Composite solid electrolyte material and preparation method and application thereof

Abstract

The application discloses a kind of composite solid electrolyte material and its preparation method and application.The material is core-shell structure, including sulfide solid electrolyte core and the amorphous lithium ion conductive shell of coating in the core surface, by mechanical force chemical reaction made from sulfide solid electrolyte and van der waals crystal, while consuming the inert layer of sulfide solid electrolyte surface, in-situ generation amorphous lithium ion conductive shell.The application is through mechanical force chemical "reaction consumption-in-situ construction" integration strategy, while effectively removing the harmful substances on the surface of sulfide solid electrolyte, constructs the amorphous protective layer with high ionic conductivity and high oxidation potential, significantly improves the interface compatibility of sulfide solid electrolyte and high-voltage positive material.Preparation method process is simple, environmental protection, easy to scale production, the obtained composite solid electrolyte material is used for solid-state battery, can effectively improve the cycle life, rate performance and coulomb efficiency of battery.

Description

Technical Field

[0001] This invention belongs to the field of solid-state battery technology, and relates to a composite solid-state electrolyte material, its preparation method and application. Specifically, it relates to a method for in-situ constructing an amorphous lithium-ion conductive layer on the surface of a sulfide solid electrolyte through a mechanochemical reaction, as well as the composite solid-state electrolyte material obtained therefrom and an all-solid-state battery containing the material. Background Technology

[0002] With the increasing demand for energy density in new energy vehicles and consumer electronics, solid-state batteries based on solid-state electrolytes are considered one of the core directions of next-generation energy storage technology. Sulfide solid-state electrolytes (such as Li6PS5Cl, Li...) 10 GeP2S 12 Li3PS4, etc., have extremely high room temperature ionic conductivity (up to 10). -2 Sulfide solid electrolytes (S / cm scale) and good mechanical ductility have made them a research hotspot in the field of all-solid-state batteries. However, sulfide solid electrolytes have two major bottlenecks: one is a narrow electrochemical window, especially a low oxidation potential (typically below 2.5V vs. Li). + When matched with high-voltage cathode materials (such as NCM811, NCA, etc., with an operating voltage > 4.2V), the electrolyte will undergo oxidative decomposition at the cathode interface, resulting in a sharp increase in interfacial impedance and rapid capacity decay. Secondly, it has poor air stability and its surface is prone to react with moisture to form H2S and inert layers such as lithium phosphate, lithium hydroxide, or lithium carbonate, which further deteriorates the interfacial performance. Therefore, the preparation of traditional sulfide electrolytes usually requires glove boxes or dry rooms with dew points below -60°C to avoid hydrolysis reactions, which greatly increases equipment investment and operating costs, limiting its large-scale application.

[0003] To address the aforementioned issues, existing technologies have attempted to dope sulfide electrolytes with elements or coat the cathode surface. For example, Chinese patent application CN 115516576 A introduces oxygen into the sulfide electrolyte to improve the interfacial stability between the material and the cathode. However, the introduction of oxygen leads to the formation of impurity phases, increasing ion transport impedance. Chinese patent application CN 112074978 A coats the cathode material with a LiNbO3 layer to reduce the interfacial impedance between the cathode and sulfide. However, this coating cannot prevent the sulfide electrolyte from contacting the conductive carbon within the cathode sheet, thus failing to effectively solve the problem of sulfide electrolyte oxidation and decomposition. Therefore, developing a simple, efficient protective layer capable of in-situ constructing a highly oxidation-resistant and highly ionicly conductive protective layer on the sulfide electrolyte surface is of great significance for promoting the industrialization of high-voltage all-solid-state batteries. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a composite solid electrolyte material with high oxidation potential resistance, good interface stability, and high tolerance to humidity in the preparation environment, as well as its preparation method and application.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A composite solid electrolyte material includes a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell coating the surface of the sulfide solid electrolyte core. The composite solid electrolyte material is generated by a mechanochemical reaction between the sulfide solid electrolyte and van der Waals crystals. The surface of the sulfide solid electrolyte has an inert layer, which is generated by the reaction of the sulfide solid electrolyte with air. The mechanochemical reaction consumes the inert layer while simultaneously generating an amorphous lithium-ion conductive shell in situ on the surface of the sulfide solid electrolyte, thereby improving the oxidation resistance of the sulfide solid electrolyte.

[0006] The design concept of the above technical solution lies in the fact that this invention constructs a unique "sulfide core-amorphous shell" core-shell structure, enabling the composite solid electrolyte to possess both high ionic conductivity and high oxidation resistance potential. The sulfide core provides high lithium-ion conductivity, while the amorphous lithium-ion conductor shell plays multiple key roles: Firstly, this shell layer has a wide electrochemical window (oxidation resistance potential > 4.0V), effectively isolating the sulfide core from direct contact with the high-voltage positive electrode, preventing the sulfide from being oxidized at the positive electrode interface; secondly, the amorphous structure eliminates grain boundary impedance, providing isotropic lithium-ion transport channels, enabling rapid lithium-ion conduction; furthermore, this shell layer originates from the in-situ conversion of harmful inert layers (such as lithium carbonate or lithium hydroxide) on the surface of the sulfide solid electrolyte, achieving resource utilization by "turning waste into treasure," while simultaneously reducing the humidity requirements of the processing environment for the sulfide electrolyte.

[0007] The amorphous lithium-ion conductive shell, with its amorphous structure, possesses advantages such as isotropy, absence of grain boundary impedance, tight bonding with the core, and adaptability to volume changes during charging and discharging. In mechanical force (e.g., mechanical ball milling) chemical reactions, the strong mechanical force causes interlayer exfoliation, lattice distortion, and chemical bond breakage in van der Waals crystals, generating numerous fresh surfaces and active sites. Simultaneously, inert substances such as lithium phosphate, lithium hydroxide, and lithium carbonate, generated on the surface of the sulfide solid electrolyte due to water absorption, are activated. Both react in a solid-phase reaction, and the reaction products are deposited in situ on the sulfide surface, forming a uniform and dense coating layer. This integrated "reaction consumption-in-situ construction" strategy effectively removes harmful inert layers while simultaneously constructing a protective layer with high ionic conductivity and high oxidation potential resistance.

[0008] It is particularly noteworthy that, because van der Waals crystals can react with common hydrolysis products on sulfide surfaces, such as inert substances like Li3PO4, LiOH, and Li2CO3, transforming them into amorphous complexes with lithium-ion conductivity, the preparation method of this invention significantly reduces the requirements for the initial surface state of the sulfide electrolyte. Even if the sulfide electrolyte undergoes slight surface hydrolysis in the preceding process, these harmful inert layers can be consumed in situ and transformed into a functional conductive shell. This characteristic overcomes the limitation that traditional sulfide electrolytes must be processed in an ultra-low dew point (<-60°C) environment, allowing material preparation to be completed in lower-cost dry rooms or even ordinary drying rooms, thereby greatly reducing the manufacturing cost of sulfide electrolytes and clearing a key obstacle for their large-scale industrial application.

[0009] As a further preferred embodiment of the above technical solution, the inert layer comprises one or more of lithium carbonate, lithium hydroxide, lithium phosphate, and lithium chloride, and the total content of the inert layer in the sulfide solid electrolyte is ≤5 wt%. The inert layer is formed by the reaction of the sulfide electrolyte with water, carbon dioxide, etc., in the air. If the content is too high, it indicates severe decomposition of the sulfide electrolyte, and the ionic conductivity will drop sharply or even lose its ability to conduct lithium ions. The lower the content of the inert layer, the better the performance of the solid electrolyte material. However, low-content inert layers require extremely stringent preparation environments (requiring ultra-low dew points <-60°C). The solution of this invention relaxes the requirements for the preparation environment, and appropriately controlling the content of the inert layer can better ensure the excellent electrical performance of the final composite solid electrolyte.

[0010] As a further preferred embodiment of the above technical solution, the van der Waals crystal is a type of zero-dimensional, one-dimensional, or two-dimensional material composed of atoms stacked together by van der Waals forces, with the general chemical formula M. a X b Y c Where M is selected from transition metal elements, X is selected from halogen elements, Y is selected from oxygen or nitrogen elements, and a, b, and c are integers, with a > 0, b > 0, and c ≥ 0.

[0011] As a further preferred embodiment of the above technical solution, the transition metal element is one or more of Mo, W, Ti, Ru, Ta, Zr, Nb and Al; the halogen element is one or more of Cl, Br and I.

[0012] As a further preferred embodiment of the above technical solution, the van der Waals crystal is one or more of titanium tetrachloride (TiCl4), ruthenium trichloride (RuCl3), tantalum pentachloride (TaCl5), zirconium tetrachloride (ZrCl4), niobium pentachloride (NbCl5), aluminum trichloride (AlCl3), and niobium oxychloride (NbOCl3). These van der Waals crystals possess unique structures and chemical reactivity, enabling them to undergo highly efficient reactions under mechanical force, making them particularly suitable for the solutions described in this invention.

[0013] As a further preferred embodiment of the above technical solution, the sulfide solid electrolyte is selected from one or more of the following: silver-germanium sulfide structure, LGPS structure, and (1-j)Li2S-(j)P2S5 binary glass / glass-ceramic system, wherein 1>j>0.

[0014] As a further optimization of the above technical solution, the preferred structure of the sulfide-silver-germanium ore type is Li. 6-k PS 5-k N 1+k N is selected from at least one of the halogen elements, 1≥k≥0; the LGPS type structure preferably uses Li. 10 GeP2S 12 Li2S-P2S5 and its derivatives; (1-j)Li2S-(j)P2S5 binary glass / glass ceramic system preferred Li2S-P2S5 binary glass / glass ceramic system and its derivatives.

[0015] As a further preferred embodiment of the above technical solution, the thickness of the amorphous lithium-ion conductive shell is 1 nm to 200 nm. A preferred shell thickness range is 2 nm to 50 nm, and more preferably 5 nm to 20 nm. If the shell is too thin (<2 nm), it cannot completely cover the core surface, making it difficult to effectively suppress oxidation; if the shell is too thick, it will reduce the overall ionic conductivity.

[0016] As a further preferred embodiment of the above technical solution, the particle size of the composite solid electrolyte material is 0.1μm to 30μm, and more preferably 1μm to 15μm.

[0017] Based on the same technical concept, the present invention also provides a method for preparing the above-mentioned composite solid electrolyte material, comprising the following steps: mechanically ball-milling a sulfide solid electrolyte and a van der Waals crystal, so that the van der Waals crystal and the inert layer on the surface of the sulfide solid electrolyte undergo a mechanochemical reaction, thereby consuming the inert layer and generating an amorphous lithium-ion conductive shell in situ on the surface of the sulfide solid electrolyte.

[0018] This preparation method is simple, low-cost, and easy to scale up. A sulfide solid electrolyte is mixed with a small amount of van der Waals crystals, and a solid-phase reaction is induced by mechanical ball milling. During ball milling, mechanical energy is converted into chemical energy, driving the van der Waals crystals to react with the sulfide surface. The reaction products coat the sulfide surface in situ, forming a conductive shell. The entire process requires no solvents, no subsequent heat treatment, and generates no wastewater, making it a green and environmentally friendly modification method.

[0019] As a further preferred embodiment of the above technical solution, the amount of van der Waals crystal added accounts for 0.05% to 5% of the mass of the sulfide solid electrolyte. If the amount added is too small, a complete outer shell cannot be formed; if the amount added is too large, the surface layer will be too thick, and the overall lithium-ion conductivity will decrease. This is because the ionic conductivity of the sulfide electrolyte is higher than that of the outer amorphous coating layer. If the coating layer is too thick and its proportion increases, the overall conductivity of the electrolyte will decrease.

[0020] As a further preferred embodiment of the above technical solution, the rotational speed of the mechanical ball mill is 100 rpm to 1000 rpm, preferably 200 rpm to 500 rpm; the milling time is 0.5 h to 20 h, preferably 2 h to 8 h; the milling media are zirconia balls or agate balls, and the ball-to-material ratio is 5 to 50:1, preferably 10 to 30:1. The ball milling process can be carried out under an inert atmosphere (such as argon or nitrogen), but compared with traditional methods, the tolerance to residual moisture in the atmosphere is significantly improved. By optimizing the ball milling process parameters, the degree of reaction can be controlled to avoid excessive reaction leading to excessive enrichment of lithium halides, ensuring that the outer shell layer exists in a stable amorphous composite form.

[0021] Based on the same technical concept, the present invention also provides an application of the above-mentioned composite solid electrolyte material or the composite solid electrolyte material prepared by the above-mentioned preparation method. The composite solid electrolyte material is used to make solid batteries, especially sulfide-based all-solid batteries that are matched with high-voltage cathode materials. The high-voltage cathode material is a cathode material with a working voltage >4.2V, such as NCM811, NCA, etc.

[0022] As a further preferred embodiment of the above technical solution, the solid-state battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte membrane; the preparation steps of the positive electrode sheet include: mixing the composite solid electrolyte material with a high-voltage positive electrode active material, a conductive agent, and a binder, preparing a positive electrode mixture through a dry or wet process, then compositing it with aluminum foil, and obtaining the positive electrode sheet by rolling and cutting.

[0023] Compared with the prior art, the advantages of the present invention are as follows: (1) The composite solid electrolyte material of the present invention comprises a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell coated on the surface of the sulfide solid electrolyte core. The composite solid electrolyte material is generated by a mechanochemical reaction between the sulfide solid electrolyte and van der Waals crystals. While consuming the inert layer on the sulfide surface, an amorphous lithium-ion conductive shell with both high ionic conductivity and high oxidation resistance potential is generated in situ. The shell layer has a wide electrochemical window (>4.0V), excellent oxidation resistance, and effectively improves the compatibility between the sulfide electrolyte and the high-voltage cathode. The amorphous structure of the shell eliminates grain boundary impedance, has isotropic lithium-ion transport characteristics, and is tightly bonded to the core. It can adapt to volume changes during charging and discharging, which is beneficial to improving long-term cycle stability.

[0024] (2) The preparation method of the composite solid electrolyte material of the present invention is simple and environmentally friendly. It is completed in one step by mechanical ball milling, without solvents, subsequent heat treatment, or wastewater generation. The process window is wide and it is easy to scale up production. Because the present invention utilizes the mechanochemical reaction between van der Waals crystals and the inert layer (such as lithium phosphate, lithium hydroxide, lithium carbonate, etc.) generated by water absorption on the surface of sulfides, it transforms them in situ into an amorphous shell with lithium-ion conductivity. This characteristic allows the preparation and processing of sulfide electrolytes to be carried out in a relatively high humidity environment (such as a dry room environment with a dew point of -20℃ to -40℃), without the need for expensive ultra-low dew point (below -60℃) drying rooms, which greatly reduces the manufacturing cost of sulfide electrolytes and provides a practical and feasible technical path for their large-scale industrial application.

[0025] (3) The composite solid electrolyte material of the present invention can be used to make solid batteries, especially suitable for high-voltage all-solid batteries, which can significantly improve the cycle life, rate performance and coulombic efficiency of the battery. Because the composite solid electrolyte obtained by the present invention has an amorphous lithium-ion conductor shell formed in situ on the surface, it has good chemical compatibility and interface stability with high-voltage cathode materials, and can effectively inhibit the oxidative decomposition of sulfide electrolytes. Detailed Implementation

[0026] The present invention will be further described below with reference to specific preferred embodiments, but this does not limit the scope of protection of the present invention. Unless otherwise specified, the materials and instruments used in the following embodiments and comparative examples are commercially available, the grinding jar is made of zirconium oxide, the grinding media is zirconium oxide balls (3 mm in diameter), and the ball-to-material ratio is 20:1.

[0027] Example 1: A composite solid electrolyte material of the present invention includes a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell. The sulfide solid electrolyte is Li6PS5Cl (D50 particle size is 5μm); the shell layer generated by in-situ reaction has a thickness of about 25nm and is an amorphous lithium-ion conductive layer generated by the reaction of tantalum pentachloride (TaCl5) with the sulfide surface.

[0028] A method for preparing a composite solid electrolyte material according to this embodiment includes the following steps: Li6PS5Cl electrolyte is refined to a D50 of 5 μm using a ball mill, and then separated into electrolyte powder by sieving. The entire process is carried out in a drying room with a dew point of -40°C. XRD quantitative analysis determines that the surface lithium salt (i.e., inert layer) content is approximately 2.5 wt%. The electrolyte is further added to a planetary ball mill with TaCl5 at a mass ratio of 97.5:2.5. The mixture is ball-milled at 300 rpm for 4 hours under an inert atmosphere to obtain the composite solid electrolyte material.

[0029] Example 2: A composite solid electrolyte material of the present invention comprises a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell. The sulfide solid electrolyte is Li. 10 GeP2S 12 (D50 particle size is 3μm); the shell layer generated by the in-situ reaction is about 25nm thick, which is an amorphous lithium-ion conductor layer generated by the reaction of aluminum trichloride (AlCl3) with the sulfide surface.

[0030] A method for preparing a composite solid electrolyte material according to this embodiment includes the following steps: Li 10 GeP2S 12 The electrolyte was refined to a D50 of 3 μm using a ball mill, and then separated into electrolyte powder by sieving. The entire process was carried out in a drying room at a dew point of -40℃. XRD quantitative analysis determined that the content of surface lithium salt (i.e., inert layer) was about 2.0 wt%. It was then added to a planetary ball mill with van der Waals crystals AlCl3 at a mass ratio of 98:2. The ball milling speed was 250 rpm and the time was 6 hours.

[0031] Example 3: A composite solid electrolyte material of the present invention comprises a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell. The sulfide solid electrolyte is Li. 5.5 PS 4.5 Cl 1.5 (D50 particle size is 2μm); the shell generated by the in-situ reaction is about 30nm thick, which is an amorphous lithium-ion conductor layer generated by the reaction of ruthenium trichloride (RuCl3) with the sulfide surface.

[0032] A method for preparing a composite solid electrolyte material according to this embodiment includes the following steps: refining Li6PS5Cl electrolyte to a D50 of 2μm using a ball mill, then separating the ball material by sieving to obtain electrolyte powder. The entire process is carried out in a drying room with a dew point of -40℃. The content of surface lithium salt (i.e., inert layer) is determined to be about 4.0wt% by XRD quantitative analysis. Further, it is added to a planetary ball mill with van der Waals crystal RuCl3 at a mass ratio of 96:4. The ball milling speed is 350rpm and the time is 3 hours.

[0033] Example 4: A composite solid electrolyte material of the present invention includes a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell. The sulfide solid electrolyte is 0.75Li2S-0.25P2S5 (D50 particle size is 1μm); the shell layer generated by in-situ reaction has a thickness of about 5nm and is an amorphous lithium-ion conductive layer generated by the reaction of titanium tetrachloride (TiCl4) with the sulfide surface.

[0034] A method for preparing a composite solid electrolyte material according to this embodiment includes the following steps: refining 0.75Li2S-0.25P2S5 electrolyte to a D50 of 1μm using a dry mill, the entire process being carried out in a drying room at -50℃ dew point, and determining the surface lithium salt (i.e., inert layer) content to be approximately 0.6wt% by XRD quantitative analysis, and further adding it to a ball mill jar with van der Waals crystal TiCl4 at a mass ratio of 99.4:0.6 (TiCl4 is liquid and added using a micro-syringe), with a ball-to-material ratio of 10:1, and ball milling at 200rpm for 8 hours.

[0035] Example 5: A composite solid electrolyte material of the present invention comprises a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell. The sulfide solid electrolyte is Li. 5.4 PS 4.4 Cl 0.8 Br 0.8 (D50 particle size is 10μm); the shell generated by the in-situ reaction is about 12nm thick, which is an amorphous lithium-ion conductor layer generated by the reaction of tantalum pentachloride (TaCl5) with the sulfide surface.

[0036] A method for preparing a composite solid electrolyte material according to this embodiment includes the following steps: Li 5.4 PS 4.4 Cl 0.8 Br 0.8Electrolyte powder was fined to a D50 of 10 μm using a pulverizer, and then separated into powder and granules by sieving. The entire process was carried out in a drying room at -50°C dew point. XRD quantitative analysis determined that the content of surface lithium salt (i.e., inert layer) was approximately 0.5 wt%. The powder was then added to a ball mill jar with van der Waals crystals TaCl5 at a mass ratio of 99.5:0.5 and a ball-to-powder ratio of 30:1. The mixture was ball-milled at 400 rpm for 2 hours.

[0037] Example 6: A composite solid electrolyte material of the present invention comprises a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell. The sulfide solid electrolyte is Li. 10 GeP2S 12 (D50 particle size is 5μm); the shell layer generated by the in-situ reaction is about 40nm thick, which is an amorphous lithium-ion conductor layer generated by the reaction of zirconium tetrachloride (ZrCl4) with the sulfide surface.

[0038] A method for preparing a composite solid electrolyte material according to this embodiment includes the following steps: Li 10 GeP2S 12 The electrolyte was refined to a D50 of 5 μm using a ball mill, and then separated into electrolyte powder by sieving. The entire process was carried out in a drying room at a dew point of -40℃. XRD quantitative analysis determined that the content of surface lithium salt (i.e., inert layer) was about 4 wt%. It was then added to a ball mill jar with van der Waals crystal ZrCl4 at a mass ratio of 96:4 and a ball-to-material ratio of 20:1, and ball-milled at 300 rpm for 5 hours.

[0039] Example 7: A composite solid electrolyte material of the present invention includes a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell. The sulfide solid electrolyte is Li6PS5Cl (D50 particle size is 5μm); the shell layer generated by in-situ reaction has a thickness of about 50nm and is an amorphous lithium-ion conductive layer generated by the reaction of niobium pentachloride (NbCl5) with the sulfide surface.

[0040] A method for preparing a composite solid electrolyte material according to this embodiment includes the following steps: refining Li6PS5Cl electrolyte to a D50 of 5μm using a ball mill, then separating the ball and material by sieving to obtain electrolyte powder. The entire process is carried out in a drying room with a dew point of -40℃. The content of surface lithium salt (i.e., inert layer) is determined to be about 3wt% by XRD quantitative analysis. It is further added to a ball mill jar with van der Waals crystal NbCl5 at a mass ratio of 97:3 and a ball-to-material ratio of 25:1, and ball milled at 350rpm for 4 hours.

[0041] Example 8: A composite solid electrolyte material of the present invention includes a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell. The sulfide solid electrolyte is 0.7Li2S-0.3P2S5 (D50 particle size is 2μm); the shell layer generated by in-situ reaction has a thickness of about 3nm and is an amorphous lithium-ion conductive layer generated by the reaction of niobium oxychloride (NbOCl3) with the sulfide surface.

[0042] A method for preparing a composite solid electrolyte material according to this embodiment includes the following steps: refining 0.7Li2S-0.3P2S5 electrolyte to a D50 of 2μm using a dry mill, the entire process being carried out in a drying room with a dew point of -60℃, and determining the content of surface lithium salt (i.e., inert layer) to be approximately 0.2wt% by XRD quantitative analysis, and further adding it to a ball mill jar with van der Waals crystal NbOCl3 at a mass ratio of 99.8:0.2, with a ball-to-material ratio of 15:1, and ball milling at 250rpm for 6 hours.

[0043] Comparative Example 1: A solid electrolyte material, namely Li6PS5Cl sulfide solid electrolyte, was ground and refined only according to the same method as in Example 1, without undergoing a mechanochemical reaction with van der Waals crystals.

[0044] Comparative Example 2: A composite solid electrolyte material is prepared using a conventional coating method: the same sulfide solid electrolyte Li6PS5Cl as in Example 1 is heat-treated at 200°C for 30 min in nitrogen containing 1000 ppm oxygen to obtain an oxygen-doped sulfide electrolyte. This process is carried out in a glove box.

[0045] Comparative Example 3: A composite solid electrolyte material was prepared by ball milling the same sulfide solid electrolyte Li6PS5Cl as in Example 1 in a -30°C dew point drying room. The content of its inert lithium salt (i.e., inert layer) was approximately 6 wt% by XRD quantitative analysis. Other treatments were completely consistent with those in Example 1.

[0046] Oxidation resistance potential was tested using linear sweep voltammetry (LSV). The electrolyte materials of each embodiment and comparative example were mixed with conductive carbon at a mass ratio of 80:20 and pressed into sheets (10 mm in diameter, 300 MPa pressure) as working electrodes. Li6PS5Cl powder was pressed into sheets (10 mm in diameter, 300 MPa pressure) as the separator layer. Lithium metal was used as the counter electrode and reference electrode. LSV tests were performed at 60 °C with a scan rate of 0.1 mV / s to determine the oxidation decomposition initiation potential. The results are shown in the table below: Table 1. Oxidative decomposition initiation potentials of electrolyte materials in Examples 1-8 and Comparative Examples 1-3

[0047] The results in Table 1 show that the oxidation decomposition initiation potential of the composite solid electrolyte materials in each embodiment of the present invention is increased to above 4.1V, which is significantly higher than that of the untreated sulfide in Comparative Example 1 and the electrolyte material treated by conventional methods in Comparative Example 2, effectively meeting the requirements for the use of high-voltage cathode materials (such as NCM811, charging voltage 4.3V).

[0048] All-solid-state battery performance test: The solid electrolyte materials used in each embodiment and comparative example were assembled into all-solid-state batteries for performance testing. The positive electrode NCM811, the electrolyte material from each embodiment or comparative example, and conductive carbon were mixed in a ratio of 70:25:5 and then pressed into sheets under a pressure of 300 MPa. The negative electrode used a lithium-indium alloy, and the electrolyte sheet was made of Li6PS5Cl and pressed into sheets under a pressure of 300 MPa. The batteries were cycle-tested at 60°C and 0.2C, and the results are shown in the table below: Table 2. Electrical performance of all-solid-state batteries assembled with electrolyte materials from Examples 1-8 and Comparative Examples 1-3.

[0049] As shown in Table 2, the composite solid-state electrolyte materials of the various embodiments of the present invention exhibit significant improvements in rate performance and cycle stability compared to the comparative examples. The rate efficiencies of Examples 1-8 all exceed 91%, and the capacity retention after 100 cycles is all above 93%, significantly better than Comparative Examples 1, 2, and 3. This indicates that the amorphous in-situ reaction layer formed on the sulfide surface through the mechanochemical "reaction consumption-in-situ construction" integrated strategy of the present invention possesses excellent oxidation resistance and lithium-ion conductivity, significantly improving interfacial compatibility with high-voltage cathodes. In contrast, the sulfide electrolyte of Comparative Example 1, due to its inert surface layer, shows significantly reduced oxidation decomposition initiation potential and electrical performance of the assembled all-solid-state battery. The oxygen-doped sulfide electrolyte of Comparative Example 2, obtained through conventional methods, has an oxidation decomposition initiation potential of only 2.6V, and the 0.2C initial discharge specific capacity, 1C / 0.2C rate efficiency, and 100-cycle capacity retention of the assembled all-solid-state battery are also far lower than those of the all-solid-state battery assembled with the composite solid-state electrolyte prepared in the present invention. In contrast, the solid electrolyte material in Comparative Example 3, due to its high content of inert lithium salt (i.e., inert layer), maintained a high oxidation decomposition initiation potential and had good oxidation resistance, but its overall lithium-ion conductivity was somewhat lost. Therefore, the performance of the assembled all-solid-state battery was significantly reduced.

[0050] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A composite solid electrolyte material, characterized in that, The composite solid electrolyte material comprises a sulfide solid electrolyte core and an amorphous lithium-ion conductive shell coating the surface of the sulfide solid electrolyte core. The composite solid electrolyte material is generated by a mechanochemical reaction between the sulfide solid electrolyte and van der Waals crystals. The surface of the sulfide solid electrolyte has an inert layer, which is generated by the reaction of the sulfide solid electrolyte with air. The mechanochemical reaction consumes the inert layer while generating an amorphous lithium-ion conductive shell in situ on the surface of the sulfide solid electrolyte, thereby improving the oxidation resistance of the sulfide solid electrolyte.

2. The composite solid electrolyte material according to claim 1, characterized in that, The inert layer comprises one or more of lithium carbonate, lithium hydroxide, lithium phosphate, and lithium chloride, and the total content of the inert layer in the sulfide solid electrolyte is ≤5 wt%.

3. The composite solid electrolyte material according to claim 1, characterized in that, The van der Waals crystal is a type of zero-dimensional, one-dimensional, or two-dimensional material composed of atoms stacked together by van der Waals forces, with the general chemical formula M. a X b Y c Where M is selected from transition metal elements, X is selected from halogen elements, Y is selected from oxygen or nitrogen elements, and a, b, and c are integers, with a > 0, b > 0, and c ≥ 0.

4. The composite solid electrolyte material according to claim 3, characterized in that, The transition metal element is one or more of Mo, W, Ti, Ru, Ta, Zr, Nb, and Al; the halogen element is one or more of Cl, Br, and I.

5. The composite solid electrolyte material according to claim 4, characterized in that, The van der Waals crystal is one or more of titanium tetrachloride, ruthenium trichloride, tantalum pentachloride, zirconium tetrachloride, niobium pentachloride, aluminum trichloride, and niobium oxychloride.

6. The composite solid electrolyte material according to claim 1, characterized in that, The sulfide solid electrolyte is selected from one or more of the following: silver-germanium sulfide structure, LGPS structure, and (1-j)Li2S-(j)P2S5 binary glass / glass-ceramic system, wherein 1 > j > 0.

7. The composite solid electrolyte material according to any one of claims 1 to 6, characterized in that, The thickness of the amorphous lithium-ion conductive shell is 1 nm to 200 nm; and / or the particle size of the composite solid electrolyte material is 0.1 μm to 30 μm.

8. A method for preparing a composite solid electrolyte material as described in any one of claims 1 to 7, characterized in that, Includes the following steps: The sulfide solid electrolyte and van der Waals crystal are mechanically ball-milled to cause a mechanochemical reaction between the van der Waals crystal and the inert layer on the surface of the sulfide solid electrolyte. While consuming the inert layer, an amorphous lithium-ion conductive shell is generated in situ on the surface of the sulfide solid electrolyte.

9. The preparation method according to claim 8, characterized in that, The amount of van der Waals crystals used accounts for 0.05% to 5% of the mass of the sulfide solid electrolyte. The rotation speed of the mechanical ball mill is 100 rpm to 1000 rpm, and the ball milling time is 0.5 h to 20 h. The ball milling media are zirconia balls or agate balls, and the ball-to-material ratio is 5 to 50:

1.

10. The application of a composite solid electrolyte material as described in any one of claims 1 to 7 or a composite solid electrolyte material prepared by the preparation method described in claim 8 or 9, characterized in that, The composite solid electrolyte material is used to manufacture solid-state batteries; the solid-state battery includes a positive electrode, a negative electrode, and an electrolyte membrane; the preparation steps of the positive electrode include: mixing the composite solid electrolyte material with a positive active material, a conductive agent, and a binder, preparing a positive electrode mixture through a dry or wet process, then compositing it with aluminum foil, and obtaining the positive electrode sheet through rolling and cutting.

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