Sulfide solid electrolyte and preparation method thereof, battery and application

Abstract

The application relates to the field of electrochemistry, and provides a sulfide solid electrolyte, a preparation method thereof, a battery and an application. The chemical formula of the sulfide solid electrolyte is Li 7‑a PS 6‑a X a , X is at least one selected from Cl, Br and I, 1<=a<=2; the sulfide solid electrolyte powder is composed of large particles and small particles, and the small particles exist on the large particles; characterized in that the particle size of the large particles is 3-20 mu m, the particle size of the small particles is 0.2-0.8 mu m; the number of the large particles accounts for 5-10% of the total particle number, and the number of the small particles accounts for 90-95% of the total particle number. The preparation method optimizes the powder structure and particle size distribution of the sulfide solid electrolyte, improves the ionic conductivity of the sulfide solid electrolyte, improves the solvent residue problem, simplifies the preparation process of the sulfide solid electrolyte, and simultaneously reduces the production cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemistry, in particular to a sulfide solid-state electrolyte, a preparation method thereof, a battery comprising the sulfide solid-state electrolyte and an application of the battery. BACKGROUND

[0002] As a key material for the next generation of high-performance battery systems, the performance of solid-state electrolyte directly affects the energy density, safety and service life of the battery. Due to its excellent ionic conductivity and electrochemical stability, sulfide solid-state electrolyte has become a research hotspot in recent years, especially in the application of all-solid-state lithium batteries.

[0003] The traditional preparation methods of sulfide solid-state electrolyte (LPSC) mainly include wet and dry processes. However, these processes have significant defects in improving the performance of sulfide solid-state electrolyte, for example, the wet process usually uses alcohol solvents for the dissolution and mixing of precursors, and uses the polarity and proticity of the solvents to improve the reaction uniformity. However, these solvents will react with Li2S, P2S5 and other precursors to produce Li3PO4 and other impurities. The dry process directly reacts the precursors by high-temperature calcination, avoiding the use of solvents in the wet process, thereby reducing the generation of oxygen and carbon impurities. However, this method requires high temperature control accuracy and uniform mixing conditions, otherwise it is easy to cause problems such as too large and uneven product particle size. SUMMARY

[0004] The purpose of the present application is to provide a sulfide solid-state electrolyte, a preparation method thereof, a battery and an application, to reduce the impurity content in the sulfide solid-state electrolyte, while improving the uniformity and ionic conductivity of the sulfide solid-state electrolyte, and to maintain the ionic conductivity at a high level while reducing the particle size. The specific technical solutions are as follows:

[0005] The first aspect of the present application provides a sulfide solid-state electrolyte, whose chemical formula is Li 7-a PS 6-a X a X is selected from at least one of Cl, Br and I, and 1≤a≤2; the sulfide solid-state electrolyte powder is composed of large particles and small particles, and the small particles exist on the large particles; characterized in that the particle size of the large particles is 3 μm~20 μm, and the particle size of the small particles is 0.2 μm~0.8 μm; the number of large particles accounts for 5%~10% of the total number of particles, and the number of small particles accounts for 90%~95% of the total number of particles.

[0006] In an embodiment of the present application, the carbon content of the sulfide solid-state electrolyte is ≤0.5wt%.

[0007] In an embodiment of the present application, the particle size of the sulfide solid-state electrolyte satisfies: 0.4 µm < D < 50 µm v 50 < 0.7 µm, 6 µm < D MAX < 8 µm.

[0008] In an embodiment of the present application, the ionic conductivity of the sulfide solid-state electrolyte is > 5.5 mS / cm.

[0009] In some embodiments of the present application, the sulfide solid-state electrolyte further comprises at least one of O, Se, F, Mg, Ca, Sr, Zn, Sc, Sb, Si, Ge, Sn, B, Al, Ga, In, Ti, Zr, V, Nb, Cu, Ni, Mn, Cr, Ag, La, Ce, Tb, Te, Pb, As, Bi, Fe, Mo and Co elements, which are introduced by doping or coating.

[0010] In some embodiments of the present application, the sulfide solid-state electrolyte is doped with an oxide selected from at least one of MgO, CaO, V2O5, MnO, Fe2O3, CoO, NiO, CuO, ZnO, ZrO2, MoO3, Ag2O, SrO, TiO2, Cr2O3, CeO2 and PbO.

[0011] A second aspect of the present application provides a preparation method of a sulfide solid-state electrolyte, comprising: mixing a precursor with a solvent under an inert atmosphere, mechanically stirring to obtain a suspension; characterized in that the precursor comprises Li2S, P2S5 and a halogen element-containing compound; the halogen element-containing compound comprises NH4X' and LiX'', X' and X'' are each independently selected from at least one of Cl, Br and I; the molar ratio of NH4X' and LiX'' is 1:(0-1); the mass ratio of the precursor to the solvent is 1:(2-4); the solvent is selected from at least one of n-hexane, benzene, toluene, cyclohexane, n-pentane, acetonitrile, cyclopentane and dimethyl carbonate; the suspension is left to stand under normal temperature and pressure and an inert atmosphere, so that the solvent volatilizes to obtain a solid-state electrolyte precursor mixture; the solid-state electrolyte precursor mixture is subjected to heat treatment under an inert atmosphere to obtain a sulfide solid-state electrolyte; wherein the heat treatment comprises a first heat treatment and a second heat treatment, the temperature rising rate of the first heat treatment is 1-2 ℃ / min, the temperature of the first heat treatment is 60-80 ℃, and the time of the first heat treatment is 1-3 h; the temperature rising rate of the second heat treatment is 7-10 ℃ / min, the temperature of the second heat treatment is 450-600 ℃, and the time of the second heat treatment is 4-10 h; wherein the chemical formula of the sulfide solid-state electrolyte is Li 7- a PS 6-a X aX is selected from at least one of Cl, Br and I, and 1≤a≤2.

[0012] In an embodiment of the present application, the inert atmosphere is selected from at least one of nitrogen, argon.

[0013] In an embodiment of the present application, the mechanical stirring is carried out at normal temperature and pressure, the time of the mechanical stirring is 12-24 h, and the rate of the mechanical stirring is 300-600 rpm.

[0014] In an embodiment of the present application, the rate of solvent evaporation is 1.5-7.0 mg / cm 2 h, and the residual rate after solvent evaporation is less than 5wt% based on the mass of the solvent.

[0015] The third aspect of the present application provides a battery comprising a positive electrode sheet, a negative electrode sheet and the sulfide solid electrolyte provided by the first aspect of the present application or the sulfide solid electrolyte prepared by the preparation method provided by the second aspect of the present application.

[0016] The fourth aspect of the present application provides the application of the battery provided by the third aspect of the present application in an aircraft, characterized in that the aircraft is selected from a low-empty manned electric vertical take-off and landing aircraft.

[0017] The beneficial effects of the present application are as follows:

[0018] The present application provides a sulfide solid electrolyte, a preparation method thereof, a battery and an application, the chemical formula of the solid electrolyte is Li 7-a PS 6-a X a X is selected from at least one of Cl, Br and I, and 1≤a≤2; the sulfide solid electrolyte powder is composed of large particles and small particles, and the small particles exist on the large particles; characterized in that the particle size of the large particles is 3-20 μm, and the particle size of the small particles is 0.2-0.8 μm; the number of the large particles accounts for 5-10% of the total number of particles, and the number of the small particles accounts for 90-95% of the total number of particles. The sulfide solid electrolyte powder of the present application is composed of large particles and small particles, and the small particles exist uniformly on the large particles, the particle size and the number of the large particles and the small particles in the sulfide solid electrolyte powder are within the range of the present application, which can make the sulfide solid electrolyte have higher ionic conductivity. Further, the preparation method of the present application avoids the introduction of impurities in the reaction process by selecting a solvent that does not dissolve the precursor; optimizes the powder structure and particle size distribution of the sulfide solid electrolyte by using ammonium halide to replace or partially replace lithium halide; improves the ionic conductivity of the sulfide solid electrolyte, solves the problem of solvent residue, simplifies the preparation process of the sulfide solid electrolyte, and reduces the production cost.

[0019] Of course, practicing any of the products or methods of the present application does not necessarily require achieving all of the above-mentioned advantages simultaneously. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. Obviously, the drawings described in the following are only some of the embodiments of the present application, and other embodiments can also be obtained by those skilled in the art based on these drawings.

[0021] Figure 1 SEM morphology of the sulfide solid electrolyte prepared for Example 1-4 is enlarged 500 times;

[0022] Figure 2 SEM morphology of the sulfide solid electrolyte prepared for Example 1-4 is enlarged 10000 times;

[0023] Figure 3 EDS analysis results of the sulfide solid electrolyte prepared for Example 1-4;

[0024] Figure 4 SEM morphology of the sulfide solid electrolyte prepared for Comparative Example 1-1 is enlarged 500 times;

[0025] Figure 5 SEM morphology of the sulfide solid electrolyte prepared for Comparative Example 1-1 is enlarged 10000 times;

[0026] Figure 6 SEM morphology of the sulfide solid electrolyte prepared for Comparative Example 3-7 is enlarged 500 times;

[0027] Figure 7 SEM morphology of the sulfide solid electrolyte prepared for Comparative Example 3-7 is enlarged 10000 times;

[0028] Figure 8 SEM morphology 1 of the sulfide solid electrolyte prepared for Comparative Example 3-5 is enlarged 10000 times;

[0029] Figure 9 SEM morphology 2 of the sulfide solid electrolyte prepared for Comparative Example 3-5 is enlarged 10000 times. DETAILED DESCRIPTION

[0030] The technical solutions in the present application will be described clearly and completely in the following with the embodiments of the present application and the drawings. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. All other embodiments obtained by those skilled in the art based on the present application are within the scope of protection of the present application.

[0031] A first aspect of the present application provides a sulfide solid electrolyte, whose chemical formula is Li 7-a PS 6-a X a X is selected from at least one of Cl, Br and I, and 1≤a≤2; for example, the chemical formula of the sulfide solid electrolyte is selected from at least one of Li6PS5X, Li 5.75 PS 4.75 X 1.25 Li 5.5 PS 4.5 X 1.5 Li 5.25 PS 4.25 X 1.75 and Li5PS4X2. The sulfide solid electrolyte powder is composed of large particles and small particles, and the small particles exist on the large particles; characterized in that the particle size of the large particles is 3 μm to 20 μm, and the particle size of the small particles is 0.2 μm to 0.8 μm; the number of the large particles accounts for 5% to 10% of the total number of particles, and the number of the small particles accounts for 90% to 95% of the total number of particles. For example, the particle size of the large particles can be 3 μm, 5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, or a range formed by any two of the above values; the particle size of the small particles can be 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, or a range formed by any two of the above values; the number of the large particles accounts for 5%, 6%, 7%, 8%, 9%, 10% or a range formed by any two of the above values of the total number of particles; and the number of the small particles accounts for 90%, 91%, 92%, 93%, 94%, 95% or a range formed by any two of the above values of the total number of particles. The inventors have found that when the sulfide solid electrolyte powder is composed of large particles and small particles, and the small particles exist uniformly on the large particles, the contact between the large particles and the small particles is closer, ion transmission is easier, and the ionic conductivity of the sulfide solid electrolyte is higher, compared with the structure in which the large particles and the small particles exist separately. When the particle size of the large particles of the sulfide solid electrolyte is too large, it is not conducive to the processing and use of the sulfide solid electrolyte in the later stage; when the particle size of the small particles of the sulfide solid electrolyte is too small, it will cause the conductivity to decrease; and when the particle size and the number of the large particles and the small particles are within the range of the present application, it indicates that the reaction of the precursor and the solvent is relatively sufficient, and the uniformity of the sulfide solid electrolyte is relatively good.

[0032] Figure 1 The SEM morphology of the sulfide solid electrolyte prepared in Examples 1-4 is enlarged 500 times. From Figure 1 It can be seen that the powder morphology of the sulfide solid electrolyte is a coral-like structure. Figure 2The SEM morphology of the sulfide solid electrolyte prepared in Example 1-4 was amplified 10,000 times. It can be seen from the SEM image that the sulfide solid electrolyte is a coral-like structure with small particles distributed on large particles. Figure 2 It can be seen that the sulfide solid electrolyte is a coral-like structure with small particles distributed on large particles. The particle size distribution of the SEM image was counted using Image J software, and the counting results showed that the particle size of the large particles in the sulfide solid electrolyte prepared in Example 1-4 was 3-8 μm, and the large particles accounted for 9% of the total number of particles; the particle size of the small particles was 0.2-0.8 μm, and the small particles accounted for 91% of the total number of particles. Figure 3 The EDS analysis results of the sulfide solid electrolyte prepared in Example 1-4 showed that the elements in the sulfide solid electrolyte were uniformly distributed, and the large particles and the small particles were a kind of substance, and the uniformity of the sulfide solid electrolyte was better.

[0033] In an embodiment of the present application, the carbon content of the sulfide solid electrolyte is ≤0.5 wt%. During use, the excess distribution of carbon can form a continuous electron conduction path, causing an electronic short circuit inside the secondary battery, thereby destroying the ion conduction mechanism of the secondary battery; at the same time, reducing the carbon content in the sulfide solid electrolyte is beneficial to the transmission of lithium ions in the secondary battery, thereby improving the cycle performance and energy efficiency of the secondary battery. Controlling the carbon content of the sulfide solid electrolyte within the range of the present application is beneficial to improving the purity of the sulfide solid electrolyte, and thus improving the ionic conductivity of the sulfide solid electrolyte.

[0034] In an embodiment of the present application, the particle size of the sulfide solid electrolyte satisfies: 0.4 µm < D v 50 < 0.7 µm, 6 µm < D MAX < 8 µm. Wherein, D MAX refers to the maximum particle size of the sulfide solid electrolyte. Controlling the particle size D v 50 and D MAX within the range of the present application, the sulfide solid electrolyte has a high bulk density, good uniformity and processing performance.

[0035] In an embodiment of the present application, the ionic conductivity of the sulfide solid electrolyte is >5.5 mS / cm (referring to the ionic conductivity measured under the condition of 350 MPa pressure molding at room temperature). The inventors found in the research that the sulfide solid electrolyte of the present application has high ionic conductivity, and can improve the safety performance, energy density and low temperature performance of the secondary battery when applied to the secondary battery.

[0036] In some embodiments of this application, the sulfide solid electrolyte further includes at least one of the elements selected from O, Se, F, Mg, Ca, Sr, Zn, Sc, Sb, Si, Ge, Sn, B, Al, Ga, In, Ti, Zr, V, Nb, Cu, Ni, Mn, Cr, Ag, La, Ce, Tb, Te, Pb, As, Bi, Fe, Mo, and Co, which are introduced by doping or coating.

[0037] In this application, the doping methods include, but are not limited to, introducing doping elements during the substrate and solvent mixing stage or introducing doping elements with sintering aids during the sintering stage; the coating methods include, but are not limited to, forming a coating layer containing doping elements on the surface of the sulfide solid electrolyte by ball milling, vapor deposition or atomic spraying.

[0038] In some embodiments of this application, the sulfide solid electrolyte is doped with an oxide, which is selected from at least one of MgO, CaO, V₂O₅, MnO, Fe₂O₃, CoO, NiO, CuO, ZnO, ZrO₂, MoO₃, Ag₂O, SrO, TiO₂, Cr₂O₃, CeO₂, and PbO. The oxide-doped sulfide solid electrolyte is prepared using the above doping method, wherein the mass ratio of substrate to oxide can be 99.99:0.01 to 95:5. The oxide-doped sulfide solid electrolyte can further improve the ionic conductivity, air stability, and interfacial stability of the sulfide solid electrolyte.

[0039] The second aspect of this application provides a method for preparing a sulfide solid electrolyte, comprising: mixing a precursor with a solvent under an inert atmosphere and mechanically stirring to obtain a suspension; characterized in that the precursor comprises Li₂S, P₂S₅, and a halogen-containing compound; the halogen-containing compound comprises NH₄X′ and LiX″, wherein X′ and X″ are each independently selected from at least one of Cl, Br, and I; exemplaryly, when NH₄X′ is NH₄Br, LiX″ can be LiCl; the molar ratio of NH₄X′ to LiX″ is 1:(0~1); the mass ratio of the precursor to the solvent is 1:(2~4); the solvent is selected from n-hexane, benzene, toluene, cyclohexane, n-pentane, acetonitrile, cyclopentane, and dimethyl carbonate. At least one of the following: A suspension is allowed to stand at room temperature and pressure under an inert atmosphere to allow the solvent to evaporate, yielding a solid electrolyte precursor mixture; the solid electrolyte precursor mixture is then heat-treated under an inert atmosphere to obtain a sulfide solid electrolyte; wherein the heat treatment includes a first heat treatment and a second heat treatment, wherein the heating rate of the first heat treatment is 1~2℃ / min, the temperature of the first heat treatment is 60~80℃, and the time of the first heat treatment is 1~3h; the heating rate of the second heat treatment is 7~10℃ / min, the temperature of the second heat treatment is 450~600℃, and the time of the second heat treatment is 4~10h; wherein the chemical formula of the sulfide solid electrolyte is Li 7-a PS 6-a X aX is selected from at least one of Cl, Br, and I, where 1 ≤ a ≤ 2. For example, the molar ratio of NH4X′ and LiX″ can be 1:0, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or any range of two of these values; the mass ratio of precursor to solvent can be 1:2, 1:2.5, 1:3, 1:3.5, 1:4, or any range of two of these values; the heating rate of the first heat treatment can be 1℃ / min, 1.2℃ / min, 1.4℃ / min, 1.6℃ / min, 1.8℃ / min, 2℃ / min, or any range of two of these values; the temperature of the first heat treatment can be 60℃, 65℃, 70℃, 75℃, 80℃, or any range of two of these values. The range of values ​​is as follows: the time for the first heat treatment can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, or any two of these values; the heating rate for the second heat treatment can be 7 °C / min, 7.3 °C / min, 7.7 °C / min, 8 °C / min, 8.3 °C / min, 8.7 °C / min, 9 °C / min, 9.3 °C / min, 9.7 °C / min, 10 °C / min, or any two of these values; the temperature for the second heat treatment can be 450 °C, 480 °C, 500 °C, 520 °C, 550 °C, 580 °C, 600 °C, or any two of these values; the time for the second heat treatment can be 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, 10 h, or any two of these values.

[0040] The inventors discovered that the above preparation method facilitates the formation of sulfide solid electrolyte powder with small particles uniformly distributed on the surface of large particles. Furthermore, it allows the large and small particles to meet the following specifications: the particle size of the large particles is 3μm~20μm, and the particle size of the small particles is 0.2μm~0.8μm; the number of large particles accounts for 5%~10% of the total number of particles, and the number of small particles accounts for 90%~95% of the total number of particles. The main reasons for this are as follows:

[0041] (1) In halogen-containing compounds, ammonium halide is used to partially or completely replace lithium halide. Ammonium halide decomposes during high-temperature sintering, producing ammonia and hydrogen halide. Hydrogen halide reacts with lithium sulfide, thereby doping halogens into the sulfide solid electrolyte. In the early stage of sintering, ammonium halide decomposes rapidly, and the concentration of hydrogen halide gas in the system is high. Therefore, the electrolyte formation rate is fast, and rapid agglomeration easily produces large-diameter particles. As the reaction proceeds, the gas concentration decreases, and the formation rate of sulfide solid electrolyte decreases significantly. Since the large-diameter particles that have already been formed can serve as new sites for crystal formation, the particles generated later tend to grow on the large particles. Furthermore, due to the decrease in the concentration of reactive gas, the reaction rate is slow, and most of the particles generated at this time are small-diameter particles.

[0042] (2) To facilitate the formation of a morphology where small particles coat large particles in conjunction with the aforementioned ammonium halide, this application uses an inert solvent and controls the mass ratio of precursor to inert solvent to achieve better dispersion of the raw materials. Because ammonium halide is highly reactive, ball milling or pulverization easily causes it to decompose, making it unsuitable for early particle size control. Therefore, the particle size of the ammonium halide raw material is maintained at approximately 100 μm at the time of manufacture. This application uses an inert solvent and controls the mass ratio of precursor to inert solvent to be (1:2~1:4), thereby achieving better and more uniform dispersion of ammonium halide and other precursor raw materials. This prevents a situation where a large amount of ammonium halide decomposes simultaneously in one area while there is virtually no effect from ammonium halide on the other side during sintering. The purpose of using an inert solvent is to prevent lithium sulfide and phosphorus pentasulfide in the raw materials from coupling with the polar solvent or undergoing other reactions. The coupling products have poor reactivity with hydrogen halide gas, resulting in the inability to form an ideal morphology. Simultaneously, the polar solvent releases a large amount of heat when reacting with the raw materials, causing the ammonium halide to decompose prematurely.

[0043] (3) In addition, the heating rate of the two sintering stages will also directly affect the formation of the morphology of the sulfide solid electrolyte. The purpose of the first heat treatment is to remove the residual solvent in the system and to prevent the introduction of a large number of cavities in the product due to rapid solvent evaporation. Therefore, the heating rate needs to be maintained at 1-2℃ / min. Too high a heating rate will cause the solvent to evaporate too quickly and introduce cavities, and it is easy to cause partial decomposition of ammonium halide; too low a heating rate will lead to too long heating time, increasing working hours and energy consumption. The purpose of the second heat treatment is to form the morphology of silver-germanium sulfide crystals and small particles uniformly existing in large particles, thereby obtaining a sulfide product with high ionic conductivity. Therefore, the heating rate needs to be maintained at 7-10℃ / min. Excessive heating rate can damage heating equipment and cause overheating, resulting in uneven heating. Insufficient heating rate will cause a large amount of ammonium halide to decompose and produce gas before the raw materials have started to react and form the target crystal form. This gas cannot act on the final product, and it is impossible to act on the product while forming the silver-germanium sulfide crystal form. As a result, it is impossible to form a product with a suitable particle size and to form a structure in which small particles of sulfide solid electrolyte are uniformly present on large particles.

[0044] The halogen-containing compounds in this application include NH4X′ and LiX″. The molar ratio of NH4X′ and LiX″ is controlled within the range specified in this application. During the heat treatment of the precursor, NH3 and H2S gases are generated. These gases not only serve as a protective atmosphere during calcination but also regulate the growth of the sulfide solid electrolyte, resulting in a structure where small particles are uniformly distributed on larger particles. This also leads to a more uniform particle size distribution between the large and small particles, resulting in a narrower particle size distribution in the final product. This is beneficial for improving the ionic conductivity of the sulfide solid electrolyte, thereby enhancing the electrochemical performance of the battery. Furthermore, this application uses an inert solvent that does not chemically react with the precursor to prepare the sulfide solid electrolyte. The mass ratio of precursor to solvent is controlled within the range specified in this application. Physical mixing is performed during the mixing stage, and no chemical reaction occurs during stirring, avoiding side reactions and reducing the introduction of impurities such as carbon and oxygen. This, in turn, improves the purity and ionic conductivity of the sulfide solid electrolyte. Furthermore, this application employs a two-stage heat treatment process. During heat treatment, the reaction rate is controlled by gradually increasing the temperature, ensuring uniform reaction between precursors and reducing the formation of byproducts. The first heat treatment uses a lower temperature, which reduces the decomposition of NH4X′ in the early stages, allowing NH4X′ to react only during the second heat treatment. This facilitates the generation of NH3 and H2S gases to regulate the growth of the sulfide solid electrolyte, resulting in a more uniform particle size distribution. Controlling the duration of the first heat treatment within the timeframe of this application ensures complete solvent evaporation while minimizing the reaction and decomposition of NH4X′. Similarly, controlling the duration of the second heat treatment within the timeframe ensures complete precursor reaction, allowing halogen atoms to be largely incorporated into the sulfide solid electrolyte cell, and reducing carbonization caused by solvent residue. This, in turn, improves the ionic conductivity and overall performance of the sulfide solid electrolyte.

[0045] Figure 4 The image shows the SEM morphology of the sulfide solid electrolyte prepared in Comparative Example 1-1, magnified 500 times. Figure 4 It can be seen that when LiCl is selected as the halogen-containing compound, that is, when halogen-containing compounds without NH4X′, Li2S, and P2S5 are used as precursors to prepare sulfide solid electrolytes, a structure in which small particles are uniformly present on large particles is not formed. Figure 5 The image shows the SEM morphology of the sulfide solid electrolyte prepared in Comparative Example 1-1, magnified 10000 times. Figure 5It can be seen that when the halogen-containing compound does not contain NH4X′, the small particles in the sulfide solid electrolyte are finely fragmented and distributed around the large particles. Using ImageJ software to analyze the particle size distribution of the SEM images, the results show that in the sulfide solid electrolyte prepared in Comparative Example 1-1, the large particles have a diameter of 6-20 μm, accounting for 21% of the total particles; the small particles have a diameter of 0.1-1 μm, accounting for 79% of the total particles. This differs from the structure in Examples 1-4 where small particles are uniformly distributed on the surface of large particles, indicating that the morphology of small particles enveloping and distributing on the surface of large particles is related to the presence of NH4X′ in the halogen-containing compound.

[0046] In one embodiment of this application, based on the molecular formula Li of the target product sulfide solid electrolyte... 7-a PS 6- a X a Adjusting the molar ratio of the precursors, for example, when the molar ratio of Li₂S, P₂S₅, and NH₄X′ is 6:1:2, the synthesized sulfide solid electrolyte is Li₆PS₅X; when the molar ratio of Li₂S, P₂S₅, and NH₄X′ is 5.75:1:2.5, the synthesized sulfide solid electrolyte is Li₆PS₅X. 5.75 PS 4.75 X 1.25 When the molar ratio of Li₂S, P₂S₅, and NH₄X′ is 5.5:1:3, the synthesized sulfide solid electrolyte is Li 5.5 PS 4.5 X 1.5 When the molar ratio of Li₂S, P₂S₅, and NH₄X′ is 5.25:1:3.5, the synthesized sulfide solid electrolyte is Li 5.25 PS 4.25 X 1.75 When the molar ratio of Li2S, P2S5, and NH4X′ is 5:1:4, the synthesized sulfide solid electrolyte is Li5PS4X2; when the molar ratio of Li2S, P2S5, NH4X′, and LiX″ is 5.75:1:1.5:0.5, the synthesized sulfide solid electrolyte is Li6PS5X; when the molar ratio of Li2S, P2S5, NH4X′, and LiX″ is 5.5:1:1:1, the synthesized sulfide solid electrolyte is Li6PS5X.

[0047] Figure 6 The SEM morphology of the sulfide solid electrolytes prepared in Comparative Examples 3-7 is magnified 500 times. Figure 7 The image shows the SEM morphology of the sulfide solid electrolytes prepared in Comparative Examples 3-7, magnified 10000 times. Figure 7It can be seen that when the second heat treatment time was shortened to 3 hours, some large particles began to appear on the surface of the large particles, but there were still large particles that were not covered by small particles. Using a laser particle size analyzer to statistically analyze the particle size distribution of the samples, the results showed that in the sulfide solid electrolytes prepared in Comparative Examples 3-7, the particle size of large particles was 3-12 μm, accounting for 15% of the total number of particles; the particle size of small particles was 0.1-1 μm, accounting for 85% of the total number of particles. This indicates that the formation time of large and small particles differs during the preparation of the sulfide solid electrolyte. Large particles mainly occur in the early stage of the second heat treatment, accompanied by the rapid decomposition of NH4X′. In the later stage of the second heat treatment, as the content of the remaining NH4X′ decreases, the precursor reaction rate decreases, and small particles begin to form on the surface of the large particles, resulting in a structure where small particles are uniformly present within the large particles.

[0048] As shown in Tables 1 and 2, the proportion of small particles in Examples 1-1, Comparative Examples 3-7, and Comparative Example 1-1 gradually decreases, while the proportion of large particles gradually increases, indicating that Example 1-1 contains more small particles with a smaller average particle size. Simultaneously, it can be seen from Examples 1-1, Comparative Examples 3-7, and Comparative Example 1-1 that the ionic conductivity gradually increases with the increase in the proportion of small particles. This is significantly different from the usual pattern where decreasing particle size of sulfide electrolytes leads to increased interfaces, increased ion transfer impedance, and consequently, a decrease in ionic conductivity. The reason for this result is that in the product synthesized in this application (Example 1-1), the small particles are distributed on the surface of the large particles, maintaining close contact. This means the large particles can act as bridges for ion transfer between the small particles, reducing the interfacial impedance between them. Therefore, while the overall particle size decreases, a product with higher ionic conductivity is obtained.

[0049] In one embodiment of this application, the inert atmosphere is selected from at least one of nitrogen and argon. By using an inert atmosphere, the occurrence of side reactions during the reaction process can be reduced, and the purity and particle size uniformity of the sulfide solid electrolyte can be improved.

[0050] In one embodiment of this application, mechanical stirring is carried out at room temperature and pressure for a duration of 12-24 hours. For example, the stirring time can be 12 hours, 15 hours, 18 hours, 21 hours, 24 hours, or any combination of two of these values. The stirring speed is 300-600 rpm. For example, the stirring speed can be 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, or any combination of two of these values. By controlling the mixing method of the precursor and solvent, and the temperature, pressure, and stirring speed within the above ranges, reactions between the substrates during stirring can be avoided, ensuring that a sufficient and uniform solid-phase reaction occurs only during the sintering stage. This is beneficial for the preparation of sulfide solid electrolytes and improves the ionic conductivity of the sulfide solid electrolyte. When other mixing methods are used (such as ultrasonic dispersion), mechanical stirring under high temperature and pressure, or excessively high rotation speeds (e.g., greater than 600 rpm), reactions may occur between the substrates, leading to uneven reaction in the subsequent preparation of sulfide solid electrolytes, which in turn affects the particle size and ionic conductivity of the sulfide solid electrolytes. In this application, the mechanical stirring time is limited to the above-mentioned range, which ensures uniform mixing and more thorough contact of the components, thereby achieving higher ionic conductivity.

[0051] In one embodiment of this application, the solvent evaporation rate is 1.5~7.0 mg / cm³. 2 • h, based on the mass of the solvent, the residual amount of solvent after evaporation is less than 5 wt%. For example, the solvent evaporation rate can be 1.5 mg / cm³. 2 ·h, 2 mg / cm 2 ·h, 3 mg / cm 2 ·h, 4 mg / cm 2 ·h, 5 mg / cm 2 ·h、6 mg / cm 2 ·h, 7 mg / cm 2 •h can be a range consisting of any two of these values. Studies have shown that limiting the solvent evaporation rate within the above range reduces the formation of cavities in the mixture due to the simultaneous evaporation of large amounts of solvent, thereby further improving the ionic conductivity and overall performance of the electrolyte. Furthermore, a lower solvent residue reduces the amount of carbon impurities introduced during calcination, resulting in a higher purity of the sulfide solid electrolyte, further enhancing its ionic conductivity.

[0052] In one embodiment of this application, the suspension is allowed to stand at room temperature and pressure under an inert atmosphere for 12 to 24 hours. For example, the standing time can be 12 hours, 15 hours, 18 hours, 21 hours, 24 hours, or any combination of two of these values. Controlling the standing time within the above range is beneficial for controlling the residual rate after solvent evaporation.

[0053] Because NH4X′ is easily decomposed and highly reactive, the suspension in this application needs to be allowed to stand at room temperature and pressure under an inert atmosphere to allow the solvent to evaporate, and the temperature and time during the first heat treatment process must be controlled. In Comparative Examples 3-5, the step of allowing the suspension to stand for 12-24 hours was changed to vacuum drying at 60°C for 6 hours. In this case, the solvent evaporation rate was 20 mg / cm³. 2 The evaporation rate is significantly higher than that of volatilization rate when left to stand at room temperature and pressure. Figure 8 The SEM morphology of the sulfide solid electrolytes prepared in Comparative Examples 3-5 is shown at 500x magnification. Figure 9 The image shows the SEM morphology of the sulfide solid electrolytes prepared in Comparative Examples 3-5, magnified 10000 times. Figure 8 and Figure 9 As can be seen, in the sulfide solid electrolyte prepared in Comparative Example 3-5, the solvent evaporation rate was too fast, resulting in the formation of cavity structures in some areas. At the same time, the vacuum drying caused some NH4X′ to react incompletely, decomposing to produce ammonia and hydrogen halide gases, which were then removed by the vacuum conditions. This was not conducive to the conduction of ions in the sulfide solid electrolyte, resulting in the ionic conductivity of the sulfide solid electrolyte prepared in Comparative Example 3-5 decreasing to 2.28 mS / cm.

[0054] In this application, the solvent evaporation rate is controlled to maintain the thickness of the solid electrolyte precursor mixture at 1-5 mm and the dry specific surface area of ​​the solid electrolyte precursor mixture at 1.5-3 cm². 2 / g. In this application, the material is a thin planar layer (e.g., granular or flake-like material spread in a beaker), and the drying specific surface area = drying area / mass of the precursor mixture; the drying area = the surface area of ​​the material in direct contact with the drying medium (inert atmosphere). By controlling the thickness and drying specific surface area, the drying rate of the material can be adjusted, thereby affecting the solvent residue and achieving the adjustment of carbon content. This application does not particularly limit the method for controlling the solvent evaporation rate, as long as it achieves the purpose of this application.

[0055] A third aspect of this application provides a battery comprising a positive electrode, a negative electrode, and a sulfide solid electrolyte provided in the first aspect of this application, or a sulfide solid electrolyte prepared by the preparation method provided in the second aspect of this application. Applying the sulfide solid electrolyte of this application or the sulfide solid electrolyte prepared by the preparation method of this application to a battery significantly improves the battery's safety, energy density, and low-temperature performance.

[0056] This application does not impose any special limitations on the positive and negative electrode plates in the battery, as long as they can achieve the purpose of this application.

[0057] The fourth aspect of this application provides the application of the battery provided in the third aspect of this application in an aircraft, characterized in that the aircraft is selected from low-altitude manned electric vertical take-off and landing aircraft, which can improve the flight endurance, safety performance and extreme environment resistance of the spacecraft, while the long-life battery can reduce the maintenance frequency and cost of the aircraft.

[0058] Example

[0059] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Unless otherwise specified, "parts" and "%" refer to mass. "Room temperature" is 25±5℃, and "atmospheric pressure" is 101kPa.

[0060] Test methods and apparatuses:

[0061] Measurement of ionic conductivity

[0062] In an argon-filled glove box, 100 mg of solid electrolyte powder was weighed and placed in a mold battery with stainless steel sheets at both ends, each with a diameter of 9 mm. The mold battery was then pressurized at 200 MPa and 350 MPa to form two sets of electrolyte sheets. The thickness of the electrolyte sheets was measured to be 1 mm using a thickness gauge. AC impedance spectroscopy was performed using the mold battery. The bulk impedance of the electrolyte was determined using electrochemical impedance spectroscopy (EIS) on an electrochemical workstation (ChenHua, CHI630E). A DC polarization voltage of 1 V was applied to measure the bulk impedance, with an amplitude of 50 mV and a frequency range of 1 Hz to 10 MHz. The ionic conductivity of the sulfide solid electrolyte was calculated based on the bulk impedance and ionic conductivity formulas, as follows:

[0063] Where σ is the ionic conductivity, in S / cm; L is the thickness of the electrolyte sheet, in cm; and R is the electrolyte bulk impedance, in S / cm. S represents the effective contact area between the stainless steel sheet and the electrolyte, in cm². 2 .

[0064] Carbon content testing

[0065] The test was conducted using a LECO CS744 high-frequency infrared carbon-sulfur analyzer. The instrument was calibrated using standard samples with known carbon content to ensure accuracy and repeatability. During the test, an appropriate amount of sulfide solid electrolyte was added to the instrument's crucible and thoroughly mixed with flux to promote complete combustion. High-frequency induction heating caused the sulfide solid electrolyte to burn rapidly. The generated gas entered the infrared detection system to detect the carbon dioxide concentration, thereby calculating the carbon content.

[0066] Morphology and particle size distribution testing

[0067] The surface morphology and particle size of the sulfide solid electrolyte were observed using a Zeiss Sigma 300 scanning electron microscope (SEM). The sample was fixed on the sample stage, which was placed in a vacuum chamber. The SEM parameters, including accelerating voltage, beam current, and working distance, were adjusted to optimize imaging. Surface morphology information was acquired using a secondary electron detector. The particle size of the sulfide solid electrolyte in the SEM images was measured using ImageJ software to obtain the main size range of the particles.

[0068] Particle size distribution was tested using a Bettersize 2600 laser particle size analyzer. Approximately 0.1 g of sample was weighed, and an appropriate amount of n-octane was added as a dispersion medium. The sample was ultrasonically dispersed for 3 minutes to promote uniform particle dispersion. The dispersed sample was then injected into the instrument's wet circulation chamber, the shading rate was adjusted to 20%, and the circulation system was activated to maintain uniform dispersion before testing began. Each sample was measured three times, and its D value was calculated. v 50. D MAX Representative particle size parameters were obtained, and the particle size distribution curve was recorded. Using the size range of large and small particles from the SEM, the particle size distribution curve was integrated in Origin software to obtain the proportion of each particle size.

[0069] Testing of solvent evaporation rate and solvent residue after evaporation

[0070] Under normal temperature and pressure and inert atmosphere, by using different evaporation containers (such as evaporating dishes and beakers), the thickness of the solid electrolyte precursor mixture was controlled at 1~5 mm, and the dry area per gram of solid electrolyte precursor mixture was controlled at 1.5~3 cm². 2 The solvent evaporation rate is controlled by adjusting the concentration of the precursor mixture. After evaporating the precursor mixture for x hours, the masses m0 and m1 of the mixture before and after evaporation are determined by weighing. The amount of solvent evaporated during that evaporation time is m0 minus m1. Dividing this by the evaporation time x and the dry specific surface area S yields the solvent evaporation rate v. If the mass of solvent added to the suspension during preparation is m2, then based on the mass of the solvent, the residual rate after solvent evaporation is... .

[0071] Example 1-1

[0072] In an argon atmosphere, Li₂S, P₂S₅, and NH₄Br in a molar ratio of 6:1:2 were weighed as precursors. The precursors were mixed with n-hexane, wherein 1 kg of precursor corresponds to 3 L of n-hexane (the mass ratio of precursor to solvent is 1:2). The mixture was stirred at 400 rpm for 12 h at room temperature and pressure to obtain a suspension.

[0073] The suspension was placed at room temperature and pressure for 12 hours in an argon atmosphere to allow the solvent to evaporate at a rate of 5 mg / cm³. 2 •h, so that the solvent residue is kept below 5wt%, and a solid electrolyte precursor mixture is obtained;

[0074] The solid electrolyte precursor mixture was transferred to a quartz tube, sealed with a sealing film, and placed in a nitrogen-filled tube furnace. After removing the sealing film, the tube was subjected to heat treatment in two steps: first, the temperature was increased to 60°C at a rate of 1.5°C / min and heated at 60°C for 2 hours; then, the temperature was increased to 550°C at a rate of 8°C / min and heated at 550°C for 5 hours to obtain solid electrolyte powder (Li6PS5Cl). The ionic conductivity of the prepared solid electrolyte at room temperature is shown in Table 1.

[0075] Examples 1-2 to Examples 1-9

[0076] Except for adjusting the type and molar ratio of the precursor according to Table 1, everything else is the same as in Example 1-1.

[0077] Examples 1-10 to Examples 1-11

[0078] Except for adjusting the mass ratio of precursor to solvent according to Table 1, the rest is the same as in Example 1-1.

[0079] Examples 2-1 to 2-6

[0080] Except for adjusting the type of solvent according to Table 2, everything else is the same as in Examples 1-1.

[0081] Examples 3-1 to 3-15

[0082] Except for adjusting the heating rate, temperature, and time of the first heat treatment and the heating rate, temperature, and time of the second heat treatment according to Table 3, the rest is the same as in Example 1-1.

[0083] Examples 4-1 to 4-6

[0084] Except for adjusting the stirring time and stirring rate according to Table 4, everything else is the same as in Example 1-1.

[0085] Example 5-1

[0086] Except for adjusting the raw material ratio to a molar ratio of Li2S, P2S5, NH4Br and SiO2 of 5.3:1:3:0.1, the rest is the same as in Example 1-1.

[0087] Example 5-2

[0088] Except for adjusting the raw material ratio to a molar ratio of Li2S, P2S5, NH4Br and ZrO2 of 5.3:1:3:0.1, the rest is the same as in Example 1-1.

[0089] Comparative Examples 1-1 to 1-2

[0090] Except for adjusting the type and molar ratio of the precursor according to Table 1, everything else is the same as in Example 1-1.

[0091] Comparative Examples 1-3 to 1-4

[0092] Except for adjusting the mass ratio of precursor to solvent according to Table 1, the rest is the same as in Example 1-1.

[0093] Comparative Example 2-1

[0094] Except for adjusting the type of solvent according to Table 2, everything else is the same as in Examples 1-1.

[0095] Comparative Examples 3-1 to 3-4

[0096] Except for adjusting the temperatures of the first and second heat treatments according to Table 3, the rest is the same as in Example 1-1.

[0097] Comparative Examples 3-5

[0098] Except for adjusting the stirring at 400 rpm for 12 hours at room temperature and pressure to vacuum drying at 60°C for 6 hours, the rest is the same as in Example 1-1.

[0099] Comparative Examples 3-6 to 3-7

[0100] Except for adjusting the time of the second heat treatment according to Table 3, the rest is the same as in Example 1-1.

[0101] Comparative Examples 3-8

[0102] Except for adjusting the heating rate of the first heat treatment according to Table 3, the rest is the same as in Example 1-1.

[0103] Comparative Examples 3-9

[0104] Except for adjusting the heating rate of the second heat treatment according to Table 3, the rest is the same as in Example 1-1.

[0105] The preparation and performance parameters of each embodiment and comparative example are shown in Tables 1 to 5.

[0106] Table 1

[0107]

[0108] Table 2

[0109]

[0110] Table 3

[0111]

[0112] Table 4

[0113]

[0114] Table 5

[0115]

[0116] As can be seen from Table 1, when the sulfide solid electrolyte powder is composed of large and small particles, with the small particles uniformly distributed on the large particles, and the particle size and number of the large particles and the small particles are within the scope of this application, the ionic conductivity of the sulfide solid electrolyte is relatively high; the carbon content is within the scope of this application, which can reduce the negative impact of excessive carbon impurity content on lithium-ion transport, thereby improving the ionic conductivity of the sulfide solid electrolyte. Within the scope of this application, the mass ratio of solvent to precursor can effectively reduce the carbon content in the solid sulfide electrolyte, thereby further improving its purity and ionic conductivity. The halogen-containing compounds include NH4X′ and LiX″, and the types of X′ and X″ are within the scope of this application, resulting in high purity and ionic conductivity in the sulfide solid electrolyte. The particle size distribution is within the scope of this application, giving the sulfide solid electrolyte a high packing density, thereby further improving its ionic conductivity. When the molar ratio of NH4X′ and LiX″ is within the above range, NH3 and H2S gases can be generated during heat treatment. NH3 and H2S gases not only serve as a protective atmosphere during calcination but also regulate the growth of the sulfide solid electrolyte, resulting in a more uniform particle size distribution and a narrower particle size distribution in the final product, which is beneficial for improving the electrochemical performance of the secondary battery.

[0117] As can be seen from Table 2, in Examples 2-1 to 2-6, the use of inert solvents that do not chemically react with the precursors to prepare sulfide solid electrolytes can avoid the occurrence of side reactions, thereby reducing the introduction of impurities such as carbon and oxygen, and thus improving the purity and ionic conductivity of the sulfide solid electrolytes. In Comparative Example 2-1, ethanol was used as a solvent. Due to the strong interaction between the precursor and the ethanol solvent, the precursor dissolved or even formed a complex, resulting in a high carbon impurity content and low ionic conductivity in the solid sulfide electrolyte.

[0118] As shown in Table 3, controlling the temperature and time of the first and second heat treatments within the range specified in this application is beneficial for complete solvent evaporation while reducing the reaction and decomposition of NH4X′. Controlling the time of the second heat treatment within the range specified in this application is beneficial for complete precursor reaction, ensuring that halogen atoms are essentially doped into the sulfide solid electrolyte cell, and minimizing carbonization caused by solvent residue, thereby improving the ionic conductivity and overall performance of the sulfide solid electrolyte. Controlling the heating rate of the first and second heat treatments within the range specified in this application can form a silver-sulfide germanium ore crystal structure, reduce product particle size, and create a sulfide solid electrolyte powder morphology where small particles are uniformly distributed on the surface of large particles, while simultaneously preventing excessively rapid solvent evaporation from introducing cavities into the product. Although the room temperature ionic conductivity values ​​of Comparative Examples 3-8 and 3-9 are relatively good, their excessively large particle size makes them unsuitable for practical applications.

[0119] As shown in Table 4, controlling the stirring time and rate within the range specified in this application is beneficial for the complete evaporation of the solvent, thereby improving the ionic conductivity and overall performance of the sulfide solid electrolyte. As shown in Table 5, doping with the oxides provided in this application can further improve the ionic conductivity of the sulfide solid electrolyte.

[0120] In summary, the sulfide solid electrolyte of this application exhibits a coral-like powder morphology, low carbon content, and high conductivity. Furthermore, the preparation method of this application, by using an inert solvent, avoids the reaction between the solvent and the precursor to generate oxygen impurities such as Li3PO4, mitigating carbonization during subsequent calcination, reducing the introduction of carbon impurities, and improving the purity of the sulfide solid electrolyte. Moreover, by using NH4X′ as a precursor component, NH3 and H2S gases can be generated during heat treatment, thereby regulating the growth of the sulfide solid electrolyte, resulting in a more uniform particle size distribution, a narrower particle size distribution, and higher ionic conductivity in the final product. Furthermore, batteries containing the sulfide solid electrolyte of this application or those prepared using the method of this application possess high safety and energy density, as well as excellent low-temperature performance, making them suitable for application in electric vertical takeoff and landing (EVTOL) aircraft, such as low-altitude economical manned EVTOL aircraft.

[0121] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A sulfide solid electrolyte with the chemical formula Li 7-a PS 6-a X a X is selected from at least one of Cl, Br, and I, 1 ≤ a ≤ 2; the sulfide solid electrolyte is composed of large particles and small particles, wherein the small particles are coated on the large particles; characterized in that, The large particles have a diameter of 3μm to 20μm, and the small particles have a diameter of 0.2μm to 0.8μm; the number of large particles accounts for 5% to 10% of the total number of particles, and the number of small particles accounts for 90% to 95% of the total number of particles.

2. The sulfide solid electrolyte according to claim 1, characterized in that, The carbon content of the sulfide solid electrolyte is ≤0.5wt%.

3. The sulfide solid electrolyte according to claim 1, characterized in that, The particle size of the sulfide solid electrolyte satisfies: 0.4µm < D v 50 < 0.7µm, 6µm < D MAX <8µm.

4. The sulfide solid electrolyte according to claim 1, characterized in that, The ionic conductivity of the sulfide solid electrolyte is >5.5 mS / cm.

5. A modified sulfide solid electrolyte, characterized in that, The modified sulfide solid electrolyte, based on the sulfide solid electrolyte of claim 1, further includes at least one of the following elements: O, Se, F, Mg, Ca, Sr, Zn, Sc, Sb, Si, Ge, Sn, B, Al, Ga, In, Ti, Zr, V, Nb, Cu, Ni, Mn, Cr, Ag, La, Ce, Tb, Te, Pb, As, Bi, Fe, Mo, and Co, wherein the elements are introduced by doping or coating.

6. A modified sulfide solid electrolyte, characterized in that, The modified sulfide solid electrolyte is prepared by incorporating oxides into the raw materials for the preparation of the sulfide solid electrolyte according to claim 1. The oxides are selected from at least one of MgO, CaO, V2O5, MnO2, Fe2O3, CoO, NiO, CuO, ZnO, ZrO2, MoO3, Ag2O, SrO, TiO2, Cr2O3, CeO2, and PbO.

7. A method for preparing a sulfide solid electrolyte, comprising: Under an inert atmosphere, the precursor and solvent are mixed and mechanically stirred to obtain a suspension; characterized in that the precursor comprises Li2S, P2S5 and a halogen-containing compound; the halogen-containing compound comprises NH4X′ and LiX″, wherein X′ and X″ are each independently selected from at least one of Cl, Br and I; the molar ratio of NH4X′ and LiX″ is 1:(0~1); the mass ratio of the precursor to the solvent is 1:(2~4); the solvent is selected from at least one of n-hexane, benzene, toluene, cyclohexane, n-pentane, acetonitrile, cyclopentane and dimethyl carbonate; The suspension was allowed to stand at room temperature and pressure under an inert atmosphere to allow the solvent to evaporate, yielding a solid electrolyte precursor mixture; the solvent evaporation rate was 1.5–7.0 mg / cm³. 2 • h, based on the mass of the solvent, the residual rate of the solvent after evaporation is less than 5 wt%; The solid electrolyte precursor mixture is heat-treated under an inert atmosphere to obtain the sulfide solid electrolyte; wherein the heat treatment includes a first heat treatment and a second heat treatment, the heating rate of the first heat treatment is 1~2℃ / min, the temperature of the first heat treatment is 60~80℃, and the time of the first heat treatment is 1~3h; the heating rate of the second heat treatment is 7~10℃ / min, the temperature of the second heat treatment is 450~600℃, and the time of the second heat treatment is 4~10h. The chemical formula of the sulfide solid electrolyte is Li. 7-a PS 6-a X a X is selected from at least one of Cl, Br and I, and 1≤a≤2.

8. The preparation method according to claim 7, characterized in that, The inert atmosphere is selected from at least one of nitrogen and argon.

9. The preparation method according to claim 7, characterized in that, The mechanical stirring is carried out at normal temperature and pressure for 12-24 hours and at a speed of 300-600 rpm.

10. A battery comprising a positive electrode, a negative electrode, and a sulfide solid electrolyte according to any one of claims 1 to 4, or a modified sulfide solid electrolyte according to any one of claims 5 to 6, or a sulfide solid electrolyte prepared by any one of claims 7 to 9.

11. The application of the battery of claim 10 in an aircraft, characterized in that, The aircraft is selected from low-altitude manned electric vertical takeoff and landing aircraft.

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