Diaphragm coating, lithium battery diaphragm, lithium battery and preparation method

Abstract

The invention relates to the technical field of batteries, and provides a diaphragm coating, a lithium battery diaphragm, a lithium battery and a preparation method. The diaphragm coating comprises pretreated porous ceramic, and the pretreated porous ceramic is porous ceramic which is expanded by alkali and / or modified by a nitrogen-containing heterocyclic compound. According to the technical scheme, the problem of low ionic conductivity of the diaphragm coating in the prior art is solved.

Description

Technical Field

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

[0002] In the precise structure of lithium batteries, the separator undoubtedly plays a crucial role. It is not only a vital physical barrier that strictly maintains the isolation between the positive and negative electrodes, effectively preventing the risk of internal short - circuit in the battery, but also shoulders the important task of ensuring the smooth shuttling of lithium ions, which is the basis for realizing the efficient and stable charge - discharge cycle of the battery. Therefore, improving the ionic conductivity of the separator is of inestimable value and significance for comprehensively optimizing the overall performance of lithium batteries, and this has naturally become a hot focus in the current field of materials science research.

[0003] With the rapid development of modern electronic devices, they have put forward higher and higher requirements for energy density and fast - charging ability. This forces researchers to accelerate the research and development of new separator materials, aiming to make breakthroughs in improving ion transport efficiency and liquid retention ability. To achieve this goal, researchers need to conduct innovative and in - depth explorations in multiple dimensions such as material design, microstructure regulation, and surface modification technology. They are committed to creating separators with higher ionic conduction performance through ingenious material ratio and structure design and fine regulation of the microstructure. At the same time, they are also actively exploring surface modification technology to further improve the ionic conduction efficiency and stability of the separator. These efforts aim to develop separator products with more excellent comprehensive performance and better meet the needs of modern electronic devices, laying a solid foundation for the overall improvement of lithium battery performance. Summary of the Invention

[0004] The present invention provides a separator coating, a lithium battery separator, a lithium battery, and a preparation method thereof, which solves the problem of low ionic conductivity of the separator coating in the related art.

[0005] The technical solution of the present invention is as follows: A separator coating includes pretreated porous ceramics, and the pretreated porous ceramics are porous ceramics that have been alkali - expanded and / or modified with nitrogen - containing heterocyclic compounds.

[0006] As a further technical solution, it further includes at least one of the following features: an adhesive, a dispersant.

[0007] As a further technical solution, when it further includes an adhesive, the adhesive includes one or more of acrylate copolymer, silicone adhesive, polyurethane adhesive, epoxy resin adhesive, polyvinyl alcohol adhesive, and is preferably acrylate copolymer.

[0008] As a further technical solution, when a dispersant is further included, the dispersant includes one or more of ammonium polyacrylate, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium tripolyphosphate, sodium hexametaphosphate, and sodium pyrophosphate, and preferably ammonium polyacrylate.

[0009] As a further technical solution, when the pretreated porous ceramic is a porous ceramic with alkali-expanded pores or a porous ceramic with alkali-expanded pores and modified with a nitrogen-containing heterocyclic compound, the alkali includes strong alkali; When the pretreated porous ceramic is a porous ceramic modified with a nitrogen-containing heterocyclic compound or a porous ceramic with alkali-expanded pores and modified with a nitrogen-containing heterocyclic compound, the nitrogen heterocycle in the nitrogen-containing heterocyclic compound includes one or two of pyrrole nitrogen and pyridine nitrogen.

[0010] In the present invention, the strong alkali is one or more of sodium hydroxide, potassium hydroxide, calcium hydroxide, and barium hydroxide, and preferably one of sodium hydroxide and potassium hydroxide.

[0011] As a further technical solution, when the pretreated porous ceramic is a porous ceramic modified with a nitrogen-containing heterocyclic compound or a porous ceramic with alkali-expanded pores and modified with a nitrogen-containing heterocyclic compound, the nitrogen-containing heterocyclic compound includes one or more of polyvinylpyrrolidone, 4-aminopyridine, 2-methylpyrrole, 2-ethylpyridine, 4-ethylpyridine, 3-ethylpyridine, and N,N-dimethylpyridine, and preferably polyvinylpyrrolidone or N,N-dimethylpyridine.

[0012] As a further technical solution, when the pretreated porous ceramic is a porous ceramic with alkali-expanded pores, the preparation method of the pretreated porous ceramic includes the following steps: Soak the porous ceramic in an alkali solution, wash it until neutral, and dry it to obtain the pretreated porous ceramic; When the pretreated porous ceramic is a porous ceramic modified with a nitrogen-containing heterocyclic compound, the preparation method of the pretreated porous ceramic includes the following steps: Soak the porous ceramic in a nitrogen-containing heterocyclic compound solution and dry it to obtain the pretreated porous ceramic; When the pretreated porous ceramic is a porous ceramic with alkali-expanded pores and modified with a nitrogen-containing heterocyclic compound, the preparation method of the pretreated porous ceramic includes the following steps: S1. Soak the porous ceramic in an alkali solution, wash it until neutral, and dry it to obtain the pre-treated porous ceramic; S2. Soak the pre-treated porous ceramic in a nitrogen-containing heterocyclic compound solution and dry it to obtain the pretreated porous ceramic.

[0013] As a further technical solution, the pretreated porous ceramic is a porous ceramic that is first alkali-expanded and then modified with a nitrogen-containing heterocyclic compound.

[0014] In the present invention, the porous ceramic is pretreated with an alkali. Impurities on the surface and in the pores of the porous ceramic will be removed and it will also undergo a pore-expanding process. The formation of large pore diameters provides convenience for further functional modification. The pore-expanded porous alumina is surface-modified by a solution impregnation method using a nitrogen-containing heterocyclic compound, so that nitrogen-containing functional groups are grafted onto the surface of the pore-expanded porous ceramic, further improving the ionic conductivity of the separator coating, reducing the thermal shrinkage rate of the separator, and improving the heat resistance of the separator.

[0015] As a further technical solution, the porous ceramic includes one or several of porous alumina, porous titanium dioxide, porous molybdenum disulfide, porous boehmite, porous magnesium nitride, porous barium sulfate, porous barium titanate, porous aluminum sulfate, porous aluminum nitride, and porous magnesium hydroxide, preferably porous alumina.

[0016] As a further technical solution, the D50 of the porous ceramic is 0.8 - 1.0 μm, the D90 is 1.5 - 3.0 μm, the specific surface area is 10 - 15 m 2 / g, and the average pore diameter is 11.62 - 12.53 nm.

[0017] The present invention also provides a lithium battery separator, including a base film and the separator coating disposed on at least one side of the base film.

[0018] The lithium battery separator provided by the present invention has excellent wetting performance and superior ion transport efficiency. Since the pretreated porous ceramic is used as the coating material of the separator, this coating provides an extremely rich and efficient adsorption and storage environment for the electrolyte by virtue of its unique and highly refined microporous structure. These micropores are like tiny liquid reservoirs, which not only greatly enhance the adsorption capacity and retention effect of the electrolyte on the separator surface, but also significantly shorten the transport path of lithium ions (Li + ) shuttling inside the separator through optimizing the pore distribution.

[0019] The design of using the pretreated porous ceramic as the separator coating material brings two significant advantages: on the one hand, it greatly improves the ionic conductivity of the separator, enabling lithium ions to pass through the separator more quickly and efficiently, thus accelerating the charge and discharge process of the battery; on the other hand, by shortening the ion transport path and optimizing the electrolyte distribution, it effectively reduces the internal resistance of the lithium ion battery, reduces energy loss, and further enables the battery to release a higher power density. This improvement not only meets the growing demand of modern electronic devices for high-performance batteries, but also injects new vitality into the continuous progress of battery technology and the improvement of the performance of electronic products.

[0020] As a further technical solution, the thickness of the separator coating is 2 - 5 μm.

[0021] The present invention also provides a method for preparing a lithium battery separator, which includes the following steps: after uniformly mixing the raw materials of the separator coating, coating them on at least one side of the base film and drying to obtain the lithium battery separator.

[0022] As a further technical solution, the raw materials include the following components in parts by mass: 10 - 30 parts of pretreated porous ceramics, 1 - 5 parts of adhesive solution, 0 - 0.5 parts of dispersant, and 40 - 90 parts of water.

[0023] As a further technical solution, it includes the following steps: A1. Mix the dispersant, water, and pretreated porous ceramics to obtain a mixture; A2. Add the adhesive solution to the mixture and mix to obtain a slurry; A3. Coat the slurry on at least one side of the base film and dry to obtain the lithium battery separator.

[0024] As a further technical solution, in step A1, during the mixing, the self - rotation speed is 1000 - 2000 r / min, the revolution speed is 40 - 60 r / min, and the mixing time is 20 - 40 min.

[0025] As a further technical solution, in step A2, during the mixing, the pressure is 0.06 - 0.08 kPa, the self - rotation speed is 1000 - 2000 r / min, the revolution speed is 40 - 60 r / min, and the mixing time is 20 - 40 min.

[0026] As a further technical solution, the mixing in steps A1 and A2 is independently carried out in a double - planetary mixer XFZH - 30L.

[0027] As a further technical solution, the coating method is coating with a coater, and the coating speed is 10 - 20 m / min.

[0028] As a further technical solution, the drying temperature is 50 - 60 °C and the time is 1 - 2 min.

[0029] The present invention also provides a lithium battery, including the separator coating described above, or the lithium battery separator described above, or the lithium battery separator obtained by the preparation method described above.

[0030] The working principle and beneficial effects of the present invention are as follows: In the present invention, the separator coating comprises porous ceramics which are alkali-enlarged and / or modified with nitrogen-containing heterocyclic compounds. In an alkaline medium, impurities on the surface and in the pores of the porous ceramics are removed and a pore-enlarging process will also occur, in which the thinner parts of the pore walls are etched away, making the pore diameter of the porous ceramics larger. The large pore diameter not only helps to improve wettability but also helps to form a more stable electrolyte channel, reducing the lithium ion transport resistance, thereby improving the ionic conductivity. In addition, after modifying the porous ceramics with nitrogen-containing heterocyclic compounds, nitrogen-containing functional groups are grafted onto the surface of the porous ceramics. The presence of the nitrogen-containing functional groups enables the porous ceramics to exhibit better interfacial stability when in contact with the electrolyte, helps to reduce the interfacial resistance, improves the transport efficiency of lithium ions at the interface, and thus improves the ionic conductivity of the coating. Detailed Embodiments

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0032] The sources of the raw materials in the following examples and comparative examples are as follows: Porous alumina powder: Suzhou Jinyi New Materials Technology Co., Ltd.; Acrylate copolymer solution with a solid content of 20%: Baoding Lucky Imaging Materials Technology Co., Ltd.; Ammonium polyacrylate: Yueyang Kaimen Waterborne Additives Co., Ltd.; The thickness of the PE-based film is 7 μm, the air permeability is 115 Sec / 100 ml, and the surface density is 4.5 g / m 2 .

[0033] Example 1 S1. Preparation of pretreated porous ceramics: Take 1000 g of porous alumina (D50 = 0.889 μm, D90 = 1.693 μm, specific surface area: 13.45 m 2 / g, average pore diameter 11.62 nm), soak it in 20 wt% sodium hydroxide solution for 12 h, wash it with water until neutral, dry it at 60 °C for 12 h, and grind it to obtain pretreated porous ceramics (D50 = 0.885 μm, D90 = 1.690 μm, specific surface area: 14.26 m 2 / g, average pore diameter 13.75 nm); S2. Preparation of Coating Slurry: 0.5 part of ammonium polyacrylate, 74.5 parts of pure water, and 20 parts of pretreated porous ceramics were blended in a double planetary mixer XFZH-30L for 40 min, with a self-rotation speed of 2000 r / min and a revolution speed of 60 r / min. Then 5 parts of acrylate copolymer solution were added, and the mixture was further mixed in the double planetary mixer XFZH-30L with ultrasonic oscillation function under vacuum and high-speed dispersion for 40 min, with an environment of 0.06 kPa, a self-rotation speed of 2000 r / min, a revolution speed of 60 r / min, and an ultrasonic frequency of 5 kHz to obtain the coating slurry; S3. Preparation of Battery Separator: The PE film was placed on a coater equipped with the coating slurry for single-sided coating, and the coating speed was controlled at 20 m / min. Then it was drawn into a drying device by a traction roller and dried at 60 °C for 1 min to obtain a battery separator with a coating thickness of 3 μm.

[0034] Example 2 S1. Preparation of Pretreated Porous Ceramics: 1000 g of porous alumina (D50 = 0.889 μm, D90 = 1.693 μm, specific surface area: 13.45 m 2 / g, average pore diameter 11.62 nm) was soaked in a 20 wt% polyvinylpyrrolidone solution for 4 h, then dried at 60 °C for 6 h and ground to obtain pretreated porous ceramics (D50 = 0.870 μm, D90 = 1.685 μm, specific surface area: 15.75 m 2 / g, average pore diameter 14.02 nm); S2. Preparation of Coating Slurry: 0.5 part of ammonium polyacrylate, 74.5 parts of pure water, and 20 parts of pretreated porous ceramics were blended in a double planetary mixer XFZH-30L for 40 min, with a self-rotation speed of 2000 r / min and a revolution speed of 60 r / min. Then 5 parts of acrylate copolymer solution were added, and the mixture was further mixed in the double planetary mixer XFZH-30L with ultrasonic oscillation function under vacuum and high-speed dispersion for 40 min, with an environment of 0.06 kPa, a self-rotation speed of 2000 r / min, a revolution speed of 60 r / min, and an ultrasonic frequency of 5 kHz to obtain the coating slurry; S3. Preparation of Battery Separator: The PE film was placed on a coater equipped with the coating slurry for single-sided coating, and the coating speed was controlled at 20 m / min. Then it was drawn into a drying device by a traction roller and dried at 60 °C for 1 min to obtain a battery separator with a coating thickness of 3 μm.

[0035] Example 3 S1. Preparation of Pretreated Porous Ceramics: 1000 g of porous alumina (D50 = 0.889 μm, D90 = 1.693 μm, specific surface area: 13.45 m 2 / g, average pore size 11.62nm) was soaked in 20wt% sodium hydroxide solution for 12h, washed with water until neutral, dried at 60℃ for 12h, and ground to obtain pre-treated porous ceramics (D50=0.885μm, D90=1.690μm, specific surface area: 14.26m 2 / g, average pore size 13.75nm); 1000g of pretreated porous ceramics were soaked in 20wt% polyvinyl pyrrolidone solution for 4h, dried at 60℃ for 6h, and ground to obtain pretreated porous ceramics (D50=0.875μm, D90=1.683μm, specific surface area: 15.88m 2 / g, average pore size 13.75nm); S2. Preparation of coating slurry: 0.5 parts of ammonium polyacrylate, 74.5 parts of pure water, and 20 parts of pretreated porous ceramics were mixed in a double planetary mixer XFZH-30L for 40 minutes, wherein the rotation speed was 2000 r / min and the revolution speed was 60 r / min, 5 parts of acrylate copolymer solution were added, and mixed in a vacuum, high-speed dispersed double planetary mixer XFZH-30L with ultrasonic oscillation function for 40 minutes, wherein the environment was 0.06 kPa, the rotation speed was 2000 r / min, the revolution speed was 60 r / min, and the ultrasonic frequency was 5 kHz, to obtain a coating slurry; S3. Preparation of battery separator: Place the PE film on a coating machine filled with coating slurry for single-sided coating, control the coating speed at 20 m / min, and pull it into a drying device through a traction roller and dry it at 60°C for 1 min to obtain a battery separator with a coating thickness of 3 μm.

[0036] Example 4 S1. Preparation of pre-treated porous ceramics: 1000 g of porous alumina (D50 = 0.896 μm, D90 = 1.763 μm, specific surface area: 12.99 m 2 / g, average pore size 11.98nm) was soaked in 20wt% potassium hydroxide solution for 12h, washed with water until neutral, dried at 60℃ for 12h, and ground to obtain pre-treated porous ceramics (D50=0.895μm, D90=1.760μm, specific surface area: 15.36m 2 / g, average pore size 14.35nm); 1000g of pretreated porous ceramics were soaked in 20wt% polyvinyl pyrrolidone solution for 4h, dried at 60℃ for 6h, and ground to obtain pretreated porous ceramics (D50=0.885μm, D90=1.756μm, specific surface area: 18.36m 2 / g, average pore size 16.98nm); S2. Preparation of Coating Slurry: 0.5 part of ammonium polyacrylate, 74.5 parts of pure water, and 20 parts of pretreated porous ceramics were blended in a double planetary mixer XFZH-30L for 40 min, with a self-rotation speed of 2000 r / min and a revolution speed of 60 r / min. Then 5 parts of acrylate copolymer solution were added, and the mixture was further mixed in the double planetary mixer XFZH-30L with ultrasonic oscillation function, vacuum, and high-speed dispersion for 40 min, with an environment of 0.06 kPa, a self-rotation speed of 2000 r / min, a revolution speed of 60 r / min, and an ultrasonic frequency of 5 kHz to obtain the coating slurry; S3. Preparation of Battery Separator: The PE membrane was placed on a coater equipped with the coating slurry for single-sided coating, and the coating speed was controlled at 20 m / min. After being pulled by the traction roller, it was fed into a drying device and dried at 60 °C for 1 min to obtain a battery separator with a coating thickness of 3 μm.

[0037] Example 5 S1. Preparation of Pretreated Porous Ceramics: 1000 g of porous alumina (D50 = 0.875 μm, D90 = 1.566 μm, specific surface area: 14.95 m 2 / g, average pore diameter 13.78 nm) was soaked in 20 wt% sodium hydroxide solution for 12 h, then washed with water until neutral, dried at 60 °C for 12 h, and ground to obtain the pretreated porous ceramics (D50 = 0.869 μm, D90 = 1.556 μm, specific surface area: 16.45 m 2 / g, average pore diameter 15.61 nm); 1000 g of the pretreated porous ceramics were soaked in 20 wt% polyvinylpyrrolidone solution for 4 h, then dried at 60 °C for 6 h, and ground to obtain the pretreated porous ceramics (D50 = 0.861 μm, D90 = 1.552 μm, specific surface area: 17.45 m 2 / g, average pore diameter 17.99 nm); S2. Preparation of Coating Slurry: 0.5 part of ammonium polyacrylate, 74.5 parts of pure water, and 20 parts of pretreated porous ceramics were blended in a double planetary mixer XFZH-30L for 40 min, with a self-rotation speed of 2000 r / min and a revolution speed of 60 r / min. Then 5 parts of acrylate copolymer solution were added, and the mixture was further mixed in the double planetary mixer XFZH-30L with ultrasonic oscillation function, vacuum, and high-speed dispersion for 40 min, with an environment of 0.06 kPa, a self-rotation speed of 2000 r / min, a revolution speed of 60 r / min, and an ultrasonic frequency of 5 kHz to obtain the coating slurry; S3. Preparation of Battery Separator: The PE membrane was placed on a coater equipped with the coating slurry for single-sided coating, and the coating speed was controlled at 20 m / min. After being pulled by the traction roller, it was fed into a drying device and dried at 60 °C for 1 min to obtain a battery separator with a coating thickness of 3 μm.

[0038] Example 6 S1. Preparation of pre-treated porous ceramics: 1000 g of porous alumina (D50 = 0.889 μm, D90 = 1.693 μm, specific surface area: 13.45 m 2 / g, average pore size 11.62nm) was soaked in 20wt% sodium hydroxide solution for 12h, washed with water until neutral, dried at 60℃ for 12h, and ground to obtain pre-treated porous ceramics (D50=0.885μm, D90=1.690μm, specific surface area: 14.26m 2 / g, average pore size 13.75nm); 1000g of pretreated porous ceramics were soaked in 20wt% N,N-dimethylpyridine solution for 4h, dried at 60℃ for 6h, and ground to obtain pretreated porous ceramics (D50=0.875μm, D90=1.683μm, specific surface area: 15.88m 2 / g, average pore size 13.75nm); S2. Preparation of coating slurry: 45 parts of pure water and 10 parts of pretreated porous ceramics were mixed in a double planetary mixer XFZH-30L for 20 minutes, wherein the rotation speed was 1000 r / min and the revolution speed was 40 r / min, 1 part of acrylate copolymer solution was added, and mixed in a vacuum, high-speed dispersed double planetary mixer XFZH-30L with ultrasonic oscillation function for 20 minutes, wherein the environment was 0.08 kPa, the rotation speed was 1000 r / min, the revolution speed was 40 r / min, and the ultrasonic frequency was 5 kHz, to obtain a coating slurry; S3. Preparation of battery separator: Place the PE film on a coating machine filled with coating slurry for double-sided coating, control the coating speed to 10 m / min, and pull it into a drying device through a traction roller and dry it at 50°C for 2 minutes to obtain a battery separator with a coating thickness of 3 μm.

[0039] Comparative Example 1 S1. Preparation of coating slurry: 0.5 parts of ammonium polyacrylate, 74.5 parts of pure water, porous alumina (D50 = 0.889 μm, D90 = 1.693 μm, specific surface area: 13.45 m 2 / g, average pore size 11.62nm) 20 parts in a double planetary mixer XFZH-30L equipment, blended for 40 minutes, wherein the rotation speed is 2000r / min, the revolution speed is 60r / min, 5 parts of the acrylate copolymer solution are added, and mixed for 40 minutes in a vacuum, high-speed dispersion double planetary mixer XFZH-30L equipment with ultrasonic oscillation function, wherein the environment is 0.06kPa, the rotation speed is 2000r / min, the revolution speed is 60r / min, and the ultrasonic frequency is 5kHz, to obtain a coating slurry; S2. Preparation of battery separator: Place the PE film on a coater equipped with coating slurry, control the coating speed at 20 m / min, and pull it into a drying device by a traction roller and dry it at 60 °C for 1 min to obtain a battery separator with a coating thickness of 3 μm.

[0040] Comparative Example 2 S1. Preparation of pretreated porous ceramic: Take 1000 g of porous alumina (D50 = 0.889 μm, D90 = 1.693 μm, specific surface area: 13.45 m 2 / g, average pore diameter 11.62 nm), soak it in 20 wt% sulfuric acid solution for 12 h, wash it with water until neutral, dry it at 60 °C for 12 h, and grind it to obtain pretreated porous ceramic (D50 = 0.876 μm, D90 = 1.687 μm, specific surface area: 14.95 m 2 / g, average pore diameter 12.22 nm); S2. Preparation of coating slurry: Blend 0.5 part of ammonium polyacrylate, 74.5 parts of pure water, and 20 parts of pretreated porous ceramic in a double planetary mixer XFZH-30L device for 40 min, with a rotation speed of 2000 r / min and a revolution speed of 60 r / min. Add 5 parts of acrylate copolymer solution and mix it in a double planetary mixer XFZH-30L device with vacuum and high-speed dispersion and ultrasonic oscillation function for 40 min, with an environment of 0.06 kPa, a rotation speed of 2000 r / min, a revolution speed of 60 r / min, and an ultrasonic frequency of 5 kHz to obtain coating slurry; S3. Preparation of battery separator: Place the PE film on a coater equipped with coating slurry, control the coating speed at 20 m / min, and pull it into a drying device by a traction roller and dry it at 60 °C for 1 min to obtain a battery separator with a coating thickness of 3 μm.

[0041] Performance test: (1) Test the thickness, air permeability, shrinkage rate (130 °C, 1 h), and ionic conductivity according to the method in GB / T 36363-2018; (2) Test of liquid absorption rate and liquid retention rate: Cut 3 diaphragm specimens with an area of 50 mm × 50 mm, weigh them, and record as m 1 , soak the weighed diaphragm in the electrolyte for 30 min; lay a layer of clean industrial wiping paper (with an area larger than 150 mm × 150 mm) on a flat table, take out the sample, quickly place it on the industrial wiping paper, and gently press and wipe the free electrolyte on the surface of the diaphragm with another piece of industrial wiping paper until no granular electrolyte can be seen with the naked eye, weigh the dried sample as m 2 , then leave it for 1 h and weigh it, record as m 3。

[0042] The liquid absorption rate and liquid retention rate of the separator are calculated according to the following formulas respectively: Liquid absorption rate = [(m 2 - m 1 ) / m 1 × 100%; Liquid retention rate = [(m 3 - m 1 ) / m 1 × 100%; In the formulas: m 1 is the weight of the cut separator, in grams (g); m 2 is the weight of the soaked separator, in grams (g); m 3 is the weight of the separator after being left for 1 hour after soaking, in grams (g); Take the average value of 3 parallel sample tests, and round the calculation result to one decimal place; (3) Areal density test: Use the conventional weighing method.

[0043] The test results are shown in Table 1.

[0044] Table 1 Test Results of Battery Separator Performance

[0045] It can be seen from Table 1 that compared with Comparative Examples 1-2, the ionic conductivity of the battery separators prepared in Examples 1-6 is above 1.2788 mS / cm, indicating that the porous ceramics in the coating can improve the ionic conductivity of the battery separator after alkali pore expansion and / or modification with nitrogen-containing heterocyclic compounds.

[0046] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A diaphragm coating, characterized in that: The invention comprises a pretreated porous ceramic, wherein the pretreated porous ceramic is a porous ceramic which is expanded with alkali and / or modified with a nitrogen-containing heterocyclic compound.

2. A diaphragm coating according to claim 1, characterized in that: It also includes at least one of the following features: an adhesive and a dispersant.

3. A diaphragm coating according to claim 1, characterized in that: When the pretreated porous ceramic is a porous ceramic expanded by alkali, or a porous ceramic expanded by alkali and modified by a nitrogen-containing heterocyclic compound, the alkali comprises a strong alkali; When the pretreated porous ceramic is a porous ceramic modified by a nitrogen-containing heterocyclic compound, or a porous ceramic expanded by alkali and modified by a nitrogen-containing heterocyclic compound, the nitrogen heterocycle in the nitrogen-containing heterocyclic compound includes one or both of pyrrole nitrogen and pyridinic nitrogen.

4. A diaphragm coating according to claim 3, characterized in that: When the pretreated porous ceramic is a porous ceramic modified with a nitrogen-containing heterocyclic compound, or a porous ceramic expanded by alkali and modified with a nitrogen-containing heterocyclic compound, the nitrogen-containing heterocyclic compound includes one or more of polyvinylpyrrolidone, 4-aminopyridine, 2-methylpyrrole, 2-ethylpyridine, 4-ethylpyridine, 3-ethylpyridine, and N,N-dimethylpyridine.

5. A diaphragm coating according to claim 1, characterized in that: When the pretreated porous ceramic is an alkali-expanded porous ceramic, the preparation method of the pretreated porous ceramic comprises the following steps: The porous ceramic is immersed in an alkaline solution, washed to neutrality, and dried to obtain a pretreated porous ceramic; When the pretreated porous ceramic is a porous ceramic modified by a nitrogen-containing heterocyclic compound, the preparation method of the pretreated porous ceramic comprises the following steps: soaking the porous ceramic in a nitrogen-containing heterocyclic compound solution and drying to obtain a pretreated porous ceramic; When the pretreated porous ceramic is a porous ceramic that has been expanded with alkali and modified with a nitrogen-containing heterocyclic compound, the method for preparing the pretreated porous ceramic comprises the following steps: S1, soaking the porous ceramic in an alkaline solution, washing until neutral, and drying to obtain a pre-treated porous ceramic; S2, immersing the pretreated porous ceramic in a nitrogen-containing heterocyclic compound solution, and drying to obtain the pretreated porous ceramic.

6. A diaphragm coating according to claim 1, characterized in that: The porous ceramic includes one or more of porous alumina, porous titanium dioxide, porous molybdenum disulfide, porous boehmite, porous magnesium nitride, porous barium sulfate, porous barium titanate, porous aluminum sulfate, porous aluminum nitride, and porous magnesium hydroxide.

7. A lithium battery separator, characterized in that: The invention comprises a base film and a diaphragm coating according to any one of claims 1 to 6 arranged on at least one side of the base film.

8. A lithium battery separator according to claim 7, characterized in that: The thickness of the diaphragm coating is 2-5 μm.

9. The method for preparing a lithium battery separator according to claim 7 or 8, characterized in that: The method comprises the following steps: mixing raw materials of the diaphragm coating evenly, coating the raw materials on at least one side of the base film, and drying the base film to obtain the lithium battery diaphragm.

10. A lithium battery, characterized in that: It comprises the diaphragm coating according to any one of claims 1 to 6, the lithium battery diaphragm according to any one of claims 7 to 8, or the lithium battery diaphragm obtained by the preparation method according to claim 9.

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