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 halogen, and 1<=a<=2; wherein the peak area of a diffraction peak corresponding to a (111) crystal face of the sulfide solid electrolyte is I1, the peak area of a diffraction peak corresponding to a (311) crystal face of the sulfide solid electrolyte is I2, and 0.2<=I1 / I2<=0.3. The I1 / I2 of the sulfide solid electrolyte in the application is in the above range, which can provide a good crystal structure and a large interface area, promote ion movement, and thus obtain a high ion conductivity. Further, the method in the application reduces the solvent consumption and optimizes the sintering step, ensures the high ion conductivity of the product, and significantly reduces environmental pollution, energy consumption and 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 application of the battery. BACKGROUND

[0002] Solid-state electrolyte material is one of the key cores to realize high safety and high energy density full solid-state lithium battery. In recent years, sulfide solid-state electrolyte has attracted widespread attention due to its relatively high room temperature ionic conductivity and good interface contact. However, the ionic conductivity of most current sulfide electrolyte systems is still difficult to meet the practical application requirements of high power output or rapid charge and discharge, which is one of the important factors restricting its industrialization and popularization.

[0003] The existing researches in improving the performance of sulfide solid-state electrolyte are mostly focused on optimizing chemical composition, adjusting doping elements or improving sintering process, but the fine regulation of the crystal structure of the material, especially the crystal face structure, is relatively less. Since the sulfide electrolyte has anisotropic crystal structure, there is a significant difference in lithium ion conductivity in different crystal face directions. If the crystal face orientation distribution is disordered, the ion migration channels in the material will be non-uniformly distributed, and even blocked, which seriously affects the effective diffusion path of lithium ions, resulting in low overall conductivity. However, the existing technology still lacks a systematic regulation method for the crystal orientation of the electrolyte material, and most of the preparation strategies still remain in the stage of disordered dense sintering, which is difficult to realize the directional construction of the crystal structure. SUMMARY

[0004] The purpose of the present application is to provide a sulfide solid-state electrolyte, a preparation method thereof, a battery comprising the sulfide solid-state electrolyte and application of the battery, which can accurately regulate the proportion of the target crystal face during the formation process of the sulfide solid-state electrolyte, thereby constructing a continuous and low-impedance lithium ion migration path, thereby significantly improving the ionic conductivity of the sulfide solid-state electrolyte material, and providing key support for the development of high-performance full solid-state batteries. The specific technical solutions are as follows:

[0005] The first aspect of the present application provides a sulfide solid-state electrolyte, which has a chemical formula of Li 7-a PS 6-a X a X is halogen, 1≤a≤2; wherein the peak area of the diffraction peak corresponding to the (111) crystal face of the sulfide solid-state electrolyte is I1, the peak area of the diffraction peak corresponding to the (311) crystal face of the sulfide solid-state electrolyte is I2, and I1 and I2 satisfy: 0.2≤I1 / I2≤0.3.

[0006] In an embodiment of the present application, the full width at half maximum of the diffraction peak corresponding to the (111) crystal plane of the sulfide solid-state electrolyte is x1, and the full width at half maximum of the diffraction peak corresponding to the (311) crystal plane of the sulfide solid-state electrolyte is x2, x1 and x2 satisfy: 0.12 < x1 < 0.2, and 0.14 < x2 < 0.22.

[0007] In an embodiment of the present application, the particle size of the sulfide solid-state electrolyte satisfies: 0.5 µm < D50 < 1 µm, 1.4 µm < D90 < 2 µm, and 10 µm < D MAX < 15 µm.

[0008] In an embodiment of the present application, the ionic conductivity of the sulfide solid-state electrolyte is ≥ 5.3 mS / cm.

[0009] In an embodiment 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, Hf, Y and Ru elements, which are introduced by doping or coating.

[0010] In an embodiment of the present application, the surface of the sulfide solid-state electrolyte is coated with an inert oxide layer, and the inert oxide layer is selected from at least one of Li2O, Al2O3, V2O5, ZnO, ZrO2, TiO2, MgO, RuO2, La2O3, CeO2, HfO2, Y2O3, SiO2, B2O3, CuO, NbO2, LiNbO3, LiAlO2.

[0011] The second aspect of the present application provides a preparation method of the sulfide solid-state electrolyte provided in the first aspect of the present application, which comprises:

[0012] Under the protection of an inert atmosphere, the substrate is mixed with a solvent and mechanically stirred to obtain a solid mixture; wherein the substrate comprises Li2S, P2S5 and LiX, X is halogen; the substrate is respectively crushed to 3 µm ≤ D50 ≤ 10 µm before being mixed with the solvent; the molar ratio of the Li2S to the P2S5 is (3-5):1; the molar ratio of the P2S5 to the LiX is 1:(2-4); and the mass ratio of the solvent to the substrate is 1:(1.5-3);

[0013] The solid mixture is left to stand at normal temperature and pressure to volatilize the solvent, thereby obtaining a solid electrolyte precursor mixture;

[0014] sintering the solid-state electrolyte precursor mixture to obtain a sulfide solid-state electrolyte; wherein the sintering comprises a first sintering and a second sintering, the first sintering is at a temperature of 150-300℃ for a time of 1-6h; the second sintering is at a temperature of 450-600℃ for a time of 10-15h.

[0015] In an embodiment of the present application, the substrate and the solvent are separately crushed to 5µm≤D50≤8µm before mixing.

[0016] In an embodiment of the present application, the first sintering is at a temperature of 200-300℃ for a time of 3-6h; the second sintering is at a temperature of 550-600℃ for a time of 10-13h.

[0017] In an embodiment of the present application, the first sintering is at a temperature of 200-300℃ for a time of 3-6h; the second sintering is at a temperature of 550-600℃ for a time of 10-13h.

[0018] In an embodiment of the present application, the solvent is selected from at least one of n-hexane, benzene, toluene, cyclohexane, n-pentane, cyclopentane and dimethyl carbonate.

[0019] In an embodiment of the present application, the mechanical stirring is carried out at normal temperature and pressure, the rotational speed of the mechanical stirring is 300rpm-600rpm, and the time of the mechanical stirring is 10-50min.

[0020] In an embodiment of the present application, the rate of solvent evaporation is 1.5-7.0 mg / cm 2 ·h.

[0021] In an embodiment of the present application, the sulfide solid-state electrolyte after sintering needs to be further treated, and the post-treatment comprises crushing.

[0022] The third aspect of the present application provides a battery comprising a positive electrode sheet, a negative electrode sheet and the sulfide solid-state electrolyte of the first aspect of the present application or the sulfide solid-state electrolyte prepared by the preparation method of the second aspect of the present application.

[0023] The fourth aspect of the present application provides the use of the battery of the third aspect of the present application in an electric vertical take-off and landing aircraft.

[0024] The beneficial effects of the present application are as follows:

[0025] The present application provides a sulfide solid-state electrolyte, a preparation method thereof, a battery and use thereof, the chemical formula of the sulfide solid-state electrolyte is Li 7-a PS 6-a X aX is halogen, 1<=a<=2; wherein the peak area of the diffraction peak corresponding to the (111) crystal face of the sulfide solid-state electrolyte is I1, the peak area of the diffraction peak corresponding to the (311) crystal face of the sulfide solid-state electrolyte is I2, I1 and I2 satisfy: 0.2<=I1 / I2<=0.3. The problem of crystal orientation disorder exists in the existing sulfide solid-state electrolyte, especially under uncontrolled synthesis conditions, the proportion of each crystal face in the grain is uneven, which leads to discontinuous lithium ion migration path or high energy barrier, thereby limiting the improvement of ion conductivity of the sulfide solid-state electrolyte. In view of the technical problem, the present application optimizes the synthesis process conditions, controls the ratio of the peak areas of the diffraction peaks corresponding to the (111) crystal face and the (311) crystal face in the sulfide solid-state electrolyte, realizes the optimization of crystal orientation, and improves the lithium ion migration path inside. Specifically, the (311) crystal face has a lower migration barrier, and appropriately increasing its proportion is conducive to building a more continuous and low-resistance ion conduction channel, thereby improving the overall ion conductivity; while the (111) crystal face has certain advantages in structural stability, which helps to maintain the mechanical strength and sintering density of the sulfide solid-state electrolyte. By controlling the crystal face ratio within the range of the present application (0.2<=I1 / I2<=0.3), the ion conductivity is improved on the basis of ensuring the structural stability of the sulfide solid-state electrolyte.

[0026] Further, the preparation method of the present application reduces the amount of solvent used, not only reducing production costs and environmental impact, but also simplifying the subsequent drying process, thereby improving overall production efficiency; by controlling the sintering temperature and time, the ion conductivity and phase purity of the electrolyte are improved, and the overall performance of the electrolyte is also enhanced. Further, the battery containing the sulfide solid-state electrolyte of the present application or the sulfide solid-state electrolyte prepared by the preparation method of the present application has high safety and energy density and good low-temperature performance, and can be applied to electric vertical take-off and landing aircraft, such as low-altitude economic manned electric vertical take-off and landing aircraft.

[0027] Of course, implementing any product or method of the present application does not necessarily require achieving all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other embodiments can also be obtained by those skilled in the art based on these drawings.

[0029] Figure 1 X-ray diffraction pattern of the sulfide solid-state electrolyte (Li6PS5Cl) prepared for Example 1-1;

[0030] Figure 2 X-ray diffraction pattern of the sulfide solid electrolyte (Li 5.5 PS 4.5 Cl 1.5 ) prepared in Example 1-4;

[0031] Figure 3 X-ray diffraction pattern of the sulfide solid electrolyte (Li

[0032] Figure 4 X-ray diffraction pattern of the sulfide solid electrolyte (Li Figure 1 X-ray diffraction pattern of the sulfide solid electrolyte (Li

[0033] Figure 5 X-ray diffraction pattern of the sulfide solid electrolyte (Li Figure 1 X-ray diffraction pattern of the sulfide solid electrolyte (Li

[0034] Figure 6 X-ray diffraction pattern of the solid electrolyte precursor mixture of Example 1-1;

[0035] Figure 7 X-ray diffraction pattern of the electrolyte precursor powder of Comparative Example 5-1. DETAILED DESCRIPTION

[0036] The technical solutions in the present application will be described clearly and completely below in combination with the embodiments and drawings of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. All other embodiments obtained by those skilled in the art based on the present application are within the scope of the present application.

[0037] A first aspect of the present application provides a sulfide solid electrolyte with a chemical formula of Li 7-a PS 6-a X a , X is halogen, 1≤a≤2; wherein the peak area of the diffraction peak corresponding to the (111) crystal face of the sulfide solid electrolyte is I1, the peak area of the diffraction peak corresponding to the (311) crystal face of the sulfide solid electrolyte is I2, and I1 and I2 satisfy: 0.2≤I1 / I2≤0.3. The inventors have found that in the sulfide solid electrolyte, the (111) crystal face belongs to a low-index face, and the structure is relatively dense, which can effectively inhibit the disorder expansion of defects and vacancies in the crystal; while the (311) crystal face is a high-index face, which has a large surface energy and a rich diffusion channel, and is conducive to the migration of lithium ions. By adjusting I1 / I2 within the range of the present application, a uniform and continuous ion diffusion path can be formed in the sulfide solid electrolyte, while the formation of excessive grain boundary resistance or non-conductive regions is inhibited, thereby facilitating the improvement of the ionic conductivity of the sulfide solid electrolyte.

[0038] When the I1 / I2 ratio is too low (<0.2), the proportion of high-index surfaces in the sulfide solid-state electrolyte is too high, which can cause the surface of the crystal grain to be too loose, the interface stability to decrease, and then introduce more grain boundary defects or secondary phase deposition, which is not conducive to the continuity of ion migration; and when the I1 / I2 ratio is too high (>0.3), the proportion of low-index surfaces is too large, which can improve the crystal density, but due to the limited number of diffusion channels of the (111) crystal surface, the effective migration of lithium ions is inhibited.

[0039] The present application successfully realizes the controllable adjustment of the relative proportion of (111) crystal surface and (311) crystal surface in the material by optimizing the preparation process of the sulfide solid-state electrolyte, thereby improving the continuity of the ion migration path and improving the ionic conductivity of the sulfide solid-state electrolyte. It is found through XRD testing that the diffraction peak area ratio of (111) crystal surface and (311) crystal surface in the sample changes obviously under different process conditions. Experiments prove that when the ratio is in the range of 0.2-0.3, the material exhibits the best ionic conductivity and structural density. In combination with the preparation process, the inventors have found that the following factors have a great influence on the crystal surface ratio:

[0040] (1) Substrate particle size: Controlling the substrate particle size D50 in the range of the present application (3-10 μm) is conducive to uniform diffusion and crystal nucleus distribution of the reaction, thereby providing a good foundation for crystal directional growth. Too large particle size can cause local concentration unevenness, induce the formation of non-ideal (311) crystal surface, and cause the I1 / I2 ratio to be less than 0.2, and too small particle size can cause particle agglomeration during sintering, imbalance of crystal surface ratio, and cause the I1 / I2 ratio to be too high.

[0041] (2) Solvent type and amount: Using a solvent with low polarity and inertia in the range of the present application can inhibit the directional complexation reaction between the substrates, which is conducive to the preferential growth of (111) crystal surface, so that the I1 / I2 ratio is in the range of the present application. Controlling the mass ratio of solvent to substrate in the range of the present application can help to control the nucleation site, thereby affecting the crystal growth direction; but too large solvent amount can cause crystal surface structure disorder, so that the I1 / I2 ratio is greater than 0.3.

[0042] (3) Second sintering temperature and time: The second sintering determines the directionality of crystal growth, and the sintering temperature in the range of the present application (450-600℃) can guide the crystal to continue growing along the low-energy surface (111), thereby increasing the proportion of (111) crystal surface and making the I1 / I2 ratio in the range of the present application. If the temperature is too high or the holding time is too long, the system tends to be in a thermodynamic equilibrium state, and the re-precipitation of high-index crystal surface (311) is easy to occur, which reduces the crystal surface ratio and makes the I1 / I2 ratio less than 0.2.

[0043] In addition, the formation of the crystal plane structure is not only affected by a single process parameter, but also by the interaction between multiple parameters. A reasonable parameter combination is crucial for achieving an ideal (111) / (311) crystal plane ratio.

[0044] (1) There is a synergistic relationship between the mass ratio of solvent to substrate and the second sintering temperature. Under moderate solvent dosage conditions, lower sintering temperature is easy to form (111) crystal plane with better orientation, so that the I1 / I2 ratio is within the scope of the present application; but if the solvent is insufficient and the temperature is increased, the crystal growth process lacks effective restriction, which easily promotes the abnormal exposure of high-energy surface (311), leading to unbalanced crystal plane ratio, and the I1 / I2 ratio is less than 0.2.

[0045] (2) There is a synergistic effect between the second sintering conditions and the particle size of the substrate. When the particle size of the substrate is small (D50 close to the lower limit), the crystal grains have higher reactivity and larger specific surface area. At this time, if a higher second-step sintering temperature or longer holding time is used, it is easy to lead to rapid grain growth, and the preferred growth direction of the crystal plane in the local area is out of control, inducing the increase of (111) crystal plane ratio. Under the same sintering conditions, if the particle size of the substrate is moderate (such as D50 in the middle range), the crystal grain growth process is more controllable, which is conducive to maintaining a suitable (311) crystal plane ratio. Therefore, fine particle systems are more suitable for moderate temperature and time sintering parameters to avoid unbalanced crystal plane structure, so that the I1 / I2 ratio is within the scope of the present application.

[0046] (3) There is a synergistic relationship between the particle size of the substrate and the solvent dosage. Smaller particle size of the substrate has higher surface energy and stronger agglomeration tendency. If the solvent dosage is insufficient, it is easy to cause uneven mixing, poor dispersion, and then form local orientation abnormalities, affecting the uniformity of the crystal structure and increasing the probability of (311) crystal plane formation. On the contrary, appropriately increasing the solvent dosage can effectively alleviate the agglomeration of fine particles, improve the mixing uniformity, and promote the uniform contact of reactant interfaces, thereby providing a basis for subsequent crystal plane ordered growth. For larger particle size raw materials, too much solvent dosage may cause reaction dilution and decrease in nucleation density, which is not conducive to the formation of stable (111) crystal plane ratio. Therefore, in practical application, appropriate solvent ratio should be selected in combination with the particle size of the raw material to achieve synergistic regulation of the crystal plane structure, so that the I1 / I2 ratio is within the scope of the present application.

[0047] Therefore, the application establishes a set of sulfide solid electrolyte preparation process systems that can be used to accurately control the crystal face ratio by the combined design and mutual matching of multiple key process parameters (including solvent usage, sintering temperature and time, substrate particle size, etc.). The system can avoid the instability factors brought by single parameter adjustment, and achieve the consistency of the crystal face orientation and the optimization of the electrochemical performance of the final sulfide solid electrolyte product. By adjusting the above process parameters, the peak area ratio I1 / I2 of the diffraction peaks corresponding to the (111) / (311) crystal faces in the XRD pattern of the product is kept in the interval of 0.2-0.3, so as to improve the ion conductivity and overall performance of the sulfide solid electrolyte, and meet the use requirements of high-performance all-solid-state battery materials.

[0048] In the application, the (311) crystal face of the sulfide solid electrolyte corresponds to a diffraction peak at 2θ = 30.3±0.5°; and the (111) crystal face of the sulfide solid electrolyte corresponds to a diffraction peak at 2θ = 15.8±0.5°.

[0049] In an embodiment of the application, the half-peak width of the diffraction peak corresponding to the (111) crystal face of the sulfide solid electrolyte is x1, and the half-peak width of the diffraction peak corresponding to the (311) crystal face of the sulfide solid electrolyte is x2, x1 and x2 satisfy: 0.12 < x1 < 0.2, 0.14 < x2 < 0.22. The x1 and x2 of the sulfide solid electrolyte of the application are in the above range, so that the sulfide solid electrolyte has high ion conductivity.

[0050] In an embodiment of the application, the particle size of the sulfide solid electrolyte satisfies: 0.5µm < D50 < 1µm, 1.4µm < D90 < 2µm, 10µm < D MAX < 15µm. The particle size D50, D90 and D MAX In the above range, the sulfide solid electrolyte has good processing performance.

[0051] In an embodiment of the application, the ion conductivity of the sulfide solid electrolyte is ≥5.3mS / cm. The inventors found in the research that the sulfide solid electrolyte of the application has high ion conductivity, and can improve the safety performance, energy density and low-temperature performance of the battery when applied to the battery.

[0052] In an embodiment 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, Hf, Y and Ru, which are introduced by doping or coating.

[0053] In the present application, the doping methods include but are not limited to introducing the doping elements in the substrate and solvent mixing stage or introducing the doping elements in the sintering stage with sintering aids; and the coating methods include but are not limited to forming a coating layer containing the doping elements on the surface of the sulfide solid-state electrolyte by ball milling, vapor deposition or atomic spraying, etc.

[0054] In an embodiment of the present application, the surface of the sulfide solid-state electrolyte is coated with an inert oxide layer selected from at least one of Li2O, Al2O3, V2O5, ZnO, ZrO2, TiO2, MgO, RuO2, La2O3, CeO2, HfO2, Y2O3, SiO2, B2O3, CuO, NbO2, LiNbO3, LiAlO2. The sulfide solid-state electrolyte coated with the inert oxide layer can effectively improve the interface stability and air stability of the solid-state electrolyte. The sulfide solid-state electrolyte coated with the inert oxide layer is prepared by the above coating method. For example, the sulfide solid-state electrolyte Li 7-a PS 6-a X a is mixed with at least one of the above inert oxides, resealed and ball milled to obtain the sulfide solid-state electrolyte coated with the inert oxide layer. The mass ratio of the sulfide solid-state electrolyte Li 7-a PS 6-a X a The mass ratio of the sulfide solid-state electrolyte Li

[0055] The second aspect of the present application provides a preparation method of the sulfide solid-state electrolyte provided in the first aspect of the present application, which comprises:

[0056] The substrate is mixed with a solvent under the protection of an inert atmosphere, and mechanical stirring is performed to obtain a solid mixture; wherein the substrate comprises Li2S, P2S5 and LiX, X is halogen; before the substrate is mixed with the solvent, each is crushed to 3 µm ≤ D50 ≤ 10 µm, preferably 5 µm ≤ D50 ≤ 8 µm; the molar ratio of the Li2S to the P2S5 is (3-5):1; the molar ratio of the P2S5 to the LiX is 1:(2-4); and the mass ratio of the solvent to the substrate is 1:(1.5-3). For example, before the substrate is mixed with the solvent, each can be crushed to D50 of 3 µm, 4 µm, 5 µm, 6 µm, 7 µm, 8 µm, 9 µm, 10 µm, or a range formed by any two of the values; the molar ratio of the Li2S to the P2S5 can be 3:1, 4:1, 5:1, or a range formed by any two of the values; the molar ratio of the P2S5 to the LiX can be 1:2, 1:3, 1:4, or a range formed by any two of the values; and the mass ratio of the solvent to the substrate can be 1:1.5, 1:2, 1:3, or a range formed by any two of the values. The molar ratio of the substrate is limited within the above range, which can avoid the change of material structure and thus the decrease of ionic conductivity; the mass ratio of the solvent to the substrate is limited within the above range, which not only reduces the production cost but also reduces environmental pollution compared with the traditional liquid phase method; at the same time, by reducing the amount of solvent, the drying step does not need vacuum drying, but can be completed by standing at normal temperature and pressure, which not only reduces the energy consumption but also reduces the production cost. Since the amount of solvent used in the wet mixing process is small and the stirring time is short, the substrate needs to be pretreated to have a D50 ≤ 10 µm, so that good dispersion can be achieved in the wet mixing process, thereby achieving a more uniform and complete reaction during sintering, improving the uniformity of the product and the ionic conductivity; if the particle size is less than 3 µm, the specific surface area of the substrate powder will increase significantly, which is easy to cause agglomeration during sintering, resulting in uneven particle growth and increased structural defects, and excessive crushing may damage the crystal structure of the substrate itself, causing deterioration of the raw material.

[0057] The amount of solvent plays a role in wetting and mixing the substrate during the wet mixing process. An appropriate amount of solvent can make each component fully contact and uniformly mix on a microscale, which is helpful for forming crystal nuclei with consistent orientation; on the contrary, an insufficient amount of solvent will lead to particle agglomeration, local formation of unevenly distributed crystal faces, or preferential growth of non-ideal crystal faces, thereby affecting the control accuracy of the I1 / I2 ratio in the final sulfide solid electrolyte product.

[0058] Specifically, the lithium sulfide (Li2S), phosphorus pentasulfide (P2S5) and lithium halide (such as LiCl, LiBr) used are each crushed to a D50 in the range of 3-10 μm. This particle size distribution is significantly different from the particle size of conventional raw materials on the market, and belongs to an unconventional particle size design. Among them, commercially available lithium sulfide is usually supplied in the form of particles or agglomerated blocks, and the market particle size is generally 50-200 μm; commercially available phosphorus pentasulfide is mainly in the form of obvious sheets or sheet blocks, and the industrial grade particle size is more than 100 μm, not only is the particle size large but also is easy to accumulate unevenly, and it is difficult to form a uniform mixing system; and commercially available lithium halide such as LiCl and LiBr is usually in the form of large particles or crystalline powder, and the particle size generally exceeds 100 μm, and is easy to absorb moisture and form lumps, further affecting the dispersion uniformity and reaction activity. Controlling the D50 of the substrate within the range of the present application is conducive to the uniform diffusion and crystal nucleus distribution of the reaction, thereby providing a good foundation for the directional growth of the crystal, and further improving the ionic conductivity of the sulfide solid electrolyte.

[0059] The solid-state mixture is left to stand at normal temperature and pressure to volatilize the solvent, to obtain a solid electrolyte precursor mixture; the preparation method of the present application selects normal temperature and pressure standing drying, compared with other drying methods such as heating and vacuum drying, a large amount of solvent can be volatilized in the mixture at the same time to form a cavity, thereby further improving the ionic conductivity and overall performance of the electrolyte.

[0060] sintering the solid electrolyte precursor mixture to obtain a sulfide solid electrolyte; wherein the sintering comprises a first sintering and a second sintering, the first sintering has a temperature of 150-300°C and a time of 1-6h; preferably, the temperature is 200-300°C and the time is 3-6h; the second sintering has a temperature of 450-600°C and a time of 10-15h; preferably, the temperature is 550-600°C and the time is 10-13h. For example, the first sintering has a temperature of 150°C, 200°C, 250°C, 300°C or a range between any two of them, and a time of 1h, 2h, 3h, 4h, 5h, 6h or a range between any two of them; the second sintering has a temperature of 450°C, 500°C, 550°C, 600°C or a range between any two of them, and a time of 10h, 11h, 12h, 13h, 14h, 15h or a range between any two of them. The inventors found in the research that the substrate starts to react during the second sintering, when the second sintering time or sintering temperature is lower than the range of the present application, the substrate is not fully reacted, and the appropriate crystal surface is not formed, I1 / I2 is large, thus leading to a lower ionic conductivity; while when the second sintering time or sintering temperature is higher than the range of the present application, the product sulfide solid electrolyte (LPSC) undergoes a side reaction, leading to the precipitation of LiX (such as LiCl), I1 / I2 decreases, thus leading to the destruction of the overall structure of the product and the decrease of ionic conductivity; at the same time, the sintering method of the present application avoids the complex process of reduced pressure drying, directly completes the drying and sintering process of the remaining solvent, reduces the equipment demand and energy consumption, and improves the ionic conductivity and overall performance of the electrolyte by controlling the sintering temperature and time.

[0061] The sintering temperature determines the driving force of crystal growth and the rearrangement rate of particles. Controlling the second sintering temperature within the range of the present application, the volatile elements such as lithium, sulfur and halogen can exist stably, which is conducive to the controlled growth of crystal grains between crystal surfaces and promotes the formation of a reasonable proportion of (111) and (311) crystal surfaces. However, too high a temperature will accelerate the reconstruction of crystal surfaces, induce non-uniform growth or produce crystal surface collapse, leading to an imbalance in the proportion of crystal surfaces; while too low a temperature may hinder the complete formation of crystals, resulting in insufficient selective growth of crystal surfaces and affecting the construction of ion migration channels.

[0062] The second sintering time affects the full growth of the crystal grains and the stability of the crystal face orientation. Short sintering time can cause the crystal grains not to be fully matured, and the crystal face ratio deviates from the target range; too long time can cause grain coarsening or structure defect accumulation, increasing the grain boundary impedance. Experimental results show that when the mass ratio of the solvent to the substrate and the sintering temperature and time of the second sintering are controlled within the ranges of the present application, the peak area ratio I1 / I2 of the diffraction peaks corresponding to the (111) and (311) crystal faces in the sulfide solid electrolyte can be stably maintained between 0.2-0.3, thereby realizing the synergistic optimization of high ionic conductivity.

[0063] In an embodiment of the present application, the heating rate of the first sintering is 2-5℃ / min; and the heating rate of the second sintering is 5-10℃ / min. For example, the heating rate of the first sintering can be 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, or a range formed by any two of the above values; and the heating rate of the second sintering can be 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, or a range formed by any two of the above values. The heating rates of the two sinterings in the present application are limited within the above ranges, which can prevent the volatilization of the solvent from introducing too many voids in the sulfide solid electrolyte, and the crystal structure of the sulfide solid electrolyte is complete and has high ionic conductivity.

[0064] The purpose of the first sintering is to remove the residual solvent in the system without introducing a large number of cavities in the product due to rapid volatilization of the solvent, and the heating rate needs to be maintained at 2-5℃ / min. Too high heating rate can cause the solvent to evaporate too quickly and introduce cavities; and too low heating rate can cause the heating time to be too long, increasing the working hours and energy consumption. The purpose of the second sintering is to form argyrodite crystal form, thereby obtaining a sulfide product with high ionic conductivity, and the heating rate needs to be maintained at 5-10℃ / min. Too high heating rate can easily damage the heating equipment and cause temperature runaway, resulting in uneven heating temperature; and lower than this heating rate can cause some phosphorus pentasulfide to decompose to produce gas that cannot act on the final product before the raw materials start to react to form the target crystal form, resulting in the product with unsuitable element ratio.

[0065] In the present application, the method for controlling the heating rate is not particularly limited as long as it can achieve the purpose of the present application, for example, the heating rate can be set by the heating program of the sintering furnace, and the selection of the sintering furnace is not particularly limited in the present application, for example, a tubular furnace with model NBD-T1500-100T2GF can be selected.

[0066] In the present application, the inert atmosphere is not particularly limited as long as it can achieve the purpose of the present application, for example, the inert atmosphere is selected from, but not limited to, at least one of argon and nitrogen.

[0067] In the present application, the halogen is at least one of Cl, Br and I.

[0068] In the present application, the condition for standing the solid mixture is not particularly limited, and any condition that can achieve the object of the present application is acceptable, for example, the mixture is left standing overnight under the protection of inert atmosphere at room temperature and normal pressure, the solvent is volatilized, and the residual amount of the solvent is kept below 5wt%.

[0069] In an embodiment of the present application, the solvent is selected from the solvent that does not react with the substrate; preferably, the solvent is selected from at least one of n-hexane, benzene, toluene, cyclohexane, n-pentane, cyclopentane and dimethyl carbonate. The inventors have found in the research that the use of the solvent of the present application can achieve better interaction between the substrates, exhibit moderate I1 / I2, thereby the ionic conductivity of the sulfide solid electrolyte is higher, and at the same time, the hydrolysis of the precursor can be avoided, the content of oxygen impurities (such as Li3PO4) in the electrolyte is reduced, thereby the purity and ionic conductivity of the electrolyte are improved. The use of solvent with low polarity and inertness can inhibit the directional complexation reaction between the substrates, and is conducive to the preferential growth of (111) crystal surface. Controlling the mass ratio of the solvent to the substrate within the range of the present application can achieve uniform dispersion of the substrate particles, which is helpful to control the nucleation site, thereby affecting the crystal growth direction; but excessive amount can easily lead to disorder of the crystal surface structure.

[0070] In an embodiment of the present application, the mechanical stirring is carried out at room temperature and pressure, and the rotation speed of the mechanical stirring is 300 rpm to 600 rpm, and the time of the mechanical stirring is 10 to 50 min. For example, the rotation speed of the mechanical stirring can be 300 rpm, 350 rpm, 400 rpm, 480 rpm, 520 rpm, 600 rpm, or a range defined by any two of the above values. The stirring time can be 10 min, 20 min, 30 min, 40 min, 50 min, or a range defined by any two of the above values. By adjusting the mixing method of the substrate and the solvent, the temperature, pressure and rotation speed of the mechanical stirring within the above range, the reaction between the substrates can be avoided during stirring, and the full and uniform solid phase reaction of the substrates can be ensured in the sintering stage, which is beneficial to the preparation of sulfide solid electrolyte and the obtaining of a suitable (111) crystal plane and (311) crystal plane ratio. When other mixing methods (such as ultrasonic dispersion, etc.), high temperature and high pressure mechanical stirring or too high rotation speed (for example, greater than 600 rpm) are used, the reaction between the substrates may occur, resulting in uneven reaction in the subsequent preparation of sulfide solid electrolyte, destroying the ordered growth of the crystal, and making the crystal plane orientation distribution disordered, especially causing the (111) crystal plane and (311) crystal plane ratio to deviate from the expected range, affecting the ionic conductivity of the sulfide solid electrolyte. In addition, the stirring time of the present application is limited within the above range, which can make the substrates more fully contacted, thereby obtaining higher ionic conductivity. In summary, by adjusting the mixing method of the substrate and the solvent to mechanical stirring and adjusting the mechanical stirring conditions within the above range, the crystal orientation can be optimized, the lithium ion migration path inside the sulfide solid electrolyte can be improved, and the ionic conductivity thereof can be improved.

[0071] In an embodiment of the present application, the solvent evaporation rate is 1.5 to 7.0 mg / cm 2 ·h. For example, the solvent evaporation rate can be 1.5 mg / cm 2 ·h, 3 mg / cm 2 ·h, 4.5 mg / cm 2 ·h, 6 mg / cm 2 ·h, 7.0 mg / cm 2 ·h, or a range defined by any two of the above values. The inventors have found in their research that the solvent evaporation rate of the present application is limited within the above range, which can avoid the formation of cavities in the mixture due to the simultaneous evaporation of a large amount of solvent, thereby further improving the ionic conductivity and overall performance of the electrolyte.

[0072] The method for controlling the evaporation rate of the solvent is not particularly limited in the present application, as long as it can achieve the purpose of the present application. For example, in a room temperature and normal pressure environment, the thickness of the solid-state electrolyte precursor mixture is controlled to be 1-5 mm, and the specific surface area of the solid-state electrolyte precursor mixture per gram is controlled to be 1.5-3 cm 2 The thickness and specific surface area can be obtained by measuring from the outside of the container.

[0073] In the present application, the mass of the solid-state electrolyte precursor mixture before and after evaporation is determined by weighing, m0 and m1, m0 minus m1 is the evaporation amount of the solvent in the evaporation time, and the evaporation rate v of the solvent is obtained by dividing the evaporation time t and the specific surface area S, v=(m0-m1) / (t×S).

[0074] In summary, by crushing the substrates respectively, controlling the D50 of the substrates, using the inert solvent within the scope of the present application, and by controlling the stirring speed and stirring time when the substrates are mixed with the solvent, the substrates can be prevented from reacting before the first sintering. If the substrates react partially before sintering, it is easy to cause non-uniformity in the reaction process, destroy the ordered growth of the crystal, and make the crystal face orientation distribution disorderly, especially causing the ratio of (111) crystal face to (311) crystal face to deviate from the expected range. The substrates do not react in advance before sintering, so that the solid-phase reaction in the sintering stage can be carried out under controlled conditions, and the nucleation and growth path of the crystal can be controlled, thereby facilitating the control of the ratio of the peak areas of the diffraction peaks corresponding to the (111) crystal face and the (311) crystal face in the sulfide solid-state electrolyte within the scope of the present application, and further improving the ionic conductivity.

[0075] In an embodiment of the present application, the sintering is followed by post-treatment, which includes crushing. The specific implementation of crushing is not particularly limited in the present application, as long as it can achieve the purpose of the present application. For example, grinding, mechanical crushing and high-energy ball milling can be used for crushing.

[0076] The third aspect of the present application provides a battery comprising a positive electrode sheet, a negative electrode sheet and the sulfide solid-state electrolyte of the first aspect of the present application or the sulfide solid-state electrolyte prepared by the preparation method of the second aspect of the present application. The use of the sulfide solid-state electrolyte of the present application or the sulfide solid-state electrolyte prepared by the preparation method of the present application in the battery greatly improves the safety, energy density and low-temperature performance of the battery.

[0077] The positive electrode sheet and the negative electrode sheet in the battery are not particularly limited in the present application, as long as they can achieve the purpose of the present application.

[0078] The fourth aspect of the present application provides the application of the battery of the third aspect of the present application in an electric vertical take-off and landing aircraft, especially in a manned electric vertical take-off and landing aircraft for low-altitude economy, which can improve the flight endurance, safety performance and extreme environment performance of the spacecraft. At the same time, the long-life battery can reduce the maintenance frequency and cost of the aircraft.

[0079] Embodiments

[0080] Hereinafter, embodiments and comparative examples are given to more specifically describe the embodiments of the present application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts", "%" are mass-based, "room temperature" is 25±5°C, "normal pressure" is 101 kPa, and "overnight" is 12-24 h.

[0081] Test method and equipment:

[0082] Ion conductivity test

[0083] In an argon-filled glove box, 100 mg of solid electrolyte powder was weighed and placed in a mold battery with a stainless steel sheet of 9 mm in diameter at both ends (Wuhan Chuangneng CN-01), and was pressed into a sheet with a thickness of 1 mm at a pressure of 200 MPa or 350 MPa. The electrolyte sheet was tested by AC impedance spectroscopy. The electrolyte impedance was measured by electrochemical impedance spectroscopy (EIS). The impedance was measured on an electrochemical workstation (ChenHua, CHI630E) by applying a direct current (DC) polarization voltage of 1 V. The amplitude was 50 mV, and the frequency range was 1 Hz-10 MHz. The ion conductivity of the electrolyte material was calculated according to the following ion conductivity formula, as follows:

[0084]

[0085] wherein σ is the ion conductivity, unit S· cm –1 ; L is the thickness of the electrolyte sheet, unit cm; R is the impedance of the electrolyte, unit ; S is the effective contact area between the stainless steel sheet and the electrolyte powder, unit cm 2 .

[0086] X-ray powder diffraction test

[0087] X-ray powder diffraction (XRD) technique was used to analyze the crystal structure of the samples. A Bruker D8 Advance diffractometer equipped with Cu Kα radiation (λ = 1.5406 Å) was used as the light source. The test parameters were set as follows: tube voltage of 40 kV, tube current of 40 mA, scanning range of 2θ = 5°-90°, scanning step of 0.02°, and scanning rate of 5° / min. The sample was uniformly dispersed in the form of powder on a glass slide without diffraction background, and was treated by compaction to reduce the influence of inter-particle voids on the diffraction results.

[0088] The XRD data were processed and analyzed using Jade software. First, the raw data were imported into the software, and background subtraction and signal optimization were performed. The peak search function was used to automatically identify the diffraction peak positions, and a Gaussian function was selected for peak shape fitting. The parameters were adjusted to make the fitted curve consistent with the experimental data. After fitting, the software directly outputted the peak area I and half-width x of the diffraction peak, where the half-width represented the width at half the peak height, and the peak area represented the integral area of the diffraction peak with units of degrees (°).

[0089] Example 1-1

[0090] Li2S, P2S5 and LiCl were respectively pulverized using the Tianchuang powder QXQM-6 ball mill. After pulverization, the D50 of Li2S was 6.1 μm, the D50 of P2S5 was 6.5 μm, and the D50 of LiCl was 6.6 μm.

[0091] Under an Ar atmosphere, Li2S, P2S5 and LiCl with a molar ratio of 5:1:2 were weighed as the substrate, 1 kg of the above substrate corresponded to 0.5 L of n-hexane (substrate:solvent mass ratio = 3:1), and stirring was performed at a speed of 500 rpm for 30 min at room temperature and normal pressure to obtain a viscous solid mixture;

[0092] The mixture was placed at room temperature and normal pressure under an Ar atmosphere overnight to volatilize the solvent, and the volatilization rate of the solvent was controlled at 5 mg / cm 2 ·h, so that the residual amount of the solvent was maintained below 5 wt%, to obtain a solid electrolyte precursor mixture, and the X-ray diffraction pattern thereof is shown in Figure 6 The volatilization rate was controlled by using a large surface dish at room temperature and normal pressure, so that the dry specific surface area of each gram of sample was 1.51 cm 2 , and the sample thickness was 2.2 mm.

[0093] The solid-state electrolyte precursor mixture was heated at a temperature increasing rate of 3℃ / min to 200℃ for 3h to remove residual organic solvent; then heated at a temperature increasing rate of 7℃ / min to 550℃ for 10h. The sintered product was ground for 1h to obtain the sulfide solid-state electrolyte (Li6PS5Cl). The X-ray diffraction pattern thereof is shown in Figure 1 , Figure 4 is an enlarged view of the diffraction peak corresponding to the (111) crystal face in the Figure 1 is an enlarged view of the diffraction peak corresponding to the (311) crystal face in the Figure 5 is an enlarged view of the diffraction peak corresponding to the (111) crystal face in the Figure 1 is an enlarged view of the diffraction peak corresponding to the (311) crystal face in the

[0094] Example 1-2 to Example 1-3

[0095] The rest was the same as Example 1-1 except that the type of LiX was adjusted according to Table 1.

[0096] Example 1-4 to Example 1-5

[0097] The rest was the same as Example 1-1 except that the molar ratio of the substrate was adjusted according to Table 1. The X-ray diffraction pattern of the sulfide solid-state electrolyte of Example 1-4 is shown in Figure 2 .

[0098] Example 1-6

[0099] The rest was the same as Example 1-1 except that the type of LiX and the molar ratio of the substrate were adjusted according to Table 1.

[0100] Example 2-1 to Example 2-2

[0101] The rest was the same as Example 1-1 except that the mass ratio of the substrate to the solvent was adjusted according to Table 2.

[0102] Example 2-3 to Example 2-4

[0103] The rest was the same as Example 1-1 except that the first sintering temperature was adjusted according to Table 2.

[0104] Example 2-5 to Example 2-6

[0105] The rest was the same as Example 1-1 except that the first sintering time was adjusted according to Table 2.

[0106] Example 2-7 to Example 2-8

[0107] The rest was the same as Example 1-1 except that the second sintering temperature was adjusted according to Table 2. The X-ray diffraction pattern of the sulfide solid-state electrolyte of Example 2-7 is shown in Figure 3 .

[0108] Example 2-9 to Example 2-10

[0109] The rest was the same as Example 1-1 except that the second sintering time was adjusted according to Table 2.

[0110] Example 3-1 to Example 3-4

[0111] The rest was the same as Example 1-1 except that the D50 of the substrate was adjusted according to Table 3.

[0112] Example 4-1 to Example 4-6

[0113] The rest was the same as Example 1-1 except that the kind of solvent was adjusted according to Table 4.

[0114] Example 5-1 to Example 5-4

[0115] The rest was the same as Example 1-1 except that the first sintering heating rate was adjusted according to Table 5.

[0116] Example 5-5 to Example 5-8

[0117] The rest was the same as Example 1-1 except that the second sintering heating rate was adjusted according to Table 5.

[0118] Example 6-1 to Example 6-6

[0119] The rest was the same as Example 1-1 except that the stirring time was adjusted according to Table 6.

[0120] Example 7-1 to Example 7-2

[0121] The rest was the same as Example 1-1 except that the post-treatment method was adjusted according to Table 7.

[0122] Example 8-1

[0123] In an inert atmosphere, Li6PS5Cl prepared in Example 1-1 and Li2O with a specific mass ratio (99.9:0.01) were weighed and transferred into a ball milling jar, 0.5 mm zirconium beads were added (ball-to-material ratio was 2:1), after sealing the ball milling jar, the sample Li6PS5Cl@0.01Li2O was obtained by ball milling at 500 rpm for 6 h on Changsha Tianchuang Powder Planetary Ball Mill.

[0124] Example 8-2

[0125] The rest was the same as Example 8-1 except that the coating oxide was adjusted to SiO2 according to Table 9.

[0126] Comparative Example 2-1 to Comparative Example 2-2

[0127] The rest is the same as Example 1-1 except that the mass ratio of the substrate to the solvent is adjusted according to Table 2.

[0128] Comparative Example 2-3

[0129] The rest is the same as Example 1-1 except that the first sintering is not performed according to Table 2.

[0130] Comparative Example 2-4 to Comparative Example 2-5

[0131] The rest is the same as Example 1-1 except that the first sintering temperature and time are adjusted according to Table 2.

[0132] Comparative Example 2-6 to Comparative Example 2-7

[0133] The rest is the same as Example 1-1 except that the second sintering temperature and time are adjusted according to Table 2.

[0134] Comparative Example 2-8

[0135] The rest is the same as Example 1-1 except that the solvent is not added according to Table 2.

[0136] Comparative Example 4-1 to Comparative Example 4-3

[0137] The rest is the same as Example 1-1 except that the type of the solvent is adjusted according to Table 4.

[0138] Among them, when using ethanol as the solvent, due to the strong interaction between the substrate and the ethanol solvent, the substrate is dissolved and even forms a complex, so ethanol cannot be dried and cannot be used for subsequent experiments, and there is no relevant data.

[0139] Comparative Example 5-1

[0140] Use Example 2 in the publication text of patent application CN115621538A to do Comparative Example 5-1. The X-ray diffraction pattern of the electrolyte precursor powder is as shown in Figure 7 .

[0141] Comparative Example 5-2

[0142] The rest is the same as Example 1-1 except that the ball milling method is used when the substrate is mixed with the solvent. Among them, the zirconium ball is used, the ball-to-material ratio is 5:1, and the ball milling is performed at a speed of 300 rpm for 12 hours.

[0143] Comparative Example 5-3

[0144] The rest is the same as Example 1-1 except that the ultrasonic dispersion method is used when the substrate is mixed with the solvent. Among them, the ultrasonic treatment frequency is 1 time / 2h, the ultrasonic power is 800W, and the ultrasonic time is 5min / time.

[0145] Comparative Example 5-4

[0146] The rest was the same as Example 1-1 except that the suspension was vacuum dried at 60°C for 24 h instead of being left at room temperature under Ar atmosphere overnight.

[0147] The preparation and performance parameters of each example and comparative example are shown in Tables 1 to 9.

[0148] Table 1

[0149]

[0150] Table 2

[0151]

[0152] " / " in Table 2 means no relevant parameter.

[0153] Table 3

[0154]

[0155] Table 4

[0156]

[0157] " / " in Table 4 means no relevant parameter.

[0158] Table 5

[0159]

[0160] Table 6

[0161]

[0162] Table 7

[0163]

[0164] Table 8

[0165]

[0166] Table 9

[0167]

[0168] From Table 1, it can be seen that the molar ratio of the substrate is limited in the range of the present application, which can avoid the structure change of the sulfide solid electrolyte material and the decrease of the ionic conductivity. From Table 2, it can be seen that the mass ratio of the substrate and the solvent, the first sintering temperature and time, and the second sintering temperature and time are limited in the range of the present application, which can obtain a higher ionic conductivity; when the second sintering temperature is lower than the range of the present application, the substrate is not fully reacted, and the appropriate crystal face is not formed, so that I1 / I2 is large, thereby resulting in a lower ionic conductivity; and when the second sintering temperature is higher than the range of the present application, the product LPSC has a side reaction, resulting in the precipitation of LiX (such as LiCl), so that I1 / I2 is small, thereby resulting in the destruction of the overall structure of the product and the decrease of the ionic conductivity. From Table 3, it can be seen that the D50 of the substrate is controlled in the range of the present application, which is beneficial to the uniform diffusion and crystal nucleus distribution of the reaction, thereby providing a good foundation for the directional growth of the crystal, and I1 / I2 is in the range of the present application, thereby further improving the ionic conductivity of the sulfide solid electrolyte. From Table 4, it can be seen that the type of the solvent is in the range of the present application, which can effectively avoid the hydrolysis of the precursor and reduce the content of oxygen impurities (such as Li3PO4) in the sulfide solid electrolyte, thereby further improving the ionic conductivity of the sulfide solid electrolyte. From Table 5, it can be seen that the heating rate of the two sintering is in the range of the present application, which can make the solvent volatilization not introduce too many gaps in the sulfide solid electrolyte, and the crystal structure of the sulfide solid electrolyte is complete, and the ionic conductivity is high. From Table 6, it can be seen that the mechanical stirring is controlled at room temperature and atmospheric pressure, and the stirring speed is in the range of the present application, so that the substrates do not react with each other when mixed with the solvent, and the sulfide solid electrolyte with high ionic conductivity can be obtained. The stirring time is controlled in the range of the present application, which can make the substrates contact more fully, thereby obtaining the sulfide solid electrolyte with higher ionic conductivity. From Table 7, it can be seen that the post-processing method of the present application has high ionic conductivity. From Table 8, it can be seen that the sulfide solid electrolyte obtained by drying the solvent at room temperature and atmospheric pressure and mixing the substrates and the solvent by the stirring method of the present application has low porosity and high ionic conductivity; when the substrates and the solvent are mixed by ultrasonic dispersion or ball milling, the substrates partially react when mixed, resulting in the increase of the porosity of the sulfide solid electrolyte and the decrease of the ionic conductivity; when the solvent is dried by vacuum drying, the porosity of the sulfide solid electrolyte increases more obviously, and the ionic conductivity of the sulfide solid electrolyte decreases; when the substrates and the solvent are mixed by ultrasonic dispersion and the solvent is dried by vacuum drying, the porosity of the obtained sulfide solid electrolyte further increases, and the ionic conductivity further decreases. From Table 9, it can be seen that the sulfide solid electrolyte prepared in the present application is coated with an inert oxide layer on the surface, and the conductivity is not obviously reduced, but the addition of the oxide layer can well isolate the sulfide from the contact with the moisture in the air. From Figure 6 and Figure 7It can be seen that only the characteristic peaks of the substrate lithium sulfide and lithium chloride (P2S5 is in amorphous structure, and the diffraction peak intensity in XRD is very low and is masked) are shown in Example 1-1, while in Comparative Example 5-1, the relative intensity of the peaks of the substrate lithium sulfide and lithium chloride decreases, and the relative intensity of the intermediate Li3PS4 and the product LPSC increases, indicating that the reaction between the substrates has occurred at this time. Therefore, the mechanism of the patent application CN115621538A publication text is completely different from the mechanism of the present application. In addition, from Figures 1 to 3 It can be seen that the substrate ratio and the second sintering temperature will affect the ratio of sulfide solid electrolyte I1 / I2. From Figure 4 and Figure 5 It can be seen that the half peak width x1 of the (111) crystal plane of the sulfide solid electrolyte prepared in Example 1-1 is 0.137, and the half peak width x2 of the (311) crystal plane is 0.146.

[0169] In addition, since the first sintering only dries the solvent, and the reaction between the substrates to generate the sulfide solid electrolyte only starts in the second sintering, the first sintering temperature and time have less effect on the value of I1 / I2. It can also be seen from Examples 2-3, 2-4 and Comparative Examples 2-3 to 2-5 that whether the first sintering temperature and time are within the scope of the present application, the value of I1 / I2 changes little. The main effect is the volatilization of the solvent. When the first sintering temperature is too low or the time is too short, the solvent is not completely volatilized, which ultimately leads to a decrease in the ionic conductivity of the sulfide solid electrolyte.

[0170] In summary, the sulfide solid electrolyte has high ionic conductivity. Among them, the I1 / I2 of the sulfide solid electrolyte is within the scope of the present application, that is, the relative proportion of the main crystal face (111) and the crystal face (311) is moderate, which can realize the optimization of crystal orientation, effectively improve the lithium ion migration path in the material, help to maintain the mechanical strength and sintering density of the material, on the basis of ensuring the structural stability of the sulfide solid electrolyte, realize the improvement of ionic conductivity. Further, the preparation method of the present application controls the D50 of the substrate within the scope of the present application, which is beneficial to the uniform diffusion and crystal nucleus distribution of the reaction, thereby providing a good foundation for the directional growth of the crystal, and further improving the ionic conductivity of the sulfide solid electrolyte; the use of low-polarity and inert alkane solvents can inhibit the directional complexation reaction between the substrates, which is beneficial to the preferential growth of the (111) crystal face; controlling the mass ratio of the solvent to the substrate within the scope of the present application, the substrate particles are dispersed uniformly, which is helpful to control the nucleation position, thereby affecting the crystal growth direction; but too large dosage is easy to cause the disorder of the crystal face structure; by controlling the sintering temperature and time, the ionic conductivity and phase purity of the electrolyte are improved, and the overall performance of the electrolyte is also enhanced. Further, the battery containing the sulfide solid electrolyte of the present application or the sulfide solid electrolyte prepared by the preparation method of the present application has high safety and energy density and good low-temperature performance, and can be applied to electric vertical take-off and landing aircraft, such as low-altitude economic manned electric vertical take-off and landing aircraft.

[0171] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A sulfide solid-state electrolyte, characterized by, The chemical formula of the sulfide solid electrolyte is Li 7-a PS 6- a X a , X is halogen, 1≤a≤2; wherein, the peak area of the diffraction peak corresponding to the (111) crystal face of the sulfide solid electrolyte is I1, the peak area of the diffraction peak corresponding to the (311) crystal face of the sulfide solid electrolyte is I2, I1 and I2 satisfy: 0.2≤I1 / I2≤0.

3.

2. The sulfide solid-state electrolyte according to claim 1, characterized by, The half-peak width of the diffraction peak corresponding to the (111) crystal face of the sulfide solid-state electrolyte is x1, the half-peak width of the diffraction peak corresponding to the (311) crystal face of the sulfide solid-state electrolyte is x2, and x1 and x2 satisfy: 0.12 < x1 < 0.2, 0.14 < x2 < 0.

22.

3. The sulfide solid-state electrolyte of claim 1, wherein, The particle diameter of the sulfide solid electrolyte satisfies: 0.5 µm < D50 < 1 µm, 1.4 µm < D90 < 2 µm, 10 µm < D MAX < 15 µm.

4. The sulfide solid-state electrolyte of claim 1, wherein, The ionic conductivity of the sulfide solid-state electrolyte is ≥5.3 mS / cm.

5. The sulfide solid-state electrolyte of claim 1, wherein, 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, Hf, Y and Ru elements, which are introduced by doping or coating.

6. The sulfide solid-state electrolyte of claim 1, wherein, The surface of the sulfide solid-state electrolyte is coated with an inert oxide layer, and the inert oxide layer is selected from at least one of Li2O, Al2O3, V2O5, ZnO, ZrO2, TiO2, MgO, RuO2, La2O3, CeO2, HfO2, Y2O3, SiO2, B2O3, CuO, NbO2, LiNbO3, LiAlO2.

7. A preparation method of the sulfide solid-state electrolyte according to any one of claims 1 to 4, characterized in that, under the protection of an inert atmosphere, the substrate is mixed with a solvent and mechanically stirred to obtain a solid-state mixture; wherein the substrate comprises Li2S, P2S5 and LiX, X is halogen; the substrate and the solvent are respectively crushed to 3 µm ≤ D50 ≤ 10 µm before being mixed; the molar ratio of the Li2S to the P2S5 is (3-5):1; the molar ratio of the P2S5 to the LiX is 1:(2-4); the mass ratio of the solvent to the substrate is 1:(1.5-3); the solid-state mixture is left to stand at normal temperature and pressure to volatilize the solvent, to obtain a solid-state electrolyte precursor mixture; the solid-state electrolyte precursor mixture is sintered to obtain a sulfide solid-state electrolyte; wherein the sintering comprises first sintering and second sintering, the temperature of the first sintering is 150-300 ℃, and the time is 1-6 h; the temperature of the second sintering is 450-600 ℃, and the time is 10-15 h.

8. The preparation method according to claim 7, characterized in that, The substrate and the solvent are respectively crushed to 5 µm ≤ D50 ≤ 8 µm before being mixed.

9. The preparation method according to claim 7, characterized in that, The temperature of the first sintering is 200-300 ℃, and the time is 3-6 h; the temperature of the second sintering is 550-600 ℃, and the time is 10-13 h.

10. The production method according to claim 7, wherein The heating rate of the first sintering is 2-5 ℃ / min; the heating rate of the second sintering is 5-10 ℃ / min.

11. The preparation method according to claim 7, characterized in that, The solvent is selected from at least one of n-hexane, benzene, toluene, cyclohexane, n-pentane, cyclopentane and dimethyl carbonate.

12. The method of claim 7, wherein, The mechanical stirring is carried out at normal temperature and pressure, the rotating speed of the mechanical stirring is 300 rpm-600 rpm, and the time of the mechanical stirring is 10-50 min.

13. The preparation method according to claim 7, characterized in that, The rate of solvent evaporation is 1.5 to 7.0 mg / cm 2 • h.

14. The preparation method according to claim 7, characterized in that, The sintering is followed by post-treatment, and the post-treatment comprises crushing.

15. A battery comprising a positive electrode sheet, a negative electrode sheet, and the sulfide solid electrolyte of any one of claims 1 to 6.

16. Use of the battery according to claim 15 in an electric vertical take-off and landing aircraft.

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