0 and 3 < mi + m3 < 6; n5 is an integer from 5 to 88; n6 is an integer from 1 to 20; n7 is an integer from 1 to 20; n8 is an integer from 1 to 20; ； ； ； ； ； 。 6. The lithium-ion battery non-fluorinated cathode binder of claim 5, wherein: The molar ratio of biepoxides, sulfur-containing carbonyl / carbonyl compounds, and amines is 1:3 to 5:

1.

7. The lithium-ion battery non-fluorinated cathode binder of claim 6, wherein: The molar ratio of biepoxides, sulfur-containing carbonyl / carbonyl compounds, and amines is 1:4:

1.

8. The lithium-ion battery non-fluorinated cathode binder of claim 7, wherein: Thiourea-based / urea-based polymers were prepared using the following method: A biepoxide compound, a sulfur-containing carbonyl / carbonyl compound, and an amine compound were added to a solvent and mixed. The mixture was reacted for 10–30 h to obtain product 1. After drying product 1, it was dissolved in a solvent. Then, triethylamine, methacryloyl chloride, and the catalyst 4-dimethylaminopyridine were added and reacted for 10–30 h. The reaction product was purified and dried to obtain thiourea / urea monomers.

9. The non-fluorinated positive electrode binder for lithium-ion batteries according to claim 8, characterized in that: The mass ratio of product 1, triethylamine, and methacryloyl chloride is 1–5:2:2; the catalyst is 4-dimethylaminopyridine; the amount of catalyst used is 0.05–0.2 mol.

10. The non-fluorinated positive electrode binder for lithium-ion batteries according to any one of claims 1 to 7, characterized in that: The polymer monomer also includes additives, which include at least one of chain transfer agents, emulsifiers, and dispersants.

11. The non-fluorinated positive electrode binder for lithium-ion batteries according to any one of claims 1 to 7, characterized in that: It also includes a solvent, wherein the solvent is NMP.

12. A lithium-ion battery positive electrode sheet, comprising a positive electrode material and a binder, characterized in that: The adhesive is the non-fluorinated positive electrode adhesive for lithium-ion batteries according to any one of claims 1 to 11.

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