Preparation method and application of hydrated salt phase change microcapsule modified diaphragm

Abstract

The invention discloses a preparation method and application of a hydrated salt phase change microcapsule modified diaphragm, and relates to the technical field of battery diaphragms.The preparation method comprises the steps that hydrated salt phase change microcapsules and a binder are taken and added into a solvent, and stirring is conducted; carrying out ultrasonic dispersion, taking out and magnetically stirring to obtain hydrated salt phase change microcapsule slurry; putting the lithium ion battery diaphragm into an organic solvent, and dipping; taking out, washing with deionized water, and soaking in deionized water; putting into a plasma surface treatment instrument, and treating in an oxygen atmosphere; taking out, and dipping in a chitosan solution; taking out, and dipping in a vinyltriethoxysilane solution; taking out and drying in vacuum to obtain a plasma modified diaphragm; and coating the surface of the plasma modified diaphragm with the hydrated salt phase change microcapsule slurry, and performing vacuum drying to obtain the hydrated salt phase change microcapsule modified diaphragm.

Description

Technical Field

[0001] This invention relates to the field of battery separator technology, specifically a method for preparing a hydrated salt phase change microcapsule modified separator and its application. Background Technology

[0002] A lithium-ion battery is a rechargeable battery that operates based on the mechanism of lithium ions being inserted and extracted between the positive and negative electrodes. Its core components include a positive electrode, a negative electrode, an electrolyte, and a separator. The separator is located between the positive and negative electrodes to prevent the two electrodes from coming into contact and causing a short circuit. The electrolyte carrying lithium ions migrates between the positive and negative electrodes through the separator. The better the electrolyte affinity of the separator, the less resistance the electrolyte encounters when passing through the separator, which is more conducive to improving the migration rate of lithium ions and improving battery performance. Lithium-ion batteries are widely used in electronic devices, new energy vehicles, and energy storage infrastructure due to their high energy density and long service life. Polypropylene separators, which are commonly used in lithium-ion batteries, are highly stable and inexpensive. However, polypropylene separators have a low melting point and are prone to shrinkage and melting in high-temperature environments, leading to battery short circuits. Therefore, how to protect the battery, limit heat dissipation, and improve the battery's thermal performance is a problem that the market urgently needs to solve.

[0003] Chinese patent with publication number CN116814221B discloses a single-shell phase change microcapsule. However, traditional single-shell microcapsules rupture prematurely due to the high temperature environment and strong mechanical pressure during battery manufacturing, and it is difficult to balance their mechanical strength and thermal response sensitivity. Chinese patent CN106479445A discloses a method for preparing polyurea-polyacrylate double-shell microcapsules by a combination of interfacial polymerization and in-situ polymerization. However, organic phase change materials have low phase change enthalpy and absorb less heat during the phase change process, which cannot effectively suppress the rate of temperature rise of lithium-ion batteries during thermal runaway. Moreover, organic phase change materials are flammable, and ignition will further promote the spread of thermal runaway.

[0004] To address the aforementioned issues and improve the electrolyte affinity and thermal properties of lithium-ion battery separators, this invention provides a method for preparing a hydrated salt phase change microcapsule modified separator and its application. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a hydrated salt phase change microcapsule modified diaphragm and its application, so as to solve the problems raised in the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: Step 1: Add the hydrated salt phase change microcapsules and binder to the solvent and stir; disperse by ultrasonication, remove and stir magnetically to obtain the hydrated salt phase change microcapsule slurry; Step 2: Place the lithium-ion battery separator in an organic solvent and immerse it; remove it, wash it with deionized water, immerse it in deionized water, and then immerse it again; place it in a plasma surface treatment instrument and treat it under an oxygen atmosphere; remove it and immerse it in a chitosan solution; remove it and immerse it in a vinyltriethoxysilane solution; remove it and vacuum dry it to obtain the plasma-modified separator. Step 3: Coat the slurry of hydrated salt phase change microcapsules onto the surface of the plasma-modified membrane, and vacuum dry to obtain the hydrated salt phase change microcapsule modified membrane.

[0007] A more optimized hydrated salt phase change microcapsule slurry comprises the following components, expressed as mass percentages: 5-20 wt% hydrated salt phase change microcapsules, 4-20 wt% binder, and the balance being solvent.

[0008] A more optimized method for preparing hydrated salt phase change microcapsules is as follows: hydrated salt is added to hydrophilic modified boron nitride, heated, and sonicated to obtain a mixed solution; cyclohexane is added to hydrophilic modified boron nitride, sonicated, and then added to the mixed solution, maintaining a constant temperature and sonicating; hexadecyltrimethylammonium bromide is added, maintaining a constant temperature and stirring; 3-aminopropyltriethoxysilane and tetraethyl silicate are added, maintaining a constant temperature and stirring; ammonia is added, maintaining a constant temperature and stirring; the mixture is filtered, washed with anhydrous ethanol, and dried to obtain hydrated salt phase change microcapsules. The mass ratio of the hydrated salt, hydrophilic modified boron nitride, cyclohexane, hexadecyltrimethylammonium bromide, 3-aminopropyltriethoxysilane, tetraethyl silicate, and ammonia is (5-43):(0.7-1):(25-40):(0.1-2):(1-5):(6-35):(7-60).

[0009] A more optimized ammonia concentration is 20%-30%.

[0010] A more optimized chitosan solution concentration is 0.5-2.5 wt%. The concentration of the vinyltriethoxysilane solution is 0.1-3 wt%.

[0011] In a more optimized step, the conditions for ultrasonic dispersion in step one are: ultrasonic dispersion for 20-30 minutes at an ultrasonic frequency of 39-41KHz and an ultrasonic power of 440-460W. In step one, the conditions for magnetic stirring are: stirring magnetically for 2.5-4 hours at a speed of 500-800 rpm.

[0012] The optimal mass ratio of hydrated salt phase change microcapsules to plasma-modified membranes is 1:(4-20).

[0013] More preferably, the adhesive is any one or more of polyvinylidene fluoride and sodium carboxymethyl cellulose; The solvent is any one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; The lithium-ion battery separator is any one of polyethylene separator, polypropylene separator, or polypropylene / polyethylene / polypropylene composite separator; The organic solvent is any one of ethanol solution, isopropanol, and acetone.

[0014] Ideally, the concentration of the ethanol solution is 70%-80%.

[0015] The more optimized hydrophilic modified boron nitride is any one of hydroxylated hexagonal boron nitride nanosheets, aminolated hexagonal boron nitride nanosheets, and carboxylated hexagonal boron nitride nanosheets; The method for preparing the hydrophilic modified boron nitride includes the following steps: Option 1: Add hexagonal boron nitride powder to sucrose, place it in a ball mill jar, and ball mill; wash with deionized water, sonicate, centrifuge, and obtain supernatant; take the supernatant, centrifuge, and obtain supernatant; take the supernatant, freeze dry, and obtain hydrophilic modified boron nitride; Option 2: Add hexagonal boron nitride powder to dopamine, add deionized water, mix evenly to obtain a slurry; take the slurry, sonicate, add agate balls, and liquid-phase ball mill to obtain hydrophilic modified boron nitride; Option 3: Add dopamine to Tris-HCl buffer and mix well to obtain a dopamine-Tris mixed solution; impregnate hexagonal boron nitride powder in the dopamine-Tris mixed solution, shake, wash with deionized water, and dry to obtain hydrophilic modified boron nitride. Option 4: Take hexagonal boron nitride powder, add it to tannic acid, add deionized water, mix evenly to obtain a slurry; take the slurry, sonicate it, add agate balls, and liquid-phase ball mill it to obtain hydrophilic modified boron nitride.

[0016] More optimized, the hydrated salt is any one or more of sodium thiosulfate pentahydrate, sodium acetate trihydrate, disodium hydrogen phosphate dodecahydrate, sodium sulfate decahydrate, calcium chloride hexahydrate, and strontium chloride hexahydrate.

[0017] A more optimized hydrated salt phase change microcapsule modified diaphragm was prepared.

[0018] The optimized application of the hydrated salt phase change microcapsule modified separator in the field of lithium-ion batteries.

[0019] Compared with the prior art, the beneficial effects of the present invention are: This invention uses a hydrated salt phase change microcapsule slurry coated on the surface of a plasma-modified separator. Hydroxylated, aminated, and carboxylated boron nitride hexahydrate (i.e., hydrophilic modified boron nitride) is prepared using a physical-chemical modifier composite modification method. The hydrated salt phase change microcapsules use hydrated salt as the core material and hydrophilic modified boron nitride and silicon dioxide as the shell layer. When the local temperature of the battery reaches the solid-liquid phase change temperature and thermochemical decomposition temperature of the hydrated salt, the hydrated salt absorbs heat and melts and decomposes thermochemically, inhibiting heat diffusion and improving the thermal safety of the battery. However, using hydrated salt directly can lead to the loss of crystal water during endothermic melting, and free ions can corrode the battery electrodes, affecting battery life. By using a core-shell structure to confine the hydrated salt in the core-shell structure silica-hydrated salt nanospace, the hydrated salt can undergo endothermic melting and thermochemical decomposition in the internal space, preventing battery thermal runaway and improving battery safety and lifespan.

[0020] Polypropylene separators are surface-treated with oxygen plasma and then sequentially immersed in chitosan solution and vinyltriethoxysilane solution to obtain plasma-modified separators. Oxygen plasma surface treatment of the polypropylene separator introduces oxygen-containing polar groups onto the separator surface, reducing the water contact angle and significantly improving the separator's hydrophilicity and surface energy, thereby increasing the electrolyte's wetting rate and improving battery performance. Furthermore, the oxygen-containing groups introduced onto the plasma-activated separator surface form hydrogen bonds with the hydroxyl groups of chitosan, allowing the chitosan solution to spread evenly on the separator surface, improving its dispersibility and inhibiting micropore blockage. The hydrophilic groups of chitosan form a hydration layer with water molecules, reducing the transport resistance of lithium ions in the electrolyte, increasing the migration rate of lithium ions, and improving battery performance.

[0021] Impregnating with vinyltriethoxysilane has two main effects. First, vinyltriethoxysilane hydrolyzes to generate hydroxyl groups, which then form covalent bonds with the oxygen-containing groups on the membrane surface and the hydroxyl groups of chitosan through a condensation reaction. This acts as a bridge, increasing the bonding force between the membrane and chitosan and preventing the chitosan layer from detaching and causing blockage of the membrane micropores. Second, vinyl groups construct a hydrophobic network within the membrane micropores, reducing the binding rate between chitosan and water molecules, preventing chitosan swelling, and avoiding the chitosan layer from detaching and causing blockage of the membrane micropores.

[0022] The preparation method of the present invention is simple and quick, requiring only modification of existing lithium-ion battery separators and coating with self-made hydrated salt phase change microcapsule slurry; there is no need to develop or produce new separators, which helps to save production costs. Attached Figure Description

[0023] Figure 1 This is a scanning electron microscope (SEM) image of a cross-section of the hydrated salt phase change microcapsule modified diaphragm prepared in Example 1 of this invention. Figure 2This is a photograph of the hydrated salt phase change microcapsule modified diaphragm prepared in Example 1 of the present invention. Figure 3 This is a photograph of the polypropylene diaphragm of the present invention. Figure 4 The image shows the contact angle test results of the hydrated salt phase change microcapsule modified diaphragm prepared in Example 1 of this invention. Figure 5 This is a test diagram of the contact angle of the polypropylene diaphragm of the present invention; Figure 6 Differential scanning calorimetry curves of the hydrated salt phase change microcapsule modified diaphragm prepared in Examples 1-4 of this invention; Figure 7 The graphs show the cycle performance of lithium iron phosphate batteries prepared in Examples 1, 2 and Comparative Example 1 of this invention. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0025] The sources and types of substances involved in this invention are not particularly limited, and exemplary examples include: The following products were supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.: hexagonal boron nitride (Catalog No. B106033); sucrose (Catalog No. S112224-500g); sodium thiosulfate pentahydrate (Catalog No. S431244-2.5kg); hexadecyltrimethylammonium bromide (Catalog No. 761534566321); 3-aminopropyltriethoxysilane (Catalog No. A800523); tetraethyl silicate (Catalog No. A800523). Product code T819506, supplied by Shanghai Maclean Biochemical Co., Ltd.; 25% ammonia solution, product code A639162-2.5L, supplied by Shanghai Aladdin Biochemical Technology Co., Ltd.; anhydrous ethanol, CAS number 64-17-5, supplied by Tianjin Baishi Chemical Co., Ltd.; polyvinylidene fluoride, product code PVDF761, supplied by Zhongxin Plastics Co., Ltd.; sodium carboxymethyl cellulose, product code C804626, supplied by Shanghai Maclean Biochemical Co., Ltd.; methylpyrrolidone, product code M812728, supplied by Shanghai Maclean Biochemical Co., Ltd.; Celgard The following materials were supplied: 2400 series polypropylene (PP) diaphragms (C105803-1kg) from Celgard Corporation, USA; chitosan (C105803-1kg) from Shanghai Aladdin Biochemical Technology Co., Ltd.; vinyltriethoxysilane (T103647-500ml) from Shanghai Aladdin Biochemical Technology Co., Ltd.; graphite (G434783-100g) from Shanghai Aladdin Biochemical Technology Co., Ltd.; lithium iron phosphate (L856672-100g) from Shanghai Maclean Biochemical Technology Co., Ltd.; ethylene carbonate (MJS-EC-2024101023-100g) from Nanjing Mojies Energy Technology Co., Ltd.; and lithium hexafluorophosphate (DW-012-100g) from Shanghai Daolian Reagent Co., Ltd. The following products are supplied: Fluoroethylene carbonate (F120339-100g) from Shanghai Aladdin Biochemical Technology Co., Ltd.; Dopamine (A902400) from Shanghai Maclean Biochemical Co., Ltd.; Tannic acid (T818845) from Shanghai Maclean Biochemical Co., Ltd.; LB-083 secondary electrolyte (E245.50.015) from Duoduo Chemical Technology Co., Ltd.; Cyclohexane (C100585-500ml) from Shanghai Aladdin Biochemical Technology Co., Ltd.; 100ml container of agate balls (XD0103) from Liaoning Heishan Xinde Agate Products Factory; and Tris-HCl buffer (R28525-500ml) from Shanghai Maclean Biochemical Technology Co., Ltd. Example 1: A method for preparing a hydrated salt phase change microcapsule modified diaphragm; Step 1: Preparation of hydrophilic modified boron nitride Hexagonal boron nitride powder with a particle size of 20 μm was added to sucrose at a mass ratio of 1:5 and placed in a ball mill jar for 11 h. The mixture was washed with deionized water, sonicated for 1.5 h, and centrifuged at 3000 rpm for 22 min to obtain a supernatant. The supernatant was then centrifuged at 7500 rpm for 8 min to obtain another supernatant. The supernatant was then freeze-dried to obtain hydrophilic modified boron nitride. Step 2: Preparation of hydrated salt phase change microcapsules 43g of sodium thiosulfate pentahydrate was added to 0.3g of hydrophilic modified boron nitride, heated, and sonicated to obtain a mixed solution; 39g of cyclohexane was added to 0.4g of hydrophilic modified boron nitride, sonicated, and then added to the mixed solution, maintaining a constant temperature and sonicating; 0.3g of hexadecyltrimethylammonium bromide was added, maintaining a constant temperature and stirring; 2g of 3-aminopropyltriethoxysilane and 6g of tetraethyl silicate were added, maintaining a constant temperature and stirring; 9g of 25% ammonia water was added, maintaining a constant temperature and stirring; the mixture was filtered, washed with anhydrous ethanol, and dried to obtain hydrated salt phase change microcapsules; Step 3: Preparation of hydrated salt phase change microcapsule slurry Take 20g of hydrated salt phase change microcapsules, 5g of polyvinylidene fluoride powder, and 5g of sodium carboxymethyl cellulose and add them to 70g of N-methylpyrrolidone. Place the mixture on a magnetic stirrer and stir for 15min at 650rpm. Then, ultrasonically disperse the mixture for 25min at an ultrasonic frequency of 40kHz and an ultrasonic power of 450W. Remove the mixture and place it on a magnetic stirrer. Stir the mixture magnetically for 3.25h at 650rpm to obtain the hydrated salt phase change microcapsule slurry. Step 4: Preparation of plasma-modified membrane A polypropylene diaphragm was immersed in a 75% ethanol solution for 30 min; it was then removed, washed with deionized water, and immersed in deionized water for 10 min; it was then placed in a plasma surface treatment instrument under an oxygen atmosphere, with a controlled pressure of 25 Pa and a power of 60 W, for 10 s; it was then removed and immersed in a 1.5 wt% chitosan solution for 2 min; it was then removed and immersed in a 1.55 wt% vinyltriethoxysilane solution for 10 s; it was then removed and vacuum dried at 40 °C to obtain the plasma-modified diaphragm. Step 5: Preparation of hydrated salt phase change microcapsule modified diaphragm Under the conditions of a coating rate of 0.05 m / s and a coating thickness of 15 μm, the slurry of hydrated salt phase change microcapsules was coated on the surface of a plasma-modified membrane and dried under vacuum for 4.5 h at a temperature of 40 °C to obtain a hydrated salt phase change microcapsule modified membrane. Step Six: Fabrication of Lithium Iron Phosphate Batteries A lithium iron phosphate battery was obtained by using a hydrated salt phase change microcapsule modified separator as the battery separator, graphite as the negative electrode, lithium iron phosphate as the positive electrode, ethylene carbonate and lithium hexafluorophosphate as the electrolyte, and fluoroethylene carbonate as the additive.

[0026] Example 2: A method for preparing a hydrated salt phase change microcapsule modified diaphragm; Step 1: Preparation of hydrophilic modified boron nitride Hexagonal boron nitride powder with a particle size of 20 μm was added to dopamine at a mass ratio of 1:4, and deionized water was added. The mixture was stirred evenly to obtain a slurry. The slurry was ultrasonicated for 1.5 h, and agate balls were added. The mass ratio of agate balls to hexagonal boron nitride powder was 60:1. The mixture was then ball-milled in liquid phase at a temperature of 25 °C for 17.5 h to obtain hydrophilic modified boron nitride. Step 2: Preparation of hydrated salt phase change microcapsules 41g of sodium thiosulfate pentahydrate was added to 0.3g of hydrophilic modified boron nitride, heated, and sonicated to obtain a mixed solution; 37g of cyclohexane was added to 0.4g of hydrophilic modified boron nitride, sonicated, and then added to the mixed solution, maintaining a constant temperature and sonicating; 0.3g of hexadecyltrimethylammonium bromide was added, maintaining a constant temperature and stirring; 1g of 3-aminopropyltriethoxysilane and 6g of tetraethyl silicate were added, maintaining a constant temperature and stirring; 14g of 25% ammonia water was added, maintaining a constant temperature and stirring; the mixture was filtered, washed with anhydrous ethanol, and dried to obtain hydrated salt phase change microcapsules; Step 3: Preparation of hydrated salt phase change microcapsule slurry Take 15g of hydrated salt phase change microcapsules, 5g of polyvinylidene fluoride powder, and 5g of sodium carboxymethyl cellulose and add them to 75g of N-methylpyrrolidone. Place the mixture on a magnetic stirrer and stir for 15min at 650rpm. Then, ultrasonically disperse the mixture for 25min at an ultrasonic frequency of 40kHz and an ultrasonic power of 450W. Remove the mixture and place it on a magnetic stirrer. Stir the mixture magnetically for 3.25h at 650rpm to obtain the hydrated salt phase change microcapsule slurry. Step 4: Preparation of plasma-modified membrane A polypropylene diaphragm was immersed in a 75% ethanol solution for 30 min; it was then removed, washed with deionized water, and immersed in deionized water for 10 min; it was then placed in a plasma surface treatment instrument under an oxygen atmosphere, with a controlled pressure of 25 Pa and a power of 60 W, for 10 s; it was then removed and immersed in a 1.5 wt% chitosan solution for 2 min; it was then removed and immersed in a 1.55 wt% vinyltriethoxysilane solution for 10 s; it was then removed and vacuum dried at 40 °C to obtain the plasma-modified diaphragm. Step 5: Preparation of hydrated salt phase change microcapsule modified diaphragm Under the conditions of a coating rate of 0.05 m / s and a coating thickness of 15 μm, the slurry of hydrated salt phase change microcapsules was coated on the surface of a plasma-modified membrane and dried under vacuum for 4.5 h at a temperature of 40 °C to obtain a hydrated salt phase change microcapsule modified membrane. Step Six: Fabrication of Lithium Iron Phosphate Batteries A lithium iron phosphate battery was obtained by using a hydrated salt phase change microcapsule modified separator as the battery separator, graphite as the negative electrode, lithium iron phosphate as the positive electrode, ethylene carbonate and lithium hexafluorophosphate as the electrolyte, and fluoroethylene carbonate as the additive.

[0027] Example 3: A method for preparing a hydrated salt phase change microcapsule modified diaphragm; Step 1: Preparation of hydrophilic modified boron nitride 2 mg of dopamine was added to 1 mL of pH 8.5 Tris-HCl buffer and mixed thoroughly to obtain a dopamine-Tris mixed solution. 20 μm hexagonal boron nitride powder was impregnated in the dopamine-Tris mixed solution, shaken for 12 h at 20 °C, washed with deionized water, and dried to obtain hydrophilic modified boron nitride. Step 2: Preparation of hydrated salt phase change microcapsules 43g of sodium thiosulfate pentahydrate was added to 0.3g of hydrophilic modified boron nitride, heated, and sonicated to obtain a mixed solution; 39g of cyclohexane was added to 0.4g of hydrophilic modified boron nitride, sonicated, and then added to the mixed solution, maintaining a constant temperature and sonicating; 0.3g of hexadecyltrimethylammonium bromide was added, maintaining a constant temperature and stirring; 1g of 3-aminopropyltriethoxysilane and 9g of tetraethyl silicate were added, maintaining a constant temperature and stirring; 7g of 25% ammonia water was added, maintaining a constant temperature and stirring; the mixture was filtered, washed with anhydrous ethanol, and dried to obtain hydrated salt phase change microcapsules; Step 3: Preparation of hydrated salt phase change microcapsule slurry Take 10g of hydrated salt phase change microcapsules, 5g of polyvinylidene fluoride powder, and 5g of sodium carboxymethyl cellulose and add them to 80g of N-methylpyrrolidone. Place the mixture on a magnetic stirrer and stir for 15min at 650rpm. Then, ultrasonically disperse the mixture for 25min at an ultrasonic frequency of 40kHz and an ultrasonic power of 450W. Remove the mixture and place it on a magnetic stirrer. Stir the mixture magnetically for 3.25h at 650rpm to obtain the hydrated salt phase change microcapsule slurry. Step 4: Preparation of plasma-modified membrane A polypropylene diaphragm was immersed in a 75% ethanol solution for 30 min; it was then removed, washed with deionized water, and immersed in deionized water for 10 min; it was then placed in a plasma surface treatment instrument under an oxygen atmosphere, with a controlled pressure of 25 Pa and a power of 60 W, for 10 s; it was then removed and immersed in a 1.5 wt% chitosan solution for 2 min; it was then removed and immersed in a 1.55 wt% vinyltriethoxysilane solution for 10 s; it was then removed and vacuum dried at 40 °C to obtain the plasma-modified diaphragm. Step 5: Preparation of hydrated salt phase change microcapsule modified diaphragm Under the conditions of a coating rate of 0.05 m / s and a coating thickness of 15 μm, the slurry of hydrated salt phase change microcapsules was coated on the surface of a plasma-modified membrane and dried under vacuum for 4.5 h at a temperature of 40 °C to obtain a hydrated salt phase change microcapsule modified membrane. Step Six: Fabrication of Lithium Iron Phosphate Batteries A lithium iron phosphate battery was obtained by using a hydrated salt phase change microcapsule modified separator as the battery separator, graphite as the negative electrode, lithium iron phosphate as the positive electrode, ethylene carbonate and lithium hexafluorophosphate as the electrolyte, and fluoroethylene carbonate as the additive.

[0028] Example 4: A method for preparing a hydrated salt phase change microcapsule modified diaphragm; Step 1: Preparation of hydrophilic modified boron nitride Hexagonal boron nitride powder with a particle size of 20 μm was added to tannic acid at a mass ratio of 3:1, followed by deionized water. The mixture was stirred until homogeneous to obtain a slurry. The slurry was ultrasonicated for 1.5 h, and agate balls were added. The mass ratio of agate balls to hexagonal boron nitride powder was 60:1. The mixture was then liquid-phase ball-milled for 19.5 h at a temperature of 25 °C to obtain hydrophilic modified boron nitride. Step 2: Preparation of hydrated salt phase change microcapsules 40g of sodium thiosulfate pentahydrate was added to 0.3g of hydrophilic modified boron nitride, heated, and sonicated to obtain a mixed solution; 36g of cyclohexane was added to 0.4g of hydrophilic modified boron nitride, sonicated, and then added to the mixed solution, maintaining a constant temperature and sonicating; 0.3g of hexadecyltrimethylammonium bromide was added, maintaining a constant temperature and stirring; 1g of 3-aminopropyltriethoxysilane and 9g of tetraethyl silicate were added, maintaining a constant temperature and stirring; 13g of 25% ammonia water was added, maintaining a constant temperature and stirring; the mixture was filtered, washed with anhydrous ethanol, and dried to obtain hydrated salt phase change microcapsules; Step 3: Preparation of hydrated salt phase change microcapsule slurry Take 5g of hydrated salt phase change microcapsules, 5g of polyvinylidene fluoride powder, and 5g of sodium carboxymethyl cellulose and add them to 85g of N-methylpyrrolidone. Place the mixture on a magnetic stirrer and stir for 15min at 650rpm. Then, ultrasonically disperse the mixture for 25min at an ultrasonic frequency of 40kHz and an ultrasonic power of 450W. Remove the mixture and place it on a magnetic stirrer. Stir the mixture magnetically for 3.25h at 650rpm to obtain the hydrated salt phase change microcapsule slurry. Step 4: Preparation of plasma-modified membrane A polypropylene diaphragm was immersed in a 75% ethanol solution for 30 min; it was then removed, washed with deionized water, and immersed in deionized water for 10 min; it was then placed in a plasma surface treatment instrument under an oxygen atmosphere, with a controlled pressure of 25 Pa and a power of 60 W, for 10 s; it was then removed and immersed in a 1.5 wt% chitosan solution for 2 min; it was then removed and immersed in a 1.55 wt% vinyltriethoxysilane solution for 10 s; it was then removed and vacuum dried at 40 °C to obtain the plasma-modified diaphragm. Step 5: Preparation of hydrated salt phase change microcapsule modified diaphragm Under the conditions of a coating rate of 0.05 m / s and a coating thickness of 15 μm, the slurry of hydrated salt phase change microcapsules was coated on the surface of a plasma-modified membrane and dried under vacuum for 4.5 h at a temperature of 40 °C to obtain a hydrated salt phase change microcapsule modified membrane. Step Six: Fabrication of Lithium Iron Phosphate Batteries A lithium iron phosphate battery was obtained by using a hydrated salt phase change microcapsule modified separator as the battery separator, graphite as the negative electrode, lithium iron phosphate as the positive electrode, ethylene carbonate and lithium hexafluorophosphate as the electrolyte, and fluoroethylene carbonate as the additive.

[0029] Comparative Example 1: The battery separator is a polypropylene separator, and the rest are the same as in Example 1; A lithium iron phosphate battery is obtained by assembling polypropylene membrane as the battery separator, graphite as the negative electrode, lithium iron phosphate as the positive electrode, ethylene carbonate and lithium hexafluorophosphate as the electrolyte, and fluoroethylene carbonate as the additive.

[0030] Comparative Example 2: The chitosan solution and vinyltriethoxysilane solution were not impregnated; the rest were the same as in Example 1. Step 1: Preparation of hydrophilic modified boron nitride Hexagonal boron nitride powder with a particle size of 20 μm was added to sucrose at a mass ratio of 1:5 and placed in a ball mill jar for 11 h. The mixture was washed with deionized water, sonicated for 1.5 h, and centrifuged at 3000 rpm for 22 min to obtain a supernatant. The supernatant was then centrifuged at 7500 rpm for 8 min to obtain another supernatant. The supernatant was then freeze-dried to obtain hydrophilic modified boron nitride. Step 2: Preparation of hydrated salt phase change microcapsules 43g of sodium thiosulfate pentahydrate was added to 0.3g of hydrophilic modified boron nitride, heated, and sonicated to obtain a mixed solution; 39g of cyclohexane was added to 0.4g of hydrophilic modified boron nitride, sonicated, and then added to the mixed solution, maintaining a constant temperature and sonicating; 0.3g of hexadecyltrimethylammonium bromide was added, maintaining a constant temperature and stirring; 2g of 3-aminopropyltriethoxysilane and 6g of tetraethyl silicate were added, maintaining a constant temperature and stirring; 9g of 25% ammonia water was added, maintaining a constant temperature and stirring; the mixture was filtered, washed with anhydrous ethanol, and dried to obtain hydrated salt phase change microcapsules; Step 3: Preparation of hydrated salt phase change microcapsule slurry Take 20g of hydrated salt phase change microcapsules, 5g of polyvinylidene fluoride powder, and 5g of sodium carboxymethyl cellulose and add them to 70g of N-methylpyrrolidone. Place the mixture on a magnetic stirrer and stir for 15min at 650rpm. Then, ultrasonically disperse the mixture for 25min at an ultrasonic frequency of 40kHz and an ultrasonic power of 450W. Remove the mixture and place it on a magnetic stirrer. Stir the mixture magnetically for 3.25h at 650rpm to obtain the hydrated salt phase change microcapsule slurry. Step 4: Preparation of plasma-modified membrane A polypropylene diaphragm was immersed in a 75% ethanol solution for 30 min; it was then removed, washed with deionized water, and immersed in deionized water for 10 min; it was then placed in a plasma surface treatment instrument under an oxygen atmosphere, with a controlled pressure of 25 Pa and a power of 60 W, for 10 s; it was then removed and immersed in a 1.5 wt% chitosan solution for 2 min; it was then removed and immersed in a 1.55 wt% vinyltriethoxysilane solution for 10 s; it was then removed and vacuum dried at 40 °C to obtain the plasma-modified diaphragm. Step 5: Preparation of hydrated salt phase change microcapsule modified diaphragm Under the conditions of a coating rate of 0.05 m / s and a coating thickness of 15 μm, the slurry of hydrated salt phase change microcapsules was coated on the surface of a plasma-modified membrane and dried under vacuum for 4.5 h at a temperature of 40 °C to obtain a hydrated salt phase change microcapsule modified membrane. Step Six: Fabrication of Lithium Iron Phosphate Batteries A lithium iron phosphate battery was obtained by using a hydrated salt phase change microcapsule modified separator as the battery separator, graphite as the negative electrode, lithium iron phosphate as the positive electrode, ethylene carbonate and lithium hexafluorophosphate as the electrolyte, and fluoroethylene carbonate as the additive.

[0031] Comparative Example 3: No vinyltriethoxysilane solution was impregnated; all other aspects are the same as in Example 1. Step 1: Preparation of hydrophilic modified boron nitride Hexagonal boron nitride powder with a particle size of 20 μm was added to sucrose at a mass ratio of 1:5 and placed in a ball mill jar for 11 h. The mixture was washed with deionized water, sonicated for 1.5 h, and centrifuged at 3000 rpm for 22 min to obtain a supernatant. The supernatant was then centrifuged at 7500 rpm for 8 min to obtain another supernatant. The supernatant was then freeze-dried to obtain hydrophilic modified boron nitride. Step 2: Preparation of hydrated salt phase change microcapsules 43g of sodium thiosulfate pentahydrate was added to 0.3g of hydrophilic modified boron nitride, heated, and sonicated to obtain a mixed solution; 39g of cyclohexane was added to 0.4g of hydrophilic modified boron nitride, sonicated, and then added to the mixed solution, maintaining a constant temperature and sonicating; 0.3g of hexadecyltrimethylammonium bromide was added, maintaining a constant temperature and stirring; 2g of 3-aminopropyltriethoxysilane and 6g of tetraethyl silicate were added, maintaining a constant temperature and stirring; 9g of 25% ammonia water was added, maintaining a constant temperature and stirring; the mixture was filtered, washed with anhydrous ethanol, and dried to obtain hydrated salt phase change microcapsules; Step 3: Preparation of hydrated salt phase change microcapsule slurry Take 20g of hydrated salt phase change microcapsules, 5g of polyvinylidene fluoride powder, and 5g of sodium carboxymethyl cellulose and add them to 70g of N-methylpyrrolidone. Place the mixture on a magnetic stirrer and stir for 15min at 650rpm. Then, ultrasonically disperse the mixture for 25min at an ultrasonic frequency of 40kHz and an ultrasonic power of 450W. Remove the mixture and place it on a magnetic stirrer. Stir the mixture magnetically for 3.25h at 650rpm to obtain the hydrated salt phase change microcapsule slurry. Step 4: Preparation of plasma-modified membrane The polypropylene membrane was immersed in 75% ethanol solution for 30 min; it was then removed, washed with deionized water, and immersed in deionized water for 10 min; it was then placed in a plasma surface treatment instrument and treated for 10 s under an oxygen atmosphere with a controlled pressure of 25 Pa and a power of 60 W; it was then removed and immersed in 1.5 wt% chitosan solution for 2 min; the membrane was then removed to obtain the plasma-modified membrane. Step 5: Preparation of hydrated salt phase change microcapsule modified diaphragm Under the conditions of a coating rate of 0.05 m / s and a coating thickness of 15 μm, the slurry of hydrated salt phase change microcapsules was coated on the surface of a plasma-modified membrane and dried under vacuum for 4.5 h at a temperature of 40 °C to obtain a hydrated salt phase change microcapsule modified membrane. Step Six: Fabrication of Lithium Iron Phosphate Batteries A lithium iron phosphate battery was obtained by using a hydrated salt phase change microcapsule modified separator as the battery separator, graphite as the negative electrode, lithium iron phosphate as the positive electrode, ethylene carbonate and lithium hexafluorophosphate as the electrolyte, and fluoroethylene carbonate as the additive.

[0032] Comparative Example 4: No chitosan solution was impregnated; all other aspects are the same as in Example 1. Step 1: Preparation of hydrophilic modified boron nitride Hexagonal boron nitride powder with a particle size of 20 μm was added to sucrose at a mass ratio of 1:5 and placed in a ball mill jar for 11 h. The mixture was washed with deionized water, sonicated for 1.5 h, and centrifuged at 3000 rpm for 22 min to obtain a supernatant. The supernatant was then centrifuged at 7500 rpm for 8 min to obtain another supernatant. The supernatant was then freeze-dried to obtain hydrophilic modified boron nitride. Step 2: Preparation of hydrated salt phase change microcapsules 43g of sodium thiosulfate pentahydrate was added to 0.3g of hydrophilic modified boron nitride, heated, and sonicated to obtain a mixed solution; 39g of cyclohexane was added to 0.4g of hydrophilic modified boron nitride, sonicated, and then added to the mixed solution, maintaining a constant temperature and sonicating; 0.3g of hexadecyltrimethylammonium bromide was added, maintaining a constant temperature and stirring; 2g of 3-aminopropyltriethoxysilane and 6g of tetraethyl silicate were added, maintaining a constant temperature and stirring; 9g of 25% ammonia water was added, maintaining a constant temperature and stirring; the mixture was filtered, washed with anhydrous ethanol, and dried to obtain hydrated salt phase change microcapsules; Step 3: Preparation of hydrated salt phase change microcapsule slurry Take 20g of hydrated salt phase change microcapsules, 5g of polyvinylidene fluoride powder, and 5g of sodium carboxymethyl cellulose and add them to 70g of N-methylpyrrolidone. Place the mixture on a magnetic stirrer and stir for 15min at 650rpm. Then, ultrasonically disperse the mixture for 25min at an ultrasonic frequency of 40kHz and an ultrasonic power of 450W. Remove the mixture and place it on a magnetic stirrer. Stir the mixture magnetically for 3.25h at 650rpm to obtain the hydrated salt phase change microcapsule slurry. Step 4: Preparation of plasma-modified membrane A polypropylene diaphragm was immersed in a 75% ethanol solution for 30 minutes; it was then removed, washed with deionized water, and immersed in deionized water for 10 minutes; it was then placed in a plasma surface treatment instrument under an oxygen atmosphere, with a controlled pressure of 25 Pa and a power of 60 W, for 10 seconds; it was then removed and immersed in a 1.55 wt% vinyltriethoxysilane solution for 10 seconds; it was then removed and vacuum dried at a temperature of 40 °C to obtain a plasma-modified diaphragm. Step 5: Preparation of hydrated salt phase change microcapsule modified diaphragm Under the conditions of a coating rate of 0.05 m / s and a coating thickness of 15 μm, the slurry of hydrated salt phase change microcapsules was coated on the surface of a plasma-modified membrane and dried under vacuum for 4.5 h at a temperature of 40 °C to obtain a hydrated salt phase change microcapsule modified membrane. Step Six: Fabrication of Lithium Iron Phosphate Batteries A lithium iron phosphate battery was obtained by using a hydrated salt phase change microcapsule modified separator as the battery separator, graphite as the negative electrode, lithium iron phosphate as the positive electrode, ethylene carbonate and lithium hexafluorophosphate as the electrolyte, and fluoroethylene carbonate as the additive.

[0033] Comparative Example 5: Uncoated hydrated salt phase change microcapsule slurry, otherwise refer to Example 1; Step 1: Preparation of plasma-modified membrane A polypropylene diaphragm was immersed in a 75% ethanol solution for 30 min; it was then removed, washed with deionized water, and immersed in deionized water for 10 min; it was then placed in a plasma surface treatment instrument under an oxygen atmosphere, with a controlled pressure of 25 Pa and a power of 60 W, for 10 s; it was then removed and immersed in a 1.5 wt% chitosan solution for 2 min; it was then removed and immersed in a 1.55 wt% vinyltriethoxysilane solution for 10 s; it was then removed and vacuum dried at 40 °C to obtain the plasma-modified diaphragm. Step 2: Preparation of Lithium Iron Phosphate Batteries A lithium iron phosphate battery was obtained by assembling a plasma-modified separator as the battery separator, graphite as the negative electrode, lithium iron phosphate as the positive electrode, ethylene carbonate and lithium hexafluorophosphate as the electrolyte, and fluoroethylene carbonate as the additive.

[0034] experiment The performance of the hydrated salt phase change microcapsule modified separators and lithium iron phosphate batteries prepared in Examples 1-4 and Comparative Examples 1-5 was measured. (1) Charge and discharge performance measurement The initial discharge specific capacity of the lithium iron phosphate battery was determined by 0.2 C cycle performance testing. After five cycles, the coulombic rate and average capacity decay rate were measured. (2) Thermal performance determination The temperature was heated to 120°C using a heating plate, and the specific temperature was recorded using a Fluke TiS20+MAX infrared thermal imager. The thermal shrinkage rate of the hydrated salt phase change microcapsule modified diaphragm was then determined. The phase transition enthalpy and decomposition enthalpy of the hydrated salt phase transition microcapsule modified diaphragm were determined by differential scanning calorimetry. (3) Electrophilic properties determination The contact angle of the hydrated salt phase change microcapsule modified membrane was measured using LB-083 secondary electrolyte and analyzed using a DSA100S droplet shape analyzer. The data obtained from the above experiments are shown in Tables 1 and 2 below: Table 1 Table 2 Conclusion: Based on the analysis of the above experimental data, the lithium iron phosphate batteries prepared in Examples 1-4 have higher initial discharge specific capacity and more stored energy; after five cycles, they have higher coulombic rate, lower average capacity decay rate, longer cycle life, and higher safety; furthermore, the hydrated salt phase change microcapsule modified separators prepared in Examples 1-4 have lower shrinkage rate and higher thermal stability under high temperature conditions; higher phase change enthalpy and decomposition enthalpy, absorbing more heat during phase change and decomposition, resulting in higher thermal stability; and higher contact angle, indicating superior electrolyte affinity of the hydrated salt phase change microcapsule modified separators; while the lithium iron phosphate batteries prepared in Comparative Examples 1-5 show significant differences from those in Examples 1-4 in all aspects, exhibiting poorer battery life, safety, and performance.

[0035] Comparative analysis of Comparative Example 1, where the battery separator is a polypropylene separator, with Example 1 shows that the polypropylene separator, after oxygen plasma surface treatment, is sequentially immersed in chitosan solution and vinyltriethoxysilane solution to obtain a plasma-modified separator. Oxygen plasma surface treatment of the polypropylene separator introduces oxygen-containing polar groups onto the separator surface, reducing the water contact angle, significantly improving the separator's hydrophilicity and surface energy, increasing the electrolyte's wetting rate on the separator surface, and improving battery performance. On the other hand, the oxygen-containing groups introduced on the plasma-activated membrane surface form hydrogen bonds with the hydroxyl groups of chitosan, which allows the chitosan solution to spread evenly on the membrane surface, improves the dispersibility of the chitosan solution on the membrane surface, and inhibits the clogging of membrane micropores.

[0036] Comparative analysis of Comparative Example 2 (without chitosan solution and vinyltriethoxysilane solution) and Example 1 shows that first impregnating with chitosan solution allows the hydrophilic groups of chitosan to form a hydration layer with water molecules, reducing the transport resistance of lithium ions in the electrolyte, increasing the migration rate of lithium ions, and improving battery performance; then impregnating with vinyltriethoxysilane inhibits the shedding of the chitosan layer and avoids clogging of the membrane micropores.

[0037] Comparative Example 3, which was not impregnated with vinyltriethoxysilane solution, and Example 1 were compared and analyzed. On the one hand, vinyltriethoxysilane hydrolyzes to generate hydroxyl groups, which form covalent bonds with the oxygen-containing groups on the membrane surface and the hydroxyl groups of chitosan through a condensation reaction. This acts as a bridge to improve the binding force between the membrane and chitosan, preventing the chitosan layer from falling off and causing blockage of the membrane micropores. On the other hand, vinyl groups construct a hydrophobic network in the membrane micropores, reducing the binding rate of chitosan and water molecules, preventing chitosan swelling, and preventing the chitosan layer from falling off and causing blockage of the membrane micropores.

[0038] Comparative analysis of Comparative Example 4 (which does not impregnate with chitosan solution) and Example 1 shows that the hydrophilic groups of chitosan form a hydration layer with water molecules, which reduces the transport resistance of lithium ions in the electrolyte, increases the migration rate of lithium ions, and improves battery performance.

[0039] Comparative analysis of Comparative Example 5 (without hydrated salt phase change microcapsule slurry) and Example 1 shows that coating the plasma-modified separator surface with hydrated salt phase change microcapsule slurry, wherein the hydrated salt phase change microcapsules use hydrated salt as the core material and hydrophilic modified boron nitride and silicon dioxide as the shell layer, when the local temperature of the battery reaches the solid-liquid phase change temperature and thermochemical decomposition temperature of the hydrated salt, the hydrated salt absorbs heat and melts and decomposes thermochemically, inhibiting heat diffusion and improving the thermal safety of the battery; However, using hydrated salt directly can lead to the loss of crystal water during endothermic melting, and free ions can corrode the battery electrodes, affecting battery life. By using a core-shell structure to confine the hydrated salt in a core-shell structure of silica-hydrophilic modified boron nitride-hydrated salt nanospace, the hydrated salt can undergo endothermic melting and thermochemical decomposition in the internal space, preventing battery thermal runaway and improving battery safety and lifespan.

[0040] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a hydrated salt phase change microcapsule modified diaphragm, characterized in that: Includes the following steps: Step 1: Add the hydrated salt phase change microcapsules and binder to the solvent and stir; The mixture was ultrasonically dispersed, removed, and magnetically stirred to obtain a hydrated salt phase change microcapsule slurry. Step 2: Place the lithium-ion battery separator in an organic solvent and immerse it; remove it, wash it with deionized water, immerse it in deionized water, and then immerse it again; place it in a plasma surface treatment instrument and treat it under an oxygen atmosphere; remove it and immerse it in a chitosan solution; remove it and immerse it in a vinyltriethoxysilane solution; remove it and vacuum dry it to obtain the plasma-modified separator. Step 3: Coat the slurry of hydrated salt phase change microcapsules onto the surface of the plasma-modified membrane, and vacuum dry to obtain the hydrated salt phase change microcapsule modified membrane.

2. The method for preparing a hydrated salt phase change microcapsule modified diaphragm according to claim 1, characterized in that: The hydrated salt phase change microcapsule slurry comprises the following components, expressed as follows by mass percentage: 5-20 wt% hydrated salt phase change microcapsules, 4-20 wt% binder, and the balance being solvent.

3. The method for preparing a hydrated salt phase change microcapsule modified diaphragm according to claim 1, characterized in that: The preparation method of the hydrated salt phase change microcapsules is as follows: hydrated salt is added to hydrophilic modified boron nitride, heated, and sonicated to obtain a mixed solution; cyclohexane is added to hydrophilic modified boron nitride, sonicated, and added to the mixed solution, maintaining a constant temperature and sonicating; hexadecyltrimethylammonium bromide is added, maintaining a constant temperature and stirring; 3-aminopropyltriethoxysilane and tetraethyl silicate are added, maintaining a constant temperature and stirring; ammonia water is added, maintaining a constant temperature and stirring; the mixture is filtered, washed with anhydrous ethanol, and dried to obtain hydrated salt phase change microcapsules. The mass ratio of the hydrated salt, hydrophilic modified boron nitride, cyclohexane, hexadecyltrimethylammonium bromide, 3-aminopropyltriethoxysilane, tetraethyl silicate, and ammonia is (5-43):(0.7-1):(25-40):(0.1-2):(1-5):(6-35):(7-60).

4. The method for preparing a hydrated salt phase change microcapsule modified diaphragm according to claim 1, characterized in that: The concentration of the chitosan solution is 0.5-2.5 wt%; The concentration of the vinyltriethoxysilane solution is 0.1-3 wt%.

5. The method for preparing a hydrated salt phase change microcapsule modified diaphragm according to claim 1, characterized in that: In step one, the conditions for ultrasonic dispersion are: ultrasonic frequency 39-41KHz, ultrasonic power 440-460W, ultrasonic dispersion for 20-30 minutes. In step one, the conditions for magnetic stirring are: stirring magnetically for 2.5-4 hours at a speed of 500-800 rpm.

6. The method for preparing a hydrated salt phase change microcapsule modified diaphragm according to claim 1, characterized in that: The mass ratio of the hydrated salt phase change microcapsules to the plasma-modified membrane is 1:(4-20).

7. The method for preparing a hydrated salt phase change microcapsule modified diaphragm according to claim 1, characterized in that: The adhesive is any one or more of polyvinylidene fluoride and sodium carboxymethyl cellulose. The solvent is any one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, and dimethyl sulfoxide; The lithium-ion battery separator is any one of polyethylene separator, polypropylene separator, or polypropylene / polyethylene / polypropylene composite separator; The organic solvent is any one of ethanol solution, isopropanol, and acetone.

8. The method for preparing a hydrated salt phase change microcapsule modified diaphragm according to claim 3, characterized in that: The hydrophilic modified boron nitride is any one of hydroxylated hexagonal boron nitride nanosheets, aminolated hexagonal boron nitride nanosheets, and carboxylated hexagonal boron nitride nanosheets; The method for preparing the hydrophilic modified boron nitride includes the following steps: Option 1: Add hexagonal boron nitride powder to sucrose, place it in a ball mill jar, and ball mill; wash with deionized water, sonicate, centrifuge, and obtain supernatant; take the supernatant, centrifuge, and obtain supernatant; take the supernatant, freeze dry, and obtain hydrophilic modified boron nitride; Option 2: Add hexagonal boron nitride powder to dopamine, add deionized water, mix evenly to obtain a slurry; take the slurry, sonicate, add agate balls, and liquid-phase ball mill to obtain hydrophilic modified boron nitride; Option 3: Add dopamine to Tris-HCl buffer and mix well to obtain a dopamine-Tris mixed solution; impregnate hexagonal boron nitride powder in the dopamine-Tris mixed solution, shake, wash with deionized water, and dry to obtain hydrophilic modified boron nitride. Option 4: Take hexagonal boron nitride powder, add it to tannic acid, add deionized water, mix evenly to obtain a slurry; take the slurry, sonicate it, add agate balls, and liquid-phase ball mill it to obtain hydrophilic modified boron nitride.

9. The method for preparing a hydrated salt phase change microcapsule modified diaphragm according to claim 3, characterized in that: The hydrated salt is any one or more of sodium thiosulfate pentahydrate, sodium acetate trihydrate, disodium hydrogen phosphate dodecahydrate, sodium sulfate decahydrate, calcium chloride hexahydrate, and strontium chloride hexahydrate.

10. The application of a hydrated salt phase change microcapsule modified separator prepared by the method of any one of claims 1-9 in the field of lithium-ion batteries.

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