Composite solid electrolyte membrane with high ionic conductivity as well as preparation method and application of composite solid electrolyte membrane

Abstract

The invention relates to a composite solid electrolyte membrane with high ionic conductivity as well as a preparation method and application thereof. The composite solid electrolyte membrane comprises a porous matrix membrane, composite solid electrolytes and a copolymer, wherein the surfaces and pores of the porous matrix membrane are filled with the composite solid electrolytes, and the copolymer forms a cross-linked network among the composite solid electrolytes; the porous matrix membrane comprises a matrix material, a plasticizer, a first lithium salt and a fluorocarbon surfactant; the composite solid electrolyte is of a core-shell structure, an inner core is a solid electrolyte, and an outer shell is a metal organic framework with pores adsorbing ionic liquid; the ionic liquid is synthesized from imidazole ionic liquid and second lithium salt; the copolymer is formed by initiating in-situ polymerization of an organic matter monomer and a cross-linking agent through an initiator. The composite solid-state electrolyte membrane and the solid-state battery are prepared through in-situ polymerization, and the composite solid-state electrolyte membrane with high ionic conductivity can improve the electrochemical window of the solid-state battery, reduce the surface resistance and improve the cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state battery materials, and in particular to a composite solid-state electrolyte membrane with high ionic conductivity, a preparation method and applications thereof. Background Art

[0002] All-solid-state lithium-ion batteries, which use solid electrolytes instead of organic electrolytes, are expected to break through the technical bottlenecks of traditional lithium-ion batteries. They address the oxidation, reduction, and thermal decomposition of organic electrolytes, their incompatibility with high-voltage, high-energy-density cathode materials, and the unstable high-temperature storage, rapid decline in low-temperature performance, susceptibility to thermal runaway, and the formation of lithium dendrites at the negative electrode of traditional lithium-ion batteries. These batteries can achieve higher energy density, power density, cycle life, and safety, and even further reduce costs. Therefore, all-solid-state lithium-ion batteries have become recognized by academics and industry worldwide as the future development direction.

[0003] In all-solid-state batteries, an ideal solid-state electrolyte membrane should possess low area resistance, high ionic conductivity, a reasonable thickness, high mechanical strength, good chemical stability, and lightweight properties. However, conventional solid-state electrolytes used in solid-state electrolyte membranes face a core contradiction: low ionic conductivity, high interfacial impedance, and a narrow electrochemical window.

[0004] For example, polymer electrolytes represented by PEO-Li TFSI have high room temperature crystallinity resulting in low ionic conductivity (<10 -5 S / cm), and the mechanical strength and ion conductivity are inversely related (for example, the conductivity drops sharply when the cross-linking degree is increased), the electrochemical window is narrow, and it cannot match the high-voltage positive electrode (such as NMC811). Inorganic solid electrolytes have the problem that the particle interface impedance affects the overall ion transfer efficiency. Traditional oxide ceramic solid electrolytes (such as LLZO, LATP) have high bulk conductivity, but poor rigid interface contact (high surface resistance); sulfide electrolytes (such as LPS) are sensitive to air and have violent side reactions with the positive electrode interface. There is also a scheme to simply mix polymers, oxide ceramic solid electrolytes, and ionic liquids to prepare composite electrolytes. The ion transfer mode of polymers and ceramic electrolytes is different, which hinders the high conductivity of ceramic electrolytes. In addition, ceramic fillers are easy to agglomerate to form an ion transfer "dead zone", and there is a multiphase interface Li + The problem of migration barrier (low lithium ion migration number).

[0005] In-situ polymerization is a simple method for preparing polymer electrolytes that is compatible with existing commercial battery production. It can produce thin and uniform polymer electrolytes with excellent compatibility with the electrode interface, which helps to reduce interfacial impedance and improve lithium ion transmission flux at the interface. However, in-situ polymerized solid electrolytes often suffer from uneven polymerization and polymer wrapping that affects ion transmission, which affects the performance of solid-state batteries and makes it difficult to meet the requirements of industrial promotion. Therefore, it is necessary to develop an in-situ polymerized solid electrolyte membrane that can improve polymerization uniformity, interfacial compatibility, and high mechanical strength while also reducing surface resistance, increasing ionic conductivity and electrochemical window, and thus improving the cycle stability of solid-state batteries. Summary of the Invention

[0006] The purpose of the present invention is to address the defects of the prior art and to propose a composite solid electrolyte membrane with high ionic conductivity, a preparation method and an application thereof.

[0007] This invention innovatively proposes a four-dimensional synergistic "core-shell-liquid-polymer" composite solid electrolyte membrane. The "core" is the solid electrolyte, the "shell" is the metal-organic framework, the "liquid" is the ionic liquid adsorbed on the metal-organic framework, and the "polymer" is a three-dimensional network copolymer formed by in situ polymerization. The solid electrolyte provides a high-speed pathway for lithium ions, while the porous shell of the metal-organic framework confines the adsorption of the ionic liquid to achieve liquid-state conduction. The in situ polymerized cross-linked network then coats the particles and fills the pores of the porous matrix membrane. This design simultaneously overcomes three bottlenecks: retaining the high ionic conductivity of the solid electrolyte at room temperature, optimizing contact with the electrode, reducing interfacial impedance, and combining rigidity and flexibility to adapt to current conventional battery manufacturing processes. It provides a disruptive solution for high-safety, high-energy-density solid-state batteries.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a composite solid electrolyte membrane with high ionic conductivity, the composite solid electrolyte membrane comprising: a porous substrate membrane, a composite solid electrolyte filled on the surface and in the pores of the porous substrate membrane, and a copolymer forming a cross-linked network between the composite solid electrolytes;

[0009] The composite solid electrolyte has a core-shell structure, wherein the core is a solid electrolyte and the shell is a metal organic framework with ionic liquid adsorbed in the pores;

[0010] The copolymer is formed by in-situ polymerization of organic monomers and a cross-linking agent initiated by an initiator.

[0011] Preferably, the porous matrix membrane comprises: a matrix material, a plasticizer, a first lithium salt and a fluorocarbon surfactant; the ionic liquid is synthesized by an imidazole ionic liquid and a second lithium salt;

[0012] Further preferably, the matrix material includes: one or more of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polypropylene oxide (PPO), and polyurethane acrylate (PUA); the percentage of the mass of the matrix material to the mass of the porous matrix membrane is 32% to 48%;

[0013] The plasticizer includes one or more of succinonitrile (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC); the mass percentage of the plasticizer to the mass percentage of the porous base film is 32% to 48%;

[0014] The first lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB); the mass percentage of the first lithium salt to the mass of the porous substrate membrane is 5% to 20%;

[0015] The fluorocarbon surfactant includes one or more of perfluoroalkyl ethoxymethyl ether, hexafluorobutyl methacrylate, perfluorooctane sulfonate and its derivatives, perfluorooctanoic acid and its salts, sodium perfluorononenyloxybenzenesulfonate, perfluorooctyl quaternary ammonium iodide, perfluoroalkyl polyoxyethylene ether, and perfluorooctyl dimethylamine oxide; the percentage of the mass of the fluorocarbon surfactant to the mass of the porous base membrane is 0.1% to 1%.

[0016] Further preferably, the thickness of the outer shell of the composite solid electrolyte is 10 nm to 50 nm;

[0017] The metal organic framework comprises: zeolite imidazolate framework-8 (ZIF-8);

[0018] The solid electrolyte includes: an oxide solid electrolyte and / or a fluoride oxide solid electrolyte; wherein the oxide solid electrolyte specifically includes: a garnet oxide solid electrolyte Li7A13B12O 12 , perovskite oxide solid electrolyte Li 3x A2 2 / 3-x B2O3, NASICON type oxide solid electrolyte Li 1+y A3 y B3 2-y(PO4)3, wherein 0.01≤x≤0.5, 0.01≤y≤0.5; A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf; A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr; A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf;

[0019] The fluoride oxide solid electrolyte specifically includes: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 、Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 、Li2VO2F、Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 、Li m La n M1 a M2 b M3 c One or more of O6F; wherein, 1<m+3n<5, 0<m≤2, 1 / 3<n<5 / 3; 0≤a≤2, 0≤b≤2, 0≤c≤2, a+b+c=2, M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn, M2 is one or more of Nb, Sb, Bi, V, Ta, and M3 is one or more of W, Cr, Mo, and Mn;

[0020] The imidazole ionic liquid includes: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIMTFSI);

[0021] The second lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB); the mass of the second lithium salt accounts for 5% to 20% of the total mass of the ionic liquid;

[0022] The organic monomers include triethylene glycol dimethacrylate (TEGDMA), butyl acrylate (BA), vinyl ethylene carbonate (VEC) and trimethylolpropane triacrylate (TMPTA);

[0023] The cross-linking agent includes: polyethylene glycol diacrylate-200 (PEGDA-200);

[0024] The initiator includes: azobisisobutyronitrile (AIBN);

[0025] The mass percentage of the copolymer to the mass percentage of the composite solid electrolyte membrane is 10wt% to 50wt%;

[0026] The ion conductivity of the composite solid electrolyte membrane is greater than 5 mS / cm.

[0027] In a second aspect, the present invention provides a method for preparing the composite solid electrolyte membrane according to the first aspect, the preparation method comprising:

[0028] Step S1, preparing a porous substrate membrane, comprising: heating and stirring a substrate material, a plasticizer, and a first lithium salt as raw materials with a solvent to obtain a first mixed solution, adding a fluorocarbon surfactant, continuing to heat and stir to obtain a first mixed solution, casting the solution into a glass mold, and vacuum drying to form pores to obtain a porous substrate membrane;

[0029] Step S2, preparing a composite solid electrolyte by a hydrothermal method, including: pretreating the solid electrolyte to obtain a solid electrolyte dispersion; preparing a metal organic framework precursor solution, a Zn(NO3)2 solution and a 2-methylimidazole solution; adding the solid electrolyte dispersion to the Zn(NO3)2 solution and stirring evenly, slowly adding the 2-methylimidazole solution dropwise and continuing to stir to obtain a second mixed solution; transferring the second mixed solution to a polytetrafluoroethylene-lined reactor for a hydrothermal reaction; collecting the product by centrifugation, and then washing and vacuum drying in sequence to obtain a core-shell structure solid electrolyte;

[0030] Step S3, preparing a composite solid electrolyte, comprising: preparing an ionic liquid, mixing an imidazole ionic liquid with a second lithium salt, heating and stirring until transparent to obtain an ionic liquid; mixing a core-shell structure solid electrolyte with the ionic liquid to obtain an ionic mixed liquid, vacuum impregnating the ionic mixed liquid to allow the metal organic framework of the shell of the core-shell structure solid electrolyte to adsorb the ionic liquid, and centrifuging to remove unadsorbed ionic liquid to obtain a composite solid electrolyte;

[0031] Step S4, preparing an in-situ polymerization solution, comprising: mixing a crosslinking agent and an organic monomer, adding the composite solid electrolyte, continuing to stir, adding an initiator azobisisobutyronitrile, and stirring evenly to obtain a uniformly dispersed in-situ polymerization solution;

[0032] Step S5, preparing a composite solid electrolyte membrane, including: coating or dripping the evenly dispersed in situ polymerization liquid onto one side of the porous base membrane to obtain a base membrane containing the in situ polymerization liquid; hot pressing the base membrane containing the in situ polymerization liquid during the assembly of the solid-state battery, so that the in situ polymerization liquid is in situ polymerized and solidified in the porous base membrane, and the composite solid electrolyte is filled into the pores of the porous base membrane to obtain a composite solid electrolyte membrane.

[0033] Preferably, in step S1, the matrix material includes: one or more of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polypropylene oxide (PPO), and polyurethane acrylate (PUA);

[0034] The plasticizer includes one or more of succinonitrile (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC);

[0035] The first lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB); the fluorocarbon surfactant includes one or more of perfluoroalkyl ethoxymethyl ether, hexafluorobutyl methacrylate, perfluorooctane sulfonate and its derivatives, perfluorooctanoic acid and its salts, sodium perfluorononenyloxybenzenesulfonate, perfluorooctyl quaternary ammonium iodide, perfluoroalkyl polyoxyethylene ether, and perfluorooctyl dimethylamine oxide;

[0036] In the raw materials, the mass ratio of the base material, the plasticizer and the first lithium salt is 4-6:4-6:2-0.5;

[0037] The solvent includes: one or more of acetone, N,N-dimethylformamide (DMF), and acetonitrile;

[0038] The mass ratio of the raw material to the solvent is 10wt% to 30wt%;

[0039] The mass ratio of the fluorocarbon surfactant to the first mixed solution is 0.1wt%-1wt%;

[0040] The heating and stirring temperature is 50°C to 80°C, and the heating and stirring time is 0.5 hours to 6 hours;

[0041] The vacuum drying pore-forming temperature is 60°C to 100°C, and the vacuum drying time is 1 hour to 8 hours;

[0042] The thickness of the porous base film is 30 μm to 150 μm.

[0043] Preferably, in step S2, the pretreatment of the solid electrolyte specifically comprises: calcining a solid electrolyte having a particle size Dv50 of 1 nm to 500 nm at 500° C. for 1 to 6 hours to remove surface impurities, dispersing the solid electrolyte in methanol after cooling, and ultrasonically dispersing the solid electrolyte for 10 to 60 minutes to obtain a solid electrolyte dispersion having a solid content of 5 wt% to 30 wt%;

[0044] The method for preparing a metal organic framework precursor solution comprises: dissolving Zn(NO3)2·6H2O in methanol to obtain a Zn(NO3)2 solution having a solid content of 5 wt% to 30 wt%; dissolving 2-methylimidazole in methanol to obtain a 2-methylimidazole solution having a solid content of 5 wt% to 30 wt%;

[0045] Add the solid electrolyte dispersion to the Zn(NO3)2 solution and stir for 10 to 60 minutes until uniform, then slowly dropwise add the 2-methylimidazole solution and continue stirring for 10 to 60 minutes to obtain the second mixed solution;

[0046] The temperature of the hydrothermal reaction is 50°C to 150°C, and the hydrothermal reaction time is 4 hours to 10 hours;

[0047] The washing comprises: washing with methanol 1 to 6 times;

[0048] The vacuum drying temperature is 50° C. to 80° C., and the drying time is 1 hour to 12 hours.

[0049] Preferably, in step S3, the imidazole ionic liquid includes: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM TFSI);

[0050] The second lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB).

[0051] The mass ratio of the imidazole ionic liquid to the second lithium salt is 20:1 to 5:1;

[0052] The heating and stirring temperature is 40°C to 60°C, and the heating and stirring time is 1 hour to 6 hours;

[0053] The solid content of the ionic mixed liquid is 5wt% to 30wt%;

[0054] The vacuum impregnation equipment is a vacuum oven; the specific conditions of the vacuum impregnation include: impregnation treatment for 1 hour to 6 hours under a vacuum degree of -0.1 MPa.

[0055] Preferably, in step S4, the organic monomers include: triethylene glycol dimethacrylate (TEGDMA), butyl acrylate (BA), vinyl ethylene carbonate (VEC) and trimethylolpropane triacrylate (TMPTA);

[0056] The cross-linking agent includes: polyethylene glycol diacrylate-200 (PEGDA-200);

[0057] The mass ratio of the cross-linking agent to the organic monomer is 1-3:2-10;

[0058] The mass percentage of the composite solid electrolyte to the in-situ polymerization solution is 10wt% to 30wt%;

[0059] The initiator includes: azobisisobutyronitrile (AIBN); the mass percentage of the composite solid electrolyte to the in-situ polymerization solution is 0.5wt% to 5wt%;

[0060] The method of subjecting the in-situ polymerized liquid-based membrane to hot pressing during the assembly of a solid-state battery specifically includes placing the in-situ polymerized liquid-based membrane on the negative electrode sheet, covering it with the positive electrode sheet, and then placing it in a hot press for 1 to 12 hours at a temperature of 60°C to 120°C and a pressure of 8MPa to 12MPa, so that the in-situ polymerized liquid is in-situ polymerized and solidified in the porous matrix membrane, and the composite solid electrolyte is filled into the pores of the porous matrix membrane to obtain a composite solid electrolyte membrane.

[0061] In a third aspect, the present invention provides a solid-state battery, comprising the composite solid-state electrolyte membrane described in the first aspect, or the composite solid-state electrolyte membrane obtained by the preparation method described in the second aspect.

[0062] The present invention provides a composite solid electrolyte membrane with high ionic conductivity, and a preparation method and application thereof, which have the following beneficial effects:

[0063] (1) The present invention provides a method for preparing a composite solid electrolyte membrane with high ionic conductivity and a solid-state battery. First, a porous matrix membrane containing a matrix material, a plasticizer, a lithium salt, and a fluorocarbon surfactant is prepared; a composite solid electrolyte having a core of a solid electrolyte and an outer shell of a metal organic framework ZIF-8 adsorbed with an ionic liquid is prepared; the composite solid electrolyte is mixed with a cross-linking agent, an organic monomer, and an initiator to prepare an in-situ polymerization liquid; the in-situ polymerization liquid is then coated or dripped onto one side of the porous matrix membrane, and then assembled with a negative electrode sheet and a positive electrode sheet to form a solid-state battery. During the hot pressing process of the battery, the in-situ polymerization liquid is in-situ polymerized and solidified, and the composite solid electrolyte is extruded and filled into the pores of the porous matrix membrane to form a composite solid electrolyte membrane, and a solid-state battery containing the composite solid electrolyte membrane. The preparation method provided by the present invention is easy to operate and can be applied to large-scale production.

[0064] (2) The composite solid electrolyte membrane obtained by the preparation method provided by the present invention has a porous matrix membrane containing lithium salt as a porous skeleton, the pores of the porous skeleton are filled with a composite solid electrolyte, and the composite solid electrolyte is in situ polymerized to form a copolymer with a three-dimensional cross-linked network; the composite solid electrolyte provided by the present invention has a core of a solid electrolyte and an outer shell of a metal organic framework ZIF-8 adsorbed with ionic liquid. On the one hand, the solid electrolyte as the core has good ionic conductivity and high mechanical strength, which can improve the ionic conductivity and compressive strength of the composite solid electrolyte membrane; on the other hand, the pores of the outer shell metal organic framework ZIF-8 contain EMIM TFS I and lithium salt ionic liquid, the ionic liquid in the flowing state can still make the core solid electrolyte have the characteristics of high ionic conductivity when the composite solid electrolyte is wrapped by the copolymer of the three-dimensional cross-linked network, and the ion migration will not be hindered by the copolymer wrapping; and the copolymer of the three-dimensional cross-linked network formed between the composite solid electrolyte constitutes a continuous ion conduction network, which can conduct ions with the ionic liquid in the composite solid electrolyte, and the ion channels of the composite solid electrolyte membrane are formed between the three-dimensional cross-linked network, the ionic liquid and the solid electrolyte, thereby greatly improving the ionic conductivity of the composite solid electrolyte membrane, reducing the surface resistance, increasing the ion migration number, and improving the electrochemical window, and the solid-state battery containing the composite solid electrolyte membrane has good cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 Flowchart of a method for preparing a composite solid electrolyte membrane provided by an embodiment of the present invention.

[0066] Figure 2 This is a scanning electron microscope (SEM) image of the porous substrate membrane prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0067] In order to make the objects, technical solutions and advantages of the present application clearer, the following further describes the present application in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those ordinarily skilled in the art without creative effort belong to the scope of the present application.

[0068] The technical solutions of the present application are further described in detail below with reference to the accompanying drawings and embodiments.

[0069] The embodiment of the present application provides a composite solid electrolyte membrane with high ionic conductivity, comprising: a porous base film, a composite solid electrolyte filled on the surface and in the pores of the porous base film, and a copolymer forming a crosslinked network between the composite solid electrolytes; the ionic conductivity of the composite solid electrolyte membrane is > 5 mS / cm.

[0070] The porous base film comprises: a base material, a plasticizer, a first lithium salt and a fluorocarbon surfactant; the thickness of the porous base film is 30 μm-150 μm, which can be any value within this range, for example: 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, etc., but is not limited to the listed values, and other values not listed within this range are also applicable.

[0071] Specifically, the base material comprises one or more of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polypropylene oxide (PPO), and polyurethane acrylate (PUA); the percentage of the mass of the base material to the mass of the porous base film is 32%-48%, which can be any value within this range, for example: 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, etc., but is not limited to the listed values, and other values not listed within this range are also applicable.

[0072] The plasticizer includes one or more of succinonitrile (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC). The percentage of the mass of the plasticizer to the mass of the porous base film is 32% to 48%, and can be any value within this range, such as 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, etc., but is not limited to the values ​​listed above. Other values ​​not listed within this range are also applicable.

[0073] The first lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB). The percentage of the mass of the first lithium salt to the mass of the porous substrate membrane is 5% to 20%, and can be any value within this range, for example, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0074] Fluorocarbon surfactants include one or more of perfluoroalkyl ethoxymethyl ether, hexafluorobutyl methacrylate, perfluorooctane sulfonate and its derivatives, perfluorooctanoic acid and its salts, sodium perfluorononenyloxybenzenesulfonate, perfluorooctyl quaternary ammonium iodide, perfluoroalkyl polyoxyethylene ether, and perfluorooctyl dimethylamine oxide. The percentage of the mass of the fluorocarbon surfactant to the mass of the porous substrate membrane is 0.1% to 1.0%, and can be any value within this range, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc., but is not limited to the listed values. Other values ​​not listed within this range are also applicable. Fluorocarbon surfactants can reduce the surface tension of the substrate membrane and improve wettability.

[0075] The pores of the composite solid electrolyte membrane are filled with a composite solid electrolyte, which has a core-shell structure, with the core being a solid electrolyte (SSE) and the shell being a metal organic framework (MOF) that adsorbs ionic liquids in the pores; the thickness of the shell of the composite solid electrolyte is 10 nm to 50 nm, and can be any value within this range, for example: 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, etc., but is not limited to the listed values, and other values ​​not listed within this numerical range are also applicable.

[0076] The solid electrolyte includes: an oxide solid electrolyte and / or a fluoride oxide solid electrolyte.

[0077] Specifically, the oxide solid electrolyte includes: garnet-type oxide solid electrolyte Li7A13B12O 12 , perovskite oxide solid electrolyte Li 3x A2 2 / 3-x B2O3, NASICON type oxide solid electrolyte Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤x≤0.5, 0.01≤y≤0.5; A1 is one or more of La, Ca, Sr, Ba, K, B1 is one or more of Zr, Ta, Nb, Hf; A2 is one or more of La, Al, Mg, Fe, Ta, B2 is one or more of Ti, Nb, Sr, Pr; A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, La, B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, Hf elements.

[0078] Fluoride oxide solid electrolytes specifically include: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 、Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 、Li2VO2F、Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 、Li m La n M1 a M2 b M3 c One or more of O6F; wherein, 1<m+3n<5, 0<m≤2, 1 / 3<n<5 / 3; 0≤a≤2, 0≤b≤2, 0≤c≤2, a+b+c=2, M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn, M2 is one or more of Nb, Sb, Bi, V, Ta, and M3 is one or more of W, Cr, Mo, and Mn.

[0079] In the present invention, the solid electrolyte used is preferably a fluoride oxide solid electrolyte Li m La n M1a M2 b M3 c O6F, wherein, 1 < m + 3n < 5, 0 < m < 2, 1 / 3 < n < 5 / 3; 0 < a < 2, 0 < b < 2, 0 < c < 2, a + b + c = 2, M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn, M2 is one or more of Nb, Sb, Bi, V, Ta, and M3 is one or more of W, Cr, Mo, Mn; because the oxyfluoride solid-state electrolyte Li m La n M1 a M2 b M3 c O6F solid-state electrolyte has high density, high purity, and high volume energy density, low internal resistance and excellent ion conduction performance, and Li m La n M1 a M2 b M3 c O6F solid-state electrolyte has a rigid backbone structure with adjustable element composition, and the introduction of a diversified coordination environment by multivalent cation doping is conducive to the formation of open channels conducive to lithium ion transmission, and the doping of fluorine elements can further enhance the polarity and interface wettability of the material, improve the interface contact with the electrolyte and the electrode, and reduce the interface impedance. The present application forms a continuous layered structure of Li m La n M1 a M2 b M3 c O6F solid-state electrolyte backbone on the surface and pore wall of the porous carbon skeleton, so that the obtained silicon-carbon composite material has excellent ion conduction performance and interface stability.

[0080] The metal organic framework comprises: zeolitic imidazolate framework-8 (ZIF-8); ZIF-8 combines the high stability of inorganic molecular sieve and the high porosity and organic function of metal organic framework, and is more easy to adsorb and contain ionic liquid.

[0081] The ionic liquid is synthesized by an imidazole ionic liquid and a second lithium salt; specifically, the imidazole ionic liquid includes 1-ethyl-3-methyl imidazole bis (trifluoromethyl sulfonate) imine (EMIM TFSI); the second lithium salt includes one or more of lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium bis (fluorosulfonyl) imide (LiFSI), lithium perchlorate (LiClO4), lithium bis (oxalate) borate (LiBOB); the mass percentage of the second lithium salt in the total mass of the ionic liquid is 5% to 20%, which can be any value within this range, for example: 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc., but not limited to the listed values, other values not listed within this range are also applicable.

[0082] The copolymer in the composite solid electrolyte is formed by in-situ polymerization of an organic monomer and a crosslinking agent initiated by an initiator; the mass percentage of the copolymer in the mass of the composite solid electrolyte film is 10wt% to 50wt%, which can be any value within this range, for example: 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, etc., but not limited to the listed values, other values not listed within this range are also applicable.

[0083] The organic monomer includes: triethylene glycol dimethacrylate (TEGDMA), butyl acrylate (BA), ethylene carbonate (VEC), and trimethylolpropane triacrylate (TMPTA); the crosslinking agent includes: polyethylene glycol diacrylate-200 (PEGDA-200); the initiator includes: azobisisobutyronitrile (AIBN).

[0084] The embodiment of the present application provides a preparation method of the composite solid electrolyte film, as shown in the figure, the preparation method comprises the following steps. Figure 1

[0085] Step S1, preparing a porous matrix film.

[0086] Specifically, the matrix material, plasticizer and first lithium salt are mixed uniformly as raw materials with a solvent by heating and stirring to obtain a first mixed solution, then a fluorocarbon surfactant is added, and the mixture is uniformly heated and stirred, then poured into a glass mold, vacuum dried to form pores, and a porous matrix film is obtained.

[0087] The matrix material includes one or more of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polypropylene oxide (PPO), and polyurethane acrylate (PUA);

[0088] ​The plasticizer includes one or more of succinonitrile (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC).

[0089] The first lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB).

[0090] Fluorocarbon surfactants include: one or more of perfluoroalkyl ethoxymethyl ether, hexafluorobutyl methacrylate, perfluorooctane sulfonate and its derivatives, perfluorooctanoic acid and its salts, sodium perfluorononenyloxybenzenesulfonate, perfluorooctyl quaternary ammonium iodide, perfluoroalkyl polyoxyethylene ether, and perfluorooctyl dimethylamine oxide.

[0091] In the raw materials, the mass ratio of the base material, the plasticizer and the first lithium salt is 4-6:4-6:2-0.5;

[0092] The solvent includes one or more of acetone, N,N-dimethylformamide (DMF), and acetonitrile.

[0093] The mass ratio of the raw material to the solvent is 10wt% to 30wt%.

[0094] The mass ratio of the fluorocarbon surfactant to the first mixed solution is 0.1 wt%-1 wt%.

[0095] The heating and stirring temperature is 50° C. to 80° C., and the heating and stirring time is 0.5 hour to 6 hours.

[0096] The temperature for vacuum drying and pore formation is 60° C. to 100° C., and the time for vacuum drying is 1 hour to 8 hours.

[0097] Step S2, preparing a composite solid electrolyte by a hydrothermal method.

[0098] Specifically, the method includes: pre-treating the solid electrolyte to obtain a solid electrolyte dispersion; preparing a metal organic framework precursor solution, a Zn(NO3)2 solution and a 2-methylimidazole solution; adding the solid electrolyte dispersion to the Zn(NO3)2 solution and stirring evenly, slowly adding the 2-methylimidazole solution and continuing to stir to obtain a second mixed solution; transferring the second mixed solution to a polytetrafluoroethylene-lined reactor for a hydrothermal reaction; collecting the product by centrifugation, and then washing and vacuum drying in sequence to obtain a core-shell structure solid electrolyte.

[0099] Among them, the pretreatment of the solid electrolyte specifically includes: calcining the solid electrolyte with a particle size Dv50 of 1nm to 500nm at 500℃ for 1 hour to 6 hours to remove surface impurities, dispersing it in methanol after cooling, and ultrasonically dispersing it for 10min to 60min to obtain a solid electrolyte dispersion with a solid content of 5wt% to 30wt%.

[0100] The preparation of the metal organic framework precursor solution includes: dissolving Zn(NO3)2·6H2O in methanol to obtain a Zn(NO3)2 solution with a solid content of 5wt% to 30wt%; dissolving 2-methylimidazole in methanol to obtain a 2-methylimidazole solution with a solid content of 5wt% to 30wt%.

[0101] The solid electrolyte dispersion is added to the Zn(NO3)2 solution and stirred for 10 to 60 minutes. After stirring evenly, the 2-methylimidazole solution is slowly added dropwise and stirred for 10 to 60 minutes to obtain a second mixed solution.

[0102] The temperature of the hydrothermal reaction is 50° C. to 150° C., and the hydrothermal reaction time is 4 hours to 10 hours.

[0103] Washing includes: washing with methanol 1 to 6 times.

[0104] The vacuum drying temperature is 50° C. to 80° C., and the time is 1 hour to 12 hours.

[0105] Step S3, preparing a composite solid electrolyte, including: preparing an ionic liquid, mixing an imidazole ionic liquid with a second lithium salt, heating and stirring until transparent to obtain an ionic liquid; mixing a core-shell structure solid electrolyte with the ionic liquid to obtain an ionic mixed liquid, vacuum impregnating the ionic mixed liquid to allow the metal organic framework of the core-shell structure solid electrolyte shell to adsorb the ionic liquid, and centrifuging to remove the unadsorbed ionic liquid to obtain a composite solid electrolyte.

[0106] Among them, the imidazolium ionic liquid includes: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIMTFSI).

[0107] The second lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB).

[0108] The mass ratio of the imidazole ionic liquid to the second lithium salt is 20:1 to 5:1.

[0109] The heating and stirring temperature is 40°C to 60°C, and the heating and stirring time until transparent is generally 1 hour to 6 hours.

[0110] The solid content of the ionic mixed liquid is 5wt% to 30wt%.

[0111] The equipment for vacuum impregnation is a vacuum oven; the specific conditions for vacuum impregnation include: impregnation treatment for 1 hour to 6 hours under a vacuum degree of -0.1 MPa.

[0112] Step S4, preparing an in-situ polymerization solution, includes: mixing a crosslinking agent and an organic monomer, adding a composite solid electrolyte, continuing to stir, adding an initiator azobisisobutyronitrile, stirring evenly, to obtain a uniformly dispersed in-situ polymerization solution.

[0113] The organic monomers include triethylene glycol dimethacrylate (TEGDMA), butyl acrylate (BA), vinyl ethylene carbonate (VEC) and trimethylolpropane triacrylate (TMPTA).

[0114] Cross-linking agents include polyethylene glycol diacrylate-200 (PEGDA-200).

[0115] The mass ratio of the cross-linking agent to the organic monomer is 1-3:2-10.

[0116] The mass percentage of the composite solid electrolyte in the in-situ polymerization liquid is 10wt% to 30wt%.

[0117] The initiator comprises: azobisisobutyronitrile (AIBN); the mass percentage of the composite solid electrolyte in the in-situ polymerization liquid is 0.5wt% to 5wt%.

[0118] Step S5, preparing a composite solid electrolyte membrane, including: coating or dripping a uniformly dispersed in-situ polymerization liquid onto one side of a porous base membrane to obtain a base membrane containing the in-situ polymerization liquid; hot pressing the base membrane containing the in-situ polymerization liquid during the assembly of a solid-state battery, so that the in-situ polymerization liquid is in-situ polymerized and solidified in the porous base membrane, and the composite solid electrolyte is filled into the pores of the porous base membrane to obtain a composite solid electrolyte membrane.

[0119] The base membrane containing the in-situ polymerization liquid is subjected to a hot pressing treatment during the process of assembling a solid-state battery, so that the in-situ polymerization liquid is in-situ polymerized and solidified in the porous base membrane, and the composite solid electrolyte is filled into the pores of the porous base membrane to obtain a composite solid electrolyte membrane. Specifically, the base membrane containing the in-situ polymerization liquid is placed on the negative electrode plate, covered with the positive electrode plate, and then placed in a hot press, and hot pressed for 1 hour to 12 hours at a temperature of 60°C to 120°C and a pressure of 8MPa to 12MPa, so that the in-situ polymerization liquid is in-situ polymerized and solidified in the porous base membrane, and the composite solid electrolyte is filled into the pores of the porous base membrane to obtain a composite solid electrolyte membrane.

[0120] The above-mentioned composite solid electrolyte membrane provided by the embodiment of the present invention is combined with the negative electrode sheet and the positive electrode sheet through hot pressing and in-situ polymerization to obtain a solid-state battery.

[0121] Among them, there are no special restrictions on the negative electrode sheets, and any negative electrode sheets that can be used in solid-state batteries can be used. The negative electrode sheets are prepared by conventional methods; the negative electrode sheets are classified according to the negative active materials contained, including but not limited to: lithium metal sheets, silicon-carbon negative electrode sheets, graphite negative electrode sheets, graphene negative electrode sheets, transition metal negative electrode sheets, etc.

[0122] There are no special restrictions on the positive electrode sheets, and any positive electrode sheets that can be used in solid-state batteries can be used; the positive electrode sheets are prepared by conventional methods; the positive electrode sheets are classified according to the positive electrode active materials contained, including but not limited to: positive electrode sheets containing lithium cobalt oxide, positive electrode sheets containing ternary materials, positive electrode sheets containing lithium manganese oxide positive electrodes, positive electrode sheets containing lithium iron phosphate, etc., among which the ternary materials can be NCM523, NCM622, NCM811, etc.

[0123] To better understand the technical solutions provided by the present invention, the following describes the preparation process of the composite solid electrolyte membrane with high ionic conductivity and the preparation process and characteristics of the solid-state battery of the present invention using multiple specific examples.

[0124] Example 1

[0125] This embodiment provides a preparation process of a composite solid electrolyte membrane with high ionic conductivity and a solid-state battery, as follows.

[0126] (1) A porous substrate membrane is prepared, specifically: 50 g of substrate material PVDF, 50 g of plasticizer SN and 10 g of lithium salt LiFSI are used as raw materials and mixed with 350 ml of acetone and 150 ml of DMF solvent, heated and stirred at 60°C for 5 hours, and mixed to obtain a first mixed solution, and then perfluoroalkyl ethoxymethyl ether is added, and after further heating and stirring, the mixture is cast into a glass mold, and vacuum dried at 70°C for 5 hours to form pores, thereby obtaining a porous substrate membrane with a thickness of 100 μm; wherein the mass of perfluoroalkyl ethoxymethyl ether is 0.5 wt% of the first mixed solution.

[0127] The SEM image of the porous base membrane prepared in this step is as follows: Figure 2 shown.

[0128] (2) preparing a composite solid electrolyte by a hydrothermal method, specifically comprising:

[0129] The fluoride oxide solid electrolyte Li with a particle size of Dv50 of 100 nm 1.25 La 0.58Nb2O6F powder was calcined at 500°C for 3 hours to remove surface impurities, and then dispersed in 50 ml of methanol after cooling and ultrasonically dispersed for 30 minutes to obtain a solid electrolyte dispersion with a solid content of 10 wt%;

[0130] Dissolve Zn(NO3)2·6H2O in 25 ml of methanol to obtain a Zn(NO3)2 solution with a solid content of 10 wt%;

[0131] 2-Methylimidazole was dissolved in 25 ml of methanol to obtain a 2-methylimidazole solution with a solid content of 10 wt%;

[0132] The solid electrolyte dispersion and Zn(NO3)2 solution were mixed and stirred for 30 minutes, and then 2-methylimidazole solution was slowly added dropwise and stirred for 30 minutes to obtain a second mixed solution; the second mixed solution was transferred to a polytetrafluoroethylene-lined reactor and subjected to hydrothermal reaction at 100°C for 6 hours; the product was collected by centrifugation, washed with methanol 3 times, and then vacuum dried at 60°C for 6 hours to obtain a Li core. 1.25 La 0.58 Nb2O6F, a core-shell solid electrolyte with a ZIF-8 shell, referred to as SSE@ZIF-8.

[0133] (3) Preparing a composite solid electrolyte, specifically comprising: preparing an ionic liquid, mixing 10 g of an imidazole ionic liquid EMIMTFSI with 1 g of a lithium salt LiTFSI, heating and stirring at 50° C. until transparent, to obtain an ionic liquid; uniformly mixing the core-shell structure solid electrolyte prepared in step (2) with the ionic liquid to obtain an ionic mixed liquid with a solid content of 20%, and immersing the ionic mixed liquid at 50° C. under a vacuum degree of -0.1 MPa for 3 hours to perform vacuum impregnation so that the ZIF-8 of the core-shell structure solid electrolyte shell is fully infiltrated and adsorbed with the ionic liquid, and removing the unadsorbed ionic liquid by centrifugation to obtain a composite solid electrolyte.

[0134] (4) preparing an in-situ polymerization solution, comprising: mixing 300 g of a cross-linking agent PEGDA-200 and 500 g of an organic monomer TEGDMA, adding the composite solid electrolyte prepared in step (3), continuing stirring, adding an initiator azobisisobutyronitrile, and stirring uniformly to obtain a uniformly dispersed in-situ polymerization solution; wherein the mass of the composite solid electrolyte accounts for 20 wt % of the in-situ polymerization solution, and the mass of the azobisisobutyronitrile accounts for 1 wt % of the in-situ polymerization solution.

[0135] (5) Preparing a composite solid electrolyte membrane, comprising: adding a uniformly dispersed in-situ polymerization liquid dropwise to one side of a porous substrate membrane to obtain a base membrane containing the in-situ polymerization liquid; placing the base membrane containing the in-situ polymerization liquid on a negative electrode sheet (the negative electrode sheet is a commercial graphite negative electrode sheet), covering it with a positive electrode sheet (the positive electrode sheet is a commercial lithium iron phosphate positive electrode sheet), and then placing it in a hot press, hot pressing it at a temperature of 80°C and a pressure of 8 MPa for 6 hours, so that the in-situ polymerization liquid is in-situ polymerized and solidified in the porous substrate membrane, and the composite solid electrolyte is filled into the pores of the porous substrate membrane, thereby obtaining a composite solid electrolyte membrane, and a solid-state battery containing the composite solid electrolyte membrane.

[0136] The ionic conductivity, surface resistance, electrochemical window, and lithium ion transference number of the composite solid electrolyte membrane prepared in this example were tested, and the cycle performance of the prepared solid-state battery was tested.

[0137] Test 1, ionic conductivity test: The ionic conductivity was determined by electrochemical impedance spectroscopy (EIS) on an electrochemical workstation. The specific steps are as follows: First, the in-situ polymerized liquid-based membrane prepared in step (5) is placed between two stainless steel (SS) inert electrodes, and after encapsulation, it is treated at 80°C for 6 hours to form a composite solid electrolyte membrane through in-situ polymerization and prepare a battery (SS|SPE|SS); to ensure the accuracy of the test, the test battery is placed in a constant temperature box for temperature control. In the EIS test, the frequency range is set to 0.01Hz to 1MHz, and the amplitude voltage is set to 10mV, in order to accurately measure the resistance of the composite solid electrolyte membrane. Then, through the analysis of the Nyquist impedance spectrum, the corresponding formula can be used to calculate the ionic conductivity of the electrolyte as follows: In the process of measuring ionic conductivity, d in the formula represents the thickness of the composite solid electrolyte membrane, R is the bulk resistance of the composite solid electrolyte membrane read from the Nyquist impedance diagram of EIS, and S represents the effective contact area between the composite solid electrolyte membrane and the stainless steel inert electrode. In order to ensure the accuracy of the measurement, when testing the ionic conductivity at different temperatures, it is necessary to set the thermostat to the target temperature and maintain it for half an hour to allow the test cell to reach thermal equilibrium. This step ensures the stability of the test environment, so that the ionic conductivity of the composite solid electrolyte membrane at this temperature can be accurately measured. The ionic conductivity tests of the present invention are all carried out at 25±2°C and a humidity of less than 50%. The test data are detailed in Table 1.

[0138] Test 2, calculation of sheet resistance: Sheet resistance = impedance value (R) × effective contact area (S) between the composite solid electrolyte membrane and the stainless steel inert electrode.

[0139] Test 3, testing the electrochemical window: Before the test, a lithium metal sheet was used as the reference electrode and the counter electrode, and a stainless steel sheet (SS) was used as the working electrode. The in-situ polymerized liquid-based membrane prepared in step (5) of this embodiment was placed on the stainless steel sheet, covered with a lithium metal sheet, and then packaged and treated at 80°C for 6 hours to perform in-situ polymerization to form a composite solid electrolyte membrane and prepare a lithium / composite solid electrolyte membrane / stainless steel (Li|SPE|SS) battery. The battery was then subjected to linear sweep voltammetry (LSV) testing in a constant temperature box at room temperature. During the test, the scan rate was set to 1 millivolt per second (mV / s), and the electrochemical window was tested from the open circuit voltage to 6V. The test results are detailed in Table 1.

[0140] Test 4, lithium ion migration number test: First, prepare a lithium-lithium symmetrical battery (Li|SPE|Li), use two lithium metal sheets as counter electrodes, place the in-situ polymerization liquid-based membrane prepared in step (5) of this embodiment on the lithium metal sheet, cover it with another lithium metal sheet, and after packaging, treat it at 80°C for 6 hours to perform in-situ polymerization to form a composite solid electrolyte membrane and prepare a Li|SPE|Li battery; it can be tested by chronoamperometry on an electrochemical workstation. This process involves applying a voltage of 10mV to the Li|SPE|Li symmetrical battery and recording the initial current and the current when it reaches steady state. The interface impedance between the composite solid electrolyte membrane and the lithium metal sheet at the initial and steady state is recorded by EIS. The lithium ion migration number is then calculated according to the following formula:

[0141] Where ΔV is the applied voltage, I0 and I s Represent the initial current and steady-state current, R0 and R s represent the interfacial impedance between the electrolyte and the lithium metal sheet at the initial and steady states, respectively.

[0142] Test 5, cycle capacity retention test: The solid-state battery prepared in this embodiment was cycled for 500 cycles at a current density of 3C using a blue electric tester, and the capacity retention was recorded.

[0143] Example 2

[0144] This embodiment provides a preparation process of a composite solid electrolyte membrane with high ionic conductivity and a solid-state battery. The difference from Example 1 is that step (1) is specifically as follows: 40g of matrix material PVDF, 30g of plasticizer SN and 5g of lithium salt LiFSI are used as raw materials and mixed with 300ml of acetone and 200ml of DMF solvent, heated and stirred at 80°C for 3 hours, and mixed to obtain a first mixed solution after uniformity, and then hexafluorobutyl methacrylate is added, and after further heating and stirring, the mixture is cast in a glass mold, and vacuum dried at 70°C for 5 hours to form pores, to obtain a porous matrix membrane with a thickness of 100μm; wherein the mass of hexafluorobutyl methacrylate is 1wt% of the first mixed solution.

[0145] The other preparation steps are the same as those in Example 1.

[0146] The ionic conductivity, surface resistance, electrochemical window and lithium ion transference number of the composite solid electrolyte membrane prepared in this embodiment were tested, and the cycle performance of the prepared solid-state battery was tested, using the same testing method as in Example 1.

[0147] Example 3

[0148] This embodiment provides a preparation process of a composite solid electrolyte membrane with high ionic conductivity and a solid-state battery. The difference from embodiment 1 is that step (2) is as follows: the fluoride oxide solid electrolyte Li 1.25 La 0.58 The particle size of Nb2O6F is Dv50, which is 300 nm.

[0149] The other preparation steps are the same as those in Example 1.

[0150] The ionic conductivity, surface resistance, electrochemical window and lithium ion transference number of the composite solid electrolyte membrane prepared in this embodiment were tested, and the cycle performance of the prepared solid-state battery was tested, using the same testing method as in Example 1.

[0151] Example 4

[0152] This embodiment provides a preparation process of a composite solid electrolyte membrane with high ionic conductivity and a solid-state battery. The difference from Example 1 is that step (3) is specifically: 5 g of imidazole ionic liquid EMIM TFSI and 1 g of lithium salt LiTFSI are mixed, heated and stirred at 60°C until transparent to obtain an ionic liquid; after the core-shell structure solid electrolyte and the ionic liquid are evenly mixed, an ionic mixed liquid with a solid content of 15% is obtained, and the ionic mixed liquid is immersed in a vacuum condition of -0.1 MPa at 60°C for 5 hours to perform vacuum impregnation so that the ZIF-8 of the core-shell structure solid electrolyte shell is fully infiltrated and adsorbed with the ionic liquid, and the unadsorbed ionic liquid is removed by centrifugation to obtain a composite solid electrolyte.

[0153] The other preparation steps are the same as those in Example 1.

[0154] The ionic conductivity, surface resistance, electrochemical window and lithium ion transference number of the composite solid electrolyte membrane prepared in this embodiment were tested, and the cycle performance of the prepared solid-state battery was tested, using the same testing method as in Example 1.

[0155] Example 5

[0156] This embodiment provides a preparation process of a composite solid electrolyte membrane with high ionic conductivity and a solid-state battery. The difference from Example 1 is that step (4) is specifically: mixing 200 g of a cross-linking agent PEGDA-200 and 700 g of an organic monomer BA, adding the composite solid electrolyte, continuing to stir, adding an initiator azobisisobutyronitrile, stirring evenly, to obtain a uniformly dispersed in-situ polymerization solution; wherein the mass of the composite solid electrolyte accounts for 15 wt % of the in-situ polymerization solution, and the mass of the azobisisobutyronitrile accounts for 0.5 wt % of the in-situ polymerization solution.

[0157] The other preparation steps are the same as those in Example 1.

[0158] The ionic conductivity, surface resistance, electrochemical window and lithium ion transference number of the composite solid electrolyte membrane prepared in this embodiment were tested, and the cycle performance of the prepared solid-state battery was tested, using the same testing method as in Example 1.

[0159] Example 6

[0160] This embodiment provides a preparation process of a composite solid electrolyte membrane with high ionic conductivity and a solid-state battery. The difference from Example 1 is that step (5) is specifically: placing a base membrane containing an in-situ polymerization liquid on a negative electrode plate (the negative electrode plate is a commercial graphite negative electrode plate), covering it with a positive electrode plate (the positive electrode plate is a commercial lithium iron phosphate positive electrode plate), and then placing it in a hot press, and hot pressing it at a temperature of 70°C and a pressure of 8 MPa for 8 hours, so that the in-situ polymerization liquid is in-situ polymerized and solidified in the porous base membrane, and the composite solid electrolyte is filled into the pores of the porous base membrane, thereby obtaining a composite solid electrolyte membrane and a solid-state battery containing the composite solid electrolyte membrane.

[0161] The other preparation steps are the same as those in Example 1.

[0162] The ionic conductivity, surface resistance, electrochemical window and lithium ion transference number of the composite solid electrolyte membrane prepared in this embodiment were tested, and the cycle performance of the prepared solid-state battery was tested, using the same testing method as in Example 1.

[0163] Example 7

[0164] This embodiment provides a preparation process of a composite solid electrolyte membrane with high ionic conductivity and a solid-state battery. The difference from Example 1 is that in step (2), different solid electrolyte raw materials are used. The core of the core-shell structure solid electrolyte of this embodiment is Li with a particle size of Dv50 of 100 nm. 1.3 Al 0.3 Ti 1.7 (PO4)3(LATP).

[0165] The other preparation steps are the same as those in Example 1.

[0166] The ionic conductivity, surface resistance, electrochemical window and lithium ion transference number of the composite solid electrolyte membrane prepared in this embodiment were tested, and the cycle performance of the prepared solid-state battery was tested, using the same testing method as in Example 1.

[0167] In order to better illustrate the effects of the embodiments of the present invention, a comparative example is compared with the above embodiments.

[0168] Comparative Example 1

[0169] The difference between this comparative example and Example 1 is that the porous substrate membrane prepared in step (1) of the example is directly used to assemble the negative electrode sheet and the positive electrode sheet into a full battery for testing.

[0170] The ionic conductivity, surface resistance, electrochemical window and lithium ion transference number of the porous substrate membrane prepared in this comparative example were tested, and the cycle performance of the prepared solid-state battery was tested, using the same testing method as in Example 1.

[0171] Comparative Example 2

[0172] The difference between this comparative example and Example 1 is that no composite solid electrolyte is added to the in-situ polymerization liquid, and the in-situ polymerization liquid is directly assembled into a solid-state battery according to the method of step (5) of Example 1.

[0173] The ionic conductivity, surface resistance, electrochemical window and lithium ion transference number of the composite solid electrolyte membrane prepared in this comparative example were tested, and the cycle performance of the prepared solid-state battery was tested, using the same testing method as in Example 1.

[0174] Comparative Example 3

[0175] The difference between this comparative example and Example 1 is that no ionic liquid is used, that is, no ionic liquid is adsorbed in the pores of the composite solid electrolyte shell ZIF-8, and the core-shell structure solid electrolyte SSE@ZIF-8 is directly prepared into an in-situ polymerization liquid according to step (4) of Example 1, and then the solid-state battery is prepared according to the method of step (5).

[0176] The ion conductivity, surface resistance, electrochemical window and lithium ion transference number of the composite solid electrolyte film prepared in the test comparative example were tested, and the cycle performance of the solid-state battery prepared was tested, and the test method was the same as that of example 1.

[0177] Table 1 is a summary of test data of the button cells assembled in examples 1-7 and comparative examples 1-3:

[0178]

[0179]

[0180] Table 1

[0181] As can be seen from the test data in Table 1, the ion conductivity of examples 1-6 is much higher than that of comparative examples 1-2, the surface resistance of examples 1-6 is significantly higher than that of comparative examples 1-2, the electrochemical window of examples 1-6 is significantly higher than that of comparative examples 1-2, and the lithium ion transference number of examples 1-6 is significantly higher than that of comparative examples 1-2. This is because comparative example 1 directly uses only a PVDF porous matrix film as an electrolyte, which is loose and porous on the surface, and the connection between the electrode and the electrolyte is not tight enough, which hinders the conduction of ions, so the electrochemical performance is poor. Comparative example 2 does not add a composite solid electrolyte, i.e. does not use a Li 1.25 La 0.58 Nb2O6F material with high ion conductivity, although in-situ solidification optimizes the interface contact, but the ion conductivity is low, which affects its electrochemical performance. Comparative example 3 does not use an ionic solution, and the Li 1.25 La 0.58 Nb2O6F material cannot play its own role as an ion conductor, and the electrochemical performance is hindered.

[0182] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific embodiment of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A composite solid electrolyte membrane with high ionic conductivity, characterized in that: The composite solid electrolyte membrane includes: a porous base membrane, a composite solid electrolyte filled on the surface and in the pores of the porous base membrane, and a copolymer forming a cross-linked network between the composite solid electrolytes; The composite solid electrolyte has a core-shell structure, wherein the core is a solid electrolyte and the shell is a metal organic framework with ionic liquid adsorbed in the pores; The copolymer is formed by in-situ polymerization of organic monomers and a cross-linking agent initiated by an initiator.

2. The composite solid electrolyte membrane according to claim 1, characterized in that The porous matrix membrane comprises: a matrix material, a plasticizer, a first lithium salt and a fluorocarbon surfactant; the ionic liquid is synthesized by an imidazole ionic liquid and a second lithium salt.

3. The composite solid electrolyte membrane according to claim 2, characterized in that The matrix material includes one or more of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polypropylene oxide (PPO), and polyurethane acrylate (PUA); the mass percentage of the matrix material to the mass of the porous matrix membrane is 32% to 48%; The plasticizer includes one or more of succinonitrile (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC); the mass percentage of the plasticizer to the mass percentage of the porous base film is 32% to 48%; The first lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB); the mass percentage of the first lithium salt to the mass of the porous substrate membrane is 5% to 20%; The fluorocarbon surfactant includes one or more of perfluoroalkyl ethoxymethyl ether, hexafluorobutyl methacrylate, perfluorooctane sulfonate and its derivatives, perfluorooctanoic acid and its salts, sodium perfluorononenyloxybenzenesulfonate, perfluorooctyl quaternary ammonium iodide, perfluoroalkyl polyoxyethylene ether, and perfluorooctyl dimethylamine oxide; the percentage of the mass of the fluorocarbon surfactant to the mass of the porous base membrane is 0.1% to 1%.

4. The composite solid electrolyte membrane according to claim 2, characterized in that The thickness of the shell of the composite solid electrolyte is 10nm to 50nm; The metal organic framework comprises: zeolite imidazolate framework-8 (ZIF-8); The solid electrolyte includes: an oxide solid electrolyte and / or a fluoride oxide solid electrolyte; wherein the oxide solid electrolyte specifically includes: a garnet oxide solid electrolyte Li7A13B12O 12 , perovskite oxide solid electrolyte Li 3x A2 2 / 3-x B2O3, NAS ICON type oxide solid electrolyte Li 1+y A3 y B3 2-y (PO4)3, wherein 0.01≤x≤0.5, 0.01≤y≤0.5; A1 is one or more of La, Ca, Sr, Ba, and K, and B1 is one or more of Zr, Ta, Nb, and Hf; A2 is one or more of La, Al, Mg, Fe, and Ta, and B2 is one or more of Ti, Nb, Sr, and Pr; A3 is one or more of Al, Y, Ga, Cr, In, Fe, Se, and La, and B3 is one or more of Ti, Ge, Ta, Zr, Sn, Fe, V, and Hf; The fluoride oxide solid electrolyte specifically includes: Li 1.5 Al 0.5 Ge 1.5 (PO4) 2.9 F 0.1 、Li 6.5 La3Zr 1.5 Ta 0.5 O 11.5 F 0.5 、Li2VO2F、Li 1.2 Mn 0.8 Nb 0.2 O 1.6 F 0.4 、Li m La n M1 a M2 b M3 c One or more of O6F; wherein, 1<m+3n<5, 0<m≤2, 1 / 3<n<5 / 3; 0≤a≤2, 0≤b≤2, 0≤c≤2, a+b+c=2, M1 is one or more of Zr, Ti, Hf, Si, Ge, Sn, M2 is one or more of Nb, Sb, Bi, V, Ta, and M3 is one or more of W, Cr, Mo, and Mn; The imidazole ionic liquid includes: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM TFS I); The second lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB); the mass of the second lithium salt accounts for 5% to 20% of the total mass of the ionic liquid; The organic monomers include triethylene glycol dimethacrylate (TEGDMA), butyl acrylate (BA), vinyl ethylene carbonate (VEC) and trimethylolpropane triacrylate (TMPTA); The cross-linking agent includes: polyethylene glycol diacrylate-200 (PEGDA-200); The initiator includes: azobisisobutyronitrile (AIBN); The mass percentage of the copolymer to the mass percentage of the composite solid electrolyte membrane is 10wt% to 50wt%; The ion conductivity of the composite solid electrolyte membrane is greater than 5 mS / cm.

5. A method for preparing a composite solid electrolyte membrane according to any one of claims 1 to 4, characterized in that: The preparation method comprises: Step S1, preparing a porous substrate membrane, comprising: heating and stirring a substrate material, a plasticizer, and a first lithium salt as raw materials with a solvent to obtain a first mixed solution, adding a fluorocarbon surfactant, continuing to heat and stir to obtain a first mixed solution, casting the solution into a glass mold, and vacuum drying to form pores to obtain a porous substrate membrane; Step S2, preparing a composite solid electrolyte by a hydrothermal method, including: pretreating the solid electrolyte to obtain a solid electrolyte dispersion; preparing a metal organic framework precursor solution, a Zn(NO3)2 solution and a 2-methylimidazole solution; adding the solid electrolyte dispersion to the Zn(NO3)2 solution and stirring evenly, slowly adding the 2-methylimidazole solution dropwise and continuing to stir to obtain a second mixed solution; transferring the second mixed solution to a polytetrafluoroethylene-lined reactor for a hydrothermal reaction; collecting the product by centrifugation, and then washing and vacuum drying in sequence to obtain a core-shell structure solid electrolyte; Step S3, preparing a composite solid electrolyte, comprising: preparing an ionic liquid, mixing an imidazole ionic liquid with a second lithium salt, heating and stirring until transparent to obtain an ionic liquid; mixing a core-shell structure solid electrolyte with the ionic liquid to obtain an ionic mixed liquid, vacuum impregnating the ionic mixed liquid to allow the metal organic framework of the shell of the core-shell structure solid electrolyte to adsorb the ionic liquid, and centrifuging to remove unadsorbed ionic liquid to obtain a composite solid electrolyte; Step S4, preparing an in-situ polymerization solution, comprising: mixing a crosslinking agent and an organic monomer, adding the composite solid electrolyte, continuing to stir, adding an initiator azobisisobutyronitrile, and stirring evenly to obtain a uniformly dispersed in-situ polymerization solution; Step S5, preparing a composite solid electrolyte membrane, including: coating or dripping the evenly dispersed in situ polymerization liquid onto one side of the porous base membrane to obtain a base membrane containing the in situ polymerization liquid; hot pressing the base membrane containing the in situ polymerization liquid during the assembly of the solid-state battery, so that the in situ polymerization liquid is in situ polymerized and solidified in the porous base membrane, and the composite solid electrolyte is filled into the pores of the porous base membrane to obtain a composite solid electrolyte membrane.

6. The preparation method according to claim 5, characterized in that In step S1, the matrix material includes: one or more of polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), polypropylene oxide (PPO), and polyurethane acrylate (PUA); The plasticizer includes one or more of succinonitrile (SN), polyvinyl alcohol (PVA), ethylene carbonate (EC), and propylene carbonate (PC); The first lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB). The fluorocarbon surfactants include one or more of perfluoroalkyl ethoxymethyl ether, hexafluorobutyl methacrylate, perfluorooctane sulfonate and its derivatives, perfluorooctanoic acid and its salts, sodium perfluorononenyloxybenzenesulfonate, perfluorooctyl quaternary ammonium iodide, perfluoroalkyl polyoxyethylene ether, and perfluorooctyl dimethylamine oxide; In the raw materials, the mass ratio of the base material, the plasticizer and the first lithium salt is 4-6:4-6:2-0.5; The solvent includes: one or more of acetone, N,N-dimethylformamide (DMF), and acetonitrile; The mass ratio of the raw material to the solvent is 10wt% to 30wt%; The mass ratio of the fluorocarbon surfactant to the first mixed solution is 0.1wt%-1wt%; The heating and stirring temperature is 50°C to 80°C, and the heating and stirring time is 0.5 hours to 6 hours; The vacuum drying pore-forming temperature is 60°C to 100°C, and the vacuum drying time is 1 hour to 8 hours; The thickness of the porous base film is 30 μm to 150 μm.

7. The preparation method according to claim 5, characterized in that In step S2, the pretreatment of the solid electrolyte specifically includes: calcining the solid electrolyte with a particle size Dv50 of 1 nm to 500 nm at 500° C. for 1 hour to 6 hours to remove surface impurities, dispersing the solid electrolyte in methanol after cooling, and ultrasonically dispersing the solid electrolyte for 10 minutes to 60 minutes to obtain the solid electrolyte dispersion with a solid content of 5 wt% to 30 wt%; The method for preparing a metal organic framework precursor solution comprises: dissolving Zn(NO3)2·6H2O in methanol to obtain a Zn(NO3)2 solution having a solid content of 5 wt% to 30 wt%; dissolving 2-methylimidazole in methanol to obtain a 2-methylimidazole solution having a solid content of 5 wt% to 30 wt%; Add the solid electrolyte dispersion to the Zn(NO3)2 solution and stir for 10 to 60 minutes until uniform, then slowly dropwise add the 2-methylimidazole solution and continue stirring for 10 to 60 minutes to obtain the second mixed solution; The temperature of the hydrothermal reaction is 50°C to 150°C, and the hydrothermal reaction time is 4 hours to 10 hours; The washing comprises: washing with methanol 1 to 6 times; The vacuum drying temperature is 50° C. to 80° C., and the drying time is 1 hour to 12 hours.

8. The preparation method according to claim 5, characterized in that In the step S3, the imidazole ionic liquid includes: 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMIM TFSI); The second lithium salt includes one or more of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium perchlorate (LiClO4), and lithium bis(oxalatoborate) (LiBOB). The mass ratio of the imidazole ionic liquid to the second lithium salt is 20:1 to 5:1; The heating and stirring temperature is 40°C to 60°C, and the heating and stirring time is 1 hour to 6 hours; The solid content of the ionic mixed liquid is 5wt% to 30wt%; The vacuum impregnation equipment is a vacuum oven; the specific conditions of the vacuum impregnation include: impregnation treatment for 1 hour to 6 hours under a vacuum degree of -0.1 MPa.

9. The preparation method according to claim 5, characterized in that In step S4, the organic monomers include triethylene glycol dimethacrylate (TEGDMA), butyl acrylate (BA), vinyl ethylene carbonate (VEC) and trimethylolpropane triacrylate (TMPTA); The cross-linking agent includes: polyethylene glycol diacrylate-200 (PEGDA-200); The mass ratio of the cross-linking agent to the organic monomer is 1-3:2-10; The mass percentage of the composite solid electrolyte to the in-situ polymerization solution is 10wt% to 30wt%; The initiator includes: azobisisobutyronitrile (AIBN); the mass percentage of the composite solid electrolyte to the in-situ polymerization solution is 0.5wt% to 5wt%; The method of subjecting the in-situ polymerized liquid-based membrane to hot pressing during the assembly of a solid-state battery specifically includes placing the in-situ polymerized liquid-based membrane on the negative electrode sheet, covering it with the positive electrode sheet, and then placing it in a hot press for 1 to 12 hours at a temperature of 60°C to 120°C and a pressure of 8MPa to 12MPa, so that the in-situ polymerized liquid is in-situ polymerized and solidified in the porous matrix membrane, and the composite solid electrolyte is filled into the pores of the porous matrix membrane to obtain a composite solid electrolyte membrane.

10. A solid-state battery, characterized in that: The solid-state battery comprises the composite solid electrolyte membrane described in any one of claims 1 to 4, or comprises the composite solid electrolyte membrane obtained by the preparation method described in any one of claims 5 to 9.

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