High-flexibility electrolyte-resistant terminal adhesive tape and preparation method thereof

Abstract

The application provides a high-flexibility electrolyte-resistant termination adhesive tape and a preparation method thereof. The termination adhesive tape comprises, from bottom to top, a non-silicon release agent coating layer, a PET substrate layer and an acrylic pressure-sensitive adhesive. The preparation raw material of the acrylic pressure-sensitive adhesive comprises the following components in parts by weight: modified polyacrylic acid resin 50-100 parts, curing agent 1-10 parts, functional additive 1-10 parts, pigment 1-5 parts and solvent 50-100 parts. The termination adhesive tape prepared by the application has the advantages of high viscosity, good flexibility, electrolyte corrosion resistance, high temperature resistance and the like, and can be better insulated and fixed at the termination position of a battery cell, thereby preventing contact short circuit, improving the service life and safety of the battery.

Description

Technical Field

[0001] This invention belongs to the field of adhesive tape technology, and particularly relates to a highly flexible, electrolyte-resistant termination tape and its preparation method. Background Technology

[0002] Termination tape is a key auxiliary material in battery manufacturing. It is mainly used to fix the wound cell electrodes, separators and tabs to prevent short circuit risks caused by electrolyte penetration.

[0003] With the explosive growth of the electric vehicle, consumer electronics, and energy storage industries, the demand for termination tape has surged, but its technological bottlenecks are also becoming increasingly prominent. Traditional termination tapes use BOPP / PET as the base material and acrylic adhesive as the bonding layer. Although they have low cost and easy processing, the adhesive layer is prone to softening, swelling, and even detachment under long-term immersion in the strong polar solvent of the electrolyte. This leads to diaphragm displacement, increased internal resistance, and ultimately causes battery short circuits or thermal runaway. Furthermore, the termination tapes in the existing technology have poor flexibility, are not easy to fit complex shapes, and have poor adaptability to battery deformation, making them prone to cracking and detachment.

[0004] To address the problems existing in the prior art, how to provide a highly flexible termination tape that is resistant to electrolyte corrosion is a problem that this invention urgently needs to solve. Summary of the Invention

[0005] The purpose of this invention is to provide a highly flexible, electrolyte-resistant termination tape and its preparation method, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides a highly flexible, electrolyte-resistant termination tape, wherein the termination tape comprises, from bottom to top: a non-silicone release agent coating, a PET substrate layer, and an acrylic pressure-sensitive adhesive; the raw materials for preparing the acrylic pressure-sensitive adhesive include the following components in parts by weight: 50-100 parts of modified polyacrylic acid resin, 1-10 parts of curing agent, 1-10 parts of functional additives, 1-5 parts of pigment, and 50-100 parts of solvent; The functional additive is a modified polyphosphazene.

[0007] As a further improvement, the synthesis of the modified polyacrylic acid resin includes the following steps: (1) Add acrylate monomer, emulsifier, crosslinking agent and solvent to the flask, stir and mix evenly to obtain a pre-emulsion; (2) Add water, initiator and part of the pre-emulsion obtained in step (1) into a flask, heat to 50-70℃ and stir to react. Then slowly add the remaining pre-emulsion and initiator over 2-4 hours, and heat to 70-90℃ to keep the temperature for reaction. After the reaction is complete, cool down to 40-50℃, add pH adjuster to adjust the reaction system to neutral, add plasticizer, continue stirring and mixing, filter and discharge to obtain modified polyacrylic acid resin.

[0008] Preferably, the acrylate monomer is methyl methacrylate, 2-ethylhexyl acrylate, isooctyl acrylate, and vinyl acetate; the emulsifier is allyloxyisomeric alcohol ether sulfate ammonium salt; the crosslinking agent is N-hydroxymethylacrylamide; and the initiator is benzoyl peroxide.

[0009] As a further improvement, the plasticizer is di(2-butoxyethyl) phthalate.

[0010] As a further improvement, the added mass of the plasticizer is 2-8% of the total mass of the acrylate monomers.

[0011] As a further improvement, the preparation method of the modified polyphosphazene includes the following steps: (1) Under a nitrogen atmosphere, hexachlorocyclotriphosphazene, catalyst and organic solvent were added to a round-bottom flask and heated to reflux. When the reaction system became viscous, the heating was stopped and the product was post-processed to obtain polyphosphazene intermediate. (2) Under a nitrogen atmosphere, p-methylphenol and a strong base were added to a round-bottom flask and stirred at room temperature. After the reaction was completed, the mixture was slowly poured into a mixture of the polyphosphazene intermediate obtained in step (1) and an organic solvent. The mixture was heated and refluxed. After the reaction was completed, the mixture was cooled to room temperature and then post-treated to obtain modified polyphosphazene.

[0012] Preferably, the catalyst is aminosulfonic acid and calcium sulfate dihydrate; the strong base is sodium hydride.

[0013] As a further improvement, the amount of modified polyphosphazene added is 2wt%-6wt% of the amount of modified polyacrylic acid resin added.

[0014] As a further improvement, the curing agent is at least one of isocyanate curing agents and imidazole curing agents.

[0015] For better curing effect, the curing agent is preferably an isocyanate-based curing agent.

[0016] As a further improvement, the pigment is blue ink.

[0017] As a further improvement, the solvent is at least one selected from isobutanol, ethyl acetate, tetrahydrofuran, and N,N-dimethylformamide.

[0018] For better reaction results, the solvent is preferably ethyl acetate.

[0019] On the other hand, the present invention also provides a method for preparing a highly flexible, electrolyte-resistant termination tape, characterized by comprising the following steps: (1) According to the weight parts, the modified acrylic resin, pigment and solvent are heated and stirred to mix, and then the curing agent and functional additives are added and stirred to obtain acrylic pressure-sensitive adhesive. (2) Apply acrylic pressure-sensitive adhesive evenly to the PET substrate, dry and shape it, then apply non-silicone release agent evenly to the other side of the PET substrate, then perform curing and shaping, and roll up and cut to obtain a highly flexible and electrolyte-resistant termination tape.

[0020] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a highly flexible, electrolyte-resistant termination tape and its preparation method. The resulting termination tape has high viscosity and low elastic modulus, indicating good adhesion and high flexibility. When applied to the termination part of a battery cell, it can better fix the chip and suppress short circuits caused by displacement due to charging and discharging vibrations. In electrolyte testing, it showed no peeling or fading, indicating good resistance to electrolyte corrosion, which can extend battery life and improve safety. At high temperatures, it left no residue, indicating good high-temperature resistance. The acrylic pressure-sensitive adhesive components will not decompose or undergo chemical changes due to high temperatures, thus ensuring the overall stability of the tape's performance. In the preparation process of the termination tape of the present invention, by adding modified polyphosphazene, the heat resistance and corrosion resistance of acrylic pressure-sensitive adhesive can be improved, thereby further improving the electrolyte corrosion resistance and high temperature resistance of the termination tape, preventing battery electrolyte leakage or penetration, thus ensuring the safety and reliability of the battery. To a certain extent, it can work synergistically with the plasticizer in the modified polyacrylic resin to reduce the elastic modulus, improve the flexibility of the termination tape, make it more suitable for bending applications, and play a role in buffering and shock absorption, protecting sensitive components in electronic devices. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the highly flexible, electrolyte-resistant termination tape structure prepared in Example 1. Detailed Implementation

[0022] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0023] In the following examples, except for modified polyacrylic acid resin 1, modified polyacrylic acid resin 2, modified polyacrylic acid resin 3, modified polyphosphazene, and polyphosphazene, all other compound monomers and related reagents used can be purchased from the market. Among them, the PET substrate was purchased from Huizhou Boyi Technology Co., Ltd., brand name 1, with a thickness of 15μm; the non-silicone release agent was purchased from Shanghai Mingtu New Materials Co., Ltd., model MT-218; the allyloxyisomeric alcohol ether sulfate ammonium salt was purchased from Adico (China) Investment Co., Ltd., model SR-10; the pigment was blue ink, purchased from Suzhou Jixin Trading Co., Ltd.; and the curing agent was isocyanate curing agent, purchased from Shanghai Sendi Chemical Co., Ltd., model BI7675.

[0024] The synthesis of modified polyacrylic acid resin 1 includes the following steps: (1) Add 8g of methyl methacrylate, 50g of 2-ethylhexyl acrylate, 30g of isooctyl acrylate, 12g of vinyl acetate, 1.2g of allyloxyisomeric alcohol ether sulfate ammonium salt, 3g of N-hydroxymethylacrylamide and 120g of water to a flask, stir and mix at room temperature for 20min to obtain a pre-emulsion. (2) Take 100g of water, 0.7g of benzoyl peroxide and 1 / 2 of the pre-emulsion obtained in step (1) and add them to the flask. Heat the flask to 70°C and stir for 30 min. Then slowly add the remaining pre-emulsion and 0.8g of benzoyl peroxide over 2 h and heat the flask to 80°C for 3 h. After the reaction is complete, cool the flask to 40°C and add ammonia to adjust the pH of the reaction system to 7. Then add 5g of di(2-butoxyethyl) phthalate and continue stirring for 30 min. Filter the flask to obtain modified polyacrylic acid resin 1.

[0025] The synthesis of modified polyacrylic acid resin 2 includes the following steps: (1) Add 8g of methyl methacrylate, 50g of 2-ethylhexyl acrylate, 30g of isooctyl acrylate, 12g of vinyl acetate, 1.2g of allyloxyisomeric alcohol ether sulfate ammonium salt, 3g of N-hydroxymethylacrylamide and 120g of water to a flask, stir and mix at room temperature for 20min to obtain a pre-emulsion. (2) Take 100g of water, 0.7g of benzoyl peroxide and 1 / 2 of the pre-emulsion obtained in step (1) and add them to the flask. Heat the flask to 70°C and stir for 30 min. Then slowly add the remaining pre-emulsion and 0.8g of benzoyl peroxide over 2 h and heat the flask to 80°C for 3 h. After the reaction is complete, cool the flask to 40°C and add ammonia to adjust the pH of the reaction system to 7. Then add 5g of diethyl phthalate and continue stirring and mixing for 30 min. Filter the mixture to obtain modified polyacrylic acid resin 2.

[0026] The synthesis of modified polyphosphazene includes the following steps: (1) Under a nitrogen atmosphere, 17g of hexachlorocyclotriphosphazene, 0.049g of aminosulfonic acid, 0.079g of calcium sulfate dihydrate and 30mL of 1,2,4-trichlorobenzene were added to a round-bottom flask. The mixture was heated to reflux at 215°C. When the system became viscous, the heating was stopped. After cooling to 70°C, 200mL of petroleum ether was added to the flask to precipitate the product. The product was then filtered and washed with petroleum ether to obtain a polyphosphazene intermediate. (2) Under a nitrogen atmosphere, 10.0 mL of p-methylphenol, 2.3 g of sodium hydride with a mass fraction of 60% and 60 mL of 1,4-dioxane were added to a round-bottom flask. The mixture was stirred at room temperature for 12 h. After the reaction was completed, it was slowly poured into a flask containing the polyphosphazene intermediate obtained in step (1) and 100 mL of 1,4-dioxane. The mixture was heated to reflux at 100 °C for 20 h. After the reaction was completed, it was cooled to room temperature. A large amount of deionized water was added to the system to precipitate the solid. The solid was collected by filtration, dried at 80 °C, and then dissolved in tetrahydrofuran. A large amount of deionized water was added to the solid to precipitate it. The purification was repeated twice. Finally, the solid was dried in a vacuum oven at 80 °C for 24 h to obtain modified polyphosphazene.

[0027] The synthesis of polyphosphazenes includes the following steps: Under a nitrogen atmosphere, 17 g of hexachlorocyclotriphosphazene, 0.049 g of aminosulfonic acid, 0.079 g of calcium sulfate dihydrate and 30 mL of 1,2,4-trichlorobenzene were added to a round-bottom flask. The mixture was heated to reflux at 215 °C. Heating was stopped when the system became viscous. After cooling to 70 °C, 200 mL of petroleum ether was added to the flask to precipitate the polyphosphazene. The precipitate was then filtered, washed with petroleum ether, and dried at 90 °C to obtain polyphosphazene.

[0028] Example 1: A method for preparing a highly flexible, electrolyte-resistant termination tape includes the following steps: (1) 70 parts of modified acrylic resin, 1 part of pigment, and 70 parts of ethyl acetate were heated and stirred at 80°C for 20 min. Then, 3 parts of isocyanate curing agent and 3 parts of modified polyphosphazene were added and stirred for another 30 min to obtain acrylic pressure-sensitive adhesive. (2) The acrylic pressure-sensitive adhesive is evenly coated on the PET substrate (the thickness of the acrylic pressure-sensitive adhesive coating is 25µm), dried and shaped at 100℃, and then the non-silicone release agent is evenly coated on the other side of the PET substrate (the thickness of the non-silicone release agent coating is 1µm), and then cured and shaped at 120℃, and wound and cut to obtain a highly flexible and electrolyte-resistant termination tape.

[0029] Example 2: A method for preparing a highly flexible, electrolyte-resistant termination tape includes the following steps: (1) 75 parts modified acrylic resin, 1 part pigment, and 60 parts ethyl acetate were heated and stirred at 80°C. Then, 2 parts isocyanate curing agent and 3 parts modified polyphosphazene were added and stirred and mixed to obtain acrylic pressure-sensitive adhesive. (2) The acrylic pressure-sensitive adhesive is evenly coated on the PET substrate (the thickness of the acrylic pressure-sensitive adhesive coating is 25µm), dried and shaped at 100℃, and then the non-silicone release agent is evenly coated on the other side of the PET substrate (the thickness of the non-silicone release agent coating is 1µm), and then cured and shaped at 120℃, and wound and cut to obtain a highly flexible and electrolyte-resistant termination tape.

[0030] The components and preparation method of Example 3 are basically the same as those of Example 1, except that 70 parts of modified acrylic resin 1 are replaced with 70 parts of modified acrylic resin 2.

[0031] The components and preparation method of Example 4 are basically the same as those of Example 1, except that 3 parts of modified polyphosphazene are replaced with 5 parts of modified polyphosphazene.

[0032] Comparative Example 1: A method for preparing a highly flexible, electrolyte-resistant termination tape includes the following steps: (1) 70 parts of modified acrylic resin, 1 part of pigment, and 70 parts of ethyl acetate were heated and stirred at 80°C for 20 min. Then, 3 parts of isocyanate curing agent and 3 parts of polyphosphazene were added and stirred for another 30 min to obtain acrylic pressure-sensitive adhesive. (2) The acrylic pressure-sensitive adhesive is evenly coated on the PET substrate (the thickness of the acrylic pressure-sensitive adhesive coating is 25µm), dried and shaped at 100℃, and then the non-silicone release agent is evenly coated on the other side of the PET substrate (the thickness of the non-silicone release agent coating is 1µm), and then cured and shaped at 120℃, and wound and cut to obtain a highly flexible and electrolyte-resistant termination tape.

[0033] Comparative Example 2: A method for preparing a highly flexible, electrolyte-resistant termination tape includes the following steps: (1) 10 parts of methyl methacrylate, 50 parts of isooctyl acrylate, 10 parts of vinyl acetate, 2 parts of pigment, and 70 parts of ethyl acetate were heated and stirred at 80°C for 20 min. Then, 3 parts of isocyanate curing agent and 3 parts of modified polyphosphazene were added and stirred for another 30 min to obtain acrylic pressure-sensitive adhesive. (2) The acrylic pressure-sensitive adhesive is evenly coated on the PET substrate (the thickness of the acrylic pressure-sensitive adhesive coating is 25µm), dried and shaped at 100℃, and then the non-silicone release agent is evenly coated on the other side of the PET substrate (the thickness of the non-silicone release agent coating is 1µm), and then cured and shaped at 120℃, and wound and cut to obtain a highly flexible and electrolyte-resistant termination tape.

[0034] The terminating tapes prepared in Examples 1-4 and Comparative Examples 1-2 were subjected to tests for viscosity, elastic modulus, electrolyte corrosion resistance, and high temperature resistance. The specific test methods are as follows: Viscosity: The acrylic pressure-sensitive adhesive layer was tested according to ASTM D3330; Elastic modulus: Tested according to GB / T 1040-2006; Electrolyte corrosion resistance: The termination tape was attached to the aluminum foil and immersed in the lithium battery electrolyte at 85°C for 4 hours. The fading and peeling of the termination tape were then observed. High temperature resistance: Apply the termination tape to the aluminum foil and bake at 100°C for 1 hour, then observe the residual adhesive on the termination tape.

[0035] The test results are shown in Table 1: Table 1

[0036] As can be seen from the test results of Example 1 and Comparative Examples 1-2 in Table 1, compared with directly using polyphosphazene or directly using acrylate monomers to prepare the termination tape, the termination tape prepared using modified polyphosphazene and modified polyacrylic acid resin has higher viscosity and lower elastic modulus. This indicates that the termination tape prepared by the present invention has good adhesion and high flexibility. When applied to the termination part of the battery cell, it can suppress the displacement caused by charging and discharging vibration. In the electrolyte test, there was no peeling or fading, indicating that the termination tape has good resistance to electrolyte corrosion and can extend the battery's service life. There was no residue at high temperature, indicating that the acrylic pressure-sensitive adhesive has good chemical stability, thereby improving the overall stability of the tape.

[0037] The test results of Examples 1-2 show that the termination tape prepared by the method provided by the present invention has high viscosity, high flexibility, resistance to electrolyte corrosion, and high temperature resistance. Furthermore, the test results of Examples 1 and 3 show that compared with using conventional plasticizers (diethyl phthalate), using di(2-butoxyethyl) phthalate as a plasticizer to prepare modified polyacrylic acid resin and then using the modified polyacrylic acid resin to prepare the termination tape results in a termination tape with superior performance. The test results of Examples 1 and 4 show that when the amount of modified polyphosphazene added is within a suitable range of the amount of modified polyacrylic acid resin added, the termination tape obtained has superior performance.

[0038] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A highly flexible, electrolyte-resistant termination tape, characterized in that, The termination tape comprises, from bottom to top: a non-silicone release agent coating, a PET substrate layer, and an acrylic pressure-sensitive adhesive; The raw materials for preparing the acrylic pressure-sensitive adhesive include the following components in parts by weight: 50-100 parts of modified polyacrylic acid resin, 1-10 parts of curing agent, 1-10 parts of functional additives, 1-5 parts of pigment, and 50-100 parts of solvent. The functional additive is a modified polyphosphazene.

2. The highly flexible, electrolyte-resistant termination tape according to claim 1, characterized in that, The synthesis of the modified polyacrylic acid resin includes the following steps: (1) Add acrylate monomer, emulsifier, crosslinking agent and solvent to the flask, stir and mix evenly to obtain a pre-emulsion; (2) Add water, initiator and part of the pre-emulsion obtained in step (1) into a flask, heat to 50-70℃ and stir to react. Then slowly add the remaining pre-emulsion and initiator over 2-4 hours, and heat to 70-90℃ to keep the temperature for reaction. After the reaction is complete, cool down to 40-50℃, add pH adjuster to adjust the reaction system to neutral, add plasticizer, continue stirring and mixing, filter and discharge to obtain modified polyacrylic acid resin.

3. The highly flexible, electrolyte-resistant termination tape according to claim 2, characterized in that, The plasticizer is di(2-butoxyethyl) phthalate.

4. The highly flexible, electrolyte-resistant termination tape according to claim 2, characterized in that, The added mass of the plasticizer is 2-8% of the total mass of the acrylate monomers.

5. The highly flexible, electrolyte-resistant termination tape according to claim 1, characterized in that, The preparation method of the modified polyphosphazene includes the following steps: (1) Under a nitrogen atmosphere, hexachlorocyclotriphosphazene, catalyst and organic solvent were added to a round-bottom flask and heated to reflux. When the reaction system became viscous, the heating was stopped and the product was post-processed to obtain polyphosphazene intermediate. (2) Under a nitrogen atmosphere, p-methylphenol and a strong base were added to a round-bottom flask and stirred at room temperature. After the reaction was completed, the mixture was slowly poured into a mixture of the polyphosphazene intermediate obtained in step (1) and an organic solvent. The mixture was heated and refluxed. After the reaction was completed, the mixture was cooled to room temperature and then post-treated to obtain modified polyphosphazene.

6. The highly flexible, electrolyte-resistant termination tape according to claim 1, characterized in that, The amount of modified polyphosphazene added is 2wt%-6wt% of the amount of modified polyacrylic acid resin added.

7. The highly flexible, electrolyte-resistant termination tape according to claim 1, characterized in that, The curing agent is at least one of isocyanate curing agents and imidazole curing agents.

8. The highly flexible, electrolyte-resistant termination tape according to claim 1, characterized in that, The pigment is blue ink.

9. The highly flexible, electrolyte-resistant termination tape according to claim 1, characterized in that, The solvent is at least one of isobutanol, ethyl acetate, tetrahydrofuran, and N,N-dimethylformamide.

10. A method for preparing a highly flexible, electrolyte-resistant termination tape according to any one of claims 1-9, characterized in that, Includes the following steps: (1) According to the weight parts, the modified acrylic resin, pigment and solvent are heated and stirred to mix, and then the curing agent and functional additives are added and stirred to obtain acrylic pressure-sensitive adhesive. (2) Apply acrylic pressure-sensitive adhesive evenly to the PET substrate, dry and shape it, then apply non-silicone release agent evenly to the other side of the PET substrate, then perform curing and shaping, and roll up and cut to obtain a highly flexible and electrolyte-resistant termination tape.

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