Solid-state battery diaphragm as well as preparation method and application thereof

Abstract

The invention discloses a solid-state battery diaphragm as well as a preparation method and application thereof, and relates to the technical field of secondary batteries. The polymer porous layer is arranged on the surface of the solid electrolyte diaphragm, the polymer porous layer is formed by coating and plasticizing the high-swelling resin and the lithium salt compound slurry, the polymer porous layer has excellent compatibility to the solid electrolyte diaphragm and a pole piece, and the polymer porous layer contains the lithium salt component, so that the ionic conductivity can be improved. The resin component of the diaphragm has high viscosity, by filling part of electrolyte, the polymer porous layer keeps a gel state, the flexibility of the diaphragm is better, a viscoelastic gel state is formed, the diaphragm can be bonded or filled with a cracked area in a solid electrolyte film or a pole piece, and the polymer porous layer contains a lithium salt component, so that effective repair can be realized.

Description

Technical Field

[0001] This application relates to the technical field of secondary batteries, and particularly relates to a solid-state battery separator and its preparation method and application. Background Art

[0002] Currently, traditional lithium batteries all use liquid organic electrolytes, which have problems such as electrolyte leakage and combustion. While solid-state batteries use solid electrolyte materials, avoiding flammable organic liquid electrolytes and greatly improving battery safety. At the same time, using solid electrolytes can effectively match lithium metal anodes and effectively inhibit the growth of lithium dendrites, so they are also significantly superior to traditional liquid lithium batteries in terms of energy density.

[0003] However, the application of solid-state batteries still needs to solve some key scientific problems: (1) Low ionic conductivity. The ionic conductivity of solid electrolyte materials is relatively low, which in turn limits the rate performance and power density. The ionic conductivity of liquid electrolytes is about 10-2 S / cm, while that of solid electrolytes is 10-8 to 10-4 S / cm. (2) Poor interfacial compatibility, with large interfacial impedance and low interfacial affinity between the solid electrolyte and the positive and negative electrodes. Therefore, how to solve the ionic conductivity of solid electrolytes and improve interfacial compatibility is crucial. Summary of the Invention

[0004] The purpose of this application is to provide a solid-state battery separator and its preparation method and application. Aiming at the low ionic conductivity and poor interfacial matching of solid electrolyte films, it can not only improve the ionic conductivity of the battery, but also improve the interfacial affinity between the solid electrolyte film and the electrode sheet.

[0005] To achieve the above purpose, the embodiments of this application adopt the following technical solutions: A solid-state battery separator, comprising: a solid electrolyte film, which is obtained by casting and shaping an oxide ceramic slurry and then sintering at high temperature; a polymer porous layer, which is disposed on both surface sides of the solid electrolyte film, and the polymer porous layer is formed by coating and plasticizing a compound slurry of a highly swellable resin and a lithium salt.

[0006] In the above technical solution, in the embodiments of this application, by disposing a polymer porous layer on the surface of the solid electrolyte separator, the polymer porous layer is formed by coating and plasticizing a compound slurry of a highly swellable resin and a lithium salt, which has excellent compatibility with both the solid electrolyte membrane and the electrode sheet, and contains lithium salt components itself, which can improve ionic conductivity. The resin component of the separator has high viscosity. By filling in part of the electrolyte, the polymer porous layer remains in a gel state, has good flexibility itself, forms a viscoelastic gel state, can bond or fill the areas with cracks that have appeared in the solid electrolyte film or the electrode sheet, and combined with the fact that the polymer porous layer contains lithium salt components, effective repair can be achieved.

[0007] Further, according to an embodiment of the present application, the average thickness A of the solid electrolyte film satisfies 20 μm ≤ A ≤ 80 μm.

[0008] Further, according to an embodiment of the present application, the average thickness a of the polymer porous layer satisfies 12 μm ≤ a ≤ 21 μm.

[0009] Further, according to an embodiment of the present application, the solid electrolyte film includes solid electrolyte particles, and the average particle size D of the solid electrolyte particles satisfies 0.01 μm ≤ D ≤ 5 μm.

[0010] Further, according to an embodiment of the present application, the average pore diameter d of the solid-state battery separator satisfies 0.1 μm ≤ d ≤ 2 μm.

[0011] Further, according to an embodiment of the present application, the highly swellable resin includes one or more of polyvinylidene fluoride, polymethyl methacrylate, aramid, furan polyamide, polyimide, and polyacrylonitrile.

[0012] Further, according to an embodiment of the present application, the mass ratio of the highly swellable resin in the polymer porous layer is 50 wt% - 90 wt%.

[0013] Further, according to an embodiment of the present application, the lithium salt includes LiPF 6 , LiClO 4 , LiBF 4 , LiAsF 6 , LiFSI, LiTFSI, LiCl, or one or more thereof.

[0014] Further, according to an embodiment of the present application, the porosity of the polymer porous layer is 30% - 70%.

[0015] To achieve the above object, an embodiment of the present application also discloses a method for preparing a solid-state battery separator, including the following steps: Flowing a mixed solution containing solid electrolyte particles and a binder onto a polyester film substrate by doctor blade casting, peeling it off after the solvent volatilizes to obtain a green film, and sintering it at 1260 °C to obtain a dense and high-strength solid electrolyte film; Coating a mixed coating solution containing a highly swellable resin and a lithium salt on both side surfaces of the solid electrolyte film, and forming a polymer porous layer after high-temperature plasticization of the coating.

[0016] Further, according to an embodiment of the present application, the coating method of the coating solution required for the polymer porous layer is preferably microgravure coating, and the coating solution is coated on both sides of the solid electrolyte film simultaneously.

[0017] To achieve the above object, an embodiment of the present application also discloses an application of a solid-state battery separator on a secondary battery. Compared with the prior art, the present application has the following beneficial effects: By providing a polymer porous layer on the surface of the solid electrolyte separator, the polymer porous layer is formed by coating and plasticizing a compound slurry of a highly swellable resin and a lithium salt, which has excellent compatibility with both the solid electrolyte membrane and the electrode sheet, and contains lithium salt components itself, which can improve the ionic conductivity. The resin component of the separator has high viscosity. By filling part of the electrolyte, the polymer porous layer remains in a gel state, has good flexibility itself, forms a viscoelastic gel state, can bond or fill the cracked areas in the solid electrolyte film or the electrode sheet, and combined with the lithium salt component in the polymer porous layer, effective repair can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present application will be further described below in conjunction with the drawings and embodiments.

[0019] Figure 1 It is a schematic diagram of cracks in the solid electrolyte film layer.

[0020] Figure 2 It is a schematic diagram of the solid electrolyte layer remaining after removing the polymer porous layer after the separator prepared in Example 1 is injected with liquid and swelled for 48 h. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] In order to clearly and completely describe the object, technical solution of the present invention and make the advantages more clear, the embodiments of the present invention will be further described in detail below in conjunction with the drawings. It should be understood that the specific embodiments described herein are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to explain the embodiments of the present invention, and are not used to limit the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "center", "middle", "upper", "lower", "left", "right", "inner", "outer", "top", "bottom", "side", "vertical", "horizontal", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, the terms "one", "first", "second", "third", "fourth", "fifth", "sixth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0023] In the description of the present invention, it should be noted that, unless otherwise clearly defined and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] For the sake of simplicity and illustration, the principles of the embodiments are mainly described by referring to examples. In the following description, many specific details are set forth to provide a thorough understanding of the embodiments. However, it is obvious that for those of ordinary skill in the art, these embodiments may not be limited to these specific details in practice. In some instances, well-known methods and structures are not described in detail to avoid unnecessarily obscuring these embodiments. Additionally, all embodiments can be used in combination with each other.

[0025] The present application discloses a solid-state battery separator, comprising: a solid electrolyte film, which is obtained by casting and molding an oxide ceramic slurry and then sintering at a high temperature; and a polymer porous layer, which is disposed on both side surfaces of the solid electrolyte film, and the polymer porous layer is formed by coating and plasticizing a compound slurry of a highly swellable resin and a lithium salt.

[0026] Specifically, the average thickness A of the solid electrolyte film satisfies 20μm ≤ A ≤ 80μm, and it contains solid electrolyte particles with an average particle size D satisfying 0.01μm ≤ D ≤ 5μm. The average thickness a of the polymer porous layer satisfies 12μm ≤ a ≤ 21μm, and the average pore size d of the separator satisfies 0.1μm ≤ d ≤ 2μm.

[0027] Regarding the solid electrolyte film, in order to ensure that the solid electrolyte film has a low impedance, its thickness A must satisfy 20μm ≤ A ≤ 80μm. If A < 20μm, the solid electrolyte film will increase the risk of battery short circuit, and it is difficult to achieve in the preparation process of inorganic solid electrolytes; if A > 80μm, the solid electrolyte film itself has a large impedance, which is not conducive to improving the ionic conductivity of the battery. Preferably, it is more than 20μm and less than 40μm. In the particle size distribution based on volume, the particle size at which the volume accumulation reaches 50% starting from the small particle size side is called the average particle size (D50) of the spherical filler. If the average particle size D50 of the solid electrolyte particles < 0.01μm, the particles are not easy to form a film and are prone to agglomeration. If D50 > 5μm, the particles are too large, and the film may have cracks, which has a destructive effect on the solid electrolyte film.

[0028] Regarding the polymer porous layer, in order to ensure its interfacial compatibility and form a viscoelastic gel state, its average thickness a satisfies 12 μm ≤ a ≤ 21 μm. If a < 12 μm, the volume of the polymer porous layer that forms a viscoelastic gel state is small and cannot effectively repair the crack area. If a > 21 μm, the volume of the polymer porous layer is too large, squeezing the space of other components inside the battery and reducing the battery performance.

[0029]

Solid electrolyte film

[0030] The solid electrolyte film is required to have high ionic conductivity and appropriate toughness, and the inorganic solid electrolyte membrane has high ionic conductivity. Considering from the perspective of high ionic conductivity, the oxide ceramic solid electrolyte membrane has good ionic conductivity and can be used as a preferred option.

[0031] The oxide ceramic solid electrolyte film can be manufactured by the following method: cast the oxide ceramic slurry on a polyester film substrate with a doctor blade, peel off the obtained green film after the solvent volatilizes, and obtain a dense and high-strength solid electrolyte film after sintering at 1260 °C.

[0032]

Polymer porous layer

[0033] In order to ensure the ionic conductivity of the solid electrolyte film and the interfacial affinity of the polymer porous layer, the thickness of the polymer porous layer is maintained at 12 μm to 21 μm, preferably 12 μm to 20 μm; being greater than 12 μm can ensure the effective repair of the damaged electrode or solid electrolyte membrane by the separator, and being less than 21 μm can maintain the occupied space of the positive and negative electrodes of the lithium battery.

[0034] Considering the shuttle efficiency of lithium ions, the porosity of the polymer porous layer is 30% - 70%. Below 70%, the stability of the skeleton structure of the polymer porous layer can be ensured, and above 30%, the shuttle efficiency of lithium ions can be ensured.

[0035] The pore size distribution of the polymer porous layer is 20 nm to 2000 nm. With the pore size below 2000 nm, the local uniformity of the pores can be ensured, the adhesion difference is small, and above 20 nm, lithium ions can easily pass through and are not easily blocked, ensuring the lithium ion permeability.

[0036] Considering ensuring the ionic conductivity of the solid electrolyte film and the interfacial affinity of the polymer porous layer, the areal density of the polymer porous layer on both sides totals 28.8 g / m 2 ~50.4 g / m 2 and the areal density on one side is 14.4 g / m 2 ~24.0 g / m 2 .

[0037] As the polymer coating with lithium ions, polyacrylic acid, polyvinylidene fluoride, polyacrylonitrile resin composite with lithium ions, etc. can be selected; as the filler with lithium ions, materials such as surface-modified silica, alumina, molecular sieve, etc. can be selected; as the lithium salt, LiPF 6 , LiClO 4 , LiBF 4 , LiAsF 6 , LiFSI, LiTFSI, LiCl, etc. can be selected. For the superposition of the multifunctional coating, methods such as coating, dipping, spraying the coating can be used.

[0038]

High-swelling resin

[0039] The high-swelling resin is preferably a polymethyl methacrylate copolymer (synthesized from acrylonitrile and methyl acrylate, molar ratio 5 / 5, weight-average molecular weight of 200,000), and the polymethyl methacrylate copolymer has high swelling. For example, when the electrolyte is EC:PC:DEC:EP = 3:1:3:3 (1M LiPF 6 ), the swelling is as high as 85.67%; when EC:EMC:DEC (1M LiPF 6 ) = 3:5:2, the swelling reaches 48.97%, and when the electrolyte is EC:PC:DEC = 1:1:1, the swelling is as high as 126.22%.

[0040] After the high-swelling resin forms a coating through the coagulation bath, its electrolyte absorption rate is relatively large. When the electrolyte is EC:PC:DEC:EP = 3:1:3:3 (1M LiPF 6When it is (), its liquid absorption rate reaches 68.16%; when EC:EMC:DEC = 3:5:2, the liquid absorption rate reaches 75.23%; when the electrolyte is EC:PC:DEC = 1:1:1, its liquid absorption rate reaches 69.20%.

[0041] The mass ratio of the highly swelling resin in the polymer porous layer is 50wt% - 90wt%.

[0042]

Lithium salt

[0043]

Preparation method of non-aqueous secondary battery separator

[0044] The mixed coating solution containing the highly swelling resin and the lithium salt is coated on the solid electrolyte film, and a polymer porous layer is formed after high-temperature plasticization of the coating.

[0045] The solvents of the mixture required for the solid electrolyte film and the coating solution required for the polymer porous layer are preferably polar solvents, such as N-methylpyrrolidone, dimethylformamide, dimethylacetamide, etc.

[0046] In the coating solution required for the polymer porous layer, in order to form a good pore structure, the mass ratio of the highly swelling resin is 50wt% - 90wt%.

[0047] In the coating liquid required for the polymer porous layer, the addition of a lithium salt can effectively improve the pore-forming effect of the separator while having little impact on the adhesiveness of the polymer porous layer. The proportion of the lithium salt in the total amount of the lithium salt and the highly swellable resin is 10 wt% - 50 wt%.

[0048] The coating method of the coating liquid required for the polymer porous layer is preferably microgravure coating, and the coating liquid is coated on both sides of the solid electrolyte film simultaneously.

[0049]

Non-aqueous secondary battery

[0050] The positive electrode is composed of a lithium-containing active material, a conductive agent, and an adhesive that bonds and adheres the two to the current collector.

[0051] The positive electrode active material is a lithium salt-containing metal oxide, including lithium iron phosphate, lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, etc.

[0052] The adhesive can be polyvinylidene fluoride, polymethyl methacrylate, polyacrylonitrile, etc.

[0053] The conductive agent can be traditional conductive agents such as carbon black, conductive graphite, carbon fiber, etc. and new conductive agents such as carbon nanotubes, graphene, etc.

[0054] The current collector can be aluminum foil, titanium foil, etc. with a thickness of 5 - 20 μm.

[0055] Since the aforementioned non-aqueous secondary separator is a combination of a solid electrolyte film and a polymer porous layer, the separator has high safety, high ionic conductivity, and high energy density lithium nickel cobalt manganate, etc. can be used as the positive electrode material.

[0056] The negative electrode is composed of an active material, a conductive agent, and an adhesive that bonds and adheres the two to the current collector.

[0057] The negative electrode material is mainly an active material that can adsorb or insert lithium ions, including carbon materials, silicon-carbon composites, lithium alloys, lithium metals, etc.

[0058] The adhesive is polyvinylidene fluoride, styrene-butadiene rubber, etc.

[0059] The conductive agent can be traditional conductive agents such as carbon black, conductive graphite, carbon fiber, etc. and new conductive agents such as carbon nanotubes, graphene, etc.

[0060] The current collector can be aluminum foil, titanium foil, etc. with a thickness of 5 - 20 μm.

[0061] The electrolyte is a solution obtained by dissolving a lithium salt in one or several solvents such as cyclic carbonates, chain carbonates, carboxylic acid esters, etc.

[0062] The lithium salts can be selected from LiPF6, LiClO 4 , LiBF 4 , LiAsF 6 , LiFSI, LiTFSI, LiCl, etc.

[0063] The solvents include cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, and carboxylic acid esters including methyl acetate, ethyl acetate, methyl formate, methyl propionate, ethyl propionate, etc.

[0064] In the present invention, the non-aqueous secondary battery separator has good wettability to various electrolytes, is based on a solid electrolyte membrane, and contains a polymer porous layer formed by plasticizing a highly swellable resin and a lithium salt, has high ionic conductivity, high interfacial affinity, and can repair damaged electrode sheets or solid electrolyte membranes.

[0065] The materials for encapsulating the battery can be aluminum cases, steel cases, aluminum-plastic films, and steel-plastic films. The battery shape can be square, cylindrical, or soft-packaged. In the present invention, the cylindrical shape is mostly used.

[0066] Method for manufacturing a non-aqueous secondary battery: Wind or laminate the positive electrode, negative electrode, and the non-aqueous secondary battery separator of the present invention, perform hot pressing and shaping on the battery core, then encapsulate it into the encapsulating material, and finally inject a small amount of electrolyte.

[0067]

Examples, Test Methods, and Test Results

[0068] Fabrication of the separator: A mixed solution containing an oxide conductive ceramic and a binder is cast onto a polyester film substrate by a doctor blade. After the solvent evaporates, the green film is peeled off and sintered at 1260 °C to obtain a dense and strong solid electrolyte film. As the highly swellable resin, a copolymer synthesized by aqueous phase precipitation of acrylonitrile and methyl acrylate (molar ratio 5 / 5, weight average molecular weight of 200,000) is used, designated as resin A. Resin A is dissolved in N-methylpyrrolidone. The lithium salt LiClO 4 is dissolved in the above solution to form a coating solution, wherein the ratio of the lithium salt to resin A is 1:4. The solid content of the coating solution is 12.20%, and the lithium salt accounts for 20% of the total amount of it and resin A. The coating solution is equally coated on both sides of the solid electrolyte film (film thickness 30 μm) and placed in an oven, dried at 80 °C for 3 h. During the whole process, the relative humidity is controlled by a humidity chamber, and the relative humidity (20 °C) is 1.0%. Under the conditions of low humidity and high temperature, the lithium salt / highly swellable resin mixture directly undergoes nanophase separation in the air to form a micro-nano pore structure and is plasticized into a polymer porous layer, and the lithium salt is directly retained in the porous layer. The thickness of the polymer porous layer is 12 μm.

[0069] Before battery assembly, further drying treatment is required. The separator is placed in a vacuum oven and dried at 60 °C for 10 h to ensure that the separator is completely dry before assembling the battery.

[0070] Fabrication of the Battery Fabrication of the negative electrode: Artificial graphite rich in negative electrode active material, styrene-butadiene rubber as the binder, carbon black as the conductive agent, and an appropriate amount of water are used to prepare a slurry for the negative electrode. The negative electrode slurry is coated on a 10-μm copper foil serving as the current collector, and after drying and pressing, a negative electrode with a negative electrode active material layer is obtained.

[0071] Fabrication of the positive electrode: Lithium iron phosphate as the positive electrode active material, carbon black as the conductive agent, and polyvinylidene fluoride as the binder are stirred to form a slurry. The positive electrode slurry is coated on a 20-μm aluminum foil serving as the current collector, and after drying and pressing, a positive electrode with a positive electrode active material layer is obtained.

[0072] Tab ears are welded to the positive and negative electrodes, and winding is carried out in the order of positive electrode, separator, negative electrode, and separator to manufacture an electrode assembly. The electrode assembly is subjected to hot pressing and shaping, then encapsulated in a steel shell material, and finally electrolyte is injected. The electrolyte is 1 M LiPF 6 -ethylene carbonate / ethyl methyl carbonate / diethyl carbonate (mass ratio 3 / 5 / 2). The conditions for hot pressing are set as 3 MPa, a hot pressing temperature of 95 °C, and a hot pressing time of 5 min.

[0073] The physical properties of the filler, the physical property values of the battery, and the evaluation in Example 1 are listed in Table 2. Example

[0074] As shown in Table 1, a copolymer (molar ratio 7 / 3, weight average molecular weight of 300,000) synthesized by aqueous precipitation method using acrylonitrile and methyl acrylate (referred to as resin B) is used to replace resin A. Except for this, the separator of Example 2 is fabricated in the same manner as in Example 1.

[0075] The rest is the same as in Example 1, and a test battery of Example 2 is fabricated.

[0076] The physical properties of the filler, the physical property values of the battery, and the evaluation in Example 2 are listed in Table 2. Example

[0077] As shown in Table 1, the average thickness of the polymer porous layer is changed. Except for this, the separator of Example 3 is fabricated in the same manner as in Example 1.

[0078] The rest is the same as in Example 1, and a test battery of Example 3 is fabricated.

[0079] The physical properties of the filler, the physical property values of the battery, and the evaluation in Example 3 are listed in Table 2. Example

[0080] As shown in Table 1, 1,1-difluoroethylene was polymerized to form polyvinylidene fluoride (weight-average molecular weight of 300,000) (referred to as Resin C) to replace Resin A. Except for this, the separator of Example 4 was produced in the same manner as in Example 1.

[0081] In the same manner as in Example 1, a test battery of Example 4 was produced.

[0082] The physical properties of the filler of Example 4, the physical property values of the battery, and the evaluations are listed in Table 2. Example

[0083] As shown in Table 1, the relative humidity (20 °C) was changed. Except for this, the separator of Example 5 was produced in the same manner as in Example 1.

[0084] In the same manner as in Example 1, a test battery of Example 5 was produced.

[0085] The physical properties of the filler of Example 5, the physical property values of the battery, and the evaluations are listed in Table 2. Example

[0086] As shown in Table 1, the type of lithium salt was changed, and LiClO 4 was replaced with LiCl. Except for this, the separator of Example 6 was produced in the same manner as in Example 1.

[0087] In the same manner as in Example 1, a test battery of Example 6 was produced.

[0088] The physical properties of the filler of Example 6, the physical property values of the battery, and the evaluations are listed in Table 2. Example

[0089] As shown in Table 1, the type of lithium salt was changed, and LiClO 4 was replaced with LiTFSI. Except for this, the separator of Example 7 was produced in the same manner as in Example 1.

[0090] In the same manner as in Example 1, a test battery of Example 7 was produced.

[0091] The physical properties of the filler of Example 7, the physical property values of the battery, and the evaluations are listed in Table 2. Example

[0092] As shown in Table 1, the ratio of lithium salt to the highly swellable resin was changed. Except for this, the separator of Example 8 was produced in the same manner as in Example 1.

[0093] In the same manner as in Example 1, a test battery of Example 8 was produced.

[0094] The physical properties of the filler of Example 8, the physical property values of the battery, and the evaluations are listed in Table 2.

[0095] Comparative Example 1 As shown in Table 1, acrylonitrile was used to polymerize polyacrylonitrile (weight average molecular weight of 500,000) (referred to as Resin D) to replace Resin A. Except for this, it was the same as Example 1. Except for this, it was the same as Example 1. The separator of Comparative Example 1 was produced.

[0096] The test battery of Comparative Example 1 was produced in the same manner as in Example 1.

[0097] The physical properties of the filler of Comparative Example 1, as well as the physical property values and evaluations of the battery, are listed in Table 2.

[0098] Comparative Example 2 As shown in Table 1, the relative humidity (20 °C) was changed. Except for this, it was the same as Example 1. The separator of Comparative Example 2 was produced.

[0099] The test battery of Comparative Example 2 was produced in the same manner as in Example 1.

[0100] The physical properties of the filler of Comparative Example 2, as well as the physical property values and evaluations of the battery, are listed in Table 2.

[0101] Comparative Example 3 As shown in Table 1, the type of lithium salt was changed, and LiClO was not added 4 , and except for this, it was the same as Example 1. The separator of Comparative Example 3 was produced.

[0102] The test battery of Comparative Example 3 was produced in the same manner as in Example 1.

[0103] The physical properties of the filler of Comparative Example 3, as well as the physical property values and evaluations of the battery, are listed in Table 2.

[0104] Comparative Example 4 As shown in Table 1, the ratio of lithium salt to high-swelling resin was changed. Except for this, it was the same as Example 1. The separator of Comparative Example 4 was produced.

[0105] The test battery of Comparative Example 4 was produced in the same manner as in Example 1.

[0106] The physical properties of the filler of Comparative Example 4, as well as the physical property values and evaluations of the battery, are listed in Table 2.

[0107] Test method Solid electrolyte membrane and polymer porous layer thickness: The average thickness of the polymer porous layer was set as the average thickness of the separator minus the average thickness of the solid electrolyte membrane. If the polymer porous layer was provided on both sides of the porous substrate, it was set as (the average thickness of the separator minus the average thickness of the solid electrolyte membrane) divided by 2. For the measurement of the thickness of the separator and the solid electrolyte membrane, 8 layers of the separator or the solid electrolyte membrane were overlapped, and 10 points were randomly selected on an area of 10 cm × 10 cm by a Mar thickness gauge, and the average was taken and then divided by 8 to obtain the thickness.

[0108] Areal density: The average areal density of the polymer porous layer is set as the average areal density of the separator minus the areal density of the solid electrolyte membrane. If the polymer porous layer is provided on both sides of the solid electrolyte membrane, it is obtained by dividing the average areal density of the separator minus the average areal density of the solid electrolyte membrane by 2. For the measurement of the areal density of the separator and the solid electrolyte membrane, 8 pieces of 10 cm x 10 cm separator or solid electrolyte membrane are stacked on an analytical balance for weighing, and after removing the area, it is divided by 8 to obtain the areal density.

[0109] Solid electrolyte particle size distribution: The solid electrolyte is dispersed in pure water, stirred, and then ultrasonically dispersed. The particle size is measured using a laser particle size distribution analyzer (Beettersize2000). In the volume-based particle size distribution, the particle size at which the volume accumulation reaches 50% from the small particle size side is called the median particle size (D50), which is used as the volume average particle size of the solid electrolyte.

[0110] Determination of Li element content: The separator is dried and placed in a conical flask, and hydrochloric acid is added for sample dissolution. After the sample is completely dissolved, it is made up to a certain volume; after centrifugation, the supernatant is taken, and then the supernatant is added with HNO3 solution and hydrochloric acid and made up to a certain volume to obtain the test solution. The content of Li element is measured using a Plasma3000 ICP spectrometer. The analysis spectral lines of Li can be selected as 670.784 nm, 610.365 nm, and 323.263 nm. Considering the precision and accuracy comprehensively, 670.784 nm is preferably selected as the analysis spectral line. By analyzing and measuring the content of Li element, the amount of lithium salt in the polymer porous layer is determined.

[0111] Adhesive force: At a specific temperature and pressure, the separator and the electrode are hot-pressed on a hot press to stick them together. The force required for peeling per unit width from the contact surface is called the adhesive force, and its unit is N / m, which reflects the bonding strength of the material. A 4.1 cm x 6 cm separator is attached to an equal-sized electrode and placed in a hot press for hot pressing. After taking it out, a HY-0350 universal tensile testing machine is used to test the adhesive force between the separator and the electrode.

[0112] The test method of conductivity is as follows: At room temperature of 25 °C, for button batteries, the test is carried out at a frequency of 0 - 100000 Hz and a perturbation voltage of 5 mV, and the unit of ionic conductivity is σ / mS cm-1. A Metrohm Autolab PGSTAT302N electrochemical workstation is used to measure the ionic conductivity.

[0113] Battery cycle performance test: Through charge-discharge cycle tests, the changes in the charge-discharge capacity of lithium batteries with charge-discharge cycles can be directly observed. A Xindaneng S100-20-40 single-channel charge-discharge tester is used to measure the battery cycle performance.

[0114] Cyclic experiment test: Charge at a constant current of 0.3 A until the cut-off voltage of 3.65 V, then switch to constant voltage of 3.65 V and charge until 0.1 A, let it stand for 10 min, and then discharge at a constant current of 0.3 A until the cut-off voltage of 2.5 V. The cycle ends after 200 times.

[0115]

[0116]

[0117] In addition, the used solid electrolyte film without the polymer porous layer coating and the solid electrolyte layer remaining after removing the polymer porous layer from the separator solution swollen in Example 1 for 48 h were observed by scanning electron microscopy. Take a small piece of the separator and place it on the conductive adhesive, then insert the sample into the sample stage and insert it into the electron microscope, and use the JEOL JSM-6701F of Japan Electronics for testing. The test results are as Figure 1-2 shown. By injecting part of the electrolyte, due to its good flexibility, the polymer porous layer with high viscosity forms a viscoelastic gel state, which has excellent compatibility with both the solid electrolyte membrane and the electrode sheet. It can bond or fill the crack areas generated on the surface of the solid electrolyte film or the electrode sheet during long-term operation, realizing effective repair and ensuring that the battery has a high capacity retention rate. At the same time, the polymer porous layer itself contains lithium salt components, which can improve the ionic conductivity of the battery during the battery cycle.

[0118] Although the above describes the illustrative specific embodiments of the present application for the convenience of those skilled in the art to understand the present application, the present application is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present application defined and determined by the appended claims, all application creations using the concept of the present application are within the scope of protection.

Claims

1. A solid-state battery separator, characterized in that: include: A solid electrolyte film, wherein the solid electrolyte film is formed by tape casting an oxide ceramic slurry and sintering it at a high temperature; The polymer porous layer is arranged on both side surfaces of the solid electrolyte film, and the polymer porous layer is formed by coating and plasticizing a composite slurry of a high swelling resin and a lithium salt.

2. A solid-state battery separator according to claim 1, characterized in that: The average thickness A of the solid electrolyte film satisfies 20 μm≤A≤80 μm.

3. A solid-state battery separator according to claim 1, characterized in that: The average thickness a of the polymer porous layer satisfies 12 μm≤a≤21 μm.

4. A solid-state battery separator according to claim 1, characterized in that: The solid electrolyte film includes solid electrolyte particles, and the average particle size D of the solid electrolyte particles satisfies 0.01 μm≤D≤5 μm.

5. A solid-state battery separator according to claim 1, characterized in that: The average pore size d of the solid-state battery separator satisfies 0.1 μm≤d≤2 μm.

6. A solid-state battery separator according to claim 1, characterized in that: The high swelling resin includes one or more of polyvinylidene fluoride, polymethyl methacrylate, aramid, furan polyamide, polyimide, and polyacrylonitrile.

7. A solid-state battery separator according to claim 1, characterized in that: The mass proportion of the high swelling resin in the polymer porous layer is 50wt% to 90wt%.

8. A solid-state battery separator according to claim 1, characterized in that: The lithium salt includes one or more of LiPF6, LiClO4, LiBF4, LiAsF6, LiFSI, LiTFSI, and LiCl.

9. A solid-state battery separator according to claim 1, characterized in that: The porosity of the polymer porous layer is 30% to 70%.

10. A method for preparing a solid-state battery separator as claimed in claim 1, characterized in that: The following steps are involved: The mixed solution containing solid electrolyte particles and adhesive is cast on a polyester film substrate by a doctor blade, and after the solvent evaporates, the green film is peeled off, and after sintering at 1260° C., a dense and high-strength solid electrolyte film is obtained; A mixed coating liquid containing a high swelling resin and a lithium salt is coated on both sides of the solid electrolyte film, and the coating is plasticized at high temperature to form a polymer porous layer.

11. The method for preparing a solid-state battery separator according to claim 10, characterized in that: The coating method of the coating liquid required for the polymer porous layer is preferably micro-gravure coating, and the coating liquid is coated on both sides of the solid electrolyte film at the same time.

12. Use of the solid-state battery separator according to any one of claims 1 to 9 or the solid-state battery separator prepared by the preparation method of the solid-state battery separator according to any one of claims 10 to 11 in a secondary battery.

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