A lithium supplement coating, a preparation method thereof, a diaphragm and a battery

Abstract

The application discloses a lithium supplement coating and a preparation method thereof, a diaphragm and a battery, and belongs to the technical field of battery materials. The lithium supplement coating contains acid-modified sepiolite fiber composites, and the acid-modified sepiolite fiber composites comprise carboxylated sepiolite fibers and metal lithium organic framework materials grafted on the carboxylated sepiolite fibers. The Si-OH bonds in the sepiolite fibers and the multi-cavity network structure formed by the interlaced fibers have strong adsorption, and the carboxylated sepiolite fibers have a large specific surface area, so that more active sites can be provided for the metal lithium organic framework materials, and good electrolyte wetting performance is achieved. The sepiolite fibers have unique water loss, so that the flame retardant performance of the battery diaphragm can be improved, and the safety of the lithium ion battery can be improved. The metal lithium organic framework material can be used as a lithium supplement agent, so that the irreversible loss of lithium can be reduced, and the cycle life of the battery can be prolonged. The diaphragm containing the lithium supplement coating has a good application prospect in the battery.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a lithium-replenishing coating and its preparation method, a separator, and a battery. Background Technology

[0002] With the increasing demand for lithium-ion batteries, enhancing battery safety and improving cycle life have become hot topics in the research and development of power battery manufacturers. Currently, porous polyolefin materials are the most commonly used materials for commercially available separators in the lithium-ion battery market, with polypropylene (PP) and polyethylene (PE) being the most widely used due to their high mechanical strength and good chemical stability. However, the hydrophobicity of polyolefin materials results in poor electrolyte wettability of porous polyolefin separators, limiting the battery's discharge capacity, especially under high-temperature and high-pressure operating conditions. Furthermore, during the initial charge and discharge of a lithium-ion battery, a solid electrolyte interphase (SEI) film forms at the interface between the negative electrode and the electrolyte. While the SEI film is a good conductor of lithium ions, its formation consumes some lithium ions from the positive electrode material, leading to insufficient lithium ion supply and reduced battery capacity. During battery cycling, the insertion and extraction of lithium ions repeatedly consume the SEI film, resulting in varying degrees of irreversible lithium consumption within both the positive and negative electrodes, thus reducing the battery's cycle life. In addition, as one of the most important safety components in a battery, the thermal stability and flame retardancy of the lithium-ion battery separator are also important performance indicators. Developing separators with high stability and flame retardancy is beneficial to preventing short circuits and thermal runaway explosions of batteries at high temperatures.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a lithium-replenishing coating and its preparation method, a separator, and a battery to solve or improve the above-mentioned technical problems.

[0005] This invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a lithium replenishing coating containing an acid-modified sepiolite fiber composite material, the acid-modified sepiolite fiber composite material including carboxylated sepiolite fibers and a lithium metal organic framework material grafted onto the carboxylated sepiolite fibers.

[0007] In an optional embodiment, the lithium-filled coating has at least one of the following characteristics:

[0008] Feature 1: The lithium replenishing coating contains 1% to 50% acid-modified sepiolite fiber composite material by weight percentage;

[0009] Feature 2: The weight ratio of carboxylated sepiolite fiber to lithium metal organic framework material is 10:1 to 5:1;

[0010] Feature 3: The length of the sepiolite fibers in the carboxylated sepiolite fibers is 0.5μm to 50μm, preferably 5μm to 25μm, and more preferably 10μm to 15μm;

[0011] Feature 4: The aspect ratio of the sepiolite fibers in the carboxylated sepiolite fibers is 10:1 to 100:1, preferably 15:1 to 90:1, and more preferably 20:1 to 80:1.

[0012] In an optional embodiment, the lithium replenishment coating also contains ceramic materials;

[0013] Ceramic materials have at least one of the following characteristics:

[0014] Feature 5: The weight ratio of ceramic material to acid-modified sepiolite fiber composite material is (19:1) to (1:1);

[0015] Feature 6: The ceramic material includes at least one of alumina, boehmite, silicon dioxide, titanium dioxide, magnesium hydroxide, aluminum hydroxide, barium titanate, and zinc oxide;

[0016] Feature 7: D of ceramic materials 50 The wavelength range is 50nm to 5μm, preferably 80nm to 4.5μm, and more preferably 100nm to 3.5μm.

[0017] In an optional embodiment, the lithium-replenishing coating also contains additives;

[0018] Additives include at least one of dispersants, adhesives, wetting agents, and thickeners.

[0019] In an optional embodiment, the amount of dispersant contained in the lithium replenishing coating is 0.05 to 5 parts by weight; and / or, the amount of adhesive contained in the lithium replenishing coating is 0.5 to 10 parts; and / or, the amount of wetting agent contained in the lithium replenishing coating is 0.01 to 0.66 parts; and / or, the amount of thickener contained in the lithium replenishing coating is 0.5 to 5 parts.

[0020] In an optional embodiment, the dispersant includes at least one of sodium polyacrylate, ammonium polyacrylate, sodium hexametaphosphate, polyvinyl alcohol, and polyethylene glycol;

[0021] And / or, the adhesive includes at least one of polyacrylamide, polyvinylamide, polyvinylpyrrolidone, polymethyl methacrylate, polycarboxylic acid, polyacrylic acid, polyurethane acrylate, polyacrylate copolymer emulsion, cis-butadiene rubber, styrene-butadiene rubber and polyurethane;

[0022] And / or, the wetting agent includes at least one of polyether-modified silicone, polyol and fatty alcohol ether;

[0023] And / or, the thickener includes at least one of methylcellulose, hydroxypropyl methylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, hydroxyethyl methylcellulose, and hydroxypropylcellulose.

[0024] In a second aspect, the present invention provides a method for preparing a lithium-replenishing coating as described in any of the foregoing embodiments, comprising the following steps: coating a slurry containing an acid-modified sepiolite fiber composite material onto the surface of at least one side of a base film, and drying it.

[0025] In an optional embodiment, the method for preparing the acid-modified sepiolite fiber composite material includes grafting a metal-organic framework material onto carboxylated sepiolite fibers.

[0026] In an optional embodiment, the preparation of acid-modified sepiolite fiber composite material includes: dissolving carboxylated sepiolite fiber and lithium metal organic framework preparation raw materials in a solvent, separating the solid and liquid, and drying the solid.

[0027] In an optional implementation, the raw materials for preparing the lithium metal organic framework include a lithium source and organic ligands.

[0028] In optional embodiments, the lithium source includes at least one of LiClO4·3H2O, Li2CO3, and LiOH; preferably, the lithium source includes LiClO4·3H2O.

[0029] In an optional embodiment, the organic ligand includes 2-methylimidazole. 、 At least one of N-ethylimidazole, N-propylimidazole, 4-nitroimidazole, and benzimidazole; preferably, the organic ligand includes 2-methylimidazole.

[0030] In an optional embodiment, the raw materials for preparing the lithium metal organic framework include LiClO4·3H2O and 2-methylimidazole.

[0031] In an optional embodiment, the preparation of carboxylated sepiolite fiber includes: acidifying sepiolite fiber to obtain acid-modified sepiolite fiber; and grafting carboxylic acid groups onto the acid-modified sepiolite fiber.

[0032] In an optional embodiment, the preparation of acid-modified sepiolite fiber includes: acid activation treatment of sepiolite fiber with acid solution; followed by washing with water and drying.

[0033] In an optional embodiment, the acid activation treatment includes at least one of the following features:

[0034] Feature 8: The acid solution includes at least one of hydrochloric acid, nitric acid, and sulfuric acid;

[0035] Feature 9: The solid-liquid ratio of sepiolite fiber to acid solution is 1g:10mL to 10g:10mL;

[0036] Feature 10: The acid activation treatment temperature is 70℃~90℃;

[0037] Feature 11: The acid activation treatment time is 24h to 48h;

[0038] Feature 12: Before acid activation treatment, the sepiolite fibers are first washed with water to remove impurities.

[0039] In an optional embodiment, grafting carboxylic acid groups includes immersing acid-modified sepiolite fibers in a coupling agent solution, followed by immersion in a carboxylic acid group providing solution.

[0040] In an optional embodiment, the grafted carboxylic acid group includes at least one of the following characteristics:

[0041] Feature 13: The coupling agent solution includes at least one of silane coupling agent solution, phthalate coupling agent solution and aluminate coupling agent solution, preferably including silane coupling agent solution;

[0042] Feature 14: The carboxylic acid group providing solution includes at least one of terephthalic acid solution, formic acid solution, acetic acid solution, oxalic acid solution and succinic acid solution, preferably including terephthalic acid solution;

[0043] Feature 15: The soaking time in the silane coupling agent solution is 4h to 8h;

[0044] Feature 16: The soaking time in the carboxylic acid group-providing solution is 4h to 8h.

[0045] Thirdly, the present invention provides a separator comprising a base membrane and a coating disposed on at least one side surface of the base membrane, wherein the coating is a lithium-filling coating of any of the foregoing embodiments.

[0046] In an optional embodiment, the diaphragm includes at least one of the following features:

[0047] Feature 17: The thickness of the diaphragm is 5.5 μm to 25.5 μm, preferably 7.5 μm to 23.5 μm, and more preferably 9.5 μm to 20.5 μm;

[0048] Feature 18: The thickness of the base film is 5μm to 25μm, preferably 7μm to 23μm, and more preferably 9μm to 20μm;

[0049] Feature 19: The thickness of the lithium replenishment coating is 0.5μm to 10μm, preferably 0.5μm to 8μm, and more preferably 0.5μm to 5μm;

[0050] Feature 20: The base membrane includes at least one of polyolefin membrane, cellulose membrane, polyester membrane, nanofiber nonwoven membrane and aramid membrane.

[0051] Fourthly, the present invention provides a battery comprising a positive electrode, a negative electrode, and a separator as described in the foregoing embodiments, wherein the positive electrode and the negative electrode are separated by the separator.

[0052] The beneficial effects of this invention include:

[0053] The lithium-replenishing coating provided by this invention contains an acid-modified sepiolite fiber composite material, which includes carboxylated sepiolite fibers and a lithium metal organic framework grafted onto the carboxylated sepiolite fibers. The Si-OH bonds in the sepiolite fibers and the porous network structure formed by the interlacing of fibers exhibit strong adsorption properties. Furthermore, the carboxylated sepiolite fibers have a large specific surface area, providing more active sites for the lithium metal organic framework material. This results in better electrolyte wetting performance when combined with ceramic materials compared to coatings prepared solely from ceramic materials. Additionally, the sepiolite fibers possess unique water-loss properties, which can enhance the flame-retardant properties of the battery separator and improve the safety of lithium-ion batteries. Moreover, the lithium metal organic framework material in the composite material can act as a lithium replenishing agent, slowly releasing lithium ions during charge and discharge, reducing irreversible lithium loss, accelerating the lithium-ion transport rate, improving the problem of insufficient lithium-ion content in the positive electrode after the formation of the SEI film in the negative electrode material, and extending the cycle life of the battery.

[0054] The separator with the above-mentioned lithium replenishment coating has good electrolyte wetting properties and flame retardant properties, which are beneficial to improving battery safety performance, first charge and discharge efficiency and cycle life. Attached Figure Description

[0055] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 This is a schematic diagram of the structure of the diaphragm provided by the present invention;

[0057] Figure 2 SEM image of acid-modified foresharpite fiber provided by this invention;

[0058] Figure 3 SEM image of acid-modified sepiolite fiber provided by the present invention.

[0059] Icons: 100 - Lithium-replenishing coating; 110 - Acid-modified sepiolite fiber composite material; 111 - Metal-organic framework; 112 - Carboxylated sepiolite fiber; 120 - Ceramic material; 200 - Base film. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0061] The following provides a detailed description of the lithium replenishment coating, its preparation method, the separator, and the battery provided by this invention.

[0062] This invention provides a lithium replenishment coating 100, such as... Figure 1 As shown, the lithium-replenishing coating 100 contains an acid-modified sepiolite fiber composite material 110, which includes carboxylated sepiolite fibers 112 and a lithium metal organic framework material grafted onto the carboxylated sepiolite fibers 112.

[0063] Among them, the Si-OH bonds in sepiolite fibers and the porous network structure formed by fiber interlacing have strong adsorption properties. During high-temperature heating, sepiolite fibers gradually release zeolite water and Mg-ion-coordinated water from the pores, which is beneficial to improving the flame retardancy of the battery. In addition, the carboxyl-modified sepiolite fibers have a large specific surface area, which can provide more active sites for lithium metal organic framework materials (denoted as Li-MOF), and can have better electrolyte wetting performance than single ceramic particle coatings. Furthermore, sepiolite fibers have unique water loss properties, which can enhance the flame retardancy of the battery separator and improve the safety of lithium-ion batteries. In addition, the lithium metal organic framework material in the composite material can act as a lithium replenishing agent, slowly releasing lithium ions during charging and discharging, accelerating the lithium ion transport rate, improving the problem of insufficient positive electrode lithium ion content after the formation of SEI film in the negative electrode material, and extending the cycle life of the battery.

[0064] The aforementioned lithium-replenishing coating 100 has good electrolyte wetting and flame-retardant properties, and can improve the first charge-discharge efficiency of the battery and improve the cycle life of the battery.

[0065] In some alternative embodiments, the lithium replenishing coating 100 contains 1% to 50% (e.g., 1%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50%) of acid-modified sepiolite fiber composite material 110 by weight percentage. In some more typical embodiments, the lithium replenishing coating 100 contains 4% to 45% of acid-modified sepiolite fiber composite material 110.

[0066] If the content of acid-modified sepiolite fiber composite material 110 in the lithium replenishment coating 100 is too low, it will not be conducive to improving the wettability and ionic conductivity of the separator, nor will it be conducive to improving the flame retardancy and cycle capacity retention of the battery. If the content of acid-modified sepiolite fiber composite material 110 in the lithium replenishment coating 100 is too high, it will not be conducive to the heat resistance of the battery and will easily lead to the problem of excessive moisture.

[0067] In the above-mentioned acid-modified sepiolite fiber composite material 110, the weight ratio of carboxylated sepiolite fiber 112 to lithium metal organic framework material can be from 10:1 to 5:1.

[0068] If the amount of carboxylated sepiolite fiber 112 is too small, it will not be conducive to the flame retardancy of the battery separator; if the amount of carboxylated sepiolite fiber 112 is too large, it will easily reduce the heat resistance of the battery separator.

[0069] In some optional embodiments, the length of the sepiolite fibers in the carboxylated sepiolite fibers 112 can be 0.5 μm to 50 μm, such as 0.5 μm, 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, 50 μm, etc., or any value or range within the range of 0.5 μm to 50 μm. In some more typical embodiments, the length of the sepiolite fibers is 5 μm to 25 μm; in some even more typical embodiments, the length of the sepiolite fibers is 10 μm to 15 μm.

[0070] In this invention, sepiolite fibers with a length of 0.5μm to 50μm are used, which is beneficial to improving the wettability and heat resistance of the ceramic coating film. If the length of the sepiolite fibers is too short, the peel strength of the coating film will be poor. If the length of the sepiolite fibers is too long, it will not be conducive to improving the wettability and heat resistance of the ceramic coating film.

[0071] In some optional embodiments, the aspect ratio of the sepiolite fibers in the carboxylated sepiolite fibers 112 can be from 10:1 to 100:1, such as 10:1, 15:1, 20:1, 25:1, 30:1, 35:1, 40:1, 45:1, 50:1, 55:1, 60:1, 65:1, 70:1, 75:1, 80:1, 85:1, 90:1, 95:1, or 100:1, or any value or range within the range of 10:1 to 100:1. In some more typical embodiments, the aspect ratio of the sepiolite fibers is from 15:1 to 90:1; in some even more typical embodiments, the aspect ratio of the sepiolite fibers is from 20:1 to 80:1.

[0072] In this invention, sepiolite fibers with an aspect ratio of 10:1 to 100:1 are used, which is beneficial to improving the wettability and heat resistance of the ceramic coating film. If the aspect ratio of the sepiolite fibers is too low (e.g., 5:1), the peel strength of the coating film will be poor. If the aspect ratio of the sepiolite fibers is too high (e.g., 120:1), it is not conducive to improving the wettability and heat resistance of the ceramic coating film.

[0073] Continuing from the above, using sepiolite fibers with the aforementioned length and aspect ratio range is more conducive to forming a stable interwoven structure than sepiolite fibers with other lengths and aspect ratios, thereby improving the heat resistance of the diaphragm.

[0074] Furthermore, the aforementioned lithium-replenishing coating 100 also contains ceramic material 120.

[0075] In some alternative embodiments, the lithium-replenishing coating 100 may contain 1% to 95% ceramic material 120 by weight percentage.

[0076] In some optional embodiments, the weight ratio of ceramic material 120 to acid-modified sepiolite fiber composite material 110 can be (19:1) to (1:1), such as 19:1, 18:2, 17:3, 16:4, 15:5, 14:6, 13:7, 12:8, 11:9, 10:9 or 9:9 (which can be expressed as 1:1), or any value or range within the range of (19:1) to (1:1). For example, the weight ratio of ceramic material 120 to acid-modified sepiolite fiber composite material 110 can be (3:1) to (1:1), such as 15:5 (which can be expressed as 3:1), 14.5:5.5, 14:6, 13.5:6.5, 13:7, 12.5:7.5, 12:8, 11.5:8.5, 11:9, 10.5:9.5, 10:9 or 9:9 (which can be expressed as 1:1), etc.

[0077] In some alternative embodiments, the ceramic material 120 may, by way of example but not limitation, include at least one of alumina, boehmite, silicon dioxide, titanium dioxide, magnesium hydroxide, aluminum hydroxide, barium titanate, and zinc oxide.

[0078] In some alternative embodiments, the D of the ceramic material 120 50 The micrometer size can be from 50 nm to 5 μm, such as 50 nm, 100 nm, 500 nm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, or 5 μm, or any value or range within the 50 nm to 5 μm range. In some typical embodiments, the D0 of the ceramic material 120... 50 The wavelength range is 80 nm to 4.5 μm; in some more typical embodiments, the D of the ceramic material 120 is... 50 Its range is 100nm to 3.5μm.

[0079] Using the above-mentioned D 50 The ceramic material with a value of 120 has more advantages than other D 50 The value of ceramic material 120 is more conducive to improving the heat resistance of ceramic coating film, D 50 If the moisture content is too low, the ceramic coating film will have an excessively high moisture content.

[0080] In some alternative embodiments, the lithium-replenishing coating 100 may also contain additives, which may include, for example, at least one of dispersants, adhesives, wetting agents and thickeners. In addition, other additives may be used as needed.

[0081] Based on 100 parts by weight of the ceramic material 120 and the acid-modified sepiolite fiber composite material 110 contained in the lithium replenishing coating 100, the amount of dispersant contained in the lithium replenishing coating 100 can be 0.05 parts to 5 parts, such as 0.05 parts, 0.1 parts, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts, or any value or range within the range of 0.05 parts to 5 parts.

[0082] The amount of adhesive contained in the lithium-replenishing coating 100 can be 0.5 parts to 10 parts, such as 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, 6.5 parts, 7 parts, 7.5 parts, 8 parts, 8.5 parts, 9 parts, 9.5 parts, or 10 parts, or any value or range within the range of 0.5 parts to 10 parts.

[0083] The amount of wetting agent contained in the lithium coating 100 can be 0.01 parts to 0.66 parts, such as 0.01 parts, 0.05 parts, 0.1 parts, 0.15 parts, 0.2 parts, 0.25 parts, 0.3 parts, 0.35 parts, 0.4 parts, 0.45 parts, 0.5 parts, 0.55 parts, 0.6 parts or 0.66 parts, or any value or range within the range of 0.01 parts to 0.66 parts.

[0084] The amount of thickener contained in the lithium coating 100 can be 0.5 parts to 5 parts, such as 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts or 5 parts, or any value or range within the range of 0.5 parts to 5 parts.

[0085] In some alternative embodiments, the dispersant described above may, by way of example but not by way of limitation, include at least one of sodium polyacrylate, ammonium polyacrylate, sodium hexametaphosphate, polyvinyl alcohol and polyethylene glycol.

[0086] In some alternative embodiments, the adhesive described above may, by way of example but not limitation, include at least one of polyacrylamide, polyvinylamide, polyvinylpyrrolidone, polymethyl methacrylate, polycarboxylic acid, polyacrylic acid, polyurethane acrylate, polyacrylate copolymer emulsion, cis-butadiene rubber, styrene-butadiene rubber, and polyurethane.

[0087] In some alternative embodiments, the wetting agent described above may, by way of example but not by way of limitation, include at least one of organic modified oxysilanes, polyols, and fatty alcohol ethers.

[0088] In some alternative embodiments, the thickener described above may, by way of example but not limitation, include at least one of methylcellulose, hydroxypropyl methylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, hydroxyethyl methylcellulose and hydroxypropylcellulose.

[0089] Accordingly, the present invention also provides a method for preparing the above-mentioned lithium-replenishing coating 100, comprising the following steps: coating a slurry containing acid-modified sepiolite fiber composite material 110 onto at least one side of the surface of the base film 200, and drying it.

[0090] When the lithium-replenishing coating 100 contains at least one of ceramic material 120 and / or additives, the acid-modified sepiolite fiber composite material 110 is first mixed with the ceramic material 120 and / or additives to obtain a slurry; then the slurry is coated on at least one side of the surface of the base film 200 and dried.

[0091] The above coating methods may include, but are not limited to, at least one of electrostatic spraying, blade coating, spin coating, extrusion coating, transfer coating, dip coating, gravure or microgravure coating.

[0092] In some alternative embodiments, the preparation method of acid-modified sepiolite fiber composite material 110 may include grafting metal-organic framework 111 material onto carboxylated sepiolite fiber 112.

[0093] The preparation of carboxylated sepiolite fiber 112 may include: acidifying sepiolite fiber to obtain acid-modified sepiolite fiber; and grafting carboxylic acid groups onto acid-modified sepiolite fiber.

[0094] The preparation of the above-mentioned acid-modified sepiolite fiber may include: acid activation treatment of sepiolite fiber with acid solution; followed by washing with water and drying.

[0095] In some preferred embodiments, the sepiolite fibers can be washed with water to remove impurities before acid activation treatment. For example, the sepiolite fiber raw material can be prepared into a suspension, stirred, and then dried to obtain the removed sepiolite fibers.

[0096] In some alternative embodiments, the acid solution used for acid activation treatment may exemplary include hydrochloric acid, and may also include sulfuric acid and / or nitric acid, etc. The concentration of the acid solution may be, for example, 1 mol / L.

[0097] In some optional embodiments, the solid-liquid ratio of sepiolite fiber to acid can be from 1g:10mL to 10g:10mL, such as 1g:10mL, 2g:10mL, 3g:10mL, 4g:10mL, 5g:10mL, 6g:10mL, 7g:10mL, 8g:10mL, 9g:10mL or 10g:10mL, or any value or range within the range of 1g:10mL to 10g:10mL.

[0098] In some optional embodiments, the acid activation treatment temperature can be 70℃~90℃ (e.g., 70℃, 75℃, 80℃, 85℃ or 90℃, etc.), and the acid activation treatment time can be 24h~48h (e.g., 24h, 32h, 40h or 48h, etc.).

[0099] The following is a specific method for preparing acid-modified sepiolite fiber: A 400 g / L sepiolite fiber raw material suspension is prepared using deionized water, stirred for 12 h, and then dried at 100 °C for 4 h to obtain impurity-removed sepiolite fiber; the impurity-removed sepiolite fiber is then acid-washed with 1 mol / L hydrochloric acid at a solid-liquid ratio of 1 g: 10 mL at 80 °C for 24 h, followed by water washing and filtration with deionized water, and then dried at 80 °C for 5 h to obtain acid-modified sepiolite fiber.

[0100] The above-mentioned acid-modified sepiolite fibers (such as...) Figure 3 (As shown) compared to unmodified sepiolite fibers (such as...) Figure 2Compared to (as shown), the former has a larger specific surface area and a higher degree of sparsity, which can provide more active sites for the formation of lithium metal organic framework materials.

[0101] In some alternative embodiments, grafting carboxylic acid groups onto acid-modified sepiolite fibers includes immersing the acid-modified sepiolite fibers in a coupling agent solution, followed by immersion in a carboxylic acid group providing solution. This process can be carried out at room temperature.

[0102] The coupling agent solution may, by way of example, include at least one of a silane coupling agent solution, a phthalate coupling agent solution, and an aluminate coupling agent solution. In some optional embodiments, the coupling agent solution may be a silane coupling agent solution, wherein the silane coupling agent may include at least one of KH550, KH792, and KH560, the solvent may be ethanol, and the concentration of the silane coupling agent in the silane coupling agent solution may be 0.2 mol / L.

[0103] The carboxylic acid group providing solution may, by way of example, include at least one selected from terephthalic acid solution, formic acid solution, acetic acid solution, oxalic acid solution, and succinic acid solution. In some alternative embodiments, the carboxylic acid group providing solution may be a terephthalic acid solution, wherein the solvent may be DMF, and the concentration of terephthalic acid in the terephthalic acid solution may be 0.15 mol / L.

[0104] The immersion in the coupling agent solution is defined as the first immersion stage, and the immersion in the carboxylic acid group providing solution is defined as the second immersion stage. The solid-liquid ratio in the first immersion stage can be 1:5, and the immersion time can be 4 to 8 hours. The solid-liquid ratio in the second immersion stage can be 1:3, and the immersion time can be 4 to 8 hours. After the second immersion stage, the carboxylation of the acid-modified sepiolite fiber is completed to facilitate the subsequent loading of lithium metal organic framework materials.

[0105] In some alternative embodiments, grafting the metal-organic framework 111 material onto the carboxylated sepiolite fiber 112 can be achieved by dissolving the carboxylated sepiolite fiber 112 and the raw material for preparing the lithium metal-organic framework in a solvent at room temperature, aging this mixture at room temperature for 24 to 48 hours, repeatedly rinsing with methanol to perform solid-liquid separation, and drying the solid.

[0106] The raw materials for preparing lithium-metal organic frameworks include a lithium source and an organic ligand. The lithium source provides lithium ions, and the organic ligand serves as the organic ligand; the two self-assemble through coordination bonds to form a crystalline porous material with a periodic network structure. Exemplarily, the lithium source may include at least one of LiClO4·3H2O, Li2CO3, and LiOH, preferably LiClO4·3H2O. The organic ligand may include 2-methylimidazole. 、At least one of N-ethylimidazole, N-propylimidazole, 4-nitroimidazole, and benzimidazole, preferably including 2-methylimidazole. In some typical embodiments, the raw materials for preparing the lithium metal organic framework include LiClO4·3H2O and 2-methylimidazole.

[0107] In some optional embodiments, the mass ratio of carboxylated sepiolite fiber 112 to the raw material for preparing the lithium metal organic framework is 1:2.5. The mass ratio of LiClO4·3H2O and 2-methylimidazole in the raw material for preparing the lithium metal organic framework is 1:1.

[0108] For example, the solvent for dissolving carboxylated sepiolite fiber 112 and lithium metal organic framework preparation raw materials can be a mixture of N,N-dimethylformamide (DMF) and ethylene glycol, and by way of example, the volume ratio of DMF to ethylene glycol can be 2:1.

[0109] Continuing from the above, the preparation method of the lithium-supplementing coating 100 provided by this invention is simple to operate and the process is easy to control. The sepiolite material used is abundant and inexpensive, which helps reduce product costs. By grafting metal-organic framework 111 onto carboxylated sepiolite fibers 112 to prepare an acid-modified sepiolite fiber composite material 110, the loose and porous structure of the sepiolite fibers and the increased specific surface area after acid modification can provide more active sites for the formation of Li-MOFs. Furthermore, Li-MOFs have porous channels, which can facilitate the release of free Li through a carrier mechanism. + Through the pores, Li + The coordinated movement of ions hopping along the frame edges provides a unique advantage for lithium-ion conduction. During the initial charge-discharge cycle of a lithium-ion battery, the introduction of Li-MOFs can provide a stable lithium source throughout battery operation. Carboxylated sepiolite fibers 112 exhibit a slow-release effect; the Li-MOFs adsorbed (grafted) in the carboxylated sepiolite fibers 112 gradually release lithium ions, replenishing the lithium-ion losses caused by the formation of the SEI film on the negative electrode. This allows the SEI film on the negative electrode surface to form rapidly and stably during battery cycling, improving the initial charge-discharge efficiency and cycle capacity retention of the lithium-ion battery.

[0110] It should also be emphasized that the Si-OH bonds in sepiolite fibers and the porous network structure formed by the interlacing of fibers have strong adsorption properties. This allows them to be mixed with ceramic material 120 to improve the electrolyte wetting performance of the lithium-ion coating 100, thereby enhancing the energy density, cycle life, and rate capability of the lithium-ion battery. Furthermore, the uniform mixing and coating of carboxylated sepiolite fibers 112 with ceramic material 120 onto the base membrane 200 forms a robust "reinforced concrete" structure, which improves the separator's peel and puncture resistance. In addition, sepiolite is a highly stable inorganic clay material with good high-temperature resistance. During heating, sepiolite gradually releases zeolite water and coordinated water with metal ions from its pores. This evaporated water (approximately 15% of the total mass of sepiolite) can act as a flame retardant, improving the flame retardant performance of the battery separator and thus enhancing the safety of the lithium-ion battery.

[0111] Furthermore, the present invention also provides a separator comprising a base film 200 and a coating disposed on at least one side surface of the base film 200, the coating being the aforementioned lithium replenishment coating 100.

[0112] In some alternative embodiments, the base membrane 200 may, by way of example but not limitation, include at least one of a polyolefin membrane, a cellulose membrane, a polyester membrane, a nanofiber nonwoven membrane, and an aramid membrane.

[0113] In some optional embodiments, the thickness of the diaphragm can be 5.5 μm to 25.5 μm, such as 5.5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, or 25.5 μm, or any value or range within the range of 5.5 μm to 25.5 μm. In some more typical embodiments, the thickness of the diaphragm is 7.5 μm to 23.5 μm; in some even more typical embodiments, the thickness of the diaphragm is 9.5 μm to 20.5 μm.

[0114] In some optional embodiments, the thickness of the base film 200 can be 5 μm to 25 μm, such as 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, or 25 μm, or any value or range within the range of 5 μm to 25 μm. In some more typical embodiments, the thickness of the base film 200 is 7 μm to 23 μm; in some even more typical embodiments, the thickness of the base film 200 is 9 μm to 20 μm.

[0115] In some optional embodiments, the thickness of the lithium replenishment coating 100 can be 0.5 μm to 10 μm, such as 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, or any value or range within the range of 0.5 μm to 10 μm. In some more typical embodiments, the thickness of the lithium replenishment coating 100 is 0.5 μm to 8 μm; in some even more typical embodiments, the thickness of the lithium replenishment coating 100 is 0.5 μm to 5 μm. It should be noted that the sum of the thicknesses of the lithium replenishment coating 100 and the base film 200 must satisfy the aforementioned thickness range of the separator.

[0116] The aforementioned separator has good electrolyte wetting properties, flame retardant properties, and peeling ability. It also has a low high-temperature shrinkage rate, which is beneficial to improving battery safety performance, initial charge and discharge efficiency, and cycle life.

[0117] Furthermore, the present invention also provides a battery comprising a positive electrode, a negative electrode, and the aforementioned separator, wherein the positive electrode and the negative electrode are separated by the separator.

[0118] This battery has good flame retardant properties, high initial charge-discharge efficiency, and long cycle life.

[0119] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0120] Example 1

[0121] This embodiment provides a lithium replenishment coating 100, the preparation method of which includes the following steps:

[0122] S1: Preparation of acid-modified carboxylated sepiolite fiber 112.

[0123] S11: Prepare a 400 g / L sepiolite fiber raw material suspension using deionized water, stir for 12 h, and then dry at 100℃ for 4 h to obtain sepiolite fiber after impurity removal.

[0124] The sepiolite fiber raw material has a length of 2μm and an aspect ratio of 15:1.

[0125] S12: The purified sepiolite fiber is acid-washed with 1 mol / L hydrochloric acid at a solid-liquid ratio of 1 g: 10 mL at 80 °C for 24 h, then washed and filtered with deionized water, and finally dried at 80 °C for 5 h to obtain acid-modified sepiolite fiber.

[0126] S2: Preparation of acid-modified sepiolite fiber composite material 110.

[0127] S21: The acid-modified sepiolite fiber obtained in S12 was immersed in a silane coupling agent solution (specifically KH550, solvent ethanol, concentration of silane coupling agent in the silane coupling agent solution was 0.2 mol / L) at a solid-liquid ratio of 1:5 for 8 hours. Then, it was immersed in a terephthalic acid solution (solvent DMF, concentration of terephthalic acid in the terephthalic acid solution was 0.15 mol / L) at a solid-liquid ratio of 1:3 for 8 hours to obtain carboxylated sepiolite fiber 112.

[0128] S22: The carboxylated sepiolite fiber 112 obtained in S21 was mixed with LiClO4·3H2O and 2-methylimidazole at a mass ratio of 0.8:1:1, and then dissolved in 500 mL of a mixture of DMF and ethylene glycol at a volume ratio of 2:1, so that Li-MOFs were grafted onto the carboxylated sepiolite fiber 112. This mixture was aged at room temperature for 24 h, and the mixture was repeatedly washed with methanol to separate the solid and liquid. The solid was dried to obtain acid-modified sepiolite fiber composite material 110.

[0129] S3: Prepare a slurry containing acid-modified sepiolite fiber composite material 110.

[0130] S31: Dissolve 1.5g of dispersant (sodium polyacrylate) in 300g of deionized water and stir at 1000r / min for 1h to form an aqueous dispersant solution;

[0131] S32: Add 10g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above to the dispersant aqueous solution in S31 above, and stir at 2000r / min for 1h; then add 190g of boehmite (D 50 (500 nm), stir at 2000 r / min for 1 h;

[0132] S33: Add another 10g of thickener (sodium carboxymethyl cellulose) and stir at 500r / min for 30min;

[0133] S34: Add 20g of adhesive (polymethyl methacrylate) and stir at 300r / min for 30min;

[0134] S35: After the mixture is evenly dispersed, add 0.05g of wetting agent (fatty alcohol ether) and stir at 300r / min for 30min to obtain a uniform coating slurry.

[0135] S4: Prepare lithium-replenishing coating 100.

[0136] The above coating slurry was applied to one side of a polyethylene film with a thickness of 9 μm using a coating machine and dried in an oven at 60°C for 30 min. After drying, a single-sided coated diaphragm was obtained, in which the thickness of the lithium coating 100 was 2 μm.

[0137] By weight percentage, the lithium-replenishing coating 100 contains 4.3% acid-modified sepiolite fiber composite material 110 and 82% ceramic material 120.

[0138] Example 2

[0139] The difference between this embodiment and embodiment 1 is as follows: S32: 20g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 180g of boehmite is added, and stirred at 2000r / min for 1h.

[0140] Example 3

[0141] The difference between this embodiment and embodiment 1 is as follows: S32: 30g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 170g of boehmite is added, and stirred at 2000r / min for 1h.

[0142] Example 4

[0143] The difference between this embodiment and embodiment 1 is as follows: S32: 40g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 160g of boehmite is added, and stirred at 2000r / min for 1h.

[0144] Example 5

[0145] The difference between this embodiment and embodiment 1 is as follows: S32: 50g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 150g of boehmite is added, and stirred at 2000r / min for 1h.

[0146] Example 6

[0147] The difference between this embodiment and embodiment 1 is as follows: S32: 60g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 140g of boehmite is added, and stirred at 2000r / min for 1h.

[0148] Example 7

[0149] The difference between this embodiment and embodiment 1 is as follows: S32: 70g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 130g of boehmite is added, and stirred at 2000r / min for 1h.

[0150] Example 8

[0151] The difference between this embodiment and embodiment 1 is as follows: S32: 80g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 120g of boehmite is added, and stirred at 2000r / min for 1h.

[0152] Example 9

[0153] The difference between this embodiment and embodiment 1 is as follows: S32: 90g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 110g of boehmite is added, and stirred at 2000r / min for 1h.

[0154] Example 10

[0155] The difference between this embodiment and embodiment 1 is as follows: S32: 90g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 100g of boehmite is added, and stirred at 2000r / min for 1h.

[0156] Example 11

[0157] The difference between this embodiment and embodiment 1 is as follows: S32: 90g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 90g of boehmite is added, and stirred at 2000r / min for 1h.

[0158] Example 12

[0159] The difference between this embodiment and embodiment 6 is as follows: S32: 60g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 140g of alumina is added, and stirred at 2000r / min for 1h.

[0160] Example 13

[0161] The difference between this embodiment and embodiment 6 is as follows: S32: 60g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 140g of barium titanate is added, and stirred at 2000r / min for 1h.

[0162] Example 14

[0163] The difference between this embodiment and embodiment 6 is as follows: S32: 60g of the acid-modified sepiolite fiber composite material 110 obtained in S3 above is added to the dispersant aqueous solution in S31 above, and stirred at 2000r / min for 1h; then 140g of magnesium hydroxide is added, and stirred at 2000r / min for 1h.

[0164] Example 15

[0165] The difference between this embodiment and Embodiment 1 is that the length of the sepiolite fiber is 5 μm and the aspect ratio is 90:1.

[0166] Example 16

[0167] The difference between this embodiment and Embodiment 1 is that the length of the sepiolite fiber is 10 μm and the aspect ratio is 20:1.

[0168] Example 17

[0169] The difference between this embodiment and Embodiment 1 is that the length of the sepiolite fiber is 15 μm and the aspect ratio is 50:1.

[0170] Example 18

[0171] The difference between this embodiment and Embodiment 1 is that the lithium replenishment coating 100 does not contain ceramic material 120.

[0172] Example 19

[0173] The difference between this embodiment and Embodiment 6 is that the length of the sepiolite fiber is 0.1 μm.

[0174] Example 20

[0175] The difference between this embodiment and Embodiment 6 is that the length of the sepiolite fiber is 80 μm.

[0176] Example 21

[0177] The difference between this embodiment and embodiment 6 is that the aspect ratio of the sepiolite fiber is 5:1.

[0178] Example 22

[0179] The difference between this embodiment and embodiment 6 is that the aspect ratio of the sepiolite fiber is 120:1.

[0180] Example 23

[0181] The difference between this embodiment and Embodiment 6 is that the content of acid-modified sepiolite fiber composite material 110 in the lithium replenishment coating 100 is only 0.5 wt%.

[0182] Comparative Example 1

[0183] The difference between this comparative example and Example 6 is that only step S3 is performed, and step S32 is: 200g of boehmite is added to the dispersant aqueous solution in step S31 and stirred at 2000r / min for 1h.

[0184] That is, the lithium-replenishing coating 100 in this comparative example does not contain acid-modified sepiolite fiber composite material 110.

[0185] Comparative Example 2

[0186] The difference between this comparative example and Example 6 is that the sepiolite fiber was directly grafted with carboxylic acid groups without acid modification.

[0187] Test case

[0188] The diaphragms obtained in Examples 1 to 23 and Comparative Examples 1 to 2 were subjected to the following performance tests, and the results are shown in Table 1.

[0189] The performance testing methods are as follows:

[0190] ① Wetting test method: Cut the diaphragm into a sample with a length × width of 50mm × 50mm, and mark it with longitudinal (MD) and transverse (TD) markings. Lay the diaphragm flat on a glass slide and fix it in place with green tape at the four corners. Observe the diffusion distance of the droplet after 5 minutes using a handheld digital microscope. The magnification is 20x, the volume of a single droplet is 2μL, and the droplet is injected by syringe at a rate of 1mL.

[0191] ② The contact angle test shall be conducted in accordance with GB / T 30693-2014 Measurement of the contact angle between plastic film and water 10.2.

[0192] ③ Test method for ionic conductivity: Cut five 50mm × 50mm membrane pieces, immerse them in the electrolyte, keep them sealed and soak for 30 minutes, and then test the AC impedance of the soaked membranes. Plot the number of membrane layers on the x-axis and the membrane resistance on the y-axis, and calculate the slope k of the curve, which is the membrane impedance value. The ionic conductivity σ of the membrane can be derived from the membrane impedance value R.

[0193] The ionic conductivity of the membrane can be calculated using the following formula: σ=d / (R×S), R=k×1;

[0194] Where d is the thickness of the sample (cm); R is the bulk impedance of the sample (ohms), which can be obtained from the intersection of the semicircle and the oblique line in the Nyquist electrochemical impedance spectroscopy plot; S is the effective area of ​​the diaphragm (cm²). 2 ).

[0195] ④ Flame retardancy test method: Take a strip of diaphragm of the same size (1cm × 5cm) and ignite it with an open flame. Start timing from the moment a stable open flame source contacts the bottom of the diaphragm sample strip until successful ignition. The time consumed to ignite the diaphragm sample strip is called the flame retardancy time.

[0196] ⑤ Method for testing battery cycle capacity: Take a separator with a width of 86mm to make a soft-pack cell, and cycle it at 1C for 1000 cycles at a temperature of 25℃±2℃, and record the battery cycle capacity retention rate.

[0197] ⑥ Peel strength test method: Cut the coated film into samples of 2.5cm × 30.5cm in length. Then peel the sample from the flexible or rigid substrate at a separation speed of 152.4mm / min at a 180-degree angle and record the test value.

[0198] ⑦ Test method for shrinkage rate: Cut the modified composite diaphragm into 5cm×5cm pieces and place them in an oven. Incubate at 150℃ for 60 minutes. The method for testing the heat shrinkage rate refers to the standard GBT36363-2018. The heat shrinkage rate of the diaphragm is measured on both the longitudinal (MD) and transverse (TD) axes. The average value of the heat shrinkage rates on the MD and TD axes is then defined as the heat shrinkage rate of the diaphragm.

[0199] ⑧. First-time efficiency test method: The formation process is performed on the new Wei machine, that is, the battery cell is charged and discharged according to the preset charge and discharge program. The capacity during the formation process is recorded as PIEF capacity.

[0200] Initial charging: Under conditions of 42℃±5℃, charge at a constant current rate of 0.5C to 4.2V, and then at a constant voltage to 4.2V. The capacity generated during the constant current and constant voltage process is recorded as the initial charging capacity.

[0201] Resting: After charging is complete, let the battery cell rest for a period of time (e.g., 30 minutes) to ensure that the battery cell reaches a balanced state.

[0202] Initial discharge: Discharge at a rate of 0.5C to 2.8V, and the discharge capacity during the discharge process is the initial discharge capacity.

[0203] Data recording: During the formation process, record data such as initial charging capacity, PIEF capacity, and initial discharge capacity.

[0204] First-time efficiency calculation: Based on the recorded data, calculate the first-time efficiency of the battery cell. The formula for calculating the first-time efficiency is: Initial discharge capacity / (Initial charge capacity + PIEF capacity) × 100%.

[0205] Table 1 Test Results

[0206]

[0207]

[0208] As shown in Table 1, the first-time efficiency, wettability, contact angle, membrane ionic conductivity, battery cycle capacity retention, and peeling force of Examples 1-17 of the present invention are significantly better than those of Comparative Example 1. This is because the loose and porous structure of sepiolite fibers and the increased specific surface area after acid modification can provide more active sites for the formation of Li-MOFs. Furthermore, Li-MOFs have porous channels, which can facilitate the free Li through a carrier mechanism. + Through the pores, Li + The coordinated movement of ions hopping along the frame edges provides a unique advantage for lithium-ion conduction. During the initial charge-discharge cycle of a lithium-ion battery, the introduction of Li-MOFs can provide a stable lithium source throughout battery operation. Carboxylated sepiolite fibers 112 exhibit a slow-release effect; the Li-MOFs adsorbed (grafted) in the carboxylated sepiolite fibers 112 gradually release lithium ions, replenishing the lithium-ion losses caused by the formation of the SEI film on the negative electrode. This allows the SEI film on the negative electrode surface to form rapidly and stably during battery cycling, improving the initial charge-discharge efficiency and cycle capacity retention of the lithium-ion battery.

[0209] Furthermore, flame retardant experimental data demonstrate that the introduction of nano-sepiolite fibers prolongs the combustion time of the separator and improves its safety performance. This is because sepiolite is an inorganic clay material with high stability and good high-temperature resistance. During the heating process, sepiolite gradually releases zeolite water and coordinated water with metal ions in its pores. This evaporated water (accounting for about 15% of the total mass of sepiolite) can act as a flame retardant, improving the flame retardant performance of the battery separator and thus enhancing the safety of lithium-ion batteries.

[0210] Heat shrinkage experiments show that adding an appropriate amount of acid-modified sepiolite fiber composite material 110 to the coating can play a supporting role, but the amount added should not be too much, otherwise it will affect the adhesion between the adhesive and the ceramic particles, thus reducing the heat resistance of the coating.

[0211] A comparison between Example 6 and Comparative Example 2 shows that Example 6 has better ionic conductivity, battery cycle performance, and first-efficiency than Comparative Example 2. This may be because the acid-modified sepiolite fiber has a larger specific surface area and a higher degree of sparsity than the unmodified sepiolite fiber, which can provide more active sites for the formation of lithium metal organic framework materials, thereby improving the above-mentioned performance.

[0212] A comparison between Example 6 and Example 18 shows that Example 6 exhibits superior heat resistance, peel strength, and initial performance compared to Example 18. This may be because the acid-modified sepiolite fiber composite material 110 coating cannot effectively adhere to the adhesive, thus affecting the coating's heat resistance. It should be noted that Example 18 uses a pure sepiolite composite material, which has better flame retardancy than Example 6. However, Example 18 does not contain ceramic materials, leading to a decrease in its areal density. Furthermore, the fibrous nature of sepiolite reduces the contact area with the adhesive, further affecting the coating's support and consequently reducing its heat resistance.

[0213] A comparison of Examples 1, 15-17, and 19-20 shows that if the length of the sepiolite fiber is too short, the peel strength of the coating film will be poor; if the length of the sepiolite fiber is too long, it will not be conducive to improving the wettability and heat resistance of the ceramic coating film.

[0214] The comparison between Examples 1 and Examples 21-22 shows that if the aspect ratio of sepiolite fibers is too low, the peel strength of the coating film will be poor; if the aspect ratio of sepiolite fibers is too high, it will not be conducive to improving the wettability and heat resistance of the ceramic coating film.

[0215] In summary, the lithium-replenishing coating 100 provided by the present invention has good electrolyte wetting properties and flame retardant properties. When it is used to prepare a separator and further prepared into a battery, the battery can have good flame retardant properties, high initial charge and discharge efficiency, and long cycle life.

[0216] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A lithium-replenishing coating, characterized in that, The lithium replenishing coating contains an acid-modified sepiolite fiber composite material, which includes carboxylated sepiolite fibers and a lithium metal organic framework material grafted onto the carboxylated sepiolite fibers. The carboxylated sepiolite fiber is obtained by grafting carboxylic acid groups onto acidified sepiolite fiber.

2. The lithium-replenishing coating according to claim 1, characterized in that, The lithium-replenishing coating has at least one of the following characteristics: Feature 1: By weight percentage, the lithium replenishing coating contains 1% to 50% acid-modified sepiolite fiber composite material; Feature 2: The weight ratio of carboxylated sepiolite fiber to lithium metal organic framework material is 10:1 to 5:1; Feature 3: The length of the sepiolite fibers in the carboxylated sepiolite fibers is 0.5μm~50μm; Feature 4: The aspect ratio of sepiolite fibers in carboxylated sepiolite fibers is 10:1 to 100:

1.

3. The lithium-replenishing coating according to claim 1 or 2, characterized in that, The lithium replenishing coating also contains ceramic materials; The ceramic material has at least one of the following characteristics: Feature 5: The weight ratio of the ceramic material to the acid-modified sepiolite fiber composite material is (19:1) to (1:1); Feature 6: The ceramic material includes at least one of alumina, boehmite, silicon dioxide, titanium dioxide, magnesium hydroxide, aluminum hydroxide, barium titanate, and zinc oxide; Feature 7: The D of the ceramic material 50 Its size is 50nm~5μm.

4. The lithium-replenishing coating according to claim 3, characterized in that, The lithium-replenishing coating also contains additives; The additives include at least one of dispersants, adhesives, wetting agents, and thickeners.

5. A method for preparing a lithium-supplementing coating as described in any one of claims 1 to 4, characterized in that, Includes the following steps: A slurry containing acid-modified sepiolite fiber composite material is coated onto at least one side of the base film and then dried.

6. The preparation method according to claim 5, characterized in that, The preparation method of the acid-modified sepiolite fiber composite material includes: grafting a lithium metal organic framework material onto carboxylated sepiolite fibers.

7. The preparation method according to claim 6, characterized in that, The preparation of the acid-modified sepiolite fiber composite material includes: dissolving carboxylated sepiolite fiber and lithium metal organic framework preparation raw materials in a solvent, separating the solid and liquid, and drying the solid.

8. The preparation method according to claim 7, characterized in that, The raw materials for preparing the lithium metal organic framework include a lithium source and organic ligands; The lithium source includes at least one of LiClO4·3H2O, Li2CO3, and LiOH; The organic ligands include at least one of 2-methylimidazole, N-ethylimidazole, N-propylimidazole, 4-nitroimidazole, and benzimidazole.

9. The preparation method according to claim 6, characterized in that, The preparation of the carboxylated sepiolite fiber includes: acidifying the sepiolite fiber to obtain acid-modified sepiolite fiber; and grafting carboxylic acid groups onto the acid-modified sepiolite fiber.

10. The preparation method according to claim 9, characterized in that, The preparation of the acid-modified sepiolite fiber includes: acid activation treatment of the sepiolite fiber with acid solution; followed by washing with water and drying.

11. The preparation method according to claim 10, characterized in that, Acid activation treatment includes at least one of the following characteristics: Feature 8: The acid solution includes at least one of hydrochloric acid, nitric acid, and sulfuric acid; Feature 9: The solid-liquid ratio of the sepiolite fiber to the acid solution is 1g:10mL to 10g:10mL; feature 10: The acid activation treatment temperature is 70℃~90℃; Feature 11: The acid activation treatment time is 24h~48h; Feature 12: Before acid activation treatment, the sepiolite fibers are first washed with water to remove impurities.

12. The preparation method according to claim 9, characterized in that, The grafting of carboxylic acid groups includes immersing the acid-modified sepiolite fiber in a coupling agent solution, followed by immersion in a carboxylic acid group providing solution.

13. The preparation method according to claim 12, characterized in that, The grafted carboxylic acid group includes at least one of the following characteristics: Feature 13: The coupling agent solution includes at least one of silane coupling agent solution, phthalate coupling agent solution and aluminate coupling agent solution; Feature 14: The carboxylic acid group providing solution includes at least one of terephthalic acid solution, formic acid solution, acetic acid solution, oxalic acid solution and succinic acid solution; Feature 15: The soaking time in the silane coupling agent solution is 4h~8h; Feature 16: The soaking time in the carboxylic acid group providing solution is 4h~8h.

14. A diaphragm, characterized in that, The diaphragm includes a base membrane and a coating disposed on at least one side surface of the base membrane, wherein the coating is a lithium replenishment coating as described in any one of claims 1 to 4.

15. The diaphragm according to claim 14, characterized in that, The diaphragm includes at least one of the following features: Feature 17: The thickness of the diaphragm is 5.5 μm to 25.5 μm; Feature 18: The thickness of the base film is 5μm~25μm; Feature 19: The thickness of the lithium replenishment coating is 0.5μm~10μm; Feature 20: The base membrane includes at least one of polyolefin membrane, cellulose membrane, polyester membrane, nanofiber nonwoven membrane and aramid membrane.

16. A battery, characterized in that, It includes a positive electrode, a negative electrode, and a separator as described in claim 14 or 15, wherein the positive electrode and the negative electrode are separated by the separator.

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