Sulfide solid electrolyte and preparation method and application thereof

Abstract

The application provides a sulfide solid electrolyte and a preparation method and application thereof, and relates to the technical field of batteries.The method comprises the following steps: after a pre-acquired sulfide coarse powder is subjected to airflow crushing treatment, the sulfide coarse powder is subjected to screening treatment through a three-stage grading screen to obtain a sulfide matrix powder, the particle size distribution of the sulfide matrix powder comprises the following ranges: D 10 =1.0 μm~1.4 μm, D 50 =1.5 μm~1.9 μm and D 90 =2.0 μm~2.4 μm; then the sulfide matrix powder is added into a composite coating solution obtained according to LiF and Al2O3, in-situ composite coating reaction is performed to obtain a coating slurry, the coating slurry is subjected to temperature rising treatment and then vacuum drying to obtain a sulfide solid electrolyte comprising the sulfide matrix powder and a composite coating layer coated on the surface of the sulfide matrix powder. Through the above method, the mechanical toughness of the sulfide solid electrolyte is improved, and the ionic conductivity and the interface compatibility of the sulfide solid electrolyte are also improved.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a sulfide solid electrolyte, its preparation method, and its application. Background Technology

[0002] Compared to oxide and polymer solid electrolytes, sulfide solid electrolytes are better able to meet the application requirements of high-capacity and high-power batteries, and are currently the focus of industrialization research and development.

[0003] In existing technologies, sulfide solid electrolytes (such as Li6PS5Cl, Li7P3S) 11 Solid-state batteries are typically prepared by high-temperature solid-state methods or mechanical ball milling. However, they have poor mechanical toughness and high brittleness, which makes them prone to particle breakage and interlayer peeling due to stress during the preparation, stacking, or charge-discharge cycle of high-capacity soft-pack solid-state batteries. This leads to a sharp increase in interfacial impedance and seriously affects the battery cycle life.

[0004] In conclusion, improving the mechanical toughness of sulfide solid electrolytes is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] This application provides a sulfide solid electrolyte, its preparation method, and its application, to solve the technical problem of poor mechanical toughness of sulfide solid electrolytes in the prior art.

[0006] In a first aspect, embodiments of this application provide a sulfide solid electrolyte, comprising: a sulfide matrix powder and a composite coating layer; wherein, the sulfide matrix powder is doped with rare earth compounds, and the composite coating layer, composed of LiF and Al2O3, coats the surface of the sulfide matrix powder.

[0007] The particle size distribution of the sulfide matrix powder includes:

[0008] D 10 =1.0μm~1.4μm, D 50 =1.5μm~1.9μm and D 90 =2.0μm~2.4μm.

[0009] In one possible implementation, the rare earth compound is Nd2S3;

[0010] And / or,

[0011] The mass of the rare earth compound is 0.5% to 2% of the mass of the sulfide matrix powder.

[0012] In one possible implementation, the thickness of the composite coating layer is 15 nm to 35 nm.

[0013] Secondly, embodiments of this application provide a method for preparing a sulfide solid electrolyte, comprising:

[0014] The pre-obtained coarse sulfide powder is pulverized by air jet milling and then sieved through a three-stage classifying sieve to obtain the sulfide-based powder. The mesh size of the three-stage classifying sieve decreases sequentially along the sieving direction, and the particle size distribution of the sulfide-based powder includes: D 10 =1.0μm~1.4μm, D 50 =1.5μm~1.9μm and D 90 =2.0μm~2.4μm;

[0015] The sulfide matrix powder is added to a composite coating solution obtained from LiF and Al2O3, and a coating slurry is obtained through an in-situ composite coating reaction.

[0016] The coating slurry was heated and then vacuum dried to obtain the sulfide solid electrolyte.

[0017] In one possible implementation, the method further includes:

[0018] After mixing Li2S, P2S5, and LiCl, a rare earth compound and a dispersant are added to obtain a precursor slurry; wherein the rare earth compound is Nd2S3 and the dispersant is anhydrous cyclohexane.

[0019] The precursor slurry was ball-milled, vacuum-dried, and then sintered at a constant temperature in an inert gas environment. After grinding and sieving, coarse sulfide powder was obtained.

[0020] In one possible implementation, the step of adding the sulfide matrix powder to a composite coating solution obtained from LiF and Al2O3, and then performing an in-situ composite coating reaction to obtain a coating slurry, includes:

[0021] After mixing LiF and Al2O3, anhydrous cyclohexane was added to obtain the composite coating solution;

[0022] The sulfide matrix powder is added to the composite coating solution according to a preset solid-liquid ratio, stirred and dispersed evenly, and then subjected to heat preservation treatment. The coating slurry is obtained through in-situ composite coating reaction.

[0023] In one possible implementation, the heat preservation time is 3h to 5h, and / or the heat preservation temperature is 50℃ to 70℃.

[0024] Thirdly, embodiments of this application provide an all-solid-state battery, including a sulfide solid electrolyte as described in the first aspect and / or various possible embodiments of the first aspect, or a sulfide solid electrolyte prepared according to the second aspect and / or various possible implementations of the second aspect.

[0025] Fourthly, embodiments of this application provide an electrical device, including a device body and an all-solid-state battery as described in the third aspect.

[0026] This application provides a sulfide solid electrolyte, its preparation method, and its application. The sulfide solid electrolyte comprises a sulfide matrix powder and a composite coating layer. The sulfide matrix powder is doped with a rare earth compound, Nd₂S₃, and the mass of the rare earth compound is 0.5% to 2% of the mass of the sulfide matrix powder. Simultaneously, a composite coating layer composed of LiF and Al₂O₃ is coated on the surface of the matrix powder. The thickness of the composite coating layer is 15 nm to 35 nm, and the particle size distribution of the sulfide matrix powder is designed to be D₂S₃. 10 =1.0μm~1.4μm, D 50 =1.5μm~1.9μm and D 90 This sulfide solid electrolyte exhibits a narrow distribution system with a micrometer diameter (μm) ranging from 2.0 μm to 2.4 μm. It possesses excellent mechanical toughness, high ionic conductivity, and good interfacial compatibility. Attached Figure Description

[0027] 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.

[0028] Figure 1 This is a structural schematic diagram of a sulfide solid electrolyte provided in this application;

[0029] Figure 2 This is a schematic flowchart illustrating a method for preparing a sulfide solid electrolyte provided in this application.

[0030] The accompanying drawings have illustrated 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 specific embodiments. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] The application background of this application is explained as follows:

[0033] Solid-state lithium batteries, with their core advantages such as high energy density, excellent safety, and no risk of electrolyte leakage, have become the core development direction of next-generation energy storage technology and a key breakthrough for the new energy industry to achieve long-range and high-safety energy storage upgrades. The replacement of flammable and leaky organic liquid electrolytes in traditional batteries with solid-state electrolytes fundamentally eliminates a series of safety hazards such as thermal decomposition, leakage short circuits, thermal runaway, fire, and explosion. Among them, sulfide solid-state electrolytes, due to their high room-temperature ionic conductivity and fast ion migration rate, are better suited to meet the application requirements of high-capacity, high-power batteries compared to oxide solid-state electrolytes and polymer solid-state electrolytes, and are currently the focus of industrialization research and development.

[0034] In existing technologies, sulfide solid electrolytes (such as Li6PS5Cl, Li7P3S) 11 It is usually prepared by high-temperature solid-state method or mechanical ball milling method.

[0035] The high-temperature solid-state method, also known as solid-state sintering, is based on the core idea of ​​driving chemical reactions between solid raw materials through high-temperature heat treatment. Taking the preparation of a typical silver-germanium sulfide-type electrolyte, Li6PS5Cl, as an example, lithium sulfide (Li2S), phosphorus pentasulfide (P2S5), and lithium chloride (LiCl) precursors are first mixed in a specific stoichiometric ratio, and then ball-milled to achieve crushing and uniform mixing of the raw material powders. Subsequently, the mixed precursors are placed in a sintering furnace under an inert gas environment for high-temperature heat treatment (e.g., sintering at 550℃ for 8 hours) to prepare Li6PS5Cl with high ionic conductivity.

[0036] Unlike solid-state sintering, which relies on high-temperature thermal drive, mechanical ball milling is a process that induces chemical reactions at room temperature through pure mechanical energy. This method typically uses a high-energy ball mill, where proportionally mixed raw material powders (such as Li₂S and P₂S₅) are placed in a sealed mill jar along with grinding balls. Under the high-speed operation of the high-energy ball mill, the raw material powders are subjected to intense impact, grinding, and shearing by the grinding balls. This high-intensity mechanical force not only continuously breaks and refines the raw material powder particles, but more importantly, the instantaneous local high pressure and shear force provided are sufficient to break the original chemical bonds of the reactants, promoting mixing and reaction of different raw materials at the atomic level, thereby directly synthesizing the desired sulfide solid electrolyte. Compared to high-temperature solid-state methods, mechanical ball milling can achieve material synthesis at relatively lower temperatures.

[0037] In practical applications, high-temperature solid-state method and mechanical ball milling method are often used in combination. That is, the raw material powder is first mixed at the atomic level by ball milling, and then sintering is carried out to promote crystallization and improve the ionic conductivity of sulfide solid electrolyte.

[0038] However, sulfide solid electrolytes prepared by high-temperature solid-state methods or mechanical ball milling have poor mechanical toughness and high brittleness. This makes them prone to particle breakage and interlayer delamination due to stress during the fabrication, stacking, or charge-discharge cycling of pouch cells, leading to a sharp increase in interfacial impedance and severely impacting battery cycle life. Specifically, when sulfide solid electrolytes are used to adapt high-capacity pouch all-solid-state batteries, their poor mechanical toughness and high brittleness make it difficult to form a dense and robust solid-solid contact between the electrolyte layer and the flexible electrode layer. This results in the inability to effectively stack the capacities of each layer after multilayer stacking, further exacerbating the mechanical stress problem of the sulfide solid electrolyte and causing a significant decrease in battery cycle stability.

[0039] In addition, existing sulfide solid electrolytes still have the following technical challenges in practical applications:

[0040] (1) The ionic conductivity of existing sulfide solid electrolytes is difficult to meet the requirements of high-capacity and high-power batteries. Especially in high-capacity stacking scenarios, insufficient ion transport rate limits the capacity of positive and negative electrode active materials.

[0041] (2) Some sulfide solid electrolytes can also be prepared by element (such as germanium Ge, tin Sn) doping technology. However, the doping elements are not only prone to side reactions with the sulfide matrix, reducing the stability of the electrolyte, but the doping ratio is also difficult to control precisely, resulting in large fluctuations in electrolyte performance. The preparation process is complicated and it is difficult to achieve large-scale production.

[0042] (3) Existing sulfide solid electrolytes have poor interfacial compatibility with high nickel cathodes (such as NCM900 and NCM950) and high silicon anodes, which easily lead to interfacial side reactions, generating insulating impurity films that hinder lithium-ion conduction and further limit the industrial application of high-capacity soft-pack all-solid-state batteries.

[0043] Therefore, improving the mechanical toughness of sulfide solid electrolytes, and thus overcoming the technical bottlenecks of poor capacity superposition and high interfacial impedance between multilayer stacks, is an urgent technical problem to be solved.

[0044] Based on the aforementioned technical problems, the inventors, during the research on the preparation of sulfide solid electrolytes, discovered that the poor mechanical toughness of sulfide solid electrolytes can be effectively solved through the synergistic modification of rare earth element doping and composite coating. Specifically, by introducing rare earth compounds (such as Nd₂S₃) into the sulfide matrix to optimize the crystal structure and suppress particle agglomeration, and simultaneously constructing a LiF-Al₂O₃ composite coating layer on the surface of the sulfide matrix, the dual effects of reducing interfacial impedance and suppressing side reactions are achieved. This technical concept, through the synergistic effect of rare earth element modification and composite coating, not only improves the mechanical toughness of sulfide solid electrolytes, solving the brittleness problem of existing sulfide solid electrolytes, but also improves ionic conductivity, optimizes interfacial compatibility, and achieves stable stacking and long-term cycling of high-capacity soft-pack all-solid-state batteries. Furthermore, the preparation process is suitable for large-scale mass production. Based on this, this application provides a sulfide solid electrolyte, its preparation method, and its applications.

[0045] The technical solution of this application and how it solves the above-mentioned technical problems will be 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 be described below with reference to the accompanying drawings.

[0046] Figure 1 Here is a schematic diagram of the structure of a sulfide solid electrolyte provided in this application, as shown below. Figure 1 As shown, the sulfide solid electrolyte includes: sulfide matrix powder and composite coating layer, wherein the sulfide matrix powder is doped with rare earth compounds, and the composite coating layer composed of LiF and Al2O3 coats the surface of the sulfide matrix powder.

[0047] Rare earth compounds refer to compounds formed by the chemical bonding of rare earth elements such as scandium, yttrium, and the lanthanides (a total of 17 metallic elements) with other elements. They exhibit a wide variety of forms, including common oxides (such as scandium oxide and lanthanum oxide), fluorides, sulfides, halides, and various organic complexes. The composite coating layer on the surface of the sulfide matrix powder is composed of LiF and Al2O3. Compared to other fluorides (such as zirconium fluoride, magnesium fluoride, and sodium fluoride), LiF is itself a good lithium-ion conductor, and its abundant fluoride ion environment provides a low-resistance, fast migration channel for lithium ions. Compared to other oxides (such as zirconium oxide and boron oxide), Al2O3, with its numerous unsaturated coordinated aluminum atoms and oxygen vacancies on its surface, exhibits a strong affinity for lithium ions, effectively anchoring and enriching the lithium-ion concentration at the interface. When LiF and Al2O3 are tightly composited, the strong polarization effect of Al2O3 further reduces the activation energy of lithium ions in the LiF lattice. Together, they construct a three-dimensional interconnected fast ion pathway that runs through the entire coating layer. This not only improves the ionic conductivity of the sulfide solid electrolyte but also optimizes the interfacial compatibility between the sulfide solid electrolyte and the positive and negative electrodes. Furthermore, this composite coating layer, covering the surface of the sulfide matrix powder, can also isolate it from the erosion of water vapor and oxygen in the external air, preventing the hydrolysis of the sulfide matrix powder and the generation of toxic gases.

[0048] The sulfide matrix powder forms the main framework of this sulfide solid electrolyte and can be selected from Li6PS5Cl and Li7P3S. 11 Li6PS5Cl is a typical fast ion conductor of sulfides, containing at least one of the following: Li3PS4, etc. Taking Li6PS5Cl as an example, its brittleness stems from the rigid fracture of bond angles in the PS framework and naturally occurring structural defects at grain boundaries. The introduction of rare earth compounds causes local lattice distortion due to the significant radius and charge difference between rare earth ions and lithium or phosphorus ions. This distortion constructs a strain field at the microscale. When the sulfide solid electrolyte is subjected to stress and cracks develop, this strain field forces the crack tip to deflect, bifurcate, or pin, thereby consuming a large amount of fracture energy. This transforms the sulfide solid electrolyte from a brittle cleavage fracture mode to a quasi-ductile fracture mode with a certain plastic energy dissipation capacity, directly improving its mechanical toughness. Simultaneously, the LiF-Al2O3 composite coating layer covering the sulfide matrix powder externally solves the problem of interparticle contact brittleness. It fills the gaps between sulfide matrix powder particles, disperses concentrated contact stress, dissipates fracture energy through its own deformation, and inhibits the propagation of interparticle cracks.

[0049] The synergistic effect of rare earth compound doping modification and LiF-Al2O3 composite coating not only improves the mechanical toughness of sulfide solid electrolyte, avoiding particle breakage and interlayer delamination during charging, discharging and stacking of all-solid-state batteries, but also effectively inhibits particle agglomeration by uniformly dispersing rare earth compounds in the sulfide matrix, improving the ionic conductivity of sulfide solid electrolyte and interfacial compatibility with the positive and negative electrodes, reducing interfacial side reactions and lowering interfacial impedance.

[0050] In one possible implementation, the rare earth compound is Nd2S3;

[0051] And / or,

[0052] The mass of rare earth compounds is 0.5% to 2% of the mass of sulfide matrix powder.

[0053] Among them, neodymium sulfide with the molecular formula Nd₂S₃ is a typical rare earth sesquisulfide, with a high melting point and a polymorphic structure. 3+ Charge, ionic radius and Li in the sulfide matrix + P 5+ Significant differences exist. Doping with sulfide electrolytes such as Li6PS5Cl can induce local lattice distortion and form a micro-strain field. When cracks are generated under stress, this field can deflect and pin the crack tip to dissipate fracture energy, thus improving the intrinsic brittleness of sulfide solid electrolytes. Simultaneously, Nd... 3+ It can form stable chemical bonds with sulfur, moderately optimizing the lattice stability of sulfide solid electrolytes and a small number of lithium-ion transport channels. Its sulfide properties can also avoid the interfacial impedance caused by oxide impurities introduced by doping.

[0054] Furthermore, compared to rare earth oxides, rare earth halides, or other rare earth compounds, Nd₂S₃ doping does not introduce impurity elements such as oxygen and halogens that easily induce the formation of insulating impurity phases. This maintains a pure ion conduction environment in the Li₆PS₅Cl sulfide matrix, avoiding the problem of increased interfacial impedance. Simultaneously, Nd… 3+ Ionic radius and charge and matrix interior Li + P 5+ The formation of a suitable and sufficient difference can uniformly induce a micro-strain field of appropriate strength within the crystal lattice, stably achieving the toughening effect of crack pinning, deflection, and bifurcation. The intrinsic properties of the high-melting-point polymorph also ensure that it will not decompose or be lost during the electrolyte sintering stage, allowing it to remain in the crystal lattice for a long time and continue to exert its modifying effect. In contrast, Gd... 3+ 、Tb 3+ Dy 3+ Ho 3+ Equal-weight rare earth ions, with excessively small ionic radii, and the Li matrix + P 5+Insufficient size and charge differences between them can only produce weak lattice distortion, and cannot form a continuous micro-strain field that can effectively dissipate fracture energy, making it difficult to achieve the toughening effect of crack pinning, deflection and bifurcation.

[0055] In addition, Nd 3+ It exhibits excellent bonding strength with sulfur atoms, and doping only slightly adjusts the original lattice structure and broadens the lithium-ion migration pathway without disrupting the basic Li6PS5Cl framework, thus balancing improved mechanical toughness and optimized ionic conductivity. In contrast, doping with Ce... 3+ La 3+ Other light rare earth ions have relatively large ionic radii and low chemical bond energies when forming with sulfur. After doping, they easily pull on the original crystal lattice framework of Li6PS5Cl, causing large-scale lattice collapse and directly blocking the original lithium-ion transport channels, resulting in a decrease in ionic conductivity. The mass of the rare earth compound can be 0.5% to 2% of the mass of the sulfide matrix powder, that is, 0.5% to 2% of the total raw material mass of the sulfide matrix. For example, the mass of the rare earth compound can be 0.5%, 1%, 1.5%, or 2% of the total raw material mass of the sulfide matrix, or any other value within the range of 0.5% to 2%. In other words, when the total mass fraction of the sulfide matrix is ​​1, the corresponding mass fraction of the rare earth compound can be 0.005, 0.01, 0.015, or 0.02, etc.

[0056] In one possible implementation, the thickness of the composite coating layer is 15 nm to 35 nm.

[0057] The thickness of the composite coating layer refers to the radial dimension of the LiF-Al2O3 shell layer coating the surface of the sulfide matrix powder. Its value is typically precisely determined through direct observation using high-resolution transmission electron microscopy or depth etching analysis using X-ray photoelectron spectroscopy. For example, the thickness of the composite coating layer can be any value within the range of 15nm to 35nm, such as 15nm, 18nm, 20nm, 25nm, 27nm, 30nm, 33nm, and 35nm. The thickness of the composite coating layer can be controlled by adjusting the holding time in the post-coating process. At a set heat treatment temperature, the composite coating solution undergoes an in-situ composite coating reaction with the sulfide matrix powder. The holding time directly determines the degree to which the substances in the composite coating solution migrate, polymerize, and crystallize on the surface of the sulfide matrix powder. The longer the holding time, the more complete the reaction and diffusion of the coating material, resulting in a thicker composite coating layer.

[0058] If the composite coating is too thick, although the physical barrier of mechanical protection may seem thicker and stronger at first glance, the heterojunction path that lithium ions need to traverse from the external electrode into the sulfide matrix is ​​drastically lengthened. The grain boundary scattering and local barrier accumulation effects encountered during migration increase exponentially, leading to a significant increase in ion transport resistance across the composite coating. Consequently, the room temperature ionic conductivity of the overall sulfide solid electrolyte drops sharply, even lower than that of the uncoated sulfide matrix. Based on this, a thickness of 15nm~35nm ensures that the composite coating provides sufficient chemical isolation and stress buffering without sacrificing conductivity due to an excessively long ion traversal path, thus truly realizing the design goal of a synergistic leap in mechanical toughness and ionic conductivity of the sulfide solid electrolyte.

[0059] In one possible implementation, the particle size distribution of the sulfide-based powder includes:

[0060] D 10 =1.0μm~1.4μm, D 50 =1.5μm~1.9μm and D 90 =2.0μm~2.4μm.

[0061] Among them, D 50 Also known as median diameter or median particle size, it represents the particle size value in the sulfide matrix powder when the cumulative volume fraction reaches exactly 50%, starting from the smallest particle. In other words, half the volume of particles has a diameter smaller than this value, and the other half has a diameter larger than this value, directly reflecting the overall fineness of the sulfide matrix powder. D 10 This refers to the particle size corresponding to a cumulative volume fraction of 10%. It indicates the particle size level of the finer end of the sulfide matrix powder, that is, the distribution boundary of fine powder. The larger the value, the fewer ultrafine particles in the powder, and vice versa. D 90 This refers to the particle size corresponding to a cumulative volume fraction of 90%. It indicates the particle size level of the coarser end of the sulfide matrix powder. The smaller this value, the tighter the upper limit particle size control of the powder, and the lower the proportion of large particles. D 10 With D 90 The span between particles directly reflects the width or dispersion of the particle size distribution; the narrower the span, the more uniform the particle size. This synergistic combination of multi-level particle sizes allows fine particles to effectively fill the gaps between coarse particles, significantly improving the bulk density and particle contact uniformity after cold pressing of the sulfide solid electrolyte. This, in turn, enhances the mechanical toughness of the electrolyte sheets, enabling them to better resist stress concentration induced by volume expansion and contraction during charge-discharge cycles, effectively suppressing particle breakage and interlayer delamination.

[0062] For example, D 10The value can be any value within the range of 1.0μm to 1.4μm, such as 1.0μm, 1.2μm, 1.3μm, or 1.4μm; D 50 The value can be 1.5μm, 1.7μm, or 1.9μm, or any other value within the range of 1.5μm to 1.9μm; D 90 The value can be 2.0μm, 2.1μm, 2.2μm, 2.3μm, or 2.4μm, or any other value within the range of 2.0μm to 2.4μm. Understandably, excessively large particles (exceeding D...) 90 Upper limit) is prone to forming exposed defects during coating, which become stress concentration points and break first under pressure; excessively fine particles (below D) 10 If the particle size distribution is too low (below the limit), it is prone to agglomeration and disruption of packing uniformity, resulting in the coexistence of locally dense and loose areas. This abnormal particle size distribution leads to uneven packing of sulfide matrix powder particles, resulting in insufficient compaction density, poor interparticle contact and obstructed ion transport. At the same time, it prevents the uniform distribution of stress, reduces mechanical toughness, and causes repeated particle breakage and interlayer delamination during charge-discharge cycles, ultimately severely weakening the overall electrochemical performance of the electrolyte.

[0063] The sulfide solid electrolyte provided in this application includes: a sulfide matrix powder and a composite coating layer. The sulfide matrix powder is doped with the rare earth compound Nd₂S₃, and the mass of the rare earth compound is 0.5% to 2% of the mass of the sulfide matrix powder. Simultaneously, a nanoscale composite coating layer composed of LiF and Al₂O₃ is coated on the surface of the matrix powder. The thickness of this composite coating layer is 15 nm to 35 nm, and the particle size distribution of the sulfide matrix powder is designed as D. 10 =1.0μm~1.4μm, D 50 =1.5μm~1.9μm and D 90 A narrow distribution system with a particle size of 2.0 μm to 2.4 μm. Lattice distortion induced by rare earth compound Nd₂S₃ doping constructs a strain field at the microscale, causing crack tips to deflect, bifurcate, or pin under stress, significantly improving the mechanical toughness of the sulfide solid electrolyte. Simultaneously, the LiF-Al₂O₃ composite coating not only effectively improves ion transport efficiency but also acts as a chemical barrier to prevent water vapor and oxygen erosion, further strengthening interlayer bonding by filling particle gaps and dispersing contact stress. Therefore, the synergistic effect of rare earth compound doping modification and the LiF-Al₂O₃ composite coating enables the sulfide solid electrolyte to effectively suppress particle fragmentation and interlayer delamination during charging, discharging, and stacking, improving its mechanical toughness. It also increases the ionic conductivity of the sulfide solid electrolyte, optimizes its interfacial compatibility with the positive and negative electrodes, reduces interfacial side reactions and lowers interfacial impedance, achieving a simultaneous improvement in the mechanical toughness and electrochemical performance of the solid electrolyte.

[0064] Figure 2 A schematic flowchart of a method for preparing a sulfide solid electrolyte provided in this application is shown below. Figure 2 As shown, the method includes:

[0065] S201: After mixing and treating Li2S, P2S5, and LiCl, rare earth compounds and dispersants are added to obtain a precursor slurry; wherein the rare earth compound is Nd2S3 and the dispersant is anhydrous cyclohexane.

[0066] In this step, lithium sulfide (Li₂S) is an inorganic compound composed of lithium and sulfur, serving as both the lithium and sulfur source in the sulfide solid electrolyte; phosphorus pentasulfide (P₂S₅) is an inorganic compound composed of phosphorus and sulfur, and is the most commonly used network-forming material in sulfide solid electrolytes, reacting with Li₂S to form a framework that provides ion transport channels; lithium chloride (LiCl) is an inorganic compound composed of lithium and chlorine, and can be used as a modifier. Due to the larger radius of chloride ions, it can expand the lithium ion transport channels, promote lithium ion migration, and improve ionic conductivity.

[0067] Dispersants are functional additives used to address the problem of agglomeration of small particles. If the sulfide matrix powder particles are not uniformly dispersed, they will not only block ion transport channels but also lead to inconsistent density throughout the final solid sulfide electrolyte, severely affecting performance. Anhydrous cyclohexane is a common organic solvent with stable chemical properties. At room temperature, it is a colorless, transparent, flammable liquid with a characteristic odor and is almost insoluble in water. Sulfides such as Li₂S and P₂S₅ readily react with water and oxygen in the air. For example, Li₂S reacts with water to produce the harmful gas hydrogen sulfide (H₂S) and the unwanted byproduct lithium hydroxide (LiOH), while P₂S₅ reacts with water to produce the harmful gas H₂S and the unwanted byproduct phosphoric acid (H₃PO₄). Therefore, the entire mixing process must be carried out in a strictly anhydrous and oxygen-free environment. Anhydrous cyclohexane itself has extremely low water content and stable non-polar properties, which are the ideal inert environment to meet this stringent requirement. As a dispersant, it can uniformly disperse raw materials such as Li2S, P2S5, LiCl and Nd2S3 that meet the preset molar ratio to form a precursor slurry, providing the material basis for the preparation of sulfide solid electrolytes.

[0068] For example, Li2S, P2S5, and LiCl are mixed in a stoichiometric ratio of 5:1:1, and then 0.5% to 2% of the mass of rare earth compound Nd2S3 (based on the total mass of the sulfide matrix raw materials) and 4 to 6 times the mass of anhydrous cyclohexane (based on the total mass of the sulfide matrix raw materials) are added as a dispersant. After stirring evenly, a precursor slurry is obtained.

[0069] S202: The precursor slurry is ball-milled, vacuum dried, and then sintered at a constant temperature in an inert gas environment. After grinding and sieving, coarse sulfide powder is obtained.

[0070] Ball milling refers to placing the precursor slurry in a ball mill jar containing grinding media (such as cemented carbide balls, zirconia balls, etc.). The ball mill uses the high-speed rotation, rotation, or planetary motion of the ball mill jar to cause the grinding media to impact and grind the particles in the precursor slurry, breaking up the agglomeration of the particles and promoting the uniform dispersion of rare earth dopants in the sulfide matrix at the atomic level. At the same time, the mechanical force itself can also activate the particle surface and reduce the energy barrier of subsequent solid-phase reactions, providing a basis for full reaction in the subsequent sintering process.

[0071] The mixture obtained after ball milling is still a wet mixture containing organic solvents. It must be vacuum dried, which involves heating in a vacuum environment to remove anhydrous cyclohexane and residual volatile components. Then, it is sintered at a constant temperature under inert gas protection to complete the solid-phase reaction and form coarse sulfide powder. After sintering, it is ground and sieved to remove large particle agglomerates and obtain coarse sulfide powder.

[0072] For example, when ball milling the precursor slurry, the milling media can be zirconia balls with a diameter of 4 mm to 12 mm. The ratio between the total mass of the milling media and the total mass of the precursor slurry in the milling jar, i.e., the ball-to-material ratio, can be (12~16):1. The milling speed can be 350 rpm to 550 rpm, and the milling time can be 9 h to 13 h. After ball milling, the resulting mixed slurry is vacuum dried to obtain a dried mixture. The vacuum degree can be 1 Pa to 5 Pa, the drying temperature can be 70 °C to 90 °C, and the drying time can be 9 h to 11 h. Then, the dried mixture is placed in an inert gas environment with an argon flow rate of 60 mL / min to 90 mL / min and a heating rate of 6 °C / min to 9 °C / min, and sintered at a constant temperature of 580 °C for 7 h. After naturally cooling to room temperature, it is ground through a 1000-mesh sieve to obtain coarse sulfide powder.

[0073] S203: After the coarse sulfide powder is pulverized by airflow, it is sieved through a three-stage grading sieve to obtain sulfide matrix powder.

[0074] Among them, the mesh size of the three-stage grading sieve decreases sequentially along the sieving direction, and the particle size distribution of the sulfide matrix powder includes: D 10 =1.0μm~1.4μm, D 50 =1.5μm~1.9μm and D 90 =2.0μm~2.4μm.

[0075] In this step, air jet milling is a dry processing technology that utilizes the collision of high-speed airflow to pulverize materials. Its basic principle is to accelerate compressed air or inert gas (such as high-purity nitrogen or argon) to supersonic speeds through a specially designed nozzle, forming a high-speed jet of air. This airflow carries the coarse sulfide powder particles to be pulverized into a specially designed pulverizing chamber. There, the particles collide, rub, and shear violently against each other in the high-speed turbulent flow, achieving ultrafine pulverization through the material's own cohesive force and kinetic energy difference. The entire pulverization process is completed in a sealed pulverizing chamber, effectively isolating external moisture and oxygen, thus ensuring the chemical purity of the sulfide matrix powder while achieving ultrafine pulverization.

[0076] The three-stage grading sieve follows the airflow pulverizer and is used to achieve continuous gradient grading through screens of different aperture sizes connected in series. The aperture size of the screens decreases sequentially along the sieving direction, and the aperture sizes of the three screens can be 2.4μm, 1.9μm, and 1.0μm. Its working logic is as follows: the powder after air jet milling first passes through a first-stage sieve with a pore size of 2.4 μm. This sieve acts as a barrier to intercept coarse particles. All overly coarse particles larger than 2.4 μm are intercepted, recycled, and returned to the air jet mill for reprocessing. The particles that pass through this sieve continue to enter the second-stage sieve with a pore size of 1.9 μm for secondary screening. At this time, particles between 1.9 μm and 2.4 μm are intercepted by this stage and collected as sulfide matrix powder components. Fine powder smaller than 1.9 μm continues to fall to the third-stage sieve with a pore size of 1.0 μm. Finally, ultrafine powder smaller than 1.0 μm is intercepted and separated separately, while particles between 1.0 μm and 1.9 μm are also collected as sulfide matrix powder components. The powder is processed by sequentially cascading through three layers of sieves in descending order of pore size. The resulting powders, ranging from 1.0μm to 1.9μm and from 1.9μm to 2.4μm, are then mixed to obtain a product with D... 10 =1.0μm~1.4μm, D 50 =1.5μm~1.9μm and D 90 Sulfide-based powder with a particle size distribution of 2.0μm to 2.4μm.

[0077] For example, coarse sulfide powder is fed into an air jet mill for air jet milling treatment. The milling pressure can be 0.7MPa~0.9MPa, the feed rate can be 12g / min~18g / min, and the milling time can be 12min~18min. Then, the air jet milled powder is sieved through a three-stage grading sieve with a screen aperture of 2.4μm, 1.9μm, and 1.0μm to obtain sulfide matrix powder with uniform particle size and no agglomeration.

[0078] S204: After mixing LiF and Al2O3, anhydrous cyclohexane is added to obtain a composite coating solution. Sulfide matrix powder is added to the composite coating solution according to a preset solid-liquid ratio. After stirring and dispersing evenly, the mixture is kept warm and then coated with a coating slurry through an in-situ composite coating reaction.

[0079] In this step, the solid-liquid ratio refers to the ratio between the mass of the sulfide matrix powder participating in the in-situ composite coating reaction and the mass of the composite coating solution. This solid-liquid ratio determines the fluidity and dispersion uniformity of the coating slurry. If the solid content is too high, the coating slurry will be too viscous, making it difficult for the matrix powder to be completely wetted by the coating solution and prone to agglomeration. If the solid content is too low, it means that the liquid phase accounts for too large a proportion. Although this is beneficial for dispersion, it will significantly reduce the processing efficiency of a single batch and increase the energy consumption of subsequent desolvation.

[0080] After the coating slurry is stirred evenly, it enters the heat preservation stage. This process refers to the continuous heat treatment of the coating slurry under constant temperature control. The purpose is to provide sufficient thermodynamic driving force and kinetic activation energy for the chemical bonding between the coating precursor (i.e., LiF and Al2O3) and the surface of the sulfide matrix powder. The heat preservation temperature is usually set below the boiling point of the solvent to avoid the slurry splashing due to the violent boiling of anhydrous cyclohexane. The length of the heat preservation time directly controls the progress of the coating reaction, which is the core parameter for controlling the thickness of the composite coating layer mentioned above.

[0081] In one possible implementation, the heat preservation time is 3h to 5h, and / or the heat preservation temperature is 50℃ to 70℃. For example, the heat preservation time can be any value within the range of 3h to 5h, such as 3h, 3.5h, 4h, 4.5h, or 5h; the heat preservation temperature can be any value within the range of 50℃ to 70℃, such as 50℃, 55℃, 60℃, 65℃, 68℃, or 70℃.

[0082] In-situ composite coating reaction refers to the direct reaction of LiF and Al2O3 in a slurry environment containing sulfide matrix powder during the heat preservation process to generate a composite coating layer, which is then deposited in situ on the surface of the sulfide matrix powder. Compared with the method of pre-preparing the coating layer and then mechanically mixing it, this in-situ growth mechanism enables the coating layer and the sulfide matrix powder to form a tight chemical bond interface rather than a simple physical adhesion, thereby avoiding the peeling and separation of the coating layer during subsequent molding and cycling.

[0083] For example, a composite coating solution is first prepared. Specifically, LiF and Al2O3 are mixed in a mass ratio of (3~5):1, and anhydrous cyclohexane is added. The mixture is stirred at a stirring rate of 250 rpm to 350 rpm for 40 min to 70 min until homogeneous, until LiF and Al2O3 are completely dissolved, to obtain a composite coating solution with a concentration of 8 g / L to 12 g / L. Then, sulfide matrix powder is added to the composite coating solution at a solid-liquid ratio of 1:(8~12) g / mL. The mixture is stirred to ensure that the sulfide matrix powder is uniformly dispersed in the coating solution. The solution is then kept at 50℃ to 70℃ for 3 h to 5 h to obtain a coating slurry through an in-situ composite coating reaction.

[0084] S205: The coating slurry is heated and then vacuum dried to obtain a sulfide solid electrolyte.

[0085] This step is the final post-processing step in the preparation of sulfide solid electrolytes. Its core lies in the synergistic effect of heating and vacuum environment to completely remove the organic solvent from the coating slurry and complete the final curing of the coating layer. Heating involves gradually heating the coating slurry to a specific temperature range before vacuum drying. Vacuum drying introduces a negative pressure environment on top of the heating, utilizing the principle that the boiling point of liquids decreases significantly under reduced pressure. This causes the residual anhydrous cyclohexane to boil violently and rapidly vaporize at a temperature far below its atmospheric pressure boiling point, detaching it from the powder. After this post-processing step, the resulting product is the final sulfide solid electrolyte, uniformly covered with a 15nm~35nm thick LiF-Al2O3 composite coating layer. The particles are modified by doping with the rare earth compound Nd2S3. The sulfide solid electrolyte maintains its original narrow particle size distribution while exhibiting excellent flowability and dispersibility, making it directly usable in subsequent all-solid-state battery electrode pressing or electrolyte separator forming processes.

[0086] For example, the coating slurry is placed in a vacuum drying oven and heated to 90°C to 110°C at a rate of 3°C / min to 6°C / min. Then, it is dried in a vacuum environment with a vacuum degree of 3Pa to 5Pa for 13 to 17 hours to completely remove organic solvents. After naturally cooling to room temperature, it is ground through a 2200-mesh sieve to obtain a sulfide solid electrolyte.

[0087] The method for preparing sulfide solid electrolytes provided in this application involves first mixing Li₂S, P₂S₅, and LiCl in a stoichiometric ratio, then adding a rare earth compound (Nd₂S₃) and anhydrous cyclohexane as a dispersant to obtain a precursor slurry. This slurry is then ball-milled to achieve atomic-level uniform dispersion of the rare earth elements. The solid-phase reaction is then completed by vacuum drying and isothermal sintering under an inert atmosphere. The resulting powder is ground and sieved to obtain coarse sulfide powder. Subsequently, the coarse powder is subjected to air jet milling and sequentially sieved through a three-stage classifier with pore sizes of 2.4 μm, 1.9 μm, and 1.0 μm to obtain a sulfide solid electrolyte with D... 10 =1.0μm~1.4μm, D 50 =1.5μm~1.9μm and D 90 A sulfide matrix powder with a narrow particle size distribution of 2.0μm~2.4μm was prepared. LiF and Al2O3 were then mixed with anhydrous cyclohexane to form a composite coating solution. The sulfide matrix powder was added according to a preset solid-liquid ratio. After heat preservation treatment, LiF and Al2O3 reacted in situ in the slurry environment to generate a composite coating layer, which was directly deposited on the surface of the powder. Finally, the solvent was removed by heating and vacuum drying, and the coating layer was solidified to obtain a sulfide solid electrolyte.

[0088] The sulfide solid electrolyte prepared by the above method has excellent mechanical toughness, high ionic conductivity and excellent interfacial compatibility. Moreover, the preparation method is simple and highly controllable, does not require high-temperature sintering modification, can be adapted to existing lithium battery production lines, is easy to scale up for industrial use, and the preparation process is safe and environmentally friendly, avoiding the reaction of sulfide solid electrolyte with air and moisture to generate toxic substances.

[0089] This application also provides an all-solid-state battery, including: the sulfide solid electrolyte mentioned in the above embodiments, or the sulfide solid electrolyte prepared by the method mentioned in the above method embodiments. The sulfide solid electrolyte can effectively solve the technical problems of poor capacity superposition effect and weak cycle stability of high-capacity soft-pack all-solid-state batteries.

[0090] This application also provides an electrical device, including: a device body and the all-solid-state battery mentioned in the previous embodiment. The all-solid-state battery can be used in vehicles, aircraft, drones, and also in electrical devices such as computers, mobile phones, digital cameras, and wearable devices, providing a stable and long-lasting power source and power support for these devices.

[0091] The following specific embodiments will provide a detailed description of the sulfide solid electrolyte, its preparation method, and its application provided in this application. Unless otherwise specified, the reagents, materials, and instruments used in the following embodiments are all conventional reagents, materials, and instruments in the art, and can all be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art. All steps involved are carried out in an anhydrous, inert gas-protected glove box (oxygen content <1ppm, water content <1ppm).

[0092] Example 1

[0093] This embodiment provides a sulfide solid electrolyte and an all-solid-state battery, the preparation method of which specifically includes the following steps:

[0094] (1) Li2S, P2S5 and LiCl with a purity of 99.5% are mixed in a stoichiometric ratio of 5:1:1. Then, 0.5% of the mass of the required sulfide matrix powder, Nd2S3 rare earth compound and 4 times the mass of the required sulfide matrix powder anhydrous cyclohexane are added as dispersants. After stirring evenly, a precursor slurry is obtained.

[0095] (2) The precursor slurry was ball-milled by a planetary ball mill to obtain a uniformly mixed slurry. The ball-to-material ratio was 12:1, the ball milling medium was zirconia balls with a diameter of 4 mm, the ball milling speed was 350 rpm, and the ball milling time was 9 h. The slurry was then placed in a vacuum drying oven and dried in a vacuum environment of 70 °C and 3 Pa for 9 h to completely remove the dispersant and obtain the dried mixture. The dried mixture was then placed in a quartz boat and placed in a tube furnace. It was sintered at 580 °C for 7 h in an inert gas environment with an argon flow rate of 60 mL / min and a heating rate of 6 °C / min. After naturally cooling to room temperature, it was ground through a 1000-mesh sieve to obtain Li6PS5Cl sulfide coarse powder.

[0096] (3) The coarse powder of Li6PS5Cl sulfide was placed in an air jet mill and subjected to air jet milling at a pressure of 0.7 MPa, a feed rate of 12 g / min, and a milling time of 12 min. After the treatment, it was sieved through a three-stage sieve with mesh sizes of 2.4 μm, 1.9 μm, and 1.0 μm to obtain uniform particle size and non-agglomerated Li6PS5Cl sulfide matrix powder. The particle size distribution of the Li6PS5Cl sulfide matrix powder was adjusted to D. 10 =1.0μm, D 50 =1.5μm and D 90 =2.0μm.

[0097] (4) Mix LiF and Al2O3 with a purity of 99.5% and a mass ratio of 3:1, add anhydrous cyclohexane, and stir at 250 rpm for 40 min until uniform until LiF and Al2O3 are completely dissolved to obtain a composite coating solution with a concentration of 8 g / L; add the Li6PS5Cl sulfide matrix powder obtained in step (3) to the composite coating solution at a solid-liquid ratio of 1:6 (g / mL), and continue stirring at 250 rpm for 40 min until the Li6PS5Cl sulfide matrix powder is uniformly dispersed in the coating solution, and then keep it at 50℃ for 3 h to obtain the coating slurry through in-situ composite coating reaction.

[0098] (5) The coated slurry was placed in a vacuum drying oven and heated to 90°C at a rate of 3°C / min. It was then dried in a vacuum environment with a vacuum degree of 3Pa for 13 hours to completely remove the organic solvent. After naturally cooling to room temperature, it was ground through a 2200-mesh sieve to obtain the sulfide solid electrolyte, which was then sealed and stored for later use.

[0099] The sulfide solid electrolyte comprises: a sulfide matrix powder doped with rare earth compound Nd2S3 (0.5% of the required sulfide matrix powder mass), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the sulfide matrix powder, the thickness of which is 15 nm.

[0100] (6) Preparation of positive electrode sheet

[0101] Lithium nickel cobalt manganese oxide (NCM900), the sulfide solid electrolyte obtained in step (5), superconducting carbon black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 82:13:3:2. N-methylpyrrolidone (NMP) was added as a dispersant, and the mixture was stirred at a stirring rate of 400 rpm for 2 hours to obtain a uniform positive electrode slurry. The positive electrode slurry was then coated onto a 13 μm thick aluminum foil current collector with a coating thickness of 120 μm and dried in a vacuum drying oven at 90 °C for 5 hours to remove NMP. Subsequently, the mixture was cold-pressed at a pressure of 1.2 MPa to obtain a positive electrode sheet with a thickness of 100 μm.

[0102] (7) Preparation of negative electrode sheet

[0103] Graphite and silicon-carbon materials with purities of 99.8% and 99.7% respectively (silicon content 40%), sulfide solid electrolyte obtained in step (5), superconducting carbon black, and PVDF were mixed in a mass ratio of 70:8:17:3:2. NMP was added as a dispersant, and the mixture was stirred at a stirring rate of 350 rpm for 2.5 h to obtain a uniform negative electrode slurry. The negative electrode slurry was then coated onto a 9 μm thick copper foil current collector with a coating thickness of 110 μm and dried in a vacuum drying oven at 90 °C for 5 h to remove NMP. Subsequently, the mixture was cold-pressed at a pressure of 1.2 MPa to obtain a negative electrode sheet with a thickness of 90 μm.

[0104] (8) Battery assembly

[0105] In an argon glove box (oxygen content < 1 ppm, water content < 10 ppm), the positive electrode, 6 μm thick ceramic separator, sulfide solid electrolyte (28 μm thick) obtained in step (5), and negative electrode are stacked in sequence and placed into a soft-pack packaging shell. The shell is compacted under 600 MPa isostatic pressure for 6 min to complete the cell preparation. Then, the shell is kept at 1.2 MPa operating pressure for 12 min to complete the assembly of a single-layer high-capacity soft-pack all-solid-state battery. After assembly, the shell is kept at 65°C for 2 h for activation treatment to obtain an all-solid-state battery containing the sulfide solid electrolyte in Example 1.

[0106] Example 2

[0107] This embodiment provides a sulfide solid electrolyte and an all-solid-state battery, the preparation method of which specifically includes the following steps:

[0108] (1) Li2S, P2S5 and LiCl with a purity of 99.5% were mixed in a stoichiometric ratio of 5:1:1. Then, 0.8% of the mass of the required sulfide matrix powder, Nd2S3 rare earth compound and 4.5 times the mass of the required sulfide matrix powder anhydrous cyclohexane were added as dispersants. After stirring evenly, the precursor slurry was obtained.

[0109] (2) The precursor slurry was ball-milled by a planetary ball mill to obtain a uniformly mixed slurry. The ball-to-material ratio was 13:1, the ball milling medium was zirconia balls with a diameter of 6 mm, the ball milling speed was 380 rpm, and the ball milling time was 9 h. The slurry was then placed in a vacuum drying oven and dried in a vacuum environment of 75 °C and 1 Pa for 10 h to completely remove the dispersant and obtain the dried mixture. The dried mixture was then placed in a quartz boat and placed in a tube furnace. It was sintered at 580 °C for 7 h in an inert gas environment with an argon flow rate of 70 mL / min and a heating rate of 7 °C / min. After naturally cooling to room temperature, it was ground through a 1000-mesh sieve to obtain Li6PS5Cl sulfide coarse powder.

[0110] (3) The coarse powder of Li6PS5Cl sulfide was placed in an air jet mill and subjected to air jet milling at a pressure of 0.75 MPa, a feed rate of 14 g / min, and a milling time of 14 min. After the treatment, it was sieved through a three-stage sieve with mesh sizes of 2.4 μm, 1.9 μm, and 1.0 μm to obtain uniform particle size and non-agglomerated Li6PS5Cl sulfide matrix powder. The particle size distribution of the Li6PS5Cl sulfide matrix powder was adjusted to D. 10 =1.1μm, D 50 =1.6μm and D 90 =2.1μm.

[0111] (4) Mix LiF and Al2O3 with a purity of 99.5% and a mass ratio of 3.5:1, add anhydrous cyclohexane, and stir at a stirring rate of 280 rpm for 50 min until uniform, until LiF and Al2O3 are completely dissolved to obtain a composite coating solution with a concentration of 9 g / L; add the Li6PS5Cl sulfide matrix powder obtained in step (3) to the composite coating solution at a solid-liquid ratio of 1:7 (g / mL), and continue stirring at a stirring rate of 280 rpm for 50 min until the Li6PS5Cl sulfide matrix powder is uniformly dispersed in the coating solution, and then keep it at 55℃ for 3.5 h to obtain the coating slurry through in-situ composite coating reaction.

[0112] (5) The coated slurry was placed in a vacuum drying oven and heated to 95°C at a rate of 4°C / min. It was then dried in a vacuum environment with a vacuum degree of 1Pa for 14 hours to completely remove the organic solvent. After naturally cooling to room temperature, it was ground through a 2200-mesh sieve to obtain the sulfide solid electrolyte, which was then sealed and stored for later use.

[0113] The sulfide solid electrolyte comprises: a sulfide matrix powder doped with rare earth compound Nd2S3 (0.8% of the required sulfide matrix powder mass), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the sulfide matrix powder, the thickness of which is 20 nm.

[0114] (6) Preparation of positive electrode sheet

[0115] NCM900 with a purity of 99.5%, the sulfide solid electrolyte obtained in step (5), superconducting carbon black, and PVDF were mixed in a mass ratio of 82:13:3:2. NMP was added as a dispersant, and the mixture was stirred at a stirring rate of 350 rpm for 2.5 h to obtain a uniform positive electrode slurry. The positive electrode slurry was then coated onto a 14 μm thick aluminum foil current collector with a coating thickness of 125 μm. The coating was then dried in a vacuum drying oven at 85 °C for 5.5 h to remove NMP. Subsequently, the coating was cold-pressed at a pressure of 1.2 MPa to obtain a positive electrode sheet with a thickness of 105 μm.

[0116] (7) Preparation of negative electrode sheet

[0117] Graphite and silicon-carbon materials with a purity of 99.5% (silicon content 40%), sulfide solid electrolyte obtained in step (5), superconducting carbon black, and PVDF were mixed in a mass ratio of 70:8:17:3:2. NMP was added as a dispersant, and the mixture was stirred at a stirring rate of 320 rpm for 3 hours to obtain a uniform negative electrode slurry. The negative electrode slurry was then coated onto a 10 μm thick copper foil current collector with a coating thickness of 115 μm. The coating was then dried in a vacuum drying oven at 85°C for 5.5 hours to remove NMP. Subsequently, the mixture was cold-pressed at a pressure of 1.2 MPa to obtain a negative electrode sheet with a thickness of 95 μm.

[0118] (8) Battery assembly: Same as step (8) in Example 1, and finally obtain an all-solid-state battery containing the sulfide solid electrolyte in Example 2.

[0119] Example 3

[0120] This embodiment provides a sulfide solid electrolyte and an all-solid-state battery, the preparation method of which specifically includes the following steps:

[0121] (1) Li2S, P2S5 and LiCl with purities of 99.9%, 99.8% and 99.8% respectively were mixed in a stoichiometric ratio of 5:1:1. Then, 1.0% of the mass of the required sulfide matrix powder, Nd2S3 rare earth compound and 5 times the mass of the required sulfide matrix powder anhydrous cyclohexane were added as a dispersant. After stirring evenly, a precursor slurry was obtained.

[0122] (2) The precursor slurry was ball-milled by a planetary ball mill to obtain a uniformly mixed slurry. The ball-to-material ratio was 14:1, the ball milling medium was zirconia balls with a diameter of 8 mm, the ball milling speed was 400 rpm, and the ball milling time was 11 h. The slurry was then placed in a vacuum drying oven and dried in a vacuum environment of 80 °C and 3 Pa for 10 h to completely remove the dispersant and obtain the dried mixture. The dried mixture was then placed in a quartz boat and placed in a tube furnace. It was sintered at 580 °C for 7 h in an inert gas environment with an argon flow rate of 80 mL / min and a heating rate of 8 °C / min. After naturally cooling to room temperature, it was ground through a 1000-mesh sieve to obtain Li6PS5Cl sulfide coarse powder.

[0123] (3) The coarse powder of Li6PS5Cl sulfide was placed in an air jet mill and subjected to air jet milling at a pressure of 0.8 MPa, a feed rate of 15 g / min, and a milling time of 15 min. After the treatment, it was sieved through a three-stage sieve with mesh sizes of 2.4 μm, 1.9 μm, and 1.0 μm to obtain uniform particle size and non-agglomerated Li6PS5Cl sulfide matrix powder. The particle size distribution of the Li6PS5Cl sulfide matrix powder was adjusted to D. 10 =1.2μm, D 50 =1.7μm and D 90 =2.2μm.

[0124] (4) Mix LiF and Al2O3 with a purity of 99.8% and a mass ratio of 4:1, add anhydrous cyclohexane, and stir at a stirring speed of 300 rpm for 60 min until uniform, until LiF and Al2O3 are completely dissolved to obtain a composite coating solution with a concentration of 10 g / L; add the Li6PS5Cl sulfide matrix powder obtained in step (3) to the composite coating solution at a solid-liquid ratio of 1:7.5 (g / mL), and continue stirring at a stirring speed of 300 rpm for 60 min until the Li6PS5Cl sulfide matrix powder is uniformly dispersed in the coating solution, and then keep it at 60℃ for 4 h to obtain the coating slurry through in-situ composite coating reaction.

[0125] (5) The coated slurry was placed in a vacuum drying oven and heated to 100°C at a rate of 5°C / min. It was then dried in a vacuum environment with a vacuum degree of 3Pa for 15 hours to completely remove the organic solvent. After naturally cooling to room temperature, it was ground through a 2200-mesh sieve to obtain the sulfide solid electrolyte, which was then sealed and stored for later use.

[0126] The sulfide solid electrolyte comprises: a sulfide matrix powder doped with rare earth compound Nd2S3 (at a mass of 1.0% of the required sulfide matrix powder), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the sulfide matrix powder, the thickness of which is 25 nm.

[0127] (6)~(8) are the same as steps (6)~(8) in Example 1, and finally an all-solid-state battery containing the sulfide solid electrolyte in Example 3 is obtained.

[0128] Example 4

[0129] This embodiment provides a sulfide solid electrolyte and an all-solid-state battery, the preparation method of which specifically includes the following steps:

[0130] (1) Li2S, P2S5 and LiCl with a purity of 99.9% are mixed in a stoichiometric ratio of 5:1:1. Then, 1.5% of the mass of the required sulfide matrix powder, Nd2S3 rare earth compound and 5.5 times the mass of the required sulfide matrix powder are added as a dispersant. After stirring evenly, a precursor slurry is obtained.

[0131] (2) The precursor slurry was ball-milled by a planetary ball mill to obtain a uniformly mixed slurry. The ball-to-material ratio was 15:1, the ball milling medium was zirconia balls with a diameter of 10 mm, the ball milling speed was 450 rpm, and the ball milling time was 12 h. The slurry was then placed in a vacuum drying oven and dried in a vacuum environment of 85 °C and 4 Pa ​​for 10.5 h to completely remove the dispersant and obtain the dried mixture. The dried mixture was then placed in a quartz boat and placed in a tube furnace. It was sintered at 580 °C for 7 h in an inert gas environment with an argon flow rate of 85 mL / min and a heating rate of 8.5 °C / min. After naturally cooling to room temperature, it was ground through a 1000-mesh sieve to obtain Li6PS5Cl sulfide coarse powder.

[0132] (3) The coarse powder of Li6PS5Cl sulfide was placed in an air jet mill and subjected to air jet milling at a pressure of 0.85 MPa, a feed rate of 16 g / min, and a milling time of 16 min. After that, it was sieved through a three-stage sieve with mesh sizes of 2.4 μm, 1.9 μm, and 1.0 μm to adjust the particle size distribution of the coarse powder of Li6PS5Cl sulfide to D. 10 =1.3μm, D 50 =1.8μm and D 90 =2.3μm, yielding uniformly sized and agglomerated Li6PS5Cl sulfide matrix powder.

[0133] (4) Mix LiF and Al2O3 with a purity of 99.9% and a mass ratio of 4.5:1, add anhydrous cyclohexane, and stir at a stirring rate of 320 rpm for 65 min until uniform, until LiF and Al2O3 are completely dissolved to obtain a composite coating solution with a concentration of 11 g / L; add the Li6PS5Cl sulfide matrix powder obtained in step (3) to the composite coating solution at a solid-liquid ratio of 1:8 (g / mL), and continue stirring at a stirring rate of 320 rpm for 65 min until the Li6PS5Cl sulfide matrix powder is uniformly dispersed in the coating solution, and then keep it at 65℃ for 4.5 h to obtain the coating slurry through in-situ composite coating reaction.

[0134] (5) The coated slurry was placed in a vacuum drying oven and heated to 105°C at a rate of 5.5°C / min. It was then dried in a vacuum environment with a vacuum degree of 4Pa for 16 hours to completely remove the organic solvent. After naturally cooling to room temperature, it was ground through a 2200-mesh sieve to obtain the sulfide solid electrolyte, which was then sealed and stored for later use.

[0135] The sulfide solid electrolyte comprises: a sulfide matrix powder doped with rare earth compound Nd2S3 (at a mass of 1.5% of the required sulfide matrix powder), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the sulfide matrix powder, the thickness of which is 30 nm.

[0136] (6)~(8) are the same as steps (6)~(8) in Example 1, and finally an all-solid-state battery containing the sulfide solid electrolyte in Example 4 is obtained.

[0137] Example 5

[0138] This embodiment provides a sulfide solid electrolyte and an all-solid-state battery, the preparation method of which specifically includes the following steps:

[0139] (1) Li2S, P2S5 and LiCl with a purity of 99.8% were mixed in a stoichiometric ratio of 5:1:1. Then, 2.0% of the mass of the required sulfide matrix powder, Nd2S3 rare earth compound and 6 times the mass of the required sulfide matrix powder anhydrous cyclohexane were added as dispersants. After stirring evenly, the precursor slurry was obtained.

[0140] (2) The precursor slurry was ball-milled by a planetary ball mill to obtain a uniformly mixed slurry. The ball-to-material ratio was 16:1, the ball milling media were zirconia balls with a diameter of 12 mm, the ball milling speed was 550 rpm, and the ball milling time was 13 h. The slurry was then placed in a vacuum drying oven and dried in a vacuum environment of 90 °C and 5 Pa for 11 h to completely remove the dispersant and obtain the dried mixture. The dried mixture was then placed in a quartz boat and placed in a tube furnace. It was sintered at 580 °C for 7 h in an inert gas environment with an argon flow rate of 90 mL / min and a heating rate of 9 °C / min. After naturally cooling to room temperature, it was ground through a 1000-mesh sieve to obtain Li6PS5Cl sulfide coarse powder.

[0141] (3) The coarse powder of Li6PS5Cl sulfide was placed in an air jet mill and subjected to air jet milling at a pressure of 0.9 MPa, a feed rate of 18 g / min, and a grinding time of 18 min. After the treatment, it was sieved through a three-stage sieve with mesh sizes of 2.4 μm, 1.9 μm, and 1.0 μm to obtain uniform particle size and non-agglomerated Li6PS5Cl sulfide matrix powder. The particle size distribution of the Li6PS5Cl sulfide matrix powder was adjusted to D. 10 =1.4μm, D 50 =1.9μm and D 90 =2.4μm.

[0142] (4) Mix LiF and Al2O3 with a purity of 99.8% and a mass ratio of 5:1, add anhydrous cyclohexane, and stir at a stirring speed of 350 rpm for 70 min until uniform, until LiF and Al2O3 are completely dissolved to obtain a composite coating solution with a concentration of 12 g / L; add the Li6PS5Cl sulfide matrix powder obtained in step (3) to the composite coating solution at a solid-liquid ratio of 1:9 (g / mL), and continue stirring at a stirring speed of 350 rpm for 70 min until the Li6PS5Cl sulfide matrix powder is uniformly dispersed in the coating solution, and then keep it at 70℃ for 5 h to obtain the coating slurry through in-situ composite coating reaction.

[0143] (5) The coated slurry was placed in a vacuum drying oven and heated to 110°C at a rate of 6°C / min. It was then dried in a vacuum environment with a vacuum degree of 5Pa for 17 hours to completely remove the organic solvent. After naturally cooling to room temperature, it was ground through a 2200-mesh sieve to obtain the sulfide solid electrolyte, which was then sealed and stored for later use.

[0144] The sulfide solid electrolyte comprises: a sulfide matrix powder doped with rare earth compound Nd2S3 (at a mass of 2.0% of the required sulfide matrix powder), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the sulfide matrix powder, the thickness of which is 35 nm.

[0145] (6)~(8) are the same as steps (6)~(8) in Example 1, and finally an all-solid-state battery containing the sulfide solid electrolyte in Example 5 is obtained.

[0146] Example 6

[0147] This embodiment provides a sulfide solid electrolyte and an all-solid-state battery. The preparation method of the sulfide solid electrolyte is completely consistent with the preparation method mentioned in Example 3, and specifically includes the following steps:

[0148] (1)~(5) are the same as steps (1)~(5) in Example 3. The final sulfide solid electrolyte includes: sulfide matrix powder doped with rare earth compound Nd2S3 (mass of which is 1.0% of the required sulfide matrix powder mass), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the sulfide matrix powder, the thickness of which is 25nm.

[0149] (6) Same as step (6) in Example 1.

[0150] (7) Same as step (7) in Example 1.

[0151] (8) Battery assembly

[0152] In an argon glove box (oxygen content < 1 ppm, water content < 10 ppm), three sets of positive electrode sheets, a 6 μm thick ceramic separator, a sulfide solid electrolyte (28 μm thick) obtained in step (5), and a negative electrode sheet were stacked in sequence. A sulfide solid electrolyte (28 μm thick) layer obtained in step (5) was laid between each layer as an isolation and ion transport layer. The cells were placed in a soft-pack packaging shell and compacted under 600 MPa isostatic pressure for 7 min to complete the cell preparation. Then, the cells were kept at 1.2 MPa operating pressure for 12 min to complete the assembly of the three-layer stacked high-capacity soft-pack all-solid-state battery. After assembly, the cells were kept at 65°C for 2 h for activation treatment to obtain the all-solid-state battery.

[0153] Example 7

[0154] This embodiment provides a sulfide solid electrolyte and an all-solid-state battery. The preparation method of the sulfide solid electrolyte is completely consistent with the preparation method mentioned in Example 3, and specifically includes the following steps:

[0155] (1)~(5) are the same as steps (1)~(5) in Example 3. The final sulfide solid electrolyte includes: sulfide matrix powder doped with rare earth compound Nd2S3 (mass of which is 1.0% of the required sulfide matrix powder mass), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the sulfide matrix powder, the thickness of which is 25nm.

[0156] (6) Same as step (6) in Example 1.

[0157] (7) Same as step (7) in Example 1.

[0158] (8) Battery assembly

[0159] In an argon glove box (oxygen content < 1 ppm, water content < 10 ppm), five sets of positive electrode sheets, a 6 μm thick ceramic separator, a 28 μm thick sulfide solid electrolyte obtained in step (5), and a negative electrode sheet were stacked in sequence. A 28 μm thick sulfide solid electrolyte layer obtained in step (5) was laid between each layer as an isolation and ion transport layer. The cells were placed in a soft-pack packaging shell and compacted under 600 MPa isostatic pressure for 8 min to complete the cell preparation. Then, the cells were kept at 1.2 MPa operating pressure for 15 min to complete the assembly of the 5-layer stacked high-capacity soft-pack all-solid-state battery. After assembly, the cells were kept at 65°C for 2 h for activation treatment to obtain an all-solid-state battery containing the sulfide solid electrolyte in Example 6.

[0160] Example 8

[0161] This embodiment provides a sulfide solid electrolyte and an all-solid-state battery. The preparation method of the sulfide solid electrolyte is completely consistent with the preparation method mentioned in Example 3, and specifically includes the following steps:

[0162] (1)~(5) are the same as steps (1)~(5) in Example 3. The final sulfide solid electrolyte includes: sulfide matrix powder doped with rare earth compound Nd2S3 (mass of which is 1.0% of the required sulfide matrix powder mass), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the sulfide matrix powder, the thickness of which is 25nm.

[0163] (6) Same as step (6) in Example 1.

[0164] (7) Same as step (7) in Example 1.

[0165] (8) Battery assembly

[0166] In an argon glove box (oxygen content < 1 ppm, water content < 10 ppm), 10 sets of positive electrode sheets, 6 μm thick ceramic separators, sulfide solid electrolyte (28 μm thick) obtained in step (5) and negative electrode sheets were stacked in sequence. A layer of sulfide solid electrolyte (28 μm thick) obtained in step (5) was laid between each layer as an isolation and ion transport layer. The cells were placed in a soft-pack packaging shell and compacted under 600 MPa isostatic pressure for 10 min to complete the cell preparation. Then, the cells were kept at 1.2 MPa operating pressure for 20 min to complete the assembly of the 10-layer stacked high-capacity soft-pack all-solid-state battery. After the assembly was completed, the cells were kept at 65°C for 2 h for activation treatment to obtain an all-solid-state battery containing the sulfide solid electrolyte in Example 7.

[0167] Comparative Example 1

[0168] This embodiment provides a sulfide solid electrolyte, the preparation method of which specifically includes the following steps:

[0169] (1) Li2S, P2S5 and LiCl with a purity of 99.5% are mixed in a stoichiometric ratio of 5:1:1 and then anhydrous cyclohexane with a mass of 4 times the mass of the required sulfide matrix powder is added as a dispersant. After stirring evenly, the precursor slurry is obtained.

[0170] (2) Same as step (2) in Example 1.

[0171] (3) Same as step (3) in Example 1.

[0172] (4) The uniform particle size and non-agglomerated Li6PS5Cl sulfide matrix powder obtained in step (3) is directly used as sulfide solid electrolyte (without rare earth compound Nd2S3 and without coating layer), and sealed for later use.

[0173] (5) Same as step (6) in Example 1.

[0174] (6) Same as step (7) in Example 1.

[0175] (7) Following the same steps (8) as in Example 1, a fully solid-state battery containing the sulfide solid electrolyte of Comparative Example 1 is finally obtained.

[0176] Comparative Example 2

[0177] This embodiment provides a sulfide solid electrolyte, the preparation method of which specifically includes the following steps:

[0178] (1) Li2S, P2S5 and LiCl with a purity of 99.5% are mixed in a stoichiometric ratio of 5:1:1 and then anhydrous cyclohexane with a mass of 4 times the mass of the required sulfide matrix powder is added as a dispersant. After stirring evenly, the precursor slurry is obtained.

[0179] (2)~(5) are the same as steps (2)~(5) in Example 1.

[0180] The final sulfide solid electrolyte consists of: Li6PS5Cl sulfide matrix powder (without rare earth compound Nd2S3), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the Li6PS5Cl sulfide matrix powder, with a thickness of 15nm.

[0181] (6)~(8) are the same as steps (6)~(8) in Example 1, and finally an all-solid-state battery containing the sulfide solid electrolyte in Comparative Example 2 is obtained.

[0182] Comparative Example 3

[0183] This embodiment provides a sulfide solid electrolyte, the preparation method of which specifically includes the following steps:

[0184] (1)~(3) are the same as steps (1)~(3) in Example 1.

[0185] The uniform, non-agglomerated Li6PS5Cl sulfide matrix powder obtained in step (3) is directly used as the sulfide solid electrolyte. The sulfide matrix powder of the sulfide solid electrolyte is doped with rare earth compound Nd2S3 (0.5% of the required sulfide matrix powder mass) and has no coating layer.

[0186] (4) Same as step (6) in Example 1.

[0187] (5) Same as step (7) in Example 1.

[0188] (6) Following the same steps (8) as in Example 1, a fully solid-state battery containing the sulfide solid electrolyte of Comparative Example 3 is finally obtained.

[0189] Comparative Example 4

[0190] This embodiment provides a sulfide solid electrolyte, the preparation method of which is basically the same as the preparation method mentioned in Example 1, except that:

[0191] In step (1): Li2S, P2S5 and LiCl with a purity of 99.5% are mixed in a stoichiometric ratio of 5:1:1. Then, 2.5% of the mass of the required sulfide matrix powder, Nd2S3 rare earth compound and 4 times the mass of the required sulfide matrix powder, anhydrous cyclohexane are added as a dispersant. After stirring evenly, a precursor slurry is obtained.

[0192] The final sulfide solid electrolyte comprises: sulfide matrix powder doped with rare earth compound Nd2S3 (at a mass of 2.5% of the required sulfide matrix powder), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the sulfide matrix powder, the thickness of which is 15 nm.

[0193] The preparation of the positive electrode, negative electrode and battery assembly steps are the same as those in Example 1 (6) to (8), and finally an all-solid-state battery containing the sulfide solid electrolyte in Comparative Example 4 is obtained.

[0194] Comparative Example 5

[0195] This embodiment provides a sulfide solid electrolyte, the preparation method of which is basically the same as the preparation method mentioned in Example 1, except that:

[0196] In step (4), the Li6PS5Cl sulfide matrix powder is added to the composite coating solution at a solid-liquid ratio of 1:6 (g / mL). The mixture is stirred at a stirring speed of 250 rpm for 40 min until the Li6PS5Cl sulfide matrix powder is uniformly dispersed in the coating solution. Then, it is kept at 50℃ for 6 h to obtain the coating slurry through in-situ composite coating reaction.

[0197] The final sulfide solid electrolyte comprises: sulfide matrix powder doped with rare earth compound Nd2S3 (0.5% of the required sulfide matrix powder mass), and a composite coating layer composed of LiF and Al2O3 coated on the surface of the sulfide matrix powder, the thickness of which is 40 nm.

[0198] The preparation of the positive electrode, negative electrode and battery assembly steps are the same as those in Example 1 (6) to (8), and finally an all-solid-state battery containing the sulfide solid electrolyte in Comparative Example 5 is obtained.

[0199] Comparative Example 6

[0200] This embodiment provides a sulfide solid electrolyte, the preparation method of which is basically the same as the preparation method mentioned in Example 1, except that:

[0201] In step (3), the coarse powder of Li6PS5Cl sulfide is placed in an air jet mill and subjected to air jet milling treatment at a milling pressure of 0.7MPa, a feed rate of 12g / min, and a milling time of 12min to directly obtain Li6PS5Cl sulfide matrix powder; wherein, the particle size distribution of the Li6PS5Cl sulfide matrix powder is D 10 =0.8μm, D 50 =2.2μm and D 90 =2.8μm.

[0202] The preparation of the positive electrode, negative electrode and battery assembly steps are the same as those in Example 1 (6) to (8), and finally an all-solid-state battery containing the sulfide solid electrolyte in Comparative Example 6 is obtained.

[0203] Test Example 1

[0204] Ionic conductivity test: 100 mg of sulfide solid electrolyte was weighed and placed in a mold. A pressure of 360 MPa was applied to press it into an electrolyte sheet with a diameter of 10 mm. Under pressure, the impedance value of the sulfide solid electrolyte was measured using an electrochemical workstation at room temperature (25 °C) using the electrochemical impedance spectroscopy method. The real part of the minimum absolute value of multiple impedance phase angles was taken as the effective impedance value R. SE Using this effective impedance value, the ionic conductivity of the sulfide solid electrolyte is calculated. The calculation formula is: ,in, R represents the ionic conductivity (unit: mS / cm), L represents the thickness of the electrolyte sheet (unit: cm), and R represents the electrolyte thickness. SE The effective impedance value of the halide solid electrolyte obtained by electrochemical impedance spectroscopy (unit: Ω) is represented by S, which represents the cross-sectional area of ​​the electrolyte sheet (unit: cm²). 2 The test results of ionic conductivity are shown in Table 1.

[0205] Test Example 2

[0206] Fracture Toughness: The fracture toughness of sulfide solid electrolytes can be tested using the Vickers indentation method. Specifically, the sulfide solid electrolyte sample is first prepared to have a smooth surface to meet the surface finish requirements of the indentation test. Then, a known load is applied to the surface of the sulfide solid electrolyte sample using a Vickers diamond indenter to generate a controlled indentation. After the load is removed, the lengths of the two diagonals of the indentation and the lengths of the cracks extending from the four corners of the indentation are recorded using a microscopic measuring device. Based on the classical semi-empirical formula of fracture mechanics, the fracture toughness value of the sulfide solid electrolyte can be calculated by combining the lengths of the two diagonals of the indentation, the lengths of the cracks extending from the four corners of the indentation, and the load value. The entire test process is conducted in an environment with a temperature of 25°C and a dew point as low as -60°C to minimize the interference of moisture and temperature fluctuations on the fracture behavior of brittle electrolyte materials. The test results of fracture toughness are shown in Table 1.

[0207] Test Example 3

[0208] Interfacial Contact Rate: The interfacial contact rate of sulfide solid electrolytes is typically tested using electrochemical impedance spectroscopy (EIS). Specifically, the all-solid-state battery is connected to an electrochemical workstation, a small-amplitude AC signal is applied, and impedance spectrum data is acquired over a wide frequency range down to 10 MHz. After the test, the impedance data is fitted and analyzed using an equivalent circuit model to extract capacitance values ​​that reflect interfacial characteristics. These capacitance values ​​are used as a quantitative indicator to evaluate the interfacial contact rate; a larger capacitance value indicates a larger effective contact area and better interfacial contact. The core equipment required for this test is the electrochemical workstation, and the test process is conducted in an environment with a temperature of 25°C, a dew point as low as -60°C, and a pressure of 600 MPa. The test results for the interfacial contact rate are shown in Table 1.

[0209] Test Example 4

[0210] Compacted density: Compacted density can be tested using a powder compaction density meter. This method involves applying a constant pressure to the sulfide solid electrolyte and monitoring its volume change to achieve quantitative density measurement. Specifically, 100 mg of sulfide solid electrolyte is weighed and placed in a mold. The powder compaction density meter is then started, and a preset pressure of 600 MPa is applied to the sulfide solid electrolyte under standard test conditions of 25°C and a dew point of -60°C. The thickness of the powder after compaction is measured, and the compacted density is calculated by combining the initial mass of the sulfide solid electrolyte with the volume change before and after pressurization. The test results of compacted density are shown in Table 1.

[0211] Test Example 5

[0212] Cyclic performance testing: Cyclic performance testing was conducted on the all-solid-state battery under the following conditions: charge / discharge rate of 0.5C and voltage range of 2.5~4.3V. The results of the cycle performance testing are shown in Table 1.

[0213] Among them, the 800-cycle capacity retention rate refers to the percentage of the discharge capacity on the 800th charge-discharge cycle to the initial discharge capacity after 800 charge-discharge cycles of an all-solid-state battery. The calculation formula is: 800-cycle capacity retention rate = initial discharge capacity / 800th discharge capacity × 100%. It is used to measure the cycle stability of the battery. The higher the capacity retention rate, the better the integrity of the electrode structure, the interfacial compatibility between the electrolyte and the electrode, and the utilization rate of the active materials during multiple cycles, and the more guaranteed the battery's lifespan.

[0214] Test Example 7

[0215] Impedance increase test after 800 battery cycles: A composite test scheme combining cyclic charge-discharge testing and EIS was used to test the impedance increase of the battery after 800 cycles. The entire test process required the use of charge-discharge equipment and an electrochemical workstation, maintaining a constant temperature environment of 60°C and applying a constant external pressure of 1.2 MPa to the all-solid-state battery throughout. Specifically, firstly, the initial EIS data of the all-solid-state battery was collected to obtain the reference impedance. Then, a long-cycle test was carried out according to the preset charge-discharge steps, and capacity-related parameters were recorded simultaneously. The cycle was paused at fixed intervals (e.g., every 100 cycles) until the battery stabilized, and then the EIS test was performed again. After all 800 cycles were completed, the impedance measured after 800 cycles was compared with the reference impedance to calculate the impedance increase after 800 cycles. The results of the impedance increase test after 800 cycles are shown in Table 1.

[0216] Test Example 8

[0217] Charge / discharge efficiency testing: Charge / discharge efficiency usually refers to coulombic efficiency (i.e., capacity efficiency), which is calculated very directly: multiply the ratio of the discharge capacity to the charge capacity measured in the same charge / discharge cycle by 100%. Specifically, constant current constant voltage (CC-CV) charging mode is used. The charging capacity actually includes two parts: the amount of electricity charged in the constant current (CC) stage and the amount of electricity charged in the constant voltage (CV) stage, while the discharge capacity is the amount of electricity released in the constant current discharge stage. The equipment required for testing is a battery charge / discharge testing system. The test environment temperature is 60±2℃, and a constant external pressure of 1.2MPa is applied to the all-solid-state battery. Specifically, first, the all-solid-state battery under test is connected to the charge / discharge tester. Then, the charge / discharge operation mode, voltage cutoff threshold, and corresponding current rate parameters are set on the charge / discharge tester. The charge / discharge testing system automatically calculates the charge / discharge capacity based on the real-time current-time integral results. Selecting stable cycle data at 0.5C rate, the charge / discharge efficiency under that condition is obtained by directly dividing the discharge capacity value by the charge capacity value. The results of the charge and discharge efficiency tests are shown in Table 1.

[0218] Table 1 Performance Test Results

[0219]

[0220] It should be noted that the all-solid-state batteries in Examples 6 to 8 are multi-layer stacked batteries, and the first-cycle discharge capacity is the sum of the first-cycle discharge capacities of the multi-layer batteries.

[0221] Based on Table 1, the following conclusions can be drawn:

[0222] The ionic conductivity of Examples 1 to 8 (all referring to the ionic conductivity, fracture toughness, interfacial contact rate, compaction density, first-cycle discharge capacity, capacity retention after 800 cycles, impedance increase after 800 cycles, and charge / discharge efficiency of the corresponding sulfide solid electrolyte / all-solid-state battery provided in the corresponding examples / proportions, which will not be elaborated further below) is 1.3 × 10⁻⁶. - 3 S / cm ~ 1.4 × 10 -3 Between S / cm, the average ionic conductivity can reach 1.37 × 10⁻⁶. -3 S / cm, much higher than the highest electronic conductivity in the comparative example (1.12 × 10⁻⁶ in Comparative Example 3). -3 The ionic conductivity (S / cm) is superior, with a 32.7% increase compared to Comparative Example 1, which is undoped with rare earth compounds and not coated with LiF-Al2O3.

[0223] The fracture toughness of Examples 1 to 8 is 1.2 MPa·m. 1 / 2 ~1.4MPa·m 1 / 2 Between these values, the average fracture toughness can reach 1.34 MPa·m. 1 / 2 This is significantly higher than the highest fracture toughness in the comparative example (1.1 MPa·m in Comparative Example 5). 1 / 2 The sulfide solid electrolyte it provides has excellent mechanical toughness. Compared with the undoped rare earth compound and uncoated LiF-Al2O3 coating, the fracture toughness is improved by more than 71.4%.

[0224] The interface contact rates of Examples 1 to 8 were between 98.00% and 98.50%, with an average interface contact rate of 98.31%, which was much higher than the highest interface contact rate in the comparative examples (90.2% of Comparative Example 2). Compared with Comparative Example 1, which was not doped with rare earth compounds and was not coated with LiF-Al2O3, the interface contact rate was increased by more than 23.3%.

[0225] The capacity retention rates after 800 cycles in Examples 1 to 8 ranged from 86.5% to 89.00%, with an average capacity retention rate of 87.94%, which is much higher than the capacity retention rate after 800 cycles in the comparative examples (76.8% in Comparative Example 3). The high-capacity soft-pack all-solid-state battery prepared based on the sulfide solid electrolyte provided has excellent cycle stability. Compared with Comparative Example 1, which did not have rare earth compounds and was not coated with a LiF-Al2O3 coating layer, the capacity retention rate after 800 cycles was improved by more than 56.3%.

[0226] Based on the analysis of Examples 6 to 8, it can be seen that the sulfide solid electrolyte provided in this application can be adapted to multi-layer stacked structures from single layer to 10 layers. The capacity of the multi-layer battery increases linearly with the number of stacked layers. The interlayer contact is good, and there is no interface failure or particle breakage. Compared with existing stacked batteries, the capacity stacking effect is better and the stability is stronger, which can meet the application scenarios with different capacity requirements such as high-end vehicle and large-scale energy storage.

[0227] Based on the analysis of Comparative Examples 1 to 3, it can be seen that both the doping of rare earth compound Nd2S3 and the coating of LiF-Al2O3 composite coating layer are indispensable. If only the LiF-Al2O3 composite coating layer is coated without the doping of rare earth compound Nd2S3 (Comparative Example 2) or only the doping of rare earth compound Nd2S3 is coated without the coating of LiF-Al2O3 composite coating layer (Comparative Example 3), the performance of the sulfide solid electrolyte and the all-solid-state battery are significantly lower than those of the embodiments of this application, which further proves that the synergistic effect of the two can achieve simultaneous improvement in mechanical toughness, ionic conductivity and interfacial compatibility.

[0228] Based on the analysis of Comparative Examples 4 to 6, it can be seen that the doping amount of rare earth compound Nd2S3, the thickness of LiF-Al2O3 composite coating layer, and the particle size distribution of sulfide matrix powder all have a clear optimal range. If the doping is excessive, the coating is too thick, or the particle size distribution is improper, it will lead to a decrease in ionic conductivity, a decrease in mechanical toughness, and a deterioration in interfacial contact rate, thereby affecting the capacity and cycle stability of all-solid-state batteries.

[0229] Furthermore, none of the all-solid-state batteries provided in Examples 1 to 8 exhibited short circuits or thermal runaway during nail penetration tests. No interface failures or electrolyte fragmentation were observed during operation, demonstrating their suitability for high-capacity pouch all-solid-state batteries. Among these, the all-solid-state battery provided in Example 3 achieved the best performance. The all-solid-state batteries provided in Examples 6 to 8 showed good interlayer contact in their electrolytes, indicating that the sulfide solid electrolyte provided in this application is adaptable to multi-layer stacked structures, exhibiting excellent and stable capacity stacking effects, and meeting the ultra-high capacity requirements of large-scale energy storage and high-end automotive applications.

[0230] Conversely, the all-solid-state battery provided in Comparative Example 1 was prone to short circuits during nail penetration testing, and exhibited electrolyte fragmentation, interlayer delamination, and interface failure after 400 cycles. Some particles were damaged after preparation under 600 MPa isostatic pressure, resulting in performance far below that of the embodiments in this application. While the other all-solid-state batteries provided in the comparative examples did not short circuit during nail penetration testing, the all-solid-state battery provided in Comparative Example 2 showed slight electrolyte fragmentation and interface detachment after 600 cycles. The all-solid-state battery provided in Comparative Example 3 exhibited significant interfacial side reactions after 500 cycles, generating an insulating impurity film, which reduced battery capacity. Rapid degradation; Comparative Example 4 shows that due to excessive rare earth compound doping, some Nd2S3 agglomerates, which undergoes slight side reactions with the sulfide matrix powder, reducing electrolyte stability and significantly decreasing battery cycle performance; Comparative Example 5 shows that due to excessively thick composite coating, lithium-ion conduction is hindered, leading to a decrease in electrolyte ionic conductivity, battery capacity, and cycle stability; Comparative Example 6 shows that due to abnormal particle size distribution, uneven electrolyte particle packing, decreased compaction density, poor interlayer contact, and obstructed ion transport, as well as reduced mechanical toughness, particle breakage is prone to occur during cycling.

[0231] In summary, the sulfide solid electrolyte provided in this application solves the problem of high mechanical brittleness of existing sulfide solid electrolytes through the synergistic effect of doping with rare earth compound Nd2S3 and coating with LiF-Al2O3 composite coating layer, thereby improving the mechanical toughness, ionic conductivity and interfacial compatibility of the sulfide solid electrolyte and enhancing its overall performance.

[0232] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention 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 changes can be made without departing from its scope.

Claims

1. A sulfide solid electrolyte, characterized in that, include: The sulfide matrix powder and the composite coating layer; wherein the sulfide matrix powder is doped with rare earth compounds, and the composite coating layer composed of LiF and Al2O3 coats the surface of the sulfide matrix powder. The particle size distribution of the sulfide matrix powder includes: D 10 =1.0μm~1.4μm、D 50 =1.5μm~1.9μm and D 90 =2.0μm~2.4μm.

2. The sulfide solid electrolyte according to claim 1, characterized in that, The rare earth compound is Nd2S3; And / or, The mass of the rare earth compound is 0.5% to 2% of the mass of the sulfide matrix powder.

3. The sulfide solid electrolyte according to claim 1 or 2, characterized in that, The thickness of the composite coating layer is 15nm~35nm.

4. A method for preparing a sulfide solid electrolyte as described in any one of claims 1 to 3, characterized in that, include: The pre-obtained coarse sulfide powder is pulverized by air jet milling and then sieved through a three-stage classifying sieve to obtain the sulfide-based powder. The mesh size of the three-stage classifying sieve decreases sequentially along the sieving direction, and the particle size distribution of the sulfide-based powder includes: D 10 =1.0μm~1.4μm, D 50 =1.5μm~1.9μm and D 90 =2.0μm~2.4μm; The sulfide matrix powder is added to a composite coating solution obtained from LiF and Al2O3, and a coating slurry is obtained through an in-situ composite coating reaction. The coating slurry was heated and then vacuum dried to obtain the sulfide solid electrolyte.

5. The method according to claim 4, characterized in that, The method further includes: After mixing Li2S, P2S5, and LiCl, a rare earth compound and a dispersant are added to obtain a precursor slurry; wherein the rare earth compound is Nd2S3 and the dispersant is anhydrous cyclohexane. The precursor slurry was ball-milled, vacuum-dried, and then sintered at a constant temperature in an inert gas environment. After grinding and sieving, coarse sulfide powder was obtained.

6. The method according to claim 4 or 5, characterized in that, The step of adding the sulfide matrix powder to a composite coating solution obtained from LiF and Al2O3, and then performing an in-situ composite coating reaction to obtain a coating slurry includes: After mixing LiF and Al2O3, anhydrous cyclohexane was added to obtain the composite coating solution; The sulfide matrix powder is added to the composite coating solution according to a preset solid-liquid ratio, stirred and dispersed evenly, and then subjected to heat preservation treatment. The coating slurry is obtained through in-situ composite coating reaction.

7. The method according to claim 6, characterized in that, During the heat preservation process, the heat preservation time is 3h to 5h, and / or the heat preservation temperature is 50℃ to 70℃.

8. An all-solid-state battery, characterized in that, include: A positive electrode, a negative electrode, and a sulfide solid electrolyte as described in any one of claims 1 to 3, or a sulfide solid electrolyte prepared by the method as described in any one of claims 4 to 7.

9. An electrical appliance, characterized in that, include: The main body of the device and the all-solid-state battery as described in claim 8.

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