A kind of lithium battery hot foaming tape and preparation method thereof

Abstract

The invention discloses a lithium battery hot foaming tape and a preparation method thereof, and belongs to the technical field of tapes. Soft monomers, hard monomers, auxiliary agents, initiators and solvents are weighed, and a solution polymerization method is adopted to prepare a pressure-sensitive adhesive solution; expanded microspheres are added to the pressure-sensitive adhesive solution, a cross-linking agent is added, and the solution is stirred to obtain a coating solution; the coating solution is coated on the surface of a polyethylene substrate, dried, and then a double-sided silicone-coated polyester release film is compounded to obtain a lithium battery hot foaming tape. The auxiliary agent has good compatibility with the other raw materials, and there is a chemical reaction with the soft monomer and the hard monomer. Therefore, the auxiliary agent containing chitosan, triazine structure and hindered amine structure can be stably present in the foaming tape. Under the joint action of the auxiliary agent and the other raw materials, the hot foaming tape of the present invention has excellent and stable anti-aging effect and antibacterial effect, so that the hot foaming tape can maintain good bonding performance and mechanical properties for a long time. At the same time, the hot foaming tape of the present invention is easy to detach when used in the field of lithium batteries, and no residual glue will appear.

Description

Technical Field

[0001] The present invention belongs to the technical field of adhesive tapes, and in particular, relates to a lithium battery thermal foaming adhesive tape and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are rechargeable batteries that are widely used in portable fields such as mobile phones and notebooks due to their high operating voltage, small size, light weight, high energy, no memory effect, low self-discharge, and long cycle life. Compared with nickel-chromium batteries, lithium batteries have greatly reduced environmental pollution because they do not contain heavy metal cadmium.

[0003] At present, the cathode and anode of lithium battery are produced by coating. The coating slurry is a molten polymer or polymer solution, and the coating substrate is a metal film, generally copper foil or aluminum foil. The foam tape temporarily fixes and protects the metal substrate during the coating process. After being heated, it foams and separates. It is required to be easy to peel off, without residual glue, and without causing damage to the adhered substrate.

[0004] Chinese patent CN106366964A discloses an easy-to-detach high-removal rate foam tape, comprising a tape base layer, a film layer and an isolation layer arranged from top to bottom, wherein the film layer comprises 20-70% by mass of a high molecular polymer glue and 30-80% by mass of heat-expandable microcapsules. Although the foam tape is easy to detach, it has poor anti-aging performance. Therefore, as time goes by and environmental conditions change, the foam tape will experience a decrease in bonding performance and mechanical properties, and its service life will be greatly reduced. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the prior art and provide a lithium battery thermal foaming tape and a preparation method thereof.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for preparing a lithium battery thermal foaming tape comprises the following steps:

[0008] (1) Mix soft monomer, hard monomer, auxiliary agent and solvent in parts by weight to obtain a premix; take 20-40% of the premix, stir and heat to 70-80°C, add 25-35% of initiator, stir for 30-60 minutes to obtain a bottom phase mixture; stir the remaining initiator and the remaining premix to obtain a standby mixed solution; heat the bottom phase mixture to 75-85°C, then dropwise add the standby mixed solution, add the solution over 4 hours, continue to keep warm and stir for 8-10 hours, cool and filter the material with a 200-mesh filter to obtain a pressure-sensitive adhesive solution;

[0009] (2) Add the expanded microspheres to the pressure-sensitive adhesive solution, stir for 1 hour, add the crosslinking agent after mixing evenly, and continue stirring for another hour to mix evenly to obtain a coating solution;

[0010] (3) Placing the polyethylene substrate on the unwinding unit of a solvent-based heated coating machine, coating the coating liquid on the surface of the polyethylene substrate, baking in a drying oven at 30-50° C. for 20-30 min, and then laminating with a double-sided silicone-coated polyethylene terephthalate release film to prepare a lithium battery thermal foaming tape.

[0011] Furthermore, the step (1) comprises 70-80 parts of soft monomer, 5-20 parts of hard monomer, 3-6 parts of auxiliary agent, 0.1-0.2 parts of initiator and 60-70 parts of solvent.

[0012] Furthermore, in step (2), the mass ratio of the pressure-sensitive adhesive, the expanded microspheres and the cross-linking agent is 60-80:20-40:1-2.

[0013] Furthermore, the soft monomer is one or more of hydroxyethyl acrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxypropyl acrylate.

[0014] Furthermore, the hard monomer is one or more of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, acrylamide, and vinyl acetate.

[0015] Furthermore, the auxiliary agent is prepared by the following steps:

[0016] S1. Add trimethylolpropane triacrylate, DBU (1,8-diazobisspiro[5.4.0]undec-7-ene) and deionized water into a three-necked flask, stir evenly, then slowly add 2,2,6,6-tetramethylpiperidinamine, heat to 60°C and react for 24 hours after the addition is completed, cool to room temperature after the reaction is completed, and distill under reduced pressure to obtain intermediate 1; the dosage ratio of 2,2,6,6-tetramethylpiperidinamine, trimethylolpropane triacrylate, DBU and deionized water is 15.4mL:25.9mL:0.4g:120mL;

[0017] Under the catalytic action of DBU, the molar ratio of 2,2,6,6-tetramethylpiperidinamine to trimethylolpropane triacrylate is controlled to be 1:1.05-1.1, and 2,2,6,6-tetramethylpiperidinamine and trimethylolpropane triacrylate undergo Michael addition reaction. The reaction process is as follows:

[0018]

[0019] S2, adding intermediate 1, cyanuric chloride and chloroform into a three-necked flask, stirring to dissolve, and then slowly adding 10wt% sodium bicarbonate solution, after the addition is completed, the temperature is controlled at 0-5°C and stirred to react for 8h, after the reaction is completed, deionized water is added and shaken, and then allowed to stand for stratification, the aqueous phase is separated and the pH is measured until the pH of the aqueous phase is neutral, and then the organic phase is dried with anhydrous magnesium sulfate, filtered, and the filtrate is distilled under reduced pressure to obtain intermediate 2; the molar ratio of cyanuric chloride to intermediate 1 is 1:1.05-1.1;

[0020] Sodium bicarbonate is used as an acid-binding agent, and the -NH- of intermediate 1 and the -Cl of cyanuric chloride undergo a nucleophilic substitution reaction. The reaction process is as follows:

[0021]

[0022] S3. In a brown three-necked flask under nitrogen protection, resorcinol, anhydrous aluminum chloride and chloroform were added in sequence, stirred evenly, and then intermediate 2 was added, followed by stirring and heating to 110°C, and the reaction was kept warm for 12 hours. After the reaction was completed, the reaction mixture was slowly poured into ice water, solids were precipitated, filtered, and then recrystallized with 80% methanol aqueous solution to obtain intermediate 3; the dosage ratio of intermediate 2, resorcinol, anhydrous aluminum chloride and chloroform was 35.2g:7mL:0.4g:180mL;

[0023] The molar ratio of intermediate 2 to resorcinol is controlled to be 1:1.2-1.4, and intermediate 2 and resorcinol undergo Friedel-Crafts acylation reaction under the catalysis of anhydrous aluminum chloride. The reaction process is as follows:

[0024]

[0025] S4. Dissolve chitosan in DMF (N,N-dimethylformamide) under nitrogen protection, add the mixed solution of intermediate 3 and DMF after stirring evenly, and then heat to 50°C and stir to react for 6 hours. During this period, adjust the pH value of the system to 7 with 10wt% sodium carbonate solution. After the reaction is completed, cool to room temperature, wash with deionized water by centrifugation for 3 times, then wash with anhydrous ethanol by centrifugation for 3 times, and finally dry at 80°C for 12 hours to obtain an auxiliary agent; the amount ratio of chitosan to intermediate 3 is 20g:9g.

[0026] Under heating conditions, the -OH of chitosan and the -Cl of intermediate 3 undergo substitution reaction, and the reaction process is as follows:

[0027]

[0028] The triazine structure in the additive can strongly absorb ultraviolet rays of 280nm-400nm. In addition, the triazine structure has the advantages of high efficiency, high temperature resistance, light color and good compatibility. Therefore, the additive can effectively protect the foam tape from ultraviolet aging. The hindered amine structure in the additive achieves light protection by capturing free radicals, decomposing hydroperoxides, quenching singlet oxygen and capturing heavy metal ions. The triazine structure and the hindered amine structure work together to make the additive have excellent anti-aging effects, so that the foam tape is not easy to harden and powder, and the bonding performance and mechanical properties can be maintained for a long time.

[0029] The additive also contains chitosan, which is a deacetylated product of the natural polysaccharide chitin and has rich amino groups on its surface. Chitosan mainly interacts with the cell wall of bacteria to destroy the cell membrane, thereby killing bacteria. It has a broad-spectrum antibacterial property. Therefore, the additive can make the foam tape less susceptible to contamination by bacteria and molds, thereby maintaining the adhesive performance for a long time and greatly extending the service life. In addition, the adhesiveness of chitosan decreases with increasing temperature, which makes the foam tape of the present invention easy to detach when used in the field of lithium batteries without residual adhesive.

[0030] The multiple acrylate groups in the additive can produce chemical reactions with the soft monomer and the hard monomer under the initiator. On the one hand, this increases the secondary force between the molecules in the pressure-sensitive adhesive liquid, thereby making the foam tape have good bonding properties. On the other hand, it allows the additive to stably exist in the foam tape, making it difficult to migrate and fall out, and can exert excellent anti-aging and antibacterial effects for a long time.

[0031] Furthermore, the initiator is one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile, and benzoyl peroxide.

[0032] Furthermore, the solvent is one or more of ethyl acetate, methanol and toluene.

[0033] Furthermore, the cross-linking agent is one or more of toluene diisocyanate-trimethylolpropane, hexamethylene diisocyanate, and aluminum acetylacetonate.

[0034] The invention also discloses a lithium battery hot foaming tape, which is prepared according to the preparation method of the lithium battery hot foaming tape.

[0035] The beneficial effects of the present invention are as follows: the auxiliary agent has good compatibility with other raw materials, and has chemical effects with soft monomers and hard monomers. Therefore, the auxiliary agent containing chitosan, triazine structure and hindered amine structure can stably exist in the foam tape. Under the joint action of the auxiliary agent and other raw materials, the hot foam tape of the present invention has excellent and stable anti-aging and antibacterial effects, so that the hot foam tape can maintain good bonding properties and mechanical properties for a long time. At the same time, the hot foam tape of the present invention is easy to detach when used in the field of lithium batteries, and no residual glue will appear. DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] Example 1: Preparation of auxiliary agent, the specific steps are as follows:

[0038] S1, add 25.9 mL of trimethylolpropane triacrylate, 0.4 g of DBU and 120 mL of deionized water into a three-necked flask, stir evenly, then slowly add 15.4 mL of 2,2,6,6-tetramethylpiperidinamine, after the addition is complete, heat to 60 ° C and react for 24 hours, cool to room temperature after the reaction is completed, and distill under reduced pressure to obtain intermediate 1;

[0039] S2, 40.1g of intermediate 1, 15.7g of cyanuric chloride and 200mL of chloroform were added to a three-necked flask, stirred to dissolve, and then 30mL of 10wt% sodium bicarbonate solution was slowly added. After the addition was completed, the temperature was controlled at 0-5°C and stirred for 8h. After the reaction was completed, deionized water was added and shaken, and then allowed to stand for stratification. The aqueous phase was separated and the pH was measured until the pH of the aqueous phase was neutral. The organic phase was then dried over anhydrous magnesium sulfate, filtered, and the filtrate was distilled under reduced pressure to obtain intermediate 2;

[0040] S3. In a brown three-necked flask, 7 mL of resorcinol, 0.4 g of anhydrous aluminum chloride and 180 mL of chloroform were added in sequence under nitrogen protection. After stirring, 35.2 g of intermediate 2 was added. The mixture was heated to 110° C. with stirring and kept for 12 h. After the reaction was completed, the reaction mixture was slowly poured into ice water to precipitate a solid, which was filtered and then recrystallized with 80% methanol aqueous solution to obtain intermediate 3.

[0041] S4. Dissolve 20g chitosan in 200mLDMF under nitrogen protection, stir evenly, add 9g mixed solution of intermediate 3 and 40mLDMF, and then heat to 50℃ and stir for 6h. During this period, adjust the pH value of the system to 7 with 10wt% sodium carbonate solution. After the reaction, cool to room temperature, wash with deionized water for 3 times by centrifugation, wash with anhydrous ethanol for 3 times by centrifugation, and finally dry at 80℃ for 12h to obtain the auxiliary agent.

[0042] Example 2: Preparation of auxiliary agent, the specific steps are as follows:

[0043] The remaining steps remain unchanged, and only step S4 of Example 1 is removed to prepare the auxiliary agent.

[0044] Example 3: Preparation of lithium battery thermal foaming tape, the specific steps are as follows:

[0045] (1) 70 parts of hydroxyethyl acrylate, 5 parts of acrylic acid, 3 parts of the auxiliary agent prepared in Example 1 and 60 parts of ethyl acetate were mixed uniformly by weight to obtain a premixture; 20% of the premixture was stirred and heated to 70°C, 0.025 parts of azobisisobutyronitrile were added, and stirred for 30 minutes to obtain a bottom phase mixture; 0.075 parts of azobisisobutyronitrile and the remaining premixture were stirred uniformly to obtain a standby mixed solution; the bottom phase mixture was heated to 75°C, and then the standby mixed solution was added dropwise, and the addition was completed within 4 hours, and the mixture was kept warm and stirred for 8 hours. After cooling, the material was filtered through a 200-mesh filter to obtain a pressure-sensitive adhesive solution with a solid content of 40%;

[0046] (2) Add Matsumoto F-20 to the pressure-sensitive adhesive solution, stir for 1 hour, and then add hexamethylene diisocyanate after mixing evenly. The mass ratio of the pressure-sensitive adhesive solution, the expanded microspheres, and the cross-linking agent is 60:20:1. Continue stirring for another hour to mix evenly to obtain a coating solution.

[0047] (3) Placing the polyethylene substrate on the unwinding unit of a solvent-based heated coating machine, coating the coating liquid on the surface of the polyethylene substrate, baking in a drying oven at 30°C for 30 minutes, and then laminating with a double-sided silicone-coated polyethylene terephthalate release film to prepare a lithium battery thermal foaming tape.

[0048] Example 4: Preparation of lithium battery thermal foaming tape, the specific steps are as follows:

[0049] (1) 76 parts of 2-ethylhexyl acrylate, 15 parts of methyl methacrylate, 5 parts of the auxiliary agent prepared in Example 1, 22 parts of ethyl acetate, 22 parts of methanol, and 24 parts of toluene were mixed uniformly by weight to obtain a premixture; 30% of the premixture was stirred and heated to 75°C, 0.045 parts of azobisisoheptanitrile were added, and stirred for 40 minutes to obtain a bottom phase mixture; 0.105 parts of azobisisoheptanitrile and the remaining premixture were stirred uniformly to obtain a standby mixed solution; the bottom phase mixture was heated to 78°C, and then the standby mixed solution was added dropwise, and the addition was completed within 4 hours, and the mixture was kept warm and stirred for 9 hours. After cooling, the material was filtered through a 200-mesh filter to obtain a pressure-sensitive adhesive solution with a solid content of 44%;

[0050] (2) Add Matsumoto F-36 to the pressure-sensitive adhesive solution, stir for 1 hour, and then add aluminum acetylacetonate after mixing evenly. The mass ratio of the pressure-sensitive adhesive solution, the expanded microspheres, and the cross-linking agent is 70:30:1.7. Continue stirring for another hour to mix evenly to obtain a coating solution.

[0051] (3) Placing the polyethylene substrate on the unwinding unit of a solvent-based heated coating machine, coating the coating liquid on the surface of the polyethylene substrate, baking in a drying oven at 40°C for 26 minutes, and then laminating with a double-sided silicone-coated polyethylene terephthalate release film to prepare a lithium battery thermal foaming tape.

[0052] Example 5: Preparation of lithium battery thermal foaming tape, the specific steps are as follows:

[0053] (1) 40 parts of butyl methacrylate, 40 parts of 2-hydroxypropyl acrylate, 10 parts of methyl acrylate, 10 parts of vinyl acetate, 6 parts of the auxiliary agent prepared in Example 1, 40 parts of ethyl acetate, 20 parts of methanol and 10 parts of toluene were mixed uniformly by weight to obtain a premixture; 40% of the premixture was stirred and heated to 80°C, 0.07 parts of benzoyl peroxide were added, and stirred for 30-60 minutes to obtain a bottom phase mixture; 0.13 parts of benzoyl peroxide and the remaining premixture were stirred uniformly to obtain a standby mixed solution; the bottom phase mixture was heated to 85°C, and then the standby mixed solution was added dropwise, and the addition was completed within 4 hours, and the mixture was kept warm and stirred for 10 hours. After cooling, the material was filtered out with a 200-mesh filter to obtain a pressure-sensitive adhesive solution with a solid content of 45%;

[0054] (2) Add Matsumoto F-48 to the pressure-sensitive adhesive solution, stir for 1 hour, and then add toluene diisocyanate-trimethylolpropane after mixing evenly, wherein the mass ratio of the pressure-sensitive adhesive solution, the expanded microspheres and the cross-linking agent is 80:40:2, and continue stirring for another hour to mix evenly to obtain a coating solution;

[0055] (3) Placing the polyethylene substrate on the unwinding unit of a solvent-based heated coating machine, coating the coating liquid on the surface of the polyethylene substrate, baking in a 50°C oven for 20 min, and then laminating with a double-sided silicone-coated polyethylene terephthalate release film to prepare a lithium battery thermal foaming tape.

[0056] Comparative Example 1: Preparation of lithium battery thermal foaming tape, the specific steps are as follows:

[0057] The remaining steps remain unchanged, and the auxiliary agent in Example 3 is replaced by the auxiliary agent prepared in Example 2, thereby preparing a lithium battery thermal foaming tape.

[0058] Comparative Example 2: Preparation of lithium battery thermal foaming tape, the specific steps are as follows:

[0059] The remaining steps remain unchanged, and the auxiliary agent in Example 3 is replaced by 1.5 parts of ultraviolet absorber UV-9 and 1.5 parts of light stabilizer 744, thereby preparing a lithium battery thermal foaming tape.

[0060] Comparative Example 3: Preparation of lithium battery thermal foaming tape, the specific steps are as follows:

[0061] The remaining steps remain unchanged, and the auxiliary agent in Example 3 is removed to prepare a lithium battery thermal foaming tape.

[0062] Performance test: The lithium battery thermal foaming tapes prepared in Examples 3-5 and Comparative Examples 1-3 were subjected to the following performance tests, and the test results are as follows:

[0063] 1. Initial adhesion: According to GB / T4852-2002 "Test method for initial adhesion of pressure-sensitive adhesive tape (rolling ball method)", the rolling ball slope stop test is used for testing (the measuring angle is 20°), and the initial adhesion of the lithium battery thermal foam tape is evaluated according to the maximum steel ball size that can be adhered to the adhesive surface of the specified length. The larger the steel ball particle size, the greater the initial adhesion performance of the lithium battery thermal foam tape;

[0064] Judgment criteria: Excellent: steel ball size > 28, Good: 25 ≤ steel ball size ≤ 28, Good: 20 ≤ steel ball size ≤ 25, Fair: 15 ≤ steel ball size ≤ 20, Poor: steel ball size < 15;

[0065] 2. Stickiness: measured according to the method of GB / T4851-2014, the lithium battery thermal foam tape in the embodiment was cut into a rectangle with a width of 25 mm and a length of 100 mm, and attached to a hard board of the same material, with the upper end aligned with the standard line, and the excess part of the lower end was cut off. After rolling back and forth 3 times with a 2kg roller, after leaving it for a period of time, the hard board with the sample was vertically hung on the test frame to prevent it from shaking, and a 1kg weight was hung below. The time it took for the tape to fall represented the stickiness of the lithium battery thermal foam tape;

[0066] The lithium battery thermal foaming tapes prepared in Examples 3-5 and Comparative Examples 1-3 were placed in an ultraviolet lamp aging test box, and ultraviolet accelerated aging test (PCT aging) was performed according to the method described in ISO4892.3. The test conditions were as follows: light source, UVA-340; radiation energy, 0.83 W / (m 2 ﹒ nm); test temperature, 70℃; light on for 4 hours, turn off the light for 1 hour, cycle test for 50 hours, and test the stickiness again in the same way;

[0067] The lithium battery thermal foaming tapes prepared in Examples 3-5 and Comparative Examples 1-3 were aged at 110° C. for 72 h (thermal aging), and the adhesiveness was tested again in the same manner;

[0068] Judgment criteria: Excellent: drop time > 90h, Good: 80h≤drop time≤90h, Good: 60h≤drop time≤80h, General: 40h≤drop time≤60h, Poor:drop time <40h;

[0069] 3. Residual adhesive: After aging for 60 days in an environment of 110°C and 90% humidity, the residual adhesive of the lithium battery thermal foaming tapes prepared in Examples 3-5 and Comparative Examples 1-3 was evaluated when peeled off after aging:

[0070]

[0071] In the description of the specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0072] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for preparing a lithium battery thermal foaming tape, characterized in that: The following steps are involved: (1) Mix soft monomer, hard monomer, auxiliary agent and solvent according to weight to obtain a premix; take 20-40% of the premix, heat it to 70-80°C, add 25-35% of initiator, and stir to obtain a bottom phase mixture; stir the remaining initiator and the remaining premix to obtain a standby mixed solution; heat the bottom phase mixture to 75-85°C, add the standby mixed solution dropwise, add it over 4 hours, stir, cool, and filter to obtain a pressure-sensitive adhesive solution; (2) adding the expanded microspheres into the pressure-sensitive adhesive solution, adding the cross-linking agent, and stirring to obtain the coating solution; (3) coating the coating liquid on the polyethylene substrate surface, drying at 30-50° C., and then compounding with a double-sided silicone-coated polyethylene terephthalate release film to obtain a lithium battery thermal foaming tape; Wherein, the auxiliary agent is prepared by the following steps: S1. Add trimethylolpropane triacrylate, 1,8-diazobisspiro[5.4.0]undec-7-ene and deionized water into a flask, add 2,2,6,6-tetramethylpiperidinamine with stirring, react at 60° C. for 24 h, and distill under reduced pressure to obtain intermediate 1; the amount ratio of 2,2,6,6-tetramethylpiperidinamine, trimethylolpropane triacrylate, 1,8-diazobisspiro[5.4.0]undec-7-ene and deionized water is 15.4 mL:25.9 mL:0.4 g:120 mL; S2, adding intermediate 1, cyanuric chloride and chloroform into a flask, adding 10wt% sodium bicarbonate solution with stirring, reacting at 0-5°C for 8h, adding deionized water, layering, measuring pH, taking the organic phase to dry, filtering, and distilling the filtrate under reduced pressure to obtain intermediate 2; the molar ratio of cyanuric chloride to intermediate 1 is 1:1.05-1.1; S3. Add resorcinol, anhydrous aluminum chloride and chloroform into a flask, add intermediate 2 with stirring, react at 110° C. for 12 h, pour into ice water, precipitate, filter, and recrystallize to obtain intermediate 3; the dosage ratio of intermediate 2, resorcinol, anhydrous aluminum chloride and chloroform is 35.2 g:7 mL:0.4 g:180 mL; S4. Dissolve chitosan in DMF, add intermediate 3 and DMF, react at 50°C for 6h, cool, wash, and dry to obtain an auxiliary agent; the dosage ratio of chitosan to intermediate 3 is 20g:9g.

2. The method for preparing a lithium battery thermal foaming tape according to claim 1, characterized in that: The step (1) comprises 70-80 parts of soft monomer, 5-20 parts of hard monomer, 3-6 parts of auxiliary agent, 0.1-0.2 parts of initiator and 60-70 parts of solvent.

3. The method for preparing a lithium battery thermal foaming tape according to claim 1, characterized in that: In the step (2), the mass ratio of the pressure-sensitive adhesive solution, the expanded microspheres and the cross-linking agent is 60-80:20-40:1-2.

4. The method for preparing a lithium battery thermal foaming tape according to claim 2, characterized in that: The soft monomer is one or more of hydroxyethyl acrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and 2-hydroxypropyl acrylate.

5. The method for preparing a lithium battery thermal foaming tape according to claim 2, characterized in that: The hard monomer is one or more of acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, acrylamide and vinyl acetate.

6. The method for preparing a lithium battery thermal foam tape according to claim 2, characterized in that: The initiator is one or more of azobisisobutyronitrile, azobisisovaleronitrile, azobisisoheptanenitrile and benzoyl peroxide.

7. The method for preparing a lithium battery thermal foaming tape according to claim 2, characterized in that: The solvent is one or more of ethyl acetate, methanol and toluene.

8. The method for preparing a lithium battery thermal foaming tape according to claim 3, characterized in that: The cross-linking agent is one or more of toluene diisocyanate-trimethylolpropane, hexamethylene diisocyanate, and aluminum acetylacetonate.

9. A lithium battery thermal foaming tape, characterized in that: The lithium battery thermal foaming tape is prepared according to the preparation method of any one of claims 1 to 8.

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