High-conductivity composite coating diaphragm and its preparation method and application

Abstract

The present invention discloses a high-conductivity composite coating diaphragm, its preparation method, and application. The high-conductivity composite coating diaphragm comprises: a base film and a coating coated on the base film. The coating comprises: poly(p-phenylene terephthalamide), lithium aluminum titanium phosphate, aluminum nitride, and a first substance, the first substance being one or a mixture of lithium nitrate, sodium dodecylbenzenesulfonate, an organic nitrate, and isosorbide dinitrate. The present invention improves the transport of lithium ions in the coating diaphragm by introducing aluminum nitride, thereby improving the ionic conductivity of the coating diaphragm. The introduction of PPTA further enhances the heat resistance and adhesion of the coating diaphragm. The introduction of LATP provides the coating diaphragm with good porosity, thermal stability, and liquid absorption rate. The first substance is introduced as a dispersant for LATP, improving its dispersibility. Furthermore, the inclusion of lithium in the first substance replenishes lithium in the diaphragm, synergizing with aluminum nitride to enhance the ionic conductivity of the diaphragm.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery separators, and in particular relates to a high-conductivity composite coating separator, a preparation method thereof, and applications thereof. Background Art

[0002] With the rapid development of high-power equipment such as new energy electric vehicles and large-scale energy storage systems, large-capacity, high-energy-density power and energy storage lithium-ion batteries have shown a blowout development in recent years.

[0003] However, the frequent spontaneous combustion and explosion incidents of new energy electric vehicles in recent years have raised significant concerns and raised questions about the safety of power lithium-ion batteries. One of the key reasons is that the performance of existing lithium battery separators cannot meet the application requirements of high-energy-density batteries. Power lithium-ion batteries require higher safety, greater capacity, consistent and stable output over time, and high-rate charge and discharge performance. As the "third electrode" of lithium-ion batteries, the separator is a key material that ensures battery safety and performance, requiring high strength, heat resistance, flame retardancy, high porosity, uniformity, and good wettability. Separators play two primary roles in lithium-ion batteries. First, the separator material must possess excellent insulation and a certain strength to prevent direct contact between the positive and negative electrodes within the battery, effectively prevent puncture by burrs and dendrites that could cause short circuits, and ensure that it does not undergo significant dimensional changes under sudden high-temperature conditions, thereby ensuring battery safety. Second, the separator's porous structure provides a good migration path for lithium ions, ensuring stable and efficient battery operation. Therefore, the development of separators with high safety is of great significance. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the present invention aims to provide a high-conductivity composite coating diaphragm.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned high-conductivity composite coating diaphragm.

[0006] Another object of the present invention is to provide a slurry.

[0007] Another object of the present invention is to provide a method for preparing the slurry.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] A high-conductivity composite coating diaphragm comprises a base film and a coating coated on the base film, wherein the coating comprises poly(p-phenylene terephthalamide) (PPTA), lithium aluminum titanium phosphate (LATP), aluminum nitride, and a first substance, wherein the ratio of poly(p-phenylene terephthalamide) (PPTA), lithium aluminum titanium phosphate (LATP), aluminum nitride, and the first substance is (7-12): (2-10): (0.15-1): (0.05-0.3) by mass, and the first substance is one or a mixture of several of lithium nitrate, sodium dodecylbenzenesulfonate, organic nitrate, and isosorbide dinitrate.

[0010] The method for preparing the above-mentioned high-conductivity composite coating membrane comprises: coating the slurry on the base membrane to obtain a coating on the base membrane to obtain a high-conductivity composite coating membrane precursor; extracting the high-conductivity composite coating membrane precursor and dehydrating it to obtain the high-conductivity composite coating membrane.

[0011] In the above technical solution, the extraction adopts an extraction liquid, and the high-conductivity composite coating membrane precursor passes through the extraction liquids with decreasing extractant concentrations in sequence, and the extractant is N-methylpyrrolidone (NMP).

[0012] In the above technical solution, the extracts with the highest to lowest extractant concentrations are the first extract, the second extract, the third extract, and the fourth extract, respectively. The first extract, the second extract, and the third extract are mixtures of extractant and water, and the fourth extract is water. The concentration of the extractant in the first extract is 65-80 wt%, the concentration of the extractant in the second extract is 40-60 wt%, and the concentration of the extractant in the third extract is 20-40 wt%.

[0013] In the above technical solution, the dehydration treatment is drying at 50-60° C. for 6-12 minutes.

[0014] A slurry includes poly(p-phenylene terephthalamide) (PPTA), lithium aluminum titanium phosphate (LATP), aluminum nitride, and a first substance. Calculated by mass, in the slurry, the ratio of poly(p-phenylene terephthalamide) (PPTA), lithium aluminum titanium phosphate (LATP), aluminum nitride, and the first substance is (7-12): (2-10): (0.15-1): (0.05-0.3). The first substance is one or more of lithium nitrate, sodium dodecylbenzenesulfonate, organic nitrate, and isosorbide dinitrate.

[0015] In the above technical solution, the slurry also includes: a solvent, which is a single-component solvent and / or a multi-component solvent. The single-component solvent is N-methylpyrrolidone, and the multi-component solvent includes: solvent 1 and solvent 2. Solvent 1 includes: acetonitrile and / or dimethylformamide, and solvent 2 includes: one or a mixture of hexamethylphosphoramide, dimethylacetamide and tetramethylurea.

[0016] In the above technical solution, the slurry also includes: calcium chloride.

[0017] In the above technical solution, the ratio of the mass fraction of lithium aluminum titanium phosphate (LATP) to the volume fraction of the solvent is (2-10):(93-97), the unit of the mass fraction is g, and the unit of the volume fraction is mL.

[0018] In the above technical solution, the ratio of calcium chloride to lithium aluminum titanium phosphate (LATP) is (0.05-0.1):(2-8) in parts by mass.

[0019] A method for preparing a slurry comprises: mixing a first slurry and a second slurry until uniform to obtain the slurry, wherein the first slurry comprises: lithium aluminum titanium phosphate (LATP), aluminum nitride, a first substance, and a first solvent, and the second slurry comprises: poly(p-phenylene terephthalamide) (PPTA), calcium chloride, and a second solvent; wherein, by mass, the ratio of poly(p-phenylene terephthalamide) (PPTA), lithium aluminum titanium phosphate (LATP), aluminum nitride, and the first substance is (7-12): (2-10): (0.15-1): (0.05-0.3), and the first substance is one or more of lithium nitrate, sodium dodecylbenzenesulfonate, an organic nitrate, and isosorbide dinitrate.

[0020] The ratio of the mass fraction of lithium aluminum titanium phosphate (LATP) to the volume fraction of the first solvent is (16-33): (60.8-82.5), the unit of mass fraction is g, and the unit of volume fraction is mL; the ratio of the first solvent to the second solvent is (6.08-16.5): (70-90) by volume; and the ratio of calcium chloride to lithium aluminum titanium phosphate (LATP) is (0.05-0.1): (2-8) by mass.

[0021] In the above technical solution, the first slurry and the second slurry are mixed and stirred at 30-45° C. and 350-400 r / min for 3-5 hours until they are uniform.

[0022] In the above technical solution, the method for preparing the first slurry is: mixing LATP, aluminum nitride, the first substance and the first solvent until they are uniformly dispersed.

[0023] In the method for preparing the first slurry, LATP, aluminum nitride, the first substance and the first solvent are mixed and wet ball milled for 3 to 5 hours to achieve uniform dispersion.

[0024] In the above technical solution, the method for preparing the second slurry is: mixing calcium chloride and a second solvent at 70-85° C., stirring until uniform, cooling to 0-3° C., and then adding p-phenylenediamine (PPDA), terephthaloyl chloride (TPC) and pyridine, stirring until uniform, to obtain a second slurry, wherein the ratio of the volume fraction of the second solvent, the mass fraction of p-phenylenediamine, the mass fraction of terephthaloyl chloride and the volume fraction of pyridine is (90-110): (4-5): (7-9): (4-5), wherein the unit of mass fraction is g, and the unit of volume fraction is mL (p-phenylenediamine and terephthaloyl chloride are used to synthesize poly (p-phenylenediamine) (PPTA), and pyridine is used to remove small molecular HCl generated during the synthesis of PPTA).

[0025] In the above technical solution, the first solvent is one or a mixture of N-methylpyrrolidone, acetonitrile and dimethylformamide.

[0026] In the above technical solution, the second solvent is one or a mixture of hexamethylphosphoramide, dimethylacetamide, N-methylpyrrolidone and tetramethylurea.

[0027] In the above technical solution, the first solvent and the second solvent may be the same or different.

[0028] In the above technical solution, the method for obtaining lithium aluminum titanium phosphate (LATP) is: uniformly mixing a lithium source, an aluminum source, a titanium source and ammonium dihydrogen phosphate to obtain a first powder, keeping the first powder at 700-900°C for 8 hours to obtain a LATP sintered block, grinding it into powder, and obtaining lithium aluminum titanium phosphate (LATP), wherein, based on the amount of substance, the ratio of lithium in the lithium source, aluminum in the aluminum source, titanium in the titanium source and phosphorus in the ammonium dihydrogen phosphate is (10-15): (1-5): (30-35): (55-65);

[0029] In the method for obtaining LATP, the lithium source is lithium carbonate or lithium nitrate; the aluminum source is boehmite or aluminum oxide; and the titanium source is one or a mixture of titanium dioxide, titanium hydroxide and tetrabutyl titanate.

[0030] In the method for obtaining LATP, a lithium source, an aluminum source, a titanium source and ammonium dihydrogen phosphate are uniformly mixed by wet ball milling for 2 to 3 hours.

[0031] In the method for obtaining LATP, wet ball milling is followed by drying, the drying temperature is 60 to 80° C., and the drying time is 16 to 24 hours.

[0032] In the method for obtaining LATP, the rate of heating to 700-900°C is 4-6°C / min.

[0033] In the above technical solution, the ball-to-material ratio of the wet ball mill is (0.8-1.2): (6-8), the wet ball mill uses grinding balls with a diameter of 5-10 mm, the orbital speed of the wet ball mill is 180-250 r / min, and the rotation speed is 550-650 r / min.

[0034] Application of high conductivity composite coating separators in lithium-ion batteries.

[0035] The invention discloses a method for synergistically improving the temperature resistance, breakdown voltage and / or adhesion of a diaphragm using four substances, wherein the four substances are poly(p-phenylene terephthalamide) (PPTA), lithium aluminum titanium phosphate (LATP), aluminum nitride and a first substance, wherein the first substance is a mixture of one or more of lithium nitrate, sodium dodecylbenzenesulfonate, organic nitrate and isosorbide dinitrate, and the ratio of poly(p-phenylene terephthalamide) (PPTA), lithium aluminum titanium phosphate (LATP), aluminum nitride and the first substance is (7-12): (2-10): (0.15-1): (0.05-0.3) by mass.

[0036] The application of a first substance, lithium aluminum titanium phosphate (LATP) and aluminum nitride to synergistically improve the ionic conductivity of the diaphragm, wherein the first substance is one or a mixture of lithium nitrate, sodium dodecylbenzenesulfonate, organic nitrate and isosorbide dinitrate.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] 1. The present invention improves the transmission of lithium ions in the coating membrane by introducing aluminum nitride, thereby improving the ionic conductivity of the coating membrane; the introduction of PPTA further improves the temperature resistance and adhesion of the coating membrane; the introduction of LATP brings good porosity (good air permeability), thermal stability and liquid absorption rate to the coating membrane; the introduction of the first substance as a dispersant for LATP improves the dispersibility of LATP, and at the same time, because it contains lithium, it can replenish lithium for the membrane and can synergize with aluminum nitride to enhance the ionic conductivity of the membrane.

[0039] 2. The first slurry and the second slurry of the present invention have good compatibility.

[0040] 3. The preparation method of the present invention has high repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is the SEM of the coated membrane prepared in Example 5;

[0042] Figure 2 This is the appearance of the slurry prepared in Example 1 after standing for 24 hours;

[0043] Figure 3This is the appearance of the slurry prepared in Comparative Example 2 after standing for 24 hours. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is further described below with reference to specific embodiments.

[0045] The purchase sources of the medicines involved in the following examples and comparative examples are as follows:

[0046] Lithium carbonate, 99.5% purity;

[0047] Boehmite, 99% purity;

[0048] Titanium dioxide, 99% pure;

[0049] Ammonium dihydrogen phosphate, analytical grade;

[0050] Lithium nitrate, analytical grade;

[0051] Aluminum nitride, purity 99.9%;

[0052] Calcium chloride, 94% purity;

[0053] p-phenylenediamine, purity 99.5%;

[0054] Terephthaloyl chloride, purity 99.5%;

[0055] Pyridine, purity 99.8%;

[0056] N-methylpyrrolidone (NMP), purity 99.5%;

[0057] Electrolyte: The electrolyte includes an electrolyte and a solvent. The electrolyte is LiPF6. The concentration of the electrolyte in the electrolyte is 1.0 M. The solvents are ethyl carbonate, methyl carbonate and dimethyl carbonate. The volume ratio of ethyl carbonate, methyl carbonate and dimethyl carbonate is 1:1:1.

[0058] The models and manufacturers of the equipment involved in the following examples and comparative examples are as follows:

[0059] High-speed planetary ball mill, MSK-SFM-15, Hefei Kejing Material Technology Co., Ltd.;

[0060] Scanning electron microscope, Sigma 300, Carl Zeiss, Germany;

[0061] Japan AsahiSeiko Asahi Seiko air permeability meter, model EH01-551MR;

[0062] Japan Shimadzu stretching machine, model, AGS-X (100N);

[0063] Electrochemical workstation, CHI660E, Shanghai Chenhua Instrument Co., Ltd.

[0064] In the following examples and comparative examples, the ball-to-material ratio of the wet ball milling is 1:7, the wet ball milling uses zirconia balls with a diameter of 5 mm, the orbital speed of the wet ball milling is 200 r / min, and the rotation speed is 600 r / min.

[0065] In the following examples and comparative examples, the base film is a polyethylene film with a thickness of 9 μm.

[0066] In the following examples and comparative examples, water is deionized water.

[0067] Air permeability value: Place the coated membrane on a Japanese AsahiSeiko air permeability tester and test 10 points evenly. The average value of the 10 points is the air permeability value.

[0068] Breakdown voltage: Lay the coated diaphragm flat on the test conductive plate, test 50 breakdown points, and the average value of the 50 breakdown points is the breakdown voltage;

[0069] Thermal shrinkage: Cut the coated membrane into 4 cm × 6 cm pieces and measure the area change of the 4 cm × 6 cm coated membrane in an oven at 180°C for 1 hour to obtain the thermal shrinkage rate.

[0070] Ionic conductivity: Ionic conductivity is measured by immersing the coated membrane in electrolyte at room temperature and 100% RH using the AC impedance method.

[0071] Diaphragm adhesion: Cut the coated diaphragm into a shape of 25mm×60mm, then stick the tape on the coated diaphragm. Use a Japanese Shimadzu stretching machine to tear the tape and the coated diaphragm apart. The force used is the diaphragm adhesion.

[0072] In the tests of air permeability, breakdown voltage, thermal shrinkage, ionic conductivity and membrane adhesion, the coated membrane is one of the coated membranes prepared in Examples 5 to 8 and Comparative Examples 4 to 5.

[0073] Examples 1 to 4

[0074] A method for preparing a slurry comprises: mixing a first slurry and a second slurry, and stirring at 35° C. and 380 r / min for 4 hours until uniform, to obtain the slurry, wherein the first slurry is a mixture of LATP, aluminum nitride, a first substance, and a first solvent; the second slurry comprises poly(p-phenylene terephthalamide) (PPTA), calcium chloride, and a second solvent; the ratio of poly(p-phenylene terephthalamide) (PPTA), LATP, aluminum nitride, and the first substance is X by mass; the first substance is lithium nitrate; the first solvent is N-methylpyrrolidone (NMP); and the second solvent is N-methylpyrrolidone (NMP).

[0075] The ratio of the mass fraction of LATP to the volume fraction of the first solvent is Y, the unit of mass fraction is g, and the unit of volume fraction is mL; the ratio of the first solvent to the second solvent is Z by volume; and the ratio of calcium chloride to lithium aluminum titanium phosphate (LATP) is W by mass.

[0076] The method for preparing the first slurry is: mixing LATP, aluminum nitride, the first substance and the first solvent, and wet-milling for 4 hours until the mixture is uniformly dispersed.

[0077] The method for obtaining LATP is as follows: mixing a lithium source, an aluminum source, a titanium source and ammonium dihydrogen phosphate, wet ball milling for 2.5 hours until uniform, drying in a 70°C oven for 18 hours to obtain a first powder, placing the first powder in a muffle furnace, heating from room temperature to 850°C at a heating rate of 5°C / min and keeping at 850°C for 8 hours to obtain a LATP sintered block, grinding to obtain LATP (powder), wherein, based on the amount of substance, the ratio of lithium in the lithium source, aluminum in the aluminum source, titanium in the titanium source and phosphorus in the ammonium dihydrogen phosphate is 13:3:34:60, the lithium source is lithium carbonate, the aluminum source is boehmite, and the titanium source is titanium dioxide.

[0078] The method for preparing the second slurry is as follows: calcium chloride and a second solvent are mixed at 80° C., stirred until uniform, cooled to 0° C., p-phenylenediamine (PPDA) is added, and then terephthaloyl chloride (TPC) and pyridine are added, and stirred for 30 minutes until uniform to obtain a second slurry, wherein the ratio of the volume fraction of the second solvent, the mass fraction of p-phenylenediamine, the mass fraction of terephthaloyl chloride and the volume fraction of pyridine is 100:4.54:8.12:4.5, the unit of mass fraction is g, and the unit of volume fraction is mL, p-phenylenediamine and terephthaloyl chloride are used to synthesize poly(p-phenylene terephthalamide) (PPTA), and pyridine is used to remove small molecular HCl generated during the synthesis of PPTA.

[0079] Table 1

[0080] Example X Y Z W Example 1 9.6:6:0.6:0.16 30：66.2 13.24：80 0.06:6 Example 2 9.6:6:0.2:0.16 30：68.2 13.64：80 0.06:6 Example 3 10.8:3:0.3:0.08 30：66.2 6.62：90 0.08:3 Example 4 9.6:3.2:0.6:0.16 16：80.2 16.04：80 0.06:3.2

[0081] Comparative Example 1

[0082] A method for preparing a slurry comprises: mixing a third slurry and the second slurry prepared in Example 1, and stirring at 35° C. and 380 r / min for 4 h until uniform, wherein the third slurry is a mixture of LATP, a first substance, and a first solvent, wherein, by mass, the ratio of poly(p-phenylene terephthalamide) (PPTA), LATP, and the first substance is 9.6:6:0.16, by volume, the ratio of the first solvent in the third slurry to the second solvent in the second slurry is 13.84:80, the first substance is lithium nitrate, the first solvent is N-methylpyrrolidone (NMP), and the second solvent is N-methylpyrrolidone (NMP), the ratio of the mass fraction of LATP to the volume fraction of the first solvent in the third slurry is 30:69.2, the unit of mass fraction is g, and the unit of volume fraction is mL.

[0083] The third slurry was prepared by mixing the LATP prepared in Example 1, the first substance, and the first solvent, and wet-milling the mixture for 4 hours until the mixture was uniformly dispersed.

[0084] Comparative Example 2

[0085] A method for preparing a slurry comprises: mixing LATP prepared in Example 1, NMP, and aluminum nitride, and wet ball milling for 4 hours to disperse the LATP and aluminum nitride in the NMP, wherein the ratio of LATP by mass, aluminum nitride by mass, and NMP by volume is 30:3:67, with the units of mass being g and volume being mL. The slurry exhibits significant stratification after being allowed to stand for 3 hours and is unusable.

[0086] Comparative Example 3

[0087] A slurry is the first slurry in Example 1.

[0088] Examples 5 to 8 and Comparative Examples 4 to 5

[0089] A method for preparing a coating membrane, comprising: coating a slurry on a base film, obtaining a coating on the base film, obtaining a coating membrane precursor, extracting the coating membrane precursor, and drying it in an oven at 55°C for 8 minutes for dehydration to obtain a coating membrane, wherein the slurry is one of the slurries prepared in Examples 1 to 4, Comparative Example 1 and Comparative Example 3, as shown in Table 2 (the coating membranes prepared in Examples 5 to 8 are named high-conductivity composite coating membranes), wherein the extraction adopts an extraction liquid, and the extraction process is as follows: the coating membrane precursor is obtained according to The extractants are passed through the extraction liquid with the extractant concentration from high to low, the extractant is N-methylpyrrolidone (NMP), and the extractants with the extractant concentration from high to low are the first extract, the second extract, the third extract and the fourth extract. The first extract, the second extract and the third extract are each a mixture of the extractant and water, and the fourth extract is water. Among them, the concentration of the extractant in the first extract is 80wt%, the concentration of the extractant in the second extract is 50wt%, and the concentration of the extractant in the third extract is 30wt%.

[0090] Table 2

[0091] Coated diaphragm Slurry for preparing coated diaphragms Example 5 Example 1 Example 6 Example 2 Example 7 Example 3 Example 8 Example 4 Comparative Example 4 Comparative Example 1 Comparative Example 5 Comparative Example 3

[0092] The SEM of the coating membrane prepared in Example 5 is as follows: Figure 1 shown.

[0093] During the process of preparing the coated membrane, the coated membrane prepared in Comparative Example 5 showed a slight shedding phenomenon.

[0094] The coated membranes prepared in the examples and comparative examples were subjected to air permeability tests, breakdown voltage tests, thermal shrinkage tests, ionic conductivity tests, and adhesion tests, and the air permeability value, breakdown voltage, thermal shrinkage rate, ionic conductivity, and membrane adhesion were obtained in turn. The results are shown in Table 3.

[0095] Table 3

[0096]

[0097]

[0098] The permeability test shows that the introduction of LATP can reduce the permeability of the coated membrane. At the same time, the introduction of LATP can effectively improve the membrane breakdown voltage and, to a certain extent, synergistically increase the membrane temperature resistance with PPTA, making the membrane have more stable performance. At the same time, the coating membrane also has good ionic conductivity due to the introduction of aluminum nitride. No PPTA was added to the slurry prepared in Comparative Example 3, resulting in a very low membrane adhesion of the coated membrane prepared using the slurry of Comparative Example 3, and even a slight material drop phenomenon. However, this also proves from the side that the introduction of PPTA greatly improves the membrane adhesion. No PPTA was added to the slurry prepared in Comparative Example 3, resulting in a large thermal shrinkage rate of the coated membrane prepared using the slurry of Comparative Example 3, indicating that PPTA can improve the high temperature resistance of the coated membrane.

[0099] The coating membrane prepared in Example 5 was microscopically scanned. From the SEM image, it can be seen that the LATP is distributed relatively evenly and the PPTA fibers are evenly distributed on the surface of the base membrane.

[0100] Depend on Figure 2 and Figure 3 It can be seen that the slurry prepared in Example 1 has no obvious stratification after standing for 24 hours, while the slurry prepared in Comparative Example 2 has obvious stratification after standing for 24 hours. By comparing the two, it can be seen that after the introduction of the first substance (lithium nitrate), LATP has good dispersibility.

[0101] The coating membranes prepared in the examples and comparative examples were subjected to liquid absorption test, liquid climbing test and liquid retention test to obtain the liquid absorption rate, liquid climbing value and liquid retention rate in turn, wherein:

[0102] The liquid absorption rate is obtained by weighing a 5cm×5cm diaphragm m0, soaking it in electrolyte, taking out the electrolyte on the surface and wiping it with non-woven cloth, and weighing m1. The liquid absorption rate of the diaphragm is calculated by (m1-m0) / m0*100%.

[0103] Liquid retention rate: The liquid absorption rate is calculated by soaking a 5cm×5cm diaphragm in electrolyte, taking out the electrolyte on the surface and wiping it with non-woven cloth, weighing m2. After wiping the surface electrolyte, place it in the air for 1 hour and weigh m3. The liquid retention rate of the diaphragm is calculated by (m2-m3) / m2*100%.

[0104] Liquid creepage value: Cut the coated diaphragm into 4cm×15cm pieces, place it vertically and soak the bottom (length 1cm) in the electrolyte for 20min / 40min / 60min. The length of the diaphragm soaked in the electrolyte after soaking for different times is the liquid creepage value of the coated diaphragm.

[0105] The coated membrane is one of the coated membranes prepared in Examples 5 to 8.

[0106] Table 4

[0107]

[0108]

[0109] The results of the liquid absorption, liquid retention and liquid climbing tests show that the slurry of the present invention provides better electrolyte wettability for the diaphragm and can better preserve the electrolyte in the battery.

[0110] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. A high conductivity composite coating diaphragm, characterized in that: include: A base film and a coating applied on the base film, wherein the coating comprises: poly(p-phenylene terephthalamide), lithium aluminum titanium phosphate, aluminum nitride and a first substance, wherein the ratio of poly(p-phenylene terephthalamide), lithium aluminum titanium phosphate, aluminum nitride and the first substance is (7-12):(2-10):(0.15-1):(0.05-0.3) by mass, and the first substance is lithium nitrate.

2. The method for preparing the high-conductivity composite coating diaphragm according to claim 1, characterized in that: include: The slurry is coated on a base film to obtain a coating on the base film to obtain a high-conductivity composite coating membrane precursor. The high-conductivity composite coating membrane precursor is extracted and dehydrated to obtain a high-conductivity composite coating membrane. The slurry includes: poly (p-phenylene terephthalamide), lithium aluminum titanium phosphate, aluminum nitride and a first substance. In the slurry, the ratio of poly (p-phenylene terephthalamide), lithium aluminum titanium phosphate, aluminum nitride and the first substance is (7-12): (2-10): (0.15-1): (0.05-0.3) by mass, and the first substance is lithium nitrate.

3. A slurry for a diaphragm composite coating, characterized in that: include: Poly(p-phenylene terephthalamide), lithium aluminum titanium phosphate, aluminum nitride and the first substance are present in a slurry in a ratio of (7-12): (2-10): (0.15-1): (0.05-0.3) by mass, and the first substance is lithium nitrate.

4. The slurry according to claim 3, characterized in that The slurry also includes: a solvent, which is a single-component solvent and / or a multi-component solvent. The single-component solvent is N-methylpyrrolidone, and the multi-component solvent includes: solvent 1 and solvent 2. Solvent 1 includes: acetonitrile and / or dimethylformamide, and solvent 2 includes: one or a mixture of hexamethylphosphoramide, dimethylacetamide and tetramethylurea.

5. A method for preparing a slurry for a diaphragm composite coating, characterized in that: include: The first slurry and the second slurry are mixed until uniform to obtain a slurry, wherein the first slurry comprises: lithium aluminum titanium phosphate, aluminum nitride, a first substance and a first solvent, and the second slurry comprises: poly(p-phenylene terephthalamide), calcium chloride and a second solvent; wherein, by mass, the ratio of poly(p-phenylene terephthalamide), lithium aluminum titanium phosphate, aluminum nitride and the first substance is (7-12): (2-10): (0.15-1): (0.05-0.3), and the first substance is lithium nitrate. The ratio of the mass fraction of lithium aluminum titanium phosphate to the volume fraction of the first solvent is (16 to 33): (60.8 to 82.5), the unit of mass fraction is g, and the unit of volume fraction is mL; the ratio of the first solvent to the second solvent is (6.08 to 16.5): (70 to 90) by volume; and the ratio of calcium chloride to lithium aluminum titanium phosphate is (0.05 to 0.1): (2 to 8) by mass.

6. The preparation method according to claim 5, characterized in that The first solvent is one or a mixture of N-methylpyrrolidone, acetonitrile and dimethylformamide.

7. The preparation method according to claim 5, characterized in that The second solvent is one or a mixture of hexamethylphosphoramide, dimethylacetamide, N-methylpyrrolidone and tetramethylurea.

8. Use of the high-conductivity composite coating separator as claimed in claim 1 in lithium-ion batteries.

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