Multifunctional lithium battery protective coating and preparation method thereof

Abstract

The invention discloses a multifunctional lithium battery protective coating and a preparation method thereof, and belongs 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-methyl pyrrolidone, 2-8 parts of a composite heat stabilizer and 3-8 parts of a composite flame retardant, and the composite heat stabilizer is prepared from the following raw materials: 4-hydroxyphthalic anhydride, decafluorobiphenyl, 3, 4, 9, 10-tetramethyl-1, 3-pentanediol monoisobutyrate, 1-3 parts of 2, 3, 5-tetramethyl-1, 3-pentanediol monoisobutyrate, 1-3 parts of 1, 3-pentanediol monoisobutyrate, 1-3 parts of 1, 3-pentanediol monoisobutyrate, 1-3 parts of 1, 3-pentanediol According to the present invention, the composite flame retardant is prepared from the following raw materials: eugenol, 1, 3-bis-(3-aminopropyl)-1, 1, 3, 3-tetramethyldisiloxane, paraformaldehyde, trifluoroethyl methacrylate and divinyl benzene, and the coating material prepared by using the method has characteristics of excellent thermal stability, excellent flame retardation and excellent chemical corrosion resistance.

Description

Technical Field

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

[0002] With the wide application of lithium-ion batteries in the fields of electric vehicles, energy storage systems, and consumer electronics, their safety and service life have become the key bottlenecks restricting the development of the industry. Currently, commercial lithium battery systems (such as ternary cathode / graphite anode, lithium iron phosphate / graphite anode, etc.) still have significant safety hazards under extreme conditions such as thermal runaway, electrolyte corrosion, and mechanical abuse. Traditional protection methods (such as separator modification, electrolyte additives) are difficult to meet the compound safety protection requirements of high-energy density battery systems. In this context, multifunctional lithium battery protection 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-resistant barrier construction, and flame retardancy and explosion suppression.

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

[0004] The purpose of the present invention is to provide a multifunctional lithium battery protection 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 purpose, 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 alumina, 13-23 parts of N-methylpyrrolidone, 2-8 parts of a composite heat stabilizer, and 3-8 parts of a composite flame retardant. Among them, 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.

[0007] Preferably, the preparation method of the composite heat stabilizer includes the following steps:

[0008] Q1: Add 4-hydroxyphthalic anhydride to tetrahydrofuran, stir to dissolve, then add triethylamine, continue to stir, and then carry out a heating reflux reaction. After the reaction is completed, add toluene, rotary evaporate, and then transfer the product to a constant temperature oil bath. Subsequently, dropwise add a tetrahydrofuran solution containing decafluorobiphenyl. After the dropping is completed, carry out a condensation reflux reaction. 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 evenly, and then carry out a heating reaction. After the reaction is completed, wash and freeze-dry to obtain Compound 2;

[0010] Q3: Add Compound 1 and Compound 2 to N,N-dimethylformamide, stir and react to obtain a mixed solution, and then continue to react by heating. After the reaction is completed, cool down, add triethylamine and acetic anhydride, precipitate, filter, wash, and vacuum dry to obtain the composite heat stabilizer.

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

[0012]

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

[0014] Preferably, in Q1, the dosage 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 temperature is 4 - 6 h.

[0015] Preferably, in Q2, the dosage 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 dosage 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 includes the following steps:

[0018] S1: Add eugenol, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde and absolute ethanol into a container, stir and mix evenly, then transfer to a constant temperature oil bath. Under a nitrogen atmosphere, stir and heat under constant reflux for reaction. After the reaction is completed, perform rotary evaporation, add chloroform for dilution, wash, extract and wash, collect the oily liquid, dry, filter, and perform rotary evaporation to obtain monomer 1;

[0019] S2: Add monomer 1 and azobisisobutyronitrile into trifluoroethyl methacrylate and divinylbenzene, stir and mix to obtain a mixed solution. Then add deionized water into the container, slowly dropwise add the mixed solution while stirring. After the addition is completed, continue stirring, and then perform oil bath magnetic stirring reaction, wash, and dry to obtain the composite flame retardant.

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

[0021]

[0022] The results of mass spectrometry analysis are: 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 dosage ratio of eugenol, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde, and absolute 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 dosage 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 continuous stirring time is 20 - 30 min, the temperature of the oil bath magnetic stirring reaction is 60 - 65 °C, the reaction time is 20 - 24 h, and the stirring speed is 600 - 800 rpm.

[0025] Preferably, a preparation method of a multifunctional lithium battery protection coating includes the following steps:

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

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

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

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

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

[0031] 2. The composite heat stabilizer prepared in the present invention is added 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 heat stabilizer need to absorb a large amount of heat to break, delaying the initial temperature of thermal decomposition. The six-membered rings contained can enhance the molecular chain rigidity and inhibit the movement of chain segments at high temperatures, thereby improving the thermal stability of the coating. The fluorine atoms contained 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 composite flame retardant prepared in the present invention is added 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 silica char layer under high temperature conditions to isolate oxygen and heat. The fluorine-containing component contained releases fluorine radicals during decomposition, captures the active radicals in the combustion chain reaction, and inhibits flame propagation, thereby improving the flame retardancy of the coating. At the same time, the siloxane bond has a high bond energy and is resistant to high-temperature decomposition. The strong electronegativity of the fluorine-containing group enhances the intermolecular force and increases the glass transition temperature of the coating, delaying thermal degradation. Specific embodiments

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0034] Example 1: This example discloses a preparation method of a composite heat stabilizer, which includes the following steps:

[0035] Q1: Add 5.9 g of 4-hydroxyphthalic anhydride to 100 mL of tetrahydrofuran, stir to dissolve, then add 4.5 g of triethylamine, continue to stir, and then carry out a heating reflux reaction at 135 °C for 6 h. After the reaction is completed, add toluene, rotary evaporate, and then transfer the product to an 80 °C constant temperature oil bath. Subsequently, dropwise add 30 mL of a tetrahydrofuran solution containing 2.8 g of decafluorobiphenyl. After the dropping is completed, carry out a condensation reflux reaction for 4 h. After the reaction is completed, precipitate, filter, precipitate, wash, and vacuum dry to obtain Compound 1;

[0036] Q2: Add 2.4 g of 3,4,9,10-perylene tetracarboxylic 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 evenly, heat and react. After the reaction is completed, 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 to 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 dry under vacuum to obtain a composite heat stabilizer.

[0038] This example discloses a preparation method of a composite flame retardant, which includes the following steps:

[0039] S1: Add 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 absolute ethanol to a container. After stirring and mixing evenly, transfer it to an oil bath maintained at 100 °C. Under a nitrogen atmosphere, stir and heat under constant reflux for 24 h. After the reaction is completed, perform rotary evaporation, add chloroform for dilution, wash, extract and wash, collect the oily liquid, dry, filter, and perform rotary evaporation 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, and slowly dropwise add the mixed solution while stirring. After the addition is complete, continue stirring for 30 min, and then perform an oil bath magnetic stirring reaction at 65 °C for 24 h with a stirring speed of 600 rpm. Wash and dry to obtain the composite flame retardant.

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

[0042] This example discloses a preparation method of a multifunctional lithium battery protection coating, which includes 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 h to obtain a mucus. Then add conductive carbon black to the mucus, stir and mix at 2500 rpm for 45 min, and then slowly add alumina and continue to stir and mix at 3000 rpm for 80 min 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 min, and filter to obtain the multifunctional lithium battery protection coating.

[0045] Example 2: This example discloses a preparation method of a composite heat stabilizer, which includes the following steps:

[0046] Q1: Add 5.1 g of 4-hydroxyphthalic anhydride to 100 mL of tetrahydrofuran, stir to dissolve, then add 4.2 g of triethylamine, continue stirring, and then carry out a reflux reaction at 135 °C for 6 h. After the reaction is completed, add toluene, rotary evaporate, and then transfer the product to an 80 °C constant temperature oil bath. Subsequently, dropwise add 30 mL of a tetrahydrofuran solution containing 2.5 g of decafluorobiphenyl. After the dropwise addition is completed, carry out a condensation reflux reaction for 4 h. After the reaction is completed, precipitate, filter, precipitate, wash, and vacuum dry 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. After stirring and mixing evenly, carry out a heating reaction. After the reaction is completed, 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 and react to obtain a mixed solution. Subsequently, continue the reaction by heating. 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 heat stabilizer.

[0049] This example discloses a preparation method of a composite flame retardant, including the following steps:

[0050] S1: Add 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 absolute ethanol to a container. After stirring and mixing evenly, transfer to a 100 °C constant temperature oil bath. Under a nitrogen atmosphere, carry out a stirring constant temperature reflux heating reaction for 24 h. After the reaction is completed, rotary evaporate, add chloroform for dilution, wash, extract and wash, collect the oily liquid, dry, filter, and rotary evaporate 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, and slowly dropwise add the mixed solution while stirring. After the dropwise addition is completed, continue stirring for 30 min, and then carry out a 65 °C oil bath magnetic stirring reaction for 24 h with a stirring speed of 600 rpm. Wash and dry to obtain the composite flame retardant.

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

[0053] This embodiment discloses a preparation method of a multifunctional lithium battery protective coating, including the following steps:

[0054] Step 1: Add polyvinylidene fluoride and N-methylpyrrolidone into a high-speed disperser, heat and stir at 85 °C for 4 h to obtain a mucus. Then add conductive carbon black into the mucus, stir and mix at 2500 rpm for 45 min. Subsequently, slowly add alumina and continue to stir and mix at 3000 rpm for 80 min to obtain a premix.

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

[0056] Example 3: This embodiment discloses a preparation method of a composite heat stabilizer, including the following steps:

[0057] Q1: Add 6.8 g of 4-hydroxyphthalic anhydride into 100 mL of tetrahydrofuran, stir to dissolve, then add 4.8 g of triethylamine, continue to stir, and then carry out a heating reflux reaction at 135 °C for 6 h. After the reaction is completed, add toluene, rotary evaporate, and then transfer the product to an 80 °C constant temperature oil bath. Subsequently, dropwise add 30 mL of a tetrahydrofuran solution containing 3.4 g of decafluorobiphenyl. After the dropwise addition is completed, carry out a condensation reflux reaction for 4 h. After the reaction is completed, precipitate, filter, precipitate, wash, and vacuum dry to obtain Compound 1.

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

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

[0060] This embodiment discloses a preparation method of a composite flame retardant, including the following steps:

[0061] S1: Add 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 absolute ethanol into a container. After stirring and mixing evenly, transfer it to an oil bath at 100 °C. Under a nitrogen atmosphere, stir and heat under constant reflux for 24 h. After the reaction is completed, perform rotary evaporation, add chloroform for dilution, wash, extract and wash, collect the oily liquid, dry, filter, and perform rotary evaporation to obtain monomer 1;

[0062] S2: Add 0.62 g of monomer 1 and 0.048 g of azobisisobutyronitrile into 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 into the container, slowly dropwise add the mixed solution while stirring. After the addition is completed, continue stirring for 30 min, and then carry out an oil bath magnetic stirring reaction at 65 °C for 24 h with a stirring speed of 600 rpm. Wash and dry to obtain the composite flame retardant.

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

[0064] This example discloses a preparation method of a multifunctional lithium battery protection coating, including the following steps:

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

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

[0067] Example 4: This example discloses a preparation method of a composite heat stabilizer, including the following steps:

[0068] Q1: Add 5.5 g of 4-hydroxyphthalic anhydride into 100 mL of tetrahydrofuran, stir to dissolve, then add 4.3 g of triethylamine, continue stirring, and then carry out a heating reflux reaction at 135 °C for 6 h. After the reaction is completed, add toluene, perform rotary evaporation, and then transfer the product to an oil bath at 80 °C. Subsequently, dropwise add 30 mL of a tetrahydrofuran solution containing 2.6 g of decafluorobiphenyl. After the addition is completed, carry out a condensation reflux reaction for 4 h. After the reaction is completed, precipitate, filter, precipitate, wash, and vacuum dry to obtain compound 1;

[0069] Q2: Add 2.2 g of 3,4,9,10-perylene tetracarboxylic dianhydride and 4.2 g of dicyandiamide to a mixed solution of 42 mL of N,N-dimethylformamide and 43 mL of ethylene glycol. After stirring and mixing evenly, heat for reaction. After the reaction is completed, wash and freeze-dry to obtain Compound 2;

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

[0071] This example discloses a preparation method of a composite flame retardant, including the following steps:

[0072] S1: Add 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 absolute ethanol to a container. After stirring and mixing evenly, transfer it to an oil bath at a constant temperature of 100 °C. Under a nitrogen atmosphere, stir and heat under constant reflux for 24 h. After the reaction is completed, perform rotary evaporation, add chloroform for dilution, wash, extract and wash, collect the oily liquid, dry, filter, and perform rotary evaporation 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 dropwise add the mixed solution while stirring. After the addition is completed, continue to stir for 30 min, and then perform an oil bath magnetic stirring reaction at 65 °C for 24 h. The stirring speed is 600 rpm. Wash and dry to obtain the composite flame retardant.

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

[0075] This example discloses a preparation method of a multifunctional lithium battery protection coating, including 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 h to obtain a mucus. Then add conductive carbon black to the mucus, stir and mix at 2500 rpm for 45 min, and then slowly add alumina, and continue to stir and mix at 3000 rpm for 80 min 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 min, filter to obtain the multifunctional lithium battery protection coating.

[0078] Example 5: This example discloses a preparation method of a composite heat stabilizer, including the following steps:

[0079] Q1: Add 6.3 g of 4-hydroxyphthalic anhydride to 100 mL of tetrahydrofuran, stir to dissolve, then add 4.6 g of triethylamine, continue to stir, then carry out a reflux reaction at 135 °C for 6 h. After the reaction is completed, add toluene, rotary evaporate, then transfer the product to an 80 °C constant temperature oil bath, and then dropwise add 30 mL of a tetrahydrofuran solution containing 3.2 g of decafluorobiphenyl. After the dropping is completed, carry out a condensation reflux reaction for 4 h. After the reaction is completed, precipitate, filter, precipitate, wash, and vacuum dry 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 evenly, heat and react. After the reaction is completed, wash and freeze-dry to obtain Compound 2;

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

[0082] This example discloses a preparation method of a composite flame retardant, including the following steps:

[0083] S1: Add 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 absolute ethanol to a container, stir and mix evenly, transfer to a 100 °C constant temperature oil bath, and under a nitrogen atmosphere, stir and carry out a constant temperature reflux reaction for 24 h. After the reaction is completed, rotary evaporate, add chloroform for dilution, wash, extract and wash, collect the oily liquid, dry, filter, and rotary evaporate 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 a container, slowly dropwise add the mixed solution while stirring. After the addition is complete, continue stirring for 30 min, then carry out a magnetic stirring reaction in an oil bath at 65 °C for 24 h, with a stirring speed of 600 rpm. Wash and dry to obtain a composite flame retardant.

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

[0086] This example discloses a preparation method of a multifunctional lithium battery protection coating, including the following steps:

[0087] Step 1: Add polyvinylidene fluoride and N-methylpyrrolidone to a high-speed disperser, heat and stir and mix at 85 °C for 4 h to obtain a mucus. Then add conductive carbon black to the mucus, stir and mix at 2500 rpm for 45 min, and then slowly add alumina and continue to stir and mix at 3000 rpm for 80 min 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 min, and filter to obtain the multifunctional lithium battery protection coating.

[0089] Comparative Example 1: Compared with Example 1, in the process of preparing the multifunctional lithium battery protection coating in Comparative Example 1, the composite heat stabilizer is not added, and other conditions remain unchanged.

[0090] Comparative Example 2: Compared with Example 1, in the process of preparing the multifunctional lithium battery protection coating in Comparative Example 2, the composite flame retardant is not added, and other conditions remain unchanged.

[0091] Experimental Example: Test the performance of the multifunctional lithium battery protection coatings prepared in Examples 1-5 and Comparative Examples 1-2. Test the thermal stability performance of the samples according to the thermogravimetric analysis method, test the corrosion resistance performance of the samples according to GB / T 2423.17-2008, and test the flame retardant performance of the samples 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 peels off or powders 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 peeling and powdering 9 Comparative Example 2 2.61 No 23

[0094] As can be seen from the test results in Table 1, the multifunctional lithium battery protection coatings prepared in Examples 1-5 of the present invention have excellent thermal stability, flame retardancy and corrosion resistance. By comparing Comparative Example 1 with Examples 1-5, it can be seen that adding a composite heat stabilizer can effectively improve the thermal stability and corrosion resistance of the multifunctional lithium battery protection coating; by comparing Comparative Example 2 with Examples 1-5, it can be seen that adding a composite flame retardant can effectively improve the thermal stability and flame retardancy of the multifunctional lithium battery protection coating.

[0095] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

[0096] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the present invention to the specific embodiments only. Obviously, many modifications and changes can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A multifunctional lithium battery protection coating, characterized in that It consists of the following components by weight: 13-18 parts of polyvinylidene fluoride, 5-8 parts of conductive carbon black, 20-30 parts of alumina, 13-23 parts of N-methylpyrrolidone, 2-8 parts of a composite heat stabilizer, and 3-8 parts of a composite flame retardant. Among them, 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.

2. The multifunctional lithium battery protection coating according to claim 1, characterized in that, The preparation method of the composite heat stabilizer includes the following steps: Q1: Add 4-hydroxyphthalic anhydride to tetrahydrofuran, stir to dissolve, then add triethylamine, continue stirring, and then carry out a heating reflux reaction. After the reaction is completed, add toluene, rotary evaporation, and then transfer the product to a constant-temperature oil bath. Subsequently, dropwise add a tetrahydrofuran solution containing decafluorobiphenyl. After the addition is completed, carry out a condensation reflux reaction. 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. After stirring and mixing evenly, carry out a heating reaction. After the reaction is completed, wash and freeze-dry to obtain Compound 2. Q3: Add Compound 1 and Compound 2 to N,N-dimethylformamide, stir and react to obtain a mixed solution. Subsequently, continue heating and reacting. After the reaction is completed, cool down, add triethylamine and acetic anhydride, precipitate, filter, wash, and vacuum dry to obtain the composite heat stabilizer.

3. The multifunctional lithium battery protection coating according to claim 2, wherein, In Q1, the dosage 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 temperature is 4-6 h.

4. The multifunctional lithium battery protection coating according to claim 2, wherein, In Q2, the dosage 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.

5. The multifunctional lithium battery protection coating according to claim 2, characterized in that, In Q3, the dosage 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.

6. The multifunctional lithium battery protection coating according to claim 1, characterized in that The preparation method of the composite flame retardant includes the following steps: S1: Add eugenol, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde, and absolute ethanol to a container. After stirring and mixing evenly, transfer it to a constant-temperature oil bath. Under a nitrogen atmosphere, stir and carry out a constant-temperature reflux heating reaction. After the reaction is completed, carry out rotary evaporation, add chloroform for dilution, wash, extract and wash, collect the oily liquid, dry, filter, and carry out rotary evaporation to obtain Monomer 1. S2: Add monomer 1 and azobisisobutyronitrile into trifluoroethyl methacrylate and divinylbenzene, stir and mix to obtain a mixed solution. Then add deionized water into a container, slowly dropwise add the mixed solution while stirring. After the addition is completed, continue stirring, and then carry out an oil bath magnetic stirring reaction, wash, and dry to obtain a composite flame retardant.

7. A multifunctional lithium battery protection coating according to claim 6, characterized in that, In the said S1, the dosage ratio of eugenol, 1,3-bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, paraformaldehyde and absolute 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.

8. A multifunctional lithium battery protection coating according to claim 6, characterized in that, In the said S2, the dosage 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 continuous stirring time is 20 - 30 min, the temperature of the oil bath magnetic stirring reaction is 60 - 65 °C, the reaction time is 20 - 24 h, and the stirring speed is 600 - 800 rpm.

9. The preparation method of a multifunctional lithium battery protection coating according to any one of claims 1-8, characterized in that, It includes the following steps: Step 1: Add polyvinylidene fluoride and N-methylpyrrolidone into a high-speed disperser, heat and stir to mix to obtain a mucus. Then add conductive carbon black into the mucus, stir and mix, and then slowly add alumina and continue to stir and mix to obtain a premix. Step 2: Add the composite heat stabilizer and the composite flame retardant into the premix, stir and mix, and filter to obtain a multifunctional lithium battery protection coating.

10. The preparation method of a multifunctional lithium battery protection coating according to claim 9, characterized in that, In the said Step 1, the temperature of heating and stirring is 80 - 85 °C, the time is 2 - 4 h, the stirring time is 30 - 45 min, the speed is 2500 - 3000 rpm, the continuous stirring time is 60 - 80 min, and the speed is 3000 - 3200 rpm; in the said Step 2, the stirring time is 15 - 20 min, and the speed is 200 - 500 rpm.

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