A high-energy-density lithium battery temperature-resistant safety composite diaphragm and a preparation method thereof

Abstract

This invention belongs to the field of lithium battery separator technology, specifically relating to a high-energy-density, temperature-resistant, and safe composite separator for lithium batteries and its preparation method. Using aluminum chloride hexahydrate as the aluminum source, this invention prepares an alumina composite material with an aerogel structure through a sol-gel method combined with supercritical carbon dioxide drying. A coating slurry is then prepared using nanocellulose, polyacrylate binders, and dispersants. This slurry is coated onto a polypropylene substrate to form a composite separator. By using a relatively large coating thickness to ensure safety, the thermal shrinkage performance of the separator is reduced, while simultaneously achieving high energy density.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery separator technology, specifically relating to a high-energy-density lithium battery temperature-resistant and safe composite separator and its preparation method. Background Technology

[0002] Lithium-ion batteries consist of a positive electrode, a negative electrode, a separator, and an electrolyte. The separator does not directly participate in the chemical reactions that occur during charging and discharging, but its presence physically separates the anode and cathode, while providing an ion transport channel between the cathode and anode. The separator ensures the realization of the battery's charging and discharging functions and reduces potential safety hazards during battery use. The separator needs to have the following characteristics to ensure safe use: (1) Electronic insulation. Insulation is a necessary property of the separator. The separator needs to impede the flow of electrons through it to both sides, which requires the separator to have very high resistance and good electronic insulation; (2) Maintaining physical morphology and dimensional stability under high temperature conditions. Thermal stability is the characteristic of the separator to maintain stability at high temperatures, which is an important characteristic for maintaining the safe operation of the battery; (3) Not reacting with the substances inside the battery or intervening in the reactions inside the battery. The separator is in an environment of electrolyte and continuous electrochemical reactions for a long time, which requires the separator to maintain stable chemical properties and not interfere with the reactions between the electrodes.

[0003] Chinese patent (publication number CN116565456A) discloses a lithium battery separator, its preparation method, and its application. The lithium battery separator prepared by this invention has a thin and light coating with high heat resistance; the thermal shrinkage of the coating after baking at 180°C for 1 hour is less than 2%, which meets the requirements for isolating the positive and negative electrodes of the lithium battery and transporting lithium ions. It also improves the thermal stability and adhesion of the lithium battery separator. In the event of abnormal temperature rise inside the battery, it effectively prevents the cell from melting and cracking, thus improving the energy density and kinetic performance of the lithium battery cell. However, the coating thickness prepared by this patented technology is too small, requiring high coating precision. Furthermore, the thin coating is easily affected by the environment, leading to insufficient product safety.

[0004] Therefore, how to modify the battery separator coating material to ensure safety while using a larger coating thickness, reduce the thermal shrinkage performance of the separator, and obtain high energy density has become a key area that needs to be addressed. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a high-energy-density lithium battery temperature-resistant and safe composite separator and its preparation method. The present invention uses aluminum chloride hexahydrate as the aluminum source and prepares an alumina composite material with an aerogel structure through a sol-gel method combined with supercritical carbon dioxide drying. A coating slurry is then prepared by combining nanocellulose, polyacrylate binders, and dispersants. This slurry is then coated onto a polypropylene substrate to form a composite separator. By using a larger coating thickness to ensure safety, the thermal shrinkage performance of the separator is reduced, while simultaneously achieving high energy density.

[0006] In a first aspect, the present invention provides a method for preparing a high-energy-density lithium battery temperature-resistant safety composite separator, comprising the following steps:

[0007] By weight, 16-20 parts of alumina composite material, 10-16 parts of nanocellulose, 4-6 parts of polyacrylate binder and 0.2-0.4 parts of dispersant are added to 400-500 parts of deionized water and ultrasonically dispersed for 50-60 minutes to obtain a coating slurry. The coating slurry is then coated onto a polypropylene substrate and dried to form a coating, thereby obtaining a high-energy-density lithium battery temperature-resistant safety composite separator.

[0008] As a preferred embodiment, the alumina composite material of the present invention may be in the following weight proportions: 16 parts, 17 parts, 18 parts, 19 parts, or 20 parts, etc.

[0009] As a preferred embodiment, the weight parts of the nanocellulose in this invention can be 10 parts, 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, or 16 parts, etc.

[0010] As a preferred embodiment, the polyacrylate adhesive described in this invention may be in the following weight proportions: 4 parts, 4.5 parts, 5 parts, 5.5 parts, or 6 parts, etc.

[0011] As a preferred embodiment, the weight parts of the dispersant in this invention can be 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, or 0.4 parts, etc.

[0012] As a preferred technical solution of the present invention, the preparation method of the alumina composite material includes: adding halloysite nano-clay to aluminum chloride hexahydrate to support titanium dioxide to form a precursor solution, and then performing gelation treatment on the precursor solution to obtain the alumina composite material.

[0013] The alumina composite material of the present invention uses aluminum chloride hexahydrate as the aluminum source and halloysite nanoclay loaded with titanium dioxide as the reinforcing phase. The alumina composite material with an aerogel structure is prepared by sol-gel method combined with supercritical carbon dioxide drying.

[0014] As a preferred technical solution of the present invention, the preparation method of halloysite nanoclay supported titanium dioxide includes: dispersing 2.4 to 2.8 parts by weight of halloysite nanoclay in 100 to 120 parts of anhydrous ethanol, then adding 1.2 to 1.6 parts of titanium tetrachloride and sonicating for 30 to 40 minutes, stirring for 80 to 90 minutes, adding 0.012 to 0.016 parts of sodium hydroxide, heat-treating at 170 to 180°C for 20 to 24 hours, centrifuging, washing with water, and drying to obtain halloysite nanoclay supported titanium dioxide.

[0015] As a preferred technical solution of the present invention, the preparation method of the precursor solution includes: adding 2-4 parts of aluminum chloride hexahydrate to a mixture of 30-40 parts of deionized water and 20-30 parts of anhydrous ethanol, and then adding 1.6-2.4 parts of halloysite nanoclay-supported titanium dioxide and stirring for 50-60 minutes to obtain the precursor solution.

[0016] As a preferred embodiment of the present invention, the gelation treatment step includes: adding 0.2 to 0.4 parts of hydroxyethyl cellulose to 50 to 70 parts of precursor solution and stirring for 160 to 180 min, then adding 0.6 to 0.8 parts of 1,2-epoxypropane and gelling at room temperature for 4 to 6 h, using anhydrous ethanol for solvent replacement, drying with supercritical carbon dioxide, and pulverizing to obtain an alumina composite material.

[0017] As a preferred technical solution of the present invention, the conditions for supercritical carbon dioxide drying are: temperature of 40-44°C and pressure of 12-13 MPa.

[0018] As a preferred embodiment of the present invention, the nanocellulose is modified nanocellulose;

[0019] The method for preparing the modified nanocellulose includes: firstly, acetylifying commercially available nanocellulose to obtain acetylated nanocellulose; and then modifying the acetylated nanocellulose with cobalt nitrate hexahydrate and 2-methylimidazole to obtain modified nanocellulose.

[0020] The modified nanocellulose of the present invention uses nanocellulose as raw material. First, acetylated nanocellulose is obtained by acetylation treatment. Then, cobalt nitrate hexahydrate and 2-methylimidazole are used for modification to grow organometallic framework particles in situ on the surface of nanocellulose, thereby preparing modified nanocellulose.

[0021] As a preferred embodiment of the present invention, the acetylation treatment step includes: dispersing 4-6 parts by weight of commercially available nanocellulose in 400-500 parts by weight of N,N-dimethylacetamide, then adding 1.8-2.4 parts by weight of pyridine and 0.6-0.8 parts by weight of acetyl chloride, and stirring the mixture at 70-80°C for 50-60 minutes.

[0022] As a preferred embodiment of the present invention, the modification process includes: dispersing 1.5 to 1.7 parts of acetylated nanocellulose in 140 to 160 parts of methanol, adding 1.6 to 1.8 parts of cobalt nitrate hexahydrate and stirring for 6 to 8 hours, then adding 1.9 to 2.1 parts of 2-methylimidazole and 140 to 160 parts of methanol and stirring for 22 to 24 hours, centrifuging, washing with ethanol, and drying to obtain modified nanocellulose.

[0023] As a preferred embodiment of the present invention, the polyacrylate adhesive is Sanrui High-Tech Materials LIB-S101 adhesive and Sanrui High-Tech Materials LIB-S106P5 adhesive.

[0024] As a preferred embodiment of the present invention, the viscosity of the LIB-S101 adhesive at 25°C is 10-100 mPa·s, and the viscosity of the LIB-S106P5 adhesive at 25°C is 50-1000 mPa·s.

[0025] As a preferred embodiment of the present invention, the mass ratio of LIB-S101 adhesive to LIB-S106P5 adhesive is (1-2):1.

[0026] Polyacrylate binders are compounded using Sanrui High-Tech Materials' LIB-S101 binder and LIB-S106P5 binder. LIB-S101 binder has good wetting and dispersing properties for alumina particles, exhibiting excellent dispersion and adhesion properties, ensuring good adhesion of the alumina composite material and thus achieving high energy density. LIB-S106P5 binder has a high glass transition temperature and excellent heat shrinkage resistance, which can reduce the heat shrinkage of the diaphragm under high-temperature conditions. The overall performance of the composite diaphragm is improved by compounding the binders.

[0027] As a preferred embodiment of the present invention, the thickness of the coating is 2 μm.

[0028] As a preferred embodiment of the present invention, the dispersant is selected from BYK-LPC20992 or BASF AA4140.

[0029] A second aspect of the present invention provides a high-energy-density lithium battery temperature-resistant safety composite separator prepared by the method described in the first aspect.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) This invention achieves effective composite of alumina composite material and modified nanocellulose on polypropylene substrate by compounding polyacrylate binder, forming a "multi-level channel of alumina composite material + rigid skeleton of organometallic" structure in the coating. While ensuring safety by using a large coating thickness, it effectively reduces the thermal shrinkage rate of the composite material and obtains high energy density.

[0032] (2) The aerogel structure alumina in the composite material of the present invention can provide more ion transport channels, enhance electrolyte wettability, and promote rapid lithium ion migration. At the same time, titanium dioxide can absorb some impurity electrolytes, which helps to reduce the interfacial impedance between the separator and the electrode, and has good compatibility with the electrolyte. It can promote lithium ion transport and improve the ionic conductivity of the separator, thereby achieving high energy density. Halloysite nanotubes are a natural nanotube clay material with excellent high temperature resistance. Combined with the porous network and high specific surface area of ​​the aerogel structure alumina, it can effectively block heat conduction and inhibit thermal shrinkage under high temperature conditions.

[0033] (3) The modified nanocellulose-supported organometallic framework particles of the present invention have a high specific surface area, providing more pathways for lithium ion migration. At the same time, the hydroxyl groups of nanocellulose can enhance the wettability of the electrolyte and improve the ionic conductivity, thereby obtaining a high energy density. In addition, the organometallic framework has a high thermal decomposition temperature, which can form a stable lattice structure at high temperature, suppressing the thermal shrinkage and melting of the membrane. Nanocellulose can provide flexibility and rigidity, making the membrane resistant to shrinkage at high temperature. Detailed Implementation

[0034] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0035] The sources of some components in the examples and comparative examples are as follows:

[0036] Aluminum chloride hexahydrate, CAS No. 7784-13-6, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0037] Halloysite nanoclay, item number H431905, was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0038] Titanium tetrachloride, CAS No. 7550-45-0, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0039] Hydroxyethyl cellulose, CAS No. 9004-62-0, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0040] 1,2-Epoxypropane, CAS No. 75-56-9, purchased from Sinopharm Chemical Reagent Co., Ltd.

[0041] Ceramic powder, purchased from Jiangsu Jingshengyuan New Material Technology Co., Ltd.;

[0042] Commercially available nanocellulose, product number TL-011, purchased from Nanjing Tianlu Nanotechnology Co., Ltd.

[0043] Pyridine, CAS No. 110-86-1, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0044] Acetyl chloride, CAS No. 75-36-5, was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0045] Cobalt nitrate hexahydrate, CAS No. 10026-22-9, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0046] 2-Methylimidazole, CAS No. 693-98-1, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0047] LIB-S101 adhesive, with a viscosity of 10-100 mPa·s at 25℃, was purchased from Shanghai Sanrui Polymer Materials Co., Ltd.

[0048] LIB-S106P5 adhesive, with a viscosity of 50-1000 mPa·s at 25℃, was purchased from Shanghai Sanrui Polymer Materials Co., Ltd.

[0049] Dispersants: BYK-LPC20992 from BYK Chemicals, AA4140 from BASF.

[0050] Example 1

[0051] This embodiment provides a method for preparing a high-energy-density lithium battery temperature-resistant safety composite separator, including the following steps:

[0052] By weight, 20 parts of alumina composite material, 16 parts of modified nanocellulose, 6 parts of polyacrylate binder (4 parts of LIB-S101 binder and 2 parts of LIB-S106P5 binder) and 0.4 parts of dispersant (BYK-LPC20992) were added to 500 parts of deionized water and ultrasonically dispersed for 60 min to obtain a coating slurry. The coating slurry was coated on a polypropylene substrate and dried to form a coating with a thickness of 2 μm, thereby obtaining a high-energy-density lithium battery temperature-resistant safety composite separator.

[0053] Preparation of the alumina composite material: (1) By weight, 2.8 parts halloysite nanoclay were dispersed in 120 parts anhydrous ethanol, then 1.6 parts titanium tetrachloride were added and ultrasonicated for 40 min. After stirring for 90 min, 0.016 parts sodium hydroxide were added. The mixture was heat-treated at 180℃ for 20 h, centrifuged, washed with water, and dried to obtain halloysite nanoclay-loaded titanium dioxide; (2) 4 parts aluminum chloride hexahydrate were added to a mixture of 40 parts deionized water and 30 parts anhydrous ethanol, then 2.4 parts halloysite nanoclay-loaded titanium dioxide were added and stirred for 60 min to obtain a precursor solution; 0.4 parts hydroxyethyl cellulose were added to 70 parts of the precursor solution and stirred for 180 min, then 0.8 parts 1,2-epoxypropane were added and gelled at room temperature for 6 h. Anhydrous ethanol was used for solvent replacement, and the mixture was dried with supercritical carbon dioxide (temperature 44℃, pressure 12 MPa), pulverized, and the alumina composite material was obtained.

[0054] Preparation of the modified nanocellulose: By weight, 6 parts of commercially available nanocellulose were dispersed in 500 parts of N,N-dimethylacetamide, then 2.4 parts of pyridine and 0.8 parts of acetyl chloride were added, and the mixture was stirred at 80°C for 50 min; 1.7 parts of acetylated nanocellulose were dispersed in 160 parts of methanol, 1.8 parts of cobalt nitrate hexahydrate were added and stirred for 8 h, then 2.1 parts of 2-methylimidazole and 160 parts of methanol were added and stirred for 24 h, centrifuged, washed with ethanol, and dried to obtain modified nanocellulose.

[0055] Example 2

[0056] This embodiment provides a method for preparing a high-energy-density lithium battery temperature-resistant safety composite separator, including the following steps:

[0057] By weight, 16 parts of alumina composite material, 10 parts of modified nanocellulose, 4 parts of polyacrylate binder (2 parts of LIB-S101 binder and 2 parts of LIB-S106P5 binder) and 0.2 parts of dispersant BASF AA4140 were added to 400 parts of deionized water and ultrasonically dispersed for 50 min to obtain a coating slurry. The coating slurry was coated on a polypropylene substrate and dried to form a coating with a thickness of 2 μm, thereby obtaining a high-energy-density lithium battery temperature-resistant safety composite separator.

[0058] Preparation of the alumina composite material: (1) By weight, 2.4 parts halloysite nanoclay were dispersed in 100 parts anhydrous ethanol, then 1.2 parts titanium tetrachloride were added and ultrasonicated for 30 min. After stirring for 80 min, 0.012 parts sodium hydroxide were added. The mixture was heat-treated at 170℃ for 24 h, centrifuged, washed with water, and dried to obtain halloysite nanoclay-loaded titanium dioxide; (2) 2 parts aluminum chloride hexahydrate were added to a mixture of 30 parts deionized water and 20 parts anhydrous ethanol, then 1.6 parts halloysite nanoclay-loaded titanium dioxide were added and stirred for 50 min to obtain a precursor solution; 0.2 parts hydroxyethyl cellulose were added to 50 parts of the precursor solution and stirred for 160 min, then 0.6 parts 1,2-epoxypropane were added and gelled at room temperature for 4 h. Anhydrous ethanol was used for solvent replacement, and the mixture was dried with supercritical carbon dioxide (temperature 40℃, pressure 12 MPa), pulverized, and the alumina composite material was obtained.

[0059] Preparation of the modified nanocellulose: By weight, 4 parts of commercially available nanocellulose were dispersed in 400 parts of N,N-dimethylacetamide, then 1.8 parts of pyridine and 0.6 parts of acetyl chloride were added, and the mixture was stirred at 70°C for 60 min; 1.5 parts of acetylated nanocellulose were dispersed in 140 parts of methanol, 1.6 parts of cobalt nitrate hexahydrate were added and stirred for 6 h, then 1.9 parts of 2-methylimidazole and 140 parts of methanol were added and stirred for 22 h, centrifuged, washed with ethanol, and dried to obtain the modified nanocellulose.

[0060] Example 3

[0061] This embodiment provides a method for preparing a high-energy-density lithium battery temperature-resistant safety composite separator, including the following steps:

[0062] By weight, 18 parts of alumina composite material, 12 parts of modified nanocellulose, 5 parts of polyacrylate binder (3 parts of LIB-S101 binder and 2 parts of LIB-S106P5 binder) and 0.3 parts of dispersant BYK-LPC20992 were added to 450 parts of deionized water and ultrasonically dispersed for 55 min to obtain a coating slurry. The coating slurry was coated on a polypropylene substrate and dried to form a coating with a thickness of 2 μm, thereby obtaining a high-energy-density lithium battery temperature-resistant safety composite separator.

[0063] Preparation of the alumina composite material: (1) By weight, 2.6 parts halloysite nanoclay were dispersed in 110 parts anhydrous ethanol, then 1.4 parts titanium tetrachloride were added and ultrasonicated for 35 min. After stirring for 85 min, 0.014 parts sodium hydroxide were added. The mixture was heat-treated at 175℃ for 22 h, centrifuged, washed with water, and dried to obtain halloysite nanoclay-loaded titanium dioxide; (2) 3 parts aluminum chloride hexahydrate were added to a mixture of 35 parts deionized water and 25 parts anhydrous ethanol, then 1.8 parts halloysite nanoclay-loaded titanium dioxide were added and stirred for 55 min to obtain a precursor solution; 0.3 parts hydroxyethyl cellulose were added to 60 parts of the precursor solution and stirred for 170 min, then 0.6-0.8 parts 1,2-epoxypropane were added and gelled at room temperature for 5 h. Anhydrous ethanol was used for solvent replacement, and the mixture was dried with supercritical carbon dioxide (temperature 42℃, pressure 12.5 MPa), pulverized, and the alumina composite material was obtained.

[0064] Preparation of the modified nanocellulose: By weight, 5 parts of commercially available nanocellulose were dispersed in 450 parts of N,N-dimethylacetamide, then 2.2 parts of pyridine and 0.7 parts of acetyl chloride were added, and the mixture was stirred at 75°C for 55 min; 1.6 parts of acetylated nanocellulose were dispersed in 150 parts of methanol, 1.7 parts of cobalt nitrate hexahydrate were added and stirred for 7 h, then 2.0 parts of 2-methylimidazole and 150 parts of methanol were added and stirred for 23 h, centrifuged, washed with ethanol, and dried to obtain the modified nanocellulose.

[0065] Comparative Example 1

[0066] The difference between this comparative example and Example 1 is that commercially available ceramic powder is used instead of alumina composite material.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Example 1 is that commercially available nanocellulose (product number TL-011) was used instead of modified nanocellulose.

[0069] Comparative Example 3

[0070] The difference between this comparative example and Example 1 is that the amount of LIB-S101 adhesive in the polyacrylate adhesive is changed to 5 parts, and the amount of LIB-S106P5 adhesive is changed to 1 part.

[0071] Comparative Example 4

[0072] The difference between this comparative example and Example 1 is that the amount of LIB-S101 adhesive in the polyacrylate adhesive is changed to 2 parts, and the amount of LIB-S106P5 adhesive is changed to 4 parts.

[0073] The performance of the diaphragms provided in the above embodiments and comparative examples was tested using the following methods:

[0074] (1) Air permeability test: The test shall be conducted in accordance with the requirements of GB / T 36363-2018 Polyolefin separator for lithium-ion batteries.

[0075] (2) Heat shrinkage performance test: The test was conducted in accordance with the requirements of GB / T 36363-2018 Polyolefin separator for lithium-ion batteries, and the temperature was 180℃.

[0076] (3) Energy density test: The battery separator sample was cut into 60mm wide battery separators. Lithium cobalt oxide was used as the positive electrode active material, PVDF as the positive electrode binder, carbon nanotubes as the conductive agent, graphite as the negative electrode, styrene-butadiene rubber as the binder, and sodium carboxymethyl cellulose as the thickener to make a soft pack battery. The battery capacity, the average output voltage of the battery during the charging and discharging process and the battery weight were measured. The energy density was calculated by the following formula: Energy density = Battery capacity × Average voltage ÷ Battery weight.

[0077] The performance test data above are shown in Table 1.

[0078] Table 1 Performance Test Results

[0079]

[0080] As can be seen from the above, the present invention achieves effective composite of alumina composite material and modified nanocellulose on a polypropylene substrate by compounding polyacrylate binders, forming a "multi-level pore structure of alumina composite material + organometallic rigid skeleton" structure in the coating, thereby preparing a high-energy-density lithium battery temperature-resistant and safe composite separator (Examples 1 to 3). Its comprehensive performance is the best. While ensuring safety by using a large coating thickness, it effectively reduces the thermal shrinkage rate of the composite material and obtains high energy density.

[0081] Compared with Example 1, using commercially available ceramic powder instead of alumina composite material resulted in poorer heat shrinkage performance and lower energy density (Comparative Example 1); compared with Example 1, using commercially available nanocellulose (product number TL-011) instead of modified nanocellulose resulted in poorer heat shrinkage performance and lower energy density (Comparative Example 2); compared with Example 1, the amount of LIB-S101 binder in the polyacrylate binder was changed to 5 parts and the amount of LIB-S106P5 binder was changed to 1 part. Due to the insufficient amount of LIB-S106P5 binder with good heat shrinkage resistance, the compounding effect was poor, resulting in poorer heat shrinkage performance (Comparative Example 3); compared with Example 1, the amount of LIB-S101 binder in the polyacrylate binder was changed to 2 parts and the amount of LIB-S106P5 binder was changed to 4 parts. Due to the insufficient amount of LIB-S101 binder with good wetting and dispersing properties for alumina particles, the compounding effect was poor, resulting in lower energy density (Comparative Example 4).

Claims

1. A method for preparing a high-energy-density lithium battery temperature-resistant safety composite separator, characterized in that, Includes the following steps: By weight, 16-20 parts of alumina composite material, 10-16 parts of modified nanocellulose, 4-6 parts of polyacrylate binder and 0.2-0.4 parts of dispersant are added to 400-500 parts of deionized water and ultrasonically dispersed for 50-60 minutes to obtain a coating slurry. The coating slurry is then coated onto a polypropylene substrate and dried to form a coating, thereby obtaining a high-energy-density lithium battery temperature-resistant safety composite separator. The preparation method of the alumina composite material includes: adding halloysite nanoclay to aluminum chloride hexahydrate to support titanium dioxide to form a precursor solution, and then performing a gelation treatment on the precursor solution to obtain the alumina composite material. The method for preparing halloysite nanoclay-supported titanium dioxide includes: dispersing 2.4-2.8 parts by weight of halloysite nanoclay in 100-120 parts of anhydrous ethanol, then adding 1.2-1.6 parts of titanium tetrachloride and sonicating for 30-40 min, stirring for 80-90 min, adding 0.012-0.016 parts of sodium hydroxide, heat-treating at 170-180℃ for 20-24 h, centrifuging, washing with water, and drying to obtain halloysite nanoclay-supported titanium dioxide; The preparation method of the precursor solution includes: adding 2-4 parts of aluminum chloride hexahydrate to a mixture of 30-40 parts of deionized water and 20-30 parts of anhydrous ethanol, and then adding 1.6-2.4 parts of halloysite nanoclay-supported titanium dioxide and stirring for 50-60 minutes to obtain the precursor solution; The gelation process includes: adding 0.2 to 0.4 parts of hydroxyethyl cellulose to 50 to 70 parts of precursor solution and stirring for 160 to 180 min; then adding 0.6 to 0.8 parts of 1,2-epoxypropane and gelling at room temperature for 4 to 6 h; using anhydrous ethanol for solvent replacement; drying with supercritical carbon dioxide; and pulverizing to obtain the alumina composite material. The method for preparing the modified nanocellulose includes: firstly, acetylifying commercially available nanocellulose to obtain acetylated nanocellulose; and then modifying the acetylated nanocellulose with cobalt nitrate hexahydrate and 2-methylimidazole to obtain modified nanocellulose.

2. The method for preparing a high-energy-density lithium battery temperature-resistant safety composite separator according to claim 1, characterized in that, The acetylation treatment step includes: dispersing 4-6 parts by weight of commercially available nanocellulose in 400-500 parts by weight of N,N-dimethylacetamide, then adding 1.8-2.4 parts by weight of pyridine and 0.6-0.8 parts by weight of acetyl chloride, and stirring the mixture at 70-80°C for 50-60 minutes.

3. The method for preparing a high-energy-density lithium battery temperature-resistant safety composite separator according to claim 1, characterized in that, The modification process includes: dispersing 1.5-1.7 parts of acetylated nanocellulose in 140-160 parts of methanol, adding 1.6-1.8 parts of cobalt nitrate hexahydrate and stirring for 6-8 hours, then adding 1.9-2.1 parts of 2-methylimidazole and 140-160 parts of methanol and stirring for 22-24 hours, centrifuging, washing with ethanol, and drying to obtain modified nanocellulose.

4. The method for preparing a high-energy-density lithium battery temperature-resistant safety composite separator according to claim 1, characterized in that, The polyacrylate adhesives are Sanrui High-Tech Materials LIB-S101 adhesive and Sanrui High-Tech Materials LIB-S106P5 adhesive; The viscosity of the LIB-S101 adhesive at 25°C is 10–100 mPa·s, and the viscosity of the LIB-S106P5 adhesive at 25°C is 50–1000 mPa·s. The mass ratio of LIB-S101 adhesive to LIB-S106P5 adhesive is (1~2):

1.

5. The method for preparing a high-energy-density lithium battery temperature-resistant safety composite separator according to claim 1, characterized in that, The coating has a thickness of 2 μm.

6. A high-energy-density lithium battery temperature-resistant and safe composite separator, characterized in that... ， Prepared by the method according to any one of claims 1-5.

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