High-thermal-conductivity adhesive for solid-state batteries and preparation method and application thereof

Abstract

The application relates to the technical field of batteries, in particular to a high-thermal-conductivity adhesive for solid-state batteries and a preparation method and application thereof. A polyacrylic acid adhesive is obtained by adding acrylic acid, propylene flame-retardant monomers, ethanolamine, a eutectic solvent and a photoinitiator. The polyacrylic acid adhesive, an amino-terminated flame retardant, a thermal-conductivity-enhancing fiber and N-methylpyrrolidone are mixed and stirred to obtain adhesive finished products. The adhesive finished products prepared by the application have good flame retardancy, mechanical properties and thermal conductivity, so that the application has a wide application prospect in the technical field of batteries.

Description

Technical Field

[0001] This invention relates to the field of battery technology, specifically to a high thermal conductivity adhesive for solid-state batteries, its preparation method, and its application. Background Technology

[0002] Solid-state batteries, as the next generation of electrochemical energy storage systems, are characterized by replacing the flammable organic liquid electrolytes in traditional lithium-ion batteries with solid-state electrolytes, aiming to address battery safety risks and improve energy density. In the structure of solid-state batteries, binders have evolved from adhesive materials in traditional electrode structures into key interfacial functional materials that determine the upper limit of the battery's overall performance. However, there are still some problems to be overcome with binders used in solid-state batteries, as follows: First, while solid-state batteries have eliminated the main risks associated with flammable liquid electrolytes, electrode active materials (especially high-energy-density lithium-rich, high-nickel cathodes) and some organic solid electrolytes still pose a risk of thermal decomposition under extreme conditions. As a continuous phase spanning the electrode and interface, the binder, if lacking sufficient flame retardancy, can easily become a trigger for thermal runaway propagation, promoting heat spread, increasing fire risk, and weakening battery safety. Second, during solid-state battery operation, the lithiation / delithiation process of electrode materials is accompanied by significant volume changes (the expansion rate of silicon-based anodes can reach over 300%). Binders with insufficient mechanical properties are prone to creep, cracking, or peeling, leading to interfacial contact failure, interruption of ion transport pathways, and a surge in battery internal resistance. Furthermore, solid-state batteries lack internal convective heat dissipation media, making it easy for heat to accumulate locally, and localized overheating can easily accelerate side reactions and aging of materials.

[0003] To overcome the shortcomings of the prior art, the present invention provides a high thermal conductivity adhesive for solid-state batteries, its preparation method and application. Summary of the Invention

[0004] The purpose of this invention is to provide a high thermal conductivity adhesive for solid-state batteries, its preparation method, and its application, so as to solve the problems raised in the prior art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a high thermal conductivity adhesive for solid-state batteries includes the following steps: Step 1: Add choline chloride and urea to deionized water and stir to obtain a eutectic solvent; then add acrylic acid, propylene flame retardant monomer and ethanolamine to the eutectic solvent, stir evenly and then add photoinitiator, stir to dissolve and crosslink under ultraviolet light to obtain polyacrylic acid adhesive. Step 2: Add polyacrylic acid adhesive to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 1; add amino-terminated flame retardant to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 2; mix reaction solution 1, reaction solution 2 and thermally conductive reinforcing fiber, and stir continuously to obtain the finished product.

[0006] In a more optimized manner, choline chloride and urea are added to deionized water and stirred at 80-85℃ for 1.5-2.0h to obtain a eutectic solvent; the molar ratio of choline chloride and urea in the eutectic solvent is 2:(1.0-1.1); acrylic acid, propylene flame retardant monomer, and ethanolamine are added to the eutectic solvent, stirred evenly, and then photoinitiator 2959 is added. After stirring and dissolving, crosslinking is carried out under ultraviolet light irradiation for 30-40min to obtain polyacrylic acid adhesive; the reaction mass ratio of acrylic acid, propylene flame retardant monomer, and ethanolamine is 2.5:(1.3-1.5):1; reaction solution 1, reaction solution 2, and thermally conductive reinforcing fiber are mixed and stirred continuously for 1.5-2.5h to obtain the finished product; wherein the reaction mass ratio of polyacrylic acid adhesive, amino-terminated flame retardant, and thermally conductive reinforcing fiber is 90:(14-15):(9-12).

[0007] A more optimized preparation process for thermally conductive reinforced fibers is as follows: Step S1: Add sepiolite fibers to 1.0-1.2 mol / L hydrochloric acid and stir at 25-30℃ for 4-5 hours. After stirring, filter, wash until neutral, dry, and grind to obtain pretreated sepiolite fibers. Step S2: Mix hexamethylene diisocyanate, triethylenediamine, and toluene, stir evenly, and then add pretreated sepiolite fiber. Impregnate at 60-70℃ for 3-4 hours. After impregnation, remove the fiber, wash and dry it to obtain modified sepiolite fiber. Step S3: Under nitrogen atmosphere, carboxylated carbon nanotubes are added to N-methylpyrrolidone and ultrasonically dispersed for 15-20 min. Then, modified sepiolite fibers are added and reacted at 60-65℃ for 2-3 h. After the reaction is completed, the fibers are removed and dried to obtain thermally conductive reinforced fibers.

[0008] In a more optimized manner, in step S1, the mass-to-volume ratio of sepiolite fiber to hydrochloric acid is 1 g: (16-18) mL; in step S2, the mass-to-volume ratio of the reaction of pretreated sepiolite fiber, hexamethylene diisocyanate, and triethylenediamine is (8-10) g: 100 mL: 1 g; and in step S3, the mass-to-volume ratio of the reaction of carboxylated carbon nanotubes and modified sepiolite fiber is 1: (3-4).

[0009] A more optimized preparation process for the propylene-based flame retardant monomer is as follows: under a nitrogen atmosphere, diethylphosphonic acid and glycidyl methacrylate are added to tetrahydrofuran and reacted continuously at 80-85℃ for 10-15 hours. During the reaction, the polymerization inhibitor 4-methoxyphenol is added. After the reaction is completed, the propylene-based flame retardant monomer is obtained by rotary evaporation.

[0010] The optimal reaction molar ratio of diethylphosphonic acid to glycidyl methacrylate is (1.1-1.2):1.

[0011] A more optimized preparation process for the amino-terminated flame retardant is as follows: 5-amino-tetrazolium is added to deionized water to obtain a 5-amino-tetrazolium solution; hexachlorocyclotriphosphazene and acetonitrile are mixed, stirred and dissolved, and then heated to 50-55℃. The 5-amino-tetrazolium solution is then added, stirred evenly, and sodium hydroxide is added. The mixture is refluxed for 5-6 hours. After the reaction is completed, the mixture is rotary evaporated, dried, dissolved, rotary evaporated again, and dried to obtain the amino-terminated flame retardant.

[0012] The optimal reaction molar ratio of 5-amino-tetrazole to hexachlorocyclotriphosphazene is (6.00-6.05):1.

[0013] An application of a high thermal conductivity adhesive for solid-state batteries involves mixing the prepared high thermal conductivity adhesive, conductive agent, and positive / negative electrode material to obtain a slurry; coating the slurry onto the surfaces of the positive and negative current collectors to obtain positive and negative electrode sheets; and pressing the prepared positive and negative electrode sheets onto both sides of a solid electrolyte to assemble a solid-state lithium battery.

[0014] The beneficial effects of this invention are: The key feature of this invention is that a ring-opening reaction occurs by adding diethylphosphonic acid and glycidyl methacrylate to obtain an propylene-based flame-retardant monomer. This reaction takes place at the epoxy end of the glycidyl methacrylate, while the double bond at the other end remains intact. Therefore, this monomer is both a highly efficient phosphorus-based flame-retardant functional material and an important component of the subsequent polymer network. Furthermore, the propylene-based flame-retardant monomer is mixed with acrylic acid, ethanolamine, and a photoinitiator, and crosslinked under ultraviolet light irradiation to obtain a polyacrylic acid adhesive that forms a highly crosslinked three-dimensional network with excellent flame retardancy and mechanical properties.

[0015] The key feature of this invention is the use of hydrochloric acid to modify the surface of sepiolite fibers, increasing their specific surface area and surface activity, and exposing more silanol groups to obtain pretreated sepiolite fibers. Hexamethylene diisocyanate and triethylenediamine are then added to further modify the pretreated sepiolite fibers. The silanol groups on the surface of the pretreated sepiolite fibers can react with the isocyanate groups, introducing isocyanate groups at the other end, resulting in modified sepiolite fibers. Carboxylated carbon nanotubes are then mixed with the modified sepiolite fibers. The isocyanate groups on the surface of the modified sepiolite fibers can react with the carboxylated carbon nanotubes, which have good thermal and electrical conductivity, to obtain a thermally enhanced fiber. The carbon nanotubes are chemically bonded to the surface of the sepiolite fibers, forming an organic-inorganic hybrid thermally conductive network unit of "sepiolite fiber-HDI-carbon nanotube". This structure avoids the aggregation of carbon nanotubes, allowing them to be uniformly dispersed and construct efficient three-dimensional thermally conductive pathways in subsequent composite processes. Furthermore, the multidirectional distribution and interconnection of sepiolite fibers in the network enable them to collaboratively share the load in multiple directions, effectively promoting the uniform distribution of stress and thus significantly improving the tensile properties of the matrix.

[0016] Furthermore, 5-amino-tetrazazole and hexachlorocyclotriphosphazene are mixed, and a nucleophilic substitution reaction is carried out using imino groups, retaining the side-chain amino groups to obtain an amino-terminated flame retardant. This amino-terminated flame retardant is a high-performance material that integrates highly efficient flame-retardant elements (P, N) with highly reactive amino groups. When polyacrylic acid adhesive and amino-terminated flame retardant are mixed, the -COOH groups in the polyacrylic acid adhesive and the amino groups in the amino-terminated flame retardant can undergo an amidation reaction for chemical cross-linking, resulting in secondary cross-linking reinforcement and forming a dense, strong network with excellent reinforcing effects. Simultaneously, thermally conductive reinforcing fibers are added during mixing, and the final adhesive product possesses excellent flame retardant properties, thermal conductivity, and mechanical properties. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Raw material source: Sepiolite fiber, supplied by Lingshou County Wanzhu Mineral Products Co., Ltd., has a particle size of 5μm; carboxylated carbon nanotubes, supplied by Guangzhou Hongwu Materials Technology Co., Ltd., have a diameter of 20nm.

[0019] Example 1: Step 1: The preparation process of the propylene flame retardant monomer is as follows: Under nitrogen atmosphere, diethylphosphonic acid and glycidyl methacrylate are added to tetrahydrofuran and reacted continuously at 85°C for 15 hours. During the reaction, the polymerization inhibitor 4-methoxyphenol is added. After the reaction is completed, the propylene flame retardant monomer is obtained by rotary evaporation. The molar ratio of diethylphosphonic acid to glycidyl methacrylate is 1.15:1. Step 2: Add choline chloride and urea to deionized water and stir at 85°C for 2.0 h to obtain a eutectic solvent; then add acrylic acid, propylene flame retardant monomer, and ethanolamine to the eutectic solvent, stir evenly, and then add photoinitiator 2959. After stirring to dissolve, crosslink under ultraviolet light for 40 min to obtain polyacrylic acid adhesive; the molar ratio of choline chloride and urea in the eutectic solvent is 2:1.05; the reaction mass ratio of acrylic acid, propylene flame retardant monomer, and ethanolamine is 2.5:1.4:1; Step 3: The preparation process of thermally conductive reinforcing fibers is as follows: Step S1: Add sepiolite fiber to 1.1 mol / L hydrochloric acid and stir at 30℃ for 5 h. After stirring, filter, wash until neutral, dry and grind to obtain pretreated sepiolite fiber; the mass-volume ratio of sepiolite fiber to hydrochloric acid is 1 g: 17 mL. Step S2: Mix hexamethylene diisocyanate, triethylenediamine, and toluene, stir evenly, and then add pretreated sepiolite fiber. Impregnate at 70°C for 4 hours. After impregnation, remove the fiber, wash and dry it to obtain modified sepiolite fiber. The reaction volume-mass ratio of pretreated sepiolite fiber, hexamethylene diisocyanate, and triethylenediamine is 9g:100mL:1g. Step S3: Under nitrogen atmosphere, carboxylated carbon nanotubes were added to N-methylpyrrolidone and ultrasonically dispersed for 20 min. Then, modified sepiolite fibers were added, and the reaction was continued at 65℃ for 3 h. After the reaction was completed, the fibers were removed and dried to obtain thermally conductive reinforced fibers. The mass ratio of carboxylated carbon nanotubes to modified sepiolite fibers was 1:3.5. Step 4: The preparation process of the amino-terminated flame retardant is as follows: 5-amino-tetrazazole is added to deionized water to obtain a 5-amino-tetrazazole solution; hexachlorocyclotriphosphazene and acetonitrile are mixed, stirred and dissolved, and then heated to 55℃. The 5-amino-tetrazazole solution is then added, stirred evenly, and sodium hydroxide is added. The mixture is refluxed for 6 hours. After the reaction is completed, the mixture is rotary evaporated, dried, dissolved, rotary evaporated again, and dried to obtain the amino-terminated flame retardant. The molar ratio of 5-amino-tetrazazole to hexachlorocyclotriphosphazene is 6.03:1. Step 5: Add the polyacrylic acid adhesive to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 1; add the amino-terminated flame retardant to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 2; mix reaction solution 1, reaction solution 2 and thermally conductive reinforcing fiber, and stir continuously for 2.5 hours to obtain the finished product; the mass ratio of polyacrylic acid adhesive, amino-terminated flame retardant and thermally conductive reinforcing fiber is 90:14.5:10.

[0020] Example 2: Step 1: The preparation process of the propylene flame retardant monomer is as follows: Under nitrogen atmosphere, diethylphosphonic acid and glycidyl methacrylate are added to tetrahydrofuran and reacted continuously at 82°C for 12 hours. During the reaction, the polymerization inhibitor 4-methoxyphenol is added. After the reaction is completed, the propylene flame retardant monomer is obtained by rotary evaporation. The molar ratio of diethylphosphonic acid to glycidyl methacrylate is 1.15:1. Step 2: Add choline chloride and urea to deionized water and stir at 82℃ for 1.7h to obtain a eutectic solvent; then add acrylic acid, propylene flame retardant monomer, and ethanolamine to the eutectic solvent, stir evenly, and then add photoinitiator 2959. After stirring to dissolve, crosslink under ultraviolet light for 35min to obtain polyacrylic acid adhesive; the molar ratio of choline chloride and urea in the eutectic solvent is 2:1.05; the reaction mass ratio of acrylic acid, propylene flame retardant monomer, and ethanolamine is 2.5:1.4:1. Step 3: The preparation process of thermally conductive reinforcing fibers is as follows: Step S1: Add sepiolite fiber to 1.1 mol / L hydrochloric acid and stir at 27°C for 4.5 h. After stirring, filter, wash until neutral, dry, and grind to obtain pretreated sepiolite fiber. The mass-volume ratio of sepiolite fiber to hydrochloric acid is 1 g: 17 mL. Step S2: Mix hexamethylene diisocyanate, triethylenediamine, and toluene, stir evenly, and then add pretreated sepiolite fiber. Impregnate at 65°C for 3.5 hours. After impregnation, remove the fiber, wash and dry it to obtain modified sepiolite fiber. The reaction volume-mass ratio of pretreated sepiolite fiber, hexamethylene diisocyanate, and triethylenediamine is 9g:100mL:1g. Step S3: Under nitrogen atmosphere, carboxylated carbon nanotubes were added to N-methylpyrrolidone and ultrasonically dispersed for 17 min. Then, modified sepiolite fibers were added, and the reaction was continued at 62℃ for 2.5 h. After the reaction was completed, the fibers were removed and dried to obtain thermally conductive reinforced fibers. The mass ratio of carboxylated carbon nanotubes to modified sepiolite fibers was 1:3.5. Step 4: The preparation process of the amino-terminated flame retardant is as follows: 5-amino-tetrazazole is added to deionized water to obtain a 5-amino-tetrazazole solution; hexachlorocyclotriphosphazene and acetonitrile are mixed, stirred and dissolved, and then heated to 52℃. The 5-amino-tetrazazole solution is then added, stirred evenly, and sodium hydroxide is added. The mixture is refluxed for 5.5 hours. After the reaction is completed, the mixture is rotary evaporated, dried, dissolved, rotary evaporated again, and dried to obtain the amino-terminated flame retardant. The molar ratio of 5-amino-tetrazazole to hexachlorocyclotriphosphazene is 6.03:1. Step 5: Add the polyacrylic acid adhesive to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 1; add the amino-terminated flame retardant to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 2; mix reaction solution 1, reaction solution 2 and thermally conductive reinforcing fiber, and stir continuously for 2 hours to obtain the finished product; the mass ratio of polyacrylic acid adhesive, amino-terminated flame retardant and thermally conductive reinforcing fiber is 90:14.5:10.

[0021] Example 3: Step 1: The preparation process of the propylene flame retardant monomer is as follows: Under nitrogen atmosphere, diethylphosphonic acid and glycidyl methacrylate are added to tetrahydrofuran and reacted continuously at 80°C for 10 hours. During the reaction, the polymerization inhibitor 4-methoxyphenol is added. After the reaction is completed, the propylene flame retardant monomer is obtained by rotary evaporation. The molar ratio of diethylphosphonic acid to glycidyl methacrylate is 1.15:1. Step 2: Add choline chloride and urea to deionized water and stir at 80°C for 1.5 h to obtain a eutectic solvent; then add acrylic acid, propylene flame retardant monomer, and ethanolamine to the eutectic solvent, stir evenly, and then add photoinitiator 2959. After stirring to dissolve, crosslink under ultraviolet light for 30 min to obtain polyacrylic acid adhesive; the molar ratio of choline chloride and urea in the eutectic solvent is 2:1.05; the reaction mass ratio of acrylic acid, propylene flame retardant monomer, and ethanolamine is 2.5:1.4:1; Step 3: The preparation process of thermally conductive reinforcing fibers is as follows: Step S1: Add sepiolite fiber to 1.1 mol / L hydrochloric acid and stir at 25°C for 4 hours. After stirring, filter, wash until neutral, dry, and grind to obtain pretreated sepiolite fiber. The mass-volume ratio of sepiolite fiber to hydrochloric acid is 1 g: 17 mL. Step S2: Mix hexamethylene diisocyanate, triethylenediamine, and toluene, stir evenly, and then add pretreated sepiolite fiber. Impregnate at 60°C for 3 hours. After impregnation, remove the fiber, wash and dry it to obtain modified sepiolite fiber. The reaction volume-mass ratio of pretreated sepiolite fiber, hexamethylene diisocyanate, and triethylenediamine is 9g:100mL:1g. Step S3: Under nitrogen atmosphere, carboxylated carbon nanotubes were added to N-methylpyrrolidone and ultrasonically dispersed for 15 min. Then, modified sepiolite fibers were added, and the reaction was continued at 60℃ for 2 h. After the reaction was completed, the fibers were removed and dried to obtain thermally conductive reinforced fibers. The mass ratio of carboxylated carbon nanotubes to modified sepiolite fibers was 1:3.5. Step 4: The preparation process of the amino-terminated flame retardant is as follows: 5-amino-tetrazazole is added to deionized water to obtain a 5-amino-tetrazazole solution; hexachlorocyclotriphosphazene and acetonitrile are mixed, stirred and dissolved, and then heated to 50℃. The 5-amino-tetrazazole solution is then added, stirred evenly, and sodium hydroxide is added. The mixture is refluxed for 5 hours. After the reaction is completed, the mixture is rotary evaporated, dried, dissolved, rotary evaporated again, and dried to obtain the amino-terminated flame retardant; the molar ratio of 5-amino-tetrazazole to hexachlorocyclotriphosphazene is 6.03:1. Step 5: Add the polyacrylic acid adhesive to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 1; add the amino-terminated flame retardant to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 2; mix reaction solution 1, reaction solution 2 and thermally conductive reinforcing fiber, and stir continuously for 1.5 hours to obtain the finished product; the mass ratio of polyacrylic acid adhesive, amino-terminated flame retardant and thermally conductive reinforcing fiber is 90:14.5:10.

[0022] Comparative Example 1: The propylene flame retardant monomer was removed, and the rest was the same as in Example 1. The specific steps are as follows: Step 1: Choline chloride and urea were added to deionized water and stirred at 85°C for 2.0 h to obtain a eutectic solvent; then acrylic acid and ethanolamine were added to the eutectic solvent, stirred evenly, and then photoinitiator 2959 was added. After stirring and dissolving, the mixture was crosslinked under ultraviolet light for 40 min to obtain a polyacrylic acid adhesive; the molar ratio of choline chloride and urea in the eutectic solvent was 2:1.05; the reaction mass ratio of acrylic acid and ethanolamine was 2.5:1; Step 2: The preparation process of thermally conductive reinforcing fibers is as follows: Step S1: Add sepiolite fiber to 1.1 mol / L hydrochloric acid and stir at 30℃ for 5 h. After stirring, filter, wash until neutral, dry and grind to obtain pretreated sepiolite fiber; the mass-volume ratio of sepiolite fiber to hydrochloric acid is 1 g: 17 mL. Step S2: Mix hexamethylene diisocyanate, triethylenediamine, and toluene, stir evenly, and then add pretreated sepiolite fiber. Impregnate at 70°C for 4 hours. After impregnation, remove the fiber, wash and dry it to obtain modified sepiolite fiber. The reaction volume-mass ratio of pretreated sepiolite fiber, hexamethylene diisocyanate, and triethylenediamine is 9g:100mL:1g. Step S3: Under nitrogen atmosphere, carboxylated carbon nanotubes were added to N-methylpyrrolidone and ultrasonically dispersed for 20 min. Then, modified sepiolite fibers were added, and the reaction was continued at 65℃ for 3 h. After the reaction was completed, the fibers were removed and dried to obtain thermally conductive reinforced fibers. The mass ratio of carboxylated carbon nanotubes to modified sepiolite fibers was 1:3.5. Step 3: The preparation process of the amino-terminated flame retardant is as follows: 5-amino-tetrazazole is added to deionized water to obtain a 5-amino-tetrazazole solution; hexachlorocyclotriphosphazene and acetonitrile are mixed, stirred and dissolved, and then heated to 55℃. The 5-amino-tetrazazole solution is then added, stirred evenly, and sodium hydroxide is added. The mixture is refluxed for 6 hours. After the reaction is completed, the mixture is rotary evaporated, dried, dissolved, rotary evaporated again, and dried to obtain the amino-terminated flame retardant. The molar ratio of 5-amino-tetrazazole to hexachlorocyclotriphosphazene is 6.03:1. Step 4: Add the polyacrylic acid adhesive to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 1; add the amino-terminated flame retardant to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 2; mix reaction solution 1, reaction solution 2 and thermally conductive reinforcing fiber, and stir continuously for 2.5 hours to obtain the finished product; the mass ratio of polyacrylic acid adhesive, amino-terminated flame retardant and thermally conductive reinforcing fiber is 90:14.5:10.

[0023] Comparative Example 2: The propylene flame retardant monomer and amino-terminated flame retardant were removed, and the rest was the same as in Example 1. The specific steps are as follows: Step 1: Choline chloride and urea were added to deionized water and stirred at 85°C for 2.0 h to obtain a eutectic solvent; then acrylic acid and ethanolamine were added to the eutectic solvent and stirred evenly. Then photoinitiator 2959 was added, stirred and dissolved, and crosslinked under ultraviolet light for 40 min to obtain a polyacrylic acid adhesive; the molar ratio of choline chloride and urea in the eutectic solvent was 2:1.05; the reaction mass ratio of acrylic acid and ethanolamine was 2.5:1; Step 2: The preparation process of thermally conductive reinforcing fibers is as follows: Step S1: Add sepiolite fiber to 1.1 mol / L hydrochloric acid and stir at 30℃ for 5 h. After stirring, filter, wash until neutral, dry and grind to obtain pretreated sepiolite fiber; the mass-volume ratio of sepiolite fiber to hydrochloric acid is 1 g: 17 mL. Step S2: Mix hexamethylene diisocyanate, triethylenediamine, and toluene, stir evenly, and then add pretreated sepiolite fiber. Impregnate at 70°C for 4 hours. After impregnation, remove the fiber, wash and dry it to obtain modified sepiolite fiber. The reaction volume-mass ratio of pretreated sepiolite fiber, hexamethylene diisocyanate, and triethylenediamine is 9g:100mL:1g. Step S3: Under nitrogen atmosphere, carboxylated carbon nanotubes were added to N-methylpyrrolidone and ultrasonically dispersed for 20 min. Then, modified sepiolite fibers were added, and the reaction was continued at 65℃ for 3 h. After the reaction was completed, the fibers were removed and dried to obtain thermally conductive reinforced fibers. The mass ratio of carboxylated carbon nanotubes to modified sepiolite fibers was 1:3.5. Step 3: Add the polyacrylic acid adhesive to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 1; mix reaction solution 1 and thermally conductive reinforcing fiber, and stir continuously for 2.5 hours to obtain the finished product; the mass ratio of polyacrylic acid adhesive to thermally conductive reinforcing fiber is 90:10.

[0024] Comparative Example 3: The thermally conductive reinforcing fiber was removed, and the rest was the same as in Example 1. The specific steps are as follows: Step 1: The preparation process of the propylene flame retardant monomer is as follows: Under nitrogen atmosphere, diethylphosphonic acid and glycidyl methacrylate are added to tetrahydrofuran and reacted continuously at 85°C for 15 hours. During the reaction, the polymerization inhibitor 4-methoxyphenol is added. After the reaction is completed, the propylene flame retardant monomer is obtained by rotary evaporation. The reaction molar ratio of diethylphosphonic acid and glycidyl methacrylate is 1.15:1. Step 2: Add choline chloride and urea to deionized water and stir at 85°C for 2.0 h to obtain a eutectic solvent; then add acrylic acid, propylene flame retardant monomer, and ethanolamine to the eutectic solvent, stir evenly, and then add photoinitiator 2959. After stirring to dissolve, crosslink under ultraviolet light for 40 min to obtain polyacrylic acid adhesive; the molar ratio of choline chloride and urea in the eutectic solvent is 2:1.05; the reaction mass ratio of acrylic acid, propylene flame retardant monomer, and ethanolamine is 2.5:1.4:1; Step 3: The preparation process of the amino-terminated flame retardant is as follows: 5-amino-tetrazazole is added to deionized water to obtain a 5-amino-tetrazazole solution; hexachlorocyclotriphosphazene and acetonitrile are mixed, stirred and dissolved, and then heated to 55℃. The 5-amino-tetrazazole solution is then added, stirred evenly, and sodium hydroxide is added. The mixture is refluxed for 6 hours. After the reaction is completed, the mixture is rotary evaporated, dried, dissolved, rotary evaporated again, and dried to obtain the amino-terminated flame retardant. The molar ratio of 5-amino-tetrazazole to hexachlorocyclotriphosphazene is 6.03:1. Step 4: Add the polyacrylic acid adhesive to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 1; add the amino-terminated flame retardant to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 2; mix reaction solution 1 and reaction solution 2, and stir continuously for 2.5 hours to obtain the finished product; the mass ratio of polyacrylic acid adhesive to amino-terminated flame retardant is 90:14.5.

[0025] Testing and experimentation: Flame retardant performance test: The finished adhesive prepared according to this invention was poured into a polytetrafluoroethylene mold and reacted at 120°C for 4 hours to obtain a sample. The oxygen index value of the sample was tested according to GB / T 2406.1-2008 "Determination of flammability of plastics by oxygen index method - Part 1: Guidelines".

[0026] Tensile property test: The finished adhesive prepared according to this invention was poured into a polytetrafluoroethylene mold and reacted at 120°C for 4 hours to obtain a sample. A tensile test was performed on the sample using an electronic universal testing machine. The sample size was 40mm × 8mm × 2mm, and the tensile properties of the sample were tested under the condition of a tensile rate of 2mm / min.

[0027] Thermal conductivity test: The finished adhesive prepared according to this invention was poured into a polytetrafluoroethylene mold and reacted at 120°C for 4 hours to obtain a sample. The thermal conductivity of the sample was tested according to ASTM D5470-06, "Standard Test Method for Thermal Conductivity and Electrical Insulation Materials". The results are shown in the table below:

[0028] Conclusion: In Examples 1-3, the dosage remained unchanged, with only some reaction parameters modified. Experimental data show that the various properties of the samples did not exhibit significant fluctuations.

[0029] Comparative Example 1: The propylene flame retardant monomer was removed, and the rest was the same as in Example 1. The experimental data showed that, compared with Example 1, the oxygen index decreased to 25.5% and the tensile strength decreased to 6.54 MPa. The reason for this is that the propylene flame retardant monomer itself has good flame retardancy and, by effectively participating in the crosslinking of polyacrylic acid adhesive, it has good tensile strength. Therefore, removing it reduces the oxygen index and tensile strength.

[0030] Comparative Example 2: The propylene flame retardant monomer and amino-terminated flame retardant were removed, while the rest were the same as in Example 1. The experimental data showed that, compared with Example 1, the oxygen index decreased to 22.4% and the tensile strength decreased to 5.81 MPa. The reason for this is that, based on Comparative Example 1, Comparative Example 2 further removed the amino-terminated flame retardant, which further reduced the degree of crosslinking of the finished adhesive and the flame retardancy, thus reducing the oxygen index and tensile strength.

[0031] Comparative Example 3: The thermally conductive reinforcing fiber was removed, and the rest was the same as in Example 1. The experimental data showed that, compared with Example 1, the tensile strength decreased to 6.21 MPa and the thermal conductivity decreased to 0.23 W / mK. The reason for this is that the surface of the thermally conductive reinforcing fiber has a carbon nanotube thermally conductive network, and the sepiolite fiber can effectively improve the tensile properties of the matrix. Therefore, removing it reduces the tensile strength and the thermal conductivity.

[0032] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process method article or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process method article or apparatus.

[0033] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a high thermal conductivity adhesive for solid-state batteries, characterized in that: Includes the following steps: Step 1: Add choline chloride and urea to deionized water and stir to obtain a eutectic solvent; then add acrylic acid, propylene flame retardant monomer and ethanolamine to the eutectic solvent, stir evenly and then add photoinitiator, stir to dissolve and crosslink under ultraviolet light to obtain polyacrylic acid adhesive. Step 2: Add polyacrylic acid adhesive to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 1; add amino-terminated flame retardant to N-methylpyrrolidone, stir and ultrasonically disperse to obtain reaction solution 2; mix reaction solution 1, reaction solution 2 and thermally conductive reinforcing fiber, and stir continuously to obtain the finished product.

2. The method for preparing a high thermal conductivity adhesive for solid-state batteries according to claim 1, characterized in that: Choline chloride and urea were added to deionized water and stirred at 80-85℃ for 1.5-2.0 h to obtain a eutectic solvent; the molar ratio of choline chloride and urea in the eutectic solvent was 2:(1.0-1.1); acrylic acid, propylene flame retardant monomer, and ethanolamine were added to the eutectic solvent, stirred evenly, and then photoinitiator 2959 was added. After stirring and dissolving, crosslinking was carried out under ultraviolet light for 30-40 min to obtain polyacrylic acid adhesive; the reaction mass ratio of acrylic acid, propylene flame retardant monomer, and ethanolamine was 2.5:(1.3-1.5):1; reaction solution 1, reaction solution 2, and thermally conductive reinforcing fiber were mixed and stirred continuously for 1.5-2.5 h to obtain the finished product; the reaction mass ratio of polyacrylic acid adhesive, amino-terminated flame retardant, and thermally conductive reinforcing fiber was 90:(14-15):(9-12).

3. The method for preparing a high thermal conductivity adhesive for solid-state batteries according to claim 1, characterized in that: The preparation process of thermally conductive reinforced fibers is as follows: Step S1: Add sepiolite fibers to 1.0-1.2 mol / L hydrochloric acid and stir at 25-30℃ for 4-5 hours. After stirring, filter, wash until neutral, dry, and grind to obtain pretreated sepiolite fibers. Step S2: Mix hexamethylene diisocyanate, triethylenediamine, and toluene, stir evenly, and then add pretreated sepiolite fiber. Impregnate at 60-70℃ for 3-4 hours. After impregnation, remove the fiber, wash and dry it to obtain modified sepiolite fiber. Step S3: Under nitrogen atmosphere, carboxylated carbon nanotubes are added to N-methylpyrrolidone and ultrasonically dispersed for 15-20 min. Then, modified sepiolite fibers are added and reacted at 60-65℃ for 2-3 h. After the reaction is completed, the fibers are removed and dried to obtain thermally conductive reinforced fibers.

4. The method for preparing a high thermal conductivity adhesive for solid-state batteries according to claim 3, characterized in that: In step S1, the mass-to-volume ratio of sepiolite fiber to hydrochloric acid is 1 g: (16-18) mL; in step S2, the mass-to-volume ratio of the reaction of pretreated sepiolite fiber, hexamethylene diisocyanate, and triethylenediamine is (8-10) g: 100 mL: 1 g; in step S3, the mass-to-volume ratio of the reaction of carboxylated carbon nanotubes and modified sepiolite fiber is 1: (3-4).

5. The method for preparing a high thermal conductivity adhesive for solid-state batteries according to claim 1, characterized in that: The preparation process of the propylene flame retardant monomer is as follows: Diethylphosphonic acid and glycidyl methacrylate are added to tetrahydrofuran under nitrogen atmosphere and reacted continuously at 80-85℃ for 10-15h. During the reaction, the polymerization inhibitor 4-methoxyphenol is added. After the reaction is completed, the propylene flame retardant monomer is obtained by rotary evaporation.

6. The method for preparing a high thermal conductivity adhesive for solid-state batteries according to claim 5, characterized in that: The reaction molar ratio of diethylphosphonic acid and glycidyl methacrylate is (1.1-1.2):

1.

7. The method for preparing a high thermal conductivity adhesive for solid-state batteries according to claim 1, characterized in that: The preparation process of the amino-terminated flame retardant is as follows: 5-amino-tetrazazole is added to deionized water to obtain a 5-amino-tetrazazole solution; hexachlorocyclotriphosphazene and acetonitrile are mixed, stirred and dissolved, and then heated to 50-55℃. The 5-amino-tetrazazole solution is then added, stirred evenly, and sodium hydroxide is added. The mixture is refluxed for 5-6 hours. After the reaction is completed, the mixture is rotary evaporated, dried, dissolved, rotary evaporated again, and dried to obtain the amino-terminated flame retardant.

8. The method for preparing a high thermal conductivity adhesive for solid-state batteries according to claim 7, characterized in that: The molar ratio of 5-amino-tetrazole to hexachlorocyclotriphosphazene is (6.00-6.05):

1.

9. A high thermal conductivity adhesive for solid-state batteries, characterized in that, Prepared by the preparation method according to any one of claims 1-8.

10. An application of a high thermal conductivity adhesive for solid-state batteries, characterized in that: The prepared high thermal conductivity binder, conductive agent, positive electrode material / negative electrode material are mixed to obtain a slurry; the slurry is coated onto the surface of the positive electrode current collector and the negative electrode current collector respectively to obtain positive electrode sheet and negative electrode sheet; the prepared positive electrode sheet and negative electrode sheet are pressed onto both sides of the solid electrolyte to assemble a solid lithium battery.

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