A composite diaphragm and its preparation method and application

Abstract

The present invention provides a composite membrane, a preparation method, and applications thereof, belonging to the field of membrane technology. The composite membrane comprises a base membrane, a first coating layer disposed on one surface of the base membrane, and a second coating layer disposed on the other surface of the base membrane. The first coating layer comprises inorganic particles and an adhesive; the second coating layer comprises a self-polymerizing microporous polymer; and the ratio of the specific surface area of ​​the second coating layer to the specific surface area of ​​the first coating layer is 10:1 to 200:1. The composite membrane provided by the present invention not only prevents the migration of transition metal ions such as nickel and manganese, but also has high lithium ion transmission efficiency and low impedance.

Description

Technical Field

[0001] The present invention belongs to the technical field of diaphragms and relates to a composite diaphragm and a preparation method and application thereof. Background Art

[0002] The base membranes of the current mainstream lithium-ion battery separators are mainly polypropylene dry-process base membranes and polyethylene wet-process base membranes, which are then matched with ceramic coatings such as alumina and boehmite, or with adhesive coatings such as PVDF. However, the current mainstream lithium-ion battery separators, whether base membranes or coated separators, not only have poor voltage breakdown resistance, but also easily cause the bulky lithium salt anions and unstable transition metal cations (such as Ni) to escape from the positive electrode. 2+ 、Mn 3+ 、Fe 3+ The lithium ion migration number is low, which will also cause the contamination of the negative electrode and the reduction of cycle life.

[0003] In recent years, in order to solve the above problems, research and development of membranes that can only conduct lithium ions and prevent the migration of transition metal ions such as nickel ions and manganese ions are underway. However, although some current membranes can block transition metal ions to a certain extent, they have disadvantages such as high impedance and low lithium ion transmission efficiency.

[0004] Therefore, there is an urgent need to develop a separator that can not only prevent the migration of transition metal ions such as nickel and manganese, but also has high efficiency and low impedance in lithium ion transmission. Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a composite diaphragm and a preparation method and application thereof.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a composite diaphragm, comprising a base film, a first coating layer disposed on one surface of the base film, and a second coating layer disposed on the other surface of the base film;

[0008] The first coating layer includes inorganic particles and an adhesive;

[0009] The second coating comprises a self-polymerizing microporous polymer;

[0010] The ratio of the specific surface area of ​​the second coating layer to the specific surface area of ​​the first coating layer is 10:1 to 200:1.

[0011] In a second aspect, the present invention provides a method for preparing the composite diaphragm according to the first aspect, the preparation method comprising the following steps:

[0012] (1) adding raw materials including inorganic particles and an adhesive into a first solvent and mixing them to obtain a first coating slurry;

[0013] mixing the self-polymerizing microporous polymer with a second solvent to obtain a second coating slurry;

[0014] (2) The first coating slurry and the second coating slurry are respectively placed on two opposite surfaces of the base film, and after drying, the composite diaphragm is obtained.

[0015] In a third aspect, the present invention provides a battery, comprising the composite diaphragm as described in the first aspect or the composite diaphragm obtained according to the preparation method as described in the second aspect.

[0016] Compared with the prior art, the present invention has at least the following beneficial effects:

[0017] The composite diaphragm provided by the present invention can improve the overall wettability of the diaphragm by arranging asymmetric coatings on both sides of the base film, and then by setting the asymmetric specific surface area, during the charging process, the first coating improves the ability of the diaphragm to accommodate the electrolyte, and locally improves the Li + concentration and reduce the energy consumption of its desolvation, while the second coating effectively blocks the penetration of lithium salt anions; during the discharge process, the first coating reduces the transmission resistance of lithium ions and alleviates the concentration polarization phenomenon, while the second coating effectively blocks the penetration of lithium salt anions; therefore, it plays a role in reducing impedance and increasing the number of lithium ion migration; in addition, the second coating can also significantly reduce the penetration concentration of transition metal ions during the use of the battery, avoiding the problem of decreased cycle performance caused by contamination of the negative electrode. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the solutions of the present invention, the present invention is described in further detail below.

[0019] An embodiment of the present invention provides a composite diaphragm, comprising a base film, a first coating layer disposed on one surface of the base film, and a second coating layer disposed on the other surface of the base film.

[0020] The first coating layer includes inorganic particles and an adhesive;

[0021] The second coating comprises a self-polymerizing microporous polymer;

[0022] The ratio of the specific surface area of ​​the second coating layer to the specific surface area of ​​the first coating layer is 10:1 to 200:1, for example, it can be 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1, 100:1, 110:1, 120:1, 130:1, 140:1, 150:1, 160:1, 170:1, 180:1, 190:1, 200:1 or a range consisting of any two thereof.

[0023] In the present invention, the chain segments of the self-polymerized microporous polymer in the second coating layer are staggered to form the microscopic pore structure (ie, nanoscale pores) of the second coating layer, but the second coating layer is substantially non-porous on a macroscopic scale.

[0024] The composite diaphragm provided by the present invention can improve the overall wettability of the diaphragm by arranging asymmetric coatings on both sides of the base film, and then by setting the asymmetric specific surface area, during the charging process, the first coating improves the ability of the diaphragm to accommodate the electrolyte, and locally improves the Li + concentration and reduce the energy consumption of its desolvation, while the second coating effectively blocks the penetration of lithium salt anions; during the discharge process, the first coating reduces the transmission resistance of lithium ions and alleviates the concentration polarization phenomenon, while the second coating effectively blocks the penetration of lithium salt anions; therefore, it plays a role in reducing impedance and increasing the number of lithium ion migration; in addition, the second coating can also significantly reduce the penetration concentration of transition metal ions during the use of the battery, avoiding the problem of decreased cycle performance caused by contamination of the negative electrode.

[0025] If both sides of the composite diaphragm are set as self-polymerized microporous polymer coatings, the diaphragm impedance will be high and the lithium ion transmission efficiency will be low, which will not meet the market's higher requirements for battery fast charging performance.

[0026] If the ratio of the specific surface area of ​​the second coating to the specific surface area of ​​the first coating is lower than 10:1~200:1, the impedance of the charge and discharge process will increase and the barrier effect of lithium salt anions and transition metal ions will be poor, affecting the cycle performance of the battery; if the ratio of the specific surface area of ​​the second coating to the specific surface area of ​​the first coating is higher than 10:1~200:1, the stress imbalance on both sides of the composite diaphragm during the coating process will cause deformation, affecting the electrochemical safety.

[0027] In some embodiments, the first coating has a specific surface area (BET) of 5 m 2 / g~100m 2 / g, for example, 5m 2 / g、10m 2 / g、15m 2 / g, 20m 2 / g, 25m 2 / g、30m 2 / g、35m 2 / g, 40m 2 / g、45m 2 / g, 50m 2 / g、55m 2 / g, 60m 2 / g、65m 2 / g、70m 2 / g、75m 2 / g、80m 2 / g、85m 2 / g、90m 2 / g、95m 2 / g、100m 2 / g or a range consisting of any two thereof.

[0028] In some embodiments, the specific surface area of ​​the second coating is 250 m 2 / g~5000m 2 / g, for example, 250m 2 / g、300m 2 / g, 400m 2 / g、500m 2 / g、600m 2 / g、800m 2 / g、1000m 2 / g、1200m 2 / g、1400m 2 / g、1600m 2 / g、1800m 2 / g、2000m 2 / g、2200m 2 / g、2400m 2 / g、2600m 2 / g、2800m 2 / g、3000m 2 / g、3200m 2 / g、3400m 2 / g、3600m 2 / g、3800m 2 / g、4000m 2 / g、4200m 2 / g、4400m 2 / g、4600m 2 / g、4800m 2 / g、5000m 2 / g or a range consisting of any two thereof.

[0029] The present invention can further reduce the membrane impedance and improve the effect of blocking lithium salt anions and transition metal ions by controlling the specific surface area of ​​the first coating and the second coating within a specific range, while also further improving the heat shrinkage resistance of the composite membrane. In addition, by controlling the specific surface area of ​​the first coating within 5m 2 / g~100m 2 / g range, it can also improve the peel strength of the first coating and reduce its moisture content, thereby improving the electrochemical safety and cycle performance of the diaphragm; by controlling the specific surface area of ​​the second coating to 250m 2 / g~5000m 2 / g range, it will not cause the problem of excessively high cell impedance, and at the same time ensure that the composite diaphragm has sufficient barrier effect on transition metals.

[0030] In the present invention, the test method for the specific surface area of ​​the first coating and the second coating is:

[0031] A resin scraper was used to scrape off debris from the first and second coatings of the composite membrane samples of the present invention. Approximately 0.5-1.0 g of each debris was weighed and placed in a sample tube. Specific surface area was measured using a JW-BK112 surface and pore size analyzer using nitrogen adsorption BET. Pretreatment conditions were 120°C / 30 min, with adsorption pressure settings of 12 kPa intervals and a 15 kPa pressure limit for the first stage and 12 kPa intervals and a 30 kPa pressure limit for the second stage. The BET point selection range was 0.05-0.3, and the thermal delay time was 0.

[0032] The specific surface area of ​​the first coating layer can be adjusted by appropriately varying the structural elements that may be present in the first coating layer. Specifically, the specific surface area can be adjusted by varying the type, particle size, and specific surface area of ​​the inorganic particles; the type and amount of the adhesive; and other additives present in the first coating layer. For example, using larger inorganic particles in the first coating layer can reduce the specific surface area of ​​the first coating layer; while increasing the amount of adhesive can also reduce the specific surface area of ​​the first coating layer.

[0033] In some embodiments, the inorganic particles include ceramic particles and / or inorganic solid electrolyte particles.

[0034] In some embodiments, the decomposition temperature of the ceramic particles is not less than 200°C, for example, it can be 200°C, 250°C, 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C or a range consisting of any two thereof.

[0035] In some embodiments, the ceramic particles include any one of BaTiO3, HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, AlOOH, TiO2, AlN, Si3N4, BN, TiN, SiC, B4C, TiC, or a combination of at least two thereof.

[0036] In some embodiments, the inorganic solid electrolyte particles include any one or a combination of at least two of lithium aluminum titanium phosphate (LATP) particles and their doped modified solid electrolyte particles, lithium aluminum germanium phosphate particles and their doped modified solid electrolyte particles, lithium lanthanum zirconium oxide particles and their doped modified solid electrolyte particles, and lithium lanthanum titanium oxide particles and their doped modified solid electrolyte particles.

[0037] In some embodiments, the doping and modifying elements in the doped and modified solid electrolyte particles include any one of silicon, tantalum, bismuth, iron, yttrium, indium, lutetium, gallium, rubidium, chromium, iron, aluminum, cerium, strontium, germanium, zinc, magnesium, and tungsten, or a combination of at least two thereof.

[0038] The present invention does not particularly limit the average particle size of the inorganic particles, and inorganic particles of any particle size can be used. The inorganic particles preferably have a 50% cumulative value (D50) of particle size in the range of 0.1 μm to 5 μm, for example, 0.1 μm, 0.15 μm, 0.2 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or any combination thereof.

[0039] In some embodiments, the 99th percentile cumulative value D99 of the inorganic particles satisfies the following relationship: 2.5*D50≤D99≤4*D50. Satisfying this relationship facilitates a good particle size distribution in the first coating layer, thereby facilitating a more suitable stacking structure between the inorganic particles, effectively encapsulating the binder and the particles, and providing gap-filling effects, thereby further improving the heat resistance of the separator.

[0040] The present invention does not particularly limit the type of adhesive. For example, the adhesive includes, but is not limited to, any one or a combination of at least two of polyacrylates, polyacrylic acid-polyacrylate copolymers, polyacrylamide copolymers, polyurethane copolymers, polyimide copolymers, polyetherimide copolymers, polyurea copolymers, and styrene-butadiene rubber copolymers. The adhesive can improve the adhesion between the first coating layer and the base film, allowing the first coating layer to adhere more tightly to the surface of the base film.

[0041] In some embodiments, based on the total mass of the first coating, the mass proportion of the inorganic particles is 85% to 98%, for example, it can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or a range consisting of any two of them.

[0042] The present invention does not impose any particular limitation on the percentage by mass of the adhesive, and the added content can be freely selected according to the purpose.

[0043] In some embodiments of the present invention, based on the total mass of the first coating, the mass proportion of the adhesive is 2% to 15%, for example, it can be 2%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, 11%, 12%, 13%, 14%, 15% or a range consisting of any two of them.

[0044] In some embodiments, the first coating layer may further include additives such as dispersants, wetting agents, thickeners, and pH regulators. In the coating slurry used to form the first coating layer, a dispersant is added, for example, for the purpose of improving dispersibility, coating properties, or storage stability. In the coating slurry used to form the first coating layer, a thickener is added, for example, for the purpose of improving storage stability. In the coating slurry used to form the first coating layer, a wetting agent is added, for example, for the purpose of improving coating uniformity. In the coating liquid used to form the first coating layer, a pH regulator is added, for example, for the purpose of adjusting pH.

[0045] The present invention does not particularly limit the type of dispersant. For example, the dispersant can be any one of polyacrylate copolymer sodium salt, polyacrylate copolymer ammonium salt and acidic group-containing alkanol ammonium salt, or a combination of at least two thereof.

[0046] The present invention does not particularly limit the type of thickener. For example, the thickener can be any one or a combination of at least two of sodium carboxymethyl cellulose, fumed silica, modified urea polymers, organic-modified silicates, organic-modified montmorillonites, and organic bentonites.

[0047] The present invention does not particularly limit the type of wetting agent. For example, the wetting agent can be any one of polyether siloxane copolymers, silicone twin structure copolymers, polyacrylate copolymers, polyether modified silicone oil copolymers, alkylphenol polyoxyethylene ethers and polyoxyethylene alkylamine copolymers, or a combination of at least two of them.

[0048] The present invention does not particularly limit the type of pH adjuster. For example, the pH adjuster can be any one of hydrochloric acid, phosphoric acid, sodium citrate, potassium citrate, sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium bicarbonate, and sodium carbonate, or a combination of at least two thereof.

[0049] The present invention does not impose any particular limitation on the mass percentage of the dispersant, thickener, wetting agent, and pH adjuster, and the added content can be freely selected according to the purpose.

[0050] In some embodiments, based on the total mass of the first coating, the mass percentage of each additive such as the dispersant, thickener, wetting agent, pH adjuster, etc. can be 0.1% to 3%, for example, it can be 0.1%, 0.2%, 0.3%, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3% or a range consisting of any two of them.

[0051] The specific surface area of ​​the second coating can be adjusted by appropriately varying the types of structural elements it may contain. For example, increasing the surface roughness of the second coating can increase the specific surface area of ​​the second coating; increasing the volume fraction of microscopic voids in the second coating can also increase the specific surface area of ​​the second coating. Specifically, the specific surface area of ​​the second coating can be controlled by adjusting the process conditions during the second coating preparation process.

[0052] In some embodiments, the self-polymerized microporous polymer includes any one of intrinsically porous polymers (PIMs), conjugated microporous polymers, or hyper-crosslinked polymers, or a combination of at least two thereof. The microporous structure of the self-polymerized microporous polymer can be formed by the rigidity of the polymer molecular chains, which prevent them from being tightly packed, and the self-polymerized microporous polymer appears to be non-porous at a macroscopic level.

[0053] In some embodiments, the intrinsically microporous polymer may include a polymer listed in the following literature: BaranMJ, CarringtonME, SahuS, BaskinA, SongJ, BairdMA, HanKS, MuellerKT,TeatSJ, MecklerSM, FuC, PrendergastD, HelmsBA. Diversity-orientedsynthesis of polymer membranes with ion solvation cages. Nature. 2021 Apr;592(7853):225-231. doi: 10.1038 / s41586-021-03377-7. Epub 2021 Apr 7. PMID:33828319. (BaranMJ, CarringtonME, SahuS, BaskinA, SongJ, BairdMA, HanKS, MuellerKT, TeatSJ, MecklerSM, FuC, PrendergastD, HelmsBA BA. Diversity-guided synthesis of ionic solvatable cage polymer membranes. Nature, 592(7853): 225–231. doi:10.1038 / s41586-021-03377-7. Epub ahead of print April 7, 2021. PMID: 33828319.

[0054] McKeown, NB, Budd, PM, Msayib, K., Ghanem, B., Microporous Polymer Material, US7690514B2, 2010.

[0055] In some embodiments, the intrinsic microporous polymer PIMs include a repeating unit (R AB ):

[0056] Formula (I);

[0057] Wherein, n is an integer between 5 and 10,000;

[0058] A is a monomer segment selected from any one of the following (A), (B), (C), (D), (E), (F), (G), (H), (I) or (j):

[0059] ;

[0060] B is a monomer segment selected from any one of the following (a), (b), (c), (d), (e), (f) or (g):

[0061] ;

[0062] Among them, each R 10 Each independently selected from (C 1-6 ) alkyl or H;

[0063] Each R 11 Each independently selected from -CH2NR1R2 or H;

[0064] Each R 12 Each independently selected from -C(NOR 13 )N(R 14 )2 or -CN;

[0065] R1 and R2 are each independently (C 1-20 ) alkyl, (C 2-20 ) alkenyl, (C 2-20 ) alkynyl, (C 6-12 ) aryl, (C 3-8 ) cycloalkyl, (C 6-12 aryl)-C 1-20 Alkyl, (C 3-8 Cycloalkyl)-C 1-20 Alkyl, (C 1-20 ) heteroalkyl, (C 1-20 ) haloalkyl, (C 1-20 ) haloalkoxy, 3 to 8 membered heterocyclyl, (3 to 8 membered heterocyclyl)-C 1-20 alkyl, 5- to 8-membered heteroaryl, heteroaryl-C 1-20 alkyl.

[0066] In some embodiments, each alkyl, alkenyl, and alkynyl group in R1 and R2 optionally and independently contains one or more heteroatoms independently selected from silicon, chalcogenides, and pnictides, and one or more atoms in R1 and R2 optionally and independently exist in an oxidized form, such as C=O, C=S, N=O, N=S, S=O, or S(O2).

[0067] In some embodiments, R1 and R2 may be optionally and independently substituted with one or more Z1.

[0068] In some embodiments, R1 and R2 can be taken together with the nitrogen atom to which they are attached to form a 3- to 8-membered heterocyclyl or a 5- to 8-membered heteroaryl, each of which is optionally substituted with one or more Z2.

[0069] The Z1 and the Z2 are each independently halogen, -OH, -NO2, -CN, (C 1-20 ) alkyl, (C 2-20 ) alkenyl, (C 2-20 ) alkynyl, (C 6-12 ) aryl, (C 3-8 ) cycloalkyl, (C 6-12 aryl)-C 1-20 Alkyl, (C 1-20 ) heteroalkyl, 3 to 8 membered heterocyclyl, 3 to 8 membered heteroaryl, (C 3-8 Cycloalkyl)-C 1-20 Alkyl, (3 to 8 membered heterocyclyl)-C 1-20 Alkyl, (5- to 8-membered heteroaryl)-C 1-20 Alkyl, (C 1-20 ) haloalkyl, (C 1-20 ) haloalkoxy, -OR6, -SR6, -S(O)R6, -S(O)2R6, SO2NR6NR7, NR6C(O)R7, NR6S(O)2R7, NR6C(O)NR7R8, NR6R7, CO2R6, -C(O)NR6R7 or -C(O)R6;

[0070] R3, R4, R5, R6, R7 and R8 are each independently (C 1-20 ) alkyl, (C 2-20 ) alkenyl, (C 2-20 ) alkynyl, (C 6-12 ) aryl, (C 3-8 ) cycloalkyl, (C 6-12 aryl)-C 1-20 Alkyl, (C 3-8 Cycloalkyl)-C 1-20 Alkyl, (C 1-20 )heteroalkyl, 3 to 8 membered heterocyclyl, (3 to 8 membered heterocyclyl)-C 1-20 alkyl, 5- to 8-membered heteroaryl, or (5- to 8-membered heteroaryl)-C 1-20 alkyl.

[0071] In some embodiments, R4 and R5 together form (C 4-8 ) cycloalkyl, (C 6-12 ) aryl, 4- to 8-membered heterocyclyl, or 5- to 8-membered heteroaryl.

[0072] In some embodiments, R6 and R7 are taken together to form a 4- to 8-membered heterocyclyl or a 5- to 8-membered heteroaryl.

[0073] In some embodiments, R7 and R8 are taken together to form a 4- to 8-membered heterocyclyl or a 5- to 8-membered heteroaryl.

[0074] In some embodiments, each R 13 are independently H, (C 1-20 ) alkyl or (C 3-8 ) cycloalkyl, wherein alkyl and cycloalkyl are optionally and independently substituted with one or more Z3;

[0075] Each Z3 is independently halogen, -NO2, -CN, -OH, -SO3H, -NH2, (C 1-20 ) alkyl, (C 2-20 ) alkenyl, (C 2-20 ) alkynyl, (C 6-12 ) aryl, (C 3-8 ) cycloalkyl, (C 6-12 aryl)-C 1-20 Alkyl, (C 1–20 ) heteroalkyl, 3 to 8 membered heterocyclyl, 5 to 8 membered heteroaryl, (C 3-8 Cycloalkyl)-C 1–20 Alkyl, (5- to 8-membered heteroaryl)-C 1-20 Alkyl, (C 1-20 ) haloalkyl, (C 1-20 ) haloalkoxy, -OR6, -SR6, -S(O)R6, -S(O)2R6, SO2NR6NR7, NR6C(O)R7, NR6S(O)2R7, NR6C(O)NR7R8, NR6R7, CO2R6, -C(O)NR6R7 or -C(O)R6.

[0076] In some embodiments, each R 14 are independently H, (C 1-20 ) alkyl or (C 3-8 ) cycloalkyl.

[0077] In some embodiments, for example, the intrinsic microporous polymer may include an intrinsic microporous polymer PIM-1 (A unit is selected from (A) monomer segment, R 11 H, B unit is selected from (a) monomer segment, R 12 CN), intrinsic microporous polymer PIM-2 (A unit is selected from (A) monomer segment, R 11 H, B unit is selected from (g) monomer segment), intrinsic microporous polymer PIM-C1 (A unit is selected from (j) monomer segment, B unit is selected from (a) monomer segment, R 12CN), pyridine-based intrinsic microporous polymer PIM-py (A unit is selected from (A) monomer segment, R 11 H, B unit is selected from (b) monomer segment, R 12 CN), cyclotricatechin-based self-microporous polymer (CTC-network-PIM), hexachlorohexaazatrinathyl self-microporous polymer (HATN-network-PIM), or a combination of at least two thereof.

[0078] In some embodiments, the conjugated microporous polymer includes any one or a combination of at least two of tetrakis[4-(9H-carbazol-9-yl)phenyl]methane conjugated microporous polymer (TPTCz-CMP), 1,3,5-tris(2-thienyl)-phenyl conjugated microporous polymer (TTB-CMP), 1,1,2,2-tetrakis(4-(9H-carbazol-9-yl)-[1,1'-biphenyl]-4-yl)vinyl conjugated microporous polymer (TPECz-CMP), and poly(1,3,5-triethynylbenzene) conjugated microporous polymer (PTEB-CMP).

[0079] In some embodiments, the hypercrosslinked polymer comprises polylactic acid-poly(4-vinylbenzyl chloride-co-divinylbenzene) hypercrosslinked polymer [PLA-b-poly(VBzCl-co-DVB)] and / or hypercrosslinked polyaniline.

[0080] The present invention does not particularly limit the thickness of the first coating layer and the second coating layer, and any coating thickness can be selected. However, based on comprehensive consideration of the membrane impedance, heat resistance, and barrier effect, the thickness of the first coating layer is preferably 0.5 μm to 4 μm, for example, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, or a range consisting of any two thereof; the thickness of the second coating layer is preferably 0.1 μm to 4 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, or a range consisting of any two thereof.

[0081] In the present invention, the surface of the base film refers to the two surfaces of the base film that have the largest area and are arranged opposite to each other.

[0082] The present invention does not particularly limit the base film, and the base film may be a porous film commonly used in the art. For example, the base film may be a polyolefin porous film.

[0083] The polyolefin porous membrane may be a polyethylene porous membrane, a polypropylene porous membrane, or a polyethylene-polypropylene multilayer composite porous membrane. A polyethylene-polypropylene multilayer composite porous membrane refers to a multilayer composite porous membrane formed by stacking polypropylene (PP) and polyethylene (PE) in any order, for example, a PP-PE-PP three-layer composite porous membrane, a PP-PE two-layer composite porous membrane, or a PP-PP-PE-PP four-layer composite porous membrane.

[0084] The thickness of the polyolefin porous membrane is not particularly limited in the present invention. Based on the considerations of mechanical strength and internal resistance, the thickness is preferably between 1 μm and 5000 μm, more preferably between 5 μm and 20 μm. For example, the thickness may be in the range of 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, 20 μm, or any two thereof.

[0085] The present invention is not particularly limited to the average pore size and porosity of polyolefin porous membrane, but based on the viewpoint of mechanical strength, ion permeability and electrochemical safety, preferably with a porosity between 30% and 65%, for example, can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65% or the scope of any two of them; Average pore size is preferably in the range of 20nm~100nm, for example, can be 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm or the scope of any two of them. In addition, the pore structure of polyolefin porous membrane is formed by the interlaced connection of some protofibrils, and protofibril is that polymer is formed through stretching orientation in the preparation process, and the preparation method of polyolefin porous membrane is not particularly limited, for example, can be stretching pore forming method, phase separation method etc.

[0086] In some embodiments, the present invention provides a method for preparing the composite membrane, comprising the following steps:

[0087] (1) adding raw materials including inorganic particles and an adhesive into a first solvent and mixing them to obtain a first coating slurry;

[0088] mixing the self-polymerizing microporous polymer with a second solvent to obtain a second coating slurry;

[0089] (2) The first coating slurry and the second coating slurry are respectively placed on two opposite surfaces of the base film, and after drying, the composite diaphragm is obtained.

[0090] In some embodiments, the first solvent comprises water and / or ethanol.

[0091] In some embodiments, the second solvent includes any one or a combination of at least two of tetrahydrofuran, dichloromethane, N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), and chloroform.

[0092] In some embodiments, at least one of a dispersant, a wetting agent, and a thickener may be added to the first coating slurry in step (1).

[0093] In some embodiments, the preparation process of the first coating slurry in step (1) may further include: adding a dispersant to the first solvent, stirring and dispersing for 10 to 60 minutes (for example, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes or a range consisting of any two thereof); then adding inorganic particles, continuing to stir and disperse for 10 to 240 minutes (for example, 10 minutes, 30 minutes, 60 minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes, 210 minutes, 240 minutes or a range consisting of any two thereof); then adding an adhesive, stirring and dispersing for 10 to 180 minutes (for example, 10 minutes, 30 minutes, 60 minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes or a range consisting of any two thereof); then adding a thickener, stirring and dispersing for 10 to 60 minutes (for example, 10 minutes, 20 minutes, 30 minutes, 60 minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes or a range consisting of any two thereof); n, 30min, 40min, 50min, 60min or a range consisting of any two thereof); finally, a wetting agent is added and stirred and dispersed for 10 to 60min (for example, 10min, 20min, 30min, 40min, 50min, 60min or a range consisting of any two thereof) to obtain a first coating slurry; the rotation speed of the above-mentioned stirring and dispersing can be independently 1000 to 5000r / min (for example, 1000r / min, 1500r / min, 2000r / min, 2500r / min, 3000r / min, 3500r / min, 4000r / min, 4500r / min, 5000r / min or a range consisting of any two thereof), and the solid content of the first coating slurry can be ≤50%, for example, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10% or a range consisting of any two thereof.

[0094] In some embodiments, the preparation process of the second coating slurry in step (1) may further include: dissolving the self-polymerizing microporous polymer in a second solvent, mechanically stirring the mixture at a speed of 50 rpm to 70 rpm (e.g., 50 rpm, 55 rpm, 60 rpm, 65 rpm, 70 rpm, or a range consisting of any two thereof) for 7 h to 9 h (e.g., 7 h, 7.5 h, 8 h, 8.5 h, 9 h, or a range consisting of any two thereof) to obtain a homogeneous solution, wherein the concentration range of the homogeneous solution (solid content of the slurry) is controlled to be 0.2% to 2.5%, e.g., 0.2%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.3%, 1.5%, 2%, 2.5%, or a range consisting of any two thereof. By controlling the concentration range of the homogeneous solution (i.e., the solid content of the second coating slurry), it is beneficial to control the density and loading amount of the second coating layer, thereby further better controlling the specific surface area of ​​the second coating layer.

[0095] In some embodiments, step (2) specifically includes: first applying a first coating slurry to one surface of the base film, drying the slurry, then applying a second coating slurry to the other surface of the base film, and drying the slurry to obtain the composite membrane;

[0096] Alternatively, the second coating slurry may be applied to one surface of the base film first, and then dried, and then the first coating slurry may be applied to the other surface of the base film, and then dried to obtain the composite diaphragm.

[0097] Alternatively, the first coating slurry and the second coating slurry may be applied to two opposite surfaces of the base film at the same time, and then dried to obtain the composite diaphragm.

[0098] In some embodiments, the preparation method of the first coating in step (2) includes adopting a slot extrusion coating process or a micro-gravure coating process, but the present invention does not limit the specific preparation process parameters.

[0099] In some embodiments, the preparation method of the second coating in step (2) includes adopting a slit extrusion coating process or a micro-gravure coating process, but the present invention does not limit the specific preparation process parameters. For example, the relative humidity range RH of the coating area of ​​the second coating is 30%~60%, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60% or a range consisting of any two thereof. By controlling the relative humidity of the coating area of ​​the second coating, it is beneficial to control the surface roughness of the second coating and the apparent stacking structure of the coating, thereby further better controlling the specific surface area of ​​the second coating.

[0100] The present invention does not limit the process parameters such as the drying temperature, drying air volume, and drying time of the first coating and the second coating, and can be selected according to the commonly used process parameters in the field, as long as the coating can be dried and cured without destroying the coating structure. In order to better ensure the specific surface area and structural stability of the coating, for example, the drying temperature is 20°C to 50°C, for example, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C or a range of any two thereof, and the drying time is 10s to 80s, for example, 10s, 15s, 20s, 25s, 30s, 35s s, 40s, 45s, 55s, 60s, 65s, 70s, 75s, 80s or a range consisting of any two thereof, and the drying air volume is 0-10 cubic meters / min, for example, 0 cubic meters / min, 0.5 cubic meters / min, 1 cubic meter / min, 2 cubic meters / min, 2.5 cubic meters / min, 3.5 cubic meters / min, 4 cubic meters / min, 5 cubic meters / min, 6 cubic meters / min, 7 cubic meters / min, 8 cubic meters / min, 9 cubic meters / min, 10 cubic meters / min or a range consisting of any two thereof.

[0101] In some embodiments, the present invention provides a battery, comprising the composite separator as described above or the composite separator obtained according to the preparation method as described above.

[0102] In some embodiments, the battery comprises a lithium-ion battery.

[0103] In some embodiments, in specific applications, the first coating is arranged on the positive electrode side of the battery, and the second coating is arranged on the negative electrode side of the battery. Through this arrangement, the first coating facing the positive electrode has a lower specific surface area and the second coating has a higher specific surface area, forming a morphology with decreasing pore space from the positive electrode to the negative electrode, so that the lithium ions maintain a higher concentration at the positive terminal and reduce the transmission resistance while having a better barrier effect at the negative terminal, thereby ensuring the barrier effect of other ions while improving the lithium ion transmission efficiency and reducing impedance.

[0104] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0105] Unless otherwise specified, the base membrane used in the examples and comparative examples of the present invention is a polyethylene microporous membrane (made by Xingyuan, model: SW509C+) with a thickness of 9 μm and a porosity of 42%.

[0106] Example 1

[0107] In this embodiment, a composite membrane is provided, comprising a base membrane, a first coating layer disposed on one surface of the base membrane, and a second coating layer disposed on the other surface of the base membrane.

[0108] The first coating layer includes inorganic particles, an adhesive, a dispersant, a wetting agent, and a thickener;

[0109] The second coating comprises a self-polymerizing microporous polymer;

[0110] Among them, the inorganic particles are AlOOH (Shandong Guoci, D50 particle size is 0.6μm, D99 particle size is 2μm); the adhesive is polyacrylic acid-polyacrylate copolymer (Gao Rui, model: GR401); the dispersant is ammonium polyacrylate (brand DP03, manufacturer Beijing Xidema); the wetting agent is alkylphenol polyoxyethylene ether (brand NP-10, manufacturer Jinan Shunwang); the thickener is sodium carboxymethyl cellulose (weight average molecular weight is 100,000);

[0111] Taking the mass of the first coating as 100%, the mass of the inorganic particles accounts for 94%, the mass of the adhesive accounts for 4.6%, the mass of the dispersant accounts for 0.50%, the mass of the wetting agent accounts for 0.1%, and the mass of the thickener accounts for 0.80%;

[0112] The self-polymerized microporous polymer was the intrinsic microporous polymer PIM-1 (Beijing Huawei Rayke).

[0113] The preparation method comprises the following steps:

[0114] (1) Dispersing inorganic particles, adhesive, dispersant, wetting agent and thickener in a first solvent and stirring uniformly to obtain a first coating slurry with a solid content of 35%;

[0115] The self-polymerized microporous polymer was dissolved in the second solvent and mechanically stirred at 60 rpm for 8 h to obtain a second coating slurry with a concentration (slurry solid content) of 1.2%;

[0116] (2) placing the first coating slurry and the second coating slurry on two opposite surfaces of the base film respectively, and drying them, wherein the drying conditions include: drying temperature of 30° C., drying air volume of 2.5 cubic meters / min, and drying time of 50 seconds, to obtain the composite diaphragm;

[0117] The first solvent is water; the second solvent is a mixed solvent of tetrahydrofuran and dichloromethane in a mass ratio of 1:1, and the relative humidity of the coating area of ​​the second coating is 48%.

[0118] In this embodiment, a battery is further provided. The preparation of the battery includes the following steps:

[0119] 1) Add the positive electrode active material nickel-cobalt-manganese ternary material (nickel-cobalt-manganese mass ratio = 8:1:1), the conductive agent conductive carbon black SP, and the binder PVDF in a mass ratio of 90:3:3 to the solvent NMP and mix well to form a positive electrode slurry, which is then coated on a 10μm aluminum foil current collector; then dry in an oven at 95°C and roll-press on a roller press to obtain a positive electrode sheet for later use.

[0120] 2) Add artificial graphite (negative electrode active material), acetylene black (conductive agent), and SBR (binder) into water at a mass ratio of 90:5:5 and disperse evenly to form a negative electrode slurry. The slurry is then coated onto a 10 μm thick copper foil current collector. The slurry is then dried in an oven at 85°C and rolled on a roller press to obtain a negative electrode sheet for later use.

[0121] 3) The composite separator is placed between the positive electrode sheet and the negative electrode sheet for stacking and packaging, wherein the first coating of the composite separator faces the positive electrode sheet and the second coating faces the negative electrode sheet, and then the electrolyte is injected to obtain a battery.

[0122] The electrolyte used has the following composition: 1 mol / L LiPF6 electrolyte, that is, the electrolyte includes lithium salt LiPF6, and the concentration of the lithium salt is 1 mol / L, and the electrolyte includes a solvent (EC:EMC:DEC (volume ratio) = 1:1:1).

[0123] The performance test of the composite diaphragm and battery provided above is carried out as follows:

[0124] (1) Specific surface area of ​​the coating: the test method is as described in the above specific implementation method section.

[0125] (2) Air permeability: The air permeability of the composite membrane is obtained by referring to the method specified in the national standard GB / T 36363-2018 "Polyolefin separators for lithium-ion batteries".

[0126] (3) Thermal shrinkage rate: The thermal shrinkage rates of the composite membrane in the MD direction (longitudinal direction) and TD direction (transverse direction) were obtained according to the method specified in the national standard GB / T 36363-2018 "Polyolefin separators for lithium-ion batteries", and the average value was taken as the thermal shrinkage rate of the composite membrane; wherein, the heat treatment temperature of the oven was 150°C and the heat treatment time was 1 h.

[0127] (4) Surface resistance: Cut 4 composite membrane samples with a diameter of 45 mm on a flat surface, immerse the samples in an electrolyte (1 mol / L LiPF6 electrolyte, the solvent is EC, EMC and DMC with a volume ratio of 1:1:1) and seal and immerse for 30 min; pour the above electrolyte into the surface resistance test fixture; place 1, 2, 3, and 4 membranes in the fixture for testing respectively; use the number of membrane layers as the horizontal axis and the membrane resistance as the vertical axis to make a linear fit, and calculate the slope and fit of the straight line. When the fit is greater than 0.999, the slope is the surface resistance of the membrane, and the unit is ohm Ω·cm 2 .

[0128] (5) Mn 3+ Transmission concentration (1h): H-type electrolytic cell is used to test transition metal ions Mn 3+ The transmittance of Mn 3+ The specific test method for the permeation concentration after 1 hour includes the following steps:

[0129] In a glove box, a glass H-type electrolytic cell was used, with the left side for high-concentration measurement (simulating positive electrode measurement) connected to the counter electrode (Pt wire), the right side for low-concentration measurement (simulating negative electrode side) and connected to the working electrode (glass carbon) and reference electrode (lithium wire), and a 10cm diameter circular diaphragm sample in the middle, with the diaphragm facing the same direction as in the battery; equal amounts of electrolyte (1 mol / L LiPF6 electrolyte, solvents are EC, EMC and DMC with a volume ratio of 1:1:1) were added to both sides before the test. Acetylacetonate manganese (III) salt was added to the left side and stirred to dissolve, so that the left side Mn 3+ The concentration is 50mmol / L, then add LiPF6 to the right side and stir to dissolve it. + The concentration is 150mmol / L. The three electrodes are connected to the electrochemical workstation and CV test is performed at a rate of 0.2V / s in the range of 4.0V~1.5V. After 1 hour from the start of the test, 5mL of liquid sample is taken from the right side and digested with acid to measure Mn using ICP. 3+ concentration.

[0130] (6) Cycle performance: The battery's 100th cycle capacity retention rate at 25°C is taken as the cycle performance result. The specific test method includes the following steps: charging at a constant current and constant voltage of 0.8C, discharging at a constant current of 1C, measuring the first-round discharge capacity, cycling 100 times under this condition, testing the discharge capacity after 100 cycles, and calculating the ratio of the discharge capacity after 100 cycles to the first-round discharge capacity as the capacity retention rate after 100 cycles at 25°C.

[0131] The performance test results are shown in Table 1 and Table 2.

[0132] Examples 2-16, Comparative Examples 1-4

[0133] The difference between Examples 2-16 and Comparative Examples 1-4 and Example 1 is that at least one of the type and / or particle size of the inorganic particles, the type of self-polymerizing microporous polymer, the coating process parameters (such as the solid content of the coating slurry, humidity, etc.), and the coating thickness is different, as shown in Table 1; the preparation method of the battery, the composite separator, and the battery testing method are the same as in Example 1, and the test results are shown in Table 2.

[0134] Table 1

[0135]

[0136] In Table 1, the alumina in Example 13 was purchased from Shandong Guoci; the PIM-py in Example 14 was purchased from Sigma-Aldrich; the γ-phase nano-alumina in Comparative Example 3 was porous particles purchased from Jiangsu Jingjing New Materials, model: WAY-8902; the PVDF used in Comparative Example 4 was purchased from Arkema, with a weight-average molecular weight of 40W, and the second solvent used was N-methylpyrrolidone (NMP).

[0137] Table 2

[0138]

[0139] It can be seen from Table 2 that the composite membrane provided by the present invention can not only prevent the migration of transition metal ions (Mn 3+ The permeation concentration is below 0.45mmol / L, preferably below 0.3mmol / L), and the lithium ion transmission efficiency is high and the impedance is low (surface resistance: 2.5Ω·cm 2 Below, preferably 2Ω·cm 2 Below), and has good heat resistance (heat shrinkage rate: 4% or less, preferably 3.5% or less), and is used in batteries, so that the batteries have good cycle performance (92% or more, preferably 95% or more).

[0140] Compared with Example 1, the BET ratio of the second coating layer to the first coating layer of the composite diaphragm provided in Comparative Example 1 is higher than 200:1, the surface resistance of the composite diaphragm is significantly increased, and the cycle performance of the battery is greatly reduced; the coating layers on both sides of the composite diaphragm provided in Comparative Example 2 are both inorganic coating layers, and the ability of the composite diaphragm to prevent the migration of transition metal ions is reduced; the coating layers on both sides of the composite diaphragm provided in Comparative Example 3 are both polymer coating layers, the thermal shrinkage rate and surface resistance of the composite diaphragm are significantly increased, and the cycle performance of the battery is greatly reduced; Comparative Example 4 is an existing PVDF coating, and the specific surface area of ​​the second coating layer of the composite diaphragm obtained cannot reach 250~5000m 2 / g, the BET ratio of the second coating to the first coating does not meet 10-200, and the thermal shrinkage rate and the ability to prevent the migration of transition metal ions of the composite membrane are significantly reduced.

[0141] The applicant declares that the present invention uses the above-mentioned embodiments to illustrate the composite diaphragm, its preparation method, and its application. However, the present invention is not limited to the above-mentioned embodiments, which does not mean that the present invention must rely on the above-mentioned embodiments in order to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacements for various raw materials in the product of the present invention, addition of auxiliary components, and selection of specific methods, etc., are all within the scope of protection and disclosure of the present invention.

Claims

1. A composite diaphragm, characterized in that: The composite diaphragm includes a base film, a first coating layer provided on one surface of the base film, and a second coating layer provided on the other surface of the base film; The first coating layer includes inorganic particles and an adhesive; The second coating comprises a self-polymerizing microporous polymer; The ratio of the specific surface area of ​​the second coating layer to the specific surface area of ​​the first coating layer is 20:1 to 200:1; The specific surface area of ​​the first coating is 5m 2 / g~100m 2 / g, the specific surface area of ​​the second coating is 250m 2 / g~5000m 2 / g; In a specific application, the first coating is disposed on the positive electrode side of the battery, and the second coating is disposed on the negative electrode side of the battery.

2. The composite diaphragm according to claim 1, characterized in that The self-polymerized microporous polymer includes any one of an intrinsic microporous polymer, a conjugated microporous polymer or a hyper-crosslinked polymer, or a combination of at least two thereof.

3. The composite diaphragm according to claim 2, characterized in that The intrinsic microporous polymer comprises a repeating unit represented by the following formula (I): Formula (I); Wherein, n is an integer between 5 and 10,000; A is a monomer segment selected from any one of the following (A), (B), (C), (D), (E), (F), (G), (H), (I) or (j): ； B is a monomer segment selected from any one of the following (a), (b), (c), (d), (e), (f) or (g): ； Among them, each R 10 Each independently selected from (C 1-6 ) alkyl or H; Each R 11 Each independently selected from -CH2NR1R2 or H; Each R 12 Each independently selected from -C(NOR 13 )N(R 14 )2 or -CN; R1 and R2 are each independently (C 1-20 ) alkyl, (C 2-20 ) alkenyl, (C 2-20 ) alkynyl, (C 6-12 ) aryl, (C 3-8 ) cycloalkyl, (C 6-12 aryl)-C 1-20 Alkyl, (C 3-8 Cycloalkyl)-C 1-20 Alkyl, (C 1-20 ) heteroalkyl, (C 1-20 ) haloalkyl, (C 1-20 ) haloalkoxy, 3 to 8 membered heterocyclyl, (3 to 8 membered heterocyclyl)-C 1-20 alkyl, 5- to 8-membered heteroaryl, heteroaryl-C 1-20 alkyl; or, each alkyl, alkenyl and alkynyl group in R1 and R2 optionally and independently contains one or more heteroatoms independently selected from silicon, chalcogenides and pnictides, and one or more atoms in R1 and R2 are optionally and independently present in an oxidized form; or R1 and R2 may be optionally and independently substituted with one or more Z1; or, R1 and R2 may be taken together with the nitrogen atom to which they are attached to form a 3- to 8-membered heterocyclyl or a 5- to 8-membered heteroaryl, each of which is optionally substituted with one or more Z2; The Z1 and the Z2 are each independently halogen, -OH, -NO2, -CN, (C 1-20 ) alkyl, (C 2-20 ) alkenyl, (C 2-20 ) alkynyl, (C 6-12 ) aryl, (C 3-8 ) cycloalkyl, (C 6-12 aryl)-C 1-20 Alkyl, (C 1-20 ) heteroalkyl, 3 to 8 membered heterocyclyl, 3 to 8 membered heteroaryl, (C 3-8 Cycloalkyl)-C 1-20 Alkyl, (3 to 8 membered heterocyclyl)-C 1-20 Alkyl, (5- to 8-membered heteroaryl)-C 1-20 Alkyl, (C 1-20 ) haloalkyl, (C 1-20 ) haloalkoxy, -OR6, -SR6, -S(O)R6, -S(O)2R6, SO2NR6NR7, NR6C(O)R7, NR6S(O)2R7, NR6C(O)NR7R8, NR6R7, CO2R6, -C(O)NR6R7 or -C(O)R6; R3, R4, R5, R6, R7 and R8 are each independently (C 1-20 ) alkyl, (C 2-20 ) alkenyl, (C 2-20 ) alkynyl, (C 6-12 ) aryl, (C 3-8 ) cycloalkyl, (C 6-12 aryl)-C 1-20 Alkyl, (C 3-8 Cycloalkyl)-C 1-20 Alkyl, (C 1-20 )heteroalkyl, 3 to 8 membered heterocyclyl, (3 to 8 membered heterocyclyl)-C 1-20 alkyl, 5- to 8-membered heteroaryl, or (5- to 8-membered heteroaryl)-C 1-20 alkyl; Each R 13 Each independently is H, (C 1-20 ) alkyl or (C 3-8 ) cycloalkyl, wherein alkyl and cycloalkyl are optionally and independently substituted with one or more Z3; Each Z3 is independently halogen, -NO2, -CN, -OH, -SO3H, -NH2, (C 1-20 ) alkyl, (C 2-20 ) alkenyl, (C 2-20 ) alkynyl, (C 6-12 ) aryl, (C 3-8 ) cycloalkyl, (C 6-12 aryl)-C 1-20 Alkyl, (C 1–20 ) heteroalkyl, 3 to 8 membered heterocyclyl, 5 to 8 membered heteroaryl, (C 3-8 Cycloalkyl)-C 1–20 Alkyl, (5- to 8-membered heteroaryl)-C 1-20 Alkyl, (C 1-20 ) haloalkyl, (C 1-20 ) haloalkoxy, -OR6, -SR6, -S(O)R6, -S(O)2R6, SO2NR6NR7, NR6C(O)R7, NR6S(O)2R7, NR6C(O)NR7R8, NR6R7, CO2R6, -C(O)NR6R7 or -C(O)R6; Each R 14 Each independently is H, (C 1-20 ) alkyl or (C 3-8 ) cycloalkyl.

4. The composite diaphragm according to claim 2, characterized in that The intrinsic microporous polymer includes any one or a combination of at least two of the intrinsic microporous polymer PIM-1, intrinsic microporous polymer PIM-2, intrinsic microporous polymer PIM-C1, pyridine-based intrinsic microporous polymer PIM-py, cyclotricatechin-based intrinsic microporous polymer, and hexachlorohexaazatrinathyl-based intrinsic microporous polymer; The conjugated microporous polymer includes any one or a combination of at least two of tetrakis[4-(9H-carbazol-9-yl)phenyl]methane conjugated microporous polymer, 1,3,5-tris(2-thienyl)-phenyl conjugated microporous polymer, 1,1,2,2-tetrakis(4-(9H-carbazol-9-yl)-[1,1'-biphenyl]-4-yl)vinyl conjugated microporous polymer, and poly(1,3,5-triethynylbenzene) conjugated microporous polymer; The hyper-crosslinked polymer includes polylactic acid-poly(4-vinylbenzyl chloride-co-divinylbenzene) hyper-crosslinked polymer and / or hyper-crosslinked polyaniline.

5. The composite diaphragm according to claim 1, characterized in that The inorganic particles include ceramic particles and / or inorganic solid electrolyte particles.

6. The composite diaphragm according to claim 5, characterized in that The decomposition temperature of the ceramic particles is not less than 200°C; The ceramic particles include any one or a combination of at least two of BaTiO3, HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, SiO2, Y2O3, Al2O3, AlOOH, TiO2, AlN, Si3N4, BN, TiN, SiC, B4C, and TiC; The inorganic solid electrolyte particles include any one or a combination of at least two of lithium aluminum titanium phosphate particles and doped modified solid electrolyte particles thereof, lithium aluminum germanium phosphate particles and doped modified solid electrolyte particles thereof, lithium lanthanum zirconium oxide particles and doped modified solid electrolyte particles thereof, and lithium lanthanum titanium oxide particles and doped modified solid electrolyte particles thereof; The doping and modifying elements in the doped and modified solid electrolyte particles include any one of silicon, tantalum, bismuth, iron, yttrium, indium, lutetium, gallium, rubidium, chromium, iron, aluminum, cerium, strontium, germanium, zinc, magnesium, and tungsten, or a combination of at least two thereof.

7. The composite diaphragm according to claim 1, characterized in that The thickness of the first coating layer is 0.5 μm to 4 μm, and the thickness of the second coating layer is 0.1 μm to 4 μm.

8. A method for preparing a composite diaphragm according to claim 1, characterized in that: The preparation method comprises the following steps: (1) adding raw materials including inorganic particles and an adhesive into a first solvent and mixing them to obtain a first coating slurry; mixing the self-polymerizing microporous polymer with a second solvent to obtain a second coating slurry; (2) The first coating slurry and the second coating slurry are respectively placed on two opposite surfaces of the base film, and after drying, the composite diaphragm is obtained.

9. The preparation method according to claim 8, characterized in that The first solvent includes water and / or ethanol; The second solvent includes any one of tetrahydrofuran, dichloromethane, N-methylpyrrolidone, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethylacetamide, and chloroform, or a combination of at least two thereof.

10. A battery, characterized in that: The battery comprises the composite separator according to any one of claims 1 to 7 or the composite separator obtained according to the preparation method according to claim 8 or 9.

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