Lithium supplementing coating and preparation method thereof, diaphragm and battery

Abstract

The invention discloses a lithium supplementing coating and a preparation method thereof, a diaphragm and a battery, and belongs to the technical field of battery materials. The lithium supplementing coating contains an acid modified sepiolite fiber composite material, and the acid modified sepiolite fiber composite material comprises carboxylated sepiolite fibers and a metal lithium organic framework material grafted on the carboxylated sepiolite fibers. Si-OH bonds in sepiolite fibers and a porous net structure formed by staggering the fibers have relatively strong adsorbability, and the sepiolite fibers subjected to carboxylation modification have a relatively large specific surface area, so that more active sites can be provided for the metal lithium organic framework material, and the metal lithium organic framework material has relatively good electrolyte wettability. The sepiolite fiber has unique water loss property, so that the flame retardant property of the battery diaphragm can be enhanced, 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 irreversible lithium loss is reduced, and the cycle life of the battery is prolonged. The diaphragm containing the lithium supplementing coating has a relatively good application prospect in batteries.

Description

Technical Field

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

[0002] With the continuous improvement of the market application requirements of lithium-ion batteries, enhancing the safety performance of batteries and increasing the cycle life of lithium-ion batteries have become the research hotspots of power battery manufacturers. At present, the materials used as commercial separators in the lithium-ion battery market are mostly porous polyolefin materials, among which polypropylene (PP) and polyethylene (PE) are the most widely used, and they have the characteristics of high mechanical strength and good chemical stability. However, the hydrophobicity of polyolefin materials results in poor electrolyte wettability of porous polyolefin separators, which will limit the discharge capacity of batteries, especially the discharge capacity of batteries operating in high-temperature and high-pressure environments. Moreover, during the first charge and discharge process of lithium-ion batteries, a solid electrolyte interface film (SEI film) will be formed at the contact interface between the negative electrode and the electrolyte. The SEI film is a good conductor of lithium ions, but the formation of the SEI film will consume some lithium ions in the positive electrode material, resulting in insufficient supply of lithium ions in the positive electrode material and reducing the battery capacity. During the battery cycling process, the insertion and extraction of lithium ions will repeatedly consume the SEI film, causing irreversible lithium consumption to varying degrees in both the positive and negative electrodes, thereby leading to a decline in the battery's cycling ability. In addition, as one of the most important safety components in batteries, the thermal stability and flame retardancy of lithium-ion battery separators are also important performance indicators. Developing separators with high stability and flame retardancy is beneficial to prevent short circuits and thermal runaway explosions of batteries at high temperatures.

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

[0004] The purpose of the present invention is to provide a lithium supplement coating, a preparation method thereof, a separator, and a battery to solve or improve the above technical problems.

[0005] The present invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a lithium supplement coating, which contains an acid-modified sepiolite fiber composite material. The acid-modified sepiolite fiber composite material includes carboxylated sepiolite fibers and a metal-organic framework material grafted onto the carboxylated sepiolite fibers.

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

[0008] Characteristic 1: By weight percentage, the lithium supplement coating contains 1% - 50% of the acid-modified sepiolite fiber composite material;

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

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

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

[0012] In an alternative embodiment, the lithium supplement coating further contains a ceramic material;

[0013] The ceramic material has at least one of the following features:

[0014] Feature 5: The weight ratio of the ceramic material to the 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, silica, titanium dioxide, magnesium hydroxide, aluminum hydroxide, barium titanate, and zinc oxide;

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

[0017] In an alternative embodiment, the lithium supplement coating further contains an auxiliary agent;

[0018] The auxiliary agent includes at least one of a dispersant, an adhesive, a wetting agent, and a thickener.

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

[0020] In an alternative 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, polyols, and fatty alcohol ethers;

[0023] And / or, the thickening agent includes at least one of methylcellulose, hydroxypropyl methylcellulose, sodium carboxymethylcellulose, hydroxyethyl cellulose, hydroxyethyl methylcellulose, and hydroxypropyl cellulose.

[0024] In a second aspect, the present invention provides a method for preparing a lithium supplement coating according to any one of the foregoing embodiments, including the following steps: coating a slurry containing an acid-modified sepiolite fiber composite material on the surface of at least one side of a base film, and drying.

[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 the acid-modified sepiolite fiber composite material includes: dissolving carboxylated sepiolite fibers and metal lithium organic framework preparation raw materials in a solvent, performing solid-liquid separation, and drying the solid matter.

[0027] In an optional embodiment, the metal lithium organic framework preparation raw materials include a lithium source and an organic ligand.

[0028] In an optional embodiment, 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 metal lithium organic framework preparation raw materials include LiClO4·3H2O and 2-methylimidazole.

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

[0032] In an optional embodiment, the preparation of acid-modified sepiolite fibers includes: performing acid activation treatment on sepiolite fibers with an acid solution; then 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 1 g:10 mL to 10 g:10 mL;

[0036] Feature 10: The temperature of the acid activation treatment is 70°C to 90°C;

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

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

[0039] In an alternative embodiment, grafting carboxylic acid groups includes: immersing the acid-modified sepiolite fiber in a coupling agent solution, and then immersing it in a carboxylic acid group-providing solution.

[0040] In an alternative embodiment, grafting carboxylic acid groups includes at least one of the following features:

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

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

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

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

[0045] In a third aspect, the present invention provides a separator, which includes a base film and a coating provided on at least one surface of the base film, and the coating is the lithium supplement coating of any one of the foregoing embodiments.

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

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

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

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

[0050] Feature 20: The base film includes at least one of a polyolefin separator, a cellulose separator, a polyester separator, a nanofiber non-woven separator, and an aramid separator.

[0051] In a fourth aspect, the present invention provides a battery, which includes a positive electrode, a negative electrode, and the separator of the foregoing embodiments, and the positive electrode and the negative electrode are isolated by the separator.

[0052] The beneficial effects of the present invention include:

[0053] The lithium supplement coating provided by the present invention contains an acid-modified sepiolite fiber composite material, and the acid-modified sepiolite fiber composite material includes carboxylated sepiolite fibers and a metal-organic framework material grafted onto the carboxylated sepiolite fibers. Among them, the Si-OH bonds in the sepiolite fibers and the porous network structure formed by the fiber interlacing have strong adsorption properties. In addition, the carboxylated sepiolite fibers have a large specific surface area, which can provide more active sites for the metal-organic framework material, and can have better electrolyte wetting performance after being compounded with ceramic materials than the coating prepared only from ceramic materials. And, the sepiolite fibers have unique water loss properties, which can enhance the flame retardant performance of the battery separator and improve the safety of lithium-ion batteries. In addition, the metal-organic framework material in the composite material can be used as a lithium supplement agent, slowly release lithium ions during the charge and discharge process, reduce the irreversible loss of lithium, accelerate the lithium ion transmission rate, improve the problem of insufficient lithium ion content in the positive electrode after the formation of the SEI film on the negative electrode material, and extend the cycle life of the battery.

[0054] The separator with the above lithium supplement coating has good electrolyte wetting performance and flame retardant performance, etc., which is beneficial to improving the safety performance, first charge and discharge efficiency, and cycle life of the battery. Description of the Drawings

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as a limitation of the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0056] Figure 1 It is a schematic structural diagram of the separator provided by the present invention;

[0057] Figure 2 It is an SEM image of sepiolite fibers before acid modification provided by the present invention;

[0058] Figure 3 It is an SEM image of sepiolite fibers after acid modification provided by the present invention.

[0059] Icons: 100 - lithium - supplementing coating; 110 - acid - modified sepiolite fiber composite; 111 - metal - organic framework; 112 - carboxylated sepiolite fiber; 120 - ceramic material; 200 - base film. Detailed implementation manners

[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. For those not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are followed. The reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0061] The lithium - supplementing coating provided by the present invention, its preparation method, separator, and battery will be specifically described below.

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

[0063] Among them, the Si - OH bonds in the sepiolite fibers and the porous network structure formed by the fiber interlacing have strong adsorption. During the high - temperature heating process, the sepiolite fibers will gradually release the zeolite water and coordinated water of Mg ion coordination in the pores, which is beneficial to improving the flame retardancy of the battery. In addition, the carboxylated sepiolite fibers have a large specific surface area, which can provide more active sites for the metal - lithium organic framework material (denoted as Li - MOF), and have better electrolyte wetting performance than a single ceramic particle coating. And the 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 metal - lithium organic framework material in the composite can be used as a lithium - supplementing agent, slowly releasing lithium ions during the charge - discharge process, accelerating the lithium - ion transmission rate, improving the problem of insufficient lithium - ion content in the positive electrode after the formation of the SEI film on the negative electrode material, and extending the cycle life of the battery.

[0064] The above - mentioned lithium - supplementing coating 100 has good electrolyte wetting performance and flame retardancy, and can improve the first charge - discharge efficiency of the battery and the cycle life of the battery.

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

[0066] If the content of the acid - modified sepiolite fiber composite material 110 in the lithium - supplementing coating 100 is too small, it is not conducive to improving the wettability and ionic conductivity of the separator, and is not conducive to enhancing the flame retardancy and cycle capacity retention rate of the battery; if the content of the acid - modified sepiolite fiber composite material 110 in the lithium - supplementing coating 100 is too large, it is not conducive to the heat resistance of the battery and is prone to the problem of excessive moisture.

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

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

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

[0070] In the present invention, using sepiolite fibers with a length of 0.5μm - 50μm is conducive to improving the wettability and heat resistance of the ceramic coating film; 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 is not conducive to improving the wettability and heat resistance of the ceramic coating film.

[0071] In some alternative embodiments, the aspect ratio of the sepiolite fibers in the carboxylated sepiolite fibers 112 may 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, etc., or may also be any value or any range within the range of 10:1 to 100:1. In some relatively typical embodiments, the aspect ratio of the sepiolite fibers is from 15:1 to 90:1; in some more typical embodiments, the aspect ratio of the sepiolite fibers is from 20:1 to 80:1.

[0072] In the present invention, using sepiolite fibers with an aspect ratio of 10:1 to 100:1 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 (such as 5:1), it will cause the peel strength of the coating film to deteriorate; if the aspect ratio of the sepiolite fibers is too high (such as 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 above length and aspect ratio ranges is more conducive to forming a stable intertwined structure and improving the heat resistance of the separator than sepiolite fibers with other lengths and aspect ratios.

[0074] Furthermore, the above-mentioned lithium supplement coating 100 further contains a ceramic material 120.

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

[0076] In some alternative embodiments, the weight ratio of the ceramic material 120 to the acid-modified sepiolite fiber composite material 110 may 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), etc., or may also be any value or any range within the range of (19:1) to (1:1). By way of example, the weight ratio of the ceramic material 120 to the acid-modified sepiolite fiber composite material 110 may 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 exemplarily but non - limitatively include at least one of alumina, boehmite, silica, titanium dioxide, magnesium hydroxide, aluminum hydroxide, barium titanate, and zinc oxide.

[0078] In some alternative embodiments, the D of the ceramic material 120 50 may 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, etc., or may be any value or any range within the range of 50 nm to 5 μm. In some relatively typical embodiments, the D of the ceramic material 120 50 is from 80 nm to 4.5 μm; in some more typical embodiments, the D of the ceramic material 120 50 is from 100 nm to 3.5 μm.

[0079] Using the ceramic material 120 with the above - mentioned D 50 value is more conducive to improving the heat resistance of the ceramic coating film than the ceramic material 120 with other D 50 values. If D 50 is too small, it will cause the moisture content of the ceramic coating film to be too high.

[0080] In some alternative embodiments, the above - mentioned lithium - supplementing coating 100 may further contain additives. The additives may exemplarily include at least one of a dispersant, an adhesive, a wetting agent, and a thickening agent. In addition, other additives may also be used according to actual needs.

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

[0082] The amount of the adhesive contained in the lithium - supplementing coating 100 may be from 0.5 part to 10 parts, such as 0.5 part, 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, etc., or may be any value or any range within the range of 0.5 part to 10 parts.

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

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

[0085] In some alternative embodiments, the above-mentioned dispersant can exemplarily but non-limitingly include at least one of sodium polyacrylate, ammonium polyacrylate, sodium hexametaphosphate, polyvinyl alcohol and polyethylene glycol.

[0086] In some alternative embodiments, the above-mentioned adhesive can exemplarily but non-limitingly include at least one of polyacrylamide, polyvinylamide, polyvinylpyrrolidone, polymethyl methacrylate, polycarboxylic acid, polyacrylic acid, polyurethane acrylate, polyacrylate copolymer emulsion, cis-1,4-polybutadiene rubber, styrene-butadiene rubber and polyurethane.

[0087] In some alternative embodiments, the above-mentioned wetting agent can exemplarily but non-limitingly include at least one of organically modified oxygen silicon-based, polyhydric alcohol-based and fatty alcohol ether-based.

[0088] In some alternative embodiments, the above-mentioned thickening agent can exemplarily but non-limitingly include at least one of methylcellulose, hydroxypropyl methylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, hydroxyethyl methylcellulose and hydroxypropylcellulose.

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

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

[0091] The above-mentioned coating method can exemplarily but non-limitingly include at least one of electrostatic spraying method, scraping method, spin coating method, extrusion coating method, transfer coating method, dip coating method, gravure or microgravure coating method.

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

[0093] Among them, the preparation of the carboxylated sepiolite fibers 112 may include: acidifying sepiolite fibers to obtain acid-modified sepiolite fibers; grafting carboxylic acid groups onto the acid-modified sepiolite fibers.

[0094] The preparation of the above-mentioned acid-modified sepiolite fibers may include: performing acid activation treatment on sepiolite fibers with an acid solution; subsequently washing with water and drying.

[0095] In some preferred embodiments, before the acid activation treatment, the sepiolite fibers may be washed to remove impurities first. For example, the sepiolite fiber raw material may be formulated into a suspension, stirred and then dried to obtain the sepiolite fibers after impurity removal.

[0096] In some alternative embodiments, the acid solution used for the acid activation treatment may exemplarily 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 alternative embodiments, the solid-liquid ratio of the sepiolite fibers to the acid solution may be 1 g:10 mL to 10 g:10 mL, such as 1 g:10 mL, 2 g:10 mL, 3 g:10 mL, 4 g:10 mL, 5 g:10 mL, 6 g:10 mL, 7 g:10 mL, 8 g:10 mL, 9 g:10 mL or 10 g:10 mL, etc., and may also be any value or any range within the range of 1 g:10 mL to 10 g:10 mL.

[0098] In some alternative embodiments, the temperature of the acid activation treatment may be 70°C to 90°C (such as 70°C, 75°C, 80°C, 85°C or 90°C, etc.), and the time of the acid activation treatment may be 24 h to 48 h (such as 24 h, 32 h, 40 h or 48 h, etc.).

[0099] The following lists a specific method for preparing acid-modified sepiolite fibers: using deionized water to prepare a 400 g / L suspension of sepiolite fiber raw materials, stirring for 12 h, drying at 100°C for 4 h to obtain the sepiolite fibers after impurity removal; mixing the sepiolite fibers after impurity removal with 1 mol / L hydrochloric acid at a solid-liquid ratio of 1 g:10 mL, pickling at 80°C for 24 h, then washing and filtering with deionized water, and drying at 80°C for 5 h to obtain acid-modified sepiolite fibers.

[0100] The above-mentioned acid-modified sepiolite fibers (such as Figure 3 shown) compared with the sepiolite fibers without acid modification (such as Figure 2Compared with the one shown, the former has a larger specific surface area and a higher degree of sparsity, and can provide more active sites for the formation of metal-organic framework materials.

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

[0102] Among them, the coupling agent solution can exemplarily include at least one of a silane coupling agent solution, a phthalate coupling agent solution, and an aluminate coupling agent solution. In some alternative embodiments, the coupling agent solution can adopt a silane coupling agent solution. Among them, the silane coupling agent can include at least one of KH550, KH792, and KH560, the solvent can be ethanol, and the concentration of the silane coupling agent in the silane coupling agent solution can be 0.2 mol / L.

[0103] The carboxylic acid group-providing solution can exemplarily include at least one of a terephthalic acid solution, a formic acid solution, an acetic acid solution, an oxalic acid solution, and a succinic acid solution. In some alternative embodiments, the carboxylic acid group-providing solution can adopt a terephthalic acid solution. Among them, the solvent can be DMF, and the concentration of terephthalic acid in the terephthalic acid solution can be 0.15 mol / L.

[0104] The above 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 h to 8 h. The solid-liquid ratio in the second immersion stage can be 1:3, and the immersion time can be 4 h to 8 h. After the second immersion stage, the carboxylation of the acid-modified sepiolite fibers is completed to facilitate the subsequent loading of metal-organic framework materials.

[0105] In some alternative embodiments, grafting the metal-organic framework 111 material onto the carboxylated sepiolite fibers 112 can be to dissolve the carboxylated sepiolite fibers 112 and the metal-organic framework preparation raw materials in a solvent at room temperature, age this mixed solution at room temperature for 24 h to 48 h, repeatedly rinse with methanol, perform solid-liquid separation, and dry the solid matter.

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

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

[0108] Exemplarily, the solvent for dissolving the carboxylated sepiolite fiber 112 and the raw materials for preparing the metal lithium organic framework can be a mixed solution of N,N-dimethylformamide (DMF) and ethylene glycol. As an example, the volume ratio of DMF to ethylene glycol can be 2:1.

[0109] As mentioned above, the preparation method of the lithium supplement coating 100 provided by the present invention is simple to operate and the process is easy to control. Among them, the used sepiolite material has rich yield and low price, which is beneficial to reducing the product cost. By grafting the metal organic framework 111 material onto the carboxylated sepiolite fiber 112 to prepare the acid-modified sepiolite fiber composite material 110, the loose and porous structure of the sepiolite fiber and the increased specific surface area after acid modification can provide more active sites for the formation of Li-MOFs. And Li-MOFs have porous channels, which can help free Li + pass through the pores, and Li + through the coordinated movement of ion hopping along the framework edge, provides unique advantages for lithium ion conduction. During the first charge and discharge process of the lithium battery, the introduction of Li-MOF can provide a stable lithium source during the operation of the battery. The carboxylated sepiolite fiber 112 has a slow release effect, and the Li-MOFs adsorbed (grafted) in the carboxylated sepiolite fiber 112 gradually release lithium ions to supplement the lithium ion loss caused by the formation of the SEI film on the negative electrode, so that the SEI film on the negative electrode surface can be quickly and stably formed during the battery cycle, improving the first charge and discharge efficiency of the lithium ion battery and the battery cycle capacity retention rate.

[0110] It should also be emphasized that the Si-OH bonds in the sepiolite fibers and the porous network structure formed by the interlacing of the fibers have strong adsorption properties. After being matched with the ceramic material 120, they can improve the electrolyte wetting performance of the lithium supplement coating 100, which is conducive to improving the energy density, cycle performance, and rate performance of lithium-ion batteries. Moreover, the carboxylated sepiolite fibers 112 and the ceramic material 120 are uniformly mixed and coated on the base film 200, which can form a strong "reinforced concrete" structure, thus facilitating the improvement of the peeling and puncture resistance of the separator. In addition, sepiolite is an inorganic clay material with high stability and good high-temperature resistance. During the heating process, sepiolite gradually releases the zeolite water in the pores and the coordinated water of metal ion coordination. This part of the volatilized water (about 15% of the total mass of sepiolite) can be used as a flame retardant to improve the flame retardant performance of the battery separator, thereby enhancing the safety of lithium-ion batteries.

[0111] Furthermore, the present invention also provides a separator, which includes a base film 200 and a coating disposed on at least one surface of the base film 200, and the coating is the above-mentioned lithium supplement coating 100.

[0112] In some alternative embodiments, the base film 200 may exemplarily but non-limitingly include at least one of a polyolefin separator, a cellulose separator, a polyester separator, a nanofiber non-woven separator, and an aramid separator.

[0113] In some alternative embodiments, the thickness of the separator 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, etc., or any value or any range within the range of 5.5 μm to 25.5 μm. In some relatively typical embodiments, the thickness of the separator is 7.5 μm to 23.5 μm; in some more typical embodiments, the thickness of the separator is 9.5 μm to 20.5 μm.

[0114] In some alternative 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, etc., or any value or any range within the range of 5 μm to 25 μm. In some relatively typical embodiments, the thickness of the base film 200 is 7 μm to 23 μm; in some more typical embodiments, the thickness of the base film 200 is 9 μm to 20 μm.

[0115] In some alternative embodiments, the thickness of the lithium supplement 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, etc., or can be any value or any range within the range of 0.5 μm to 10 μm. In some relatively typical embodiments, the thickness of the lithium supplement coating 100 is 0.5 μm to 8 μm; in some more typical embodiments, the thickness of the lithium supplement coating 100 is 0.5 μm to 5 μm. It should be noted that the sum of the thicknesses of the lithium supplement coating 100 and the base film 200 needs to meet the above-mentioned thickness range of the separator.

[0116] The above-mentioned separator has good electrolyte wetting performance, flame retardant performance, peeling ability, and a small high-temperature shrinkage rate, which is beneficial to improving the safety performance, first charge-discharge efficiency, and cycle life of the battery, etc.

[0117] Furthermore, the present invention also provides a battery, which includes a positive electrode, a negative electrode, and the above-mentioned separator, and the positive electrode and the negative electrode are isolated by the separator.

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

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

[0120] Example 1

[0121] This example provides a lithium supplement coating 100, and its preparation method includes the following steps:

[0122] S1: Prepare acid-modified carboxylated sepiolite fibers 112.

[0123] S11: Use deionized water to prepare a 400 g / L suspension of sepiolite fiber raw materials, stir for 12 h, and then dry at 100 °C for 4 h to obtain the sepiolite fibers after impurity removal.

[0124] Among them, the length of the sepiolite fiber raw materials is 2 μm, and the aspect ratio is 15:1.

[0125] S12: Mix the sepiolite fibers after impurity removal with 1 mol / L hydrochloric acid at a solid-liquid ratio of 1 g:10 mL, perform acid washing at 80 °C for 24 h, then wash and filter with deionized water, and then dry at 80 °C for 5 h to obtain acid-modified sepiolite fibers.

[0126] S2: Prepare acid-modified sepiolite fiber composites 110.

[0127] S21: Immerse the acid-modified sepiolite fibers obtained in S12 in a silane coupling agent solution (the silane coupling agent is specifically KH550, the solvent is ethanol, and the concentration of the silane coupling agent in the silane coupling agent solution is 0.2 mol / L) at a solid-liquid ratio of 1:5 for 8 h. Subsequently, immerse it in a terephthalic acid solution (the solvent is DMF, and the concentration of terephthalic acid in the terephthalic acid solution is 0.15 mol / L) at a solid-liquid ratio of 1:3 for 8 h to obtain carboxylated sepiolite fibers 112.

[0128] S22: Mix the carboxylated sepiolite fibers 112 obtained in S21 with LiClO4·3H2O and 2-methylimidazole at a mass ratio of 0.8:1:1. Subsequently, dissolve them in 500 mL of a mixed solution composed of DMF and ethylene glycol at a volume ratio of 2:1, so that Li-MOFs are grafted onto the carboxylated sepiolite fibers 112. Age this mixed solution at room temperature for 24 h, repeatedly rinse it with methanol, perform solid-liquid separation, and dry the solid matter to obtain acid-modified sepiolite fiber composites 110.

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

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

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

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

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

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

[0135] S4: Prepare a lithium supplement coating 100.

[0136] Use a coating machine to coat the above-mentioned coating slurry on one side surface of a polyethylene film with a thickness of 9 μm, and dry it in an oven at 60 °C for 30 min. After drying, a single-sided coated separator is obtained, and the thickness of the lithium supplement coating 100 in this separator is 2 μm.

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

[0138] Example 2

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

[0140] Example 3

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

[0142] Example 4

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

[0144] Example 5

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

[0146] Example 6

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

[0148] Example 7

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

[0150] Example 8

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

[0152] Example 9

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

[0154] Example 10

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

[0156] Example 11

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

[0158] Example 12

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

[0160] Example 13

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

[0162] Embodiment 14

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

[0164] Embodiment 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] Embodiment 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] Embodiment 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] Embodiment 18

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

[0172] Embodiment 19

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

[0174] Embodiment 20

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

[0176] Embodiment 21

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

[0178] Embodiment 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 example and Example 6 is that the content of the acid-modified sepiolite fiber composite material 110 in the lithium supplement 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 carried out, and S32 is: adding 200 g of boehmite to the aqueous dispersant solution in S31 and stirring at 2000 r / min for 1 h.

[0184] That is, the lithium supplement coating 100 in this comparative example does not contain the 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 is directly grafted with carboxylic acid groups without acid modification.

[0187] Test Example

[0188] The diaphragms obtained from the above 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 methods for each performance test are as follows:

[0190] ①. Method for wettability test: Cut the diaphragm into samples with a length×width of 50 mm×50 mm, and make longitudinal (MD) and transverse (TD) marks. Lay the diaphragm flat on a glass slide and fix the four corners with green tape for testing. Observe the diffusion distance of the liquid droplet after 5 min using a handheld digital microscope. The magnification is 20 times, the volume of a single drop of liquid is 2 μL, and the dropping method is injection with a syringe of 1 mL.

[0191] ②. The contact angle test was carried out with reference to GB / T 30693-2014 Measurement of the Contact Angle of Plastic Films with Water 10.2.

[0192] ③. Method for testing ionic conductivity: Cut 5 diaphragms with a size of 50 mm×50 mm, put the diaphragms into the electrolyte, keep them sealed and soaked for 30 min, and test the alternating current impedance of the soaked diaphragms. Taking the number of diaphragm layers as the abscissa and the diaphragm resistance as the ordinate, find the slope k of the curve, which is the diaphragm impedance value. According to the diaphragm impedance value R, the ionic conductivity σ of the diaphragm can be deduced and calculated.

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

[0194] where d is the thickness of the sample under test (cm); R is the bulk impedance of the sample under test (ohm), which can be obtained from the intersection of the semi-circular arc and the oblique line in the Nyquist diagram of the electrochemical impedance spectrum; S is the effective area of the separator (cm 2 ).

[0195] ④. Method for flame retardancy test: Take a strip-shaped separator with the same size of 1 cm × 5 cm and ignite it with an open flame. Start timing from when the stable open flame source touches the bottom end of the separator sample strip until it is successfully ignited and stop timing. The time consumed to ignite the separator sample strip is called the flame retardancy time.

[0196] ⑤. Method for battery cycle capacity test: Make a soft-pack battery cell with a separator of 86 mm in width, and perform 1000 cycles at 1C at a temperature of 25°C ± 2°C, and record the battery cycle capacity retention rate.

[0197] ⑥. Method for peel strength test: Cut the coated film into samples with a length of 2.5 cm × 30.5 cm. Then peel the samples from the flexible or rigid substrate at an angle of 180 degrees at a separation speed of 152.4 mm / min, and record the test values.

[0198] ⑦. Method for shrinkage rate test: Cut the modified composite separator into a separator with a size of 5 cm × 5 cm and place it in an oven. Keep it at 150°C for 60 min. The method for testing the thermal shrinkage rate refers to the standard of GBT36363-2018. The thermal shrinkage rate of the separator is measured in the longitudinal direction (MD) and the transverse direction (TD) respectively, and then the average value of the thermal shrinkage rates in MD and TD is defined as the thermal shrinkage rate of the separator.

[0199] ⑧. Method for first efficiency test: Perform the formation process on a Neware machine, that is, charge and discharge the battery cell according to the preset charge and discharge program. The capacity during the formation process is recorded as the PIEF capacity.

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

[0201] Rest: After charging is completed, rest the battery cell for a period of time (such as 30 minutes) to ensure that the inside of the battery cell reaches an equilibrium state.

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

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

[0204] Initial efficiency calculation: Calculate the initial efficiency of the battery cell based on the recorded data. The formula for initial efficiency is: Initial discharge capacity / (Initial charge capacity + PIEF capacity) × 100%.

[0205] Table 1 Test Results

[0206]

[0207]

[0208] As can be seen from Table 1, the initial efficiency, wettability, contact angle, separator ionic conductivity, battery cycle capacity retention rate, and peel strength of Examples 1 to 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. And Li-MOFs have porous channels, which can help free Li + pass through the pores, and Li + provides a unique advantage for lithium ion conduction through the cooperative movement of ionic hopping along the framework edge. During the first charge and discharge process of the lithium battery, the introduction of Li-MOF can provide a stable lithium source during the operation of the battery. The carboxylated sepiolite fiber 112 has a slow-release effect, and the Li-MOFs adsorbed (grafted) in the carboxylated sepiolite fiber 112 gradually release lithium ions to supplement the lithium ion loss caused by the formation of the SEI film on the negative electrode, enabling the SEI film on the negative electrode surface to form quickly and stably during the battery cycle, improving the first charge and discharge efficiency of the lithium ion battery and the battery cycle capacity retention rate.

[0209] In addition, through the flame retardancy experimental data, it can be proved that the introduction of nano-sepiolite fibers prolongs the combustion time of the separator and improves the safety performance of the separator. This is because sepiolite is an inorganic clay material with relatively high stability and good high-temperature resistance. During the heating process, sepiolite will gradually release the zeolite water in the pores and the coordinated water of metal ion coordination. This part of the volatilized water (about 15% of the total mass of sepiolite) can act as a flame retardant to improve the flame retardancy of the battery separator, thereby enhancing the safety of the lithium ion battery.

[0210] The thermal shrinkage experiment shows that the appropriate addition of the acid-modified sepiolite fiber composite material 110 in the coating can play a supporting role, but the addition amount should not be too much, otherwise it will affect the adhesion between the adhesive and the ceramic particles, reducing the heat resistance of the coating.

[0211] It can be seen from the comparison between Example 6 and Comparative Example 2 that the ionic conductivity, battery cycling performance, and initial efficiency of Example 6 are all better than those of Comparative Example 2. The reason may be that the acid-modified sepiolite fiber has a larger specific surface area and a higher sparsity compared with the unmodified sepiolite fiber, which can provide more active sites for the formation of the metal-organic framework material, thus facilitating the improvement of the above properties.

[0212] It can be seen from the comparison between Example 6 and Example 18 that the heat resistance, peel strength, and initial efficiency of Example 6 are all better than those of Example 18. The reason may be that the simple acid-modified sepiolite fiber composite material 110 coating cannot effectively adhere to the adhesive, thus affecting the heat resistance of the coating. It should be noted that in Example 18, it is a pure sepiolite composite material, and its flame retardancy is better than that of Example 6. However, since Example 18 does not contain ceramic materials, its areal density will decrease, and due to the fibrous morphology of sepiolite, the contact area with the adhesive is small, which will further affect the supportability of the coating, thus resulting in a decrease in heat resistance.

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

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

[0215] In summary, the lithium supplement coating 100 provided by the present invention has good electrolyte wetting performance and flame retardancy. When a separator is prepared from it and further made into a battery, the battery can have good flame retardancy, high first charge-discharge efficiency, and long cycle life.

[0216] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A lithium supplement coating, characterized in that: The lithium supplement coating contains an acid-modified sepiolite fiber composite material, which includes carboxylated sepiolite fibers and a metal lithium organic framework material grafted onto the carboxylated sepiolite fibers.

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

1.

3. The lithium supplement coating according to claim 1 or 2, characterized in that: The lithium supplement coating also contains ceramic material; 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: D of the ceramic material 50 It is 50nm~5μm.

4. The lithium supplement coating according to claim 3, characterized in that: The lithium supplement coating also contains an additive; The auxiliary agent includes at least one of a dispersant, an adhesive, a wetting agent and a thickener.

5. A method for preparing a lithium supplement coating according to any one of claims 1 to 4, characterized in that: The following steps are involved: The slurry containing the acid-modified sepiolite fiber composite material is applied to at least one surface of the base film and dried.

6. The preparation method according to claim 5, characterized in that: The preparation method of the acid-modified sepiolite fiber composite material comprises: grafting a metal lithium 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 comprises: dissolving carboxylated sepiolite fiber and raw materials for preparing a metal lithium organic framework in a solvent, separating the solid from the liquid, and drying the solid.

8. The preparation method according to claim 7, characterized in that: The raw materials for preparing the metal lithium organic framework include a lithium source and an organic ligand; The lithium source includes at least one of LiClO4·3H2O, Li2CO3 and LiOH; The organic ligand includes 2-methylimidazole 、 At least one of 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 comprises: 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 comprises: performing acid activation treatment on the sepiolite fiber with acid solution; and then washing with water and drying.

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

12. The preparation method according to claim 9, characterized in that: The grafting of carboxylic acid groups comprises: immersing the acid-modified sepiolite fiber in a coupling agent solution, and then immersing the fiber in a carboxylic acid group providing solution.

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

14. A diaphragm, characterized in that: The separator includes a base film and a coating disposed on at least one surface of the base film, and the coating is the lithium-supplementing coating according to 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 5 μm to 25 μm; Feature 19: The thickness of the lithium replenishing coating is 0.5 μm to 10 μm; Feature 20: The base film includes at least one of a polyolefin separator, a cellulose separator, a polyester separator, a nanofiber nonwoven separator, and an aramid separator.

16. A battery, characterized in that: The invention comprises a positive electrode, a negative electrode and the separator according to claim 14 or 15, wherein the positive electrode and the negative electrode are separated by the separator.

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