A double-layer solid electrolyte membrane, a preparation method thereof, and a all-solid-state battery

Abstract

The present invention relates to the technical field of solid electrolytes, and discloses a double-layer solid electrolyte membrane, a preparation method thereof, and an all-solid-state battery. The double-layer solid electrolyte membrane includes a first solid electrolyte layer and a second solid electrolyte layer that are superposed on each other; the first solid electrolyte layer includes a hydride solid electrolyte, and the second solid electrolyte layer includes a halide solid electrolyte; the hydride solid electrolyte includes Li 7‑a P(BH4) a S 6‑a and / or Li 7‑a‑b P(BH4) a S 6‑a‑b X b , where X is a halogen, 0

Description

Technical Field

[0001] The present invention relates to the technical field of solid electrolytes, and particularly to a double-layer solid electrolyte membrane, a preparation method thereof, and a all-solid-state battery. Background Art

[0002] With the gradual increase in the penetration rate of electric vehicles and the continuous expansion of the scale of grid energy storage, the safety performance and energy density of batteries have received key attention as crucial indicators for practical applications. All-solid-state batteries use solid electrolytes to replace the separators and flammable liquid electrolytes in traditional liquid batteries, which are expected to improve the safety performance of batteries. At the same time, compared with liquid batteries, all-solid-state batteries have a higher compatibility with thick electrode technology, which helps to increase the mass ratio of active materials in the battery, thereby improving the energy density of the battery.

[0003] An ideal solid electrolyte needs to have characteristics such as high ionic conductivity, low electronic conductivity, wide electrochemical window, and high chemical stability. Generally speaking, solid electrolytes can achieve the performance indicators of high ionic conductivity and low electronic conductivity by combining crystal structure design and ion doping. For example, halogen anions are doped in hydride solid electrolytes, and transition metal cations are doped in sulfide and halide solid electrolytes. However, limited by the physical and chemical properties of materials, solid electrolytes usually do not have a wide electrochemical window and cannot simultaneously take into account high-potential cathode materials and low-potential anode materials. During the battery cycling process, under the multiple effects of electrochemistry, chemistry, and thermodynamics, a single solid electrolyte is prone to strong side reactions at the cathode or anode interface, resulting in rapid attenuation of the battery capacity. For example, hydrides and sulfides are easily decomposed at high potentials, sulfides are unstable to lithium metal, and halides are easily reduced at low potentials. Summary of the Invention

[0004] In order to solve the technical problem that a single solid electrolyte is prone to strong side reactions at the cathode or anode interface, resulting in rapid attenuation of the battery capacity, the present invention provides a double-layer solid electrolyte membrane, a preparation method thereof, and an all-solid-state battery. The double-layer solid electrolyte membrane of the present invention has good interfacial stability at the interfaces with the positive and negative electrodes, and there are fewer interfacial side reactions between the two solid electrolyte layers, which can enable the solid-state battery to have a high Coulomb efficiency and cycling stability.

[0005] The specific technical solution of the present invention is as follows:

[0006] In a first aspect, the present invention provides a double-layer solid electrolyte membrane, including a first solid electrolyte layer and a second solid electrolyte layer that are superposed on each other; the first solid electrolyte layer includes a hydride solid electrolyte, and the second solid electrolyte layer includes a halide solid electrolyte; the hydride solid electrolyte includes Li 7-a P(BH 4 ) a S6-a and / or Li 7-a-b P(BH 4 ) a S 6-a-b X b , wherein X is a halogen, 0 < a ≤ 2, 0 < b < 2.

[0007] In the double-layer solid electrolyte membrane of the present invention, the hydride solid electrolyte has good low-potential stability and stability against the negative electrode, enabling the first solid electrolyte layer to directly contact the negative electrode; the halide solid electrolyte has good high-potential stability and stability against the positive electrode, enabling the second solid electrolyte layer to directly contact the positive electrode. By the above method, the design of the double-layer solid electrolyte membrane in the present invention can solve the problem that a single type of solid electrolyte cannot be compatible with both the positive and negative electrodes at the same time, improve the interfacial stability between the solid electrolyte membrane and the electrode, and thus improve the Coulomb efficiency and cycle stability of the battery.

[0008] The hydride solid electrolyte contains hydride anions and has strong reducibility. The halide solid electrolyte contains high-valent metal ions. This causes direct contact between the two solid electrolytes at the interface between the first and second solid electrolyte layers, resulting in interfacial side reactions, thereby reducing the lithium ion transport rate and causing poor Coulomb efficiency and cycle stability of the battery. For this reason, the present invention uses Li 7-a P(BH 4 ) a S 6-a and / or Li 7-a-b P(BH 4 ) a S 6-a-b X b as the hydride solid electrolyte. Through P and S double substitution, the density of hydride anions in the unit cell can be reduced, the crystal structure stability can be improved, the reducibility of the electrolyte can be weakened, thereby improving the compatibility between the hydride electrolyte and the halide electrolyte, reducing interfacial side reactions, and contributing to improving the Coulomb efficiency and cycle stability of the battery. Moreover, although halogen ion substitution can also reduce the density of hydride anions in the hydride electrolyte unit cell, compared with only using halogen ion substitution, the present invention introduces P and S double substitution, which can form PS 4 3- anions in the crystal structure. The 4 - anions and the BH 4 - anions are both tetrahedral structures, and have a larger volume, a higher charge number, and a more stable anion configuration. Therefore, they can more effectively improve the crystal structure stability, weaken the electrolyte reducibility, thereby better improving the interfacial compatibility between the double-layer electrolytes and enhancing the Coulomb efficiency and cycle stability of the battery to a greater extent.

[0009] Preferably, the halide solid electrolyte includes Lic MZ d where M is at least one of Zr, Hf, Sc, In, Y, La, Nb, and Gd, Z is at least one of F, Cl, and I, 1 ≤ c ≤ 8, and 2 ≤ d ≤ 10.

[0010] Preferably, the Li 7-a-b P(BH 4 ) a S 6-a-b X b where X is at least one of F, Cl, and I.

[0011] Preferably, in the first solid electrolyte layer, the mass ratio of the hydride solid electrolyte is not less than 90%; in the second solid electrolyte layer, the mass ratio of the halide solid electrolyte is not less than 90%.

[0012] Further, in the first solid electrolyte layer, the mass ratio of the hydride solid electrolyte is 90 - 99.8%; in the second solid electrolyte layer, the mass ratio of the halide solid electrolyte is 90 - 99.8%.

[0013] Further, in the first solid electrolyte layer, the mass ratio of the hydride solid electrolyte is 95 - 99.8%; in the second solid electrolyte layer, the mass ratio of the halide solid electrolyte is 95 - 99.8%.

[0014] Preferably, the first solid electrolyte layer and the second solid electrolyte layer further include a polymer binder.

[0015] Further, the polymer binder includes at least one of styrene - butadiene rubber (SBR), nitrile - butadiene rubber (NBR), hydrogenated nitrile - butadiene rubber (HNBR), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene - butadiene block copolymer (SBS), styrene - ethylene - butylene - styrene block copolymer (SEBS), and polyisobutylene (PIB).

[0016] In a second aspect, the present invention provides a method for preparing the double - layer solid electrolyte membrane, including the following steps:

[0017] S1: Mix the polymer binder used in the first solid electrolyte layer with an inert solvent to obtain a first glue solution;

[0018] S2: Mix the first glue solution, the hydride solid electrolyte, and the inert solvent, coat the mixture on a substrate, and dry to form the first solid electrolyte layer;

[0019] S3: Mix the polymer binder used in the second solid electrolyte layer with an inert solvent to obtain a second adhesive solution.

[0020] S4: Mix the second adhesive solution, the halide solid electrolyte, and the inert solvent, coat the mixture on the first solid electrolyte layer, and dry it to obtain a double-layer solid electrolyte membrane.

[0021] Preferably, in steps S1 to S4, the inert solvent includes at least one of toluene, p-xylene, 1,3,5-trimethylbenzene, chlorobenzene, n-hexane, n-heptane, dichloromethane, and dichloroethane; the inert solvents in steps S1 to S4 can be the same or different.

[0022] Preferably, in step S2, the substrate is a copper foil, an aluminum foil, a stainless steel foil, a polyethylene terephthalate (PET) substrate, a polyethylene (PE) substrate, a polyimide (PI) substrate, a polytetrafluoroethylene (PTFE) substrate, or a release paper.

[0023] Preferably, in steps S2 and S4, the drying process includes hot air drying and vacuum drying.

[0024] In a third aspect, the present invention provides a all-solid-state battery, including the double-layer solid electrolyte membrane, a positive electrode, and a negative electrode; the first solid electrolyte layer is in contact with the negative electrode, and the second solid electrolyte layer is in contact with the positive electrode.

[0025] Preferably, the active material of the negative electrode includes at least one of silicon, silicon monoxide, silicon dioxide, aluminum-silicon alloy, lithium metal, lithium-indium alloy, lithium-tin alloy, and lithium-aluminum alloy.

[0026] Further, the active material of the negative electrode includes at least one of silicon, aluminum-silicon alloy, lithium metal, and lithium-indium alloy.

[0027] Preferably, the active material of the positive electrode includes at least one of lithium cobaltate, lithium manganate, nickel cobalt manganese (NCM) ternary material, nickel cobalt aluminum (NCA) ternary material, lithium iron phosphate, lithium manganese iron phosphate, sulfur, selenium, iron sulfide, and sulfurized polyacrylonitrile.

[0028] Further, the active material of the positive electrode includes at least one of lithium cobaltate, nickel cobalt manganese (NCM) ternary material, lithium manganese iron phosphate, sulfur, and sulfurized polyacrylonitrile.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) The present invention uses a specific first solid electrolyte layer and a second solid electrolyte layer to form a double-layer solid electrolyte membrane, which can enable good interfacial stability between the solid electrolyte and the positive and negative electrodes, thereby endowing the solid-state battery with higher Coulomb efficiency and cycle stability.

[0031] (2)The present invention uses Li 7-a P(BH 4 ) a S 6-a and / or Li 7-a-b P(BH 4 ) a S 6-a-b X b as the hydride solid electrolyte, which can reduce the interfacial side reactions between the first and second solid electrolyte layers, thereby improving the Coulomb efficiency and cycle stability of the solid-state battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic structural diagram of a all-solid-state battery in the present invention.

[0033] The reference numerals are: positive current collector 1, positive electrode 2, double-layer solid electrolyte film 3, second solid electrolyte layer 31, first solid electrolyte layer 32, negative electrode 4, negative current collector 5. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention will be further described below in conjunction with embodiments.

[0035] First, the present invention relates to a double-layer solid electrolyte film, comprising a first solid electrolyte layer and a second solid electrolyte layer that are superposed on each other; the first solid electrolyte layer comprises a hydride solid electrolyte, and the second solid electrolyte layer comprises a halide solid electrolyte; the hydride solid electrolyte comprises Li 7-a P(BH 4 ) a S 6-a and / or Li 7-a-b P(BH 4 ) a S 6-a- b X b , where X is a halogen, 0 < a ≤ 2, 0 < b < 2.

[0036] In some specific embodiments, in the Li 7-a-b P(BH 4 ) a S 6-a-b X b , X is at least one of F, Cl, and I.

[0037] In some specific embodiments, the halide solid electrolyte comprises Li c MZ d, where M is at least one of Zr, Hf, Sc, In, Y, La, Nb, and Gd, Z is at least one of F, Cl, and I, 1 ≤ c ≤ 8, and 2 ≤ d ≤ 10.

[0038] In some specific embodiments, in the first solid electrolyte layer, the mass ratio of the hydride solid electrolyte is not less than 90%; in the second solid electrolyte layer, the mass ratio of the halide solid electrolyte is not less than 90%.

[0039] In some specific embodiments, the first solid electrolyte layer and the second solid electrolyte layer further include a polymer binder. Optionally or preferably, the polymer binder includes at least one of styrene-butadiene rubber (SBR), nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene block copolymer (SBS), styrene-ethylene-butene-styrene block copolymer (SEBS), and polyisobutylene (PIB).

[0040] Second, the present invention relates to a method for preparing the double-layer solid electrolyte membrane, including the following steps:

[0041] S1: Mix the polymer binder used in the first solid electrolyte layer with an inert solvent to obtain a first glue solution;

[0042] S2: Mix the first glue solution, the hydride solid electrolyte, and the inert solvent, coat the mixture on a substrate, and dry it to form the first solid electrolyte layer;

[0043] S3: Mix the polymer binder used in the second solid electrolyte layer with an inert solvent to obtain a second glue solution;

[0044] S4: Mix the second glue solution, the halide solid electrolyte, and the inert solvent, coat the mixture on the first solid electrolyte layer, and dry it to obtain the double-layer solid electrolyte membrane.

[0045] In some specific embodiments, in steps S1 to S4, the inert solvent includes at least one of toluene, p-xylene, 1,3,5-trimethylbenzene, chlorobenzene, n-hexane, n-heptane, dichloromethane, and dichloroethane; the inert solvents in steps S1 to S4 may be the same or different.

[0046] In some specific embodiments, in step S2, the substrate is a copper foil, an aluminum foil, a stainless steel foil, a polyethylene terephthalate (PET) substrate, a polyethylene (PE) substrate, a polyimide (PI) substrate, a polytetrafluoroethylene (PTFE) substrate, or a release paper.

[0047] In some specific embodiments, in steps S2 and S4, the drying process includes air-blowing drying and vacuum drying.

[0048] Third, the present invention relates to a all-solid-state battery, comprising the double-layer solid electrolyte membrane, a positive electrode and a negative electrode; the first solid electrolyte layer is in contact with the negative electrode, and the second solid electrolyte layer is in contact with the positive electrode.

[0049] In some specific embodiments, the active material of the negative electrode includes at least one of silicon, silicon monoxide, silicon dioxide, aluminum-silicon alloy, lithium metal, lithium-indium alloy, lithium-tin alloy and lithium-aluminum alloy.

[0050] In some specific embodiments, the active material of the positive electrode includes at least one of lithium cobalt oxide, lithium manganese oxide, nickel cobalt manganese (NCM) ternary material, nickel cobalt aluminum (NCA) ternary material, lithium iron phosphate, lithium manganese iron phosphate, sulfur, selenium, iron sulfide and sulfurized polyacrylonitrile.

[0051] The present invention will be described below through specific examples. It should be understood that these examples are only used to illustrate the present invention and not to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be conceived by those skilled in the art are included in the present invention, and the scope of protection of the present invention is defined by the appended claims and any equivalents thereof.

[0052] Unless otherwise defined, all technical terms and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present disclosure belongs. The raw materials and equipment used in the present invention are conventional raw materials and equipment in the art and can be obtained from conventional commercial channels unless otherwise specified; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0053] Example 1

[0054] Prepare the double-layer solid electrolyte membrane of this example according to the following steps:

[0055] S1: Add SBR to p-xylene and mix evenly to obtain a first adhesive solution, where the mass ratio between SBR and p-xylene is 4:96.

[0056] S2: Add the first adhesive solution and the hydride solid electrolyte Li 5 P(BH 4 ) 2 S 4 to p-xylene and mechanically stir evenly to obtain a first electrolyte slurry, where the first adhesive solution, Li 5 P(BH 4 ) 2 S 4The mass ratio to p-xylene is 50:98:300.

[0057] S3: Coating the first electrolyte slurry on a PET substrate, drying it with forced air at 40°C for 2 h, and then drying it under vacuum at 60°C for 10 h to form a first solid electrolyte layer on the PET substrate.

[0058] S3: Adding SBR to 1,3,5-trimethylbenzene and mixing evenly to obtain a second adhesive solution, where the mass ratio of SBR to 1,3,5-trimethylbenzene is 2:98.

[0059] S4: Adding the second adhesive solution and the halide solid electrolyte Li 3 InCl 6 to 1,3,5-trimethylbenzene and stirring mechanically and evenly to obtain a second electrolyte slurry, where the mass ratio among the second adhesive solution, Li 3 InCl 6 and 1,3,5-trimethylbenzene is 100:98:100.

[0060] S5: Coating the second electrolyte slurry on the first solid electrolyte layer, drying it with forced air at 40°C for 2 h, and then drying it under vacuum at 60°C for 10 h to form a first solid electrolyte layer on the first solid electrolyte layer, obtaining a double-layer solid electrolyte membrane.

[0061] Using the double-layer solid electrolyte membrane prepared in this example to fabricate a all-solid-state battery. The structure of the all-solid-state battery is as Figure 1 shown, specifically as follows: including a positive current collector 1, a positive electrode 2, a double-layer solid electrolyte membrane 3, a negative electrode 4, and a negative current collector 5 stacked in sequence from top to bottom. Among them, the double-layer solid electrolyte membrane 3 is composed of a second solid electrolyte layer 31 and a first solid electrolyte layer 32 stacked up and down. The second solid electrolyte layer 31 is attached to the positive electrode 2, the first solid electrolyte layer 32 is attached to the negative electrode 4, the negative current collector 5 is a carbon-coated copper foil, and the positive current collector 1 is a carbon-coated aluminum foil. The all-solid-state battery of this example is prepared through the following steps:

[0062] (1) Adding nanosilicon, Li 5 P(BH 4 ) 2 S 4 , vapor-grown carbon fiber (VGCF), and SBR with a mass ratio of 70:22:5:3 to p-xylene, mixing and homogenizing, and then coating on a carbon-coated copper foil. After the p-xylene volatilizes naturally, drying it under vacuum at 90°C for 16 h to obtain a negative electrode sheet.

[0063] (2) Adding NCM811, Li 3 InCl 6, VGCF and PVDF were added to N-methylpyrrolidone (NMP). After mixing and homogenizing, it was coated on carbon-coated aluminum foil. After the natural evaporation of NMP, it was dried in vacuum at 90 °C for 12 h to obtain the positive electrode sheet.

[0064] (3) The double-layer solid electrolyte membrane was transferred to the positive electrode sheet, the PET substrate was removed, and then the negative electrode sheet was pasted on one side of the first solid electrolyte layer, followed by tab welding and vacuum packaging to obtain the all-solid-state battery.

[0065] Example 2

[0066] The double-layer solid electrolyte membrane of this example was prepared according to the following steps:

[0067] S1: PMMA was added to p-xylene and mixed evenly to obtain the first adhesive solution, where the mass ratio between PMMA and p-xylene was 8:92.

[0068] S2: The first adhesive solution and the hydride solid electrolyte Li 5 P(BH 4 ) 2 S 4 were added to p-xylene and mechanically stirred evenly to obtain the first electrolyte slurry, where the mass ratio between the first adhesive solution, Li 5 P(BH 4 ) 2 S 4 and p-xylene was 50:96:300.

[0069] S3: The first electrolyte slurry was coated on the PET substrate and dried in a blast oven at 40 °C for 2 h, and then dried in vacuum at 60 °C for 10 h to form the first solid electrolyte layer on the PET substrate.

[0070] S3: SBR was added to 1,3,5-trimethylbenzene and mixed evenly to obtain the second adhesive solution, where the mass ratio between SBR and 1,3,5-trimethylbenzene was 2:98.

[0071] S4: The second adhesive solution and the halide solid electrolyte Li 3 InCl 6 were added to 1,3,5-trimethylbenzene and mechanically stirred evenly to obtain the second electrolyte slurry, where the mass ratio between the second adhesive solution, Li 3 InCl 6 and 1,3,5-trimethylbenzene was 100:98:100.

[0072] S5: The second electrolyte slurry was coated on the first solid electrolyte layer and dried in a blast oven at 40 °C for 2 h, and then dried in vacuum at 60 °C for 10 h to form the first solid electrolyte layer on the first solid electrolyte layer to obtain the double-layer solid electrolyte membrane.

[0073] Using the double-layer solid electrolyte membrane prepared in this example, a all-solid-state battery was fabricated. The structure and preparation method of the all-solid-state battery were the same as those in Example 1.

[0074] Example 3

[0075] The double-layer solid electrolyte membrane of this example was prepared according to the following steps:

[0076] S1: SEBS was added to p-xylene and mixed evenly to obtain a first adhesive solution, where the mass ratio between SEBS and p-xylene was 4:96.

[0077] S2: The first adhesive solution and the hydride solid electrolyte Li 5 P(BH 4 ) 1.75 S 4 Cl 0.25 were added to p-xylene and mechanically stirred evenly to obtain a first electrolyte slurry, where the mass ratio among the first adhesive solution, Li 5 P(BH 4 ) 1.75 S 4 Cl 0.25 and p-xylene was 50:98:300.

[0078] S3: The first electrolyte slurry was coated on a PET substrate, dried with hot air at 40 °C for 2 h, and then dried under vacuum at 60 °C for 10 h to form a first solid electrolyte layer on the PET substrate.

[0079] S3: SEBS was added to 1,3,5-trimethylbenzene and mixed evenly to obtain a second adhesive solution, where the mass ratio between SEBS and 1,3,5-trimethylbenzene was 2:98.

[0080] S4: The second adhesive solution and the halide solid electrolyte Li 2 ZrCl 6 were added to 1,3,5-trimethylbenzene and mechanically stirred evenly to obtain a second electrolyte slurry, where the mass ratio among the second adhesive solution, Li 2 ZrCl 6 and 1,3,5-trimethylbenzene was 100:98:100.

[0081] S5: The second electrolyte slurry was coated on the first solid electrolyte layer, dried with hot air at 40 °C for 2 h, and then dried under vacuum at 60 °C for 10 h to form a first solid electrolyte layer on the first solid electrolyte layer, obtaining the double-layer solid electrolyte membrane.

[0082] Using the double-layer solid electrolyte membrane prepared in this example, a all-solid-state battery is fabricated. The structure of the all-solid-state battery is the same as that in Example 1 and is prepared through the following steps:

[0083] (1) Nano-silicon, Li 5 P(BH 4 ) 1.75 S 4 Cl 0.25 , VGCF, and SBR with a mass ratio of 70:22:5:3 are added to p-xylene. After mixing and homogenizing, it is coated on a carbon-coated copper foil. After the p-xylene naturally volatilizes, it is dried in vacuum at 90 °C for 16 h to obtain a negative electrode sheet.

[0084] (2) NCM811, Li 2 ZrCl 6 , VGCF, and PVDF with a mass ratio of 80:16:2:2 are added to NMP. After mixing and homogenizing, it is coated on a carbon-coated aluminum foil. After the NMP naturally volatilizes, it is dried in vacuum at 90 °C for 12 h to obtain a positive electrode sheet.

[0085] (3) The double-layer solid electrolyte membrane is transferred to the positive electrode sheet, the PET substrate is removed, and then the negative electrode sheet is attached to one side of the first solid electrolyte layer. After tab welding and vacuum packaging, an all-solid-state battery is obtained.

[0086] Example 4

[0087] The preparation process of the double-layer solid electrolyte membrane in this example refers to Example 1. The difference from Example 1 is only that: in the first solid electrolyte layer of this example, Li 5 P(BH 4 ) 2 S 4 is replaced with Li 5 P(BH 4 ) 1.75 S 4 Cl 0.25 . Specifically, the solid electrolyte membrane of this example is prepared according to the following steps:

[0088] S1: SBR is added to p-xylene and mixed evenly to obtain a first adhesive solution, where the mass ratio between SBR and p-xylene is 4:96.

[0089] S2: The first adhesive solution and the hydride solid electrolyte Li 5 P(BH 4 ) 1.75 S 4 Cl 0.25 are added to p-xylene and mechanically stirred evenly to obtain a first electrolyte slurry, where the first adhesive solution, Li 5 P(BH 4 )1.75 S 4 Cl 0.25 The mass ratio between S, Cl and p - xylene is 50:98:300.

[0090] S3: Coating the first electrolyte slurry on the PET substrate, drying it with forced air at 40 °C for 2 h, and then drying it under vacuum at 60 °C for 10 h to form the first solid electrolyte layer on the PET substrate.

[0091] S3: Adding SBR to 1,3,5 - trimethylbenzene and mixing evenly to obtain the second glue solution, where the mass ratio of SBR to 1,3,5 - trimethylbenzene is 2:98.

[0092] S4: Adding the second glue solution and the halide solid electrolyte Li 3 InCl 6 to 1,3,5 - trimethylbenzene and stirring mechanically and evenly to obtain the second electrolyte slurry, where the mass ratio among the second glue solution, Li 3 InCl 6 and 1,3,5 - trimethylbenzene is 100:98:100.

[0093] S5: Coating the second electrolyte slurry on the first solid electrolyte layer, drying it with forced air at 40 °C for 2 h, and then drying it under vacuum at 60 °C for 10 h to form the first solid electrolyte layer on the first solid electrolyte layer, obtaining a double - layer solid electrolyte membrane.

[0094] Using the double - layer solid electrolyte membrane prepared in this example to prepare an all - solid - state battery, the structure and preparation method of the all - solid - state battery are the same as those in Example 1.

[0095] Comparative Example 1

[0096] The preparation process of the solid electrolyte membrane in this comparative example refers to Example 1. The difference from Example 1 is only that: the solid electrolyte membrane in this comparative example is only composed of the first solid electrolyte layer and does not contain the second solid electrolyte layer. Specifically, the solid electrolyte membrane in this comparative example is prepared according to the following steps:

[0097] S1: Adding SBR to p - xylene and mixing evenly to obtain a glue solution, where the mass ratio of SBR to p - xylene is 4:96.

[0098] S2: Adding the glue solution and the hydride solid electrolyte Li 5 P(BH 4 ) 2 S 4 to p - xylene and stirring mechanically and evenly to obtain an electrolyte slurry, where the mass ratio among the glue solution, Li 5 P(BH 4 ) 2 S4 The mass ratio to p-xylene is 50:98:300.

[0099] S3: Coating the electrolyte slurry on a PET substrate, drying it with hot air at 40 °C for 2 h, and then drying it under vacuum at 60 °C for 10 h to form a solid electrolyte layer on the PET substrate, obtaining a solid electrolyte membrane.

[0100] Using the double-layer solid electrolyte membrane prepared in this comparative example to prepare an all-solid-state battery. The structure and preparation method of the all-solid-state battery are only different from those of Example 1 in that: replacing the double-layer solid electrolyte membrane with the solid electrolyte membrane in this comparative example, and attaching the two sides of the solid electrolyte membrane to the positive electrode and the negative electrode respectively.

[0101] Comparative Example 2

[0102] The preparation process of the solid electrolyte membrane in this comparative example refers to Example 1, and the difference from Example 1 is only that: the solid electrolyte membrane in this comparative example is only composed of the second solid electrolyte layer and does not contain the first solid electrolyte layer. Specifically, the solid electrolyte membrane in this comparative example is prepared according to the following steps:

[0103] S1: Adding SBR to 1,3,5-trimethylbenzene, mixing evenly to obtain a glue solution, where the mass ratio of SBR to 1,3,5-trimethylbenzene is 2:98.

[0104] S2: Adding the glue solution and the halide solid electrolyte Li 3 InCl 6 to 1,3,5-trimethylbenzene, and mechanically stirring evenly to obtain an electrolyte slurry, where the mass ratio of the glue solution, Li 3 InCl 6 and 1,3,5-trimethylbenzene is 100:98:100.

[0105] S3: Coating the electrolyte slurry on a PET substrate, drying it with hot air at 40 °C for 2 h, and then drying it under vacuum at 60 °C for 10 h to form a solid electrolyte layer on the PET substrate, obtaining a solid electrolyte membrane.

[0106] Using the double-layer solid electrolyte membrane prepared in this comparative example to prepare an all-solid-state battery. The structure and preparation method of the all-solid-state battery are only different from those of Example 1 in that: replacing the double-layer solid electrolyte membrane with the solid electrolyte membrane in this comparative example, and attaching the two sides of the solid electrolyte membrane to the positive electrode and the negative electrode respectively.

[0107] Comparative Example 3

[0108] The preparation process of the double-layer solid electrolyte membrane in this comparative example refers to Example 1, and the difference from Example 1 is only that: in the first solid electrolyte layer of this comparative example, Li 5 P(BH4 ) 2 S 4 was replaced with LiBH 4 . Specifically, the solid electrolyte membrane of this comparative example was prepared according to the following steps:

[0109] S1: Add SBR to p-xylene and mix evenly to obtain a first glue solution, where the mass ratio between SBR and p-xylene is 4:96.

[0110] S2: Add the first glue solution and the hydride solid electrolyte LiBH 4 to p-xylene and stir mechanically until evenly mixed to obtain a first electrolyte slurry, where the mass ratio among the first glue solution, LiBH 4 and p-xylene is 50:98:300.

[0111] S3: Coat the first electrolyte slurry on a PET substrate, dry it in a blast dryer at 40 °C for 2 h, and then dry it under vacuum at 60 °C for 10 h to form a first solid electrolyte layer on the PET substrate.

[0112] S3: Add SBR to 1,3,5-trimethylbenzene and mix evenly to obtain a second glue solution, where the mass ratio between SBR and 1,3,5-trimethylbenzene is 2:98.

[0113] S4: Add the second glue solution and the halide solid electrolyte Li 3 InCl 6 to 1,3,5-trimethylbenzene and stir mechanically until evenly mixed to obtain a second electrolyte slurry, where the mass ratio among the second glue solution, Li 3 InCl 6 and 1,3,5-trimethylbenzene is 100:98:100.

[0114] S5: Coat the second electrolyte slurry on the first solid electrolyte layer, dry it in a blast dryer at 40 °C for 2 h, and then dry it under vacuum at 60 °C for 10 h to form a first solid electrolyte layer on the first solid electrolyte layer, obtaining a double-layer solid electrolyte membrane.

[0115] Use the double-layer solid electrolyte membrane prepared in this comparative example to prepare an all-solid-state battery. The structure and preparation method of the all-solid-state battery are the same as those in Example 1.

[0116] Comparative Example 4

[0117] The preparation process of the double-layer solid electrolyte membrane in this comparative example refers to Example 1. The difference from Example 1 is only that: in the first solid electrolyte layer of this comparative example, Li 5 P(BH 4 ) 2 S 4 was replaced with Li(BH4 ) 0.75 I 0.25 Specifically, the solid electrolyte membrane of this comparative example was prepared according to the following steps:

[0118] S1: Add SBR to p-xylene and mix evenly to obtain a first adhesive solution, where the mass ratio between SBR and p-xylene is 4:96.

[0119] S2: Add the first adhesive solution and the hydride solid electrolyte Li(BH 4 ) 0.75 I 0.25 to p-xylene and stir mechanically until evenly mixed to obtain a first electrolyte slurry, where the mass ratio among the first adhesive solution, Li(BH 4 ) 0.75 I 0.25 and p-xylene is 50:98:300.

[0120] S3: Coat the first electrolyte slurry on a PET substrate, dry it in a blast dryer at 40 °C for 2 h, and then dry it twice in vacuum at 60 °C for 10 h to form a first solid electrolyte layer on the PET substrate.

[0121] S3: Add SBR to 1,3,5-trimethylbenzene and mix evenly to obtain a second adhesive solution, where the mass ratio between SBR and 1,3,5-trimethylbenzene is 2:98.

[0122] S4: Add the second adhesive solution and the halide solid electrolyte Li 3 InCl 6 to 1,3,5-trimethylbenzene and stir mechanically until evenly mixed to obtain a second electrolyte slurry, where the mass ratio among the second adhesive solution, Li 3 InCl 6 and 1,3,5-trimethylbenzene is 100:98:100.

[0123] S5: Coat the second electrolyte slurry on the first solid electrolyte layer, dry it in a blast dryer at 40 °C for 2 h, and then dry it twice in vacuum at 60 °C for 10 h to form a first solid electrolyte layer on the first solid electrolyte layer, obtaining a double-layer solid electrolyte membrane.

[0124] Using the double-layer solid electrolyte membrane prepared in this comparative example, a all-solid-state battery was fabricated. The structure and preparation method of the all-solid-state battery were the same as those in Example 1.

[0125] Comparative Example 5

[0126] The preparation process of the double-layer solid electrolyte membrane in this comparative example referred to Example 1. The difference from Example 1 was only that: in the first solid electrolyte layer of this comparative example, Li 5 P(BH 4 )2 S 4 was replaced with Li(BH 4 ) 0.75 Cl 0.25 . Specifically, the solid electrolyte membrane of this comparative example was prepared according to the following steps:

[0127] S1: Add SBR to p-xylene and mix evenly to obtain the first glue solution, where the mass ratio between SBR and p-xylene is 4:96.

[0128] S2: Add the first glue solution and the hydride solid electrolyte Li(BH 4 ) 0.75 Cl 0.25 to p-xylene and stir mechanically until evenly mixed to obtain the first electrolyte slurry, where the mass ratio among the first glue solution, Li(BH 4 ) 0.75 Cl 0.25 and p-xylene is 50:98:300.

[0129] S3: Coat the first electrolyte slurry on a PET substrate, dry it with hot air at 40°C for 2 h, and then dry it twice in vacuum at 60°C for 10 h, thereby forming a first solid electrolyte layer on the PET substrate.

[0130] S3: Add SBR to 1,3,5-trimethylbenzene and mix evenly to obtain the second glue solution, where the mass ratio between SBR and 1,3,5-trimethylbenzene is 2:98.

[0131] S4: Add the second glue solution and the halide solid electrolyte Li 3 InCl 6 to 1,3,5-trimethylbenzene and stir mechanically until evenly mixed to obtain the second electrolyte slurry, where the mass ratio among the second glue solution, Li 3 InCl 6 and 1,3,5-trimethylbenzene is 100:98:100.

[0132] S5: Coat the second electrolyte slurry on the first solid electrolyte layer, dry it with hot air at 40°C for 2 h, and then dry it twice in vacuum at 60°C for 10 h, thereby forming a first solid electrolyte layer on the first solid electrolyte layer to obtain a double-layer solid electrolyte membrane.

[0133] Using the double-layer solid electrolyte membrane prepared in this comparative example, a all-solid-state battery was prepared. The structure and preparation method of the all-solid-state battery were the same as those in Example 1.

[0134] Test Example

[0135] The long-cycle performance of the all-solid-state batteries prepared in each of the examples and comparative examples was tested under the following conditions: temperature of 60 °C, current of 0.1 C, and pressure of 10 MPa. The test results of the long-cycle performance are shown in Table 1.

[0136] Table 1 Test Results of the Long-Cycle Performance of All-Solid-State Batteries

[0137]

[0138] Analyzing the test results in Table 1, the following conclusions can be drawn:

[0139] (1) Comparing Example 1, Comparative Example 1, and Comparative Example 2, it can be shown that compared with using a single type of solid electrolyte, the present invention uses a double-layer solid electrolyte membrane composed of a hydride solid electrolyte and a halide solid electrolyte, which can improve the Coulombic efficiency and cycle stability of the battery. The reason for the analysis is as follows: The hydride solid electrolyte has good low-potential stability and anode stability, but is easily decomposed at high potentials. The halide solid electrolyte has good high-potential stability and cathode stability, but is easily reduced at low potentials. Therefore, after forming the double-layer structure of the present invention, the solid electrolyte membrane has good interfacial stability at both the positive and negative electrode interfaces.

[0140] (2) Comparing Example 1, Example 4, and Comparative Example 3, it can be shown that compared with using LiBH 4 , when the hydride solid electrolyte uses Li 5 P(BH 4 ) 2 S 4 or Li 5 P(BH 4 ) 1.75 S 4 Cl 0.25 , the battery can have higher Coulombic efficiency and cycle stability. The reason for the analysis is as follows: In Li 5 P(BH 4 ) 2 S 4 and Li 5 P(BH 4 ) 1.75 S 4 Cl 0.25 , the double substitution of P and S can reduce the density of hydride anions in the unit cell, thereby enhancing the crystal structure stability, weakening the reducibility of the electrolyte, and making the hydride solid electrolyte and the halide solid electrolyte have better compatibility. Therefore, it can reduce the interfacial side reactions between the first and second solid electrolyte layers caused by the strong reducibility of hydride anions and the high-valent metal ions in the halide solid electrolyte.

[0141] (3) Comparing Example 1, Example 4, Comparative Example 4 and Comparative Example 5, it can be shown that compared with using Li(BH 4 ) 0.75 I 0.25 and Li(BH 4 ) 0.75 Cl 0.25 , when the hydride solid electrolyte uses Li 5 P(BH 4 ) 2 S 4 or Li 5 P(BH 4 ) 1.75 S 4 Cl 0.25 , the battery can have higher Coulomb efficiency and cycling stability. The reason for the analysis is as follows: Although the substitution of halogen ions can also reduce the density of hydride anions in the hydride electrolyte unit cell, compared with Li(BH 4 ) 0.75 I 0.25 , Li(BH 4 ) 0.75 Cl 0.25 which only uses halogen ion substitution, the introduction of P and S double substitution in Li 5 P(BH 4 ) 2 S 4 , Li 5 P(BH 4 ) 1.75 S 4 Cl 0.25 can form PS 4 3- anions in the crystal structure. The PS 4 - anions and BH 4 - anions have the same tetrahedral structure, and are larger in volume, higher in charge number, and more stable in anion configuration. Therefore, they can more effectively improve the crystal structure stability, weaken the reducibility of the electrolyte, and thus better improve the interfacial compatibility between the double-layer electrolytes.

[0142] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. An all-solid-state battery, characterized in that: The invention comprises a double-layer solid electrolyte membrane, a positive electrode and a negative electrode; the double-layer solid electrolyte membrane comprises a first solid electrolyte layer and a second solid electrolyte layer stacked on each other, the first solid electrolyte layer is in contact with the negative electrode, and the second solid electrolyte layer is in contact with the positive electrode; the first solid electrolyte layer comprises a hydride solid electrolyte, and the second solid electrolyte layer comprises a halide solid electrolyte; the hydride solid electrolyte comprises Li 7-a P(BH4) a S 6-a and / or Li 7-a-b P(BH4) a S 6-a-b X b , where X is a halogen, 0 <a≤2,0<b<2。 2. The all-solid-state battery according to claim 1, characterized in that: The halide solid electrolyte includes Li c Z d , wherein M is at least one of Zr, Hf, Sc, In, Y, La, Nb and Gd, Z is at least one of F, Cl and I, 1≤c≤8, 2≤d≤10.

3. The all-solid-state battery according to claim 1, characterized in that: The Li 7-a-b P(BH4) a S 6-a-b X b wherein X is at least one of F, Cl and I.

4. The all-solid-state battery according to claim 1, characterized in that: In the first solid electrolyte layer, the mass proportion of the hydride solid electrolyte is not less than 90%; in the second solid electrolyte layer, the mass proportion of the halide solid electrolyte is not less than 90%.

5. The all-solid-state battery according to any one of claims 1 to 4, characterized in that: The first solid electrolyte layer and the second solid electrolyte layer further include a polymer binder.

6. A method for preparing an all-solid-state battery according to claim 5, characterized in that: The following steps are involved: S1: mixing the polymer binder used in the first solid electrolyte layer with an inert solvent to obtain a first glue solution; S2: mixing the first glue, the hydride solid electrolyte and the inert solvent, coating the mixture on the substrate, and drying the mixture to form a first solid electrolyte layer; S3: mixing the polymer binder used in the second solid electrolyte layer with an inert solvent to obtain a second glue solution; S4: mixing the second glue solution, the halide solid electrolyte and the inert solvent, coating the mixture on the first solid electrolyte layer, and drying the mixture to obtain a double-layer solid electrolyte membrane; S5: Make a double-layer solid electrolyte membrane, positive electrode and negative electrode into an all-solid-state battery.

7. The preparation method according to claim 6, characterized in that: In steps S1 to S4, the inert solvent includes at least one of toluene, p-xylene, 1,3,5-trimethylbenzene, chlorobenzene, n-hexane, n-heptane, dichloromethane and dichloroethane.

8. The preparation method according to claim 6, characterized in that: In step S2, the substrate is copper foil, aluminum foil, stainless steel foil, PET substrate, PE substrate, PI substrate, PTFE substrate or release paper.

9. The preparation method according to claim 6, characterized in that: In steps S2 and S4, the drying process includes air drying and vacuum drying.

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