Composite diaphragm and preparation method, battery and application thereof

Abstract

The present invention belongs to the technical field of battery separator materials, specifically relating to a composite separator, a preparation method, a battery, and its applications. The composite separator comprises a base membrane and a first coating layer applied to one surface of the base membrane; the composite separator has a porosity of 45% to 87%; the first coating layer is made from a first active material, which in turn comprises a composite electrolyte material; the composite electrolyte material comprises a solid electrolyte, an organic ligand, and a lithium supplement. The composite separator exhibits excellent liquid absorption and thermal stability, meeting the requirements of rapid battery charging and discharging.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery diaphragm materials, and in particular relates to a composite diaphragm and a preparation method thereof, a battery and applications thereof. Background Art

[0002] Lithium-ion batteries (LIBs) have become the primary mobile power source due to their high energy density, long lifespan, and low self-discharge rate. LIB safety has long been a concern and a major obstacle to the development of high-energy-density LIBs. The performance of the separator, a crucial component of LIBs, significantly impacts battery capacity and performance and plays a crucial role in LIB safety. However, conventional separators cannot meet the demands of high-performance and safer battery systems due to issues such as poor electrolyte compatibility, thermal runaway, and ultimately dendrite growth. Therefore, developing a method to coat different functional layers on both sides of the separator to improve these issues is urgent. However, conventional separator coatings have high bulk density and limited porosity increase, resulting in defects such as decreased cycle capacity retention with increasing cycle number and rate, and an inability to operate for extended periods under rapid charge and discharge conditions. Summary of the Invention

[0003] To solve the above problems, the present invention provides a composite diaphragm and its preparation method, a battery and its application. The composite diaphragm has good liquid absorption rate and thermal stability, and can meet the requirements of fast charging and discharging of the battery.

[0004] The present invention is achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a composite diaphragm, comprising a base film and a first coating layer coated on a surface of the base film;

[0006] The base film is at least one of a PE film, a PP film, a polyethylene-polypropylene composite film, and a PI film;

[0007] The porosity of the composite membrane is 45% to 87%;

[0008] The raw material of the first coating layer includes a first active material, and the first active material includes a composite electrolyte material;

[0009] The raw materials of the composite electrolyte material include solid electrolyte, organic ligand and lithium supplement agent;

[0010] The chemical formula of the solid electrolyte is as follows:

[0011] Li x Al y A m B n PO e ;

[0012] wherein 0<x≤3, 0<y≤2, 0≤m<2, 0≤n<2, 4≤e≤6.5, m and n are not simultaneously 0, A is at least one element of Group IVA, and B is at least one element of Group IVB;

[0013] The organic ligand includes at least one of trimesic acid, 2-methylimidazole, terephthalic acid, 2,5-dihydroxyterephthalic acid, and 3,3',5,5'-biphenyltetracarboxylic acid;

[0014] The lithium supplement comprises at least one of lithium nitrate, lithium chloride, lithium acetate, lithium hydroxide and lithium oxide.

[0015] In some possible implementations, the composite membrane has a thickness of 7 μm to 31 μm.

[0016] In some possible implementations, the composite membrane further includes a second coating layer;

[0017] The raw material of the second coating layer includes a second active material; the second active material includes at least one of the above-mentioned composite electrolyte material, polyvinylidene fluoride, polymethyl methacrylate, polyvinylidene fluoride-hexafluoropropylene copolymer, polyaniline, polyethylene oxide, and aramid;

[0018] The second coating layer is applied to the other surface of the base film that is away from the first coating layer.

[0019] In some possible implementations, the thickness of the first coating layer is 2 μm to 7 μm.

[0020] In some possible implementations, the thickness of the second coating layer is 2 μm to 7 μm.

[0021] In a second aspect, the present invention provides a method for preparing a composite membrane, comprising the following steps:

[0022] Applying the first mixed slurry on the surface of the base film to form a first coating after drying to obtain a composite diaphragm;

[0023] The first mixed slurry contains a first active material and a first auxiliary agent;

[0024] The first active material includes the composite electrolyte material described above;

[0025] The first auxiliary agent includes at least one of a wetting agent, a plasticizer, a dispersant, a binder, an anti-settling agent, a defoaming agent, and a pore-forming agent.

[0026] In some possible implementations, the mass ratio of the first active material to the first auxiliary agent is 1:(0.01-0.15).

[0027] In some possible implementations, the preparation of the composite electrolyte material includes the following steps:

[0028] The mixture is subjected to a solvent thermal reaction, and then washed, dried and calcined to obtain the composite electrolyte material;

[0029] The mixture contains organic ligands, metal salts and solid electrolytes.

[0030] In some possible implementations, the method for preparing the composite diaphragm further includes the following steps:

[0031] applying a second mixed slurry on the other surface of the base film away from the first coating layer, and forming a first coating layer after drying to obtain a composite diaphragm;

[0032] The second mixed slurry contains the second active material and the second auxiliary agent;

[0033] The second auxiliary agent includes at least one of a wetting agent, a plasticizer, a dispersant, a binder, an anti-settling agent, a defoaming agent, and a pore-forming agent.

[0034] In a third aspect, the present invention provides an application of the composite diaphragm provided above in the field of battery material technology.

[0035] Compared with the prior art, the composite diaphragm, preparation method, and battery provided by the present invention have at least the following beneficial technical effects:

[0036] The composite diaphragm provided by the present invention has a porosity of 45% to 87%. The higher porosity provides more ion storage space. The large porosity brings a high specific surface area and shortens the diffusion path of ions, thereby improving the ionic conductivity of the diaphragm and further improving the rapid charging and discharging performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present drawings or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present drawings. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0038] Figure 1 A schematic structural diagram of a composite diaphragm provided in an embodiment of the present invention;

[0039] Figure 2 TEM image of the composite electrolyte material provided in Example 1 of the present invention;

[0040] Figure 3TEM image of the composite electrolyte material provided in Example 7 of the present invention;

[0041] Figure 4 TEM image of the composite electrolyte material provided in Example 13 of the present invention;

[0042] Figure 5 This is a TEM image of the composite electrolyte material provided in Comparative Example 1 of the present invention;

[0043] Figure 6 TEM image of the composite electrolyte material provided in Comparative Example 10 of the present invention;

[0044] Figure 7 TEM image of the composite electrolyte material provided in Comparative Example 19 of the present invention;

[0045] Figure 8 Electrochemical impedance spectroscopy of button batteries made of the separators provided in Example 2, Comparative Example 8, and Comparative Example 9 of the present invention;

[0046] Figure 9 Electrochemical impedance spectroscopy of button batteries made of the separators provided in Example 8, Comparative Example 17, and Comparative Example 18 of the present invention;

[0047] Figure 10 Electrochemical impedance spectroscopy of button batteries made with the diaphragms provided in Example 14, Comparative Example 26, and Comparative Example 27 of the present invention.

[0048] Description of the drawings: 1-first coating, 2-base film, 3-second coating.

[0049] The purpose, features and advantages of this drawing will be further described with reference to the accompanying drawings in conjunction with the embodiments. DETAILED DESCRIPTION

[0050] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is described and illustrated below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention. Based on the embodiments provided by the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work are within the scope of protection of the present invention.

[0051] Obviously, the following descriptions are merely examples or embodiments of the present invention, and those skilled in the art will be able to apply the present invention to other similar scenarios without inventive effort. Furthermore, it is understood that while the effort involved in such a development process may be complex and lengthy, for those skilled in the art related to the present disclosure, any design, manufacturing, or production changes based on the technical content disclosed in the present disclosure are merely conventional technical means and should not be construed as an inadequacy of the present disclosure.

[0052] However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters or repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to facilitate a thorough understanding of the present invention by those skilled in the art and is not intended to limit the subject matter recited in the claims.

[0053] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form a new technical solution, and all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0054] The following is a detailed description of a composite diaphragm, a preparation method, and a battery according to an embodiment of the present invention.

[0055] A first aspect of an embodiment of the present invention provides a composite diaphragm, comprising a base film and a first coating layer coated on a surface of the base film;

[0056] The porosity of the composite diaphragm is 45%~87%;

[0057] The raw material of the first coating layer includes a first active material, and the first active material includes a composite electrolyte material;

[0058] The raw materials of composite electrolyte materials include solid electrolytes, organic ligands and lithium supplements.

[0059] The composite membrane provided by the present invention comprises a base membrane and a first coating layer. The composite electrolyte material exhibits a high ion migration rate and a porosity of 45% to 87%. This high porosity provides more ion storage space. The high porosity results in a high specific surface area and shortens the ion diffusion path, increasing the membrane's ionic conductivity and, in turn, improving the battery's rapid charge and discharge performance.

[0060] In some embodiments, the base film is at least one of a PE (Polyethylene Film, polyethylene) film, a PP (polypropylene) film, a polyethylene-polypropylene composite film, and a PI (polyimide) film.

[0061] In some embodiments, the base film has a thickness of 5 μm to 25 μm.

[0062] In some embodiments, the solid electrolyte has the following chemical formula:

[0063] Li x Al y A m B n P3O 12 ;

[0064] Wherein, 0<x≤3, 0<y≤2, 0≤m<2, 0≤n<2, m and n are not 0 at the same time, A is at least one element of Group IVA, and B is at least one element of Group IVB.

[0065] In some embodiments, the solid electrolyte has the following chemical formula:

[0066] Li x Al y A m B n P3O 12 ;

[0067] Among them, 0<x≤3, 0<y≤2, 0≤m<2, 0≤n<2, m and n are not 0 at the same time, A is at least one of Ge and Sn, and B is at least one of Ti and Zr.

[0068] In some specific embodiments, the chemical formula of the solid electrolyte is:

[0069] Li 1.5 Al 0.5 Ge 1.5 P3O 12 .

[0070] In some specific embodiments, the chemical formula of the solid electrolyte is:

[0071] Li 1.3 Al 0.3 Ti 1.7 P3O 12 .

[0072] In some specific embodiments, the chemical formula of the solid electrolyte is:

[0073] Li2AlTi 0.5 Ge 0.5 P3O 12 .

[0074] In some embodiments, the first coating layer has a thickness of 2 μm to 7 μm.

[0075] In some embodiments, the composite separator has a thickness of 7 μm to 31 μm.

[0076] In some embodiments, the composite membrane further comprises a second coating;

[0077] The second coating is applied to the other surface of the base film away from the first coating. Figure 1 As shown, 1 is the first coating, 2 is the base film, and 3 is the second coating.

[0078] In some embodiments, the raw material of the second coating layer includes a second active material; the second active material includes at least one of the above-mentioned composite electrolyte material, polyvinylidene fluoride, polymethyl methacrylate, polyvinylidene fluoride-hexafluoropropylene copolymer, polyaniline, polyethylene oxide, and aramid.

[0079] In some embodiments, the second coating layer has a thickness of 2 μm to 7 μm.

[0080] A second aspect of an embodiment of the present invention provides a method for preparing the composite diaphragm, comprising the following steps:

[0081] S10. The first mixed slurry is applied to the surface of the base film, and after drying, a first coating is formed to obtain a composite membrane;

[0082] The first mixed slurry contains a first active material and a first auxiliary agent;

[0083] The first active material includes the composite electrolyte material described above.

[0084] In some embodiments, in the above step S10 , the mass ratio of the first active material to the first auxiliary agent is 1:(0.01-0.15).

[0085] In some embodiments, in the above step S10 , the viscosity of the first mixed slurry is 500 mPa·s to 910 mPa·s.

[0086] In some embodiments, the preparation of the composite electrolyte material comprises the following steps:

[0087] S101. The mixture is subjected to a solvothermal reaction, and then washed, dried and calcined to obtain a composite electrolyte material;

[0088] The mixture contains an organic ligand, a lithium supplement and a solid electrolyte.

[0089] In the preparation of the composite electrolyte material, a mixture of an organic ligand, a lithium replenisher and a solid electrolyte is subjected to a solvent thermal reaction to release the aluminum element in the solid electrolyte, or to release aluminum and a group IVB element simultaneously, and to form a MOF structure with the organic ligand. The lithium in the lithium replenisher is used to supplement the defects caused by the release of the group IVB element in the solid electrolyte, thereby obtaining a composite electrolyte material in situ doped with a MOF material. The obtained composite electrolyte material has a high resistance to lithium ions (Li + )'s conductivity, structural stability and mechanical strength.

[0090] In some embodiments, in the above step S101 , the mass ratio of the organic ligand, the lithium supplement agent, and the solid electrolyte is (2-9):1:(1-7).

[0091] In some embodiments, in the above step S101, the organic ligand includes at least one of trimesic acid (H3BTC), 2-methylimidazole (2-Methylimidazole), terephthalic acid (H2BDC), 2,5-dihydroxyterephthalic acid (H4DOBDC), and 3,3',5,5'-biphenyltetracarboxylic acid (H4ABTC).

[0092] In some embodiments, in the above step S101, the lithium supplement includes at least one of lithium nitrate, lithium chloride, lithium acetate, lithium hydroxide, and lithium oxide.

[0093] In some embodiments, in step S101, the mixture further includes a solvent, including at least one of methanol, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), ethanol, and chloroform. In this case, using an organic material as the solvent allows for in-situ doping and preparation of the MOF material while maintaining the solid electrolyte structure.

[0094] In some embodiments, in the above step S101, preparing the mixture includes the following steps:

[0095] S1011. After mixing the organic ligand with the solvent, the mixture is mixed with the lithium supplement agent and the solid electrolyte to obtain a mixture.

[0096] In some embodiments, in the above step S1011 , the mass volume ratio of the organic ligand to the solvent is (3.1 g to 5 g): 1 ml.

[0097] In some embodiments, in step S1011, the stirring speed of the mixture with the lithium supplement and the solid electrolyte is 490 rpm to 510 rpm and the stirring time is 4 hours to 6 hours. In this case, the obtained mixture has uniform composition and no agglomeration.

[0098] In some embodiments, in the above step S101, in the solvent thermal reaction, the reaction temperature is 120° C. to 150° C., and the reaction time is 24 h to 36 h.

[0099] In some embodiments, in the above step S101, the washing step includes:

[0100] S1012. Centrifuge the solvent thermal reaction product to obtain a precipitate, and wash it with a detergent.

[0101] In some embodiments, the detergent washing step in step S1012 includes an alcohol wash followed by a water wash. In this case, alcohol is first used to remove unreacted metal salts or ligands, and then deionized water is used to form defects, thereby increasing the charge transfer capacity. It should be noted that the amount of alcohol or water used for washing depends on the amount of precipitate obtained during actual preparation and is not particularly limited in the present embodiments. However, as an example, the amount of alcohol or water used in a single wash can be 2 to 5 times the amount of precipitate.

[0102] In some embodiments, the alcohol washing step includes: mixing the alcohol and the precipitate and then centrifuging and separating the mixture to obtain the precipitate for the next washing step.

[0103] In some embodiments, the number of alcohol washes is at least 3 times.

[0104] In some embodiments, the water washing step includes: mixing water and the precipitate after alcohol washing and then centrifuging to obtain the precipitate for the next washing step.

[0105] In some embodiments, the number of water washes is at least 3 times.

[0106] It should be noted that the rotation speed of centrifugal separation is conventional in the art and is not particularly limited in the embodiments of the present invention.

[0107] In some specific embodiments, the alcohol includes at least one of methanol, ethanol, and propanol.

[0108] In some embodiments, in the above step S101 , the drying temperature is 85° C. to 90° C.

[0109] In some embodiments, in the above step S101, the drying time is 8 hours to 9 hours. It should be noted that the drying time is only an example of the embodiment of the present invention, and an appropriate drying time can be selected according to the amount of the product during actual preparation.

[0110] In some specific embodiments, in the above step S101, the drying conditions are: vacuum drying, temperature of 85° C. to 90° C., and time of 8 h to 9 h.

[0111] In some embodiments, in the calcination step in step S101, the calcination atmosphere is an inert gas, and the calcination temperature is 490°C to 510°C.

[0112] In some embodiments, in the calcination step in step S101, the calcination time is 3 hours to 4 hours.

[0113] In some embodiments, the inert gas includes at least one of argon, helium, and neon.

[0114] In some embodiments, in the above step S10, the first auxiliary agent includes at least one of a wetting agent, a plasticizer, a dispersant, a binder, an anti-settling agent, a defoaming agent, and a pore-forming agent.

[0115] In some specific embodiments, the wetting agent includes at least one of Dow Corning DC501W, Dow Corning DC502W, and Dow Corning DC67.

[0116] In some specific embodiments, the plasticizer includes at least one of triethyl phosphate (TEP), triphenyl phosphate (TPP), ethylene carbonate (EC), propylene carbonate (PC), triethyl citrate (TEC), tributyl citrate (TBC), acetyl tributyl citrate (ATBC), and dioctyl adipate (DOA).

[0117] In some specific embodiments, the dispersant includes at least one of T50, A-30SL, and A-6114.

[0118] In some specific embodiments, the binder includes at least one of GR-508, GR-506, and GR-816B produced by Hunan Gaorui Power Materials Co., Ltd.

[0119] In some specific embodiments, the anti-settling agent includes at least one of polyvinyl pyrrolidone (PVP) and hydroxyethyl cellulose (HEC).

[0120] In some embodiments, the defoaming agent includes polydimethylsiloxane (PDMS).

[0121] In some specific embodiments, the pore-forming agent includes at least one of polyethylene glycol (PEG), polyvinyl pyrrolidone (PVP), and polymethyl methacrylate (PMMA).

[0122] In some embodiments, in the above step S10, the preparation of the first mixed slurry includes the following steps:

[0123] S102. Mix the first active material solution and the first auxiliary agent to obtain a first mixed solution, adjust the viscosity of the first mixed solution, and filter to obtain a first mixed slurry.

[0124] In some embodiments, in the above step S102, the preparation of the first active material solution includes the following steps:

[0125] S1021. Under stirring conditions, mix the first active material and carboxymethyl cellulose (CMC) solution to obtain a first active material solution.

[0126] In some specific embodiments, in the above step S1021, the stirring speed is 500 r / min to 600 r / min.

[0127] In some specific embodiments, in the above step S1021 , the mass ratio of the first active material to the carboxymethyl cellulose solution is 1:(2-3).

[0128] In some specific embodiments, in the above step S1021, the concentration of the carboxymethyl cellulose solution is 5% to 8%.

[0129] In some embodiments, in the above step S102, the step of mixing the first active material solution and the first auxiliary agent to obtain the first mixed solution includes:

[0130] S1022. Add the first auxiliary agent to the first active material solution under stirring conditions at a rotation speed of 500 r / min to 600 r / min, and continue stirring for 6 h to 10 h to obtain a first mixed solution.

[0131] In some embodiments, in the above step S102, the step of adjusting the viscosity of the first mixed liquid includes:

[0132] S1023. Add water to the first mixed liquid under stirring conditions at a rotation speed of 500 r / min to 600 r / min, and continue stirring for more than 1 hour.

[0133] In some embodiments, in the above step S102, the filtering step includes: filtering with a filter cloth.

[0134] In some specific embodiments, the mesh size of the filter cloth is 100-300 mesh.

[0135] In some embodiments, in the above step S10, a doctor blade coater is used to coat the first mixed slurry on the surface of the base film.

[0136] In some embodiments, in the above step S10, the drying temperature is 55° C. to 65° C., and the drying time is 10 min to 20 min.

[0137] In some embodiments, the method for preparing the composite membrane further comprises the following steps:

[0138] S20. The second mixed slurry is applied to the other surface of the base film away from the first coating, and after drying, a first coating is formed to obtain a composite membrane;

[0139] The second mixed slurry contains a second active material and a second auxiliary agent.

[0140] In some embodiments, in the above step S20, the mass ratio of the second active material to the second auxiliary agent is 1:(0.09-0.15).

[0141] In some embodiments, in the above step S20, the viscosity of the second mixed slurry is 2300 mPa·s to 3600 mPa·s.

[0142] In some embodiments, in the above step S20, the second active material includes at least one of the above composite electrolyte material, polyvinylidene fluoride, polymethyl methacrylate, polyvinylidene fluoride-hexafluoropropylene copolymer, polyaniline, polyethylene oxide, and aramid.

[0143] In some specific embodiments, the average molecular weight of polyvinylidene fluoride is 390,000 to 410,000, preferably 400,000.

[0144] In some specific embodiments, the average molecular weight of polymethyl methacrylate is 90,000 to 110,000, preferably 100,000.

[0145] In some specific embodiments, the average molecular weight of the polyvinylidene fluoride-hexafluoropropylene copolymer is 450,000 to 500,000, preferably 455,000.

[0146] In some specific embodiments, the polyaniline is a product of AR grade purity produced by Shanghai MacLean Biochemical Technology Co., Ltd.

[0147] In some specific embodiments, the average molecular weight of polyethylene oxide is 590,000 to 610,000, preferably 600,000.

[0148] In some specific embodiments, the purity of the aramid produced by Shanghai MacLean Biochemical Technology Co., Ltd. is AR grade product.

[0149] In some embodiments, in the above step S20, the second auxiliary agent includes at least one of a wetting agent, a plasticizer, a dispersant, a binder, an anti-settling agent, a defoaming agent, and a pore-forming agent.

[0150] In some embodiments, in the above step S20, the preparation of the second mixed slurry includes the following steps:

[0151] S201. Mix the second active material solution and the second auxiliary agent to obtain a second mixed solution, adjust the viscosity of the second mixed solution, and filter to obtain a second mixed slurry.

[0152] In some embodiments, in step S201 above, the preparation of the second active material solution includes the following steps:

[0153] S2011. Under stirring conditions, the second active material and carboxymethyl cellulose (CMC) solution are mixed to obtain a second active material solution.

[0154] In some specific embodiments, in the above step S2011, the stirring speed is 500 r / min to 600 r / min.

[0155] In some specific embodiments, in the above step S2011, the mass ratio of the second active material to the carboxymethyl cellulose solution is 1:(2-3).

[0156] In some specific embodiments, in the above step S2011, the concentration of the carboxymethyl cellulose solution is 5% to 8%.

[0157] In some embodiments, in the above step S201, the step of mixing the second active material solution and the second auxiliary agent to obtain a second mixed solution includes:

[0158] S2012. Add the second auxiliary agent to the second active material solution under stirring conditions at a rotation speed of 500 r / min to 600 r / min, and continue stirring for 6 h to 10 h to obtain a second mixed solution.

[0159] In some embodiments, in the above step S201, the step of adjusting the viscosity of the second mixed liquid includes:

[0160] S2013. Add water to the second mixed liquid under stirring conditions at a rotation speed of 500 r / min~600 r / min, and continue stirring for more than 1 hour.

[0161] In some embodiments, in the above step S201, the filtering step includes: filtering with a filter cloth.

[0162] In some specific embodiments, the mesh size of the filter cloth is 300-400 mesh.

[0163] In some embodiments, in the above step S20, a blade coater is used to coat the second mixed slurry on the surface of the base film.

[0164] In some embodiments, in the above step S20, the drying temperature is 55° C. to 65° C., and the drying time is 10 min to 20 min.

[0165] In some embodiments, a method for preparing a composite membrane is provided, comprising the following steps:

[0166] S11. Applying a first mixed slurry on the surface of the base film and forming a first coating layer after drying; wherein the first mixed slurry contains a first active material and a first auxiliary agent.

[0167] S21. Apply a second mixed slurry on the other surface of the base film away from the first coating layer, and obtain a composite diaphragm after drying; wherein the second mixed slurry contains a second active material and a second auxiliary agent.

[0168] In other embodiments, a method for preparing a composite membrane is provided, comprising the following steps:

[0169] S12. Coating a first mixed slurry on the surface of the base film; wherein the first mixed slurry contains a first active material and a first auxiliary agent.

[0170] S22. Apply a second mixed slurry on the other surface of the base film away from the first coating layer, and obtain a composite diaphragm after drying; wherein the second mixed slurry contains a second active material and a second auxiliary agent.

[0171] The composite diaphragm and preparation method provided by the present invention are further described below with reference to specific embodiments.

[0172] Example 1

[0173] Example 1 provides a composite diaphragm, comprising a base film and a first coating layer coated on one surface of the base film;

[0174] The porosity of the composite membrane is 45%.

[0175] Among them, the base film is PE film with a thickness of 7 μm;

[0176] The active material in the first coating is a composite electrolyte material with a thickness of 6.5 μm; wherein the raw material of the composite electrolyte material is Li 1.5 Al 0.5 Ge 1.5 P3O 12 (solid electrolyte, LAGP), H3BTC (organic ligand) and lithium nitrate (lithium supplement).

[0177] This embodiment also provides a method for preparing a composite diaphragm, the steps of which are as follows:

[0178] S1-1. Preparation of composite electrolyte materials

[0179] (1) Preparation of a mixture: 50 g of H3BTC was added to 100 ml of methanol and stirred until completely dissolved. The mixture was then mixed with 10 g of lithium nitrate and 29 g of LAGP powder and stirred for 4 h at a stirring speed of 500 rpm to obtain a mixture.

[0180] (2) Solvothermal reaction: The mixture was placed in a high-pressure reactor and reacted at 120 °C for 24 h to obtain the precursor.

[0181] (3) Washing: The precursor was centrifuged to obtain a precipitate, which was washed 4 times with methanol and 4 times with deionized water.

[0182] (4) Drying: The washed product was vacuum dried in a forced air drying oven for 8 h at a drying temperature of 85 °C.

[0183] (5) Calcination: The dried product was calcined under argon atmosphere at a temperature of 500 °C for 4 h, and then cooled to room temperature to obtain a composite electrolyte material.

[0184] S1-2. Preparation of the first mixed slurry

[0185] (1) Preparation of the first active material solution

[0186] Under a stirring speed of 500 r / min, 23.2 g of the composite electrolyte material prepared in step S1-1 was divided into three portions, and each portion was added to 62.2 g of 5% CMC solution at intervals of 1 hour to obtain a first active material solution.

[0187] (2) Preparation of the first mixed solution

[0188] GR-506 (binder), T50 (dispersant), and DC501W (wetting agent) were added to the first active material solution at a stirring speed of 500 r / min and stirred for 0.5 h to obtain a first mixed solution. The mass ratio of the composite electrolyte material, GR-506, T50, and DC501W was 1:0.05:0.03:0.01.

[0189] (3) Under stirring conditions at a speed of 500 r / min, 30 g of deionized water was added to the first mixed liquid. After stirring for 1 h, the mixture was filtered using a 300-mesh filter cloth to obtain a first mixed slurry with a viscosity of 527 mPa·s.

[0190] S1-3. Apply the first coating

[0191] The first mixed slurry was evenly coated on one surface of the PE base film using a doctor blade coater and dried at 85° C. for 15 minutes to obtain the composite diaphragm provided in this embodiment.

[0192] Example 2

[0193] Example 2 provides a composite membrane consisting of a base membrane, a first coating layer, and a second coating layer;

[0194] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0195] The material and thickness of the base film and the material and thickness of the first coating layer are the same as those in Example 1;

[0196] The material and thickness of the second coating layer are the same as those of the first coating layer.

[0197] This embodiment also provides a method for preparing a composite diaphragm. The steps are basically the same as those in Example 1, except that the following steps are also included:

[0198] S2-4. Apply the second coating

[0199] The first mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this embodiment.

[0200] Example 3

[0201] Example 3 provides a composite diaphragm having the same structural composition as that of Example 2.

[0202] This embodiment also provides a method for preparing a composite diaphragm, and the steps are basically the same as those in Example 2, except that:

[0203] Step S1-1. Preparation of composite electrolyte material,

[0204] (1) Preparation of a mixture: 50 g of H3BTC, 10 g of lithium nitrate, 29 g of LAGP powder, and 100 ml of methanol were mixed and stirred for 1 h at a stirring speed of 500 rpm to obtain a mixture.

[0205] Example 4

[0206] Example 4 provides a composite diaphragm having the same structural composition as that of Example 2.

[0207] This embodiment also provides a method for preparing a composite diaphragm, and the steps are basically the same as those in Example 2, except that:

[0208] Step S1-1. Preparation of composite electrolyte material

[0209] (3) Washing: The precursor was centrifuged to obtain a precipitate, which was then washed four times with methanol.

[0210] Example 5

[0211] Example 5 provides a composite diaphragm having the same structural composition as that of Example 2.

[0212] This embodiment also provides a method for preparing a composite diaphragm, and the steps are basically the same as those in Example 2, except that:

[0213] Step S1-2. Prepare the first mixed slurry,

[0214] (3) Under stirring conditions at a speed of 500 r / min, 30 g of domestic water was added to the first mixed liquid, and the mixture was stirred for 1 h and then filtered using a 300-mesh filter cloth to obtain a first mixed slurry with a viscosity of 600 mPa·s.

[0215] Example 6

[0216] Example 6 provides a composite membrane consisting of a base membrane, a first coating layer, and a second coating layer;

[0217] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0218] The material and thickness of the base film and the material and thickness of the first coating layer are the same as those in Example 2;

[0219] The active material in the second coating is polyvinylidene fluoride with an average molecular weight of 400,000.

[0220] This embodiment also provides a method for preparing a composite diaphragm, and the steps are the same as those in Example 2, except that the following steps are also included:

[0221] S6-4. Preparation of the second mixed slurry

[0222] At a stirring speed of 500 r / min, polyvinylidene fluoride was dissolved in N-methylpyrrolidone to form a second mixed slurry. The viscosity of the second mixed slurry was 2350 mPa·s.

[0223] S6-5. Apply the second coating

[0224] The second mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this embodiment.

[0225] Comparative Example 1

[0226] Comparative Example 1 provides a method for preparing the composite diaphragm provided in Example 2, and the steps are basically the same as those in Example 2, except that:

[0227] Step S1-1. Preparation of composite electrolyte material:

[0228] (3) Washing: The precursor was centrifuged to obtain a precipitate, which was then washed four times with deionized water.

[0229] Comparative Example 2

[0230] Comparative Example 2 provides a method for preparing the composite diaphragm provided in Example 2. The steps are basically the same as those in Example 2, except that:

[0231] Step S1-2. Preparing the first mixed slurry:

[0232] (1) Preparation of the first active material solution

[0233] At a stirring speed of 500 r / min, 23.2 g of the composite electrolyte material prepared in step S1-1 was added into 62.2 g of a 5% CMC solution at one time to obtain a first active material solution.

[0234] Comparative Example 3

[0235] Comparative Example 3 provides a method for preparing the composite diaphragm provided in Example 2. The steps are basically the same as those in Example 2, except that:

[0236] In step S1-2, in preparing the first mixed slurry, the stirring speed in steps (1), (2) and (3) is 300 r / min.

[0237] Comparative Example 4

[0238] Comparative Example 4 provides a method for preparing the composite diaphragm provided in Example 2. The steps are basically the same as those in Example 2, except that:

[0239] Step S1-2. Preparing the first mixed slurry:

[0240] (2) Preparation of the first mixed solution

[0241] GR-506 (binder), T50 (dispersant), and DC501W (wetting agent) were added to the first active material solution simultaneously at a stirring speed of 500 r / min and stirred for 0.5 h to obtain a first mixed solution. The mass ratio of the composite electrolyte material, GR-508, T50, and DC501W was 1:0.05:0.03:0.01.

[0242] Comparative Example 5

[0243] Comparative Example 5 provides a method for preparing the composite diaphragm provided in Example 2. The steps are basically the same as those in Example 2, except that:

[0244] Step S1-2. Preparing the first mixed slurry:

[0245] (3) Under stirring conditions at a speed of 500 r / min, 30 g of deionized water was added to the first mixed solution and stirring was continued for 1 h to obtain a first mixed slurry with a viscosity of 400 mPa·s.

[0246] Comparative Example 6

[0247] Comparative Example 6 provides a method for preparing the composite diaphragm provided in Example 2. The steps are basically the same as those in Example 2, except that:

[0248] Step S1-1. Preparation of the composite electrolyte material only includes steps (1), (2) and (3), that is, the precipitate obtained after washing is regarded as the composite electrolyte material.

[0249] Comparative Example 7

[0250] Comparative Example 7 provides a composite diaphragm, comprising a base film and a first coating layer coated on one surface of the base film;

[0251] The porosity of the composite membrane is 45%.

[0252] Among them, the base film is PE film with a thickness of 7 μm;

[0253] The active material in the first coating is Li 1.5 Al 0.5 Ge 1.5 P3O 12 (LAGP), with a thickness of 6.5 μm.

[0254] This comparative example also provides a method for preparing the composite diaphragm provided in this comparative example, and the steps are as follows:

[0255] D7-1. Preparation of LAGP mixed slurry

[0256] (1) Preparation of LAGP solution

[0257] Under a stirring speed of 500 r / min, 23.2 g of LAGP was divided into three portions and added to 62.2 g of 5% CMC solution at intervals of 1 h to obtain LAGP solution.

[0258] (2) Preparation of LAGP mixture

[0259] GR-506 (binder), T50 (dispersant), and DC501W (wetting agent) were added to the LAGP solution at a stirring speed of 500 r / min and stirred for 0.5 h to obtain a LAGP mixed solution. The mass ratio of the composite electrolyte material, GR-506, T50, and DC501W was 1:0.05:0.03:0.01.

[0260] (3) Under stirring conditions at a speed of 500 r / min, 30 g of deionized water was added to the LAGP mixture. After stirring for 1 h, the mixture was filtered using a 300-mesh filter cloth to obtain a LAGP mixed slurry with a viscosity of 728 mPa·s.

[0261] D7-2. Apply the first coating

[0262] The LAGP mixed slurry was evenly coated on one surface of the PE base film using a doctor blade coater and dried at 85° C. for 15 minutes to obtain the composite diaphragm provided in this comparative example.

[0263] Comparative Example 8

[0264] Comparative Example 8 provides a composite diaphragm consisting of a base film, a first coating layer and a second coating layer;

[0265] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0266] The material and thickness of the base film and the material and thickness of the first coating layer are the same as those in Comparative Example 7;

[0267] The material and thickness of the second coating layer are the same as those of the first coating layer.

[0268] This comparative example also provides a method for preparing a composite diaphragm, and the steps are basically the same as those of comparative example 7, except that the following steps are also included:

[0269] D8-3. Apply the second coating

[0270] The LAGP mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this comparative example.

[0271] Comparative Example 9

[0272] Comparative Example 9 provides a composite diaphragm consisting of a base film, a first coating layer and a second coating layer;

[0273] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0274] Wherein, the material and thickness of the base film are the same as those in Comparative Example 7;

[0275] The active material in the first coating is polyvinylidene fluoride with an average molecular weight of 400,000.

[0276] The active material in the second coating is polyvinylidene fluoride with an average molecular weight of 400,000.

[0277] This comparative example also provides a method for preparing a composite diaphragm, the steps of which are as follows:

[0278] D9-1. Preparation of polyvinylidene fluoride mixed slurry

[0279] At a stirring speed of 500 r / min, polyvinylidene fluoride was dissolved in N-methylpyrrolidone to form a polyvinylidene fluoride mixed slurry. The viscosity of the polyvinylidene fluoride mixed slurry was 2180 mPa·s.

[0280] D9-2. Apply the first coating

[0281] The polyvinylidene fluoride mixed slurry was evenly coated on one surface of the PE base film using a doctor blade coater and dried at 85° C. for 15 minutes.

[0282] D9-3. Apply the second coating

[0283] The polyvinylidene fluoride mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this comparative example.

[0284] Example 7

[0285] Example 7 provides a composite membrane comprising a base membrane and a first coating layer coated on one surface of the base membrane;

[0286] The porosity of the composite membrane is 45%.

[0287] Among them, the base film is PE film with a thickness of 7 μm;

[0288] The active material in the first coating is a composite electrolyte material with a thickness of 6.5 μm; wherein the composite electrolyte material is composed of Li 1.3 Al 0.3 Ti 1.7 P3O 12 (solid electrolyte, LATP), H3BTC (organic ligand) and lithium nitrate (lithium supplement).

[0289] This embodiment also provides a method for preparing a composite diaphragm, the steps of which are as follows:

[0290] S7-1. Preparation of composite electrolyte materials

[0291] (1) Preparation of a mixture: 42 g of H3BTC was added to 100 ml of methanol and stirred until completely dissolved. The mixture was then mixed with 5 g of lithium nitrate and 33 g of LATP powder and stirred for 6 h at a stirring speed of 490 rpm to obtain a mixture.

[0292] (2) Solvothermal reaction: The mixture was placed in a high-pressure reactor and reacted at 120 °C for 24 h to obtain the precursor.

[0293] (3) Washing: The precursor was centrifuged to obtain a precipitate, which was washed 4 times by centrifugation with methanol and 4 times by centrifugation with deionized water.

[0294] (4) Drying: The washed product was vacuum dried in a forced air drying oven for 8 h at a drying temperature of 85 °C.

[0295] (5) Calcination: The dried product was calcined under argon atmosphere at a temperature of 490 °C for 4 h, and then cooled to room temperature to obtain a composite electrolyte material.

[0296] S7-2. Preparation of the first mixed slurry

[0297] (1) Preparation of the first active material solution

[0298] Under a stirring speed of 500 r / min, 25 g of the composite electrolyte material prepared in step S7-1 was divided into three portions, and each portion was added to 52 g of 5% CMC solution at intervals of 1 hour to obtain a first active material solution.

[0299] (2) Preparation of the first mixed solution

[0300] GR-508 (binder), A-30SL (dispersant), and DC501W (wetting agent) were added to the first active material solution at a stirring speed of 500 r / min and stirred for 0.5 h to obtain a first mixed solution. The mass ratio of the composite electrolyte material, GR-508, A-30SL, and DC501W was 1:0.07:0.05:0.03.

[0301] (3) Under stirring conditions at a speed of 500 r / min, 40 g of deionized water was added to the first mixed liquid, and the mixture was stirred for 1 h and then filtered using a 300-mesh filter cloth to obtain a first mixed slurry with a viscosity of 864 mPa·s.

[0302] S7-3. Apply the first coating

[0303] The first mixed slurry was evenly coated on one surface of the PE base film using a doctor blade coater and dried at 85° C. for 15 minutes to obtain the composite diaphragm provided in this embodiment.

[0304] Example 8

[0305] Example 8 provides a composite membrane consisting of a base membrane, a first coating layer, and a second coating layer;

[0306] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0307] The material and thickness of the base film and the material and thickness of the first coating layer are the same as those in Example 7;

[0308] The material and thickness of the second coating layer are the same as those of the first coating layer.

[0309] This embodiment also provides a method for preparing a composite diaphragm, and the steps are the same as those in Example 7, except that the following steps are also included:

[0310] S8-4. Apply the second coating

[0311] The first mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this embodiment.

[0312] Example 9

[0313] Example 9 provides a composite diaphragm having the same structural composition as that of Example 8.

[0314] This embodiment also provides a method for preparing a composite diaphragm, and the steps are basically the same as those in Example 8, except that:

[0315] Step S7-1. Preparation of composite electrolyte material

[0316] (1) Preparation of a mixture: 42 g of H3BTC, 5 g of lithium nitrate, 33 g of LATP powder and 100 ml of methanol were mixed and stirred for 2 h at a stirring speed of 500 rpm to obtain a mixture.

[0317] Example 10

[0318] Example 10 provides a composite diaphragm having the same structural composition as that of Example 8.

[0319] This embodiment also provides a method for preparing a composite diaphragm, and the steps are basically the same as those in Example 8, except that:

[0320] Step S7-1. Preparation of composite electrolyte material

[0321] (3) Washing: The precursor was centrifuged to obtain a precipitate, which was then washed four times with methanol.

[0322] Example 11

[0323] Example 11 provides a composite diaphragm having the same structural composition as that of Example 8.

[0324] This embodiment also provides a method for preparing a composite diaphragm, and the steps are basically the same as those in Example 8, except that:

[0325] Step S7-2. Prepare the first mixed slurry,

[0326] (3) Under stirring conditions at a speed of 500 r / min, 40 g of domestic water was added to the first mixed liquid, and the mixture was stirred for 1 h and then filtered using a 300-mesh filter cloth to obtain a first mixed slurry with a viscosity of 673 mPa·s.

[0327] Example 12

[0328] Example 12 provides a composite membrane consisting of a base membrane, a first coating layer, and a second coating layer;

[0329] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0330] The material and thickness of the base film and the material and thickness of the first coating layer are the same as those in Example 8;

[0331] The active material in the second coating layer is polyvinylidene fluoride-hexafluoropropylene copolymer with an average molecular weight of 455,000.

[0332] This embodiment also provides a method for preparing a composite diaphragm, and the steps are the same as those in Example 8, except that the following steps are also included:

[0333] S12-4. Preparation of the second mixed slurry

[0334] Under a stirring speed of 500 r / min, α-Acetyl-1-[4-nitropropene]-2-ol was dissolved in N-methylpyrrolidone to form a second mixed slurry. The viscosity of the second mixed slurry was 2563 mPa·s.

[0335] S12-5. Apply the second coating

[0336] The second mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this embodiment.

[0337] Comparative Example 10

[0338] Comparative Example 10 provides a method for preparing the composite diaphragm provided in Example 8. The steps are basically the same as those in Example 8, except that:

[0339] Step S7-1. Preparation of composite electrolyte material:

[0340] (3) Washing: The precursor was centrifuged to obtain a precipitate, which was then washed four times with deionized water.

[0341] Comparative Example 11

[0342] Comparative Example 11 provides a method for preparing the composite diaphragm provided in Example 8. The steps are basically the same as those in Example 8, except that:

[0343] Step S7-2. Preparing a first mixed slurry:

[0344] (1) Preparation of the first active material solution

[0345] At a stirring speed of 500 r / min, 25 g of the composite electrolyte material prepared in step S7-1 was added to 52 g of a 5% CMC solution at one time to obtain a first active material solution.

[0346] Comparative Example 12

[0347] Comparative Example 12 provides a method for preparing the composite diaphragm provided in Example 8. The steps are basically the same as those in Example 8, except that:

[0348] Step S7-2. In preparing the first mixed slurry, the stirring speed in steps (1), (2) and (3) is 300 r / min.

[0349] Comparative Example 13

[0350] Comparative Example 13 provides a method for preparing the composite diaphragm provided in Example 8. The steps are basically the same as those in Example 8, except that:

[0351] Step S7-2. Preparing a first mixed slurry:

[0352] (2) Preparation of the first mixed solution

[0353] GR-508 (binder), A-30SL (dispersant), and DC501W (wetting agent) were added simultaneously to the first active material solution while stirring at 500 r / min. Stirring was continued for 0.5 h to obtain a first mixed solution. The mass ratio of the composite electrolyte material, GR-508, A-30SL, and DC501W was 1:0.05:0.03:0.01.

[0354] Comparative Example 14

[0355] Comparative Example 14 provides a method for preparing the composite diaphragm provided in Example 8. The steps are basically the same as those in Example 8, except that:

[0356] Step S7-2. Preparing a first mixed slurry:

[0357] (3) Under stirring conditions at a speed of 500 r / min, 40 g of deionized water was added to the first mixed solution and stirring was continued for 1 h to obtain a first mixed slurry with a viscosity of 501 mPa·s.

[0358] Comparative Example 15

[0359] Comparative Example 15 provides a method for preparing the composite diaphragm provided in Example 8. The steps are basically the same as those in Example 8, except that:

[0360] Step S7-1. Preparation of the composite electrolyte material only includes steps (1), (2) and (3), that is, the precipitate obtained after washing is regarded as the composite electrolyte material.

[0361] Comparative Example 16

[0362] Comparative Example 16 provides a composite diaphragm, comprising a base film and a first coating layer coated on one surface of the base film;

[0363] The porosity of the composite membrane is 45%.

[0364] Among them, the base film is PE film with a thickness of 7 μm;

[0365] The active material in the first coating is Li 1.3 Al 0.3 Ti 1.7 P3O 12 (LATP), with a thickness of 6.5 μm.

[0366] This comparative example also provides a method for preparing the composite diaphragm provided in this comparative example, and the steps are as follows:

[0367] D16-1. Preparation of LATP mixed slurry

[0368] (1) Preparation of LATP solution

[0369] Under a stirring speed of 500 r / min, 25 g of LATP was divided into three portions and added to 52 g of 5% CMC solution at intervals of 1 h to obtain LATP solution.

[0370] (2) Preparation of LATP mixture

[0371] GR-508 (binder), A-30SL (dispersant), and DC501W (wetting agent) were added to the LATP solution at a stirring speed of 500 r / min and stirred for 0.5 h to obtain a LATP mixed solution. The mass ratio of LATP, GR-508, A-30SL, and DC501W was 1:0.07:0.05:0.03.

[0372] (3) Under stirring conditions at a speed of 500 r / min, 40 g of deionized water was added to the LATP mixture. After stirring for 1 h, the mixture was filtered using a 300-mesh filter cloth to obtain a LATP mixed slurry with a viscosity of 803 mPa·s.

[0373] D16-2. Apply the first coating

[0374] The LATP mixed slurry was evenly coated on one surface of the PE base film using a doctor blade coater and dried at 85° C. for 15 minutes to obtain the composite diaphragm provided in this comparative example.

[0375] Comparative Example 17

[0376] Comparative Example 17 provides a composite diaphragm consisting of a base film, a first coating layer, and a second coating layer;

[0377] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0378] The material and thickness of the base film and the material and thickness of the first coating layer are the same as those in Comparative Example 16;

[0379] The material and thickness of the second coating layer are the same as those of the first coating layer.

[0380] This comparative example also provides a method for preparing a composite diaphragm, and the steps are basically the same as those of comparative example 16, except that the following steps are also included:

[0381] D17-3. Apply the second coating

[0382] The LATP mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this comparative example.

[0383] Comparative Example 18

[0384] Comparative Example 18 provides a composite diaphragm consisting of a base film, a first coating layer, and a second coating layer;

[0385] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0386] The material and thickness of the base film and the thickness of the first coating layer are the same as those in Comparative Example 16;

[0387] The active material in the first coating layer is polyvinylidene fluoride-hexafluoropropylene copolymer with an average molecular weight of 455,000.

[0388] The active material in the second coating layer is polyvinylidene fluoride-hexafluoropropylene copolymer with an average molecular weight of 455,000.

[0389] The thickness of the second coating layer is the same as the thickness of the first coating layer.

[0390] This comparative example also provides a method for preparing a composite diaphragm, the steps of which are as follows:

[0391] D18-1. Preparation of mixed slurry

[0392] Under a stirring speed of 500 r / min, α-D-pyrrolidone was dissolved in N-methylpyrrolidone to form a mixed slurry. The viscosity of the mixed slurry was 2659 mPa·s.

[0393] D18-2. Apply the first coating

[0394] The mixed slurry was evenly coated on one surface of the PE base film using a doctor blade coater and dried at 85° C. for 15 minutes.

[0395] D18-3. Apply the second coating

[0396] The mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this comparative example.

[0397] Example 13

[0398] Example 13 provides a composite membrane comprising a base membrane and a first coating layer coated on one surface of the base membrane;

[0399] The porosity of the composite membrane is 45%.

[0400] Among them, the base film is PE film with a thickness of 7 μm;

[0401] The active material in the first coating is a composite electrolyte material with a thickness of 6.5 μm; wherein the composite electrolyte material is composed of Li2AlTi 0.5 Ge 0.5 P3O 12 (solid electrolyte, LATGP), H3BTC (organic ligand) and lithium nitrate (lithium supplement).

[0402] This embodiment also provides a method for preparing a composite diaphragm, the steps of which are as follows:

[0403] S13-1. Preparation of composite electrolyte materials

[0404] (1) Preparation of a mixture: 31 g of H3BTC was added to 100 ml of methanol and stirred until completely dissolved. The mixture was then mixed with 15 g of lithium nitrate and 15 g of LATGP powder and stirred for 5 h at a stirring speed of 510 rpm to obtain a mixture.

[0405] (2) Solvothermal reaction: The mixture was placed in a high-pressure reactor and reacted at 120 °C for 24 h to obtain the precursor.

[0406] (3) Washing: The precursor was centrifuged to obtain a precipitate, which was washed 4 times by centrifugation with methanol and 4 times by centrifugation with deionized water.

[0407] (4) Drying: The washed product was vacuum dried in a forced air drying oven for 8 h at a drying temperature of 85 °C.

[0408] (5) Calcination: The dried product was calcined under argon atmosphere at a temperature of 510 °C for 3 h, and then cooled to room temperature to obtain a composite electrolyte material.

[0409] S13-2. Preparation of the first mixed slurry

[0410] (1) Preparation of the first active material solution

[0411] Under a stirring speed of 500 r / min, 29 g of the composite electrolyte material prepared in step S13-1 was divided into three portions, and each portion was added to 58 g of 8% CMC solution at intervals of 1 hour to obtain a first active material solution.

[0412] (2) Preparation of the first mixed solution

[0413] GR-816B (binder), A-6114 (dispersant), and DC502W (wetting agent) were added to the first active material solution at a stirring speed of 500 r / min and stirred for 0.5 h to obtain a first mixed solution. The mass ratio of the composite electrolyte material, GR-816B, A-6114, and DC502W was 1:0.1:0.03:0.02.

[0414] (3) Under stirring conditions at a speed of 500 r / min, 37 g of deionized water was added to the first mixed solution. After stirring for 1 h, the mixture was filtered using a 300-mesh filter cloth to obtain a first mixed slurry with a viscosity of 902 mPa·s.

[0415] S13-3. Applying the first coating

[0416] The first mixed slurry was evenly coated on one surface of the PE base film using a doctor blade coater and dried at 85° C. for 15 minutes to obtain the composite diaphragm provided in this embodiment.

[0417] Example 14

[0418] Example 14 provides a composite membrane comprising a base membrane, a first coating layer, and a second coating layer;

[0419] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0420] The material and thickness of the base film and the material and thickness of the first coating layer are the same as those in Example 13;

[0421] The material and thickness of the second coating layer are the same as those of the first coating layer.

[0422] This embodiment also provides a method for preparing a composite diaphragm, and the steps are the same as those of Example 13, except that the following steps are also included:

[0423] S14-4. Applying the second coating

[0424] The first mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this embodiment.

[0425] Example 15

[0426] Example 15 provides a composite diaphragm having the same structural composition as that of Example 14.

[0427] This embodiment also provides a method for preparing a composite diaphragm, and the steps are basically the same as those in Example 14, except that:

[0428] Step S13-1. Preparing a composite electrolyte material,

[0429] (1) Preparation of a mixture: 29 g H3BTC, 15 g lithium nitrate, 15 g LATGP powder and 100 ml methanol were mixed and stirred for 2 h at a stirring speed of 500 rpm to obtain a mixture.

[0430] Example 16

[0431] Example 16 provides a composite diaphragm having the same structural composition as Example 14.

[0432] This embodiment also provides a method for preparing a composite diaphragm, and the steps are basically the same as those in Example 14, except that:

[0433] Step S13-1. Preparation of composite electrolyte material

[0434] (3) Washing: The precursor was centrifuged to obtain a precipitate, which was then washed four times with methanol.

[0435] Example 17

[0436] Example 17 provides a composite diaphragm having the same structural composition as Example 14.

[0437] This embodiment also provides a method for preparing a composite diaphragm, and the steps are basically the same as those in Example 14, except that:

[0438] Step S13-2. Prepare the first mixed slurry,

[0439] (3) Under stirring conditions at a speed of 500 r / min, 37 g of domestic water was added to the first mixed liquid. After stirring for 1 h, the mixture was filtered using a 300-mesh filter cloth to obtain a first mixed slurry with a viscosity of 735 mPa·s.

[0440] Example 18

[0441] Example 18 provides a composite membrane consisting of a base membrane, a first coating layer, and a second coating layer;

[0442] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0443] The material and thickness of the base film and the material and thickness of the first coating layer are the same as those in Example 14;

[0444] The active material in the second coating is polyethylene oxide with an average molecular weight of 600,000.

[0445] This embodiment also provides a method for preparing a composite diaphragm, and the steps are the same as those of Example 14, except that the following steps are also included:

[0446] S18-4. Preparation of the second mixed slurry

[0447] Polyethylene oxide was dissolved in N-methylpyrrolidone at a stirring speed of 500 r / min to form a second mixed slurry. The viscosity of the second mixed slurry was 3587 mPa·s.

[0448] S18-5. Apply the second coating

[0449] The second mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this embodiment.

[0450] Comparative Example 19

[0451] Comparative Example 19 provides a method for preparing the composite diaphragm provided in Example 14, and the steps are substantially the same as those in Example 14, except that:

[0452] Step S13-1. Preparation of composite electrolyte material:

[0453] (3) Washing: The precursor was centrifuged to obtain a precipitate, which was then washed four times with deionized water.

[0454] Comparative Example 20

[0455] Comparative Example 20 provides a method for preparing the composite diaphragm provided in Example 14, and the steps are substantially the same as those in Example 14, except that:

[0456] Step S13-2. Preparing the first mixed slurry:

[0457] (1) Preparation of the first active material solution

[0458] At a stirring speed of 500 r / min, 29 g of the composite electrolyte material prepared in step S13-1 was added to 58 g of 8% CMC solution at one time to obtain a first active material solution.

[0459] Comparative Example 21

[0460] Comparative Example 21 provides a method for preparing the composite diaphragm provided in Example 14, and the steps are substantially the same as those in Example 14, except that:

[0461] Step S13-2. In preparing the first mixed slurry, the stirring speed in steps (1), (2) and (3) is 300 r / min.

[0462] Comparative Example 22

[0463] Comparative Example 22 provides a method for preparing the composite diaphragm provided in Example 14. The steps are substantially the same as those in Example 14, except that:

[0464] Step S13-2. Preparing the first mixed slurry:

[0465] (2) Preparation of the first mixed solution

[0466] GR-816B (binder), A-6114 (dispersant), and DC502W (wetting agent) were added simultaneously to the first active material solution while stirring at 500 r / min. Stirring was continued for 0.5 h to obtain a first mixed solution. The mass ratio of the composite electrolyte material, GR-816B, A-6114, and DC502W was 1:0.1:0.03:0.02.

[0467] Comparative Example 23

[0468] Comparative Example 23 provides a method for preparing the composite diaphragm provided in Example 14. The steps are substantially the same as those in Example 14, except that:

[0469] Step S13-2. Preparing the first mixed slurry:

[0470] (3) Under stirring conditions at a rotation speed of 500 r / min, 37 g of deionized water was added to the first mixed liquid and stirring was continued for 1 h to obtain a first mixed slurry with a viscosity of 487 mPa·s.

[0471] Comparative Example 24

[0472] Comparative Example 24 provides a method for preparing the composite diaphragm provided in Example 14, and the steps are substantially the same as those in Example 14, except that:

[0473] Step S13-1. Preparation of the composite electrolyte material only includes steps (1), (2) and (3), that is, the precipitate obtained after washing is regarded as the composite electrolyte material.

[0474] Comparative Example 25

[0475] Comparative Example 25 provides a composite diaphragm, comprising a base film and a first coating layer coated on one surface of the base film;

[0476] The porosity of the composite membrane is 45%.

[0477] Among them, the base film is PE film with a thickness of 7 μm;

[0478] The active material in the first coating is Li2AlTi 0.5 Ge 0.5 P3O 12 (LATGP), with a thickness of 6.5 μm.

[0479] This comparative example also provides a method for preparing the composite diaphragm provided in this comparative example, and the steps are as follows:

[0480] D25-1. Preparation of LATGP mixed slurry

[0481] (1) Preparation of LATGP solution

[0482] Under a stirring speed of 500 r / min, 29 g of LATGP was divided into three portions and added to 58 g of 8% CMC solution at intervals of 1 h to obtain LATGP solutions.

[0483] (2) Preparation of LATGP mixture

[0484] GR-816B (binder), A-6114 (dispersant), and DC502W (wetting agent) were added to the LATGP solution at 500 r / min and stirred for 0.5 h to obtain a LATGP mixture. The mass ratio of LATGP, GR-816B, A-6114, and DC502W was 1:0.1:0.03:0.02.

[0485] (3) Under stirring conditions at a speed of 500 r / min, 37 g of deionized water was added to the LATGP mixture. After stirring for 1 h, the mixture was filtered using a 300-mesh filter cloth to obtain a LATGP mixed slurry with a viscosity of 874 mPa·s.

[0486] D25-2. Apply the first coating

[0487] The LATGP mixed slurry was evenly coated on one surface of the PE base film using a doctor blade coater and dried at 85° C. for 15 minutes to obtain the composite diaphragm provided in this comparative example.

[0488] Comparative Example 26

[0489] Comparative Example 26 provides a composite diaphragm consisting of a base film, a first coating layer, and a second coating layer;

[0490] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0491] The material and thickness of the base film and the material and thickness of the first coating layer are the same as those in Comparative Example 25;

[0492] The material and thickness of the second coating layer are the same as those of the first coating layer.

[0493] This comparative example also provides a method for preparing a composite diaphragm, and the steps are basically the same as those of comparative example 25, except that the following steps are also included:

[0494] D26-3. Apply the second coating

[0495] The LATGP mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this comparative example.

[0496] Comparative Example 27

[0497] Comparative Example 27 provides a composite diaphragm consisting of a base film, a first coating layer, and a second coating layer;

[0498] The first coating layer is coated on one surface of the base film; the second coating layer is coated on the other surface of the base film away from the first coating layer.

[0499] The material and thickness of the base film and the thickness of the first coating layer are the same as those in Comparative Example 25;

[0500] The active material in the first coating is polyethylene oxide with an average molecular weight of 600,000.

[0501] The active material in the second coating is polyethylene oxide with an average molecular weight of 600,000.

[0502] The thickness of the second coating layer is the same as the thickness of the first coating layer.

[0503] This comparative example also provides a method for preparing a composite diaphragm, the steps of which are as follows:

[0504] D27-1. Preparation of polyethylene oxide mixed slurry

[0505] Polyethylene oxide was dissolved in N-methylpyrrolidone at a stirring speed of 500 r / min to form a polyethylene oxide mixed slurry. The viscosity of the polyethylene oxide mixed slurry was 4012 mPa·s.

[0506] D27-2. Apply the first coating

[0507] The polyethylene oxide mixed slurry was evenly coated on one surface of the PE base film using a doctor blade coater and dried at 85° C. for 15 minutes.

[0508] D27-3. Apply the second coating

[0509] The polyethylene oxide mixed slurry was evenly coated on the other surface of the PE base film away from the first coating layer using a doctor blade coater, and dried at 60° C. for 15 minutes to obtain the composite diaphragm provided in this comparative example.

[0510] In order to verify the progressiveness of a composite diaphragm and a preparation method according to an embodiment of the present invention, the composite diaphragms provided in the embodiments and comparative examples or the composite diaphragms prepared by the provided preparation methods were made into button batteries, and the coulombic efficiency and capacity retention of the batteries were tested on a Land tester. The test results are shown in Tables 1 to 3 below; wherein, Table 1 is the results of Examples 1 to 6 and Comparative Examples 1 to 9; Table 2 is the results of Examples 7 to 12 and Comparative Examples 10 to 18; and Table 3 is the results of Examples 13 to 18 and Comparative Examples 19 to 27. The composite electrolyte materials prepared in Example 1, Example 7, Example 13, Comparative Example 1, Comparative Example 10 and Comparative Example 19 were scanned using a transmission electron microscope. The TEM images of the composite electrolyte materials obtained by scanning are shown in FIG. Figures 2 to 7 Taking Example 2, Example 8, Example 14, Comparative Example 8, Comparative Example 9, Comparative Example 17, Comparative Example 18, Comparative Example 26 and Comparative Example 27 as examples, the prepared button batteries were subjected to EIS impedance testing, and the test results are shown as follows: Figure 8 、 9 and 10.

[0511] The preparation of button cells is as follows:

[0512] A CR2032 button cell was assembled in an argon-protected glove box using NCM811 as the positive electrode, metallic lithium as the negative electrode, a composite membrane as the separator, and 1 mol / L LiPF6 (volume ratio of ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1:1:1) as the electrolyte.

[0513] Table 1

[0514]

[0515] Table 2

[0516]

[0517] Table 3

[0518]

[0519] From the above table and the accompanying drawings, we can at least draw the following conclusions:

[0520] (1) The solid electrolyte selected for the composite diaphragms provided in Examples 1 to 6 is LAGP. The coulombic efficiency and capacity retention rate of the button batteries prepared are higher than those of Examples 7 to 12 (LATP) and Examples 13 to 16 (LATGP), indicating that the coating made of LAGP has good stability and effectively improves the capacity and cycle stability of the battery.

[0521] (2) Comparing the coulombic efficiency and capacity retention of Example 2 and Comparative Examples 1 to 6 (or Comparative Example 8 and Comparative Examples 10 to 15, or Comparative Example 14 and Comparative Examples 19 to 24), it can be seen that in the preparation method of the composite diaphragm provided by the embodiment of the present invention, the washing detergent, the mixing method of the composite electrolyte material and the CMC solution, the rotation speed of the slurry preparation, the ratio between the components in the mixed solution, the viscosity of the slurry, etc., all have an impact on the performance of the composite diaphragm prepared. The composite diaphragm prepared by the preparation method of the composite diaphragm provided by the embodiment of the present invention, the composite electrolyte material containing the in-situ doped MOF material in the coating layer can effectively improve the lithium ion (Li + )'s conductivity, and also improves the structural stability and mechanical strength of the diaphragm.

[0522] (3) By Figure 8 、 Figure 9 and Figure 10 It can be seen that in the low-frequency region, the impedance value is low and the slope of each curve is large, indicating that the impedance increases rapidly with increasing frequency. This is usually because the inductance effect dominates at low frequencies. The impedance values ​​of the embodiments in the low-frequency region are relatively low, and the impedance values ​​of the comparative examples are relatively high. In the high-frequency region, the impedance value tends to be stable and the slope decreases, which indicates that the inductance effect weakens and the capacitance effect may begin to dominate. The impedance values ​​of the embodiments in the high-frequency region are relatively low, and the impedance values ​​of the comparative examples are relatively high. This shows that after double-sided coating of the composite MOF material, the impedance can be effectively reduced, and at the same time, the liquid absorption capacity is greater, which can significantly improve its charge transfer ability and cycle stability.

[0523] It should be noted that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the technical solution of the present invention are all included in the technical scope of the present invention. In addition, without departing from the scope of the present invention, other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present invention.

Claims

1. A composite diaphragm, characterized in that: It includes a base film and a first coating layer coated on one surface of the base film; The porosity of the composite membrane is 45% to 87%; The base film is at least one of a PE film, a PP film, a polyethylene-polypropylene composite film, and a PI film; The raw material of the first coating layer includes a first active material, and the first active material includes a composite electrolyte material; The raw materials of the composite electrolyte material include solid electrolyte, organic ligand and lithium supplement agent; The chemical formula of the solid electrolyte is as follows: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> A<h2 style=";text-align:left;direction:ltr"> m <h2 style=";text-align:left;direction:ltr"> B<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> PO<h2 style=";text-align:left;direction:ltr"> e <h2 style=";text-align:left;direction:ltr"> ; wherein 0<x≤3, 0<y≤2, 0≤m<2, 0≤n<2, 4≤e≤6.5, m and n are not simultaneously 0, A is at least one element of Group IVA, and B is at least one element of Group IVB; The organic ligand includes at least one of trimesic acid, 2-methylimidazole, terephthalic acid, 2,5-dihydroxyterephthalic acid, and 3,3',5,5'-biphenyltetracarboxylic acid; The lithium supplement comprises at least one of lithium nitrate, lithium chloride, lithium acetate, lithium hydroxide, and lithium oxide; The preparation of the composite electrolyte material comprises the following steps: The mixture is subjected to a solvothermal reaction, and then washed, dried and calcined to obtain a composite electrolyte material; The mixture contains an organic ligand, a lithium supplement and a solid electrolyte.

2. The composite diaphragm according to claim 1, characterized in that The solid electrolyte is: Li 1.5 Al 0.5 Ge 1.5 P3O 12 、Li 1.3 Al 0.3 Ti 1.7 P3O 12 or Li2AlTi 0.5 Ge 0.5 P3O 12 .

3. The composite diaphragm according to claim 1, characterized in that The thickness of the composite diaphragm is 7 μm to 31 μm.

4. The composite diaphragm according to any one of claims 1 to 3, characterized in that: The composite diaphragm further includes a second coating; The raw material of the second coating layer includes a second active material; the second active material includes at least one of the composite electrolyte material, polyvinylidene fluoride, polymethyl methacrylate, polyvinylidene fluoride-hexafluoropropylene copolymer, polyaniline, polyethylene oxide, and aramid; The second coating layer is applied to the other surface of the base film that is away from the first coating layer.

5. The composite diaphragm according to claim 4, characterized in that Satisfy at least one of the following conditions (1) to (2): (1) The thickness of the first coating is 2 μm to 7 μm; (2) The thickness of the second coating layer is 2 μm to 7 μm.

6. A method for preparing a composite diaphragm, characterized in that: The steps include: Applying the first mixed slurry on the surface of the base film and forming a first coating after drying to obtain a composite diaphragm; The first mixed slurry contains a first active material and a first auxiliary agent; The first active material includes a composite electrolyte material; The raw materials of the composite electrolyte material include solid electrolyte, organic ligand and lithium supplement agent; The chemical formula of the solid electrolyte is as follows: <h2 style=";text-align:left;direction:ltr">Li<h2 style=";text-align:left;direction:ltr"> x <h2 style=";text-align:left;direction:ltr"> Al<h2 style=";text-align:left;direction:ltr"> y <h2 style=";text-align:left;direction:ltr"> A<h2 style=";text-align:left;direction:ltr"> m <h2 style=";text-align:left;direction:ltr"> B<h2 style=";text-align:left;direction:ltr"> n <h2 style=";text-align:left;direction:ltr"> PO<h2 style=";text-align:left;direction:ltr"> e <h2 style=";text-align:left;direction:ltr"> ; wherein 0<x≤3, 0<y≤2, 0≤m<2, 0≤n<2, 4≤e≤6.5, m and n are not simultaneously 0, A is at least one element of Group IVA, and B is at least one element of Group IVB; The organic ligand includes at least one of trimesic acid, 2-methylimidazole, terephthalic acid, 2,5-dihydroxyterephthalic acid, and 3,3',5,5'-biphenyltetracarboxylic acid; The lithium supplement comprises at least one of lithium nitrate, lithium chloride, lithium acetate, lithium hydroxide, and lithium oxide; The first auxiliary agent includes at least one of a wetting agent, a plasticizer, a dispersant, a binder, an anti-settling agent, a defoaming agent, and a pore-forming agent; The preparation of the composite electrolyte material comprises the following steps: The mixture is subjected to a solvothermal reaction, and then washed, dried and calcined to obtain a composite electrolyte material; The mixture contains an organic ligand, a lithium supplement and a solid electrolyte.

7. The method for preparing a composite diaphragm according to claim 6, characterized in that: The mass ratio of the first active material to the first auxiliary agent is 1:0.01-0.

15.

8. The method for preparing a composite diaphragm according to any one of claims 6 to 7, characterized in that: The preparation method of the composite diaphragm further comprises the following steps: applying a second mixed slurry on the other surface of the base film away from the first coating layer, and drying to obtain a composite diaphragm; The second mixed slurry contains a second active material and a second auxiliary agent; The second active material comprises at least one of the composite electrolyte material, polyvinylidene fluoride, polymethyl methacrylate, polyvinylidene fluoride-hexafluoropropylene copolymer, polyaniline, polyethylene oxide, and aramid; The second auxiliary agent includes at least one of a wetting agent, a plasticizer, a dispersant, a binder, an anti-settling agent, a defoaming agent, and a pore-forming agent.

9. Use of the composite separator according to any one of claims 1 to 5 in the field of battery material technology.

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