A double-layer solid electrolyte membrane for solid-state lithium batteries and a method for preparing the same
By coating the positive and negative electrode surfaces of solid-state lithium batteries with double-layer solid electrolyte films of different compositions, the problems of low ionic conductivity and high interfacial impedance of solid-state lithium batteries are solved, thereby improving battery performance and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG DAXIANG NEW ENERGY TECH CO LTD
- Filing Date
- 2022-08-09
- Publication Date
- 2026-06-09
AI Technical Summary
Existing solid-state lithium batteries suffer from low ionic conductivity, high interface impedance, and lithium dendrite formation, which affect battery electrical and safety performance.
A double-layer solid electrolyte membrane structure is adopted, in which the surface of the positive electrode is coated with a thicker solid electrolyte membrane composed of polymer solid electrolyte, inorganic solid electrolyte and lithium salt, and the surface of the negative electrode is coated with a thinner conductive solid electrolyte membrane composed of polymer solid electrolyte, inorganic solid electrolyte and lithium salt and conductive agent. This structure is achieved by adjusting the current density and reducing the interface impedance.
It improves the ionic conductivity and chemical stability of the solid electrolyte membrane, reduces interfacial impedance, prevents lithium dendrite formation, and enhances the battery's electrical and safety performance.
Abstract
Description
Technical Field
[0001] This invention relates to the field of solid-state lithium-ion battery technology, and more specifically to a double-layer solid electrolyte membrane for solid-state lithium batteries and its preparation method. Background Technology
[0002] Lithium-ion batteries are widely used due to their advantages such as high specific energy, high operating voltage, long cycle life, low self-discharge rate, and environmental friendliness. However, traditional liquid lithium-ion batteries contain organic carbonate-based liquid electrolytes, which have poor thermal stability and are flammable. When the batteries are abused and overheat, there are safety hazards such as leakage, fire, and explosion. Compared to traditional liquid lithium-ion batteries, solid-state lithium batteries use non-flammable, thermally stable solid electrolytes instead of organic electrolytes, resulting in higher energy density, longer cycle life, and better safety.
[0003] Solid-state electrolytes are classified into inorganic solid-state electrolytes and polymer solid-state electrolytes. Inorganic solid-state electrolytes generally have high ionic conductivity and a wide electrochemical window, but they are brittle. The solid-solid contact between the electrolyte and the electrode leads to insufficient contact and a large interfacial impedance, significantly affecting the battery's electrical performance. Polymer solid-state electrolytes are lightweight, easy to form films, and have good viscoelasticity, resulting in good processability and interfacial wettability. However, their low room-temperature ionic conductivity severely impacts battery performance. Especially in solid-state lithium batteries using lithium metal as the negative electrode, uneven current density during charging and discharging can easily lead to lithium dendrite formation, affecting both battery performance and safety.
[0004] Therefore, there is an urgent need to develop a solid electrolyte membrane with high ionic conductivity, low interfacial impedance, and tunable current density for use in solid-state lithium batteries. Summary of the Invention
[0005] The purpose of this invention is to provide a double-layer solid electrolyte membrane for solid-state lithium batteries and its preparation method, which aims to improve the ionic conductivity of the solid electrolyte membrane, reduce the interfacial impedance of the solid electrolyte membrane / electrode sheet, adjust the current density, prevent lithium dendrite formation, and improve the electrical and safety performance of solid-state lithium batteries, thereby solving the problems mentioned in the background art.
[0006] The technical solution adopted in this invention is as follows:
[0007] A double-layer solid electrolyte membrane for solid-state lithium batteries includes a solid electrolyte membrane A coated on the surface of the positive electrode of the battery and a solid electrolyte membrane B coated on the surface of the negative electrode of the battery. The solid electrolyte membrane A is composed of polymer solid electrolyte A, inorganic solid electrolyte and lithium salt, and the solid electrolyte membrane B is composed of polymer solid electrolyte B, inorganic solid electrolyte, lithium salt and conductive agent.
[0008] Furthermore, the polymer solid electrolyte A is one or more of polyacrylamide, polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene) copolymer and polyacrylonitrile, and the polymer solid electrolyte B is selected from polyethylene oxide.
[0009] Furthermore, the inorganic solid electrolyte is one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, lithium oxide-alumina, lithium oxide-silicon oxide-alumina, and lithium aluminum titanium phosphate.
[0010] Furthermore, the lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium difluoromethanesulfonylimide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium dioxalateborate.
[0011] Furthermore, the conductive agent is one or more of graphene, carbon nanotubes, conductive fibers, conductive graphite, and conductive carbon black.
[0012] Further, the weight ratio of the polymer solid electrolyte A, the inorganic solid electrolyte, and the lithium salt is 20-50:30-70:1-20, and the weight ratio of the polymer solid electrolyte B, the inorganic solid electrolyte, the lithium salt, and the conductive agent is 6-18:1-4:1-4:0.1-1.
[0013] Furthermore, the thickness of the solid electrolyte membrane A is 10–50 μm, and the thickness of the solid electrolyte membrane B is 2–10 μm.
[0014] The method for preparing a double-layer solid electrolyte membrane for solid-state lithium batteries includes the following steps:
[0015] Step 1: Preparation of solid electrolyte membrane A: Dissolve polymer solid electrolyte A in a mixed solvent of N,N-dimethylacetamide and acetone, then add lithium salt and inorganic solid electrolyte, stir evenly, coat it on the surface of the prepared positive electrode, and dry it to obtain solid electrolyte membrane A.
[0016] Step 2: Preparation of solid electrolyte membrane B: Dissolve polymer solid electrolyte B in a mixed solvent of N,N-dimethylacetamide and acetone, then add a conductive agent and continue stirring for 30-90 minutes. Then add lithium salt and inorganic solid electrolyte, stir evenly, coat the mixture onto the surface of the prepared negative electrode sheet, and dry to obtain solid electrolyte membrane B.
[0017] Furthermore, the active material of the positive electrode in step one is selected from one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide, and lithium manganese oxide, and the active material of the negative electrode in step two is selected from one or more of lithium metal, graphite, and silicon negative electrode.
[0018] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:
[0019] 1. The present invention directly coats a relatively thick solid electrolyte film on the surface of the positive electrode and a relatively thin conductive solid electrolyte film on the surface of the negative electrode. This can effectively improve the interfacial contact between the solid electrolyte and the electrode, reduce the interfacial impedance, and at the same time, the thicker solid electrolyte film on the positive electrode can play an electronic insulating role, while the thinner conductive solid electrolyte film on the negative electrode can uniformize the current density and prevent the formation of lithium dendrites, thereby improving the electrical performance and safety performance.
[0020] 2. The solid electrolyte membrane coated on the surface of the positive electrode of the present invention uses a solid electrolyte with oxidation resistance, and the conductive solid electrolyte membrane coated on the surface of the negative electrode uses a solid electrolyte with reduction resistance, thereby improving the chemical stability of the solid electrolyte membrane.
[0021] 3. In the solid electrolyte membrane coated on the surface of the positive electrode of the present invention, the content of inorganic solid electrolyte is higher than that of polymer solid electrolyte, which effectively improves ionic conductivity and thermal stability; in the conductive solid electrolyte membrane coated on the surface of the negative electrode, the content of polymer solid electrolyte is higher than that of inorganic solid electrolyte, which further improves the interfacial contact between solid electrolyte membranes and reduces interfacial impedance. At the same time, the addition of carbon nanotube conductive agent can effectively improve the mechanical strength and thermal stability of the solid electrolyte membrane. Detailed Implementation
[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.
[0023] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0024] Example
[0025] A double-layer solid electrolyte membrane for solid-state lithium batteries includes a solid electrolyte membrane A coated on the surface of the positive electrode of the battery and a solid electrolyte membrane B coated on the surface of the negative electrode of the battery. The solid electrolyte membrane A is composed of polymer solid electrolyte A, inorganic solid electrolyte and lithium salt, and the solid electrolyte membrane B is composed of polymer solid electrolyte B, inorganic solid electrolyte, lithium salt and conductive agent.
[0026] The polymer solid electrolyte A is one or more of polyacrylamide, polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene) copolymer and polyacrylonitrile, and the polymer solid electrolyte B is selected from polyethylene oxide.
[0027] The inorganic solid electrolyte is one or more of the following: lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, lithium oxide-aluminum oxide, lithium oxide-silicon oxide-aluminum oxide, and lithium aluminum titanium phosphate.
[0028] The lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium difluoromethanesulfonylimide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium dioxalate borate.
[0029] The conductive agent is one or more of graphene, carbon nanotubes, conductive fibers, conductive graphite, and conductive carbon black.
[0030] The weight ratio of the polymer solid electrolyte A, the inorganic solid electrolyte, and the lithium salt is 20-50:30-70:1-20, and the weight ratio of the polymer solid electrolyte B, the inorganic solid electrolyte, the lithium salt, and the conductive agent is 6-18:1-4:1-4:0.1-1.
[0031] The thickness of the solid electrolyte membrane A is 10–50 μm, and the thickness of the solid electrolyte membrane B is 2–10 μm.
[0032] The method for preparing a double-layer solid electrolyte membrane for solid-state lithium batteries includes the following steps:
[0033] Step 1: Preparation of solid electrolyte membrane A: Dissolve polymer solid electrolyte A in a mixed solvent of N,N-dimethylacetamide and acetone, then add lithium salt and inorganic solid electrolyte, stir evenly, coat it on the surface of the prepared positive electrode, and dry it to obtain solid electrolyte membrane A.
[0034] Step 2: Preparation of solid electrolyte membrane B: Dissolve polymer solid electrolyte B in a mixed solvent of N,N-dimethylacetamide and acetone, then add a conductive agent and continue stirring for 30-90 minutes. Then add lithium salt and inorganic solid electrolyte, stir evenly, coat the mixture onto the surface of the prepared negative electrode sheet, and dry to obtain solid electrolyte membrane B.
[0035] The active material of the positive electrode in step one is selected from one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide, and lithium manganese oxide. The active material of the negative electrode in step two is selected from one or more of lithium metal, graphite, and silicon negative electrode.
[0036] Example 1
[0037] This embodiment provides a double-layer solid electrolyte membrane for solid-state lithium batteries and its preparation method.
[0038] 20g of polyacrylamide was dissolved in 500mL of a mixed solvent of N,N-dimethylacetamide and acetone. Then, 10g of lithium bis(trifluoromethanesulfonyl)imide and 70g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of a positive electrode sheet with lithium nickel cobalt manganese oxide as the active material. After drying, a solid electrolyte membrane with a thickness of 20μm was prepared.
[0039] 80g of polyethylene oxide was dissolved in 700mL of a mixed solvent of N,N-dimethylacetamide and acetone. Then, 1g of carbon nanotubes was added and stirred for 60min. Next, 10g of lithium bis(trifluoromethanesulfonyl)imide and 9g of lithium lanthanum zirconium tantalum oxide were added and stirred until homogeneous. The mixture was then coated onto the surface of the active material, metallic lithium and dried to prepare a solid electrolyte membrane with a thickness of 5μm.
[0040] Example 2
[0041] 30g of polyacrylamide was dissolved in 500mL of N,N-dimethylacetamide / acetone mixed solvent, then 10g of lithium bis(trifluoromethanesulfonyl)imide and 60g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material. After drying, a solid electrolyte membrane with a thickness of 20μm was prepared.
[0042] 80g of polyethylene oxide was dissolved in 700mL of N,N-dimethylacetamide / acetone mixed solvent, then 1g of carbon nanotubes was added, and the mixture was stirred for 60min. Then, 10g of lithium bis(trifluoromethanesulfonyl)imide and 9g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated onto the surface of the active material lithium metal. After drying, a solid electrolyte membrane with a thickness of 5μm was prepared.
[0043] Example 3:
[0044] 40g of polyacrylamide was dissolved in 500mL of N,N-dimethylacetamide / acetone mixed solvent, then 10g of lithium bis(trifluoromethanesulfonyl)imide and 50g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material. After drying, a solid electrolyte membrane with a thickness of 20μm was prepared.
[0045] 80g of polyethylene oxide was dissolved in 700mL of N,N-dimethylacetamide / acetone mixed solvent, then 1g of carbon nanotubes was added, and the mixture was stirred for 60min. Then, 10g of lithium bis(trifluoromethanesulfonyl)imide and 9g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated onto the surface of the active material lithium metal. After drying, a solid electrolyte membrane with a thickness of 5μm was prepared.
[0046] Example 4:
[0047] 30g of polyacrylamide was dissolved in 500mL of N,N-dimethylacetamide / acetone mixed solvent, then 10g of lithium bis(trifluoromethanesulfonyl)imide and 60g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material. After drying, a solid electrolyte membrane with a thickness of 20μm was prepared.
[0048] 78g of polyethylene oxide was dissolved in 700mL of N,N-dimethylacetamide / acetone mixed solvent, then 3g of carbon nanotubes were added, and the mixture was stirred for 60min. Then, 10g of lithium bis(trifluoromethanesulfonyl)imide and 9g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated onto the surface of the active material lithium metal. After drying, a solid electrolyte membrane with a thickness of 5μm was prepared.
[0049] Example 5:
[0050] 30g of polyacrylamide was dissolved in 500mL of N,N-dimethylacetamide / acetone mixed solvent, then 10g of lithium bis(trifluoromethanesulfonyl)imide and 60g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material. After drying, a solid electrolyte membrane with a thickness of 20μm was prepared.
[0051] 75g of polyethylene oxide was dissolved in 700mL of N,N-dimethylacetamide / acetone mixed solvent, then 5g of carbon nanotubes were added, and the mixture was stirred for 60min. Then, 10g of lithium bis(trifluoromethanesulfonyl)imide and 9g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated onto the surface of the active material lithium metal. After drying, a solid electrolyte membrane with a thickness of 5μm was prepared.
[0052] Example 6:
[0053] 30g of polyacrylamide was dissolved in 500mL of N,N-dimethylacetamide / acetone mixed solvent, then 10g of lithium bis(trifluoromethanesulfonyl)imide and 60g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material. After drying, a solid electrolyte membrane with a thickness of 20μm was prepared.
[0054] 72g of polyethylene oxide was dissolved in 700mL of N,N-dimethylacetamide / acetone mixed solvent, then 3g of carbon nanotubes were added, and the mixture was stirred for 60min. Then, 10g of lithium bis(trifluoromethanesulfonyl)imide and 15g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated onto the surface of the active material lithium metal. After drying, a solid electrolyte membrane with a thickness of 5μm was prepared.
[0055] Example 7:
[0056] 30g of polyacrylamide was dissolved in 500mL of N,N-dimethylacetamide / acetone mixed solvent, then 10g of lithium bis(trifluoromethanesulfonyl)imide and 60g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material. After drying, a solid electrolyte membrane with a thickness of 20μm was prepared.
[0057] 67g of polyethylene oxide was dissolved in 700mL of N,N-dimethylacetamide / acetone mixed solvent, then 3g of carbon nanotubes were added and stirred for 60min. Then 10g of lithium bis(trifluoromethanesulfonyl)imide and 20g of lithium lanthanum zirconium tantalum oxide were added and stirred evenly. The mixture was then coated on the surface of the active material lithium metal and dried to prepare a solid electrolyte membrane with a thickness of 5μm.
[0058] Example 8
[0059] 20g of polyacrylamide and 10g of polyvinylidene fluoride were dissolved in 500mL of N,N-dimethylacetamide / acetone mixed solvent, then 10g of lithium bis(trifluoromethanesulfonyl)imide and 60g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material. After drying, a solid electrolyte membrane with a thickness of 20μm was prepared.
[0060] 78g of polyethylene oxide was dissolved in 700mL of N,N-dimethylacetamide / acetone mixed solvent, then 3g of carbon nanotubes were added, and the mixture was stirred for 60min. Then, 10g of lithium bis(trifluoromethanesulfonyl)imide and 9g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated onto the surface of the active material lithium metal. After drying, a solid electrolyte membrane with a thickness of 5μm was prepared.
[0061] Example 9
[0062] 20g of polyacrylamide and 10g of polyvinylidene fluoride were dissolved in 500mL of N,N-dimethylacetamide / acetone mixed solvent, then 10g of lithium bis(trifluoromethanesulfonyl)imide and 60g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material. After drying, a solid electrolyte membrane with a thickness of 30μm was prepared.
[0063] 78g of polyethylene oxide was dissolved in 700mL of N,N-dimethylacetamide / acetone mixed solvent, then 3g of carbon nanotubes were added, and the mixture was stirred for 60min. Then, 10g of lithium bis(trifluoromethanesulfonyl)imide and 9g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated onto the surface of the active material lithium metal. After drying, a solid electrolyte membrane with a thickness of 5μm was prepared.
[0064] Example 10
[0065] 20g of polyacrylamide and 10g of polyvinylidene fluoride were dissolved in 600mL of N,N-dimethylacetamide / acetone mixed solvent, then 10g of lithium bis(trifluoromethanesulfonyl)imide and 60g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material. After drying, a solid electrolyte membrane with a thickness of 10μm was prepared.
[0066] 78g of polyethylene oxide was dissolved in 700mL of N,N-dimethylacetamide / acetone mixed solvent, then 3g of carbon nanotubes were added, and the mixture was stirred for 60min. Then, 10g of lithium bis(trifluoromethanesulfonyl)imide and 9g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated onto the surface of the active material lithium metal. After drying, a solid electrolyte membrane with a thickness of 5μm was prepared.
[0067] In the fabrication of solid-state lithium batteries, the solid electrolyte membrane coated on the surface of the positive electrode and the solid electrolyte membrane coated on the surface of the negative electrode are in direct contact, and under certain pressure, the interface contact becomes tighter.
[0068] Comparative Example 1
[0069] 30g of polyacrylamide was dissolved in 500mL of N,N-dimethylacetamide / acetone mixed solvent, then 10g of lithium bis(trifluoromethanesulfonyl)imide and 60g of lithium lanthanum zirconium tantalum oxide were added, stirred evenly, and coated on the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material and the surface of metallic lithium. After drying, solid electrolyte membranes with a thickness of 20μm were prepared respectively.
[0070] Comparative Example 2
[0071] 78g of polyethylene oxide was dissolved in 600mL of N,N-dimethylacetamide / acetone mixed solvent, and then 10g of lithium bis(trifluoromethanesulfonyl)imide and 12g of lithium lanthanum zirconium tantalum oxide were added. The mixture was stirred evenly and coated onto the surface of the positive electrode sheet with lithium nickel cobalt manganese oxide as the active material and the surface of metallic lithium. After drying, solid electrolyte membranes with a thickness of 10μm were prepared.
[0072] The ionic conductivity and cycle capacity retention of solid-state lithium batteries fabricated using the solid electrolyte membranes obtained in the above embodiments and comparative examples are shown in the table below.
[0073] Ionic conductivity and cycling capacity retention
[0074] <![CDATA[Ionic conductivity at 25 °C (*10 -4 S / cm)]]> 100-week cycle capacity retention Example 1 4.56 89.6％ Example 2 3.56 92.8％ Example 3 3.21 91.3％ Example 4 5.87 95.6％ Example 5 5.14 95.1％ Example 6 6.35 94.3％ Example 7 7.78 91.8％ Example 8 3.66 92.1％ Example 9 3.11 92.3％ Example 10 3.86 88.1％ Comparative Example 1 0.63 78.2％ Comparative Example 2 0.21 71.7％
[0075] As shown in the table above, the present invention has a higher content of inorganic solid electrolyte in the solid electrolyte membrane coated on the surface of the positive electrode than that of polymer solid electrolyte, which effectively improves the ionic conductivity and thermal stability. The present invention also has a higher content of polymer solid electrolyte in the conductive solid electrolyte membrane coated on the surface of the negative electrode than that of inorganic solid electrolyte, which further improves the interfacial contact between solid electrolyte membranes and reduces the interfacial impedance. At the same time, the addition of carbon nanotube conductive agent can effectively improve the mechanical strength and thermal stability of the solid electrolyte membrane.
Claims
1. A double-layer solid electrolyte membrane for solid-state lithium batteries, characterized in that, The battery includes a solid electrolyte membrane A coated on the surface of the positive electrode and a solid electrolyte membrane B coated on the surface of the negative electrode. The solid electrolyte membrane A is composed of polymer solid electrolyte A, inorganic solid electrolyte and lithium salt, and the solid electrolyte membrane B is composed of polymer solid electrolyte B, inorganic solid electrolyte and lithium salt and conductive agent. The polymer solid electrolyte A is one or more of polyacrylamide, polyvinylidene fluoride, poly(vinylidene fluoride-hexafluoropropylene) copolymer and polyacrylonitrile, and the polymer solid electrolyte B is selected from polyethylene oxide; The inorganic solid electrolyte is one or more of the following: lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, lithium lanthanum titanium oxide, lithium oxide-alumina, lithium oxide-silicon oxide-alumina, and lithium aluminum titanium phosphate. The lithium salt is one or more of lithium bis(trifluoromethanesulfonyl)imide, lithium difluoromethanesulfonylimide, lithium hexafluorophosphate, lithium tetrafluoroborate, and lithium dioxolaneborate. The conductive agent is one or more of graphene, carbon nanotubes, conductive fibers, conductive graphite, and conductive carbon black. The weight ratio of the polymer solid electrolyte A, the inorganic solid electrolyte, and the lithium salt is 20~50:30~70:1~20, and the weight ratio of the polymer solid electrolyte B, the inorganic solid electrolyte, the lithium salt, and the conductive agent is 6~18:1~4:1~4:0.1~1. The thickness of the solid electrolyte membrane A is 10~50μm, and the thickness of the solid electrolyte membrane B is 2~10μm.
2. A method for preparing a double-layer solid electrolyte membrane as described in claim 1, characterized in that, Includes the following steps: Step 1: Preparation of solid electrolyte membrane A: Dissolve polymer solid electrolyte A in a mixed solvent of N,N-dimethylacetamide and acetone, then add lithium salt and inorganic solid electrolyte, stir evenly, coat it on the surface of the prepared positive electrode, and dry it to obtain solid electrolyte membrane A. Step 2: Preparation of solid electrolyte membrane B: Dissolve polymer solid electrolyte B in a mixed solvent of N,N-dimethylacetamide and acetone, then add a conductive agent and continue stirring for 30-90 minutes. Then add lithium salt and inorganic solid electrolyte, stir evenly, coat the mixture onto the surface of the prepared negative electrode sheet, and dry to obtain solid electrolyte membrane B.
3. The method for preparing a double-layer solid electrolyte membrane according to claim 2, characterized in that, The active material of the positive electrode in step one is selected from one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide, and lithium manganese oxide. The active material of the negative electrode in step two is selected from one or more of lithium metal, graphite, and silicon negative electrode.