A lithium battery positive electrode film oil coating roller composite material and a preparation method thereof

Abstract

The application discloses a lithium battery positive electrode film oily coating roller composite material and a preparation method thereof, relates to the technical field of fluororubber materials, and comprises 100 parts of fluororubber, 15-28 parts of a reinforcing agent, 3-7 parts of a process aid, 12-22 parts of carbon nanotube masterbatch, 2-3 parts of a vulcanizing agent and 4-7 parts of TAIC-70; wherein: the fluororubber is covalently grafted with triazine group perfluorinated covalent organic framework PF-COF in situ; and the reinforcing agent is boron-nitrogen two-dimensional hybrid nanosheet obtained by compounding hydroxylated hexagonal boron nitride and boron-doped graphene at a mass ratio of 6-7:3-4. The application is synergized with the boron-nitrogen two-dimensional hybrid nanosheet through PF-COF grafting modification, can significantly improve the solvent resistance, effectively inhibit swelling and prolong the service life of the roller, thereby reducing the replacement frequency, and achieving the effects of improving product quality and production efficiency.

Description

Technical Field

[0001] This application relates to the field of fluororubber materials technology, and in particular to a lithium battery positive electrode film oil-based coating roller composite material and its preparation method. Background Technology

[0002] As climate change intensifies and prices of traditional fossil fuels like oil and coal fluctuate wildly, the substitution of new energy sources and the development of green energy industries have become core trends in energy transformation. The rapid advancement of green power industries such as hydrogen energy and photovoltaics has significantly expanded the development boundaries of the energy storage industry. Lithium-ion batteries and solid-state batteries, as the core development direction of new energy storage, have ushered in a historic opportunity for large-scale development. With the rapid expansion of downstream emerging industries such as new energy vehicles, the low-altitude economy, and humanoid robots, market demand for lithium-ion battery products is experiencing exponential growth, placing higher standards and requirements on the process precision, production efficiency, and product quality of lithium-ion battery manufacturing. Positive electrode film coating is a key process in lithium-ion battery production, directly determining the coating quality, production stability, and overall economic efficiency of the lithium-ion battery positive electrode film. It is a core link in the high-performance, large-scale production of lithium-ion batteries.

[0003] In the conventional production process of oil-based coating for lithium-ion battery cathode films, DMF, DMAC, NMP, and various mixed solvents are commonly used as diluents for the cathode film materials. These strong solvent conditions place stringent demands on the performance of the core components of the coating equipment. The dewatering roller, as a highly customized key component in the cathode film coating process, is made of rubber. Its core performance indicators must be adapted to the requirements of the coating production conditions, specifically including excellent resistance to strong solvents, high elastic recovery performance, and stable antistatic properties, thereby ensuring the uniformity and stability of the cathode film coating. Currently, mainstream cathode film coating dewatering rollers in the industry are all made of conventional rubber materials in a single piece. Relying on the basic physical properties of the rubber matrix, they are adapted to coating, dewatering, and lamination operations. They are indispensable core components in current lithium-ion battery cathode film coating production lines and are widely used in various high-speed coating production scenarios for lithium-ion battery cathode films.

[0004] However, existing rubber squeezing rollers have poor solvent resistance in actual industrial production applications. They are prone to significant swelling and deformation under long-term immersion or contact with strong solvents such as DMF, DMAC, and NMP, resulting in a shortened service life of only 3 to 7 days. This leads to frequent shutdowns for roller replacement during production, significantly increasing equipment downtime and labor maintenance costs, severely impacting the efficiency of continuous production line operations and hindering the pace of large-scale production. Secondly, there is the issue of scratching, especially at high-speed coating speeds of 90 m / min, where static electricity can easily cause white spots or uneven coating of the positive electrode film, seriously affecting coating quality and requiring improvement.

[0005] This invention provides a composite material for oily coating rollers of lithium battery positive electrode film and its preparation method, which enables the coating rollers to have good resistance to strong solvents and high resilience, and fundamentally solves the problem of smudging during the coating process, greatly improving the service life of the rollers and reducing the frequency of downtime for replacement. Summary of the Invention

[0006] In view of this, the first objective of this application is to provide a composite material for an oily coating roller for lithium battery positive electrode film, so as to solve the problem of swelling and deformation of the coating roller, so that the coating roller has good resistance to strong solvents and high resilience, and fundamentally solves the problem of smudging during the coating process, greatly improving the service life of the roller and reducing the frequency of downtime for replacement.

[0007] The specific plan is as follows: A composite material for oil-based coating rollers of lithium battery positive electrode films, comprising 100 parts by weight of fluororubber, 15-28 parts by weight of reinforcing agent, 3-7 parts by weight of processing aid, 12-22 parts by weight of carbon nanotube masterbatch, 2-3 parts by weight of vulcanizing agent, and 4-7 parts by weight of TAIC-70; wherein: The fluororubber is in situ covalently grafted with a triazine-based perfluorinated covalent organic framework PF-COF; The reinforcing agent is a boron-nitrogen two-dimensional hybrid nanosheet obtained by combining hydroxylated hexagonal boron nitride and boron-doped graphene in a mass ratio of 6-7:3-4.

[0008] Preferably, the process aids include PE wax and WS180 in a mass ratio of 2:0.9-1; the carbon nanotube masterbatch is a carbon nanotube pre-dispersed masterbatch with a mass concentration of 9-11% obtained by mixing and internally mixing with fluororubber; and the vulcanizing agent is bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane adsorbent powder with a concentration of 48-52 wt%.

[0009] Preferably, the amount of PF-COF added is 2.5-4.5 parts.

[0010] Preferably, the preparation method of the reinforcing agent includes step ① adding hydroxylated hexagonal boron nitride to anhydrous ethanol, stirring evenly at room temperature and ultrasonically dispersing to obtain a pre-dispersion liquid; step ② adding boron-doped graphene to the pre-dispersion liquid, stirring evenly and ultrasonically dispersing to obtain a mixed dispersion liquid with a solid content of 8-10%; step ③ centrifuging the mixed dispersion liquid to obtain a solid precipitate and vacuum drying to obtain the finished two-dimensional hybrid nanosheets.

[0011] Preferably: Step ① involves adding hydroxylated hexagonal boron nitride to anhydrous ethanol, stirring at room temperature for 10 minutes, and then ultrasonically dispersing at 300W for 40 minutes to obtain a pre-dispersion; Step ② involves adding boron-doped graphene to the pre-dispersion and stirring continuously for 15 minutes, followed by ultrasonic dispersion at 400W for 60 minutes to obtain a mixed dispersion with a solid content of 8-10%; Step ③ involves centrifuging the mixed dispersion at 8000 r / min for 20 minutes to obtain a solid precipitate, and then vacuum drying at 60℃ for 12 hours to obtain the finished two-dimensional hybrid nanosheets.

[0012] Preferably, it further comprises 2.0-3.5 parts by weight of zinc dodecylphosphonate and 3.0-5.0 parts by weight of chitosan-based solvent-responsive self-healing microcapsules.

[0013] Preferably, the preparation method of the chitosan-based solvent-responsive self-healing microcapsules includes the following steps: Step ① adding 2-3 parts by weight of chitosan to 97-98 parts by weight of 2.5% glacial acetic acid aqueous solution, and stirring to dissolve to obtain a chitosan aqueous solution; Step ② adding a fluorinated prepolymer crosslinking solution dropwise to the chitosan aqueous solution, and obtaining an oil-in-water emulsion through a high-speed emulsification reaction; Step ③ adding dilute ammonia dropwise to the oil-in-water emulsion to adjust the pH value to 7.0-7.5, and stirring continuously to solidify, followed by centrifugation, washing, drying, pulverizing and sieving to obtain the final product.

[0014] Preferably, the fluorinated prepolymer crosslinking solution is obtained by mixing a fluorinated prepolymer and an isocyanate crosslinking agent at a mass ratio of 95:5, followed by adding 2% Span-80 by mass and stirring; the high-speed emulsification reaction is carried out by controlling the stirring speed at 3000 r / min for 30 min; the mass ratio of the fluorinated prepolymer crosslinking solution to the chitosan aqueous solution is 1:3-4, and the dilute ammonia solution is 5% by mass.

[0015] The second objective of this invention is to provide a method for preparing an oil-based coating roller composite material for lithium battery positive electrode films, as described above, comprising the following steps: Step 1: Mix fluororubber, PF-COF, zinc dodecylphosphonate and a portion of vulcanizing agent and knead to obtain a pre-composite fluororubber with in-situ grafting and ion crosslinking of PF-COF. Step 2: Press the pre-composite fluororubber through a two-roll mill to obtain a semi-transparent two-roll plasticized fluororubber; Step 3: Add process aids, reinforcing agents and chitosan-based solvent-responsive self-healing microcapsules to open-milled plasticized fluororubber. After one mixing, add carbon nanotubes and mix a second time to obtain a compounded composite. Step 4: Add the remaining vulcanizing agent and TAIC-70 to the compound, and obtain the compound to be vulcanized after three mixing processes. Step 5: The rubber compound to be vulcanized is subjected to two-stage vulcanization treatment to obtain the finished lithium battery positive electrode film oil-based coating roller composite material.

[0016] Preferably: In step 1, the vulcanizing agent accounts for less than 20% of the total mass of the vulcanizing agent, and the pre-composite fluororubber is left to stand at room temperature for no less than 72 hours after being obtained; in step 2, the pressing time is 5-6 minutes; in step 3, the first mixing time is 6-8 minutes, and the second mixing time is 2-2.5 minutes; in step 4, the third mixing time is 2-2.5 minutes, and no less than 5 triangular slabs are formed, the roller gap of the open mill is controlled to be less than 1 mm, and after passing through the thin mill at least 10 times, the sheet is cooled and left to stand at room temperature for no less than 72 hours; in step 5, the two-stage vulcanization treatment includes a first-stage vulcanization using a flat vulcanizing machine and a second-stage vulcanization using an oven; the temperature of the first-stage vulcanization is 175-178℃, and the time is 7.5-8.5 minutes; the temperature of the second-stage vulcanization is 195-205℃, and the time is 5.8-6.2 hours.

[0017] As can be seen from the above solutions, this application provides a lithium battery positive electrode film oil-based coating roller composite material and its preparation method. This lithium battery positive electrode film oil-based coating roller composite material and its preparation method have the following beneficial effects: 1. By in-situ covalently grafting triazine-based perfluorinated covalent organic framework PF-COF onto fluororubber, its resistance to strong solvents such as DMF, DMAC, and NMP is significantly improved in synergy with boron-nitrogen two-dimensional hybrid nanosheets, carbon nanotube masterbatch, and process aids. This effectively inhibits the swelling and deformation of the rollers used to prepare oily coating rollers for lithium battery cathode films, thus extending their service life. It also improves antistatic properties and surface self-lubrication, reducing downtime and replacement frequency, thereby improving production quality and efficiency. 2. By grafting PF-COF covalent bonds onto the molecular chain of fluororubber, its rigid layered structure restricts the movement of polymer chain segments, and the polar repulsion generated based on the perfluorinated structure reduces solvent wetting and penetration; the boron-nitrogen two-dimensional hybrid nanosheets form intricate barrier channels, prolonging the solvent diffusion path, thereby solving the problems of low solvent resistance and short-term failure. 3. By using zinc dodecylphosphonate and fluororubber to form a dynamic ionic cross-linking network, which complements and synergizes with the covalent cross-linking structure, internal stress is released and microcrack initiation is inhibited during repeated extrusion deformation, thereby improving fatigue resistance. Furthermore, chitosan-based solvent-responsive microcapsules are distributed at the component interface to trigger capsule rupture when solvent penetrates the gaps, thereby sealing defects through in-situ cross-linking and achieving the effect of self-repair of interface damage. Detailed Implementation

[0018] The technical solutions described below in conjunction with the embodiments of this application will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] It should be noted that the fluororubber in this embodiment is a peroxy-cured fluororubber with a fluorine content ≥70%, a Mooney viscosity ML1+10, and a value of 20-30 at 121°C. TAIC-70 is a powder of triallyl isocyanurate containing 30wt% fumed silica. The vulcanizing agent is grade 101-50D. The hydroxyl grafting rate in the hydroxylated hexagonal boron nitride is ≥8%, and the boron doping amount in the boron-doped graphene is 3-5 at%, both of which are commercially available and will not be described in detail here. The particle size of the prepared chitosan-based solvent-responsive self-healing microcapsules is 2-5 μm.

[0020] The following will provide a detailed description of an oily coating roller composite material for lithium battery positive electrode film and its preparation method.

[0021] A composite material for oil-based coating rollers of lithium battery positive electrode film comprises 100 parts by weight of fluororubber, 15-28 parts by weight of reinforcing agent, 3-7 parts by weight of process aid, 12-22 parts by weight of carbon nanotube masterbatch, 2-3 parts by weight of vulcanizing agent, and 4-7 parts by weight of TAIC-70.

[0022] in: In situ covalent grafting of fluororubber with triazine-based perfluorinated covalent organic framework PF-COF, and the amount of PF-COF added during grafting is 2.5-4.5 parts.

[0023] The reinforcing agent is a boron-nitrogen two-dimensional hybrid nanosheet obtained by combining hydroxylated hexagonal boron nitride and boron-doped graphene in a mass ratio of 6-7:3-4.

[0024] The preparation method of the reinforcing agent includes step ① adding hydroxylated hexagonal boron nitride to anhydrous ethanol, stirring at room temperature for 10 min, and then ultrasonically dispersing at 300W for 40 min to obtain a pre-dispersion; step ② adding boron-doped graphene to the pre-dispersion and stirring continuously for 15 min, and then ultrasonically dispersing at 400W for 60 min to obtain a mixed dispersion with a solid content of 8-10%; step ③ centrifuging the mixed dispersion at a speed of 8000 r / min for 20 min to obtain a solid precipitate, and then vacuum drying at 60℃ for 12 h to obtain the finished two-dimensional hybrid nanosheets.

[0025] Processing aids include PE wax and WS180 in a mass ratio of 2:0.9-1. The carbon nanotube masterbatch is a pre-dispersed carbon nanotube masterbatch with a mass concentration of 9-11% obtained by mixing and internally mixing with fluororubber. The vulcanizing agent is 48-52 wt% bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane adsorbent powder.

[0026] To further reduce solvent wettability and achieve self-healing, the lithium battery positive electrode film oil-coating roller composite material in this application embodiment also includes 2.0-3.5 parts by weight of zinc dodecylphosphonate and 3.0-5.0 parts by weight of chitosan-based solvent-responsive self-healing microcapsules.

[0027] The preparation method of chitosan-based solvent-responsive self-healing microcapsules includes the following steps: Step ① Adding 2-3 parts by weight of chitosan to 97-98 parts by weight of 2.5% glacial acetic acid aqueous solution and stirring to dissolve to obtain chitosan aqueous solution; Step ② Adding a fluorinated prepolymer crosslinking solution dropwise to the chitosan aqueous solution, controlling the mixing mass ratio of the fluorinated prepolymer crosslinking solution to the chitosan aqueous solution to be 1:3-4, and the fluorinated prepolymer crosslinking solution is obtained by mixing a fluorinated prepolymer and an isocyanate crosslinking agent at a mass ratio of 95:5, and then adding 2% by mass of Span-80 and mixing and stirring, and obtaining an oil-in-water emulsion by high-speed emulsification reaction controlled at a stirring speed of 3000 r / min for 30 min; Step ③ Adding 5% by mass of ammonia water dropwise to the oil-in-water emulsion to adjust the pH value to 7.0-7.5, and stirring continuously to solidify, and then centrifuging, washing, drying and pulverizing and sieving to obtain the final product.

[0028] A method for preparing an oil-based coating roller composite material for lithium battery positive electrode film, used to prepare the oil-based coating roller composite material for lithium battery positive electrode film as described above, includes the following steps: Step 1: Mix fluororubber, PF-COF, zinc dodecylphosphonate and a portion of vulcanizing agent accounting for no more than 20% of the total mass and knead to obtain a pre-composite fluororubber with in-situ grafting and ion crosslinking of PF-COF, and then let it stand at room temperature for no less than 72 hours. Step 2: Press the pre-composite fluororubber on a two-roll mill for 5-6 minutes to obtain a semi-transparent two-roll plasticized fluororubber. Step 3: Add process aids, reinforcing agents and chitosan-based solvent-responsive self-healing microcapsules to open-milled plasticized fluororubber. After a first mixing of 6-8 minutes, add carbon nanotube masterbatch and mix for a second time of 2-2.5 minutes to obtain the compounded composite. Step 4: Add the remaining vulcanizing agent and TAIC-70 to the compound, make no less than 5 triangular bags and mix three times for 2-2.5 minutes. Control the gap of the open mill to be less than 1 mm, pass through the thin mill at least 10 times, then sheet and cool and let it stand at room temperature for no less than 72 hours to obtain the compound to be vulcanized. Step 5: The rubber compound to be vulcanized undergoes a two-stage vulcanization process, namely a first-stage vulcanization using a flat vulcanizing machine and a second-stage vulcanization using an oven. The first-stage vulcanization temperature is 175-178℃ and the time is 7.5-8.5 min, while the second-stage vulcanization temperature is 195-205℃ and the time is 5.8-6.2 h, to obtain the finished lithium battery positive electrode film oil-based coating roller composite material. Example 1

[0029] A composite material for oil-based coating rollers of lithium battery positive electrode film comprises 100 parts by weight of fluororubber, 15 parts of reinforcing agent, 3 parts of process aid, 12 parts of carbon nanotube masterbatch, 2 parts of vulcanizing agent, and 4 parts of TAIC-70.

[0030] in: Fluororubber is in situ covalently grafted with a triazine-based perfluorinated covalent organic framework PF-COF, and the amount of PF-COF added during grafting is 2.5 parts.

[0031] The reinforcing agent is a boron-nitrogen two-dimensional hybrid nanosheet obtained by combining hydroxylated hexagonal boron nitride and boron-doped graphene in a mass ratio of 6:4.

[0032] The preparation method of the reinforcing agent includes step ① adding hydroxylated hexagonal boron nitride to anhydrous ethanol, stirring at room temperature for 10 min, and then ultrasonically dispersing at 300W for 40 min to obtain a pre-dispersion liquid; step ② adding boron-doped graphene to the pre-dispersion liquid and stirring continuously for 15 min, and then ultrasonically dispersing at 400W for 60 min to obtain a mixed dispersion liquid with a solid content of 8%; step ③ centrifuging the mixed dispersion liquid at a speed of 8000 r / min for 20 min to obtain a solid precipitate, and then vacuum drying at 60℃ for 12 h to obtain the finished two-dimensional hybrid nanosheets.

[0033] Processing aids include PE wax and WS180 in a mass ratio of 2:0.9. The carbon nanotube masterbatch is a 9% carbon nanotube pre-dispersed masterbatch obtained by mixing and internally mixing with fluororubber. The vulcanizing agent is 48wt% bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane adsorbent powder.

[0034] To further reduce solvent wettability and achieve self-healing, the lithium battery positive electrode film oil-coating roller composite material in this application embodiment also includes 2.0 parts by weight of zinc dodecylphosphonate and 3.0 parts by weight of chitosan-based solvent-responsive self-healing microcapsules.

[0035] The preparation method of chitosan-based solvent-responsive self-healing microcapsules includes the following steps: Step ① Adding 2 parts by weight of chitosan to 98 parts by weight of 2.5% glacial acetic acid aqueous solution and stirring to dissolve to obtain chitosan aqueous solution; Step ② Adding a fluorinated prepolymer crosslinking solution dropwise to the chitosan aqueous solution, controlling the mixing mass ratio of the fluorinated prepolymer crosslinking solution to the chitosan aqueous solution to be 1:3, and the fluorinated prepolymer crosslinking solution is obtained by mixing a fluorinated prepolymer and an isocyanate crosslinking agent at a mass ratio of 95:5, then adding 2% by mass of Span-80 and mixing and stirring, and obtaining an oil-in-water emulsion by high-speed emulsification reaction controlled at a stirring speed of 3000 r / min for 30 min; Step ③ Adding 5% by mass of ammonia water dropwise to the oil-in-water emulsion to adjust the pH value to 7.0, and stirring continuously to solidify, followed by centrifugation, washing, drying, pulverizing and sieving to obtain the final product.

[0036] A method for preparing an oil-based coating roller composite material for lithium battery positive electrode film, used to prepare the oil-based coating roller composite material for lithium battery positive electrode film as described above, includes the following steps: Step 1: Mix fluororubber, PF-COF, zinc dodecylphosphonate and a portion of vulcanizing agent accounting for no more than 20% of the total mass and knead to obtain a pre-composite fluororubber with in-situ grafting and ion crosslinking of PF-COF, and then let it stand at room temperature for no less than 72 hours. Step 2: Press the pre-composite fluororubber on a two-roll mill for 5 minutes to obtain a semi-transparent two-roll plasticized fluororubber. Step 3: Add process aids, reinforcing agents and chitosan-based solvent-responsive self-healing microcapsules to open-milled plasticized fluororubber. After a first mixing of 6 minutes, add carbon nanotube masterbatch and mix for a second time of 2 minutes to obtain a compound. Step 4: Add the remaining vulcanizing agent and TAIC-70 to the compound, make no less than 5 triangular bags and mix three times for 2 minutes each, control the gap of the open mill to be less than 1 mm, pass through the thin mill at least 10 times, then sheet and cool and let stand at room temperature for no less than 72 hours to obtain the compound to be vulcanized. Step 5: The rubber compound to be vulcanized is subjected to two-stage vulcanization treatment: a first-stage vulcanization using a flat vulcanizing machine and a second-stage vulcanization using an oven. The temperature of the first-stage vulcanization is 175℃ and the time is 7.5 min, while the temperature of the second-stage vulcanization is 195℃ and the time is 5.8 h, to obtain the finished lithium battery positive electrode film oil-based coating roller composite material. Example 2

[0037] A composite material for oil-based coating rollers of lithium battery positive electrode film comprises 100 parts by weight of fluororubber, 22 parts by weight of reinforcing agent, 5 parts by weight of process aid, 17 parts by weight of carbon nanotube masterbatch, 2.5 parts by weight of vulcanizing agent, and 5.5 parts by weight of TAIC-70.

[0038] in: Fluororubber is in situ covalently grafted with a triazine-based perfluorinated covalent organic framework PF-COF, and the amount of PF-COF added during grafting is 3.5 parts.

[0039] The reinforcing agent is a boron-nitrogen two-dimensional hybrid nanosheet obtained by combining hydroxylated hexagonal boron nitride and boron-doped graphene in a mass ratio of 6.5:3.5.

[0040] The preparation method of the reinforcing agent includes step ① adding hydroxylated hexagonal boron nitride to anhydrous ethanol, stirring at room temperature for 10 min, and then ultrasonically dispersing at 300W for 40 min to obtain a pre-dispersion liquid; step ② adding boron-doped graphene to the pre-dispersion liquid and stirring continuously for 15 min, and then ultrasonically dispersing at 400W for 60 min to obtain a mixed dispersion liquid with a solid content of 9%; step ③ centrifuging the mixed dispersion liquid at a speed of 8000 r / min for 20 min to obtain a solid precipitate, and then vacuum drying at 60℃ for 12 h to obtain the finished two-dimensional hybrid nanosheets.

[0041] Processing aids include PE wax and WS180 in a mass ratio of 2:0.95. The carbon nanotube masterbatch is a 10% carbon nanotube pre-dispersed masterbatch obtained by mixing and internally mixing with fluororubber. The vulcanizing agent is a 50wt% concentration of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane adsorbent powder.

[0042] To further reduce solvent wettability and achieve self-healing, the lithium battery positive electrode film oil-coating roller composite material in this application embodiment also includes 2.8 parts by weight of zinc dodecylphosphonate and 4.0 parts by weight of chitosan-based solvent-responsive self-healing microcapsules.

[0043] The preparation method of chitosan-based solvent-responsive self-healing microcapsules includes the following steps: Step ① Adding 2.5 parts by weight of chitosan to 97.5 parts by weight of 2.5% glacial acetic acid aqueous solution and stirring to dissolve to obtain chitosan aqueous solution; Step ② Adding a fluorinated prepolymer crosslinking solution dropwise to the chitosan aqueous solution, controlling the mixing mass ratio of the fluorinated prepolymer crosslinking solution to the chitosan aqueous solution to be 1:3.5, and the fluorinated prepolymer crosslinking solution is obtained by mixing a fluorinated prepolymer and an isocyanate crosslinking agent at a mass ratio of 95:5, and then adding 2% by mass of Span-80 and mixing and stirring, and obtaining an oil-in-water emulsion by high-speed emulsification reaction controlled at a stirring speed of 3000 r / min for 30 min; Step ③ Adding 5% by mass of ammonia water dropwise to the oil-in-water emulsion to adjust the pH value to 7.2, and stirring continuously to solidify, and then centrifuging, washing, drying and pulverizing and sieving to obtain the final product.

[0044] A method for preparing an oil-based coating roller composite material for lithium battery positive electrode film, used to prepare the oil-based coating roller composite material for lithium battery positive electrode film as described above, includes the following steps: Step 1: Mix fluororubber, PF-COF, zinc dodecylphosphonate and a portion of vulcanizing agent accounting for no more than 20% of the total mass and knead to obtain a pre-composite fluororubber with in-situ grafting and ion crosslinking of PF-COF, and then let it stand at room temperature for no less than 72 hours. Step 2: Press the pre-composite fluororubber on a two-roll mill for 5.5 minutes to obtain a semi-transparent two-roll plasticized fluororubber; Step 3: Add process aids, reinforcing agents and chitosan-based solvent-responsive self-healing microcapsules to open-milled plasticized fluororubber. After a first mixing of 7 minutes, add carbon nanotube masterbatch and mix for a second time of 2.2 minutes to obtain the compounded composite. Step 4: Add the remaining vulcanizing agent and TAIC-70 to the compound, make at least 5 triangular bags and mix three times for 2.2 minutes each. Control the gap between the rollers of the open mill to be less than 1 mm, pass through the thin mill at least 10 times, then sheet and cool and let it stand at room temperature for at least 72 hours to obtain the compound to be vulcanized. Step 5: The rubber compound to be vulcanized is subjected to two-stage vulcanization treatment: a first-stage vulcanization using a flat vulcanizing machine and a second-stage vulcanization using an oven. The temperature of the first-stage vulcanization is 176℃ and the time is 8 minutes, while the temperature of the second-stage vulcanization is 200℃ and the time is 6 hours, to obtain the finished lithium battery positive electrode film oil-based coating roller composite material. Example 3

[0045] A composite material for oil-based coating rollers of lithium battery positive electrode film comprises 100 parts by weight of fluororubber, 28 parts by weight of reinforcing agent, 7 parts by weight of process aid, 22 parts by weight of carbon nanotube masterbatch, 3 parts by weight of vulcanizing agent, and 7 parts by weight of TAIC-70.

[0046] in: Fluororubber was in situ covalently grafted with a triazine-based perfluorinated covalent organic framework PF-COF, and the amount of PF-COF added during grafting was 4.5 parts.

[0047] The reinforcing agent is a boron-nitrogen two-dimensional hybrid nanosheet obtained by combining hydroxylated hexagonal boron nitride and boron-doped graphene in a mass ratio of 7:3.

[0048] The preparation method of the reinforcing agent includes step ① adding hydroxylated hexagonal boron nitride to anhydrous ethanol, stirring at room temperature for 10 min, and then ultrasonically dispersing at 300W for 40 min to obtain a pre-dispersion liquid; step ② adding boron-doped graphene to the pre-dispersion liquid and stirring continuously for 15 min, and then ultrasonically dispersing at 400W for 60 min to obtain a mixed dispersion liquid with a solid content of 10%; step ③ centrifuging the mixed dispersion liquid at a speed of 8000 r / min for 20 min to obtain a solid precipitate, and then vacuum drying at 60℃ for 12 h to obtain the finished two-dimensional hybrid nanosheets.

[0049] Processing aids include PE wax and WS180 in a mass ratio of 2:1. The carbon nanotube masterbatch is a pre-dispersed carbon nanotube masterbatch with a mass concentration of 11%, obtained by mixing and internally mixing with fluororubber. The vulcanizing agent is 52wt% bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane adsorbent powder.

[0050] To further reduce solvent wettability and achieve self-healing, the lithium battery positive electrode film oil-coating roller composite material in this application embodiment also includes 3.5 parts by weight of zinc dodecylphosphonate and 5.0 parts by weight of chitosan-based solvent-responsive self-healing microcapsules.

[0051] The preparation method of chitosan-based solvent-responsive self-healing microcapsules includes the following steps: Step ① Adding 3 parts by weight of chitosan to 97 parts by weight of 2.5% glacial acetic acid aqueous solution and stirring to dissolve to obtain chitosan aqueous solution; Step ② Adding a fluorinated prepolymer crosslinking solution dropwise to the chitosan aqueous solution, controlling the mixing mass ratio of the fluorinated prepolymer crosslinking solution to the chitosan aqueous solution to be 1:4, and the fluorinated prepolymer crosslinking solution is obtained by mixing a fluorinated prepolymer and an isocyanate crosslinking agent at a mass ratio of 95:5, then adding 2% by mass of Span-80 and mixing and stirring, and obtaining an oil-in-water emulsion by high-speed emulsification reaction controlled at a stirring speed of 3000 r / min for 30 min; Step ③ Adding 5% by mass of ammonia water dropwise to the oil-in-water emulsion to adjust the pH value to 7.5, and stirring continuously to solidify, followed by centrifugation, washing, drying, pulverizing and sieving to obtain the final product.

[0052] A method for preparing an oil-based coating roller composite material for lithium battery positive electrode film, used to prepare the oil-based coating roller composite material for lithium battery positive electrode film as described above, includes the following steps: Step 1: Mix fluororubber, PF-COF, zinc dodecylphosphonate and a portion of vulcanizing agent accounting for no more than 20% of the total mass and knead to obtain a pre-composite fluororubber with in-situ grafting and ion crosslinking of PF-COF, and then let it stand at room temperature for no less than 72 hours. Step 2: Press the pre-composite fluororubber on a two-roll mill for 6 minutes to obtain a semi-transparent two-roll plasticized fluororubber. Step 3: Add process aids, reinforcing agents and chitosan-based solvent-responsive self-healing microcapsules to open-milled plasticized fluororubber. After a first mixing of 8 minutes, add carbon nanotube masterbatch and mix for a second time of 2.5 minutes to obtain the compound. Step 4: Add the remaining vulcanizing agent and TAIC-70 to the compound, make no less than 5 triangular bags and mix three times for 2.5 minutes each. Control the gap of the open mill to be less than 1 mm, pass through the thin mill at least 10 times, then sheet and cool and let stand at room temperature for no less than 72 hours to obtain the compound to be vulcanized. Step 5: The rubber compound to be vulcanized is subjected to two-stage vulcanization treatment: a first-stage vulcanization using a flat vulcanizing machine and a second-stage vulcanization using an oven. The temperature of the first-stage vulcanization is 178℃ and the time is 8.5 min, while the temperature of the second-stage vulcanization is 205℃ and the time is 6.2 h, to obtain the finished lithium battery positive electrode film oil-based coating roller composite material.

[0053] Comparative Example 1 The difference between Comparative Example 1 and Example 2 is that the fluororubber in Comparative Example 1 was not grafted with PF-COF.

[0054] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that zinc dodecylphosphonate was not added in Comparative Example 2.

[0055] Comparative Example 3 The difference between Comparative Example 3 and Example 2 is that chitosan-based solvent-responsive self-healing microcapsules were not added in Comparative Example 3.

[0056] Comparative Example 4 The difference between Comparative Example 4 and Example 2 is that fumed silica was used as a reinforcing agent in Comparative Example 4.

[0057] Performance testing: 1. Swelling rate: Referring to GB / T1690-2010 "Test method for resistance to liquid of vulcanized rubber or thermoplastic rubber", a 20mm×20mm×2mm sample was used. The dry weight and volume were measured. The sample was then immersed in NMP at a constant temperature of 40℃ for 72h in a sealed environment. The volume swelling rate was calculated after immersion. 2. Volume resistivity: Referring to GB / T 1692-2008 "Determination of Insulation Resistivity of Vulcanized Rubber", a high insulation resistance tester was used to test the resistivity of a 2mm thick sample under a pressure of 1kg and a test voltage of 100V. 3. Reciprocating compression fatigue: Referring to GB / T 7759.1-2015, the compression rate was controlled at 25%, and the compression was cyclically compressed for 100,000 times at 40℃. Surface microcracks were observed and the permanent compression deformation rate was recorded. 4. Wear resistance: Referring to GB / T 1689-2014, Akron wear wheels were used, with a load of 26.7 N and a rotation speed of 72 r / min, and the wear volume was tested for 1 hour.

[0058] The performance test results are shown in Table 1 below.

[0059] Table 1 Performance Test Results Example 1 2.4 <![CDATA[1.4*10 6 ]]> 7.8 0.062 Example 2 1.7 <![CDATA[7.2*10 5 ]]> 6.1 0.045 Example 3 1.1 <![CDATA[3.6*10 5 ]]> 4.3 0.028 Comparative Example 1 4.6 <![CDATA[7.5*10 5 ]]> 9.8 0.087 Comparative Example 2 3.3 <![CDATA[7.1*10 5 ]]> 6.5 0.051 Comparative Example 3 2.1 <![CDATA[7.3*10 5 ]]> 11.6 0.053 Comparative Example 4 4.1 <![CDATA[7.0*10 5 ]]> 13.2 0.115 As shown in Table 1 above, the performance test results of this application demonstrate that the technical solution utilizes in-situ covalently grafted triazine-based perfluorinated covalent organic framework PF-COF, synergistically added boron-nitrogen two-dimensional hybrid nanosheets as a reinforcing agent, carbon nanotube masterbatch, zinc dodecylphosphonate, and chitosan-based solvent-responsive self-healing microcapsules. In Examples 1, 2, and 3, the NMP volume swelling rate, volume resistivity, compression set, and Akron abrasion volume gradually decreased synchronously with increasing addition amounts. This indicates that the lithium battery positive electrode film oil-coated roller composite material prepared by the method described in this application exhibits progressively improved resistance to NMP solvent penetration, antistatic conductivity, reciprocating compression fatigue resistance, and abrasion resistance.

[0060] It is worth mentioning that the absence of in-situ covalent grafting of triazine-based perfluorinated covalent organic framework PF-COF onto fluororubber, the absence of zinc dodecylphosphonate, the absence of chitosan-based solvent-responsive self-healing microcapsules, or the use of fumed silica instead of boron-nitrogen two-dimensional hybrid nanosheets as a reinforcing agent all reduce the NMP swelling resistance, cyclic compression fatigue resistance, and wear resistance of the composite material. Specifically, Comparative Example 3, due to the absence of chitosan-based solvent-responsive self-healing microcapsules, exhibited a significantly increased compression set. Comparative Example 4, due to the use of fumed silica instead of boron-nitrogen two-dimensional hybrid nanosheets as a reinforcing agent, showed a significant increase in NMP volume swelling rate, maximum compression set, and maximum Akron wear volume. Comparative Example 1, due to the absence of triazine-based perfluorinated covalent organic framework PF-COF grafting onto fluororubber, experienced a significant decrease in NMP solvent swelling resistance. Furthermore, the absence of zinc dodecylphosphonate in Comparative Example 2 resulted in a slight decrease in solvent wettability and wear resistance.

[0061] Based on the fact that the volume resistivity values ​​of each comparative example are basically close to those of Example 2, it can be seen that the triazine-based perfluorinated covalent organic framework PF-COF, zinc dodecylphosphonate, chitosan-based solvent-responsive self-healing microcapsules, and reinforcing agents do not damage the conductive network constructed by the carbon nanotube masterbatch, so that the lithium battery positive electrode film oily coating roller composite material obtained by the preparation method of this application has the effect of stable antistatic conductivity.

[0062] In summary, this application provides a composite material for oily coating rollers of lithium-ion battery positive electrode films and its preparation method. This composite material involves in-situ covalent grafting of a triazine-based perfluorinated covalent organic framework (PF-COF) onto fluororubber. This, combined with boron-nitrogen two-dimensional hybrid nanosheets, carbon nanotube masterbatch, and process aids, significantly enhances resistance to strong solvents such as DMF, DMAC, and NMP. This effectively suppresses swelling and deformation during the preparation of the oily coating roller, extending its service life. Furthermore, it improves antistatic properties and surface self-lubrication, reducing downtime and replacement frequency, thus improving production quality and efficiency. Simultaneously, by covalently grafting PF-COF onto the molecular chains of fluororubber, its rigid layered structure restricts the movement of polymer chain segments, and the perfluorinated structure generates polar repulsion to reduce solvent wetting and penetration. The boron-nitrogen two-dimensional hybrid nanosheets form intricate barrier channels, extending the solvent diffusion path, thereby solving the problems of low solvent resistance and short-term failure. The preparation method of this lithium battery positive electrode film oil-coated rubber roller composite material adopts the dynamic ionic cross-linking network formed by zinc dodecylphosphonate and fluororubber, which complements and synergizes with the covalent cross-linking structure. During repeated extrusion deformation, it releases internal stress and inhibits the initiation of microcracks, thereby improving the fatigue resistance. In addition, the chitosan-based solvent-responsive microcapsules are distributed at the component interface, which triggers the rupture when the solvent penetrates the gap, and then seals the defects through in-situ cross-linking, thereby achieving the effect of self-repair of interface damage.

[0063] The terms “first,” “second,” “third,” “fourth,” etc., used in this application (if applicable) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments described herein can be implemented in orders other than those described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, or apparatus that includes a series of steps or units is not necessarily limited to those explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, or apparatus.

[0064] It should be noted that the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. Furthermore, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0065] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A composite material for oil-based coating rollers of lithium battery positive electrode film, characterized in that, It includes 100 parts by weight of fluororubber, 15-28 parts of reinforcing agent, 3-7 parts of processing aid, 12-22 parts of carbon nanotube masterbatch, 2-3 parts of vulcanizing agent, and 4-7 parts of TAIC-70; wherein: The fluororubber is in situ covalently grafted with a triazine-based perfluorinated covalent organic framework PF-COF; The reinforcing agent is a boron-nitrogen two-dimensional hybrid nanosheet obtained by combining hydroxylated hexagonal boron nitride and boron-doped graphene in a mass ratio of 6-7:3-4.

2. The lithium battery positive electrode film oil-based coating roller composite material according to claim 1, characterized in that: The process aids include PE wax and WS180 in a mass ratio of 2:0.9-1; the carbon nanotube masterbatch is a carbon nanotube pre-dispersed masterbatch with a mass concentration of 9-11% obtained by mixing and kneading with fluororubber; the vulcanizing agent is bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane adsorbent powder with a concentration of 48-52 wt%.

3. The lithium battery positive electrode film oil-based coating roller composite material according to claim 1, characterized in that: The amount of PF-COF added is 2.5-4.5 parts.

4. The lithium battery positive electrode film oil-based coating roller composite material according to claim 1, characterized in that: The preparation method of the reinforcing agent includes step ① adding hydroxylated hexagonal boron nitride to anhydrous ethanol, stirring evenly at room temperature and ultrasonically dispersing to obtain a pre-dispersion liquid; step ② adding boron-doped graphene to the pre-dispersion liquid, stirring evenly and ultrasonically dispersing to obtain a mixed dispersion liquid with a solid content of 8-10%; step ③ centrifuging the mixed dispersion liquid to obtain a solid precipitate and vacuum drying to obtain the finished two-dimensional hybrid nanosheets.

5. The lithium battery positive electrode film oil-based coating roller composite material according to claim 4, characterized in that: Step ① involves adding hydroxylated hexagonal boron nitride to anhydrous ethanol, stirring at room temperature for 10 minutes, and then ultrasonically dispersing at 300W for 40 minutes to obtain a pre-dispersion. Step ② involves adding boron-doped graphene to the pre-dispersion and stirring continuously for 15 minutes, followed by ultrasonic dispersion at 400W for 60 minutes to obtain a mixed dispersion with a solid content of 8-10%. Step ③ involves centrifuging the mixed dispersion at 8000 r / min for 20 minutes to obtain a solid precipitate, followed by vacuum drying at 60℃ for 12 hours to obtain the finished two-dimensional hybrid nanosheets.

6. The lithium battery positive electrode film oil-based coating roller composite material according to claim 1, characterized in that: It also includes 2.0-3.5 parts by weight of zinc dodecylphosphonate and 3.0-5.0 parts by weight of chitosan-based solvent-responsive self-healing microcapsules.

7. The lithium battery positive electrode film oil-based coating roller composite material according to claim 6, characterized in that: The preparation method of the chitosan-based solvent-responsive self-healing microcapsules includes the following steps: Step ① Adding 2-3 parts by weight of chitosan to 97-98 parts by weight of 2.5% glacial acetic acid aqueous solution, and dissolving by stirring to obtain a chitosan aqueous solution; Step ② Adding a fluorinated prepolymer crosslinking solution dropwise to the chitosan aqueous solution, and obtaining an oil-in-water emulsion through a high-speed emulsification reaction; Step ③ Adding dilute ammonia dropwise to the oil-in-water emulsion to adjust the pH value to 7.0-7.5, and continuously stirring to solidify, followed by centrifugation, washing, drying, pulverizing and sieving to obtain the final product.

8. The lithium battery positive electrode film oil-based coating roller composite material according to claim 7, characterized in that: The fluorinated prepolymer crosslinking solution is obtained by mixing a fluorinated prepolymer and an isocyanate crosslinking agent at a mass ratio of 95:5, followed by adding 2% Span-80 by mass and stirring. The high-speed emulsification reaction is carried out by controlling the stirring speed at 3000 r / min for 30 min. The mass ratio of the fluorinated prepolymer crosslinking solution to the chitosan aqueous solution is 1:3-4, and the dilute ammonia solution is 5% by mass.

9. A method for preparing an oil-based coating roller composite material for lithium battery positive electrode film, used to prepare the oil-based coating roller composite material for lithium battery positive electrode film as described in any one of claims 6-8, characterized in that, Includes the following steps: Step 1: Mix fluororubber, PF-COF, zinc dodecylphosphonate and a portion of vulcanizing agent and knead to obtain a pre-composite fluororubber with in-situ grafting and ion crosslinking of PF-COF. Step 2: Press the pre-composite fluororubber through a two-roll mill to obtain a semi-transparent two-roll plasticized fluororubber; Step 3: Add process aids, reinforcing agents and chitosan-based solvent-responsive self-healing microcapsules to open-milled plasticized fluororubber. After one mixing, add carbon nanotube masterbatch and mix a second time to obtain a compounded composite. Step 4: Add the remaining vulcanizing agent and TAIC-70 to the compound, and obtain the compound to be vulcanized after three mixing processes. Step 5: The rubber compound to be vulcanized is subjected to two-stage vulcanization treatment to obtain the finished lithium battery positive electrode film oil-based coating roller composite material.

10. The method for preparing an oily coating roller composite material for lithium battery positive electrode film according to claim 9, characterized in that: In step 1, the vulcanizing agent accounts for no more than 20% of the total mass of the vulcanizing agent, and the pre-composite fluororubber is left to stand at room temperature for no less than 72 hours after obtaining it; in step 2, the pressing time is 5-6 minutes; in step 3, the first mixing time is 6-8 minutes, and the second mixing time is 2-2.5 minutes; in step 4, the third mixing time is 2-2.5 minutes, and no less than 5 triangular slabs are formed, the roller gap of the open mill is controlled to be less than 1 mm, and after passing through the thin mill at least 10 times, the sheet is cooled and left to stand at room temperature for no less than 72 hours; in step 5, the two-stage vulcanization process includes a first-stage vulcanization using a flat vulcanizing machine and a second-stage vulcanization using an oven; the temperature of the first-stage vulcanization is 175-178℃, and the time is 7.5-8.5 minutes; the temperature of the second-stage vulcanization is 195-205℃, and the time is 5.8-6.2 hours.