Composite solid electrolyte membrane and preparation method thereof, secondary battery and electric device

Abstract

The invention provides a composite solid electrolyte membrane and a preparation method thereof, a secondary battery and an electric device. The preparation method comprises the following steps: forming a first mixed solution from a precursor solution of an oxide solid electrolyte and a pore forming agent, and forming a porous oxide solid electrolyte membrane by adopting a tape casting method; dissolving a lithium salt and a tackifier in an organic solvent to obtain an ionic liquid; and applying pressure to permeate the ionic liquid into the porous oxide solid electrolyte membrane to obtain the composite solid electrolyte membrane. The invention provides a method for efficiently and uniformly filling a porous oxide solid electrolyte membrane. The composite solid electrolyte membrane provided by the invention has relatively high ionic conductivity and interface contact, and rapid infiltration of the ionic liquid and efficient utilization of the porous oxide solid electrolyte membrane are realized. The invention also provides an application of the composite solid electrolyte membrane in a secondary battery, and the secondary battery has relatively high energy density and long cycle life.

Description

Technical Field

[0001] The present application relates to the field of battery material technology, and in particular to a composite solid electrolyte membrane and a preparation method thereof, a secondary battery, and an electrical device. Background Art

[0002] In the field of energy storage, solid electrolyte materials are considered to be key materials for the next generation of lithium-ion batteries. For oxide solid-state batteries, the dense solid electrolyte membrane sintered at high temperature is relatively brittle, and the sintering process causes defects in the solid electrolyte membrane, which affects the ion conductivity. In addition, the interface contact between the oxide solid electrolyte membrane and the electrode material is poor, which affects the performance of the battery.

[0003] In the related art, in order to improve the ionic conductivity of the solid electrolyte membrane and improve the poor contact between the solid electrolyte membrane and the electrode material interface, binders are usually added to the solid electrolyte membrane, such as polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), etc., and conductive materials such as metal oxides, carbon materials, etc. are added to the solid electrolyte membrane to form a composite electrolyte membrane. However, the addition of binders and conductive materials still cannot effectively solve the problem of low ionic conductivity of the solid electrolyte membrane itself. Summary of the invention

[0004] The present application aims to solve one of the technical problems in the related art at least to some extent.

[0005] On the one hand, the present application proposes a method for preparing a composite solid electrolyte membrane, which utilizes ionic liquid to efficiently and uniformly fill a porous oxide solid electrolyte membrane. The method is simple and easy to mass produce.

[0006] On the other hand, the present application proposes a composite solid electrolyte membrane, which has high ionic conductivity and interface contact with electrode materials, and can achieve rapid infiltration of ionic liquids and efficient utilization of porous oxide solid electrolyte membranes.

[0007] On the other hand, the present application proposes the use of the composite solid electrolyte membrane in any of the above-mentioned embodiments in secondary batteries and electrical devices, so as to improve the ionic conductivity and interface contact of the oxide solid electrolyte membrane, so that the secondary batteries and electrical devices have higher energy density and cycle life performance.

[0008] According to an embodiment of the first aspect of the present application, a method for preparing a composite solid electrolyte membrane is provided, comprising the following steps:

[0009] A first mixed solution formed by a precursor solution of an oxide solid electrolyte and a pore former is formed into a porous oxide solid electrolyte membrane by a tape casting method;

[0010] Dissolving a lithium salt in an organic solvent to obtain an ionic liquid with a concentration range of 0.8-10 mol / L, wherein the concentration of lithium ions is greater than 0.8 mol / L, and adding a thickener to the ionic liquid to make the viscosity of the ionic liquid range from 500 to 15000 mPa·S;

[0011] The ionic liquid is infiltrated into the porous oxide solid electrolyte membrane by applying pressure to obtain a composite solid electrolyte membrane.

[0012] In some embodiments, the oxide solid electrolyte includes lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphate, or lithium aluminum titanium phosphate;

[0013] and / or, the pore-forming agent comprises at least one of ammonium bicarbonate, polyethylene, urea, polypropylene, polystyrene or polymethyl acrylate;

[0014] And / or, based on the precursor solution, the mass percentage of the pore-forming agent is 20%-60%;

[0015] And / or, the porous oxide solid electrolyte membrane has a thickness of 20-80 μm.

[0016] In some embodiments, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorobisoxalatoborate, lithium difluorophosphate, and lithium bis(trifluoromethylsulfonyl imide);

[0017] and / or, the organic solvent comprises at least one of ether, toluene, tetrahydrofuran, fluorocarbonate, ethylene carbonate, dimethyl carbonate or ethyl methyl carbonate;

[0018] and / or, the tackifier includes at least one of polyimide hot melt adhesive, ethylene-vinyl acetate copolymer, styrene-isoprene glycol-styrene block copolymer, polyethylene wax or polyethylene oxide wax;

[0019] And / or, based on the ionic liquid, the mass percentage of the viscosity enhancer is 3%-50%.

[0020] In some embodiments, the ionic liquid is heated to a fluid state and pressure is applied to allow the ionic liquid to penetrate into the porous oxide solid electrolyte membrane.

[0021] In some embodiments, the ionic liquid and the porous oxide solid electrolyte membrane are placed in an osmotic pressure device; after the porous oxide solid electrolyte membrane is fully infiltrated, excess ionic liquid on the surface is removed, and then the temperature is restored to room temperature.

[0022] According to an embodiment of the second aspect of the present application, a composite solid electrolyte membrane is proposed, which is obtained by using the preparation method described in any of the above embodiments.

[0023] In some embodiments, the composite solid electrolyte membrane has a thickness of 5 μm-90 μm.

[0024] In some embodiments, the ionic conductivity of the composite solid electrolyte membrane is (1.09-4.25)×10 - 4 S cm -1 .

[0025] According to an embodiment of the third aspect of the present application, a secondary battery is provided, which includes the composite solid electrolyte membrane described in any of the above embodiments.

[0026] According to an embodiment of the fourth aspect of the present application, an energy storage device is provided, which includes the secondary battery described in any of the above embodiments.

[0027] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become apparent from the description below, or will be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the following description of the embodiments in conjunction with the accompanying drawings, in which:

[0029] Figure 1 It is a flow chart of a method for preparing a composite solid electrolyte membrane provided in one embodiment of the present application. DETAILED DESCRIPTION

[0030] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be construed as limiting the present application. On the contrary, the present application includes all changes, modifications and equivalents that fall within the spirit and connotation of the appended claims.

[0031] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0032] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0033] To achieve the above-mentioned purpose, according to the embodiment of the first aspect of the present application, a method for preparing a composite solid electrolyte membrane is proposed. Figure 1 , including the following steps:

[0034] S1: forming a porous oxide solid electrolyte membrane by using a tape casting method to form a first mixed solution formed by a precursor solution of an oxide solid electrolyte and a pore former;

[0035] S2: dissolving a lithium salt in an organic solvent to obtain an ionic liquid with a concentration range of 0.8-10 mol / L, wherein the concentration of lithium ions is greater than 0.8 mol / L, and then adding a thickener to the ionic liquid to make the viscosity of the ionic liquid range from 500 to 15000 mPa·S;

[0036] S3: The ionic liquid is infiltrated into the porous oxide solid electrolyte membrane by applying pressure to obtain a composite solid electrolyte membrane.

[0037] In S1, a precursor solution is formed according to an oxide solid electrolyte, wherein the oxide solid electrolyte includes lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphate or lithium aluminum titanium phosphate. For example, when the oxide solid electrolyte is lithium aluminum titanium phosphate, lithium nitrate, aluminum isopropoxide, phosphoric acid and tetraisopropyl titanate in a mass ratio of 1-1.5: 0.35-0.8: 1.2-1.8: 2.5-4.5 are dissolved and dispersed in a solvent such as isopropanol to form a precursor solution of lithium aluminum titanium phosphate.

[0038] A pore former is added to a precursor solution of an oxide solid electrolyte to form a first mixed solution; wherein the pore former includes at least one of ammonium bicarbonate, polyethylene, urea, polypropylene, polystyrene or polymethyl acrylate, and the pore former in the present application is an organic pore former: it will not remain in the porous oxide solid electrolyte membrane after high-temperature sintering. In this embodiment, the mass percentage of the pore former is 20%-60% based on the precursor solution; the mass percentage of the pore former in the example is 20%, 30%, 40%, 50%, 60%, etc.

[0039] The first mixed solution is used to form a porous oxide solid electrolyte membrane by a casting method, which includes adjusting the viscosity of the first mixed solution, pouring the first mixed solution on a substrate, using a scraper to prepare a film of a set thickness, slowly drying in an oven to remove the solvent, first pre-sintering at 180°C to remove organic matter and pore-forming agents, and then sintering at 950°C to form a porous oxide solid electrolyte membrane, which is then set aside for use.

[0040] In some embodiments, the thickness of the porous oxide solid electrolyte membrane is 20-80 μm, and the thickness of the porous oxide solid electrolyte membrane in the examples is 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, etc. In the preparation process of the porous oxide solid electrolyte membrane, because a set amount of pore-forming agent is added, the obtained porous oxide solid electrolyte membrane is an integrated microporous ceramic sheet with certain pores, and the obtained porous oxide solid electrolyte membrane not only has certain pores, but also has a certain ion transmission capacity.

[0041] In S2, a lithium salt is dissolved in an organic solvent to obtain an ionic liquid with a concentration range of 0.8-10 mol / L, wherein the concentration of lithium ions is greater than 0.8 mol / L. In some embodiments, the concentration range of the ionic liquid is 0.8 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, etc.

[0042] The exemplary lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorobisoxalate borate, lithium difluorophosphate, and lithium bis(trifluoromethylsulfonyl imide); the organic solvent includes at least one of diethyl ether, toluene, tetrahydrofuran, fluorocarbonate, ethylene carbonate, dimethyl carbonate, or ethyl methyl carbonate. The organic solvent used to prepare the ionic liquid must be dried at the end. To ensure that the organic solvent is finally retained inside the electrolyte membrane and does not affect the performance of the composite solid electrolyte membrane, the present application selects at least one of diethyl ether, toluene, tetrahydrofuran, fluorocarbonate, ethylene carbonate, dimethyl carbonate, or ethyl methyl carbonate, but cannot select acetonitrile, N,N-dimethylformamide (DMF), etc.

[0043] A viscosity enhancer is added to the ionic liquid so that the viscosity of the ionic liquid is in the range of 500-15000 mPa·S, for example, the viscosity of the ionic liquid is in the range of 500 mPa·S, 1000 mPa·S, 2000 mPa·S, 3000 mPa·S, 5000 mPa·S, 6000 mPa·S, 7000 mPa·S, 8000 mPa·S, 9000 mPa·S, 10000 mPa·S, 15000 mPa·S, etc. Exemplary viscosity enhancers include at least one of polyimide hot melt adhesive, ethylene-vinyl acetate copolymer, styrene-isoprene-styrene block copolymer, polyethylene wax or polyethylene oxide wax. In this step, the mass percentage of the thickener is 3%-50% based on the ionic liquid, and the mass percentage of the thickener is 3%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 50%, etc. When the mass percentage of the thickener is too large, such as greater than 50%, the viscosity of the ionic liquid will be too large, and the ionic liquid cannot effectively penetrate into the porous oxide solid electrolyte membrane; when the mass percentage of the thickener is too small, such as less than 3%, the viscosity of the ionic liquid will be too small, and the ionic liquid will be less bound in the porous oxide solid electrolyte membrane, resulting in ionic liquid loss during the cycle, and the battery performance will decrease. In addition, because the composite solid electrolyte membrane to be formed in this embodiment is dense and maintains a certain viscosity, but the fluidity is poor; the ionic liquid in this application has a higher lithium ion concentration to make up for the shortcomings caused by the poor fluidity of the electrolyte through high-concentration lithium ions.

[0044] In S3, the ionic liquid is heated to a flowing state and pressure is applied to allow the ionic liquid to penetrate into the porous oxide solid electrolyte membrane. For example, the ionic liquid is placed in the permeation chamber of the osmotic pressure device, heated to 90°C, so that the ionic liquid has good fluidity, the porous oxide solid electrolyte membrane is placed in the osmotic pressure device, pressure is applied, the ionic liquid is pushed to penetrate into the oxide electrolyte membrane, the electrolyte membrane is fully infiltrated, the excess ionic liquid on the surface is removed, and it is restored to room temperature until it cannot flow, and a composite solid electrolyte membrane is obtained. In this step, a high-viscosity ionic liquid is filled in the body and surface of the porous oxide solid electrolyte membrane by osmotic pressure, and a high concentration of lithium salt or polymer lithium salt is infiltrated into the voids of the sintered porous oxide solid electrolyte membrane to achieve rapid infiltration of the ionic liquid and efficient utilization of the porous oxide solid electrolyte membrane, which can effectively improve the ionic conductivity of the composite solid electrolyte membrane and effectively improve the interface contact between the solid electrolyte membrane and the electrode material.

[0045] In the related art, the method of improving the ionic conductivity of the solid electrolyte membrane by adding conductive materials, the present application avoids the chemical stability and safety problems that may be caused by adding conductive materials, and can also better maintain the porous structure of the composite solid electrolyte membrane, so as to better play its role as an electrolyte. In addition, in the related art, the interface contact between the solid electrolyte membrane and the electrode plate is improved by adding a binder, and the present application avoids the problem of decreased mechanical strength and ionic conductivity that may be caused by adding a binder, and can better maintain the mechanical strength and ionic conductivity of the solid electrolyte membrane.

[0046] In addition, the present application can achieve separate infiltration of the solid electrolyte membrane by infiltrating a high concentration of lithium salt or polymer lithium salt into the voids of the sintered porous oxide solid electrolyte membrane, thereby saving battery infiltration time; at the same time, the lithium salt material or polymer lithium salt material can be evenly distributed in the electrolyte membrane. In the related art, it is necessary to infiltrate the lithium salt material or polymer lithium salt material into the electrode material together with the electrolyte membrane. The present application can greatly shorten the cycle and cost of battery manufacturing, and can also avoid the impact of long-term infiltration on the structure and performance of the electrolyte membrane. At the same time, compared with the problem of uneven distribution of lithium salt materials or polymer lithium salt materials in electrode materials in the related art, the present application can achieve uniform distribution of lithium salt materials or polymer lithium salt materials in the electrolyte membrane, which can improve the performance of secondary batteries, thereby improving the energy density and cycle life of the battery.

[0047] According to an embodiment of the second aspect of the present application, a composite solid electrolyte membrane is proposed, which is obtained by using the preparation method in any of the above embodiments.

[0048] The thickness of the composite solid electrolyte membrane is 5 μm-90 μm, and its ionic conductivity is (1.09-4.25)×10 - 4 S cm -1 .

[0049] The composite solid electrolyte membrane in the present application effectively improves the ionic conductivity and solves the problem of interface contact between the composite solid electrolyte membrane and the electrode plate compared to the solid electrolyte membrane in the related art, and only a very small amount of ionic liquid is used to exert the performance of the secondary battery.

[0050] According to an embodiment of the third aspect of the present application, a secondary battery is provided, which includes the composite solid electrolyte membrane in any of the above embodiments.

[0051] The secondary battery in this embodiment further includes a positive electrode sheet and a negative electrode sheet, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material. As an example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0052] The positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0053] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery known in the art. As an example, the positive electrode active material may include at least one of the following materials: As an example, the positive electrode active material may include but is not limited to lithium iron phosphate (LiFePO 4 ), lithium manganese phosphate (LiMnPO 4 ), lithium cobalt phosphate (LiCoPO 4 ), ferric pyrophosphate (Li 2 FeP 2 O 7 ), lithium cobalt oxide (LiCoO 2 ), spinel lithium manganese oxide (LiMn 2 O 4 ), spinel lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4 ) Lithium manganese oxide (LiMnO 2 ) Lithium nickel oxide (LiNiO 2 ) Lithium niobate (LiNbO 2 ) Lithium ferrite (LiFeO 2 ) Lithium manganate (LiMgO 2 ) Lithium calcium oxide (LiCaO 2 ) Lithium copper oxide (LiCuO 2 ) Lithium zinc oxide (LiZnO 2 ) Lithium molybdate (LiMoO 2 ) Lithium tantalate (LiTaO 2 ) Lithium tungstate (LiWO 2 ) Lithium nickel cobalt aluminum oxide (LiNi x Co y Al 1-x-y O 2 , 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example LiNi 0.8 Co 0.15 Al 0.05 O 2 ) Lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O 2 , 0 < x < 1, 0 < y < 1, 0 < x + y < 1, for example LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 , LiNi 0.6 Co 0.2 Mn 0.2 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 etc.), lithium-rich materials (such as lithium-rich nickel cobalt manganese oxide), manganese oxide (MnO 2 ), vanadium oxide, sulfur oxide, silicate oxide, and at least one of their respective modified compounds. These materials can be used alone or in combination of two or more.

[0054] The modified compounds of the above positive electrode active materials can be doping modification, surface coating modification, or simultaneous doping and coating modification of the positive electrode active materials, etc.

[0055] In some embodiments, the positive electrode film layer may also optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0056] In some embodiments, the positive electrode film layer may further include a conductive agent, for example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0057] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0058] [Negative electrode]

[0059] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material. As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0060] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0061] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0062] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0063] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0064] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0065] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0066] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the composite solid electrolyte membrane can be formed into an electrode assembly through a lamination process.

[0067] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0068] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0069] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape.

[0070] By applying the positive electrode active material with high compaction, higher capacity and higher energy efficiency prepared in the above embodiments to a secondary battery, the obtained secondary battery has the properties of high capacity, high compaction, ultra-long cycle and the like.

[0071] According to an embodiment of the fourth aspect of the present application, an energy storage device is provided, which includes the secondary battery in any of the above embodiments.

[0072] To facilitate further understanding of the present application, the scheme of the present application is further described below in conjunction with the embodiments. Those skilled in the art will understand that the description in the present application is only part of the examples, and any other suitable specific examples are within the scope of the present application.

[0073] Example 1

[0074] The present embodiment provides a composite solid electrolyte membrane, and its preparation method and specific operating parameters are as follows: 36.67g of lithium nitrate, 15g of aluminum isopropoxide, 48.33g of phosphoric acid and 100g of tetraisopropyl titanate are dissolved and dispersed in isopropanol to form a precursor solution, 60g of ammonium bicarbonate is added as a pore-forming agent, the viscosity is adjusted, and the mixture is stirred evenly at room temperature. The precursor solution containing the pore-forming agent is poured on a substrate, a 35μm thick film is prepared using a scraper, and the solvent is slowly dried in an oven. Pre-sintering is first performed at 180°C to remove organic matter and the pore-forming agent, and then sintering is performed at 950°C to form a porous LATP (lithium aluminum titanium phosphate) membrane, which is left for standby use.

[0075] 87.03 g of lithium bis(trifluoromethylsulfonylimide) was dissolved in 100 mL of tetrahydrofuran to prepare an ionic liquid with a concentration of 3 mol / L. After it was fully dissolved, 9.35 g of polyethylene oxide wax was added as a thickener. The obtained ionic liquid had a viscosity of 2540 mPa·S and was set aside for later use.

[0076] A high-viscosity ionic liquid is placed in the osmotic chamber of an osmotic pressure device and heated to 90°C to allow the ionic liquid to have good fluidity. A porous oxide electrolyte membrane is placed in the osmotic pressure device and pressure is applied to push the ionic liquid to penetrate into the oxide electrolyte membrane and fully wet the electrolyte membrane. Excess ionic liquid on the surface is removed and the membrane is restored to room temperature until it can no longer flow, thereby obtaining a composite solid electrolyte membrane.

[0077] Example 2

[0078] This embodiment is different from Embodiment 1 in the following aspects: 29.1 g of lithium bis(trifluoromethylsulfonyl imide) is dissolved in 100 mL of tetrahydrofuran to prepare an ionic liquid with a concentration of 1 mol / L.

[0079] Example 3

[0080] This example is different from Example 1 in the following aspects: 145.05 g of lithium bis(trifluoromethylsulfonyl imide) is dissolved in 100 mL of tetrahydrofuran to prepare a 5 mol / L ionic liquid.

[0081] Example 4

[0082] This embodiment is different from Embodiment 1 in that 3.74 g of polyethylene oxide wax is used as a thickener to prepare an ionic liquid with a viscosity of 800 mPa·S.

[0083] Example 5

[0084] This embodiment is different from Embodiment 1 in that 14.96 g of polyethylene oxide wax is used as a thickener to prepare an ionic liquid with a viscosity of 6200 mPa·S.

[0085] Comparative Example 1

[0086] This comparative example is different from Example 1 in that the ionic liquid is not permeated into the porous LATP (lithium aluminum titanium phosphate) membrane.

[0087] Comparative Example 2

[0088] This comparative example is different from Example 1 in that a common electrolyte is infiltrated into the porous LATP (lithium aluminum titanium phosphate) membrane.

[0089] Test Case

[0090] The composite solid electrolyte membranes prepared in the above embodiments and comparative examples were cut into suitable sizes (diameter φ19, thickness 35 μm) for ion conductivity testing. The testing method is as follows: an electrochemical workstation with an AC impedance test function was used to test using an AC impedance method, and the test frequency range was 0.1-106 Hz.

[0091] The oxide solid electrolyte membrane in each embodiment and comparative example is assembled with the positive electrode plate and the negative electrode plate into a button battery, wherein the positive electrode plate uses a high-nickel NCM ternary material; the negative electrode plate uses a silicon-carbon Si-C material. The button batteries formed by the oxide solid electrolyte membrane in each embodiment and comparative example are tested for the first discharge capacity, coulomb efficiency and capacity retention rate after 30 cycles. The test method is as follows: In the voltage range of 2.5-4.2V, the first charge and discharge test is first performed at 0.1C, and then a cycle test is performed at 0.2C charging and 0.2C discharging for 30 cycles, and the capacity retention rate of the battery is recorded. All tests are performed at room temperature, and the results are shown in Table 1.

[0092] Table 1 Test results of positive electrode active materials in various embodiments and comparative examples

[0093]

[0094] According to the comparison between Examples 1-5 and Comparative Examples 1-2, it can be seen that the penetration of an ionic liquid of a certain viscosity in the porous oxide solid electrolyte membrane is beneficial to improving the ion transmission capacity of the composite solid electrolyte membrane and the interface contact between the composite solid electrolyte membrane and the electrode plate. By comparing Examples 1-3, it can be seen that when the concentration of the ionic liquid is too low, the transmission of ions is blocked, affecting the performance of the battery. As the ion concentration increases, the ion transmission efficiency reaches a certain peak value, and the cycle performance of the battery performance will not continue to increase; reducing the viscosity of the ionic liquid, the battery performance initially shows a certain advantage. As the number of cycles increases, the flowable ionic liquid is consumed, resulting in a decrease in the battery cycle retention rate. Excessive viscosity of the ionic liquid will also cause ion transmission to be blocked, resulting in a decrease in battery performance.

[0095] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0096] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A method for preparing a composite solid electrolyte membrane, characterized in that: The following steps are involved: A first mixed solution formed by a precursor solution of an oxide solid electrolyte and a pore former is formed into a porous oxide solid electrolyte membrane by a tape casting method; Dissolving a lithium salt in an organic solvent to obtain an ionic liquid with a concentration range of 0.8-10 mol / L, wherein the concentration of lithium ions is greater than 0.8 mol / L, and adding a thickener to the ionic liquid to make the viscosity of the ionic liquid range from 500 to 15000 mPa·S; The ionic liquid is infiltrated into the porous oxide solid electrolyte membrane by applying pressure to obtain a composite solid electrolyte membrane.

2. The preparation method according to claim 1, characterized in that: The oxide solid electrolyte includes lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum zirconium aluminum oxide, lithium lanthanum zirconium gallium oxide, lithium lanthanum titanium oxide, lithium aluminum germanium phosphate or lithium aluminum titanium phosphate; and / or, the pore-forming agent comprises at least one of ammonium bicarbonate, polyethylene, urea, polypropylene, polystyrene or polymethyl acrylate; And / or, based on the precursor solution, the mass percentage of the pore-forming agent is 20%-60%; And / or, the porous oxide solid electrolyte membrane has a thickness of 20-80 μm.

3. The preparation method according to claim 1 or 2, characterized in that: The lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorobisoxalatoborate, lithium difluorophosphate, and lithium bis(trifluoromethylsulfonyl imide); and / or, the organic solvent comprises at least one of ether, toluene, tetrahydrofuran, fluorocarbonate, ethylene carbonate, dimethyl carbonate or ethyl methyl carbonate; and / or, the tackifier includes at least one of polyimide hot melt adhesive, ethylene-vinyl acetate copolymer, styrene-isoprene glycol-styrene block copolymer, polyethylene wax or polyethylene oxide wax; And / or, based on the ionic liquid, the mass percentage of the viscosity enhancer is 3%-50%.

4. The preparation method according to claim 3, characterized in that: The ionic liquid is heated to a fluid state and pressure is applied to allow the ionic liquid to penetrate into the porous oxide solid electrolyte membrane.

5. The preparation method according to claim 4, characterized in that: The ionic liquid and the porous oxide solid electrolyte membrane are placed in an osmotic pressure device; after the porous oxide solid electrolyte membrane is fully infiltrated, the excess ionic liquid on the surface is removed, and then the temperature is restored to room temperature.

6. A composite solid electrolyte membrane, characterized in that: The method is obtained by any one of claims 1 to 5.

7. The composite solid electrolyte membrane according to claim 6, characterized in that: The thickness of the composite solid electrolyte membrane is 5 μm-90 μm.

8. The composite solid electrolyte membrane according to claim 6, characterized in that: The ionic conductivity of the composite solid electrolyte membrane is (1.09-4.25)×10 -4 S cm -1 .

9. A secondary battery, comprising the composite solid electrolyte membrane according to any one of claims 6 to 8.

10. An electrical device, characterized in that: A secondary battery comprising the secondary battery according to claim 9.

Images