Solid electrolyte with multi-layer coating structure, preparation method of solid electrolyte and battery

Abstract

The embodiment of the invention provides a solid electrolyte with a multilayer coating structure, a solid electrolyte preparation method and a battery. The solid electrolyte with the multilayer coating structure comprises an inner core, a first coating layer coating the surface of the inner core and a second coating layer coating the surface of the first coating layer. The chemical general formula of the inner core is Li < 6-a > PS < 5-a > X < 1 + a >, the chemical general formula of the first coating layer is Li < 2 + b-3c > McOXb, and the chemical formula of the second coating layer is B2O3. Wherein X is at least one of F, Cl, Br and I, M is at least two of Al, La, Cr, Y, Yb, Gd and Ga, the value range of a is more than or equal to 0 and less than or equal to 2, the value range of b is more than or equal to 1 and less than or equal to 7, and the value range of c is more than or equal to 0.5 and less than or equal to 3. The solid electrolyte with the multilayer coating structure does not need to be subjected to secondary refining treatment, so that the ionic conductivity is improved.

Description

Technical Field

[0001] This application relates to the field of solid-state battery technology, and in particular to a multilayer coated solid electrolyte, a method for preparing the solid electrolyte, and a battery. Background Technology

[0002] Among the many key parameters affecting electrolyte performance, particle size is a crucial indicator. However, solid electrolytes prepared by high-temperature calcination often suffer from excessively large particle sizes. Larger particle sizes make it difficult to construct continuous three-dimensional lithium-ion transport channels and are also detrimental to the fabrication of ultra-thin, dense, and defect-free electrolyte membranes. Therefore, refining the electrolyte particle size is a major technical challenge.

[0003] Currently, the mainstream methods for refining electrolyte particle size are mainly divided into two categories: dry refining and wet refining. Dry refining primarily involves applying high-frequency impact, collision, and shear forces directly to the calcined electrolyte mass using equipment such as planetary ball mills, air jet mills, and stirred mills. This causes large crystal particles to cleave and break down, gradually reducing them to the target particle size. Wet refining involves first mixing the coarse calcined electrolyte powder with anhydrous inert solvent to prepare a uniformly dispersed slurry. Then, using equipment such as sand mills and wet ball mills, the particles in the slurry are ultra-finely crushed by the shearing and collision effects of the grinding media. After refining, solid-liquid separation and vacuum drying are performed to remove the solvent, ultimately yielding ultrafine electrolyte powder.

[0004] However, both of the above methods will cause irreversible degradation of the intrinsic properties of solid electrolytes, resulting in a decrease in electrolyte ionic conductivity. Summary of the Invention

[0005] This application provides a multilayer coated solid electrolyte, a method for preparing the solid electrolyte, and a battery, in order to achieve the technical effect of improving ionic conductivity.

[0006] In a first aspect, embodiments of this application provide a multilayer coated solid electrolyte, comprising: a core, a first coating layer covering the surface of the core, and a second coating layer covering the surface of the first coating layer.

[0007] The general chemical formula of the core is Li 6-a PS 5-a X 1+a The chemical formula of the first coating layer is Li (2+b-3c) M c OX b The chemical formula of the second coating layer is B2O3.

[0008] Wherein, X is at least one of F, Cl, Br, and I, M is at least two of Al, La, Cr, Y, Yb, Gd, and Ga, the value of a is 0 ≤ a ≤ 2, the value of b is 1 ≤ b ≤ 7, the value of c is 0.5 ≤ c ≤ 3, the mass of the first coating layer is 0.1% to 20% of the mass of the core, and the mass of the second coating layer is 1% to 20% of the mass of the core.

[0009] The multilayer coated solid electrolyte, as measured by X-ray diffraction, exhibited diffraction peaks at 2θ values ​​of 27.5°±0.5°, 29°±0.5°, and 35°±0.5°. The X-ray diffraction test conditions were: CuKα radiation, λ=1.54178Å, tube voltage 40kV, tube current 40mA, in-situ sealed test, 2θ test range 10°~80°, scan rate 5° / min, and step size 0.02°.

[0010] Secondly, embodiments of this application provide a method for preparing a solid electrolyte. The method is used to prepare a multilayer coated solid electrolyte as described in the first aspect. The method includes: weighing and mixing a lithium source, a sulfur source, a phosphorus source, an M source, an oxygen source, and a compound containing element B according to the corresponding stoichiometric ratio of the chemical formula of the multilayer coated solid electrolyte to obtain a mixed precursor.

[0011] The mixed precursor was subjected to high-temperature calcination in an inert atmosphere to obtain the multilayer coated solid electrolyte.

[0012] In one possible implementation, the lithium source is Li₂O, Li₂O₂, Li₂S, LiOH, LiCl·H₂O, LiX, At least one of them.

[0013] In one possible implementation, the sulfur source is Li2S, P2S5, or P4S. 10 At least one of elemental S.

[0014] In one possible implementation, the phosphorus source is P2S5 or P4S. 10 At least one of elemental P.

[0015] In one possible implementation, the M source is at least one selected from AlX3, AlX3·6H2O, LaX3, YX, YX3·6H2O, YbX3, CrX3, GdCl3, and GaCl3.

[0016] In one possible implementation, the oxygen source is at least one of P2O5, Li2O, Li2O2, LiOH, LiCl·H2O, AlX3·6H2O, and YX3·6H2O.

[0017] In one possible implementation, the compound containing element B is B2O3, Li3BO3, or... , , , , , , At least one of them.

[0018] In one possible implementation, the holding temperature for the high-temperature calcination treatment is 200–600°C, and the holding time is 4–24 hours.

[0019] Thirdly, embodiments of this application provide a solid-state battery, including: a positive electrode, a negative electrode, and a solid electrolyte with a multilayer coating structure.

[0020] The multilayer coated solid electrolyte is a multilayer coated solid electrolyte as described in the first aspect, or a multilayer coated solid electrolyte prepared by the solid electrolyte preparation method described in the second aspect and / or various possible embodiments of the second aspect.

[0021] The multilayer coated solid electrolyte, its preparation method, and battery provided in this application embodiment are described below. The multilayer coated solid electrolyte, through a hierarchical structure design of a core, a first coating layer, and a second coating layer, utilizes the molten liquid phase formed by the second coating layer (B2O3) during high-temperature calcination to encapsulate and pin the core grains, fundamentally suppressing abnormal grain growth. This avoids the conductivity degradation problem caused by grain refinement processes without requiring additional refinement treatment. Simultaneously, the first coating layer broadens the electrochemical window of the solid electrolyte, combined with the intrinsic high lithium-ion conductivity of the core, balancing particle size controllability and core ion conductivity. This significantly improves the air stability and structural uniformity of the solid electrolyte, overcoming the inherent shortcomings of traditional sulfide electrolytes. Attached Figure Description

[0022] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0023] Figure 1 This is a schematic flowchart of the solid electrolyte preparation method provided in this application.

[0024] Figure 2The X-ray diffraction (XRD) spectra of Comparative Example 1 and Examples 7 and 18 provided for embodiments of this application.

[0025] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0026] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this application as detailed in the appended claims.

[0027] First, the application scenarios involved in this application will be explained.

[0028] With the rapid development of the electric vehicle and large-scale energy storage markets, the industry has placed more stringent demands on the energy density, safety, and cost control of lithium-ion batteries. Traditional liquid lithium-ion batteries, using organic liquid electrolytes, not only suffer from inherent safety hazards such as electrolyte leakage, flammability, explosiveness, and poor thermal stability, but their energy density is also approaching its theoretical limit. In contrast, all-solid-state batteries, by replacing liquid electrolytes with solid electrolytes, address the safety concerns of liquid batteries. They are also compatible with high-capacity lithium metal anodes and high-voltage cathode materials, potentially achieving a leap forward in battery energy density. With its core advantages of high safety, high energy density, and wide temperature range adaptability, all-solid-state batteries are widely recognized as the core development direction for next-generation electrochemical energy storage technology.

[0029] In all-solid-state battery systems, the solid electrolyte is the core component, and its physicochemical properties directly determine the overall electrochemical performance of the battery. Among the many key parameters affecting electrolyte performance, particle size is a crucial indicator. Particle size influences the macroscopic electrochemical performance of all-solid-state batteries by regulating the electrolyte's microstructure, ionic conductivity, interfacial contact characteristics, mechanical properties, and electrochemical stability.

[0030] However, solid electrolytes prepared by high-temperature calcination often have the problem of large particle size. If they are directly applied to composite electrodes, the large particle size will result in insufficient effective contact area between the electrolyte particles and the active material, making it difficult to construct a continuous three-dimensional lithium-ion transport channel, and ultimately preventing the active material from fully realizing its capacity and rate performance. In the preparation of electrolyte membranes, large-particle electrolytes are also not conducive to the preparation of ultra-thin, dense, and defect-free electrolyte membranes, thus restricting the improvement of the energy density of all-solid-state batteries.

[0031] To address the performance bottlenecks caused by large particle sizes, current mainstream methods for refining electrolyte particle size are mainly divided into two categories: dry refining and wet refining. Dry refining primarily involves applying high-frequency impact, collision, and shear forces directly to the calcined electrolyte mass using equipment such as planetary ball mills, air jet mills, and stirred mills. This causes large crystal particles to cleave and break down, gradually reducing them to the target particle size. However, dry refining easily leads to an increase in crystal defects in the material, and can even cause well-crystallized powders to become amorphous, resulting in a decrease in ionic conductivity. Furthermore, the final product has a wide particle size distribution, making it difficult to prepare submicron-sized and smaller ultrafine particles. Wet refining primarily involves first mixing the calcined coarse electrolyte powder with anhydrous inert solvent to prepare a uniformly dispersed slurry. Then, using equipment such as sand mills and wet ball mills, the particles in the slurry are ultrafinely broken down by the shearing and collision effects of the grinding media. After refining, solid-liquid separation and vacuum drying are performed to remove the solvent, ultimately yielding ultrafine electrolyte powder. However, wet refining requires the introduction of organic solvents, which can easily degrade the performance of solid electrolytes. Furthermore, both the pretreatment and dehydration process of the solvent, and the embedding of solvent molecules into the electrolyte lattice and adsorption on the particle surface after refining, will further reduce the electrochemical performance of the electrolyte.

[0032] In summary, dry refining relies on high-intensity mechanical force to break particles, which introduces a large number of lattice defects and dislocations, and may even cause local amorphization, thereby blocking the lithium-ion conduction pathway. In wet refining, solvent molecules are easily embedded in the lattice and irreversibly adsorbed on the particle surface, which also damages the ion transport network. Both methods lead to a decrease in the ionic conductivity of the electrolyte.

[0033] Based on the aforementioned technical problems, the technical concept of this application is as follows: During the research of sulfide solid electrolytes, the inventors found that electrolytes prepared by high-temperature calcination generally have a large particle size. To adapt to battery applications, a secondary refinement process using dry or wet methods is necessary. However, this refinement process inevitably introduces lattice defects and triggers solvent side reactions, ultimately leading to an irreversible decrease in the intrinsic ionic conductivity of the electrolyte. Therefore, the inventors realized that to solve this problem, it is necessary to abandon the traditional approach of first calcining to large particles and then refining to change the particle size. Instead, abnormal grain growth needs to be suppressed from the source of calcination. Based on this, the inventors designed a solid electrolyte scheme with a multi-layered coating structure consisting of a core, a first coating layer, and a second coating layer. A compound containing element B forms a molten liquid phase during high-temperature calcination, which encapsulates the grains and pins grain boundaries, suppressing abnormal grain growth at its source. This eliminates the need for subsequent dry or wet refinement steps, thus avoiding the conductivity degradation problem caused by the refinement process. Simultaneously, the first coating layer broadens the electrochemical window of the electrolyte, achieving a balance between controllable particle size and preservation of core performance.

[0034] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0035] Figure 1 This is a schematic flowchart of the solid electrolyte preparation method provided in this application, as shown below. Figure 1 As shown, the method includes...

[0036] S11. According to the general chemical formula of solid electrolytes with multilayer coating structure, weigh lithium source, sulfur source, phosphorus source, M source, oxygen source and compound containing element B according to the corresponding stoichiometric ratio and mix them to obtain the mixed precursor.

[0037] The multilayer coated solid electrolyte includes a core, a first coating layer covering the surface of the core, and a second coating layer covering the surface of the first coating layer.

[0038] Specifically, the general chemical formula of the kernel is Li. 6-a PS 5-a X 1+a The range of values ​​for a is 0 ≤ a ≤ 2.

[0039] Among them, Li 6-a PS 5-a X 1+aIt is a lithium-sulfur silver-germanium ore-type sulfide solid electrolyte, a core functional material of solid-state batteries, exhibiting excellent lithium-ion conductivity at room temperature. In the multilayer coated solid electrolyte of this application, this component serves as the core of the electrolyte, undertaking the core lithium-ion transport function and providing the electrolyte with basic high ion conductivity. At the same time, it provides a stable loading substrate for the first and second coating layers, working synergistically with the two coating layers to simultaneously adapt to grain control during the calcination process while retaining the intrinsic high ion conductivity, thus solving the inherent problems of sulfide electrolytes such as abnormal grain growth, poor air stability, and narrow electrochemical window.

[0040] Specifically, the chemical formula of the first coating layer is Li (2+b-3c) M c OX b The range of values ​​for b is 1 ≤ b ≤ 7, and the range of values ​​for c is 0.5 ≤ c ≤ 3.

[0041] Among them, Li (2+b-3c) M c OX b It is a lithium-doped multi-metal oxide with excellent electrochemical oxidation stability, good lithium-ion conductivity, and structural stability, making it a core coating material suitable for sulfide electrolyte interface modification. In the multilayer coated solid electrolyte of this application, this component serves as the first coating layer on the core surface, effectively widening the electrochemical window of the sulfide electrolyte, suppressing interfacial side reactions when the electrolyte contacts the high-voltage cathode, and improving the cycle stability of the battery. Simultaneously, it can work synergistically with the second coating layer to further isolate water and oxygen, improving the air stability of the sulfide electrolyte. It also serves as a transition layer between the core and the second coating layer, avoiding the obstruction of lithium-ion transport by the insulating coating layer, thus balancing the interface modification effect with the overall ion conduction efficiency.

[0042] Specifically, the second coating layer has the chemical formula B2O3. B2O3 is a common boron oxide with a low melting point, which can melt at high temperatures to form a liquid phase. In the multilayer coated solid electrolyte of this application, B2O3, as a component of the second coating layer, can encapsulate the first coating layer during high-temperature calcination, thus pinning grain boundaries, inhibiting grain boundary migration and abnormal grain growth, thereby achieving controllable preparation of solid electrolyte particle size. Simultaneously, the B2O3 coating on the surface of the first coating layer effectively improves the air stability of the sulfide solid electrolyte, reduces its sensitivity to water and oxygen, and improves the stability of the material during use. Working synergistically with the core and the first coating layer, the solid electrolyte simultaneously possesses excellent ion conductivity, electrochemical stability, and structural uniformity.

[0043] Furthermore, the mass of the first coating layer is 0.1% to 20% of the core mass, and the mass of the second coating layer is 1% to 20% of the core mass.

[0044] Specifically, the general chemical formula of a multilayer coated solid electrolyte can be represented as Li 6-a PS 5-a X 1+a @kLi (2+b-3c) M c OX b @nB2O3, where k refers to the mass percentage of the first coating layer relative to the core, and the value of k ranges from 0.1% to 20%, and n refers to the mass percentage of the second coating layer relative to the core, and the value of n ranges from 1% to 20%.

[0045] It should be understood that the surface region of a multilayer coated solid electrolyte contains M, O, and B elements.

[0046] The aforementioned multi-layered coated solid electrolyte, through its hierarchical structure of a core, a first coating layer, and a second coating layer, utilizes the molten liquid phase formed by the second coating layer (B2O3) during high-temperature calcination to encapsulate and pin the core grains, fundamentally suppressing abnormal grain growth. This avoids the conductivity degradation caused by grain refinement processes without requiring additional refinement treatment. Simultaneously, the first coating layer broadens the electrochemical window of the solid electrolyte, combined with the inherently high lithium-ion conductivity of the core, balancing particle size controllability and core ion conductivity. This significantly improves the air stability and structural uniformity of the solid electrolyte, addressing the inherent shortcomings of traditional sulfide electrolytes.

[0047] The lithium sources include Li₂O, Li₂O₂, Li₂S, LiOH, LiCl·H₂O, and LiX. At least one of them.

[0048] Specifically, Li₂O is a highly reactive inorganic alkaline lithium oxide that can undergo solid-phase reactions with various inorganic compounds at high temperatures, providing lithium ions and oxygen to the system; Li₂O₂ is an oxidizing inorganic lithium compound that easily decomposes at high temperatures to release oxygen, providing lithium and reactive oxygen species to the system; Li₂S is an inorganic lithium sulfide salt that is hygroscopic and hydrolyzed at room temperature, but can undergo solid-phase reactions with phosphorus sulfides at high temperatures, providing lithium and sulfur to the system; LiOH is a moderately strong alkaline inorganic lithium compound that can decompose by dehydration at high temperatures, providing lithium and oxygen to the system; LiCl·H₂O is an inorganic lithium salt containing water of crystallization, easily soluble in water, and can lose its water of crystallization at high temperatures, providing lithium and chlorine to the system; LiX is a collective term for inorganic lithium salts formed by lithium and halogens, where X represents halogen elements such as fluorine, chlorine, bromine, and iodine, exhibiting good reactivity at high temperatures and providing lithium and the corresponding halogen elements to the system; It is a stable inorganic lithium salt that can decompose at high temperatures to produce lithium oxide and carbon dioxide, and can gently release lithium ions.

[0049] The sulfur sources are Li2S, P2S5, and P4S. 10 At least one of elemental S.

[0050] Specifically, P4S 10 It is an inorganic phosphorus sulfide, which is stable at room temperature and can undergo a solid-phase reaction with lithium sulfides at high temperatures, providing phosphorus and sulfur elements to the system; elemental sulfur is a non-metallic element formed from sulfur, which is stable at room temperature and can undergo a combination reaction at high temperatures, providing sulfur elements to the system.

[0051] The phosphorus sources are P2S5 and P4S. 10 At least one of elemental P.

[0052] Specifically, P2S5 is an inorganic phosphorus sulfide that readily absorbs moisture and hydrolyzes at room temperature, releasing hydrogen sulfide gas. It exhibits excellent reactivity at high temperatures and can provide phosphorus and sulfur elements to the system. Elemental P is a non-metallic element formed from phosphorus, with common allotropes including red phosphorus and white phosphorus. It can undergo combination reactions at high temperatures and can provide phosphorus elements to the system.

[0053] Wherein, the source M is at least one of AlX3, AlX3·6H2O, LaX3, YX, YX3·6H2O, YbX3, CrX3, GdCl3, and GaCl3.

[0054] Specifically, AlX3 is an inorganic metal salt formed by aluminum and halogens. It is stable at room temperature and exhibits good reactivity at high temperatures, providing aluminum and halogens to the system. AlX3·6H2O is an aluminum-based metal salt containing water of crystallization. It can lose its water of crystallization at high temperatures, providing aluminum and halogens to the system. LaX3 is an inorganic rare earth metal salt formed by lanthanum and halogens. It is chemically stable and can participate in solid-state reactions at high temperatures, providing lanthanum and halogens to the system. YX is an inorganic metal salt formed by yttrium and halogens. It has moderate reactivity and can undergo combination reactions at high temperatures, providing yttrium and halogens to the system. YX3·6H2O is a yttrium-based metal salt containing water of crystallization. YbX3 is an inorganic rare earth metal salt formed by ytterbium and halogens. It is stable and reactive at high temperatures, providing ytterbium and halogens to the system. CrX3 is an inorganic metal salt formed by chromium and halogens. It is chemically stable and can participate in solid-state reactions at high temperatures, providing chromium and halogens to the system. GdCl3 is an inorganic rare earth metal salt formed by gadolinium and chlorine. It is stable at room temperature but can react at high temperatures, providing gadolinium and chlorine to the system. GaCl3 is an inorganic metal salt formed by gallium and chlorine. It has good reactivity and can participate in solid-state reactions at high temperatures, providing gallium and chlorine to the system.

[0055] The oxygen source is at least one of P2O5, Li2O, Li2O2, LiOH, LiCl·H2O, AlX3·6H2O, and YX3·6H2O.

[0056] Specifically, P2O5 is an inorganic phosphorus oxide that is highly hygroscopic at room temperature and can participate in solid-phase reactions at high temperatures, providing phosphorus and oxygen to the system.

[0057] Among them, the compounds containing element B are B2O3, Li3BO3, , , , , , , At least one of them.

[0058] Specifically, B2O3 is an inorganic boron oxide that is glassy or white crystals at room temperature and can melt at high temperatures, providing boron and oxygen to the system; Li3BO3 is an inorganic borate that is chemically stable and can decompose at high temperatures, providing boron, lithium and oxygen to the system. It is an inorganic weak acid, which is a white crystal at room temperature. It can be dehydrated and decomposed at high temperature, and can provide boron and oxygen to the system. It is an inorganic borate containing water of crystallization. It can lose its water of crystallization and decompose at high temperatures, providing boron and oxygen to the system. It is an inorganic boron-nitrogen compound with stable chemical properties. It can decompose at high temperatures and can provide boron and nitrogen elements to the system. It is an organoboron compound that is solid at room temperature but decomposes at high temperatures, providing boron to the system. It is an organoboron compound with active chemical properties. It can decompose at high temperatures and can provide boron to the system. It is an organoboron compound that is stable, decomposes at high temperatures, and can provide boron to the system. It is an organoboron ester compound that is liquid at room temperature but decomposes at high temperatures, providing boron and oxygen to the system.

[0059] Alternatively, each raw material can be weighed individually using a precision analytical balance.

[0060] Alternatively, the raw materials can be mixed in any of the following ways.

[0061] 1. Dry ball milling: Put all raw materials into a sealed ball mill jar, add grinding balls, and then dry ball mill to mix them.

[0062] 2. Mechanical grinding and mixing: Place the raw materials in a mortar or grinder, grind and mix them thoroughly to obtain the mixed precursor.

[0063] 3. Closed high-speed vortex dry mixing: All raw materials are put into a closed mixing device, and the powder is fully collided and dispersed by the high-speed vortex airflow, so as to quickly achieve uniform mixing of multiple components.

[0064] In practical applications, the entire S11 process can be carried out in an inert atmosphere, which includes at least one of nitrogen, argon, helium and neon, to avoid the influence of the external environment on the raw materials and ensure the purity of the mixed precursor.

[0065] S12. The mixed precursors are subjected to high-temperature calcination in an inert atmosphere to obtain a multilayer coated solid electrolyte.

[0066] Among them, the high-temperature calcination treatment, by controlling the temperature and time, causes the raw materials in the mixed precursor to undergo solid-phase reaction, and synergistically form a multi-layer structure of core, first coating layer and second coating layer. At the same time, the molten liquid phase of the second coating layer containing B element compound is used to achieve in-situ grain size control.

[0067] Alternatively, the mixed precursor can be subjected to high-temperature calcination in any of the following ways.

[0068] 1. Inert atmosphere segmented calcination: The mixed precursor is placed in a tube furnace and protected by nitrogen or argon. The temperature is controlled and increased in three stages: low temperature pretreatment, medium temperature reaction, and high temperature crystallization. Dehydration, solid-phase reaction and grain shaping are completed step by step to avoid the formation of impurity phases.

[0069] 2. Microwave-assisted rapid calcination: The mixed precursor is heated in a microwave calcination furnace. The microwave dielectric heating is used to achieve uniform temperature rise, shorten the calcination time, inhibit abnormal growth of electrolyte grains, and improve structural uniformity.

[0070] 3. Constant temperature calcination in an atmospheric pressure box furnace: The mixed precursor is loaded into a sealed corundum crucible, placed in a box furnace and kept inert atmosphere, and calcined at a constant high temperature.

[0071] In practical applications, the holding temperature for high-temperature calcination treatment is 200–600℃, and the holding time is 4–24 hours.

[0072] It should be understood that the holding temperature is related to the melting point of B2O3. Since the melting point of B2O3 is approximately 450℃, in a preferred embodiment, the holding temperature can be set to 400–600℃ to ensure that B2O3 melts and forms a liquid phase, which coats the surface of the core grains, pins the grain boundaries, and inhibits grain boundary migration, thereby suppressing abnormal grain growth. The holding time can be flexibly adjusted according to the reactivity of the raw materials and the particle size requirements of the product. For example, when the reactivity of the raw materials is low, the holding time can be 12–24 hours to ensure that the solid-phase reaction proceeds fully and a stable multilayer coating structure is formed.

[0073] In practical applications, the above-mentioned heat preservation temperature and heat preservation time can ensure that the solid phase reaction of each raw material in the mixed precursor is fully carried out. This can avoid incomplete reaction and poor coating layer formation caused by excessively low temperature, and prevent abnormal grain growth and structural collapse caused by excessively high temperature. It can also allow the multi-layer coating structure to form in an orderly manner, ensuring that the grain size of the solid electrolyte is uniform and the performance is stable and controllable.

[0074] The solid electrolyte preparation method provided in this application involves first weighing and mixing lithium source, sulfur source, phosphorus source, M source, oxygen source, and a B-containing compound according to the corresponding stoichiometric ratio, based on the general chemical formula of a multilayer coated solid electrolyte, to obtain a mixed precursor. Then, the mixed precursor is subjected to high-temperature calcination in an inert atmosphere to obtain a multilayer coated solid electrolyte. In this technical solution, the inert atmosphere isolates water and oxygen to prevent raw material deterioration and promotes sufficient solid-phase reaction of each raw material. The second coating layer, B2O3, forms a molten liquid phase during high-temperature calcination, achieving encapsulation and grain boundary pinning of the core grains, fundamentally inhibiting abnormal grain growth. This avoids the conductivity degradation problem caused by the refinement process without additional refinement treatment, thus ensuring the ionic conductivity of the solid electrolyte.

[0075] In summary, this application provides a multilayer coated solid electrolyte and its preparation method, in Li 6-a PS 5- a X 1+a Introducing Li into the system (2+b-3c) M c OX b It does not significantly reduce the ionic conductivity of the sulfide electrolyte matrix, and Li (2+b-3c) M c OX b This method can enhance the oxidation resistance of multilayer coated solid electrolytes. By introducing low-melting-point B-containing compounds during the high-temperature calcination of the solid electrolyte, these compounds can melt at the high-temperature calcination temperature to form a liquid phase. The molten B₂O₃ then coats the Li₂O₃. (2+b-3c) M c OX bBy reducing solid-solid contact points on the surface, the nucleation process is no longer confined to the local solid-solid interface but tends to be homogenized throughout the liquid phase. This reduces the randomness of solid electrolyte nucleation, slows down the nucleation rate, and reduces the number of nuclei, avoiding the formation of large-particle products due to excessive nucleation points during high-temperature calcination. Simultaneously, the compound formed by boron on the electrolyte surface enhances the air stability of the multilayer coated solid electrolyte. This method can prepare multilayer coated solid electrolytes with controllable particle size without introducing additional refining processes, without reducing the intrinsic properties of the material. It balances industrial production efficiency, production cost, and product consistency, making it suitable for large-scale production applications. Applying this electrolyte to all-solid-state batteries is beneficial for achieving high energy density and high safety performance, significantly reducing the manufacturing cost of solid electrolytes, accelerating the commercialization of solid electrolytes and all-solid-state batteries, and providing technical support for the preparation of high-energy-density sulfide all-solid-state batteries.

[0076] Specifically, the aforementioned technical effects can be reflected in the following aspects.

[0077] 1) Existing Li 6-a PS 5-a X 1+a During high-temperature calcination, sulfur (S) volatilizes. This application addresses this issue by using compounds containing boron (B) to lower the calcination temperature of multilayer coated solid electrolytes, thereby reducing S loss and improving the ionic conductivity of the solid electrolyte.

[0078] 2) Existing solid electrolytes used directly after high-temperature calcination often result in insufficient capacity utilization of active materials when applied to electrodes, making it difficult to prepare ultra-thin electrolyte films and hindering the improvement of energy density in all-solid-state batteries. Dry refining yields electrolytes with a wide particle size distribution, making it difficult to obtain submicron-sized electrolyte materials, and the refining process easily reduces electrolyte crystallinity. Wet refining, on the other hand, allows solvents to easily embed into the electrolyte lattice or adsorb onto the electrolyte surface, making complete removal impossible and affecting the overall performance of the multilayer-coated solid electrolyte. This application utilizes a boron-containing compound to form a molten liquid phase during high-temperature calcination, encapsulating grains and pinning grain boundaries, thus inhibiting abnormal grain growth at its source. This eliminates the need for subsequent dry or wet refining steps, avoiding conductivity degradation and other problems associated with the refining process. Applying the multilayer-coated solid electrolyte to the electrode allows for the construction of a uniform and dense ion-conducting network on the surface of the active material, achieving thinner electrolyte films, effectively reducing solid-solid interface contact resistance, and fully utilizing the electrochemical performance of the battery materials.

[0079] 3) Li 6-a PS 5-a X 1+aThe air stability of the electrolyte is poor. In addition to improving its oxidation resistance, by introducing compounds containing element B, on the one hand, the electrolyte grains can be coated during high-temperature calcination to avoid the formation of large particle size. On the other hand, the second coating layer formed can improve the air stability of the multi-layer coated solid electrolyte.

[0080] 4) Li 6-a PS 5-a X 1+a The electrochemical window is narrow, and the cycling performance at high voltage is poor. This can be addressed by introducing Li... (2+b-3c) M c OX b It can increase the oxidation potential of multilayer coated solid electrolytes and raise the electrochemical window to above 4.0V.

[0081] In practical applications, the multilayer coated solid electrolyte exhibits diffraction peaks at 2θ values ​​of 27.5°±0.5°, 29°±0.5°, and 35°±0.5° as determined by X-ray diffraction. The X-ray diffraction test conditions are: CuKα radiation, λ=1.54178Å, tube voltage 40kV, tube current 40mA, in-situ sealed test, 2θ test range 10°~80°, scan rate 5° / min, and step size 0.02°.

[0082] This application also provides a solid-state battery, including a positive electrode, a negative electrode, and a solid electrolyte with a multilayer coating structure as shown in any of the above embodiments.

[0083] Next, the technical effects of the multilayer coated solid electrolyte will be illustrated through several examples and comparative examples.

[0084] Example 1

[0085] The chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.05Li 0.8 Al 0.9 La 0.1 Cl 2.2 O 0.8 .

[0086] Preparation process: P2S5, Li2S, LiCl, LiOH, AlCl3, and LaCl3 were weighed according to the corresponding stoichiometric ratio based on the chemical formula and placed in a mixer. The mixing speed was 10,000 rpm, with a mixing interval of 10 seconds and a 10-minute interval, and this process was repeated 6 times to obtain the mixed precursor. Then, it was calcined at 450℃ for 8 hours in an argon atmosphere to obtain a multilayer coated solid electrolyte.

[0087] Example 2

[0088] The preparation process is the same as in Example 1, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.1Li 0.8 Al 0.9 La 0.1 Cl 2.2 O 0.8 .

[0089] Example 3

[0090] The preparation process is the same as in Example 1, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.9 La 0.1 Cl 2.2 O 0.8 .

[0091] Example 4

[0092] The preparation process is the same as in Example 1, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.2Li 0.8 Al 0.9 La 0.1 Cl 2.2 O 0.8 .

[0093] Example 5

[0094] The preparation process is the same as in Example 1, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.25Li 0.8 Al 0.9 La 0.1 Cl 2.2 O 0.8 .

[0095] Example 6

[0096] The preparation process is the same as in Example 1, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.3Li 0.8 Al 0.9 La 0.1Cl 2.2 O 0.8 .

[0097] Example 7

[0098] The chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0. 1Y 0.1 Cl 2.2 O 0.8 .

[0099] Preparation process: P2S5, Li2S, LiCl, LiOH, AlCl3, LaCl3, and YCl3 were weighed according to the corresponding stoichiometric ratio based on the chemical formula and placed in a mixer. The mixing speed was 10,000 rpm, with a mixing interval of 10 seconds and a 10-minute interval, and this process was repeated 6 times to obtain the mixed precursor. Then, it was calcined at 450℃ for 8 hours in an argon atmosphere to obtain a multilayer coated solid electrolyte.

[0100] Example 8

[0101] The chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0.1 Ga 0.1 Cl 2.2 O 0.8 .

[0102] Preparation process: P2S5, Li2S, LiCl, LiOH, AlCl3, LaCl3, and GaCl3 were weighed according to the corresponding stoichiometric ratio based on the chemical formula and placed in a mixer. The mixing speed was 10,000 rpm, with a mixing interval of 10 seconds and a 10-minute interval, and this process was repeated 6 times to obtain the mixed precursor. Then, it was calcined at 450℃ for 8 hours in an argon atmosphere to obtain a multilayer coated solid electrolyte.

[0103] Example 9

[0104] The chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0.1 Gd 0.1 Cl2.2 O 0.8 .

[0105] Preparation process: P2S5, Li2S, LiCl, LiOH, AlCl3, LaCl3, and GdCl3 were weighed according to the corresponding stoichiometric ratio based on the chemical formula and placed in a mixer. The mixing speed was 10,000 rpm, with a mixing interval of 10 seconds and a 10-minute interval, and this process was repeated 6 times to obtain the mixed precursor. Then, it was calcined at 450℃ for 8 hours in an argon atmosphere to obtain a multilayer coated solid electrolyte.

[0106] Example 10

[0107] The chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0.1 Yb 0.1 Cl 2.2 O 0.8 .

[0108] Preparation process: P2S5, Li2S, LiCl, LiOH, AlCl3, LaCl3, and YbCl3 were weighed according to the corresponding stoichiometric ratio based on the chemical formula and placed in a mixer. The mixing speed was 10,000 rpm, with a mixing interval of 10 seconds and a 10-minute interval, and this process was repeated 6 times to obtain the mixed precursor. Then, it was calcined at 450℃ for 8 hours in an argon atmosphere to obtain a multilayer coated solid electrolyte.

[0109] Example 11

[0110] The chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0.1 Cr 0.1 Cl 2.2 O 0.8 .

[0111] Preparation process: P2S5, Li2S, LiCl, LiOH, AlCl3, LaCl3, and CrCl3 were weighed according to the corresponding stoichiometric ratio based on the chemical formula and placed in a mixer. The mixing speed was 10,000 rpm, with a mixing interval of 10 seconds and a 10-minute interval, and this process was repeated 6 times to obtain the mixed precursor. Then, it was calcined at 450℃ for 8 hours in an argon atmosphere to obtain a multilayer coated solid electrolyte.

[0112] Example 12

[0113] The chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0. 1Y 0.1 Cl 2.2 O 0.8 @0.01B2O3.

[0114] Preparation process: According to the chemical formula, P2S5, Li2S, LiCl, LiOH, AlCl3, LaCl3, YCl3, and B2O3 were weighed out according to the corresponding stoichiometric ratio and placed in a mixer. The mixing speed was 10000 rpm, with a mixing interval of 10 seconds and a 10-minute interval, and this process was repeated 6 times to obtain the mixed precursor. Then, it was calcined at 450℃ for 8 hours in an argon atmosphere to obtain a multilayer coated solid electrolyte.

[0115] Example 13

[0116] The preparation process is the same as in Example 12, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0.1 Y 0.1 Cl 2.2 O 0.8 @0.025B2O3.

[0117] Example 14

[0118] The preparation process is the same as in Example 12, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0.1 Y 0.1 Cl 2.2 O 0.8 @0.05B2O3.

[0119] Example 15

[0120] The preparation process is the same as in Example 12, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5@0.15Li 0.8 Al 0.8 La 0.1 Y 0.1 Cl 2.2 O 0.8 @0.075B2O3.

[0121] Example 16

[0122] The preparation process is the same as in Example 12, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0.1 Y 0.1 Cl 2.2 O 0.8 @0.1B2O3.

[0123] Example 17

[0124] The preparation process is the same as in Example 12, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0.1 Y 0.1 Cl 2.2 O 0.8 @0.15B2O3.

[0125] Example 18

[0126] The preparation process is the same as in Example 12, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0.1 Y 0.1 Cl 2.2 O 0.8 @0.2B2O3.

[0127] Example 19

[0128] The preparation process is the same as in Example 12, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La0.1 Y 0.1 Cl 2.2 O 0.8 @0.25B2O3.

[0129] Example 20

[0130] The preparation process is the same as in Example 12, except that the chemical formula of the multilayer coated solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 @0.15Li 0.8 Al 0.8 La 0.1 Y 0.1 Cl 2.2 O 0.8 @0.3B2O3.

[0131] Comparative Example 1

[0132] The chemical formula of the solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 .

[0133] Preparation process: P2S5, Li2S, and LiCl were weighed according to the corresponding stoichiometric ratio based on the chemical formula and placed in a mixer. The mixing speed was 10,000 rpm, with a mixing interval of 10 seconds and a 10-minute interval, and this process was repeated 6 times to obtain the precursor. Then, it was calcined at 490℃ for 16 hours in an argon atmosphere to obtain the sulfide electrolyte.

[0134] Comparative Example 2

[0135] The chemical formula and preparation process are the same as those of the solid electrolyte in Comparative Example 1, except that the calcination temperature is 450℃ and the calcination time is 8h.

[0136] Comparative Example 3

[0137] Weigh 20g of the sulfide electrolyte Li synthesized in Comparative Example 1 5.5 PS 4.5 Cl 1.5 Dry refining was used to obtain the refined sulfide electrolyte X1-Li. 5.5 PS 4.5 Cl 1.5 .

[0138] Comparative Example 4

[0139] Weigh 20g of the sulfide electrolyte Li synthesized in Comparative Example 1 5.5 PS 4.5 Cl 1.5 The refined sulfide electrolyte X2-Li was obtained by wet refining.5.5 PS 4.5 Cl 1.5 .

[0140] For example, the electrolyte chemical formulas in the above embodiments and comparative examples can be represented by Table 1.

[0141] Table 1. Electrolyte chemical formulas in each example and comparative example.

[0142]

[0143] Test case

[0144] Crystal structure testing: X-ray diffraction (XRD) is a common method for testing the composition and crystal information of solid powder materials. High-energy X-rays produce specific signals when passing through a periodic material lattice. Materials with different crystal structures produce different interference signals; therefore, XRD can qualitatively and quantitatively analyze the crystal structure information of materials. This application uses the CuKα XRD diffraction mode (λ=1.54178Å), with a tube voltage and current of 40kV and 40mA, respectively. To avoid exposing the electrolyte to air, in-situ sealed testing is employed. The XRD testing range is 10°~80°, the scan rate is 5° / min, and the step size is 0.02°.

[0145] Figure 2 The XRD patterns of Comparative Example 1 and Examples 7 and 18 provided for embodiments of this application. Figure 2 As shown, the horizontal axis represents 2θ, with units of degrees (°); the vertical axis represents diffraction intensity, with units of au. Example 7, compared to Comparative Example 1, exhibits a diffraction peak at 35.5° ± 0.5°. Example 18, compared to Comparative Example 1, shows a diffraction peak after the addition of Li. (2+b-3c) M c OX b After the compound containing boron, the XRD pattern showed diffraction peaks at 27.5°±0.5° (y3 in the figure), 29°±0.5° (y2 in the figure), and 35°±0.5° (y1 in the figure).

[0146] Particle size testing: The dry laser particle size analyzer is based on the classical laser diffraction / scattering theory. By measuring the intensity of scattered light at different angles, the particle size distribution of the electrolyte can be calculated using an inversion algorithm. Specifically, D50 and D90 are used as parameters characterizing the particle size distribution. D50 is the median particle size, representing that 50% of the particles in the electrolyte are smaller than this value, and D90 is the cumulative particle size, representing that 90% of the particles in the electrolyte are smaller than this value.

[0147] For the ionic conductivity test, 150 mg of electrolyte powder was weighed and placed in a battery mold (inner diameter 10 mm), a pressure of 400 MPa was applied, and the AC impedance was tested using an electrochemical workstation. An applied voltage of 10 mV was applied in the frequency range of 1 Hz to 1 MHz, and the ionic conductivity of the electrolyte after exposure was calculated.

[0148] 4h ionic conductivity test

[0149] After completing the above ionic conductivity test and placing the electrolyte in air for 4 hours, an electrochemical workstation was used to apply an external voltage of 10mV within a frequency range of 1Hz to 1MHz to test the AC impedance and calculate the 4-hour ionic conductivity of the electrolyte.

[0150] 4-hour ionic conductivity retention rate: The 4-hour ionic conductivity retention rate is calculated using the formula: 4-hour ionic conductivity retention rate (%) = (4-hour ionic conductivity ÷ initial ionic conductivity) × 100%. Here, the initial ionic conductivity is the ionic conductivity obtained directly after the electrolyte has been compressed into tablets and has not been exposed to air for an extended period.

[0151] For example, Table 2 can be used to represent the particle size and air stability of the electrolytes prepared in each embodiment and comparative example.

[0152] Table 2. Particle size and air stability of electrolytes in each example and comparative example.

[0153]

[0154] As shown in Table 2, the particle size of Example 20 is smaller than that of Comparative Example 4, but its ionic conductivity is higher. Compared with Comparative Example 3, the particle size distribution of Examples 17-19 is relatively narrower, and their ionic conductivity is higher than that of Comparative Example 3. This is because the B-containing compound melts at high temperature and forms grain boundaries around the sulfide grains, hindering rapid grain growth and engulfing of small grains, thus reducing the particle size of the synthesized electrolyte. The electrolytes prepared in Examples 12-20 have better air stability than those in Comparative Examples 1-4. The B2O3 component on the surface of the sulfide electrolyte effectively isolates the contact between water and oxygen in the air and the electrolyte, improving the air stability of the sulfide. Compared with Comparative Example 2, Examples 1-11 show lower ionic conductivity at the same calcination temperature.

[0155] Electrochemical window testing: The electrolyte was pressurized in a 10mm diameter battery mold at 200MPa. A lithium foil was stacked on one side of the electrolyte and pressurized at 50MPa. Stainless steel current collectors were placed above and below the stack. Linear scanning voltammetry was performed with a scan range of 1.5-6.0V and a scan rate of 0.1mV / s. The oxidation potential of the electrolyte is obtained by plotting the tangent line to the oxidation peak of the test curve and intersecting it with the abscissa.

[0156] The electrolytes obtained in the above embodiments and comparative examples are mixed with positive electrode materials to form a composite positive electrode. The electrolyte is used as the electrolyte layer, and lithium metal is used as the negative electrode to assemble an all-solid-state battery. Specifically:

[0157] (1) Preparation of positive electrode sheet.

[0158] The positive electrode material, electrolyte, conductive agent (VGCF), and binder (PTFE) are mixed in a mass ratio of 80:20:2:0.5 to prepare a positive electrode film. The positive electrode film is then combined with stainless steel to form a positive electrode sheet.

[0159] (2) Lithium metal is used as the negative electrode.

[0160] (3) Preparation of solid electrolyte membrane.

[0161] An electrolyte membrane is prepared by thoroughly mixing sulfide electrolyte and binder (PTFE) at a mass ratio of 100:0.5.

[0162] Electrochemical performance tests were performed on the solid-state batteries assembled with electrolytes prepared in Examples 1-20 and Comparative Examples 1-4, including...

[0163] 1) First charge and discharge test: The solid-state battery was tested at 25℃ with a constant current of 0.1C for 1 cycle, with a voltage range of 2.7-4.3V.

[0164] 2) Long cycle test: The solid-state battery is subjected to 300 cycles of 0.1C constant current charge and discharge at 25℃, with a voltage range of 2.7-4.3V.

[0165] 3) Rate Performance Testing: The solid-state battery was tested at 25°C within its rated operating voltage window of 2.7V to 4.2V, using six charge / discharge rate gradients from low to high: 0.1C, 0.2C, 0.3C, 0.5C, 1C, and 2C. For each charge / discharge rate, five complete charge / discharge cycles were performed consecutively. The ratio of the average discharge capacity of the five cycles at each charge / discharge rate to the average discharge capacity of the five cycles at the 0.1C rate was taken as the rate capacity retention rate of the solid-state battery at that charge / discharge rate.

[0166] For example, the electrochemical performance of the electrolytes in each embodiment and comparative example can be represented by Table 3.

[0167] Table 3 Electrochemical performance of electrolytes in each example and comparative example

[0168]

[0169] As shown in Table 3, Examples 1-11 introduce Li (2+b-3a) M a OX b The electrochemical window of the electrolyte was significantly broadened afterward. In Examples 12-20, compared to the comparative examples, the Li-containing electrolyte showed improved performance during electrochemical cycling. 6-a PS 5-a X 1+a The all-solid-state battery assembled with electrolyte materials treated with element B showed higher first-discharge specific capacity, cycle life, and rate performance than the comparative example.

[0170] As can be seen from the above embodiments and comparative examples, the present invention uses Li (2+b-3c) M c OX b As the first coating layer, it covers Li 6-a PS 5-a X 1+a Surface, does not significantly reduce Li 6-a PS 5-a X 1+a This method improves the intrinsic ionic conductivity of electrolytes and significantly enhances the oxidation resistance of sulfide electrolytes. By using low-melting-point compounds containing boron and melting them under high-temperature calcination conditions, the calcination synthesis temperature of the electrolyte material can be reduced. Furthermore, the molten liquid phase can encapsulate the electrolyte grains and pin grain boundaries, effectively inhibiting abnormal grain growth and preventing large grains from engulfing smaller grains, thus allowing for precise control of the synthesized electrolyte particle size. The multilayer coated solid electrolyte prepared by this method has a smaller particle size and superior ionic conductivity compared to electrolyte materials processed by conventional dry and wet secondary refinement methods. When applied to electrodes, it can construct a uniform and dense three-dimensional ionic conductive network on the surface of the active material, significantly reducing the solid-solid interface contact impedance and enabling the controllable preparation of ultrathin, high-density electrolyte films. Assembling the aforementioned multilayer coated solid electrolyte into solid-state batteries can fully utilize the capacity characteristics of the active material, significantly improving the battery's cycle stability and rate performance. This preparation process eliminates the need for additional secondary refinement steps, effectively reducing production costs and meeting the needs of large-scale industrial production, thus facilitating the commercialization and large-scale application of high-energy-density, high-safety all-solid-state batteries.

[0171] Finally, it should be noted that other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and alterations may be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A multilayer coated solid electrolyte, characterized in that, include: The core, a first covering layer covering the surface of the core, and a second covering layer covering the surface of the first covering layer; The general chemical formula of the core is Li 6-a PS 5-a X 1+a The chemical formula of the first coating layer is Li (2+b-3c) M c OX b The chemical formula of the second coating layer is B2O3; Wherein, X is at least one of F, Cl, Br, and I; M is at least two of Al, La, Cr, Y, Yb, Gd, and Ga; the value of a ranges from 0 to a ≤ 2; the value of b ranges from 1 to b ≤ 7; the value of c ranges from 0.5 to c ≤ 3; the mass of the first coating layer is 0.1% to 20% of the core mass; and the mass of the second coating layer is 1% to 20% of the core mass. The multilayer coated solid electrolyte exhibited diffraction peaks at 2θ values ​​of 27.5°±0.5°, 29°±0.5°, and 35°±0.5° as determined by X-ray diffraction. The X-ray diffraction test conditions were: CuKα radiation, λ=1.54178Å, tube voltage 40kV, tube current 40mA, in-situ sealed test, 2θ test range 10°~80°, scan rate 5° / min, and step size 0.02°.

2. A method for preparing a solid electrolyte, characterized in that, The solid electrolyte preparation method is used to prepare the multilayer coated solid electrolyte as described in claim 1, and the solid electrolyte preparation method includes: According to the chemical formula of the solid electrolyte with the multilayer coating structure, lithium source, sulfur source, phosphorus source, M source, oxygen source and B-containing compound are weighed and mixed according to the corresponding stoichiometric ratio to obtain the mixed precursor. The mixed precursor was subjected to high-temperature calcination in an inert atmosphere to obtain the multilayer coated solid electrolyte.

3. The method for preparing a solid electrolyte according to claim 2, characterized in that, The lithium source is Li₂O, Li₂O₂, Li₂S, LiOH, LiCl·H₂O, LiX, At least one of them.

4. The method for preparing a solid electrolyte according to claim 2, characterized in that, The sulfur source is Li2S, P2S5, or P4S. 10 At least one of elemental S.

5. The method for preparing a solid electrolyte according to claim 2, characterized in that, The phosphorus source is P2S5 or P4S. 10 At least one of elemental P.

6. The method for preparing a solid electrolyte according to claim 2, characterized in that, The M source is at least one of AlX3, AlX3·6H2O, LaX3, YX, YX3·6H2O, YbX3, CrX3, GdCl3, and GaCl3.

7. The method for preparing a solid electrolyte according to claim 2, characterized in that, The oxygen source is at least one of P2O5, Li2O, Li2O2, LiOH, LiCl·H2O, AlX3·6H2O, and YX3·6H2O.

8. The method for preparing a solid electrolyte according to claim 2, characterized in that, The compounds containing element B are B2O3, Li3BO3, , , , , , , At least one of them.

9. The method for preparing a solid electrolyte according to claim 2, characterized in that, The holding temperature for high-temperature calcination is 200–600℃, and the holding time is 4–24 hours.

10. A solid-state battery, characterized in that, include: Positive electrode, negative electrode, and solid electrolyte with multilayer coating structure; The multilayer coated solid electrolyte is the multilayer coated solid electrolyte as described in claim 1, or a multilayer coated solid electrolyte prepared by the solid electrolyte preparation method as described in any one of claims 2-9.

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