A multifunctional lithium battery protective coating and preparation method thereof

Abstract

The present invention discloses a multifunctional lithium battery protective coating and a preparation method thereof, belonging to the technical field of lithium battery protective coating production. The multifunctional lithium battery protective coating is composed of the following components in parts by weight: 13-18 parts of polyvinylidene fluoride, 5-8 parts of conductive carbon black, 20-30 parts of aluminum oxide, 13-23 parts of N-methylpyrrolidone, 2-8 parts of a composite heat stabilizer, and 3-8 parts of a composite flame retardant, wherein the raw materials for preparing the composite heat stabilizer include 4-hydroxyphthalic anhydride, decafluorobiphenyl, 3,4,9,10-perylenetetracarboxylic dianhydride, and dicyandiamide; the raw materials for preparing the composite flame retardant include eugenol, 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde, trifluoroethyl methacrylate, and divinylbenzene. The coating prepared by the method has excellent thermal stability, flame retardancy, and chemical corrosion resistance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium battery protective coating production, and in particular relates to a multifunctional lithium battery protective coating and a preparation method thereof. Background Art

[0002] With the widespread application of lithium-ion batteries in electric vehicles, energy storage systems, and consumer electronics, their safety and service life have become key bottlenecks restricting the development of the industry. Current commercial lithium battery systems (such as ternary cathode / graphite anode, lithium iron phosphate / graphite anode, etc.) still have significant safety risks under extreme conditions such as thermal runaway, electrolyte corrosion, and mechanical abuse. Traditional protection methods (such as diaphragm modification and electrolyte additives) can no longer meet the complex safety protection needs of high-energy-density battery systems. In this context, multifunctional lithium battery protective coatings, as an emerging surface protection technology, are becoming a research hotspot in the field of battery safety because they can simultaneously achieve synergistic effects such as thermal stability enhancement, corrosion barrier construction, and flame retardancy and explosion suppression.

[0003] Patent CN118027753B discloses a nano-insulating water-based coating for lithium batteries and a preparation method thereof. The nano-insulating water-based coating comprises the following raw materials in parts by weight: 8-12 parts of a binder, 45-50 parts of water, 3-5 parts of a flame retardant, and 2-4 parts of a thickener; wherein the nano-insulating water-based coating further comprises 5-8 parts of a continuous-effect functional agent and 3-4 parts of a synergist based on nano-SiO2 modification. The nano-insulating water-based coating of this invention uses a binder and water in combination with a flame retardant and a thickener. By adding a continuous-effect functional agent and a synergist based on nano-SiO2 modification, the two are coordinated and formulated to optimize the insulation, flame retardancy, and adhesion properties of the product. The performance of the product can be improved in a coordinated manner, and the salt and alkali stability of the product is significant. However, the thermal stability, flame retardancy, and chemical corrosion resistance of the water-based coating prepared by this method still have room for improvement. Summary of the Invention

[0004] The purpose of the present invention is to provide a multifunctional lithium battery protective coating and a preparation method thereof, which are used to solve the technical problems of poor thermal stability, flame retardancy and chemical corrosion resistance of the coating in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention provides a multifunctional lithium battery protective coating, which is composed of the following components in parts by weight: 13-18 parts of polyvinylidene fluoride, 5-8 parts of conductive carbon black, 20-30 parts of aluminum oxide, 13-23 parts of N-methylpyrrolidone, 2-8 parts of a composite heat stabilizer, and 3-8 parts of a composite flame retardant. The composite heat stabilizer is prepared from 4-hydroxyphthalic anhydride, decafluorobiphenyl, 3,4,9,10-perylenetetracarboxylic dianhydride and dicyandiamide as main raw materials, and the composite flame retardant is prepared from eugenol, 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde, trifluoroethyl methacrylate and divinylbenzene as main raw materials.

[0007] Preferably, the preparation method of the composite thermal stabilizer comprises the following steps:

[0008] Q1: Add 4-hydroxyphthalic anhydride to tetrahydrofuran, stir and dissolve, then add triethylamine, continue stirring, and then heat and reflux to react. After the reaction is completed, add toluene, rotary evaporate, and then transfer the product to a constant temperature oil bath. Then, add a tetrahydrofuran solution containing decafluorobiphenyl dropwise. After the addition is completed, condense and reflux to react. After the reaction is completed, precipitate, filter, precipitate, wash, and vacuum dry to obtain compound 1;

[0009] Q2: Add 3,4,9,10-perylenetetracarboxylic dianhydride and dicyandiamide to a mixed solution of N,N-dimethylformamide and ethylene glycol, stir and mix until uniform, heat to react, wash, and freeze-dry to obtain compound 2;

[0010] Q3: Compound 1 and compound 2 are added to N,N-dimethylformamide, stirred to react, and a mixed solution is obtained. The solution is then heated to continue the reaction. After the reaction is completed, the solution is cooled, triethylamine and acetic anhydride are added, precipitated, filtered, washed, and vacuum dried to obtain a composite thermal stabilizer.

[0011] In the above process, the synthetic reaction formula of the composite thermal stabilizer is as follows:

[0012]

[0013] The results of mass spectrometry analysis of compound 1 were: m / z: 621.99 (100.0%), 623.00 (30.7%), 624.00 (6.2%); the results of mass spectrometry analysis of compound 2 were: m / z: 524.10 (100.0%), 525.10 (33.5%), 526.10 (6.1%).

[0014] Preferably, in Q1, the amount ratio of 4-hydroxyphthalic anhydride, triethylamine and decafluorobiphenyl is (5.1-6.8) g: (4.2-4.8) g: (2.5-3.4) g, the heating reflux reaction temperature is 130-140°C, the reaction time is 4-6 h, the temperature of the constant temperature oil bath is 80-85°C, and the condensation reflux reaction time is 4-6 h.

[0015] Preferably, in Q2, the usage ratio of 3,4,9,10-perylenetetracarboxylic dianhydride, dicyandiamide, N,N-dimethylformamide and diethanol is (2-2.8) g: (4-5.3) g: (40-50) mL: (40-55) mL.

[0016] Preferably, in Q3, the usage ratio of compound 1, compound 2, N,N-dimethylformamide, triethylamine and acetic anhydride is (12-25) g: (15-28) g: (30-45) mL: (18-32) mL: (13-30) mL.

[0017] Preferably, the preparation method of the composite flame retardant comprises the following steps:

[0018] S1: Add eugenol, 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde and anhydrous ethanol to a container, stir and mix well, transfer to a constant temperature oil bath, stir and reflux under nitrogen environment, react, after completion of the reaction, rotary evaporate, add chloroform for dilution, wash, extract and wash, collect the oily liquid, dry, filter, and rotary evaporate to obtain monomer 1;

[0019] S2: Monomer 1 and azobisisobutyronitrile are added to trifluoroethyl methacrylate and divinylbenzene, stirred and mixed to obtain a mixed solution, and then deionized water is added to the container, and the mixed solution is slowly added dropwise while stirring. After the addition is completed, stirring is continued, and then an oil bath magnetic stirring reaction is performed, washed, and dried to obtain a composite flame retardant.

[0020] In the above process, the synthetic reaction formula of monomer 1 is as follows:

[0021]

[0022] The results of mass spectrometry analysis were: m / z: 624.34 (100.0%), 625.34 (47.7%), 626.34(11.0%), 626.35 (8.0%), 627.34 (3.0%), 627.35 (2.0%).

[0023] Preferably, in S1, the usage ratio of eugenol, 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde and anhydrous ethanol is (30.01-35.17) g: (17.2-21.6) g: (11.2-13.6) g: (280-330) mL, the temperature of the constant temperature oil bath is 90-110° C., and the heating reaction time is 24-36 h.

[0024] Preferably, in S2, the amount ratio of monomer 1, azobisisobutyronitrile, trifluoroethyl methacrylate, divinylbenzene and deionized water is (0.4-0.62) g: (0.04-0.048) g: (3-3.88) g: (1-1.56) g: (12-28) mL, the stirring time is continued for 20-30 min, the oil bath magnetic stirring reaction temperature is 60-65 ° C, the reaction time is 20-24 h, and the stirring speed is 600-800 rpm.

[0025] Preferably, the method for preparing the multifunctional lithium battery protective coating comprises the following steps:

[0026] Step 1: Add polyvinylidene fluoride and N-methylpyrrolidone into a high-speed disperser, heat and stir to obtain a mucus, then add conductive carbon black to the mucus, stir to mix, and then slowly add alumina, continue stirring and mixing to obtain a premix;

[0027] Step 2: Add the composite heat stabilizer and the composite flame retardant to the premix, stir and mix, and filter to obtain a multifunctional lithium battery protective coating.

[0028] Preferably, in the step 1, the heating and stirring mixing temperature is 80-85°C, the time is 2-4h, the stirring mixing time is 30-45min, the speed is 2500-3000rpm, and the stirring mixing time is continued for 60-80min, and the speed is 3000-3200rpm; in the step 2, the stirring mixing time is 15-20min, and the speed is 200-500rpm.

[0029] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0030] 1. The present invention first prepares a composite heat stabilizer using 4-hydroxyphthalic anhydride, decafluorobiphenyl, 3,4,9,10-perylenetetracarboxylic dianhydride and dicyandiamide as main raw materials, and then prepares a composite flame retardant using eugenol, 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde, trifluoroethyl methacrylate and divinylbenzene as main raw materials. Adding the two to the preparation process of the coating can effectively improve its thermal stability, chemical corrosion resistance and flame retardant properties.

[0031] 2. The present invention adds the prepared composite thermal stabilizer to the lithium battery protective coating, which can effectively improve its thermal stability and chemical corrosion resistance. The carbon-fluorine bonds contained in the composite thermal stabilizer need to absorb a large amount of heat to break, delaying the starting temperature of thermal decomposition. The six-membered ring contained in it can enhance the rigidity of the molecular chain and inhibit the movement of chain segments at high temperatures, thereby improving the thermal stability of the coating. The fluorine atoms contained in it can also reduce the surface energy of the coating, thereby reducing the penetration and adsorption of the electrolyte and improving the corrosion resistance of the coating.

[0032] 3. The present invention adds the prepared composite flame retardant to the lithium battery protective coating, which can effectively improve its flame retardant performance and thermal stability. The silane structure contained in the composite flame retardant can generate a silicon dioxide carbon residue layer under high temperature conditions to isolate oxygen and heat. The fluorine-containing component contains fluorine free radicals when decomposed, captures active free radicals in the combustion chain reaction, and inhibits flame propagation, thereby improving the flame retardancy of the coating. At the same time, the silicon-oxygen bond contained has high bond energy and is resistant to high-temperature decomposition. The strong electronegativity of the fluorine-containing group enhances the interaction force between molecular chains, increases the glass transition temperature of the coating, and delays thermal degradation. DETAILED DESCRIPTION

[0033] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Example 1: This example discloses a method for preparing a composite thermal stabilizer, comprising the following steps:

[0035] Q1: 5.9 g of 4-hydroxyphthalic anhydride was added to 100 mL of tetrahydrofuran and stirred to dissolve. Subsequently, 4.5 g of triethylamine was added and the mixture was stirred continuously. The mixture was then heated at 135°C and refluxed for 6 h. After the reaction, toluene was added and the mixture was evaporated. The product was then transferred to an 80°C constant temperature oil bath. 30 mL of a tetrahydrofuran solution containing 2.8 g of decafluorobiphenyl was then added dropwise. After the addition was completed, the mixture was condensed and refluxed for 4 h. After the reaction was completed, the mixture was precipitated, filtered, washed, and dried in vacuo to obtain compound 1.

[0036] Q2: Add 2.4 g of 3,4,9,10-perylenetetracarboxylic dianhydride and 4.6 g of dicyandiamide to a mixed solution of 45 mL of N,N-dimethylformamide and 47.5 mL of ethylene glycol, stir and mix thoroughly, and heat to react. After the reaction is complete, wash and freeze-dry to obtain compound 2;

[0037] Q3: Add 18.5 g of compound 1 and 21.5 g of compound 2 to 37.5 mL of N,N-dimethylformamide, stir to react, and obtain a mixed solution. Then heat to continue the reaction. After the reaction is completed, cool down, add 25 mL of triethylamine and 21.5 mL of acetic anhydride, precipitate, filter, wash, and vacuum dry to obtain a composite thermal stabilizer.

[0038] This embodiment discloses a method for preparing a composite flame retardant, comprising the following steps:

[0039] S1: 32.58 g of eugenol, 19.4 g of 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 12.4 g of paraformaldehyde, and 305 mL of anhydrous ethanol were added to a container, stirred and mixed uniformly, and then transferred to a constant temperature oil bath at 100°C. Under a nitrogen environment, the mixture was stirred and refluxed for 24 h. After the reaction was completed, the mixture was rotary evaporated, chloroform was added for dilution, washed, extracted and washed, and the oily liquid was collected, dried, filtered, and rotary evaporated to obtain monomer 1;

[0040] S2: Add 0.51 g of monomer 1 and 0.044 g of azobisisobutyronitrile to 3.44 g of trifluoroethyl methacrylate and 1.28 g of divinylbenzene, stir and mix to obtain a mixed solution, then add 20 mL of deionized water to the container, slowly add the mixed solution dropwise while stirring, continue stirring for 30 minutes after the addition is complete, then carry out magnetic stirring reaction in a 65°C oil bath for 24 hours, with a stirring speed of 600 rpm, wash, and dry to obtain a composite flame retardant.

[0041] This embodiment discloses a multifunctional lithium battery protective coating, which is composed of the following ingredients in parts by weight: 15.5 parts of polyvinylidene fluoride, 6.5 parts of conductive carbon black, 25 parts of aluminum oxide, 18 parts of N-methylpyrrolidone, 5 parts of a composite heat stabilizer, and 5.5 parts of a composite flame retardant.

[0042] This embodiment discloses a method for preparing a multifunctional lithium battery protective coating, comprising the following steps:

[0043] Step 1: Add polyvinylidene fluoride and N-methylpyrrolidone to a high-speed disperser, heat and stir at 85°C for 4 hours to obtain a mucus, then add conductive carbon black to the mucus, stir and mix at 2500 rpm for 45 minutes, then slowly add alumina, and continue stirring and mixing at 3000 rpm for 80 minutes to obtain a premix;

[0044] Step 2: Add the composite heat stabilizer and the composite flame retardant to the premix, stir and mix at 300 rpm for 20 minutes, and filter to obtain a multifunctional lithium battery protective coating.

[0045] Example 2: This example discloses a method for preparing a composite thermal stabilizer, comprising the following steps:

[0046] Q1: 5.1 g of 4-hydroxyphthalic anhydride was added to 100 mL of tetrahydrofuran and stirred to dissolve. Subsequently, 4.2 g of triethylamine was added and the mixture was stirred continuously. The mixture was then heated at 135°C and refluxed for 6 h. After the reaction, toluene was added and the mixture was evaporated. The product was then transferred to an 80°C constant temperature oil bath. 30 mL of a tetrahydrofuran solution containing 2.5 g of decafluorobiphenyl was then added dropwise. After the addition was completed, the mixture was condensed and refluxed for 4 h. After the reaction was completed, the mixture was precipitated, filtered, washed, and dried in vacuo to obtain compound 1.

[0047] Q2: Add 2 g of 3,4,9,10-perylenetetracarboxylic dianhydride and 5.3 g of dicyandiamide to a mixed solution of 40 mL of N,N-dimethylformamide and 55 mL of ethylene glycol, stir and mix thoroughly, and heat to react. After the reaction is complete, wash and freeze-dry to obtain compound 2;

[0048] Q3: Add 12 g of compound 1 and 15 g of compound 2 to 30 mL of N,N-dimethylformamide, stir to react, and obtain a mixed solution. Then heat to continue the reaction. After the reaction is completed, cool down, add 18 mL of triethylamine and 30 mL of acetic anhydride, precipitate, filter, wash, and vacuum dry to obtain a composite thermal stabilizer.

[0049] This embodiment discloses a method for preparing a composite flame retardant, comprising the following steps:

[0050] S1: 30.01 g of eugenol, 17.2 g of 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 11.2 g of paraformaldehyde, and 330 mL of anhydrous ethanol were added to a container, stirred and mixed uniformly, and then transferred to a constant temperature oil bath at 100°C. Under a nitrogen atmosphere, the mixture was stirred and refluxed for 24 h. After the reaction was completed, the mixture was rotary evaporated, chloroform was added for dilution, washed, extracted and washed, and the oily liquid was collected, dried, filtered, and rotary evaporated to obtain monomer 1;

[0051] S2: Add 0.4 g of monomer 1 and 0.04 g of azobisisobutyronitrile to 3.88 g of trifluoroethyl methacrylate and 1.56 g of divinylbenzene, stir and mix to obtain a mixed solution, then add 12 mL of deionized water to the container, slowly add dropwise the mixed solution while stirring, continue stirring for 30 minutes after the addition is complete, then carry out magnetic stirring reaction in a 65°C oil bath for 24 hours, with a stirring speed of 600 rpm, wash, and dry to obtain a composite flame retardant.

[0052] This embodiment discloses a multifunctional lithium battery protective coating, which is composed of the following ingredients in parts by weight: 13 parts of polyvinylidene fluoride, 8 parts of conductive carbon black, 30 parts of aluminum oxide, 13 parts of N-methylpyrrolidone, 8 parts of a composite heat stabilizer, and 3 parts of a composite flame retardant.

[0053] This embodiment discloses a method for preparing a multifunctional lithium battery protective coating, comprising the following steps:

[0054] Step 1: Add polyvinylidene fluoride and N-methylpyrrolidone to a high-speed disperser, heat and stir at 85°C for 4 hours to obtain a mucus, then add conductive carbon black to the mucus, stir and mix at 2500 rpm for 45 minutes, then slowly add alumina, and continue stirring and mixing at 3000 rpm for 80 minutes to obtain a premix;

[0055] Step 2: Add the composite heat stabilizer and the composite flame retardant to the premix, stir and mix at 300 rpm for 20 minutes, and filter to obtain a multifunctional lithium battery protective coating.

[0056] Example 3: This example discloses a method for preparing a composite thermal stabilizer, comprising the following steps:

[0057] Q1: 6.8 g of 4-hydroxyphthalic anhydride was added to 100 mL of tetrahydrofuran and stirred to dissolve. Subsequently, 4.8 g of triethylamine was added and the mixture was stirred continuously. The mixture was then heated at 135°C and refluxed for 6 h. After the reaction, toluene was added and the mixture was evaporated. The product was then transferred to an 80°C constant temperature oil bath. 30 mL of a tetrahydrofuran solution containing 3.4 g of decafluorobiphenyl was then added dropwise. After the addition was completed, the mixture was condensed and refluxed for 4 h. After the reaction was completed, the mixture was precipitated, filtered, washed, and dried in vacuo to obtain compound 1.

[0058] Q2: Add 2.8 g of 3,4,9,10-perylenetetracarboxylic dianhydride and 4 g of dicyandiamide to a mixed solution of 50 mL of N,N-dimethylformamide and 40 mL of ethylene glycol, stir and mix thoroughly, and heat to react. After the reaction is complete, wash and freeze-dry to obtain compound 2;

[0059] Q3: Add 25g of compound 1 and 28g of compound 2 to 45mL of N,N-dimethylformamide, stir to react, and obtain a mixed solution. Then heat to continue the reaction. After the reaction is completed, cool down, add 32mL of triethylamine and 13mL of acetic anhydride, precipitate, filter, wash, and vacuum dry to obtain a composite thermal stabilizer.

[0060] This embodiment discloses a method for preparing a composite flame retardant, comprising the following steps:

[0061] S1: 35.17 g of eugenol, 21.6 g of 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 13.6 g of paraformaldehyde and 280 mL of anhydrous ethanol were added to a container, stirred and mixed evenly, and then transferred to a constant temperature oil bath at 100°C. Under a nitrogen environment, stirred and refluxed for reaction for 24 h. After the reaction was completed, the mixture was rotary evaporated, chloroform was added for dilution, washed, extracted and washed, the oily liquid was collected, dried, filtered, and rotary evaporated to obtain monomer 1;

[0062] S2: Add 0.62 g of monomer 1 and 0.048 g of azobisisobutyronitrile to 3 g of trifluoroethyl methacrylate and 1 g of divinylbenzene, stir and mix to obtain a mixed solution, then add 28 mL of deionized water to the container, slowly add the mixed solution dropwise while stirring, continue stirring for 30 minutes after the addition is complete, then carry out magnetic stirring reaction in a 65°C oil bath for 24 hours, with a stirring speed of 600 rpm, wash, and dry to obtain a composite flame retardant.

[0063] This embodiment discloses a multifunctional lithium battery protective coating, which is composed of the following ingredients in parts by weight: 18 parts of polyvinylidene fluoride, 5 parts of conductive carbon black, 20 parts of aluminum oxide, 23 parts of N-methylpyrrolidone, 2 parts of a composite heat stabilizer, and 8 parts of a composite flame retardant.

[0064] This embodiment discloses a method for preparing a multifunctional lithium battery protective coating, comprising the following steps:

[0065] Step 1: Add polyvinylidene fluoride and N-methylpyrrolidone to a high-speed disperser, heat and stir at 85°C for 4 hours to obtain a mucus, then add conductive carbon black to the mucus, stir and mix at 2500 rpm for 45 minutes, then slowly add alumina, and continue stirring and mixing at 3000 rpm for 80 minutes to obtain a premix;

[0066] Step 2: Add the composite heat stabilizer and the composite flame retardant to the premix, stir and mix at 300 rpm for 20 minutes, and filter to obtain a multifunctional lithium battery protective coating.

[0067] Example 4: This example discloses a method for preparing a composite thermal stabilizer, comprising the following steps:

[0068] Q1: 5.5 g of 4-hydroxyphthalic anhydride was added to 100 mL of tetrahydrofuran and stirred to dissolve. Subsequently, 4.3 g of triethylamine was added and the mixture was stirred continuously. The mixture was then heated at 135°C and refluxed for 6 h. After the reaction, toluene was added and the mixture was evaporated. The product was then transferred to an 80°C constant temperature oil bath. 30 mL of a tetrahydrofuran solution containing 2.6 g of decafluorobiphenyl was then added dropwise. After the addition was completed, the mixture was condensed and refluxed for 4 h. After the reaction was completed, the mixture was precipitated, filtered, washed, and dried in vacuo to obtain compound 1.

[0069] Q2: Add 2.2 g of 3,4,9,10-perylenetetracarboxylic dianhydride and 4.2 g of dicyandiamide to a mixed solution of 42 mL of N,N-dimethylformamide and 43 mL of ethylene glycol, stir and mix thoroughly, and heat to react. After the reaction is complete, wash and freeze-dry to obtain compound 2;

[0070] Q3: Add 17g of compound 1 and 20g of compound 2 to 32mL of N,N-dimethylformamide, stir to react, and obtain a mixed solution. Then heat to continue the reaction. After the reaction is completed, cool down, add 21mL of triethylamine and 18mL of acetic anhydride, precipitate, filter, wash, and vacuum dry to obtain a composite thermal stabilizer.

[0071] This embodiment discloses a method for preparing a composite flame retardant, comprising the following steps:

[0072] S1: 31.17 g of eugenol, 18.5 g of 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 11.8 g of paraformaldehyde, and 310 mL of anhydrous ethanol were added to a container, stirred and mixed uniformly, and then transferred to a constant temperature oil bath at 100°C. Under a nitrogen atmosphere, the mixture was stirred and refluxed for 24 h. After the reaction was completed, the mixture was rotary evaporated, chloroform was added for dilution, washed, extracted and washed, and the oily liquid was collected, dried, filtered, and rotary evaporated to obtain monomer 1;

[0073] S2: Add 0.48 g of monomer 1 and 0.042 g of azobisisobutyronitrile to 3.22 g of trifluoroethyl methacrylate and 1.17 g of divinylbenzene, stir and mix to obtain a mixed solution, then add 22 mL of deionized water to the container, slowly add dropwise the mixed solution while stirring, continue stirring for 30 minutes after the addition is complete, then carry out magnetic stirring reaction in a 65°C oil bath for 24 hours, with a stirring speed of 600 rpm, wash, and dry to obtain a composite flame retardant.

[0074] This embodiment discloses a multifunctional lithium battery protective coating, which is composed of the following ingredients in parts by weight: 16 parts of polyvinylidene fluoride, 6 parts of conductive carbon black, 22 parts of aluminum oxide, 15 parts of N-methylpyrrolidone, 4 parts of a composite heat stabilizer, and 4 parts of a composite flame retardant.

[0075] This embodiment discloses a method for preparing a multifunctional lithium battery protective coating, comprising the following steps:

[0076] Step 1: Add polyvinylidene fluoride and N-methylpyrrolidone to a high-speed disperser, heat and stir at 85°C for 4 hours to obtain a mucus, then add conductive carbon black to the mucus, stir and mix at 2500 rpm for 45 minutes, then slowly add alumina, and continue stirring and mixing at 3000 rpm for 80 minutes to obtain a premix;

[0077] Step 2: Add the composite heat stabilizer and the composite flame retardant to the premix, stir and mix at 300 rpm for 20 minutes, and filter to obtain a multifunctional lithium battery protective coating.

[0078] Example 5: This example discloses a method for preparing a composite thermal stabilizer, comprising the following steps:

[0079] Q1: 6.3 g of 4-hydroxyphthalic anhydride was added to 100 mL of tetrahydrofuran and stirred to dissolve. Subsequently, 4.6 g of triethylamine was added and the mixture was stirred continuously. The mixture was then heated at 135°C and refluxed for 6 h. After the reaction, toluene was added and the mixture was evaporated. The product was then transferred to an 80°C constant temperature oil bath. 30 mL of a tetrahydrofuran solution containing 3.2 g of decafluorobiphenyl was then added dropwise. After the addition was completed, the mixture was condensed and refluxed for 4 h. After the reaction was completed, the mixture was precipitated, filtered, washed, and dried in vacuo to obtain compound 1.

[0080] Q2: Add 2.6 g of 3,4,9,10-perylenetetracarboxylic dianhydride and 5.1 g of dicyandiamide to a mixed solution of 48 mL of N,N-dimethylformamide and 51 mL of ethylene glycol. Stir and mix thoroughly, then heat to react. After the reaction is complete, wash and freeze-dry to obtain compound 2.

[0081] Q3: Add 21g of compound 1 and 24g of compound 2 to 41mL of N,N-dimethylformamide, stir to react, and obtain a mixed solution. Then heat to continue the reaction. After the reaction is completed, cool down, add 28mL of triethylamine and 24mL of acetic anhydride, precipitate, filter, wash, and vacuum dry to obtain a composite thermal stabilizer.

[0082] This embodiment discloses a method for preparing a composite flame retardant, comprising the following steps:

[0083] S1: 34.28 g of eugenol, 20.2 g of 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, 12.9 g of paraformaldehyde and 290 mL of anhydrous ethanol were added to a container, stirred and mixed evenly, and then transferred to a constant temperature oil bath at 100°C. Under a nitrogen environment, stirred and refluxed for reaction for 24 h. After the reaction was completed, the mixture was rotary evaporated, chloroform was added for dilution, washed, extracted and washed, the oily liquid was collected, dried, filtered, and rotary evaporated to obtain monomer 1;

[0084] S2: Add 0.59 g of monomer 1 and 0.046 g of azobisisobutyronitrile to 3.66 g of trifluoroethyl methacrylate and 1.43 g of divinylbenzene, stir and mix to obtain a mixed solution, then add 16 mL of deionized water to the container, slowly add dropwise the mixed solution while stirring, continue stirring for 30 minutes after the addition is complete, then carry out magnetic stirring reaction in an oil bath at 65°C for 24 hours, with a stirring speed of 600 rpm, wash, and dry to obtain a composite flame retardant.

[0085] This embodiment discloses a multifunctional lithium battery protective coating, which is composed of the following ingredients in parts by weight: 14 parts of polyvinylidene fluoride, 7 parts of conductive carbon black, 28 parts of aluminum oxide, 21 parts of N-methylpyrrolidone, 7 parts of a composite heat stabilizer, and 7 parts of a composite flame retardant.

[0086] This embodiment discloses a method for preparing a multifunctional lithium battery protective coating, comprising the following steps:

[0087] Step 1: Add polyvinylidene fluoride and N-methylpyrrolidone to a high-speed disperser, heat and stir at 85°C for 4 hours to obtain a mucus, then add conductive carbon black to the mucus, stir and mix at 2500 rpm for 45 minutes, then slowly add alumina, and continue stirring and mixing at 3000 rpm for 80 minutes to obtain a premix;

[0088] Step 2: Add the composite heat stabilizer and the composite flame retardant to the premix, stir and mix at 300 rpm for 20 minutes, and filter to obtain a multifunctional lithium battery protective coating.

[0089] Comparative Example 1: Compared with Example 1, in the process of preparing the multifunctional lithium battery protective coating in Comparative Example 1, no composite thermal stabilizer is added, and other conditions remain unchanged.

[0090] Comparative Example 2: Compared with Example 1, in the process of preparing the multifunctional lithium battery protective coating in Comparative Example 2, no composite flame retardant is added, and other conditions remain unchanged.

[0091] Experimental Example: The performance of the multifunctional lithium battery protective coatings prepared in Examples 1-5 and Comparative Examples 1-2 was tested. The thermal stability of the samples was tested according to the thermogravimetric analysis method, the corrosion resistance of the samples was tested according to GB / T 2423.17-2008, and the flame retardant properties of the samples were tested according to GB / T 31241-2022. The test results are shown in Table 1:

[0092] Table 1

[0093] project Mass reduction rate / % Whether the coating is peeling or powdering Self-extinguishing time / s Example 1 1.89 no 6 Example 2 1.94 no 8 Example 3 1.92 no 9 Example 4 1.95 no 8 Example 5 1.98 no 9 Comparative Example 1 2.56 There is shedding and powdering 9 Comparative Example 2 2.61 no 23

[0094] The test results in Table 1 show that the multifunctional lithium battery protective coatings prepared in Examples 1-5 of the present invention exhibit excellent thermal stability, flame retardancy, and corrosion resistance. A comparison of Comparative Example 1 with Examples 1-5 shows that the addition of a composite thermal stabilizer effectively improves the thermal stability and corrosion resistance of the multifunctional lithium battery protective coating. A comparison of Comparative Example 2 with Examples 1-5 shows that the addition of a composite flame retardant effectively improves the thermal stability and flame retardancy of the multifunctional lithium battery protective coating.

[0095] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

[0096] The preferred embodiments of the present invention disclosed above are intended only to help illustrate the present invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the present invention to specific embodiments. Obviously, many modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A multifunctional lithium battery protective coating, characterized in that: The invention is composed of the following components in parts by weight: 13-18 parts of polyvinylidene fluoride, 5-8 parts of conductive carbon black, 20-30 parts of aluminum oxide, 13-23 parts of N-methylpyrrolidone, 2-8 parts of a composite heat stabilizer, and 3-8 parts of a composite flame retardant, wherein the composite heat stabilizer is prepared from 4-hydroxyphthalic anhydride, decafluorobiphenyl, 3,4,9,10-perylenetetracarboxylic dianhydride and dicyandiamide as main raw materials, and the composite flame retardant is prepared from eugenol, 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde, trifluoroethyl methacrylate and divinylbenzene as main raw materials; The preparation method of the composite thermal stabilizer comprises the following steps: Q1: Add 4-hydroxyphthalic anhydride to tetrahydrofuran, stir and dissolve, then add triethylamine, continue stirring, and then heat and reflux to react. After the reaction is completed, add toluene, rotary evaporate, and then transfer the product to a constant temperature oil bath. Then, add a tetrahydrofuran solution containing decafluorobiphenyl dropwise. After the addition is completed, condense and reflux to react. After the reaction is completed, precipitate, filter, precipitate, wash, and vacuum dry to obtain compound 1; Q2: Add 3,4,9,10-perylenetetracarboxylic dianhydride and dicyandiamide to a mixed solution of N,N-dimethylformamide and ethylene glycol, stir and mix until uniform, heat to react, wash, and freeze-dry to obtain compound 2; Q3: Compound 1 and Compound 2 are added to N,N-dimethylformamide, stirred to react, and a mixed solution is obtained. The solution is then heated to continue the reaction. After the reaction is completed, the solution is cooled, triethylamine and acetic anhydride are added, and the solution is precipitated. The solution is filtered, washed, and vacuum dried to obtain a composite thermal stabilizer. The preparation method of the composite flame retardant comprises the following steps: S1: Add eugenol, 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde and anhydrous ethanol to a container, stir and mix well, transfer to a constant temperature oil bath, stir and reflux under nitrogen environment, react, after completion of the reaction, rotary evaporate, add chloroform for dilution, wash, extract and wash, collect the oily liquid, dry, filter, and rotary evaporate to obtain monomer 1; S2: Monomer 1 and azobisisobutyronitrile are added to trifluoroethyl methacrylate and divinylbenzene, stirred and mixed to obtain a mixed solution, and then deionized water is added to the container, and the mixed solution is slowly added dropwise while stirring. After the addition is completed, stirring is continued, and then an oil bath magnetic stirring reaction is performed, washed, and dried to obtain a composite flame retardant.

2. The multifunctional lithium battery protective coating according to claim 1, characterized in that: In Q1, the usage ratio of 4-hydroxyphthalic anhydride, triethylamine and decafluorobiphenyl is (5.1-6.8) g: (4.2-4.8) g: (2.5-3.4) g, the heating reflux reaction temperature is 130-140° C., the reaction time is 4-6 h, the temperature of the constant temperature oil bath is 80-85° C., and the condensation reflux reaction time is 4-6 h.

3. The multifunctional lithium battery protective coating according to claim 1, characterized in that: In the Q2, the usage ratio of 3,4,9,10-perylenetetracarboxylic dianhydride, dicyandiamide, N,N-dimethylformamide and diethanol is (2-2.8) g: (4-5.3) g: (40-50) mL: (40-55) mL.

4. The multifunctional lithium battery protective coating according to claim 1, characterized in that: In Q3, the usage ratio of compound 1, compound 2, N,N-dimethylformamide, triethylamine and acetic anhydride is (12-25) g: (15-28) g: (30-45) mL: (18-32) mL: (13-30) mL.

5. The multifunctional lithium battery protective coating according to claim 1, characterized in that: In S1, the usage ratio of eugenol, 1,3-bis-(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde and anhydrous ethanol is (30.01-35.17) g: (17.2-21.6) g: (11.2-13.6) g: (280-330) mL, the temperature of the constant temperature oil bath is 90-110° C., and the heating reaction time is 24-36 h.

6. The multifunctional lithium battery protective coating according to claim 1, characterized in that: In S2, the usage ratio of monomer 1, azobisisobutyronitrile, trifluoroethyl methacrylate, divinylbenzene and deionized water is (0.4-0.62) g: (0.04-0.048) g: (3-3.88) g: (1-1.56) g: (12-28) mL, the stirring time is continued for 20-30 min, the reaction temperature under oil bath magnetic stirring is 60-65° C., the reaction time is 20-24 h, and the stirring speed is 600-800 rpm.

7. The method for preparing a multifunctional lithium battery protective coating according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: Add polyvinylidene fluoride and N-methylpyrrolidone into a high-speed disperser, heat and stir to obtain a mucus, then add conductive carbon black to the mucus, stir to mix, and then slowly add alumina, continue stirring and mixing to obtain a premix; Step 2: Add the composite heat stabilizer and the composite flame retardant to the premix, stir and mix, and filter to obtain a multifunctional lithium battery protective coating.

8. The method for preparing a multifunctional lithium battery protective coating according to claim 7, characterized in that: In the step 1, the heating and stirring mixing temperature is 80-85°C, the time is 2-4h, the stirring mixing time is 30-45min, the speed is 2500-3000rpm, and the stirring mixing time is continued for 60-80min, and the speed is 3000-3200rpm; in the step 2, the stirring mixing time is 15-20min, and the speed is 200-500rpm.

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