Composite solid electrolyte membrane, preparation method thereof and all-solid-state sodium ion battery

Abstract

The invention relates to the technical field of secondary batteries, in particular to a composite solid electrolyte membrane, a preparation method thereof and an all-solid-state sodium ion battery. The composite solid-state electrolyte membrane comprises a niobium-doped oxide solid-state electrolyte layer and a polymer solid-state electrolyte layer containing an inorganic metal oxide, the niobium-doped oxide solid-state electrolyte layer and the polymer solid-state electrolyte layer have a certain thickness ratio, and the composite solid-state electrolyte membrane has good flexibility, conductivity and stability through the synergistic effect of the niobium-doped oxide solid-state electrolyte layer and the polymer solid-state electrolyte layer; and the rate capability, the cycling stability and the safety of the all-solid-state sodium-ion battery can be improved.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, specifically to a composite solid electrolyte membrane and its preparation method, and an all-solid-state sodium-ion battery. Background Technology

[0002] With the increasing severity of environmental problems such as global warming caused by fossil fuels, the development of clean and renewable energy storage and conversion devices is urgently needed. Compared with traditional lithium-ion batteries, sodium-ion batteries have advantages such as low cost, abundant raw materials, and stable cycle life, and have broad application prospects in technologies such as large-scale energy storage.

[0003] Currently, mainstream sodium-ion batteries use organic liquid electrolyte systems, which pose safety issues such as leakage and thermal runaway. Therefore, developing all-solid-state sodium-ion batteries not only promises to completely eliminate safety hazards during use but also further improves the performance of sodium-ion batteries. Solid-state electrolytes, as a key component of solid-state batteries, have a significant impact on battery safety, cycle stability, and rate performance. Solid-state electrolytes are generally classified into oxide solid-state electrolytes, polymer solid-state electrolytes, sulfide solid-state electrolytes, and halide solid-state electrolytes. Oxide solid-state electrolytes have high ionic conductivity but are brittle and have poor interfacial contact with the positive and negative electrodes. Polymer solid-state electrolytes are flexible, simple to process, and have good interfacial wetting properties with the positive and negative electrodes, but their ionic conductivity at room temperature is low, resulting in poor electrochemical performance. Sulfide and halide solid-state electrolytes have high ionic conductivity but are sensitive to air and moisture and are unstable.

[0004] Therefore, how to improve the problems of poor interfacial contact and poor conductivity of solid electrolytes, and thus further improve the safety and charge / discharge performance of all-solid-state sodium-ion batteries, is an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and provide a composite solid electrolyte membrane, its preparation method, and an all-solid-state sodium-ion battery.

[0006] To achieve the above objectives, the present invention provides a composite solid electrolyte membrane comprising a first solid electrolyte layer and a second solid electrolyte layer, wherein the thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:0.3-0.8, the first solid electrolyte layer comprises a niobium-doped oxide solid electrolyte, and the second solid electrolyte layer comprises a polymer solid electrolyte containing an inorganic metal oxide, wherein the inorganic metal oxide does not contain Na.

[0007] A second aspect of the present invention provides a method for preparing the above-mentioned composite solid electrolyte membrane, the method comprising:

[0008] (1) A first slurry is coated into a film to obtain the first solid electrolyte layer, wherein the first slurry includes the niobium-doped oxide solid electrolyte and a first binder;

[0009] (2) The second slurry is coated on the first solid electrolyte membrane to form the second solid electrolyte layer, thereby obtaining the composite solid electrolyte membrane. The second slurry includes the polymer solid electrolyte containing inorganic metal oxide and the second binder.

[0010] A third aspect of the present invention provides an all-solid-state sodium-ion battery, the all-solid-state sodium-ion battery comprising the above-described composite solid electrolyte membrane.

[0011] This invention combines a niobium-doped oxide solid electrolyte layer with a polymer solid electrolyte layer containing inorganic metal oxides to form a composite solid electrolyte membrane. By adjusting the thickness of both layers and utilizing their synergistic effect, it achieves a balance between mechanical strength and flexibility while also improving ionic conductivity and interfacial contact performance. This composite solid electrolyte membrane exhibits high conductivity and stability, and good compatibility with both positive and negative electrodes. When used in all-solid-state sodium-ion batteries, it significantly improves rate performance, cycle stability, and safety. Furthermore, its process is simple and suitable for large-scale production. Attached Figure Description

[0012] Figure 1 The graph shows the cycle performance of the all-solid-state sodium-ion battery prepared in Example 1. Detailed Implementation

[0013] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0014] The present invention provides a composite solid electrolyte membrane, which includes a first solid electrolyte layer and a second solid electrolyte layer, wherein the thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:0.3-0.8, the first solid electrolyte layer includes a niobium-doped oxide solid electrolyte, and the second solid electrolyte layer includes a polymer solid electrolyte containing an inorganic metal oxide, wherein the inorganic metal oxide does not contain Na.

[0015] According to the present invention, a niobium-doped oxide solid electrolyte layer and a polymer solid electrolyte layer containing inorganic metal oxides are combined, and the thicknesses of the two layers are adjusted. Utilizing the synergistic effect between the two, the resulting composite solid electrolyte membrane can effectively balance electrochemical performance and flexibility. To further improve the ionic conductivity and interfacial contact performance of the composite solid electrolyte membrane, preferably, the thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:0.4-0.6, for example, values ​​such as 1:0.4, 1:0.45, 1:0.5, and 1:0.6, or any range thereof. Preferably, the thickness of the first solid electrolyte layer is 3-30 μm, more preferably 3-15 μm, for example, values ​​such as 5 μm, 8 μm, 12 μm, and 15 μm, or any range thereof. Preferably, the thickness of the second solid electrolyte layer is 1-25 μm, more preferably 1-10 μm, for example, values ​​such as 1 μm, 3 μm, 6 μm, and 9 μm, or any range thereof.

[0016] According to the present invention, in order to enable the first solid electrolyte layer to better cooperate with the second solid electrolyte layer, thereby improving ion migration rate and conductivity, preferably, the niobium-doped oxide solid electrolyte is Na. 1+x-y Zr2Nb y Si x P 3-x O 12 And x is 0-3, preferably 2-2.5, for example, it can be 2, 2.2, 2.4 and 2.5 and any other value between them; y is 0.1-2, preferably 0.5-1, for example, it can be 0.5, 0.6, 0.9 and 1 and any other value between them.

[0017] According to the present invention, in order to reduce the charge transport path and provide a larger interfacial contact area, thereby improving the energy density of the solid-state sodium-ion battery, the particle size of the niobium-doped oxide solid electrolyte can be adjusted to match the porosity of the active material. Preferably, the average particle size of the niobium-doped oxide solid electrolyte is 0.5-2 μm, more preferably 0.5-1 μm, for example, it can be a value of 0.5 μm, 0.7 μm, 0.9 μm and 1 μm, or any value between these values.

[0018] According to the present invention, in order to promote the interaction between the second solid electrolyte layer and the first solid electrolyte layer, thereby improving the stability of the composite solid electrolyte membrane and its compatibility with the positive and negative electrodes, preferably, in the polymer solid electrolyte containing inorganic metal oxides, the polymer solid electrolyte is selected from one or more of polyethylene oxide, polyvinyl chloride, polyacrylonitrile, polymethyl methacrylate, polycarbonate, polyvinylidene fluoride, and polyethylene, and more preferably one or more of polyethylene oxide, polyvinyl chloride, polyacrylonitrile, and polymethyl methacrylate. Preferably, the inorganic metal oxide is selected from one or more of TiO2, SiO2, Al2O3, ZnO2, MgO, and ZrO2, and more preferably one or more of TiO2, SiO2, and Al2O3. Preferably, the weight ratio of the inorganic metal oxide to the polymer solid electrolyte is 1:40-1000, more preferably 1:60-200, for example, it can be 1:60, 1:100, 1:150, and 1:200, or any range between these values.

[0019] According to the present invention, the inorganic metal oxide can enhance the conductivity and structural stability between the first solid electrolyte layer and the second solid electrolyte layer. In order to better cooperate with the first solid electrolyte layer and improve the carrier transport rate, the average particle size of the inorganic metal oxide is preferably 0.2-2 μm, more preferably 0.2-0.8 μm, for example, it can be 0.2 μm, 0.4 μm, 0.7 μm and 0.8 μm and any value between them.

[0020] A second aspect of the present invention provides a method for preparing the above-mentioned composite solid electrolyte membrane, the method comprising:

[0021] (1) A first slurry is coated into a film to obtain the first solid electrolyte layer, wherein the first slurry includes the niobium-doped oxide solid electrolyte and a first binder;

[0022] (2) The second slurry is coated on the first solid electrolyte membrane to form the second solid electrolyte layer, thereby obtaining the composite solid electrolyte membrane. The second slurry includes the polymer solid electrolyte containing inorganic metal oxide and the second binder.

[0023] According to the present invention, in step (1) above, by mixing the niobium-doped oxide solid electrolyte with the first binder, the first slurry can be obtained and coated into a film to obtain the first solid electrolyte layer. To facilitate film formation and obtain a better-quality first solid electrolyte layer, the first binder can be selected. Preferably, the first binder is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, sodium carboxymethyl cellulose, and gelatin, and more preferably from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polytetrafluoroethylene. Preferably, the weight ratio of the first binder to the niobium-doped oxide solid electrolyte is 1:10-1000, more preferably 1:20-200, and for example, it can be 1:30, 1:50, 1:100, 1:160, and 1:200, or any range thereof.

[0024] According to the present invention, in step (1) above, in order to make the niobium-doped oxide solid electrolyte and the first binder more fully contact and more uniformly mix, the first slurry may further include a first solvent. To obtain a first slurry with better properties, the first solvent and its amount can be selected. Preferably, the first solvent is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, toluene, acetone, and pyridine, and more preferably from one or more of N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran. Preferably, relative to 1g of the niobium-doped oxide solid electrolyte, the amount of the first solvent is 2-7mL, preferably 2-4.5mL, for example, values ​​such as 2mL, 3mL, 3.8mL, and 4.5mL, and any range between these values.

[0025] The niobium-doped oxide solid electrolyte of the second aspect of the present invention can be selected and preferred from the niobium-doped oxide solid electrolytes described above, and will not be repeated here.

[0026] According to the present invention, in step (1) above, the niobium-doped oxide solid electrolyte can be prepared by the following method, for example, the method may include: subjecting the raw materials of the niobium-doped oxide solid electrolyte to a contact reaction, followed by calcination treatment to obtain the niobium-doped oxide solid electrolyte. The niobium-doped oxide solid electrolyte is Na as described above. 1+x-y Zr2Nb y Si x P 3-x O 12In this case, the raw materials for the niobium-doped oxide solid electrolyte may include one or more of the following: sodium source (e.g., Na₂CO₃), zirconium source (e.g., ZrO₂), niobium source (e.g., NbO₂), silicon source (e.g., SiO₂), and phosphorus source (e.g., NH₄H₂PO₄). Preferably, the molar ratio of Na, Zr, Nb, Si, and P provided by the sodium source, zirconium source, niobium source, silicon source, and phosphorus source is 1 + xy: 2:y:x: 3-x, where x is 0-3, preferably 2-2.5, for example, values ​​such as 2, 2.2, 2.4, and 2.5, and any range thereof; and y is 0.1-2, preferably 0.5-1, for example, values ​​such as 0.6, 0.8, 0.9, and 1, and any range thereof. To achieve better contact reaction results, the contact reaction can also be carried out in the presence of a solvent. The solvent and its amount can be selected within a wide range. Preferably, the solvent can be one or more of ethanol, acetone, acetonitrile, tetrahydrofuran, N-methylpyrrolidone, and N,N-dimethylformamide, and more preferably one or more of ethanol, acetone, and acetonitrile. Preferably, the amount of solvent used in the contact reaction is 5-20 mL relative to the total weight of 1 g of the niobium-doped oxide solid electrolyte raw materials, preferably 8-14 mL, for example, 8 mL, 10 mL, 12.5 mL, and 14 mL, and any value between these values. To facilitate better contact between the above raw materials and achieve the desired particle size distribution, ball milling can be performed simultaneously with the contact reaction. Preferably, the ball milling speed is 200-800 rpm, more preferably 400-600 rpm, for example, 400 rpm, 480 rpm, 500 rpm, and 600 rpm, and any value between these values. Preferably, the ball milling time is 6-36 hours, more preferably 10-28 hours, for example, it can be 10 hours, 15 hours, 19 hours, 22 hours, and 26 hours, or any range thereof. To obtain better calcination results, improve the thermal stability of the product, and achieve the purpose of impurity removal and enrichment of active components, preferably, the calcination temperature is 400-1500℃, more preferably 600-1100℃, for example, it can be 600℃, 800℃, 960℃, and 1100℃, or any range thereof. Preferably, the calcination time is 1-12 hours, more preferably 3-6 hours, for example, it can be 3 hours, 4 hours, 5 hours, and 6 hours, or any range thereof. Preferably, the heating rate of the calcination is 1-12℃ / min, more preferably 2-8℃ / min, for example, it can be 2℃ / min, 4℃ / min, 5℃ / min, and 8℃ / min, or any range thereof. Preferably, the calcination treatment is carried out in the presence of a non-reactive gas. Preferably, the non-reactive gas is selected from nitrogen and / or argon.The starting temperature for this calcination treatment is typically 20-40℃, or it can be appropriately exceeded.

[0027] According to the present invention, in step (2) above, by mixing the polymer solid electrolyte containing inorganic metal oxides with the second binder, a second slurry can be obtained and coated onto the first solid electrolyte layer to form a film, thereby obtaining the second solid electrolyte layer, and further obtaining the composite solid electrolyte membrane. To facilitate film formation and obtain a better-formed second solid electrolyte layer, the second binder can be selected. Preferably, the second binder is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, sodium carboxymethyl cellulose, and gelatin, and more preferably from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, and polytetrafluoroethylene. Preferably, the weight ratio of the second binder to the polymer solid electrolyte containing inorganic metal oxides is 1:10-1000, more preferably 1:20-200, for example, values ​​such as 1:30, 1:50, 1:100, 1:160, and 1:200, and any range between these values.

[0028] According to the present invention, in step (2) above, in order to mix the polymer solid electrolyte containing inorganic metal oxides with the second binder more uniformly, the second slurry may further include a second solvent. To obtain a second slurry with better properties, the second solvent and its amount can be selected. Preferably, the second solvent is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, toluene, acetone, and pyridine, and more preferably from one or more of N,N-dimethylformamide, N-methylpyrrolidone, and tetrahydrofuran. Preferably, relative to 1g of the polymer solid electrolyte containing inorganic metal oxides, the amount of the second solvent is 2-7mL, preferably 2.5-4mL, for example, values ​​such as 2.5mL, 3mL, 3.5mL, and 4mL, and any range between these values.

[0029] The polymer solid electrolyte containing inorganic metal oxides in the second aspect of the present invention can be selected and preferred from the polymer solid electrolytes containing inorganic metal oxides described above, and will not be repeated here.

[0030] According to the present invention, in step (2) above, the inorganic metal oxide and the polymer solid electrolyte in the polymer solid electrolyte containing inorganic metal oxide can be mixed in advance before being mixed with the second binder, or the inorganic metal oxide, the polymer solid electrolyte and the second binder can be mixed simultaneously.

[0031] The thickness and thickness ratio of the first solid electrolyte layer and the second solid electrolyte layer in the second aspect of the present invention can be selected and preferred from the thickness and thickness ratio of the first solid electrolyte layer and the second solid electrolyte layer described above, and will not be repeated here.

[0032] A third aspect of the present invention provides an all-solid-state sodium-ion battery, the all-solid-state sodium-ion battery comprising the above-described composite solid electrolyte membrane.

[0033] This invention combines a niobium-doped oxide solid electrolyte layer with a polymer solid electrolyte layer containing inorganic metal oxides to form a composite solid electrolyte membrane. By adjusting the thickness of both layers and utilizing their synergistic effect, it achieves a balance between mechanical strength and flexibility while also improving ionic conductivity and interfacial contact performance. This composite solid electrolyte membrane exhibits high conductivity, high stability, and good compatibility with both positive and negative electrodes. When used in all-solid-state sodium-ion batteries, it can significantly improve rate performance, cycle stability, and safety.

[0034] The present invention will be described in detail below through embodiments.

[0035] In the following examples, the apparatus used is standard experimental equipment in the field, the experimental procedures employed are standard procedures in the field, and the raw materials and reagents used are commercially available. Specifically, the polyvinylidene fluoride (PVDF) grade is PVDF5130; the polyethylene oxide grade is 620; the polyvinylidene fluoride-hexafluoropropylene grade is Solef21216; the polyacrylonitrile grade is P90H; the polytetrafluoroethylene (PTFE) grade is 640XTX; the polyvinyl chloride (PVC) grade is M1000; the SP conductive carbon black grade is Super P Li; and the hard carbon grade is HCM-B2-K.

[0036] Example 1

[0037] (1) Na₂CO₃, ZrO₂, NbO₂, SiO₂, and NH₄H₂PO₄ (the molar ratio of Na, Zr, Nb, Si, and P was 2:2:1:2:1) were added to ethanol (12.5 mL of ethanol per 1 g of total solid weight) and ball-milled at 600 rpm for 20 h. The dried mixture was calcined under a nitrogen atmosphere, with the temperature increased from room temperature to 800 °C at a rate of 5 °C / min, and calcined at 800 °C for 5 h to obtain Na₂Zr₂NbSi₂PO₄ with an average particle size of 0.6 μm. 12 Polyvinylidene fluoride and Na2Zr2NbSi2PO4 12 Add N-methylpyrrolidone (relative to 1g Na2Zr2NbSi2PO4) at a weight ratio of 1:100. 12The mixture was thoroughly mixed with 2.5 mL of N-methylpyrrolidone and then coated into a 10 μm film. After drying, the first solid electrolyte layer was obtained.

[0038] (2) Polyvinylidene fluoride, TiO2 and polyethylene oxide (the average particle size of TiO2 is 0.2 μm; the weight ratio of TiO2 to polyethylene oxide is 1:100; the weight ratio of polyvinylidene fluoride to the total weight of TiO2 and polyethylene oxide is 1:100) are added to N-methylpyrrolidone (the amount of N-methylpyrrolidone is 2.5 mL relative to 1 g of polyethylene oxide containing TiO2) and mixed thoroughly. Then, a 5 μm film is coated on the first solid electrolyte layer to obtain the second solid electrolyte layer. After drying, the composite solid electrolyte membrane is obtained (the thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:0.5).

[0039] Example 2

[0040] (1) Na₂CO₃, ZrO₂, NbO₂, SiO₂, and NH₄H₂PO₄ (the molar ratio of Na, Zr, Nb, Si, and P was 3:2:0.5:2.5:0.5) were added to acetone (12.5 mL relative to 1 g of total solid weight) and ball-milled at 400 rpm for 15 h. The dried mixture was calcined under a nitrogen atmosphere, with the temperature increased from room temperature to 1100 °C at a rate of 8 °C / min, and calcined at 1100 °C for 3 h to obtain Na₃Zr₂Nb with an average particle size of 1 μm. 0.5 Si 2.5 P 0.5 O 12 Polyvinylidene fluoride-hexafluoropropylene and Na3Zr2Nb 0.5 Si 2.5 P 0.5 O 12 Add N,N-dimethylformamide (relative to 1g Na3Zr2Nb) at a weight ratio of 1:20. 0.5 Si 2.5 P 0.5 O 12 The mixture was thoroughly mixed with 2.5 mL of N,N-dimethylformamide and then coated into a 6 μm film. After drying, the first solid electrolyte layer was obtained.

[0041] (2) Polytetrafluoroethylene, SiO2 and polyacrylonitrile (the average particle size of SiO2 is 0.5 μm; the weight ratio of SiO2 to polyacrylonitrile is 1:200; the weight ratio of polytetrafluoroethylene to the total weight of SiO2 and polyacrylonitrile is 1:20) are added to tetrahydrofuran (the amount of tetrahydrofuran is 2.5 mL relative to 1 g of polyacrylonitrile containing SiO2) and mixed thoroughly. Then, a 2.4 μm film is coated on the first solid electrolyte layer to obtain the second solid electrolyte layer. After drying, the composite solid electrolyte membrane is obtained (the thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:0.4).

[0042] Example 3

[0043] (1) Na₂CO₃, ZrO₂, NbO₂, SiO₂, and NH₄H₂PO₄ (the molar ratio of Na, Zr, Nb, Si, and P was 2.5:2:0.7:2.2:0.8) were added to acetonitrile (12.5 mL relative to 1 g of total solid weight) and ball-milled at 500 rpm for 25 h. The dried mixture was calcined under a nitrogen atmosphere, with the temperature increased from room temperature to 600 °C at a rate of 2 °C / min, and calcined at 600 °C for 6 h to obtain Na with an average particle size of 0.5 μm. 2.5 Zr2Nb 0.7 Si 2.2 P 0.8 O 12 Polytetrafluoroethylene and Na 2.5 Zr2Nb 0.7 Si 2.2 P 0.8 O 12 Add N-methylpyrrolidone (relative to 1g Na) at a weight ratio of 1:200. 2.5 Zr2Nb 0.7 Si 2.2 P 0.8 O 12 The mixture was thoroughly mixed with 2.5 mL of N-methylpyrrolidone and then coated into a 15 μm film. After drying, the first solid electrolyte layer was obtained.

[0044] (2) Polyvinylidene fluoride, Al2O3 and polyvinyl chloride (the average particle size of Al2O3 is 0.8 μm; the weight ratio of Al2O3 to polyvinyl chloride is 1:60; the weight ratio of polyvinylidene fluoride to the total weight of Al2O3 and polyvinyl chloride is 1:180) are added to N-methylpyrrolidone (the amount of N-methylpyrrolidone is 2.5 mL relative to 1 g of polyvinyl chloride containing Al2O3) and mixed thoroughly. Then, a 9 μm film is coated on the first solid electrolyte layer to obtain the second solid electrolyte layer. After drying, the composite solid electrolyte membrane is obtained (the thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:0.6).

[0045] Example 4

[0046] The method is the same as in Example 1, except that the weight ratio of TiO2 to polyacrylonitrile in step (2) is 1:40.

[0047] Example 5

[0048] The method is the same as in Example 1, except that the weight ratio of TiO2 to polyacrylonitrile in step (2) is 1:600.

[0049] Example 6

[0050] The method is the same as in Example 1, except that in step (1), the molar ratio of Na, Zr, Nb, Si, and P in Na2CO3, ZrO2, NbO2, SiO2, and NH4H2PO4 is 2.8:2:0.2:2:1, and then Na is obtained. 2.8 Zr2Nb 0.2 Si2PO 12 .

[0051] Example 7

[0052] The method is the same as in Example 1, except that in step (1), the molar ratio of Na, Zr, Nb, Si, and P in Na2CO3, ZrO2, NbO2, SiO2, and NH4H2PO4 is 2.8:2:1:2.8:0.2, and then Na is obtained. 2.8 Zr2Nb1Si 2.8 P 0.2 O 12 .

[0053] Example 8

[0054] According to the method of Example 1, the difference is that the coating thickness of the first solid electrolyte layer in step (1) is 10 μm, the coating thickness of the second solid electrolyte layer in step (2) is 3 μm, and the thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:0.3.

[0055] Example 9

[0056] According to the method of Example 1, the difference is that the coating thickness of the first solid electrolyte layer in step (1) is 10 μm, the coating thickness of the second solid electrolyte layer in step (2) is 8 μm, and the thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:0.8.

[0057] Comparative Example 1

[0058] According to the method of Example 1, the difference is that the coating thickness of the first solid electrolyte layer in step (1) is 10 μm, the coating thickness of the second solid electrolyte layer in step (2) is 1 μm, and the thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:0.1.

[0059] Comparative Example 2

[0060] According to the method of Example 1, the difference is that the coating thickness of the first solid electrolyte layer in step (1) is 10 μm, the coating thickness of the second solid electrolyte layer in step (2) is 10 μm, and the thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:1.

[0061] Comparative Example 3

[0062] The method of Example 1 differs except that step (1) involves mixing polyvinylidene fluoride with Na, which has an average particle size of 0.6 μm. 6.4 La3Zr 1.4 Ta 0.6 O 12 Add N-methylpyrrolidone (relative to 1g Na) at a weight ratio of 1:100. 6.4 La3Zr 1.4 Ta 0.6 O 12 The mixture was thoroughly mixed with 2.5 mL of N-methylpyrrolidone and then coated into a 10 μm film to obtain the first solid electrolyte layer. Step (2) is the same as in Example 1.

[0063] Comparative Example 4

[0064] The method is the same as in Example 1, except that step (2) is as follows: polyvinylidene fluoride and polyethylene oxide (the weight ratio of polyvinylidene fluoride to polyethylene oxide is 1:100) are added to N-methylpyrrolidone (the amount of N-methylpyrrolidone is 2.5 mL relative to 1 g of polyethylene oxide) and mixed thoroughly. Then, a 5 μm film is coated on the first solid electrolyte layer to obtain the second solid electrolyte layer. Step (1) is the same as in Example 1.

[0065] Comparative Example 5

[0066] According to the method of Example 1, the difference is that after step (1) is completed, step (2) is not performed, and the first solid electrolyte layer obtained is directly used as a single-layer solid electrolyte membrane for later use.

[0067] Comparative Example 6

[0068] The method according to Example 1 differs in that step (1) is omitted, and in step (2), the second solid electrolyte layer obtained after coating is directly used as a single-layer solid electrolyte membrane for later use.

[0069] Test case

[0070] The composite solid electrolyte membranes or single-layer solid electrolyte membranes obtained in Examples 1-9 and Comparative Examples 1-6 were respectively wound with positive and negative electrodes to prepare all-solid-state sodium-ion batteries SIB606691-2.5Ah, and then tested.

[0071] Among them, the positive electrode is prepared by layering the metal oxide NaNi. 1 / 3 Mn 1 / 3 Fe 1 / 3 O2, SP conductive carbon black, and polyvinylidene fluoride were mixed in a weight ratio of 95:2:3 with N-methylpyrrolidone (relative to 1 g of layered metal oxide NaNi). 1 / 3 Mn 1 / 3 Fe 1 / 3 The positive electrode was prepared by mixing O2 (1 mL of N-methylpyrrolidone) and coating it onto aluminum foil (100 μm thick). The mixture was then fabricated using a sheet-forming process. The negative electrode was prepared by mixing hard carbon, SP conductive carbon black, and polyvinylidene fluoride in a weight ratio of 95:2:3 with N-methylpyrrolidone (1.5 mL of N-methylpyrrolidone relative to 1 g of hard carbon). This mixture was then coated onto copper foil (50 μm thick) and fabricated using a sheet-forming process.

[0072] The testing method is as follows:

[0073] The all-solid-state sodium-ion batteries prepared in Examples 1-9 and Comparative Examples 1-6 were tested at 23±5℃ for 1000 cycles of 1C charge-discharge. The capacity retention rate after 1000 cycles is shown in Table 1.

[0074] Table 1

[0075]

[0076] As can be seen from Table 1, the cycle performance of Examples 1-9 using the technical solution of the present invention is better than that of Comparative Examples 1-6. Their capacity retention rate after 1000 cycles can reach more than 93%, and in particular, some preferred embodiments can reach more than 97%.

[0077] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A composite solid electrolyte membrane, characterized in that, The composite solid electrolyte membrane includes a first solid electrolyte layer and a second solid electrolyte layer, with a thickness ratio of 1:0.3-0.8 between the first solid electrolyte layer and the second solid electrolyte layer. The first solid electrolyte layer includes a niobium-doped oxide solid electrolyte, and the second solid electrolyte layer includes a polymer solid electrolyte containing an inorganic metal oxide, wherein the inorganic metal oxide does not contain Na.

2. The composite solid electrolyte membrane according to claim 1, wherein, The thickness ratio of the first solid electrolyte layer to the second solid electrolyte layer is 1:0.4-0.6; Preferably, the thickness of the first solid electrolyte layer is 3-30 μm, and more preferably 3-15 μm; Preferably, the thickness of the second solid electrolyte layer is 1-25 μm, and more preferably 1-10 μm.

3. The composite solid electrolyte membrane according to claim 1 or 2, wherein, The niobium-doped oxide solid electrolyte is Na 1+x-y Zr2Nb y Si x P 3-x O 12 And x is 0-3, preferably 2-2.5; y is 0.1-2, preferably 0.5-1; Preferably, the average particle size of the niobium-doped oxide solid electrolyte is 0.5-2 μm, more preferably 0.5-1 μm.

4. The composite solid electrolyte membrane according to any one of claims 1-3, wherein, The polymer solid electrolyte is selected from one or more of polyethylene oxide, polyvinyl chloride, polyacrylonitrile, polymethyl methacrylate, polycarbonate, polyvinylidene fluoride and polyethylene, preferably one or more of polyethylene oxide, polyvinyl chloride, polyacrylonitrile and polymethyl methacrylate; Preferably, the inorganic metal oxide is selected from one or more of TiO2, SiO2, Al2O3, ZnO2, MgO and ZrO2, and more preferably from one or more of TiO2, SiO2 and Al2O3; Preferably, the inorganic metal oxide has an average particle size of 0.2-2 μm, more preferably 0.2-0.8 μm; Preferably, the weight ratio of the inorganic metal oxide to the polymer solid electrolyte is 1:40-1000, more preferably 1:60-200.

5. A method for preparing a composite solid electrolyte membrane according to any one of claims 1-4, characterized in that, The method includes: (1) A first slurry is coated into a film to obtain the first solid electrolyte layer, wherein the first slurry includes the niobium-doped oxide solid electrolyte and the first binder; (2) The second slurry is coated on the first solid electrolyte membrane to form the second solid electrolyte layer, thereby obtaining the composite solid electrolyte membrane. The second slurry includes the polymer solid electrolyte containing inorganic metal oxide and the second binder.

6. The method according to claim 5, wherein, The weight ratio of the first binder to the niobium-doped oxide solid electrolyte is 1:10-1000, preferably 1:20-200.

7. The method according to claim 5 or 6, wherein, The first slurry also includes a first solvent; Preferably, the first solvent is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, toluene, acetone and pyridine, and more preferably from one or more of N,N-dimethylformamide, N-methylpyrrolidone and tetrahydrofuran; Preferably, the amount of the first solvent used is 2-7 mL, more preferably 2.5-4 mL, relative to 1 g of the niobium-doped oxide solid electrolyte.

8. The method according to any one of claims 5-7, wherein, The weight ratio of the second binder to the polymer solid electrolyte containing inorganic metal oxides is 1:10-1000, preferably 1:20-200.

9. The method according to any one of claims 5-7, wherein, The second slurry also includes a second solvent; Preferably, the second solvent is selected from one or more of N,N-dimethylformamide, N-methylpyrrolidone, tetrahydrofuran, dimethyl sulfoxide, toluene, acetone and pyridine, and more preferably from one or more of N,N-dimethylformamide, N-methylpyrrolidone and tetrahydrofuran; Preferably, the amount of the second solvent used is 2-7 mL, more preferably 2.5-4 mL, relative to 1 g of the polymer solid electrolyte containing inorganic metal oxides.

10. A fully solid-state sodium-ion battery, characterized in that, The all-solid-state sodium-ion battery includes the composite solid-state electrolyte membrane as described in any one of claims 1-4.

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