Solid electrolytes, solid-state batteries and electrical devices

Abstract

A solid electrolyte including a first solid electrolyte layer and a second solid electrolyte layer, wherein the first solid electrolyte layer includes a first sulfide solid electrolyte and the second solid electrolyte layer includes a phosphide solid electrolyte.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This disclosure claims priority to and benefit of Chinese Patent Application No. 202211742332.8, entitled "Solid Electrolyte, Solid-State Battery and Electrical Device," filed on December 30, 2022. The entire contents of the above-referenced application are incorporated herein by reference.

[0002] Technical Field The present disclosure relates to the field of battery technology, particularly solid electrolytes, solid-state batteries, and electrical devices. [Background technology]

[0003] The development of sulfide-based all-solid-state batteries has attracted widespread attention in industry because sulfide solid electrolytes have the characteristics of high ionic conductivity, low grain boundary impedance, and non-flammability. However, sulfide solid electrolytes have a high reduction potential (approximately 1.7 V), which causes problems with interfacial reactions at the anode side, resulting in poor ion permeability of the formed interfacial layer. As a result, the interfacial resistance increases, ultimately leading to battery failure. Summary of the Invention [Problem to be solved by the invention]

[0004] In this regard, the present disclosure provides a solid electrolyte, which, when used in a solid-state battery, can provide a low ionic impedance at the interface between the solid electrolyte and the negative electrode, thereby optimizing the performance of the solid-state battery. [Means for solving the problem]

[0005] Specifically, a first aspect of the present disclosure provides a solid electrolyte including a first solid electrolyte layer and a second solid electrolyte layer, the first solid electrolyte layer including a first sulfide solid electrolyte, and the second solid electrolyte layer including a phosphide solid electrolyte.

[0006] When the solid electrolyte of the present disclosure is used in a solid-state battery and a second solid electrolyte layer is disposed adjacent to a negative electrode, the interfacial layer between the solid electrolyte and the negative electrode can contain many components with high ionic conductivity, thereby effectively reducing the interfacial impedance and keeping the overall electronic conductivity of the solid electrolyte low, thereby achieving the goal of optimizing the performance of the solid-state battery.

[0007] According to a second aspect, the present disclosure provides a solid-state battery including a positive electrode, a negative electrode, and the solid electrolyte according to the first aspect. The solid electrolyte is disposed between the positive electrode and the negative electrode. A first solid electrolyte layer is disposed between the positive electrode and the second solid electrolyte layer. The second solid electrolyte layer is disposed between the first solid electrolyte layer and the negative electrode.

[0008] According to a third aspect, the present disclosure provides an electrical device including a solid-state battery according to the second aspect.

[0009] Detailed Description The technical solutions in the embodiments of the present disclosure are clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. It is clear that the described embodiments are only some, not all, of the embodiments of the present disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0010] The development of sulfide-based all-solid-state batteries has attracted widespread attention in the industry because sulfide solid electrolytes have the characteristics of high ionic conductivity, low grain boundary impedance, and non-flammability. However, the stable electrochemical window of sulfide solid electrolytes is narrow. On the negative electrode side, the high reduction potential of sulfide solid electrolytes (approximately 1.7 V) poses the problem of interfacial reactions. In particular, when sulfide solid electrolytes are used with negative electrodes with high energy densities, such as lithium metal or some lithium alloys, the ionic impedance at the interface rises sharply. To reduce the ionic impedance at the interface with the negative electrode and optimize the performance of solid-state batteries, the present disclosure provides a solid electrolyte comprising a first solid electrolyte layer and a second solid electrolyte layer. The first solid electrolyte layer comprises a first sulfide solid electrolyte. The second solid electrolyte layer comprises a phosphide solid electrolyte. When the solid electrolyte provided in the present disclosure is used in a solid-state battery, the solid electrolyte can be disposed between the positive electrode and the negative electrode. The first solid electrolyte layer is disposed adjacent to the positive electrode. The second solid electrolyte layer is disposed adjacent to the negative electrode. Because the second solid electrolyte layer contains a phosphide solid electrolyte with a low interfacial potential, the stability of the interface between the solid electrolyte and the negative electrode is improved. Furthermore, the phosphide solid electrolyte in the second solid electrolyte layer can contain a higher proportion of a component with high ionic conductivity (e.g., Li3P) in the interfacial layer between the solid electrolyte and the negative electrode, effectively reducing the ionic impedance at the interface between the solid electrolyte and the negative electrode. Furthermore, the first sulfide solid electrolyte in the first solid electrolyte layer can maintain the electronic conductivity of the solid electrolyte itself at a low level. Therefore, the solid electrolyte of the present disclosure effectively reduces the ionic impedance at the interface with the solid electrolyte-coated electrode and maintains the electronic conductivity of the solid electrolyte at a low level, thereby optimizing the charge / discharge and cycle performance of the solid-state battery.

[0011] In this embodiment of the present disclosure, the first sulfide solid electrolyte may be a known sulfide solid electrolyte. For example, the first sulfide solid electrolyte may be selected from, but is not limited to, one or more of a fast-ion conductor type sulfide solid electrolyte, an argyrodite type sulfide solid electrolyte, a glass-ceramic type sulfide solid electrolyte, a thiophosphate type sulfide solid electrolyte, and a thiosilicate type sulfide solid electrolyte. For example, a fast-ion conductor type sulfide solid electrolyte may be Li3PS4, Li 10 GeP2S 12 , and Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The argyrodite-type sulfide solid electrolyte may be one or more of the following: Li 6-z PS 5-z Cl 1+z (0≦z≦1), etc. The glass ceramic type sulfide solid electrolyte may be LiI-(70Li2S-30P2S5), etc. The thiophosphate type sulfide solid electrolyte may be Li7P3S 11 , Li4PS4I, and Li7P2S8I. The thiosilicate-based sulfide solid electrolyte may be Li2SiS3, etc. The phosphide solid electrolyte may be a phosphorus-containing compound having a specific ionic conductivity, for example, a room temperature ionic conductivity of 0.01 mS / cm or greater.

[0012] In some embodiments of the present disclosure, the phosphide solid electrolyte contains phosphorus with a valence of −3. The valence of the phosphorus in the phosphide solid electrolyte may be −3 entirely or partially. When the phosphide solid electrolyte contains phosphorus with a valence of −3, the conductivity of the interface layer between the solid electrolyte and the negative electrode can be improved, thereby further improving the charge / discharge performance and cycle performance of the solid-state battery.

[0013] In some embodiments of the present disclosure, the reduction potential of the phosphide solid electrolyte is 0 V to 1.2 V. When the reduction potential of the phosphide solid electrolyte is within this range, the electrochemical stability of the solid electrolyte to the negative electrode is higher, side reactions at the interface are minimal, and the interfacial layer formed is thinner, which can further improve the stability of the interface between the solid electrolyte and the negative electrode, reduce the ionic impedance at the interface, improve the charge / discharge performance of the solid-state battery, and extend the cycle life of the solid-state battery.

[0014] In some embodiments of the present disclosure, the phosphide solid electrolyte is Li 3x-3 AP x and Li 3y-4 BP y The element P has a valence of -3. The element A is selected from at least one of Al, Ga, and In. The element B is selected from at least one of Si, Ge, and Sn. x is an integer of 2 to 4. y is an integer of 2 to 6.

[0015] In some embodiments of the present disclosure, the phosphide solid electrolyte is selected from the group consisting of Li9AlP4, Li9GaP4, Li9InP4, Li3AlP2, Li3GaP2, Li3InP2, Li8SiP4, Li8GeP4, Li8SnP4, Li2SiP2, Li2GeP2, Li2SnP2, Li 14 SiP6, and Li 14 In some embodiments of the present disclosure, the phosphide solid electrolyte comprises one or more of Li9AlP4, Li9GaP4, Li 14 SiP6, and Li 14 The room temperature ionic conductivity of these phosphide solid electrolytes is on the order of mS / cm, which helps to further improve the conductivity of the solid electrolyte and optimize the charge / discharge and cycling performance of the battery.

[0016] In some embodiments of the present disclosure, the first sulfide solid electrolyte is Li3PS4, Li 10 GeP2S 12 (LGPS), Li 9.54 Si1.74 P 1.44 S 11.7 Cl 0.3 , Li 6-z PS 5-z Cl 1+z , LiI-(70Li2S-30P2S5), Li7P3S 11 , Li4PS4I, Li7P2S8I, and Li2SiS3. 6-z PS 5-z Cl 1+z where the value of z is in the range of 0≦z≦1. These sulfide solid electrolytes have high ionic conductivity and low electronic conductivity, and are compatible with phosphide solid electrolytes, which helps to improve the electrochemical performance of solid-state batteries.

[0017] In some embodiments of the present disclosure, the total mass of the first solid electrolyte layer is used as a reference, and the content of the first sulfide solid electrolyte in the first solid electrolyte layer is 90% by mass to 99.9% by mass. For example, the content of the first sulfide solid electrolyte in the first solid electrolyte layer may be 90%, 92%, 94%, 96%, 98%, or 99.9% by mass. When the content of the first sulfide solid electrolyte in the first solid electrolyte layer is within the above range, the ion permeability of the solid electrolyte can be improved, the structural stability of the solid electrolyte can be ensured, and the charge / discharge performance and cycle performance of the solid battery can be improved.

[0018] In some embodiments of the present disclosure, the total mass of the second solid electrolyte layer is used as a standard, and the content of the phosphide solid electrolyte in the second solid electrolyte layer is 90% by mass to 99.9% by mass. When the content of the phosphide solid electrolyte in the second solid electrolyte layer is within this range, the ionic impedance at the interface between the solid electrolyte and the negative electrode can be further reduced, thereby optimizing the performance of the battery.

[0019] In some embodiments of the present disclosure, the second solid electrolyte layer further includes a second sulfide solid electrolyte. Specifically, the second solid electrolyte layer includes a second sulfide solid electrolyte and a phosphide solid electrolyte. The first sulfide solid electrolyte and the second sulfide solid electrolyte may be the same or different. The first sulfide solid electrolyte and the second sulfide solid electrolyte may independently be known sulfide solid electrolytes. For example, the second sulfide solid electrolyte may be selected from, but is not limited to, one or more of a fast-ion conductor sulfide solid electrolyte, an argyrodite-type sulfide solid electrolyte, a glass-ceramic-type sulfide solid electrolyte, a thiophosphate-based sulfide solid electrolyte, and a thiosilicate-based sulfide solid electrolyte. Specifically, the fast-ion conductor sulfide solid electrolyte may be Li3PS4, LGPS, and Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 The argyrodite-type sulfide solid electrolyte may be one or more of the following: Li 6-z PS 5-z Cl 1+z (wherein the value of z is in the range of 0≦z≦1) and the like. The glass-ceramic sulfide solid electrolyte may be LiI-(70Li2S-30P2S5) and the like. The thiophosphate-based sulfide solid electrolyte may be Li7P3S 11 , Li4PS4I, and Li7P2S8I. The thiosilicate-based sulfide solid electrolyte may be Li2SiS3, etc.

[0020] In some embodiments of the present disclosure, the total mass of the second solid electrolyte layer is used as a standard, and the content of the second sulfide solid electrolyte and the phosphide solid electrolyte in the second solid electrolyte layer is 90% by mass to 99.9% by mass. In other words, the sum of the content of the second sulfide solid electrolyte and the content of the phosphide solid electrolyte in the second solid electrolyte layer is 90% by mass to 99.9% by mass.

[0021] In some embodiments of the present disclosure, the first solid electrolyte layer and the second solid electrolyte layer each further include a binder. The total mass of the first solid electrolyte layer is used as a reference, and the binder content in the first solid electrolyte layer is 0.1% by mass to 10% by mass. The total mass of the second solid electrolyte layer is used as a reference, and the binder content in the second solid electrolyte layer is 0.1% by mass to 10% by mass. The total mass of the solid electrolyte is used as a reference, and the binder content in the solid electrolyte is 0.1% by mass to 10% by mass. The binder can improve the structural stability of the solid electrolyte. The binder in the solid electrolyte may be selected from one or more of polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile butadiene rubber (NBR), polyacrylate, poly(acrylic acid) (PAA), alkyl cellulose, and polyethylene oxide (PEO).

[0022] In some embodiments of the present disclosure, the total mass of the second sulfide solid electrolyte and the phosphide solid electrolyte in the second solid electrolyte layer is used as a reference, and the content of the second sulfide solid electrolyte in the second solid electrolyte layer is 10% by mass to 95% by mass, and the content of the phosphide solid electrolyte is 5% by mass to 90% by mass. Specifically, of the total mass of the second sulfide solid electrolyte and the phosphide solid electrolyte in the second solid electrolyte layer, the mass percentage of the second sulfide solid electrolyte is 10% by mass to 95% by mass, and the mass percentage of the phosphide solid electrolyte is 5% by mass to 90% by mass. For example, the content of the second sulfide solid electrolyte in the second solid electrolyte layer may be 10% by mass, 20% by mass, 30% by mass, 40% by mass, 50% by mass, 60% by mass, 70% by mass, 80% by mass, 90% by mass, or 95% by mass. The content of the phosphide solid electrolyte may be 5 mass%, 10 mass%, 20 mass%, 30 mass%, 40 mass%, 50 mass%, 60 mass%, 70 mass%, 80 mass%, or 90 mass%. When the content range is satisfied, the solid electrolyte can improve the stability of the interface between the solid electrolyte and the negative electrode and reduce the impedance of the interface layer between the solid electrolyte and the negative electrode while maintaining low electronic conductivity, thereby increasing the capacity of the solid-state battery and extending the cycle life of the solid-state battery.

[0023] In some embodiments of the present disclosure, the total mass of the second sulfide solid electrolyte and the phosphide solid electrolyte in the second solid electrolyte layer is used as a standard, and the content of the second sulfide solid electrolyte in the second solid electrolyte layer is 30% by mass to 70% by mass, and the content of the phosphide solid electrolyte is 30% by mass to 70% by mass. When these content ranges are satisfied, the solid electrolyte can have both low electronic conductivity and low impedance at the interface with the negative electrode, thereby increasing the capacity of the solid battery and extending the cycle life of the solid battery.

[0024] In some embodiments of the present disclosure, the thickness of the first solid electrolyte layer is 15 μm to 200 μm, and the thickness of the second solid electrolyte layer is 1 μm to 15 μm. For example, the thickness of the first solid electrolyte layer may be 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, or 200 μm. The thickness of the second solid electrolyte layer may be 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, or 15 μm. When the above thickness ranges are satisfied, the solid electrolyte has good interfacial stability with the negative electrode and can maintain low electronic conductivity, thereby improving the electrochemical performance of the solid-state battery.

[0025] In some embodiments of the present disclosure, the thickness of the first solid electrolyte layer is 15 μm to 50 μm, and the thickness of the second solid electrolyte layer is 3 μm to 7 μm. When these thickness ranges are satisfied, the stability of the interface between the solid electrolyte and the negative electrode can be further improved and low electronic conductivity can be maintained, thereby improving the electrochemical performance of the solid-state battery.

[0026] In some embodiments of the present disclosure, the first sulfide solid electrolyte has a D50 of 1 μm to 10 μm, the second sulfide solid electrolyte has a D50 of 0.5 μm to 4 μm, and the phosphide solid electrolyte has a D50 of 0.5 μm to 4 μm. For example, the first sulfide solid electrolyte may have a D50 of 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, the second sulfide solid electrolyte may have a D50 of 0.5 μm, 1 μm, 2 μm, 3 μm, or 4 μm, and the phosphide solid electrolyte may have a D50 of 0.5 μm, 1 μm, 2 μm, 3 μm, or 4 μm. When the D50 of the first sulfide solid electrolyte, the D50 of the second sulfide solid electrolyte, and the D50 of the phosphide solid electrolyte are adjusted to be within the aforementioned ranges, the density of the solid electrolyte can be improved, and the ionic conductivity of the solid electrolyte can be improved.

[0027] In some embodiments of the present disclosure, the first sulfide solid electrolyte has a D50 of 2 μm to 5 μm, the second sulfide solid electrolyte has a D50 of 0.7 μm to 2 μm, and the phosphide solid electrolyte has a D50 of 0.7 μm to 2 μm. When the D50s of the first sulfide solid electrolyte, the second sulfide solid electrolyte, and the phosphide solid electrolyte are adjusted to be within the aforementioned ranges, the denseness and ionic conductivity of the solid electrolyte can be further improved.

[0028] The present disclosure further provides a solid-state battery. The solid-state battery includes a positive electrode, a negative electrode, and the aforementioned solid electrolyte. The solid electrolyte is disposed between the positive electrode and the negative electrode. A first solid electrolyte layer is disposed between the positive electrode and the second solid electrolyte layer. The second solid electrolyte layer is disposed between the first solid electrolyte layer and the negative electrode.

[0029] In the solid-state battery of the present disclosure, the phosphide solid electrolyte has a lower reduction potential than the sulfide solid electrolyte. Therefore, by disposing the second solid electrolyte layer containing the phosphide solid electrolyte closer to the negative electrode, the electrochemical stability of the solid electrolyte relative to the negative electrode can be improved, side reactions at the interface between the solid electrolyte and the negative electrode can be minimized, and the formed interface can be made thinner, effectively reducing the ionic impedance at the interface and optimizing the performance of the solid-state battery. Furthermore, the first sulfide solid electrolyte in the first solid electrolyte layer can maintain the electronic conductivity of the solid electrolyte itself at a low level.

[0030] In this embodiment of the present disclosure, the solid state battery may be an all-solid state battery or a semi-solid state battery.

[0031] In this embodiment of the present disclosure, the positive electrode may include a positive electrode current collector and a positive electrode material layer disposed on at least one side of the positive electrode current collector. The positive electrode current collector may include, but is not limited to, a metal film, a foam metal mesh, etc., and may specifically be aluminum foil, carbon-coated aluminum foil, etc. The positive electrode material layer may include a positive electrode active material, a solid electrolyte material, a conductive agent, a binder, etc. Using the mass of the positive electrode material layer as the basis, the content of the positive electrode active material is 50% to 85% by mass, the content of the solid electrolyte is 5% to 49% by mass, the content of the binder is 0.1% to 10% by mass, and the content of the conductive agent is 0% to 10% by mass. The positive electrode active material can be selected from known positive electrode active materials used in rechargeable batteries, such as materials that can reversibly extract and insert lithium ions, including, but not limited to, olivine-type positive electrode active materials (e.g., LiFePO), layered oxide-type positive electrode active materials (e.g., ternary materials NCM and NCA, or lithium cobalt oxide LiCoO), spinel-type positive electrode active materials (e.g., LiMnO or LiTiO), and the like. 12 ), and sulfur and sulfide positive electrode active materials (e.g., S8, FeS2, or CuS). The solid electrolyte material can be selected from known sulfide solid electrolytes and known halide solid electrolytes. For example, sulfide solid electrolytes include Li3PS4, LGPS, Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 6-z PS 5-z Cl 1+z , LiI-(70Li2S-30P2S5), Li7P3S 11, Li4PS4I, Li7P2S8I, Li2SiS3, etc. The halide solid electrolyte may be selected from Li3InCl6, Li3YCl6, etc. The binder may be selected from binders commonly used in positive electrodes, including, but not limited to, one or more of polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile butadiene rubber (NBR), polyacrylate, poly(acrylic acid) (PAA), alkyl cellulose, and polyethylene oxide (PEO). The conductive agent may be selected from conductive agents commonly used in positive electrodes, such as acetylene black, carbon nanotubes, carbon fibers, and carbon black.

[0032] In this embodiment of the present disclosure, the negative electrode can be selected from known negative electrodes used in rechargeable batteries. For example, the negative electrode can be selected from lithium foil, lithium alloy foil, copper foil bonded with lithium metal, stainless steel foil bonded with lithium metal, copper foil bonded with lithium alloy, stainless steel foil bonded with lithium alloy, etc. The lithium alloy can be selected from one or more of lithium indium alloy, lithium silicon alloy, lithium boron alloy, lithium tin alloy, lithium magnesium alloy, lithium aluminum alloy, lithium silver alloy, and silicon-based negative electrode.

[0033] In some embodiments of the present disclosure, after the first charge / discharge of the solid-state battery, an interface layer is formed between the second solid electrolyte layer and the negative electrode, the interface layer comprising Li3P. The ionic conductivity of Li3P at room temperature is 10 -4 The ionic conductivity is on the order of 1000 S / cm. The high ionic conductivity of the interfacial layer reduces the overall impedance of the solid-state battery, improving its performance. The composition of the interfacial layer can be determined by combined analysis using XPS and nuclear magnetic resonance.

[0034] In some embodiments of the present disclosure, the Li3P content in the interface layer is 5% to 25% by weight, based on the weight of the interface layer. By ensuring that the Li3P content is within this range, the ionic conductivity of the interface layer can be further improved, the overall impedance of the solid-state battery can be reduced, and the interface layer can have a stable structure. Furthermore, excessively high electronic conductivity of the interface layer, which would be caused by an excessively high Li3P content, can be avoided. This avoids the continuous interaction of the negative electrode with the electrolyte, which would result in an excessively thick interface layer and excessively high impedance of the interface layer, thereby affecting battery performance.

[0035] In some embodiments of the present disclosure, the interfacial layer comprises Li2S, Li2S a , M1 b P, and M2 c M1 and M2 are each independently selected from one or more of Si, Ge, Sn, Al, Ga, and In. The ranges of a, b, and c are 2≦a≦8, 0.75≦b≦1.5, and 0.5≦c≦1, respectively. The interfacial layer may further comprise one or more of Li2S, Li2S a , M1 b P, and M2 c When the second sulfide solid electrolyte contains a halogen element X, the interface layer further contains a LiX component, where X is selected from F, Cl, Br, or I. Among these interface layer components, Li2S, Li2S a , and LiX can maintain the electronic conductivity of the interface layer at a low level, thus preventing the negative electrode from continuously reducing the electrolyte, which would cause an excessively thick interface layer and an excessively high interface ionic impedance. b P and M2 c S can inhibit the formation of lithium dendrites to a certain extent, which helps improve the cycle stability of the battery.

[0036] In some embodiments of the present disclosure, the negative electrode comprises lithium metal or a lithium alloy. Such negative electrodes have a high lithium insertion capacity, and therefore the solid-state battery has a high energy density.

[0037] In some embodiments of the present disclosure, a method for manufacturing a solid-state battery includes the following steps.

[0038] (1) Positive electrodes are manufactured using methods such as wet coating or dry extrusion. Using wet coating, a positive electrode active material, a solid electrolyte material, a conductive agent, and a binder can be dispersed in a solvent to obtain a positive electrode slurry. The positive electrode slurry is then applied to a positive electrode current collector, which is then dried, rolled, and divided to obtain a positive electrode. The positive electrode includes a positive electrode current collector and a positive electrode material layer. The solvent is selected from low- to medium-polarity solvents. The low- to medium-polarity solvent can be selected from one or more of methylcyclohexane, heptane, decane, methyl phenyl ether, cyclopentyl methyl ether, toluene, dimethylbenzene, butyl butyrate, and methyl benzoate. Using dry extrusion, the positive electrode active material, the solid electrolyte material, the conductive agent, and the binder can be homogeneously mixed and then extruded to form a positive electrode material layer.

[0039] (2) After mixing the first sulfide solid electrolyte and the binder, the mixed first sulfide solid electrolyte and binder are coated, laminated, or transferred onto the surface of the positive electrode material layer to form a first solid electrolyte layer. The binder in the first solid electrolyte layer can be selected from one or more of polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile butadiene rubber (NBR), polyacrylate, poly(acrylic acid) (PAA), alkyl cellulose, and polyethylene oxide (PEO). Coating refers to directly coating an electrolyte slurry, prepared by dispersing the solid electrolyte and the binder in a solvent, onto the surface of the positive electrode material layer, followed by drying and rolling to form a solid electrolyte layer directly on the surface of the positive electrode. Lamination refers to applying the electrolyte slurry to a PET film using a wet coating method. The electrolyte slurry is then peeled off by rolling to form a free-standing electrolyte film. Alternatively, a free-standing electrolyte film can be directly fabricated by dry extrusion of the solid electrolyte and binder. The free-standing electrolyte film is then laminated onto a cathode sheet, and the free-standing electrolyte film and cathode sheet are combined under a specific pressure. Transfer refers to the process of rolling the electrolyte layer formed on a PET film by wet coating onto the cathode sheet, transferring the electrolyte layer from the PET film to the surface of the cathode layer.

[0040] (3) After mixing the phosphide solid electrolyte and the binder, the mixed phosphide solid electrolyte and binder are coated, laminated, or transferred onto the surface of the first solid electrolyte layer to form a second solid electrolyte layer. The binder in the second solid electrolyte layer can be selected from one or more of polyvinylidene difluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), nitrile butadiene rubber (NBR), polyacrylate, poly(acrylic acid) (PAA), alkyl cellulose, and polyethylene oxide (PEO). When the second solid electrolyte layer includes a second sulfide solid electrolyte, the second sulfide solid electrolyte, the phosphide solid electrolyte, and the binder can be mixed and then coated, laminated, or transferred onto the surface of the first solid electrolyte layer to form the second solid electrolyte layer.

[0041] (4) The negative electrode sheet is pressed onto the second solid electrolyte layer to obtain an all-solid-state battery.

[0042] The present disclosure further provides an electric device including the aforementioned solid-state battery. The electric device may be a vehicle, an energy storage power plant, an electronic device, etc. The vehicle may be a pure electric vehicle, a hybrid electric vehicle, etc. The electronic device may be a 3C product, etc. [Example]

[0043] This embodiment of the present disclosure is further described below with reference to some specific embodiments.

[0044] Embodiment 1 (1) Production of phosphide solid electrolyte In a glove box, a total of 5 g of lithium metal powder, aluminum powder, and red phosphorus powder were accurately weighed according to the stoichiometric ratio of Li9AlP4 and placed in a zirconia-lined ball mill tank. Zirconia ball mill beads were added to the ball mill tank. The ball-to-material ratio was adjusted to 25:1. Ball milling was carried out for 18 hours at a speed of 1000 RPM in a high-speed ball mill. Cooling water was used to cool the ball mill tank throughout the entire ball milling process, and the temperature during ball milling was adjusted to 15±5°C. After ball milling was completed, the powder was removed.

[0045] The powder was pressed into a block using a cold press, and the block was sealed in an ampoule. The ampoule was placed in a muffle furnace for sintering. The sintering temperature was adjusted to 800°C, and the sintering time was 24 hours. The sintered electrolyte sheet was crushed into powder to obtain the corresponding Li9AlP4 solid electrolyte.

[0046] (2) Manufacturing of solid-state batteries All of the following steps were completed in a dry room with a dew point below -50°C.

[0047] Step 1: 75g LiNi 0.6 Mn 0.2 Co 0.2 O2 (NCM622) cathode material, 20 g of solid electrolyte Li6PS5Cl, 3 g of nitrile butadiene rubber binder, and 2 g of acetylene black were added to 100 g of toluene solvent, which was then stirred in a vacuum mixer to form a stable and homogeneous cathode slurry. The cathode slurry was uniformly and intermittently coated on both sides of an aluminum foil (the aluminum foil size was defined as 160 mm wide and 16 μm thick), which was then baked at 373 K. After pressing by a roll press, a cathode material layer with a thickness of 80 μm on one side was formed on both sides of the aluminum foil, resulting in a cathode sheet.

[0048] Step 2: 58.2 g of Li6PS5Cl and 1.8 g of nitrile butadiene rubber binder were added to 60 g of toluene solution, which was thoroughly stirred to form a stable and homogeneous slurry. The solution was continuously applied to the positive electrode sheet, which was then baked at 373 K to obtain a composite of the positive electrode sheet and the first solid electrolyte layer. The thickness of the first solid electrolyte layer was 50 μm. In Step 2, the D50 of Li6PS5Cl was 4 μm.

[0049] Step 3: 0.18 g of nitrile butadiene rubber binder and a mixed powder of 1.746 g of Li9AlP4 and 4.074 g of Li6PS5Cl were added to 6 g of toluene solution and thoroughly stirred to form a stable and homogeneous slurry. The solution was continuously applied to the first solid electrolyte layer of the composite of the positive electrode sheet and the first solid electrolyte layer, which was then baked at 373 K to obtain a composite of the positive electrode sheet, the first solid electrolyte layer, and the second solid electrolyte layer. The thickness of the second solid electrolyte layer was 5 μm. In Step 3, the D50 of Li6PS5Cl was 1 μm, and the D50 of Li9AlP4 was 1 μm.

[0050] Step 4: The composite layer of the positive electrode sheet, the first solid electrolyte layer, and the second solid electrolyte layer was cut into a composite film of the positive electrode sheet, the first solid electrolyte layer, and the second solid electrolyte layer, having a size of 21 mm length x 41 mm width.

[0051] Step 5: A lithium-copper composite foil (i.e., copper foil bonded with lithium metal) was selected as the negative electrode. The lithium layer had a thickness of 15 μm, and the composite foil was cut into a negative electrode film with a size of 20 mm × 40 mm.

[0052] Step 6: The composite film of the positive electrode sheet, the first solid electrolyte layer, and the second solid electrolyte layer obtained in Step 4 and the negative electrode film obtained in Step 5 were placed side by side in a hot press, and hot pressing was carried out at 453 K for 1 h under a pressure of 200 MPa. After evacuation, the sample was removed and sealed using an aluminum plastic film. Finally, the pressed sample was pressed in an isostatic press under 200 MPa for 300 seconds. Thus, a solid-state battery of this embodiment was obtained, designated as C1.

[0053] Embodiment 2 (1) Preparation of phosphide solid electrolyte: In a glove box, a total of 5 g of lithium metal powder, gallium powder, and red phosphorus powder were accurately weighed according to the stoichiometric ratio of Li9GaP4 and placed in a zirconia-lined ball mill tank. Zirconia ball mill beads were placed in the ball mill tank. The ball-to-material ratio was adjusted to 25:1. Ball milling was carried out for 18 hours at a speed of 1000 RPM in a high-speed ball mill. Throughout the ball milling process, cooling water was used to cool the ball mill tank, and the temperature during ball milling was adjusted to 15±5°C. After ball milling was completed, the powders were removed.

[0054] The powder was pressed into a block using a cold press, and the block was sealed in an ampoule. The ampoule was placed in a muffle furnace for sintering. The sintering temperature was adjusted to 400°C, and the sintering time was 24 hours. The sintered electrolyte sheet was crushed into powder to obtain the corresponding Li9GaP4 solid electrolyte.

[0055] (2) Preparation of solid-state battery: The steps for preparing a solid-state battery in embodiment 2 are the same as those in embodiment 1, except that 1.746 g of Li9AlP4 is replaced with 1.746 g of Li9GaP4. The obtained solid-state battery is designated as C2.

[0056] Embodiment 3 (1) Preparation of phosphide solid electrolyte: In a glove box, Li 14A total of 5 g of lithium metal powder, silicon powder, and red phosphorus powder were accurately weighed according to the stoichiometric ratio of SiP6 and placed in a zirconia-lined ball mill tank. Zirconia ball mill beads were placed in the ball mill tank. The ball-to-material ratio was adjusted to 25:1. Ball milling was carried out for 18 hours at a speed of 1000 RPM in a high-speed ball mill. Cooling water was used to cool the ball mill tank throughout the entire ball milling process, and the temperature during ball milling was adjusted to 15±5°C. After ball milling was completed, the powder was removed.

[0057] The powder was pressed into a block using a cold press, and the block was sealed in an ampoule. The ampoule was placed in a muffle furnace for sintering. The sintering temperature was adjusted to 700°C, and the sintering time was 24 hours. The sintered electrolyte sheet was crushed into powder, and the corresponding Li 14 The SiP6 solid electrolyte was obtained.

[0058] (2) Solid-state battery production: 1.746g of Li9AlP4 was added to 1.746g of Li 14 Except for replacing SiP6, the steps for preparing the solid-state battery in embodiment 3 are the same as embodiment 1. The obtained solid-state battery is designated as C3.

[0059] Embodiment 4 (1) Production of phosphide solid electrolyte In the glove box, Li 14 A total of 5 g of lithium metal powder, germanium powder, and red phosphorus powder were accurately weighed according to the stoichiometric ratio of GeP6 and placed in a zirconia-lined ball mill tank. Zirconia ball mill beads were placed in the ball mill tank. The ball-to-material ratio was adjusted to 25:1. Ball milling was carried out for 18 hours at a speed of 1000 RPM in a high-speed ball mill. Cooling water was used to cool the ball mill tank throughout the entire ball milling process, and the temperature during ball milling was adjusted to 15±5°C. After ball milling was completed, the powders were removed.

[0060] The powder was pressed into a block using a cold press, and the block was sealed in an ampoule. The ampoule was placed in a muffle furnace for sintering. The sintering temperature was adjusted to 500°C, and the sintering time was 24 hours. The sintered electrolyte sheet was crushed into powder, and the corresponding Li 14 A GeP6 solid electrolyte was obtained.

[0061] (2) Solid-state battery production: 1.746g of Li9AlP4 was added to 1.746g of Li 14 Except for replacing GeP6, the steps for preparing the solid-state battery in embodiment 4 are the same as those in embodiment 1. The obtained solid-state battery is designated as C4.

[0062] Embodiment 5 The steps for preparing the solid-state battery in Embodiment 5 are the same as those in Embodiment 1, except that 1.746 g of Li9AlP4 is replaced with 0.873 g of Li9AlP4 and 0.873 g of Li9GaP4 (wherein the steps for preparing Li9GaP4 are the same as those in Embodiment 2). The obtained solid-state battery is designated as C5.

[0063] EMBODIMENT 6 Li6PS5Cl in steps 1, 2 and 3 11 The steps for preparing a solid-state battery in embodiment 6 are the same as those in embodiment 1, except that the step of preparing a solid-state battery in embodiment 6 is replaced with the step of preparing a solid-state battery in embodiment 1. The obtained solid-state battery is designated as C6.

[0064] EMBODIMENT 7 The steps for preparing the solid-state battery in Embodiment 7 are basically the same as those in Embodiment 1. The only difference is that in Step 2, 58.2 g of Li6PS5Cl and 1.8 g of nitrile butadiene rubber binder are replaced with 51 g of Li6PS5Cl and 9 g of nitrile butadiene rubber binder. The obtained solid-state battery is designated as C7.

[0065] EMBODIMENT 8 The steps for preparing a solid-state battery in Embodiment 8 are basically the same as those in Embodiment 1. The only difference is that in Step 3, the mixed powder of 1.746 g of Li9AlP4 and 4.074 g of Li6PS5Cl, and 0.18 g of nitrile-butadiene rubber binder are replaced with the mixed powder of 1.53 g of Li9AlP4 and 3.57 g of Li6PS5Cl, and 0.9 g of nitrile-butadiene rubber binder. The obtained solid-state battery is designated as C8.

[0066] EMBODIMENT 9 The steps for preparing a solid-state battery in Embodiment 9 are basically the same as those in Embodiment 1. The only difference is that in Step 3, the mixed powder of 1.746 g of Li9AlP4 and 4.074 g of Li6PS5Cl is replaced with the mixed powder of 5.238 g of Li9AlP4 and 0.582 g of Li6PS5Cl. The obtained solid-state battery is designated as C9.

[0067] EMBODIMENT 10 The steps for preparing a solid-state battery in Embodiment 10 are basically the same as those in Embodiment 1. The only difference is that in Step 3, the mixed powder of 1.746 g of Li9AlP4 and 4.074 g of Li6PS5Cl is replaced with the mixed powder of 0.291 g of Li9AlP4 and 5.529 g of Li6PS5Cl. The obtained solid-state battery is designated as C10.

[0068] EMBODIMENT 11 The steps for preparing a solid-state battery in Embodiment 11 are basically the same as those in Embodiment 1. The only difference is that in Step 3, the mixed powder of 1.746 g of Li9AlP4 and 4.074 g of Li6PS5Cl is replaced with 5.82 g of Li9AlP4 powder. The obtained solid-state battery is designated as C11.

[0069] EMBODIMENT 12 The steps for preparing a solid-state battery in Embodiment 12 are basically the same as those in Embodiment 1. The only difference is that in Step 3, the mixed powder of 1.746 g of Li9AlP4 and 4.074 g of Li6PS5Cl is replaced with the mixed powder of 0.116 g of Li9AlP4 and 5.704 g of Li6PS5Cl. The obtained solid-state battery is designated as C12.

[0070] EMBODIMENT 13 The steps for preparing a solid-state battery in Embodiment 13 are basically the same as those in Embodiment 1. The only difference is that in Step 3, the mixed powder of 1.746 g of Li9AlP4 and 4.074 g of Li6PS5Cl is replaced with a mixed powder of 4.074 g of Li9AlP4 and 1.746 g of Li6PS5Cl. The obtained solid-state battery is designated as C13.

[0071] EMBODIMENT 14 The steps for manufacturing a solid-state battery in embodiment 14 are basically the same as those in embodiment 1. The only differences are as follows: In step 2, the mass ratio of Li6PS5Cl to nitrile butadiene rubber binder remained unchanged, and the total mass of Li6PS5Cl and nitrile butadiene rubber binder was adjusted so that the thickness of the first solid electrolyte layer was 10 μm.

[0072] In step 3, the mass ratio of Li9AlP4, Li6PS5Cl, and nitrile butadiene rubber binder remained unchanged, and the total mass of Li9AlP4, Li6PS5Cl, and nitrile butadiene rubber binder was adjusted so that the thickness of the second solid electrolyte layer was 15 μm.

[0073] The resulting solid-state battery was designated as C14.

[0074] EMBODIMENT 15 The steps for manufacturing a solid-state battery in embodiment 15 are basically the same as those in embodiment 1. The only differences are as follows: In step 2, the mass ratio of Li6PS5Cl to nitrile butadiene rubber binder remained unchanged, and the total mass of Li6PS5Cl and nitrile butadiene rubber binder was adjusted so that the thickness of the first solid electrolyte layer was 200 μm.

[0075] In step 3, the mass ratio of Li9AlP4, Li6PS5Cl, and the nitrile butadiene rubber binder remained unchanged, and the total mass of Li9AlP4, Li6PS5Cl, and the nitrile butadiene rubber binder was adjusted so that the thickness of the second solid electrolyte layer was 1 μm.

[0076] The resulting solid-state battery was designated as C15.

[0077] EMBODIMENT 16 The steps for manufacturing a solid-state battery in embodiment 16 are basically the same as those in embodiment 1. The only differences are as follows: In stage 2, the D50 of Li6PS5Cl was 8 μm. In stage 3, the D50 of Li6PS5Cl was 2.2 μm and the D50 of Li9AlP4 was 2.2 μm.

[0078] EMBODIMENT 17 The steps for manufacturing a solid-state battery in embodiment 17 are basically the same as those in embodiment 1. The only differences are as follows: In stage 2, the D50 of Li6PS5Cl was 11 μm. In stage 3, the D50 of Li6PS5Cl was 4 μm and the D50 of Li9AlP4 was 3 μm.

[0079] Comparative Example 1 The steps for manufacturing a solid-state battery in Comparative Example 1 are basically the same as those in Example 1. The only differences are as follows: In step 3 for preparing a solid-state battery, the mixed powder of 1.746 g of Li9AlP4 and 4.074 g of Li6PS5Cl was replaced with 5.82 g of Li6PS5Cl powder. The obtained solid-state battery was designated as DC1.

[0080] Comparative Example 2 (1) Li9AlP4 was prepared using the same steps as in Example 1.

[0081] (2) Manufacturing of solid-state batteries All of the following steps were completed in a dry room with a dew point below -50°C.

[0082] Step 1: 75 g of NCM622 cathode material, 20 g of solid electrolyte Li6PS5Cl, 3 g of nitrile butadiene rubber binder, and 2 g of acetylene black were added to 100 g of toluene solvent, which was then stirred in a vacuum mixer to form a stable and homogeneous cathode slurry. The cathode slurry was evenly and intermittently applied to both sides of an aluminum foil (the aluminum foil size was defined as 160 mm wide and 16 μm thick), which was then baked at 373 K. After pressing by a roll press, a cathode material layer with a thickness of 80 μm on one side was formed on both sides of the aluminum foil, resulting in a cathode sheet.

[0083] Step 2: 62.274 g of Li6PS5Cl, 1.746 g of Li9AlP4, and 1.98 g of nitrile butadiene rubber binder were added to 66 g of toluene solution, which was thoroughly stirred to form a stable and homogeneous slurry. The solution was continuously applied to the positive electrode sheet, which was then baked at 373 K to obtain a composite of the positive electrode sheet and the solid electrolyte layer. The thickness of the solid electrolyte layer was 55 μm. In Step 2, the D50 of Li6PS5Cl was 4 μm, and the D50 of Li9AlP4 was 1 μm.

[0084] Step 3: The composite layer of the positive electrode sheet and the solid electrolyte layer was cut into a composite film of the positive electrode sheet and the solid electrolyte layer having a size of 21 mm length x 41 mm width.

[0085] Step 4: A lithium copper composite foil was selected as the negative electrode. The thickness of the lithium layer was 15 μm, and the composite foil was cut into a negative electrode film with a size of 20 mm × 40 mm.

[0086] Step 5: The composite film of the positive electrode sheet and the solid electrolyte layer obtained in Step 3 and the negative electrode film obtained in Step 4 were placed side by side in a hot press, and hot pressing was carried out at 453 K for 1 h under a pressure of 200 MPa. After evacuation, the sample was removed and sealed using an aluminum plastic film. Finally, the pressed sample was pressed in an isostatic press under 200 MPa for 300 seconds. Thus, a solid-state battery of this embodiment was obtained. The obtained solid-state battery was designated as DC2.

[0087] Comparative Example 3 (1) Li9AlP4 was prepared using the same steps as in Example 1.

[0088] (2) Manufacturing of solid-state batteries All of the following steps were completed in a dry room with a dew point below -50°C.

[0089] Step 1: 75 g of NCM622 cathode material, 20 g of solid electrolyte Li9AlP4, 3 g of nitrile butadiene rubber binder, and 2 g of acetylene black were added to 100 g of toluene solvent, which was then stirred in a vacuum mixer to form a stable and homogeneous cathode slurry. The cathode slurry was evenly and intermittently applied to both sides of an aluminum foil (the aluminum foil size was defined as 160 mm wide and 16 μm thick), which was then baked at 373 K. After pressing by a roll press, a cathode material layer with a thickness of 80 μm on one side was formed on both sides of the aluminum foil, resulting in a cathode sheet.

[0090] Step 2: 64.02 g of Li9AlP4 and 1.98 g of nitrile butadiene rubber binder were added to 66 g of toluene solution, which was thoroughly stirred to form a stable and homogeneous slurry. The solution was continuously applied to the positive electrode sheet, which was then baked at 373 K to obtain a composite of the positive electrode sheet and the solid electrolyte layer. The thickness of the solid electrolyte layer was 55 μm. In Step 2, the D50 of Li9AlP4 was 4 μm.

[0091] Step 3: The composite layer of the positive electrode sheet and the solid electrolyte layer was cut into a composite film of the positive electrode sheet and the solid electrolyte layer having a size of 21 mm length x 41 mm width.

[0092] Step 4: A lithium copper composite foil was selected as the negative electrode. The thickness of the lithium layer was 15 μm, and the composite foil was cut into a negative electrode film with a size of 20 mm × 40 mm.

[0093] Step 5: The composite film of the positive electrode sheet and the solid electrolyte layer obtained in Step 3 and the negative electrode film obtained in Step 4 were placed side by side in a hot press, and hot pressing was carried out at 453 K for 1 h under a pressure of 200 MPa. After evacuation, the sample was removed and sealed using an aluminum plastic film. Finally, the pressed sample was pressed in an isostatic press under 200 MPa for 300 seconds. Thus, a solid-state battery of this embodiment was obtained. The obtained solid-state battery was designated as DC3.

[0094] A battery cycle life test was carried out on the solid batteries C1 to C17 obtained in Embodiments 1 to 17, and the solid batteries DC1 to DC3 obtained in Comparative Examples 1 to 3. The test method was as follows.

[0095] Five replicates of the batteries manufactured in each embodiment and comparative example were selected and subjected to a charge-discharge cycle test at 0.1 C in a LAND CT 2001C rechargeable battery performance measurement device under conditions of 298 K±1 K. The steps were as follows: each battery was allowed to rest for 10 minutes, and then constant current charging was performed on the battery until the voltage reached 4.2 V. Each battery was allowed to rest for 10 minutes, and then constant current discharging was performed on the battery until the voltage dropped to 2.6 V. This process constituted one cycle. The initial discharge capacity was recorded, and the initial discharge specific capacity was calculated as the initial discharge capacity divided by the mass of the positive electrode active material. The above steps were repeated. Using an electrochemical workstation EIS, the AC impedance of each battery at 100% SOC for the first, tenth, and 20th cycles was recorded. The average value of each group was used as the cyclic impedance, which was separately designated as the first, tenth, and twentieth impedances. During the cycle, the cycle was terminated when the battery capacity fell below 80% of the initial discharge capacity. In this case, the number of cycles was the cycle life of the battery, and the average value for each group was obtained. The battery parameters and average first discharge capacity data are shown in the table below.

[0096] [Table 1]

[0097] The reduction potential of each solid electrolyte was tested using a CV curve. Specifically, the electrolytes for the second solid electrolyte layer in each of Examples 1 to 17 and Comparative Example 1, and the electrolytes for the solid electrolyte layer in each of Comparative Examples 2 and 3 were selected. 10 mg of electrolyte from the second solid electrolyte layer or the solid electrolyte layer was homogeneously mixed with 0.1 mg of acetylene black and used as one side of a battery electrode. A lithium-copper composite foil with a thickness of 15 μm and a diameter of 15 mm was used as the counter electrode. 260 mg of Li6PS5Cl was used as the intermediate electrolyte layer. Coin battery 1 was assembled and connected to an electrochemical workstation. Using a CV program, a sweep from the OCV state to 0 V was performed at a rate of 0.1 mV / s. The voltage at which a reduction current occurred was recorded as the reduction potential of the electrolyte.

[0098] 260 mg of electrolyte from the second solid electrolyte layer or 260 mg of electrolyte from the first solid electrolyte layer was weighed and placed in a circular mold with a diameter of 15 mm. The electrolyte sheet was preformed in a powder cold press at 50 MPa, and then carbon-coated aluminum foil with a diameter of 15 mm was attached to both sides of the electrolyte and reformed at 500 MPa. The carbon-coated aluminum foil was pressed onto the electrolyte sheet. The thickness of the electrolyte layer was accurately measured using a micrometer and indicated as L. The electrolyte layer was sealed in a 2025 coin battery box to form Battery 2.

[0099] Battery 1 was connected to an electrochemical workstation. Using an EIS program, the amplitude was set to 10 mV and the sweep frequency range was 7 MHz to 1 Hz. The impedance R1 of the electrolyte and the initial ionic conductivity σ of the electrolyte were obtained through the measurement. i is the formula σ i = L / R1S. S = πd 2 / 4.

[0100] Using a direct current polarization program (PPI), the voltage was set to U = 50 mV, and the test time was 1 hour. In this state, the steady-state current I of Battery 2 was tested, and the impedance R2 = U / I was calculated. The electronic conductivity of the electrolyte of the second solid electrolyte layer was σ c = L / R²S.

[0101] In Table 2, "electrolyte of the second solid electrolyte layer, or electrolyte of the solid electrolyte layer" refers to the electrolyte of the second solid electrolyte layer in each of Embodiments 1 to 17 and Comparative Example 1, or the electrolyte of the solid electrolyte layer in each of Comparative Examples 2 and 3.

[0102] [Table 2]

[0103] The composition of the electrolyte interfacial layer can be examined using XPS. The negative electrode sheet of the battery is removed, the surface of the sample is irradiated with X-rays, and the escaped photoelectrons are collected to form a characteristic photoelectron spectrum. After the spectrum is calibrated, smoothed, and background subtracted, peak separation is performed, and the composition and proportion of the interfacial layer are identified based on peak position and area.

[0104] [Table 3]

[0105] The above data reveal the following: In Comparative Example 1, no phosphide is included, and the interface layer has high impedance, resulting in a short cycle life of the battery. In Comparative Example 2, the first sulfide solid electrolyte layer is absent, and the overall electronic conductivity of the battery is high, causing self-discharge and further affecting battery performance. Furthermore, the phosphide electrolyte is in direct contact with the positive electrode layer and is easily oxidized by the positive electrode. As a result, more side reactions occur on the positive electrode side, affecting battery performance. In Comparative Example 3, only a phosphide solid electrolyte is used as the solid electrolyte, and no sulfide solid electrolyte is used. Similar and more serious problems exist as in Comparative Example 2.

[0106] In this description, the recitation of a reference term such as "embodiments," "some embodiments," "examples," "particular examples," or "some examples" means that a particular feature, structure, material, or characteristic described with reference to that embodiment or example is included in at least one embodiment or example of the present disclosure. In this description, illustrative descriptions of the foregoing terms do not necessarily refer to the same embodiment or example. Furthermore, the described features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0107] Furthermore, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or suggesting relative importance. In the description of this disclosure, "several" means at least two, e.g., two or three, unless otherwise defined.

[0108] Although embodiments of the present disclosure have been shown and described above, it can be understood that the foregoing embodiments are illustrative and cannot be understood as limitations of the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the foregoing embodiments within the scope of the present disclosure.

Claims

1. A solid electrolyte comprising a first solid electrolyte layer and a second solid electrolyte layer, wherein the first solid electrolyte layer comprises a first sulfide solid electrolyte, and the second solid electrolyte layer comprises a phosphide solid electrolyte.

2. 2. The solid electrolyte according to claim 1, wherein the phosphide solid electrolyte contains phosphorus element having a valence of −3.

3. 3. The solid electrolyte according to claim 1, wherein the reduction potential of the phosphide solid electrolyte is 0 V to 1.2 V.

4. The phosphide solid electrolyte is Li 3x-3 AP x and Li 3y-4 BP y wherein the element P has a valence of −3; the element A is selected from at least one of Al, Ga, and In; the element B is selected from at least one of Si, Ge, and Sn; x is an integer of 2 to 4; and y is an integer of 2 to 6.

5. The phosphide solid electrolyte is Li 9 AlP 4 , Li 9 GaP 4 , Li 9 InP 4 , Li 3 AlP 2 , Li 3 GaP 2 , Li 3 InP 2 , Li 8 SiP 4 , Li 8 GeP 4 , Li 8 SnP 4 , Li 2 SiP 2 , Li 2 GeP 2 , Li 2 SnP 2 , Li 14 SiP 6 , and Li 14 GeP 6 5. The solid electrolyte of claim 1, comprising one or more of:

6. The first sulfide solid electrolyte is Li 3 P.S. 4 , Li 10 GeP 2 S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 6-z P.S. 5-z Cl 1+z , LiI-(70Li 2 S-30P 2 S 5 ), Li 7 P 3 S 11 , Li 4 P.S. 4 I, Li 7 P 2 S 8 I, and Li 2 SiS 3 and Li 6-z P.S. 5-z Cl 1+z 6. The solid electrolyte according to claim 1, wherein the value of z is in the range of 0≦z≦1.

7. 7. The solid electrolyte according to claim 1, wherein the total mass of the first solid electrolyte layer is used as a reference, and the content of the first sulfide solid electrolyte in the first solid electrolyte layer is 90% by mass to 99.9% by mass.

8. 8. The solid electrolyte of claim 1, wherein the second solid electrolyte layer further comprises a second sulfide solid electrolyte.

9. The total mass of the second solid electrolyte layer is used as a reference, and the content of the second sulfide solid electrolyte and the phosphide solid electrolyte in the second solid electrolyte layer is 90% by mass to 99.9% by mass; and The total mass of the second sulfide solid electrolyte and the phosphide solid electrolyte in the second solid electrolyte layer is used as a standard, and in the second solid electrolyte layer, the content of the second sulfide solid electrolyte is 10% by mass to 95% by mass, and the content of the phosphide solid electrolyte is 5% by mass to 90% by mass. The solid electrolyte according to claim 8.

10. 10. The solid electrolyte according to claim 9, wherein the total mass of the second sulfide solid electrolyte and the phosphide solid electrolyte in the second solid electrolyte layer is used as a standard, and the content of the second sulfide solid electrolyte in the second solid electrolyte layer is 30% by mass to 70% by mass, and the content of the phosphide solid electrolyte is 30% by mass to 70% by mass.

11. The second sulfide solid electrolyte is Li 3 P.S. 4 , Li 10 GeP 2 S 12 , Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 , Li 6-z P.S. 5-z Cl 1+z , LiI-(70Li 2 S-30P 2 S 5 ), Li 7 P 3 S 11 , Li 4 P.S. 4 I, Li 7 P 2 S 8 I, and Li 2 SiS 3 and Li 6-z P.S. 5-z Cl 1+z 11. The solid electrolyte according to claim 8, wherein the value of z is in the range of 0≦z≦1.

12. 12. The solid electrolyte according to claim 1, wherein the first solid electrolyte layer has a thickness of 15 μm to 200 μm, and the second solid electrolyte layer has a thickness of 1 μm to 15 μm.

13. 13. The solid electrolyte according to claim 1, wherein the first solid electrolyte layer has a thickness of 15 μm to 50 μm, and the second solid electrolyte layer has a thickness of 3 μm to 7 μm.

14. The first sulfide solid electrolyte has a D50 of 1 μm to 10 μm, the phosphide solid electrolyte has a D50 of 0.5 μm to 4 μm, and the second sulfide solid electrolyte has a D50 of 0.5 μm to 4 μm. A solid electrolyte according to any one of claims 8 to 11.

15. 15. A solid-state battery comprising: a positive electrode; a negative electrode; and the solid electrolyte according to claim 1, wherein the solid electrolyte is disposed between the positive electrode and the negative electrode, the first solid electrolyte layer is disposed between the positive electrode and the second solid electrolyte layer, and the second solid electrolyte layer is disposed between the first solid electrolyte layer and the negative electrode.

16. After the first charge and discharge of the solid-state battery, an interface layer is formed between the second solid electrolyte layer and the negative electrode, and the interface layer contains Li 3 The solid-state battery of claim 15 comprising P.

17. Li in the interface layer 3 The solid state battery according to claim 16, wherein the content of P is 5% by mass to 25% by mass relative to the mass of the interface layer.

18. The interface layer is Li 2 S., Li. 2 S a , LiX, M1 b P, and M2 c 18. The solid-state battery according to claim 16 or 17, further comprising one or more of S, wherein X is one or more of F, Cl, Br, and I, M1 and M2 are each independently selected from one or more of Si, Ge, Sn, Al, Ga, and In, and the ranges of a, b, and c are 2≦a≦8, 0.75≦b≦1.5, and 0.5≦c≦1, respectively.

19. 19. The solid-state battery of any one of claims 15 to 18, wherein the negative electrode comprises lithium metal or a lithium alloy.

20. 20. An electrical device comprising the solid state battery of any one of claims 15 to 19.

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