Composite diaphragm as well as preparation method and application thereof

Abstract

The invention provides a composite diaphragm and a preparation method and application thereof, and belongs to the technical field of diaphragms.The composite diaphragm comprises a base diaphragm, a first coating arranged on the surface of one side of the base diaphragm and a second coating arranged on the surface of the other side of the base diaphragm; the first coating comprises inorganic particles and an adhesive; the second coating comprises a self-polymerization microporous polymer; the ratio of the specific surface area of the second coating to the specific surface area of the first coating is (10: 1)-(200: 1). The composite diaphragm provided by the invention not only can prevent the migration of transition metal ions such as nickel and manganese, but also has relatively 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, a preparation method thereof and an application thereof. Background Art

[0002] At present, the base films of the mainstream lithium-ion battery diaphragms are mainly dry-process base films made of polypropylene and wet-process base films made of polyethylene, and are further combined with ceramic coatings such as alumina and boehmite, or combined with adhesive coatings such as PVDF. However, for the current mainstream lithium-ion battery diaphragms, whether they are base films or coated diaphragms, not only the voltage breakdown resistance performance is not ideal, but also large-sized lithium salt anions and transition metal cations (such as Ni 2+ , Mn 3+ , Fe 3+ etc.) that are unstably released from the positive electrode can easily pass through, resulting in a low lithium ion transference number, and also causing problems of negative electrode contamination and reduced cycle life.

[0003] In recent years, in order to solve the above problems, research and development of diaphragms that can only conduct lithium ions and prevent the migration of transition metal ions such as nickel ions and manganese ions has been underway. However, although some current diaphragms 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 diaphragm that can not only prevent the migration of transition metal ions such as nickel and manganese, but also has a high lithium ion transmission efficiency and low impedance. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a composite diaphragm, a preparation method thereof and an application thereof.

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

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

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

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

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

[0011] In a second aspect, the present invention provides a preparation method of the composite diaphragm as described in the first aspect, and the preparation method comprises the following steps:

[0012] (1)Add raw materials including inorganic particles and adhesives to a first solvent and mix to obtain a first coating slurry;

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

[0014] (2)Dispose the first coating slurry and the second coating slurry on two opposite surfaces of a base film respectively, and after drying, obtain the composite separator.

[0015] In a third aspect, the present invention provides a battery, which includes the composite separator as described in the first aspect or includes a composite separator 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] For the composite separator provided by the present invention, by disposing asymmetric coatings on both sides of the base film, the overall wettability of the separator can be improved. Then, through the asymmetric specific surface area setting, during the charging process, the first coating improves the ability of the separator to accommodate the electrolyte, locally increases the Li + concentration and reduces the energy consumption of its desolvation. At the same time, the second coating effectively blocks the permeation of lithium salt anions; during the discharging process, the first coating reduces the transmission resistance of lithium ions and alleviates the concentration polarization phenomenon. At the same time, the second coating effectively blocks the permeation of lithium salt anions; therefore, it plays a role in reducing the impedance and increasing the lithium ion transference number; in addition, the second coating can also significantly reduce the permeation concentration of transition metal ions during the use of the battery, avoiding the problem of the decline in cycle performance caused by its contamination of the negative electrode. Detailed Embodiments

[0018] To enable those skilled in the art to better understand the solution of the present invention, the present invention will be further described in detail below.

[0019] An embodiment of the present invention provides a composite separator, which includes a base film, a first coating disposed on one surface of the base film, and a second coating disposed on the other surface of the base film;

[0020] The first coating includes inorganic particles and adhesives;

[0021] The second coating includes a self-polymerized microporous polymer;

[0022] The ratio of the specific surface area of the second coating to that of the first coating 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 the range composed of any two of them.

[0023] In the present invention, the segments of the self - polymerized microporous polymer in the second coating are interlaced to form the microscopic pore structure (i.e., nanoscale pores) of the second coating, but macroscopically it appears to be basically pore - free.

[0024] The composite separator provided by the present invention can improve the overall wettability of the separator by setting asymmetric coatings on both sides of the base film. Then, through the asymmetric specific surface area setting, during the charging process, the first coating improves the ability of the separator to accommodate the electrolyte, locally increases the Li + concentration and reduces the energy consumption of its desolvation. At the same time, the second coating effectively blocks the permeation of lithium salt anions; during the discharging process, the first coating reduces the transmission resistance of lithium ions, alleviates the concentration polarization phenomenon, and at the same time the second coating effectively blocks the permeation of lithium salt anions; thus, it plays the role of reducing impedance and increasing the lithium ion transference number; in addition, the second coating can also significantly reduce the permeation concentration of transition metal ions during the use of the battery, avoiding the problem of the decline in cycle performance caused by its contamination of the negative electrode.

[0025] If self - polymerized microporous polymer coatings are set on both sides of the composite separator, it will result in high impedance of the separator and low lithium ion transmission efficiency, unable to meet the higher requirements of the market for the fast charging performance of the battery, etc.

[0026] If the ratio of the specific surface area of the second coating to that of the first coating is lower than 10:1 to 200:1, it will lead to an increase in impedance during the charge - discharge process and poor blocking effects on lithium salt anions and transition metal ions, affecting the cycle performance of the battery; if the ratio of the specific surface area of the second coating to that of the first coating is higher than 10:1 to 200:1, it will lead to deformation due to unbalanced internal stress on both sides of the composite separator during the coating process, affecting the electrochemical safety.

[0027] In some embodiments, the specific surface area (BET) of the first coating is 5m 2 / g to 100m 2 / g. For example, it can be 5m 2 / g, 10m 2 / g, 15m 2 / g, 20m 2 / g, 25m 2 / g, 30m 2 / g, 35 m 2 / g, 40 m 2 / g, 45 m 2 / g, 50 m 2 / g, 55 m 2 / g, 60 m 2 / g, 65 m 2 / g, 70 m 2 / g, 75 m 2 / g, 80 m 2 / g, 85 m 2 / g, 90 m 2 / g, 95 m 2 / g, 100 m 2 / g or a range composed of any two of them.

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

[0029] The present invention can further reduce the impedance of the diaphragm 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 diaphragm. 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 of the specific surface area of the first coating and the second coating is:

[0031] The first coating and the second coating debris of the composite membrane sample of the present invention were scraped with a resin scraper, and then about 0.5-1.0g of the debris were weighed and added to the sample tube, and the specific surface area was tested by nitrogen adsorption BET method using JW-BK112 type specific surface and pore size analyzer. The pretreatment condition was 120℃ / 30min, and the adsorption pressure was set as follows: the pressure interval of the first stage was 12kPa, the pressure limit was 15kPa, and the pressure interval of the second stage was 12kPa, and the pressure limit was 30kPa; the BET selection point range was 0.05-0.3, and the thermal delay time was 0.

[0032] The value of the specific surface area of the first coating layer can be adjusted by appropriately changing the structural elements that may be contained in the first coating layer, specifically, by changing the type, particle size, and specific surface area of the inorganic particles; the type and amount of the adhesive; other additives contained in the first coating layer, etc. For example, if the first coating layer uses inorganic particles with a large particle size, the specific surface area of the first coating layer can be reduced; if the amount of the adhesive added is increased, the specific surface area of the first coating layer can be reduced.

[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 of them.

[0035] In some embodiments, 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, TiC.

[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 and modified solid electrolyte particles, lithium germanium aluminum phosphate particles and their doped and modified solid electrolyte particles, lithium lanthanum zirconium oxide particles and their doped and modified solid electrolyte particles, and lithium lanthanum titanium oxide particles and their doped and modified solid electrolyte particles.

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

[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 50% cumulative value D50 of the particle size of the inorganic particles is preferably 0.1 μm to 5 μm, and can be, 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 a range composed of any two of them.

[0039] In some embodiments, the 99% cumulative value D99 of the particle size of the inorganic particles satisfies the relationship: 2.5*D50 ≤ D99 ≤ 4*D50. Satisfying this relationship is beneficial to making the first coating have a good particle size distribution, which is more conducive to forming a more suitable packing structure among the inorganic particles, and forming an effective coating and gap filling effect between the binder and the particles, thereby further improving the heat resistance of the separator.

[0040] The present invention does not particularly limit the type of the adhesive. Exemplarily, the adhesive includes, but is not limited to, any one or a combination of at least two of polyacrylate, polyacrylic acid-polyacrylate copolymer, polyacrylamide copolymer, polyurethane copolymer, polyimide copolymer, polyetherimide copolymer, polyurea copolymer, and styrene-butadiene rubber copolymer. The adhesive can improve the adhesion between the first coating and the base film, so that the first coating can adhere more closely 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% - 98%, for example, it can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98% or the range composed of any two of them.

[0042] The present invention does not particularly limit the mass percentage content of the adhesive, and the addition content corresponding to the purpose can be freely selected.

[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% - 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 the range composed of any two of them.

[0044] In some embodiments, the first coating may further contain additives such as a dispersant, a wetting agent, a thickener, a pH regulator, etc.; in the coating slurry for forming the first coating, for example, a dispersant is added for the purpose of improving dispersibility, coatability or storage stability; in the coating slurry for forming the first coating, for example, a thickener is added for the purpose of improving storage stability; in the coating slurry for forming the first coating, for example, a wetting agent is added for the purpose of improving coating uniformity; in the coating liquid for forming the first coating, for example, a pH regulator is added for the purpose of adjusting the pH.

[0045] The present invention does not particularly limit the type of the dispersant. Exemplarily, the dispersant can be any one or a combination of at least two of sodium polyacrylate copolymer salts, ammonium polyacrylate copolymer salts, and alkanol ammonium salts containing acidic groups.

[0046] The present invention does not particularly limit the type of the thickener. Exemplarily, the thickener can be any one or a combination of at least two of sodium carboxymethyl cellulose, fumed silica, modified urea polymers, organically modified silicate salts, organically modified montmorillonite, and organic bentonite.

[0047] The present invention does not particularly limit the type of the wetting agent. Exemplarily, the wetting agent can be any one or a combination of at least two of polyether siloxane copolymers, organosilicon gemini copolymers, polyacrylate copolymers, polyether-modified silicone copolymers, alkylphenol polyoxyethylene ethers, and polyoxyethylene-based alkylamine copolymers.

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

[0049] The present invention also does not particularly limit the mass percentage contents of the dispersant, thickener, wetting agent, and pH regulator, and the addition contents corresponding to the purpose can be freely selected.

[0050] In some embodiments, based on the total mass of the first coating, the mass percentage contents of each additive such as the dispersant, thickener, wetting agent, and pH regulator can be 0.1% - 3% respectively. For example, they 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 the range composed of any two of them.

[0051] The specific surface area value of the second coating can be adjusted by appropriately changing the types of structural elements that may be contained in the second coating. For example, if the surface roughness of the second coating is increased, the specific surface area of the second coating can be increased; if the proportion of the microscopic void volume in the second coating is increased, the specific surface area of the second coating can be increased. Specifically, the control of the specific surface area of the second coating can be achieved by adjusting the process conditions during the preparation process of the second coating.

[0052] In some embodiments, the self - polymerized microporous polymer includes any one or a combination of at least two of intrinsic microporous polymers (PIMs), conjugated microporous polymers, or hypercrosslinked polymers. The microscopic porous structure of the self - polymerized microporous polymer can be formed due to the rigidity of the polymer molecular chains that cannot be closely stacked, and its macroscopic manifestation is pore - free.

[0053] In some embodiments, the intrinsically microporous polymer may include the polymers listed in the following literature: Baran MJ, Carrington ME, Sahu S, Baskin A, Song J, Baird MA, Han KS, Mueller KT, Teat SJ, Meckler SM, Fu C, Prendergast D, Helms BA. Diversity-oriented synthesis 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. (Baran MJ, Carrington ME, Sahu S, Baskin A, Song J, Baird MA, Han KS, Mueller KT, Teat SJ, Meckler SM, Fu C, Prendergast D, Helms BA. Diversity-oriented synthesis of polymer membranes with ion solvation cages. Nature, Volume 592, Issue 7853, pp. 225-231. doi: 10.1038 / s41586-021-03377-7. Epub 7 April 2021. PMID: 33828319);

[0054] McKeown, N.B., Budd, P.M., Msayib, K., Ghanem, B., Microporous Polymer Material, US7690514B2, 2010.. (McKeown, N.B., Budd, P.M., Msayib, K., Ghanem, B., Microporous Polymer Material, US Patent No. US7690514B2, 2010.)

[0055] In some embodiments, specifically, the intrinsically microporous polymer PIMs comprise repeating units (R AB ) as shown in the following formula (I):

[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] wherein each R 10 is independently selected from (C 1-6 )alkyl or H;

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

[0064] each R 12 is 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, a 3- to 8-membered heterocyclic group, (a 3- to 8-membered heterocyclic group)-C 1-20 alkyl, a 5- to 8-membered heteroaryl, heteroaryl-C 1-20 alkyl.

[0066] In some embodiments, each alkyl, alkenyl, and alkynyl 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 said R1 and R2 are optionally and independently present 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 by one or more Z1.

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

[0069] Each of said Z1 and said Z2 is independently a 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 heterocyclic group, 3- to 8-membered heteroaryl group, (C 3-8 cycloalkyl)-C 1-20 alkyl, (3- to 8-membered heterocyclic group)-C 1-20 alkyl, (5- to 8-membered heteroaryl group)-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 heterocyclic group, (3- to 8-membered heterocyclic group)-C 1-20 alkyl, 5- to 8-membered heteroaryl group, or (5- to 8-membered heteroaryl group)-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 heterocyclic group or 5- to 8-membered heteroaryl group.

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

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

[0074] In some embodiments, each R 13 is independently H, (C 1-20 )alkyl or (C 3-8 )cycloalkyl, wherein the alkyl and cycloalkyl are optionally and independently substituted by 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, a 3- to 8-membered heterocyclic group, a 5- to 8-membered heteroaryl group, (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 is independently H, (C 1-20 )alkyl or (C 3-8 )cycloalkyl.

[0077] In some embodiments, illustratively, the intrinsically microporous polymer may include intrinsically microporous polymer PIM-1 (the A unit is selected from (A) monomer segments, R 11 is H, the B unit is selected from (a) monomer segments, R 12 is CN), intrinsically microporous polymer PIM-2 (the A unit is selected from (A) monomer segments, R 11 is H, the B unit is selected from (g) monomer segments), intrinsically microporous polymer PIM-C1 (the A unit is selected from (j) monomer segments, the B unit is selected from (a) monomer segments, R 12For CN), pyridine-based intrinsically microporous polymer PIM-py (the A unit is selected from the (A) monomer segment, R 11 is H, the B unit is selected from the (b) monomer segment, R 12 is CN), any one or at least two combinations of cyclotriveratrylene-based intrinsically microporous polymer (CTC-network-PIM), hexaazatriphenylene-based intrinsically microporous polymer (HATN-network-PIM).

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

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

[0080] The present invention has no particular limitation on the thickness of the first coating and the second coating, and any coating thickness can be selected. However, based on the comprehensive consideration of the diaphragm impedance, heat resistance and barrier effect, the thickness of the first coating is preferably 0.5 μm to 4 μm, for example, it can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm or the range composed of any two of them; the thickness of the second coating is preferably 0.1 μm to 4 μm, for example, it can be 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 the range composed of any two of them.

[0081] In the present invention, the surface of the base film refers to the two largest and relatively arranged surfaces in the base film.

[0082] The present invention does not make any particular limitation on the base film, and the base film can be a porous film commonly used in the art. Exemplarily, the base film can be a polyolefin porous film.

[0083] The polyolefin porous membrane can be a polyethylene porous membrane, a polypropylene porous membrane, or a polyethylene - polypropylene multi - layer composite porous membrane. The polyethylene - polypropylene multi - layer composite porous membrane refers to a multi - layer composite porous membrane formed by laminating polypropylene (PP) and polyethylene (PE) in any order. For example, a three - layer composite porous membrane of PP - PE - PP, a two - layer composite porous membrane of PP - PE, or a four - layer composite porous membrane of PP - PP - PE - PP.

[0084] The present invention does not particularly limit the thickness of the polyolefin porous membrane. From the viewpoints of mechanical strength and internal resistance, it preferably has a thickness between 1 μm and 5000 μm, more preferably between 5 μm and 20 μm. For example, it can be 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, 20 μm, or a range composed of any two of them.

[0085] The present invention does not particularly limit the average pore diameter and porosity of the polyolefin porous membrane. However, from the viewpoints of mechanical strength, ion permeability, and electrochemical safety, it preferably has a porosity between 30% and 65%. For example, it can be 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or a range composed of any two of them; the average pore diameter is preferably in the range of 20 nm to 100 nm. For example, it can be 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or a range composed of any two of them. In addition, the pore structure of the polyolefin porous membrane is formed by the interlaced connection of several fibrils. The fibrils are formed by the stretching and orientation of the polymer during the preparation process. The preparation method of the polyolefin porous membrane is not particularly limited. For example, it can be a stretching - pore - forming method, a phase - separation method, etc.

[0086] In some embodiments, the present invention provides a method for preparing the composite separator, and the preparation method includes the following steps:

[0087] (1) Adding a raw material including inorganic particles and an adhesive to a first solvent and mixing to obtain a first coating slurry;

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

[0089] (2) Disposing the first coating slurry and the second coating slurry on two opposite surfaces of the base film respectively, and after drying, obtaining the composite separator.

[0090] In some embodiments, the first solvent includes 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 thickening agent may also 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 (such as 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, or a range composed of any two of them); then adding inorganic particles, and continuing to stir and disperse for 10 to 240 minutes (such as 10 minutes, 30 minutes, 60 minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes, 210 minutes, 240 minutes, or a range composed of any two of them); then adding an adhesive, stirring and dispersing for 10 to 180 minutes (such as 10 minutes, 30 minutes, 60 minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes, or a range composed of any two of them); then adding a thickening agent, stirring and dispersing for 10 to 60 minutes (such as 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, or a range composed of any two of them); and finally adding a wetting agent, stirring and dispersing for 10 to 60 minutes (such as 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, or a range composed of any two of them) to obtain the first coating slurry; the rotation speeds of the above stirring and dispersing can be independently 1000 to 5000 r / min (such as 1000 r / min, 1500 r / min, 2000 r / min, 2500 r / min, 3000 r / min, 3500 r / min, 4000 r / min, 4500 r / min, 5000 r / min, or a range composed of any two of them), and the solid content of the first coating slurry can be ≤50%, such as 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, or a range composed of any two of them.

[0094] In some embodiments, the preparation process of the second coating slurry in step (1) may further include: dissolving the self-polymerized microporous polymer in a second solvent, and mechanically stirring at a rotation speed of 50 rpm to 70 rpm (such as 50 rpm, 55 rpm, 60 rpm, 65 rpm, 70 rpm or a range composed of any two of them) for 7 h to 9 h (such as 7 h, 7.5 h, 8 h, 8.5 h, 9 h or a range composed of any two of them) to obtain a homogeneous solution, and controlling the concentration range of the homogeneous solution (slurry solid content) to be 0.2% to 2.5%, such as 0.2%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.3%, 1.5%, 2%, 2.5% or a range composed of any two of them. 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, and further better control the specific surface area of the second coating.

[0095] In some embodiments, step (2) specifically includes: the first coating slurry can be first coated on one surface of the base film, and after drying, the second coating slurry is coated on the other surface of the base film, and after drying, the composite separator is obtained;

[0096] Alternatively, the second coating slurry can be first coated on one surface of the base film, and after drying, the first coating slurry is coated on the other surface of the base film, and after drying, the composite separator is obtained;

[0097] It is also possible to simultaneously coat the first coating slurry and the second coating slurry on two opposite surfaces of the base film respectively, and after simultaneous drying, the composite separator is obtained.

[0098] In some embodiments, the preparation method of the first coating in step (2) includes using a slot die coating process or a 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 using a slot die coating process or a gravure coating process, but the present invention does not limit the specific preparation process parameters. Exemplarily, the relative humidity range RH of the coating area of the second coating is 30% to 60%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60% or a range composed of any two of them. By controlling the relative humidity of the coating area of the second coating, it is beneficial to control the surface roughness and the apparent stacking structure of the coating, and further better control the specific surface area of the second coating.

[0100] The present invention does not limit process parameters such as the drying temperature, drying air volume, and drying time of the first coating and the second coating. These can be selected according to common process parameters in the art, as long as the coating can be dried and cured without damaging the coating structure. From the perspective of better ensuring the specific surface area and structural stability of the coating, exemplarily, the drying temperature is 20°C to 50°C, such as 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, or any range composed of any two of them; the drying time is 10 s to 80 s, such as 10 s, 15 s, 20 s, 25 s, 30 s, 35 s, 40 s, 45 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, or any range composed of any two of them; the drying air volume is 0 to 10 cubic meters per minute, such as 0 cubic meters per minute, 0.5 cubic meters per minute, 1 cubic meter per minute, 2 cubic meters per minute, 2.5 cubic meters per minute, 3.5 cubic meters per minute, 4 cubic meters per minute, 5 cubic meters per minute, 6 cubic meters per minute, 7 cubic meters per minute, 8 cubic meters per minute, 9 cubic meters per minute, 10 cubic meters per minute, or any range composed of any two of them.

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

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

[0103] In some embodiments, in specific applications, the first coating is disposed on the side facing the positive electrode of the battery, and the second coating is disposed on the side facing the negative electrode of the battery. Through this arrangement, the first coating facing the positive electrode has a lower specific surface area while the second coating has a higher specific surface area, forming a morphology with a decreasing pore space from the positive electrode to the negative electrode. As a result, lithium ions maintain a higher concentration at the positive electrode end and the transmission resistance is reduced, while a better blocking effect is achieved at the negative electrode end. Furthermore, while ensuring the blocking effect of other ions, the lithium-ion transmission efficiency can be improved and the impedance can be reduced.

[0104] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0105] Unless otherwise specified, the base film used in the embodiments and comparative examples of the present invention is a polyethylene microporous separator (Star Source Materials, model: SW509C+) with a thickness of 9 μm and a porosity of 42%.

[0106] Example 1

[0107] In this embodiment, a composite separator is provided. The composite separator includes a base film, a first coating disposed on one surface of the base film, and a second coating disposed on the other surface of the base film;

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

[0109] The second coating includes a self-polymerized microporous polymer;

[0110] Among them, the inorganic particles are AlOOH (Shandong Guoci, D50 particle size is 0.6 μm, D99 particle size is 2 μm); the adhesive is a polyacrylic acid-polyacrylate copolymer (Gaorui, 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 thickening agent is sodium carboxymethyl cellulose (weight average molecular weight is 100,000);

[0111] Based on the mass of the first coating being 100%, the mass ratio of the inorganic particles is 94%, the mass ratio of the adhesive is 4.6%, the mass ratio of the dispersant is 0.50%, the mass ratio of the wetting agent is 0.1%, and the mass ratio of the thickening agent is 0.80%;

[0112] The self-polymerized microporous polymer is an intrinsically microporous polymer PIM-1 (Beijing Huawei Ruike).

[0113] The preparation method includes the following steps:

[0114] (1) Disperse the inorganic particles, adhesive, dispersant, wetting agent, and thickening agent in a first solvent, stir evenly to obtain a first coating slurry with a solid content of 35%;

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

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

[0117] Among them, the first solvent is water; the second solvent is a mixed solvent of tetrahydrofuran and dichloromethane with 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 also provided. The preparation of the battery includes the following steps:

[0119] 1) The cathode active material nickel cobalt manganese ternary material (mass ratio of nickel, cobalt, and manganese = 8:1:1), conductive agent conductive carbon black SP, and binder PVDF are added to the solvent NMP in a mass ratio of 90:3:3 and mixed evenly to form a cathode slurry, which is then coated on an aluminum foil current collector with a thickness of 10 μm. Then, it is dried in an oven at 95 °C and roll-pressed on a roll press to obtain a cathode sheet for standby.

[0120] 2) The anode active material artificial graphite, conductive agent acetylene black, and binder SBR are added to water in a mass ratio of 90:5:5 and dispersed evenly to form an anode slurry, which is coated on a copper foil current collector with a thickness of 10 μm. After drying in an oven at 85 °C, it is roll-pressed on a roll press to obtain an anode sheet for standby.

[0121] 3) The above composite separator is placed between the cathode sheet and the anode sheet for lamination and encapsulation, where the first coating of the composite separator faces the cathode sheet and the second coating faces the anode sheet, and then the electrolyte is injected to obtain a battery.

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

[0123] Performance tests are carried out on the above-provided composite separator and battery, and the test methods are as follows:

[0124] (1) Specific surface area of the coating: The test method refers to the specific implementation part above.

[0125] (2) Permeability value: The permeability value of the composite separator 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 in the MD direction (longitudinal direction) and TD direction (transverse direction) of the composite separator are obtained by referring to the method specified in the national standard GB / T 36363-2018 "Polyolefin Separators for Lithium-Ion Batteries", and the average value is taken as the thermal shrinkage rate of the composite separator; among them, the heat treatment temperature of the oven is 150 °C and the heat treatment time is 1 h.

[0127] (4) Sheet resistance: Cut a total of 4 pieces of composite separator samples with a diameter of 45 mm at a flat position. Immerse the samples in the electrolyte (1 mol / L LiPF6 electrolyte, and the solvent is EC, EMC, and DMC with a volume ratio of 1:1:1) and seal them for 30 min. Pour the above electrolyte into the sheet resistance test fixture. Place 1, 2, 3, and 4 separators in the fixture for testing respectively. Use the number of separator layers as the abscissa and the separator resistance as the ordinate for linear fitting to obtain the slope and goodness of fit of the straight line. When the goodness of fit is greater than 0.999, the slope at this time is the sheet resistance of the separator, and the unit is ohm Ω·cm 2 .

[0128] (5) Mn 3+ Permeation concentration (1 h): Use an H-type electrolytic cell to test the transmittance of transition metal ion Mn 3+ . Specifically, test the permeation concentration of Mn 3+ after 1 h. The specific test method includes the following steps:

[0129] In the glove box, use a glass H-type electrolytic cell. The left side is the high-concentration side (simulating the positive electrode side) and is connected to the counter electrode (Pt wire). The right side is the low-concentration side (simulating the negative electrode side) and is connected to the working electrode (glassy carbon) and the reference electrode (lithium wire). The middle is separated by a 1-layer circular separator sample with a diameter of 10 cm, and the orientation of the separator is the same as that in the battery. Add an equal amount of electrolyte (1 mol / L LiPF6 electrolyte, and the solvent is EC, EMC, and DMC with a volume ratio of 1:1:1) to both sides. Before the test, add manganese(III) acetylacetonate salt to the left side and stir to dissolve it so that the Mn 3+ concentration on the left side is 50 mmol / L, and then add LiPF6 to the right side and stir to dissolve it so that the Li + concentration is 150 mmol / L. Connect the above three electrodes to the electrochemical workstation and perform a CV test at a rate of 0.2 V / s in the range of 4.0 V to 1.5 V. Starting from the test, take 5 mL of liquid sample from the right side 1 hour later, add acid for digestion, and then use ICP to test the Mn 3+ concentration.

[0130] (6) Cycling performance: Take the cycle capacity retention rate of the battery at the 100th cycle at 25 °C as the result of the cycling performance. The specific test method includes the following steps: Charge at a constant current and constant voltage of 0.8C, discharge at a constant current of 1C, measure the initial discharge capacity, cycle 100 times under this condition, test the discharge capacity after 100 cycles, and calculate the ratio of the discharge capacity after 100 cycles to the initial discharge capacity as the cycle capacity retention rate at 25 °C for 100 cycles.

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

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

[0133] Examples 2-16, Comparative Examples 1-4 are different from Example 1 in that at least one of the type and / or particle size of the inorganic particles, the type of the self-polymerized microporous polymer, the coating process parameters (such as the solid content and humidity of the coating slurry), and the coating thickness is different, as specifically shown in Table 1; the preparation method of the battery, the composite separator and the test method of the battery are the same as those 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; PIM-py in Example 14 was purchased from Sigma-Aldrich; the γ-phase nano-alumina in Comparative Example 3 was a porous particle, 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 400,000, and the second solvent used was N-methylpyrrolidone (NMP).

[0137] Table 2

[0138]

[0139] As can be seen from Table 2, the composite separator provided by the present invention can not only prevent the migration of transition metal ions (Mn 3+ penetration concentration: below 0.45 mmol / L, preferably below 0.3 mmol / L), but also has a high lithium ion transmission efficiency and a low impedance (surface resistance: 2.5 Ω·cm 2 or below, preferably 2 Ω·cm 2 or below), and has good heat resistance (thermal shrinkage rate: 4% or below, preferably 3.5% or below). When it is used in a battery, the battery has good cycle performance (above 92%, preferably above 95%).

[0140] Compared with Example 1, the BET ratio of the second coating to the first coating of the composite separator provided by Comparative Example 1 is higher than 200:1, the surface resistance of the composite separator increases significantly, and the cycle performance of the battery drops significantly; for the composite separator provided by Comparative Example 2, both sides of the coating are inorganic coatings, and the ability of the composite separator to prevent the migration of transition metal ions decreases; for the composite separator provided by Comparative Example 3, both sides of the coating are polymer coatings, and the thermal shrinkage rate and surface resistance of the composite separator increase significantly, and the cycle performance of the battery drops significantly; Comparative Example 4 is an existing PVDF coating, and the specific surface area of the second coating of the prepared composite separator cannot reach 250-5000 m 2 / g, the BET ratio of the second coating to the first coating also does not satisfy 10-200, and the thermal shrinkage rate and the ability to prevent the migration of transition metal ions of the composite separator decrease significantly.

[0141] The applicant declares that the composite separator of the present invention and its preparation method and application are illustrated by the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent substitution of each raw material of the product of the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A composite separator, characterized in that, The composite separator includes a base film, a first coating provided on one surface of the base film, and a second coating provided on the other surface of the base film; The first coating includes inorganic particles and an adhesive; The second coating includes a self-polymerized microporous polymer; The ratio of the specific surface area of the second coating to that of the first coating is 10:1 to 200:

1.

2. The composite separator according to claim 1, wherein The specific surface area of the first coating is 5 m 2 / g to 100 m 2 / g, and the specific surface area of the second coating is 250 m 2 / g to 5000 m 2 / g.

3. The composite separator according to claim 1, wherein The self-polymerized microporous polymer includes any one or at least two combinations of an intrinsically microporous polymer, a conjugated microporous polymer, or a hypercrosslinked polymer.

4. The composite separator according to claim 3, wherein The intrinsically microporous polymer contains 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): ； wherein each R 10 is independently selected from (C 1-6 )alkyl or H; Each R 11 is independently selected from -CH2NR1R2 or H; Each R 12 is 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), a 3- to 8-membered heterocyclic group, (3- to 8-membered heterocyclic group)-C 1-20 alkyl, a 5- to 8-membered heteroaryl, heteroaryl-C 1-20 alkyl; or each alkyl, alkenyl, and alkynyl 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 said R1 and R2 are optionally and independently present in oxidized form; or R1 and R2 may optionally and independently be substituted by one or more Z1; or, R1 and R2 may together with the nitrogen atom to which they are attached form a 3- to 8-membered heterocyclic group or a 5- to 8-membered heteroaryl, each of which is optionally substituted by one or more Z2; Each of said Z1 and said Z2 is independently a 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), a 3- to 8-membered heterocyclic group, a 3- to 8-membered heteroaryl, (C 3-8 cycloalkyl)-C 1-20 alkyl, (3- to 8-membered heterocyclic group)-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, a 3- to 8-membered heterocyclic group, (a 3- to 8-membered heterocyclic group)-C 1-20 alkyl, a 5- to 8-membered heteroaryl, or (a 5- to 8-membered heteroaryl)-C 1-20 alkyl; Each R 13 is independently H, (C 1-20 )alkyl or (C 3-8 )cycloalkyl, where the alkyl and cycloalkyl are optionally and independently substituted by one or more Z3; Each Z3 is independently a 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), a 3- to 8-membered heterocyclic group, a 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 is independently H, (C 1-20 )alkyl or (C 3-8 )cycloalkyl.

5. The composite separator according to claim 3, wherein The intrinsically microporous polymer includes any one or at least two combinations of an intrinsically microporous polymer PIM-1, an intrinsically microporous polymer PIM-2, an intrinsically microporous polymer PIM-C1, a pyridine-based intrinsically microporous polymer PIM-py, a cyclotriveratrylene-based intrinsically microporous polymer, or a hexachloronaphthyridine-based intrinsically microporous polymer; The conjugated microporous polymer includes any one or at least two combinations of a tetra[4-(9H-carbazol-9-yl)phenyl]methane-based conjugated microporous polymer, a 1,3,5-tris(2-thienyl)phenyl-based conjugated microporous polymer, a 1,1,2,2-tetrakis(4-(9H-carbazol-9-yl)-[1,1'-biphenyl]-4-yl)ethylene-based conjugated microporous polymer, or a poly(1,3,5-triethynylbenzene)-based conjugated microporous polymer; The hypercrosslinked polymer includes a polylactic acid-poly(4-vinylbenzyl chloride-co-divinylbenzene) hypercrosslinked polymer and / or hypercrosslinked polyaniline.

6. The composite separator according to claim 1, wherein, The inorganic particles include ceramic particles and / or inorganic solid electrolyte particles.

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

8. The composite separator according to claim 1, wherein The thickness of the first coating is 0.5 μm to 4 μm, and the thickness of the second coating is 0.1 μm to 4 μm.

9. A method for preparing a composite separator as described in claim 1, characterized in that, The preparation method includes the following steps: (1) Add raw materials including inorganic particles and adhesives to a first solvent and mix to obtain a first coating slurry; Mix the self-polymerized microporous polymer with a second solvent to obtain a second coating slurry; (2) Dispose the first coating slurry and the second coating slurry on two opposite surfaces of the base film respectively, and after drying, obtain the composite separator.

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

11. A battery, characterized in that, The battery includes the composite separator according to any one of claims 1-8 or includes the composite separator obtained by the preparation method according to claim 9 or 10.

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