Composite solid electrolyte membrane and preparation method and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a composite solid electrolyte membrane as well as a preparation method and application thereof. The composite solid electrolyte membrane comprises a first electrolyte layer, a second electrolyte layer and a third electrolyte layer, the first electrolyte layer is arranged on the surface of one side of the second electrolyte layer, and the third electrolyte layer is arranged on the surface of the other side of the second electrolyte layer; the first electrolyte layer comprises a first lithium salt and a first organic high-molecular polymer, the second electrolyte layer comprises an inorganic electrolyte and an organic filling support, the organic filling support comprises a three-dimensional porous organic membrane and / or organic fiber filling filaments, and the third electrolyte layer comprises a second lithium salt and a second organic high-molecular polymer. Through coordination and cooperation of all the layers, the composite solid electrolyte membrane can be endowed with appropriate flexibility, high ionic conductivity and high interface bonding strength, and the comprehensive electrochemical performance is excellent.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a composite solid electrolyte membrane and a preparation method and application thereof. BACKGROUND

[0002] Solid-state batteries have better safety potential and higher energy density than traditional liquid batteries, and are advantageous alternatives for next-generation high-energy-density safe batteries. However, since solid-state batteries do not have electrolyte, and the whole battery cell is high in brittleness after high-pressure compression molding, the expansion and contraction of the positive and negative electrode materials during charging and discharging can easily cause the generation of gaps and cracks between the positive and negative electrode and the electrolyte interface, thereby reducing the interface contact area, increasing the charging and discharging polarization of the battery cell, and accelerating the cycle decay.

[0003] The defects of the existing organic-inorganic composite composite electrolyte membrane include: the addition of organic high molecules can split the mutual contact between the inorganic solid electrolyte particles, greatly reducing the conductivity thereof; and the high safety of the solid-state battery is not good.

[0004] Therefore, the present application is proposed. SUMMARY

[0005] An object of the present application is to provide a composite solid electrolyte membrane which has appropriate flexibility, high ion conductivity and high interface bonding strength, and excellent comprehensive electrochemical performance.

[0006] Another object of the present application is to provide a preparation method of the composite solid electrolyte membrane.

[0007] Another object of the present application is to provide a battery.

[0008] Another object of the present application is to provide an electric device.

[0009] In order to achieve the above objects of the present application, the following technical solutions are adopted: A composite solid electrolyte membrane comprises a first electrolyte layer, a second electrolyte layer and a third electrolyte layer, one side surface of the second electrolyte layer is provided with the first electrolyte layer, and the other side surface is provided with the third electrolyte layer; the first electrolyte layer comprises a first lithium salt and a first organic high molecular polymer, the mass content of the first lithium salt in the first electrolyte layer is 10% to 60%; the second electrolyte layer comprises an inorganic electrolyte and an organic filling support, the organic filling support comprises a three-dimensional porous organic membrane and / or an organic fiber filling wire, the mass content of the inorganic electrolyte in the second electrolyte layer is 85% to 98%; the third electrolyte layer comprises a second lithium salt and a second organic high molecular polymer, the mass content of the second lithium salt in the third electrolyte layer is 10% to 60%.

[0010] In some embodiments, the first lithium salt comprises at least one of lithium hexafluorophosphate, lithium bisfluorosulfonimide, lithium bis-trifluoromethylsulfonimide, lithium difluoro(oxalato)borate, and lithium tetrafluoroborate.

[0011] In some embodiments, the first organic high molecular polymer comprises at least one of polyacrylonitrile, polycarbonate, polyurethane, and polyvinylidene fluoride.

[0012] In some embodiments, the second lithium salt comprises at least one of lithium hexafluorophosphate, lithium bisfluorosulfonimide, lithium bis-trifluoromethylsulfonimide, lithium difluoro(oxalato)borate, and lithium tetrafluoroborate.

[0013] In some embodiments, the second organic high molecular polymer comprises at least one of polyacrylonitrile, polycarbonate, polyurethane, and polyvinylidene fluoride.

[0014] In some embodiments, the inorganic electrolyte comprises at least one of a sulfide electrolyte, a halide electrolyte, and an oxide electrolyte.

[0015] In some embodiments, the sulfide electrolyte comprises Li 10 GeP2S 12 , Li6PS5Cl, Li7P3S 11 , Li2S-P2S5, and at least one of Li2S-P2S5.

[0016] In some embodiments, the halide electrolyte comprises at least one of Li3YCl6, Li3YBr6, Li2TiCl4, Li3InBr6, and Li3InCl6.

[0017] In some embodiments, the oxide electrolyte comprises Li7La3Zr2O 12 , Li 1.3 Al 0.3 Ti 1.7 (PO4)3, and Li 3x La (2 / 3)-x TiO3.

[0018] In some embodiments, the material of the organic filling support comprises at least one of polyacrylonitrile, polycarbonate, polyurethane, polyvinylidene fluoride, polyfluoro rubber, epoxy alkane rubber, polyethylene, polypropylene, and polyphenyl alkene.

[0019] In some embodiments, the thickness of the first electrolyte layer is 0.1-20 μm.

[0020] In some embodiments, the thickness of the second electrolyte layer is 10-100 μm.

[0021] In some embodiments, the third electrolyte layer has a thickness of 0.1-20 μm.

[0022] In some embodiments, the second electrolyte layer has a porosity of less than 5%.

[0023] In some embodiments, the composite solid-state electrolyte film has an electrical conductivity of 1.2-2.8 mS / cm.

[0024] In some embodiments, the composite solid-state electrolyte film has a tensile strength of 7.8-10.5 N / 32 mm.

[0025] A method for preparing a composite solid-state electrolyte film as described above, comprising the following steps: A first electrolyte layer is prepared by a first coating method or a first casting method using a first mixed system containing a first lithium salt and a first organic high-molecular polymer; an inorganic electrolyte is compounded with an organic filler support by a wet coating method or a dry film forming method, and then subjected to densification treatment to obtain a second electrolyte layer; a second electrolyte layer is prepared by a second coating method or a second casting method using a second mixed system containing a second lithium salt and a second organic high-molecular polymer. The first electrolyte layer, the second electrolyte layer and the third electrolyte layer are sequentially laminated and then subjected to compression treatment to obtain a composite solid-state electrolyte film.

[0026] In some embodiments, the first coating method specifically comprises: mixing a first lithium salt, a first organic high-molecular polymer and a first solvent to obtain a first slurry, coating the first slurry onto the surface of a release film, and obtaining a first electrolyte layer after first drying and peeling; the solid content of the first slurry is 40%-55%.

[0027] In some embodiments, the first casting method comprises: subjecting a first lithium salt and a first organic high-molecular polymer to hot melt treatment, and then casting a film; In some embodiments, the second coating method specifically comprises: mixing a second lithium salt, a second organic high-molecular polymer and a second solvent to obtain a second slurry, coating the second slurry onto the surface of a release film, and obtaining a third electrolyte layer after second drying and peeling; the solid content of the second slurry is 40%-55%.

[0028] In some embodiments, the second casting method comprises: subjecting a second lithium salt and a second organic high-molecular polymer to hot melt treatment, and then casting a film.

[0029] In some embodiments, the wet coating method specifically comprises: mixing an inorganic electrolyte with an organic solvent to obtain a mixed slurry, coating the mixed slurry onto the surface of a three-dimensional porous organic film, and obtaining a second electrolyte layer after drying; the solid content of the mixed slurry is 40%-55%.

[0030] In some embodiments, the dry film forming method specifically comprises: hot-pressing treatment of the inorganic electrolyte, the organic fiber filling yarn and the mixture; the temperature of the hot-pressing treatment is 70-85℃, the pressure of the hot-pressing treatment is 0.7-1.2T, and the linear speed is 0.8-1.5m / s.

[0031] In some embodiments, the pressure of the densification treatment is 200-350MPa, and the pressure holding time is 5-15min.

[0032] In some embodiments, the pressure holding temperature of the densification treatment is 60-90℃.

[0033] In some embodiments, the pressure of the pressing treatment is 400-600MPa, and the time of the pressing treatment is 5-15min.

[0034] A battery comprising the composite solid electrolyte film or the composite solid electrolyte film obtained by the method.

[0035] A power consuming device comprising the battery.

[0036] Compared with the prior art, the present application has the following advantages: (1) In the composite solid electrolyte film of the present application, the first electrolyte layer and the third electrolyte layer are mainly inorganic and are respectively arranged on the two sides of the second electrolyte layer, which can not only increase the flexibility of the composite electrolyte film, but also avoid the problem of a large decrease in electrical conductivity caused by the contact and fragmentation of too many organic components to inorganic electrolyte particles. Some inorganic electrolyte particles are prone to side reactions with organic solvents or lithium salts, which can cause a large decrease in overall ionic conductivity. The present application separates the organic layer and the inorganic electrolyte layer, which can greatly reduce the contact area between the organic solvent, lithium salt and inorganic electrolyte particles, thereby reducing the reaction between them and improving the ionic conductivity. The use of a composite layer mainly composed of inorganic electrolyte particles in the middle layer and the use of organic layers with different oxidation and reduction resistance on both sides can reduce the interface side reaction between the positive and negative layers and the electrolyte layer, thereby improving the battery performance. Each layer has a suitable proportion to ensure the performance of each layer. Through the coordination of each layer, the composite solid electrolyte film can have suitable flexibility, high ionic conductivity and high interface bonding strength, and its comprehensive electrochemical performance is excellent.

[0037] (2) The preparation method of the composite solid electrolyte film of the present application can ensure the physicochemical properties of the first electrolyte layer, the second electrolyte layer and the third electrolyte layer through the coordination of the above steps. Through the lamination of the three layers, the interface bonding strength, conductivity and flexibility of the composite solid electrolyte film can be ensured, and the electrochemical performance of the battery can be improved.

[0038] (3) The battery of the present application has high conductivity, excellent cycle performance, rate performance and safety performance. DETAILED DESCRIPTION

[0039] The embodiments of the present application will be described in detail below with reference to Examples, but those skilled in the art will appreciate that the following Examples are for illustrative purposes only and should not be construed as limiting the scope of the present application. The specific conditions not mentioned in the Examples were carried out under the conventional conditions or the conditions recommended by the manufacturers. The reagents or instruments used were not specified by the manufacturers, and were all conventional products that can be commercially available.

[0040] According to one aspect of the present application, the present application relates to a composite solid-state electrolyte film, comprising a first electrolyte layer, a second electrolyte layer and a third electrolyte layer, one side surface of the second electrolyte layer is provided with the first electrolyte layer, and the other side surface is provided with the third electrolyte layer; the first electrolyte layer comprises a first lithium salt and a first organic high polymer, the mass content of the first lithium salt in the first electrolyte layer is 10% to 60% (for example, 10%, 15%, 20%, 30%, 40%, 50%, 60%, etc.); the second electrolyte layer comprises an inorganic electrolyte and an organic filling support, the organic filling support comprises a three-dimensional porous organic film and / or an organic fiber filling wire, the mass content of the inorganic electrolyte in the second electrolyte layer is 85% to 98% (for example, 85%, 88%, 90%, 92%, 95%, 96%, 98%, etc.); the third electrolyte layer comprises a second lithium salt and a second organic high polymer, the mass content of the second lithium salt in the third electrolyte layer is 10% to 60% (for example, 10%, 15%, 20%, 30%, 40%, 50%, 60%, etc.).

[0041] In the composite solid-state electrolyte film of the present application, the first electrolyte layer and the third electrolyte layer are mainly inorganic respectively, and are separated on both sides of the second electrolyte layer, which can not only increase the flexibility of the composite electrolyte film, but also avoid the problem of large decrease in conductivity caused by excessive organic components cutting the contact of inorganic electrolyte particles. Some inorganic electrolyte particles are prone to side reactions with organic solvents or lithium salts, which can cause a large decrease in overall ionic conductivity. The present application separates the organic layer and the inorganic electrolyte layer, which can greatly reduce the contact area between the organic solvent, lithium salt and inorganic electrolyte particles, thereby reducing the reaction between them and improving the ionic conductivity. The use of a composite layer mainly composed of inorganic electrolyte particles as the middle layer and the use of organic layers with different oxidation and reduction resistance on both sides can reduce the interface side reaction between the positive and negative layers and the electrolyte layer, thereby improving the battery performance. Each layer has a suitable proportion to ensure the performance of each layer. Through the coordination of each layer, the composite solid-state electrolyte film can be given appropriate flexibility, high ionic conductivity and high interface bonding strength, and its comprehensive electrochemical performance is excellent.

[0042] Because the positive electrode side interface has strong oxidizing property and the negative electrode side interface has strong reducing property, if the electrolyte layer can be kept stable at the interfaces of the positive and negative electrodes, the electrolyte needs to have a very wide electrochemical oxidation-reduction window (e.g. 5~0V Vs Li / Li + ), but in fact the electrochemical reduction window of the commonly used solid electrolyte is far below this range, resulting in strong side reactions at the interfaces of the positive and negative electrodes and thus causing large resistance. The present application uses an inorganic electrolyte layer with strong ionic conductivity in the middle layer, and uses different thin organic layers on both sides, and selects organic components that can ensure stable interface and less side reactions according to the oxidation-reduction characteristics of the positive and negative electrodes, thereby avoiding the problem of large side reactions of the uniformly mixed organic-inorganic electrolyte film.

[0043] In some embodiments, the first lithium salt includes at least one of lithium hexafluorophosphate (LiPF6), lithium bisfluorosulfonylimide (LiN(SO2F)2), lithium bis-trifluoromethylsulfonylimide (LiN(SO2CF3)2), lithium difluoro(oxalato)borate (LiBF2(C2O4)), and lithium tetrafluoroborate (LiBF4), such as a combination of lithium hexafluorophosphate and lithium bisfluorosulfonylimide, a combination of lithium bis-trifluoromethylsulfonylimide and lithium bis-trifluoromethylsulfonylimide, etc. The above first lithium salt is beneficial to improve ionic conductivity.

[0044] In some embodiments, the first organic high molecular polymer includes at least one of polyacrylonitrile, polycarbonate, polyurethane, and polyvinylidene fluoride, such as a combination of polyacrylonitrile and polycarbonate, a combination of polyurethane and polyvinylidene fluoride, etc. The first organic high molecular polymer has strong oxidation resistance, and this layer of electrolyte is in contact with the positive electrode layer. The high flexibility of the organic high molecular polymer can be used to tightly bond the positive electrode layer together during the process of being assembled into a battery cell by high-pressure pressing, thereby reducing the risk of contact separation between the positive electrode and the electrolyte film interface during the charge and discharge cycle of the battery cell.

[0045] In some embodiments, the second lithium salt includes at least one of lithium hexafluorophosphate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethylsulfonylimide, lithium difluoro(oxalato)borate, and lithium tetrafluoroborate, such as a combination of lithium hexafluorophosphate and lithium bisfluorosulfonylimide, a combination of lithium tetrafluoroborate and lithium bis-trifluoromethylsulfonylimide, etc. The above second lithium salt is beneficial to improve ionic conductivity.

[0046] In some embodiments, the second organic polymer includes at least one of polyacrylonitrile, polycarbonate, polyurethane, and polyvinylidene fluoride, such as a combination of polyacrylonitrile and polycarbonate, a combination of polyurethane and polyvinylidene fluoride, and the like. The second polymer is made of a strong anti-reducing material, and the electrolyte layer in contact with the negative electrode layer uses the high flexibility of the organic polymer to be tightly bonded with the negative electrode layer during the assembly into the battery cell and the high-pressure pressing process, thereby reducing the risk of contact separation between the negative electrode and the electrolyte membrane interface during the charge and discharge cycle of the battery cell.

[0047] In some embodiments, the inorganic electrolyte includes at least one of a sulfide electrolyte, a halide electrolyte, and an oxide electrolyte; the sulfide electrolyte includes Li 10 GeP2S 12 , Li6PS5Cl, Li7P3S 11 , Li2S-P2S5, and at least one of Li2S-P2S5; the halide electrolyte includes at least one of Li3YCl6, Li3YBr6, Li2TiCl4, Li3InBr6, and Li3InCl6; and the oxide electrolyte includes at least one of Li7La3Zr2O 12 , Li 1.3 Al 0.3 Ti 1.7 (PO4)3, and Li 3x La (2 / 3)-x TiO3. The above suitable inorganic electrolyte and its proportion can ensure that the electrical conductivity of the composite electrolyte membrane can be maintained at a high level, which is beneficial to improve the electrical conductivity of the battery.

[0048] In some embodiments, the material of the organic filling support includes at least one of polyacrylonitrile, polycarbonate, polyurethane, polyvinylidene fluoride, polyfluororubber, epoxy alkane rubber, polyethylene, polypropylene, and polyphenyl alkene. In some embodiments, the three-dimensional porous organic membrane includes an electrospun porous membrane and a non-woven fabric membrane. In some embodiments, the organic fiber filling yarn includes at least one of polyester fiber, polyamide fiber, aramid fiber, polyacrylonitrile fiber, and polypropylene fiber.

[0049] In some embodiments, the thickness of the first electrolyte layer is 0.1-20 μm, such as 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 10 μm, 15 μm, 20 μm, etc. In some embodiments, the thickness of the second electrolyte layer is 10-100 μm, such as 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 50 μm, 100 μm, 150 μm, 200 μm, etc. In some embodiments, the thickness of the third electrolyte layer is 0.1-20 μm, such as 0.1 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 10 μm, 15 μm, 20 μm, etc. By using the first electrolyte layer, the second electrolyte layer and the third electrolyte layer with appropriate thicknesses, the ion conductivity and mechanical properties of the composite solid electrolyte film can be balanced, and the cycle stability of the battery can be improved.

[0050] In some embodiments, the porosity of the second electrolyte layer is less than 5%, such as 1%, 2%, 3%, 4% and 5%, etc. By setting the porosity of the second electrolyte layer, the composite solid electrolyte film has appropriate compactness, and the overall electrochemical performance of the composite solid electrolyte film is ensured.

[0051] In some embodiments, the electrical conductivity of the composite solid electrolyte film is 1.2-2.8 mS / cm, such as 1.2 mS / cm, 1.5 mS / cm, 1.8 mS / cm, 2 mS / cm, 2.5 mS / cm, 2.8 mS / cm, etc. The composite solid electrolyte film of the present application has excellent electrical conductivity.

[0052] In some embodiments, the tensile strength of the composite solid electrolyte film is 7.8-10.5 N / 32 mm, such as 7.8 N / 32 mm, 8 N / 32 mm, 9 N / 32 mm, 10 N / 32 mm, 10.5 N / 32 mm, etc. The composite solid electrolyte film of the present application has appropriate tensile strength.

[0053] The composite solid electrolyte film of the present application can increase the flexibility of the inorganic electrolyte film, prevent the electrolyte layer from cracking during charging and discharging, reduce the weakening of the ion conductivity of the inorganic electrolyte caused by the organic component, and maintain a high ion conductivity of the composite electrolyte film. Through the structural design of the composite film, the interface bonding strength between the electrolyte film and the positive electrode layer and the negative electrode layer can be enhanced, and the risk of contact separation between the electrolyte film and the positive electrode layer and the negative electrode layer during charging and discharging can be reduced.

[0054] According to another aspect of the present application, the present application also relates to a method for preparing the composite solid electrolyte film as described above, comprising the following steps: The first electrolyte layer is prepared by a first coating method or a first casting method using a first mixed system containing a first lithium salt and a first organic high molecular polymer; the second electrolyte layer is prepared by a second coating method or a second casting method using a second mixed system containing a second lithium salt and a second organic high molecular polymer; and the third electrolyte layer is prepared by a third coating method or a third casting method using a third mixed system containing a third lithium salt and a third organic high molecular polymer.

[0055] The preparation method of the composite solid-state electrolyte film can ensure the physicochemical properties of the first electrolyte layer, the second electrolyte layer and the third electrolyte layer, and can ensure the interface bonding strength, the electrical conductivity and the flexibility of the composite solid-state electrolyte film through the layer-by-layer compounding of the three layers, thereby improving the electrochemical performance of the battery.

[0056] In some embodiments, the first coating method specifically includes: mixing the first lithium salt, the first organic high molecular polymer and the first solvent to obtain a first slurry, coating the first slurry to the surface of a release film, and obtaining the first electrolyte layer after first drying and peeling; the solid content of the first slurry is 40% to 55%, for example, 40%, 45%, 50% or 55%, etc., and the viscosity of the first slurry is controlled to be 5 to 100 Pa.s, for example, 5 Pa.s, 10 Pa.s, 20 Pa.s, 50 Pa.s, 70 Pa.s or 100 Pa.s, etc. The suitable solid content of the first slurry is conducive to improving the coating effect and improving the performance of the electrolyte layer. The solvent is removed by first drying to form a dry film, the temperature of the first drying is 50 to 150°C (for example, 50°C, 70°C, 100°C, 150°C, etc.), the drying time is determined according to the residual solvent content (residual solvent content < 5%), and the organic electrolyte film is peeled off from the release film after the dry film is formed.

[0057] In some embodiments, the first casting method includes: performing hot melt treatment on the first lithium salt and the first organic high molecular polymer, and then performing film casting by a casting device. In some embodiments, the second coating method specifically includes mixing the second lithium salt, the second organic high molecular polymer and the second solvent to obtain a second slurry, coating the second slurry to the surface of the release film, and obtaining a third electrolyte layer after second drying and peeling; the solid content of the second slurry is 40% to 55%, for example, 40%, 45%, 50% or 55%, etc., and the viscosity of the second slurry is controlled to be 5 to 100 Pa.s, for example, 5 Pa.s, 10 Pa.s, 20 Pa.s, 50 Pa.s, 70 Pa.s or 100 Pa.s, etc. The suitable solid content of the first slurry is conducive to improving the coating effect and improving the performance of the electrolyte layer. The solvent is removed by second drying to form a dry film, the temperature of the second drying is 50 to 150°C (for example, 50°C, 70°C, 100°C, 150°C, etc.), the drying time is determined according to the residual solvent content, the residual solvent content is <5%, and the organic electrolyte film is peeled off from the release film after the dry film is formed.

[0058] In some embodiments, the second casting method includes: subjecting the second lithium salt and the second organic high molecular polymer to hot melt treatment, and then performing film casting by a casting device.

[0059] In some embodiments, the wet coating method specifically includes: mixing the inorganic electrolyte with an organic solvent to obtain a mixed slurry, coating the mixed slurry to the surface of the three-dimensional porous organic film, and obtaining a second electrolyte layer after drying; the solid content of the mixed slurry is 40% to 55%, for example, 40%, 45%, 50% or 55%, etc.; the viscosity of the mixed slurry is 4000 to 20000 mPa.s, for example, 4000 mPa.s, 5000 mPa.s, 10000 mPa.s, 20000 mPa.s, etc. The suitable solid content and viscosity of the mixed slurry are conducive to ensuring the coating effect and improving the film forming quality of the second electrolyte layer. The solvent is removed by drying to form a dry film, the heating temperature can be determined according to the solvent, for example, 50 to 150°C (for example, 50°C, 60°C, 70°C, 80°C or 150°C, etc.), the drying time is determined according to the residual solvent content, and the residual solvent content is recommended to be <50 ppm. After the dry film is formed, further high compaction is performed to form a dense film.

[0060] In some embodiments, the dry film forming method specifically comprises: heat pressing the inorganic electrolyte, the organic fiber filling yarn and the mixture; the heat pressing temperature is 70-85℃ (for example, 70℃, 75℃, 80℃, 85℃, etc.), the heat pressing pressure is 0.7-1.2T (for example, 0.7T, 1T, 1.1T, 1.2T, etc.), and the linear velocity is 0.8-1.5m / s (for example, 0.8m / s, 0.9m / s, 1m / s, 1.5m / s, etc.). The present application adopts a suitable dry film forming method to ensure the performance of the second electrolyte layer. In some embodiments, a film forming binder can be appropriately added, including polytetrafluoroethylene fiber. After the components are uniformly mixed by a high-speed mixing device, the powder is rolled or molded by a mold. The molding pressure is adjusted according to the density of the film, and the target porosity of the film after molding is below 5%.

[0061] In some embodiments, the pressure of the densification treatment is 200-350MPa, for example, 200MPa, 250MPa, 300MPa, 320MPa, 350MPa, etc. The pressure holding time is 5-15min, for example, 5min, 10min, 15min, etc. The compaction process can be carried out by rolling, mold molding, etc. The compaction pressure is adjusted according to the density of the film. Through the above-mentioned suitable densification treatment, the target porosity of the film after compaction is below 5%. In some embodiments, the pressure holding temperature of the densification treatment is 60-90℃, for example, 60℃, 70℃, 80℃, 90℃, etc. Through a suitable pressure holding temperature, the performance of the electrolyte layer is improved.

[0062] In some embodiments, the pressure of the pressing treatment is 400-600MPa, for example, 400MPa, 420MPa, 450MPa, 500MPa, 550MPa or 600MPa. The time of the pressing treatment is 5-15min, for example, 5min, 8min, 10min, 12min or 15min, etc. A suitable pressing treatment is adopted to ensure the interface bonding performance between the layers and the comprehensive performance of the composite film layer.

[0063] According to another aspect of the present application, the present application also relates to a battery comprising the composite solid electrolyte film or the composite solid electrolyte film obtained by the method.

[0064] The battery of the present application has high conductivity, excellent cycle performance, rate performance and safety performance.

[0065] According to another aspect of the present application, the present application also relates to an electric device comprising the battery. The electric device of the present application includes an electric vehicle, an electric tool, etc.

[0066] The following is further explained in conjunction with specific examples, comparative examples.

[0067] Example 1 A method for preparing a composite solid-state electrolyte film, comprising the following steps: (1) Dissolve lithium bisfluorosulfonylimide (first lithium salt) and polyacrylonitrile (first organic high molecular polymer) in dimethyl sulfoxide solvent, the mass ratio of lithium bisfluorosulfonylimide: polyacrylonitrile is 1:2, adjust the solvent content to make the solid content 50%, use the method of blade coating to coat the solution on the release film, put it into the oven to dry for 24h to remove the solvent, and then peel off the first electrolyte layer from the release film, the thickness is 4μm.

[0068] (2) Add Li6PS5Cl solid-state electrolyte powder into dimethylbenzene solvent, control the solid content at 40%, use homogenizer to stir and homogenize for 10h to form uniform slurry, coat the slurry on non-woven fabric (organic filling support, polypropylene), the porosity of non-woven fabric is 90%, the thickness is 30μm. After the slurry fully penetrates into the voids of non-woven fabric, remove the solvent by vacuum heating, form a dry film, the heating temperature is 90℃, the holding time is 10h, use isostatic pressing machine to press the dry film into a dense film, the pressure is set at 300MPa, the pressure holding time is 10min, obtain the second electrolyte layer, the porosity of the second electrolyte layer is 3%. The mass ratio of solid-state electrolyte powder and organic filling support polypropylene is 90:5.

[0069] (3) Dissolve lithium bis(trifluoromethanesulfonyl)imide (second lithium salt) and polyethylene oxide (second organic high molecular polymer) in acetonitrile, the mass ratio of lithium bis(trifluoromethanesulfonyl)imide: polyethylene oxide is 1:2, adjust the solvent content to make the solid content 50%, use the method of blade coating to coat the solution on the release film, put it into the oven to dry for 24h to remove the solvent, and then peel off the third electrolyte layer from the release film, the thickness is 4μm.

[0070] (4) Stack the first electrolyte layer, the second electrolyte layer and the third electrolyte layer in turn, and then perform isostatic pressing treatment, the pressure is set at 500MPa, the pressure holding time is 10min, obtain the composite solid-state electrolyte film. The mass ratio of the first electrolyte layer, the second electrolyte layer and the third electrolyte layer is 5:90:5.

[0071] Example 2 A method for preparing a composite solid-state electrolyte film, comprising the following steps: (1) Lithium bis-trifluoromethanesulfonimide (first lithium salt), polytetrafluoroethylene (first organic high molecular polymer) are dissolved in N-methyl pyrrolidone, the mass ratio of lithium bis-trifluoromethanesulfonimide: polytetrafluoroethylene is 1:2, the solvent content is adjusted to make the solid content 30%, the solution is coated on the release film by scraping, dried in an oven for 24 hours to remove the solvent, and the first electrolyte layer is obtained by peeling off from the release film, with a thickness of 5 μm.

[0072] (2) Li6PS5Cl solid-state electrolyte powder, polypropylene fiber (organic filling support), and polytetrafluoroethylene powder are mixed together, with a mass ratio of 90%, 9%, and 1% respectively. The above materials are uniformly mixed using a high-speed mixer, and are rolled into a film using a multi-roll film forming device. The rolling parameters are adjusted according to the film forming characteristics and equipment parameters. In this example, the rolling pressure is 1T, the rolling temperature is 80°C, and the linear speed is 1m / s. After rolling, the film is further densified by isostatic pressing, with a pressure of 300Ma, a holding time of 10min, and a holding temperature of 85°C. The porosity of the second electrolyte layer is 3.5%.

[0073] (3) Lithium bis-trifluoromethanesulfonimide (second lithium salt) and polyethylene oxide powder (second organic high molecular polymer) are mixed, with a mass ratio of lithium bis-trifluoromethanesulfonimide: polyethylene oxide of 1:2. The film is formed by casting using a casting device, with a thickness of 5 μm.

[0074] (4) The first electrolyte layer, the second electrolyte layer, and the third electrolyte layer are stacked in turn, and then isostatic pressing is performed, with a pressure of 500MPa and a holding time of 10min, to obtain a composite solid-state electrolyte film.

[0075] Example 3 A method for preparing a composite solid-state electrolyte film, which is different from Example 1 in that: The first lithium salt is lithium bis-fluorosulfonimide and lithium hexafluorophosphate, with a mass ratio of 1:2.

[0076] The first organic high molecular polymer is polyacrylonitrile and polycarbonate, with a mass ratio of 3:1.

[0077] The second lithium salt is lithium bis-fluorosulfonimide and lithium hexafluorophosphate, with a mass ratio of 1:2.

[0078] The second organic high molecular polymer is polyethylene oxide and polycarbonate, with a mass ratio of 3:1.

[0079] The solid-state electrolyte is Li6PS5Cl, Li3InCl6, and Li 1.3 Al 0.3 Ti 1.7(PO4)3, with a mass ratio of 3:1:1. The porosity of the second electrolyte layer is 2.5%.

[0080] Example 4 A method for preparing a composite solid electrolyte membrane differs from that in Example 1 in that: The thickness of the first electrolyte layer is 3 μm.

[0081] The organic filler support is an electrospun porous membrane with a porosity of 92% and is made of polyfluororubber. The second electrolyte layer has a porosity of 3.5%.

[0082] The thickness of the second electrolyte layer is 3 μm.

[0083] Example 5 The method for preparing a composite solid electrolyte membrane differs from that in Example 2 in that: The first lithium salt is lithium tetrafluoroborate and lithium hexafluorophosphate in a mass ratio of 1:3.

[0084] The first organic polymer is polyacrylonitrile and polyvinylidene fluoride in a mass ratio of 4:1.

[0085] The second lithium salt is lithium tetrafluoroborate and lithium hexafluorophosphate in a mass ratio of 1:3.

[0086] The second organic polymer is polyacrylonitrile and polyvinylidene fluoride in a mass ratio of 4:1.

[0087] The solid electrolytes are Li6PS5Cl, Li3InCl6 and Li 1.3 Al 0.3 Ti 1.7 (PO4)3, with a mass ratio of 3:1:1, and the porosity of the second electrolyte layer is 3%.

[0088] Example 6 A method for preparing a composite solid electrolyte membrane differs from that in Example 3 in that: The thickness of the first electrolyte layer is 3 μm.

[0089] The organic filler support consists of polyamide fibers and polypropylene fibers in a mass ratio of 2:1. The porosity of the second electrolyte layer is 2.8%.

[0090] The thickness of the second electrolyte layer is 3 μm.

[0091] Comparative Example 1 A method for preparing a composite solid electrolyte membrane differs from that in Example 1 in that: In step (1), the mass ratio of lithium bis(trifluoromethanesulfonylimide) to polyacrylonitrile is 1:12.

[0092] In step (3), the mass ratio of lithium bis(trifluoromethylsulfonyl)imide: poly(ethylene oxide) is 1:12.

[0093] Comparative Example 2 A method for preparing a composite solid electrolyte membrane, which differs from Comparative Example 1 in that: In step (2), the pressure is set to 180 MPa, and the porosity of the second electrolyte layer is 10%.

[0094] Experimental Example I. Performance test of the composite solid electrolyte membrane The composite solid electrolyte membranes of each example and comparative example were respectively subjected to performance tests, and the test method included: the conductivity test adopted an alternating current impedance test method, the electrolyte membrane was prepared into a membrane piece with a diameter of 10 mm, was loaded into a mold with a diameter of 11 mm, two steel cylindrical electrodes with a diameter of 10 mm were respectively pressed on the upper and lower sides of the membrane piece, a pressure of 100 MPa was applied, the electrodes were linked to an alternating current impedance instrument for testing, the equilibrium voltage was 0 V, the voltage excitation amplitude was 10 mV, and the frequency range was 10 kHz~1 Hz. An alternating current impedance plot was drawn to obtain the value of the conductivity. The calculation formula of the conductivity was: Conductivity = membrane piece resistance / membrane piece thickness.

[0095] The tensile strength test adopted a membrane tensile machine to obtain the tensile strength. The sample width was 32 mm.

[0096] The performance test results of the composite solid electrolyte membranes of each example and comparative example are shown in Table 1.

[0097] Table 1 Performance test results of the composite solid electrolyte membranes

[0098] The composite solid electrolyte membranes of each example of the present application have excellent conductivity and suitable tensile strength. The conductivity of the composite solid electrolyte membrane of Comparative Example 1 is poor. The conductivity and compression strength of the composite solid electrolyte membrane of Comparative Example 2 are both poor.

[0099] II. Battery performance test The batteries prepared from the composite solid electrolyte membranes of each example and comparative example were subjected to performance tests, and the battery test method included: The membrane piece was cut into a circular piece with a diameter of 10 mm, a graphite electrode was placed on one side of the membrane piece, a lithium metal piece was placed on the other side, was loaded into a mold with a diameter of 11 mm, and two steel cylindrical electrodes with a diameter of 10 mm were respectively pressed on the upper and lower sides of the membrane piece, and a pressure of 10 MPa was applied. The battery was subjected to a cyclic charge-discharge test, the voltage range was 1 V~0 V, and the charge-discharge current was 2 mA / cm 2 . Continuous cycling for 500 cycles.

[0100] The performance test results of the above batteries are shown in Table 2.

[0101] Table 2 Performance test results of the batteries

[0102] As shown in Table 2, the batteries prepared by the composite solid electrolyte films of the embodiments of the present application have excellent rate performance and capacity retention rate, the rate performance is above 80%, and the capacity retention rate is above 80%.

[0103] The rate performance and capacity retention rate of the batteries prepared by the composite solid electrolyte films of Comparative Examples 1-2 are both poor.

[0104] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A composite solid electrolyte membrane, characterized in that, It includes a first electrolyte layer, a second electrolyte layer and a third electrolyte layer, wherein the first electrolyte layer is disposed on one side surface of the second electrolyte layer and the third electrolyte layer is disposed on the other side surface; The first electrolyte layer comprises a first lithium salt and a first organic polymer, wherein the mass content of the first lithium salt in the first electrolyte layer is 10% to 60%. The second electrolyte layer includes an inorganic electrolyte and an organic filler support, wherein the organic filler support includes a three-dimensional porous organic membrane and / or organic fiber filler filaments, and the inorganic electrolyte has a mass content of 85% to 98% in the second electrolyte layer; The third electrolyte layer includes a second lithium salt and a second organic polymer, wherein the mass content of the second lithium salt in the third electrolyte layer is 10% to 60%.

2. The composite solid electrolyte membrane according to claim 1, characterized in that, It includes at least one of the following features (1) to (4): (1) The first lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, and lithium tetrafluoroborate; (2) The first organic polymer includes at least one of polyacrylonitrile, polycarbonate, polyurethane and polyvinylidene fluoride; (3) The second lithium salt includes at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalateborate, and lithium tetrafluoroborate; (4) The second organic polymer includes at least one of polyacrylonitrile, polycarbonate, polyurethane and polyvinylidene fluoride.

3. The composite solid electrolyte membrane according to claim 1, characterized in that, It includes at least one of the following features (1) to (2): (1) The inorganic electrolyte includes at least one of sulfide electrolyte, halide electrolyte and oxide electrolyte; The sulfide electrolyte includes Li 10 GeP2S 12 Li6PS5Cl, Li7P3S 11 At least one of Li2S-P2S5 and Li2S-P2S5; The halide electrolyte includes at least one of Li3YCl6, Li3YBr6, Li2TiCl4, Li3InBr6, and Li3InCl6; The oxide electrolyte includes Li7La3Zr2O 12 Li 1.3 Al 0.3 Ti 1.7 (PO4)3 and Li 3x La (2 / 3)-x At least one of TiO3; (2) The organic filler support is made of at least one of polyacrylonitrile, polycarbonate, polyurethane, polyvinylidene fluoride, fluororubber, epoxy alkane rubber, polyethylene, polypropylene and polyphenylene olefin.

4. The composite solid electrolyte membrane according to claim 1, characterized in that, It includes at least one of the following features (1) to (6): (1) The thickness of the first electrolyte layer is 0.1~20μm; (2) The thickness of the second electrolyte layer is 10~100μm; (3) The thickness of the third electrolyte layer is 0.1~20μm; (4) The porosity of the second electrolyte layer is less than 5%; (5) The conductivity of the composite solid electrolyte membrane is 1.2~2.8 mS / cm; (6) The tensile strength of the composite solid electrolyte membrane is 7.8~10.5 N / 32mm.

5. The method for preparing the composite solid electrolyte membrane according to any one of claims 1 to 4, characterized in that, Includes the following steps: The first electrolyte layer is prepared by a first mixed system containing a first lithium salt and a first organic polymer through a first coating method or a first casting method. Inorganic electrolytes are combined with organic filler supports by wet coating or dry film formation, and then densification is performed to obtain a second electrolyte layer. The second electrolyte layer is prepared by a second coating method or a second casting method using a second mixed system containing a second lithium salt and a second organic polymer. The first electrolyte layer, the second electrolyte layer, and the third electrolyte layer are stacked sequentially and then pressed together to obtain a composite solid electrolyte membrane.

6. The method for preparing the composite solid electrolyte membrane according to claim 5, characterized in that, It includes at least one of the following features (1) to (3): (1) The first coating method specifically includes: mixing a first lithium salt, a first organic polymer and a first solvent to obtain a first slurry, coating the first slurry onto the surface of a release film, and obtaining a first electrolyte layer after drying and peeling; the solid content of the first slurry is 40%~55%; (2) The first casting method includes: performing a hot melt treatment on the first lithium salt and the first organic polymer, and then casting them into a film; (3) The second coating method specifically includes: mixing a second lithium salt, a second organic polymer and a second solvent to obtain a second slurry, coating the second slurry onto the surface of a release film, and obtaining a third electrolyte layer after drying and peeling; the solid content of the second slurry is 40%~55%; (4) The second casting method includes: hot melting the second lithium salt and the second organic polymer, and then casting them into a film.

7. The method for preparing the composite solid electrolyte membrane according to claim 5, characterized in that, It includes at least one of the following features (1) to (4): (1) The wet coating method specifically includes: mixing an inorganic electrolyte with an organic solvent to obtain a mixed slurry, coating the mixed slurry onto the surface of a three-dimensional porous organic membrane, and drying it to obtain a second electrolyte layer; the solid content of the mixed slurry is 40%~55%; (2) The dry film-making method specifically includes: hot pressing inorganic electrolyte with organic fiber filler and mixture; the hot pressing temperature is 70~85℃, the hot pressing pressure is 0.7~1.2T, and the linear velocity is 0.8~1.5m / s; (3) The densification treatment pressure is 200~350MPa, and the holding time is 5~15min; (4) The holding temperature of the densification treatment is 60~90℃.

8. The method for preparing the composite solid electrolyte membrane according to claim 6, characterized in that, The pressure of the pressing process is 400~600MPa, and the pressing time is 5~15min.

9. A battery, characterized in that, The composite solid electrolyte membrane includes any one of claims 1 to 4, or the composite solid electrolyte membrane obtained by the method of any one of claims 5 to 8.

10. An electrical appliance, characterized in that, Includes the battery as described in claim 9.

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