Li4snS4, method for preparing the same, and use thereof

Abstract

The application provides Li4SnS4 and a preparation method and application thereof, and particularly relates to the technical field of solid-state electrolyte. The preparation method comprises the following steps: uniformly mixing a lithium source, a tin source and a sulfur source according to a molar ratio, adding a solvent, and then placing the mixture in a closed container to perform a solvothermal reaction; after the reaction is completed, sequentially performing drying and heat treatment to obtain Li4SnS4; and the mass-volume ratio of the raw materials and the solvent is greater than or equal to 0.067 g / mL. By controlling the mass-volume ratio of the raw materials and the solvent to be greater than or equal to 0.067 g / mL, it is ensured that the reactants in the solvothermal system have sufficient local concentration and ionic strength, so as to significantly promote the effective mass transfer, coordination and in-situ nucleation of the precursor in the liquid phase, and after heat treatment, the Li4SnS4 phase with high crystallinity, small and uniform crystal grains and few grain boundary impurities is obtained, and the ionic conductivity of the product is improved. The preparation method has high efficiency, high controllability and high scalability, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte technology, and in particular to a Li4SnS4, its preparation method, and its applications. Background Technology

[0002] Solid-state electrolytes are the core materials for achieving high energy density, high safety, and long cycle life in all-solid-state lithium metal batteries. Among them, sulfide-based solid-state electrolytes such as Li4SnS4 have attracted widespread attention due to their high room-temperature ionic conductivity, good interfacial wettability, and relatively mild synthesis conditions.

[0003] Currently, the mainstream preparation method for Li4SnS4 is the mechanochemical method. Although this method can obtain products with a certain degree of crystallinity, it has the following inherent technical limitations: 1. Severe limitation on single-batch loading: To ensure sufficient collision space for the grinding balls within the jar to transfer effective mechanical energy, the actual filling rate of the ball mill jar must typically be controlled below 30%. The maximum safe loading capacity for a single batch in a conventional planetary ball mill generally does not exceed 5 g. This limitation results in extremely low efficiency in large-scale production, making it difficult to meet the urgent demand of the battery industry for kilogram-level or even ton-level solid electrolyte materials.

[0004] 2. Long reaction cycle and high energy consumption: The ball milling time can be several hours to tens of hours, and it requires high-power ball milling equipment and cooling system, which significantly increases manufacturing costs and energy consumption.

[0005] 3. Product uniformity and purity are questionable: During the high-energy ball milling process, the zirconium oxide grinding balls inevitably experience minor wear, introducing heterogeneous impurities such as ZrO2. These impurities may become preferential channels for lithium dendrite growth, deteriorating the cycle stability and critical current density of all-solid-state batteries.

[0006] In view of this, the present invention is hereby proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a Li4SnS4, its preparation method, and its application, aiming to solve at least one of the above-mentioned technical problems.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: The first aspect of this invention provides a method for preparing Li4SnS4, wherein a lithium source, a tin source and a sulfur source are mixed uniformly in a molar ratio, a solvent is added and the mixture is placed in a sealed container for a solvothermal reaction; after the reaction is completed, the mixture is dried and heat-treated sequentially to obtain Li4SnS4; wherein the mass-volume ratio of the raw materials to the solvent is ≥0.067 g / mL.

[0009] Furthermore, the mass-to-volume ratio of the raw material to the solvent is ≤0.667 g / mL.

[0010] Furthermore, the mass-to-volume ratio of the raw material to the solvent is 0.100~0.233 g / mL.

[0011] Furthermore, the temperature of the solvothermal reaction is ≥100℃, and the time is 2~5h.

[0012] Furthermore, the drying process is vacuum drying.

[0013] Preferably, the vacuum drying temperature is 120~180℃ and the time is 1~3h.

[0014] Furthermore, the heat treatment temperature is 250~300℃ and the time is 20~90min.

[0015] Furthermore, the solvent includes water.

[0016] The second aspect of the present invention provides a Li4SnS4 prepared by the preparation method described in the first aspect.

[0017] Furthermore, the ionic conductivity of the Li4SnS4 is ≥8.4×10⁻⁶. -5 S / cm.

[0018] The third aspect of the present invention provides the application of the aforementioned Li4SnS4 in solid-state batteries.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects: The preparation method provided by this invention, by controlling the mass-to-volume ratio of raw materials to solvent at ≥0.067 g / mL, ensures sufficient local concentration and ionic strength of reactants in the solvothermal system, thereby significantly promoting Li + Sn 4+ With S 2- The precursor achieves efficient mass transfer, coordination, and in-situ nucleation in the liquid phase. After heat treatment, a Li4SnS4 phase with high crystallinity, fine and uniform grains, and few grain boundary impurities is obtained, which improves the ionic conductivity of the product. This preparation method has high efficiency, high controllability, and high scalability, making it suitable for industrial production.

[0020] The Li4SnS4 provided by this invention has better ionic conductivity due to the advantages of the above preparation method, which is beneficial to improving the energy density, rate performance and cycle stability of solid-state batteries using it. Detailed Implementation

[0021] The embodiments and examples of the present invention will be described in detail below with reference to the implementation methods and examples. However, those skilled in the art will understand that the following implementation methods and examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The first aspect of this invention provides a method for preparing Li4SnS4, wherein a lithium source, a tin source and a sulfur source are mixed uniformly in a molar ratio, a solvent is added and the mixture is placed in a sealed container for a solvothermal reaction; after the reaction is completed, the mixture is dried and heat-treated sequentially to obtain Li4SnS4; wherein the mass-volume ratio of the raw materials to the solvent is ≥0.067 g / mL.

[0023] The preparation method provided by this invention, by controlling the mass-to-volume ratio of raw materials to solvent at ≥0.067 g / mL, ensures sufficient local concentration and ionic strength of reactants in the solvothermal system, thereby significantly promoting Li + Sn 4+ With S 2- The precursor achieves efficient mass transfer, coordination, and in-situ nucleation in the liquid phase. After heat treatment, a Li4SnS4 phase with high crystallinity, fine and uniform grains, and few grain boundary impurities is obtained, which improves the ionic conductivity of the product. This preparation method has high efficiency, high controllability, and high scalability, making it suitable for industrial production.

[0024] A mass-to-volume ratio of raw materials to solvent ≥0.067 g / mL ensures sufficient local reactant concentration and ionic strength in the solvothermal system, thereby effectively promoting liquid-phase mass transfer, coordination complexation, and in-situ nucleation of the precursor. This lays a key foundation for obtaining a Li4SnS4 phase with high crystallinity, fine and uniform grains, and low grain boundary impurities.

[0025] In embodiments of the present invention, the lithium source is Li₂S, the tin source is metallic tin, and the sulfur source is solid sulfur. Li₂S provides both lithium and... + Also provides S 2- This avoids the introduction of inactive cationic impurities; metallic Sn can be oxidized in situ to Sn in a reducing solvothermal environment (especially in water or systems containing H2O). 4+ and with Li + S 2- / HS - The coordination-condensation reaction is conducive to the formation of the target crystalline phase Li4SnS4; while the addition of elemental sulfur is used to precisely compensate for possible sulfur loss during the reaction (such as H2S volatilization), regulate the sulfur chemical potential, and ensure that sulfur is in excess to suppress the formation of impurity phases such as low-valence oxides / sulfides of Sn, thereby improving the purity and crystal integrity of the Li4SnS4 phase.

[0026] Furthermore, the mass-to-volume ratio of the raw material to the solvent is ≤0.667 g / mL, which can avoid insufficient solvation, hindered mass transfer, local overheating or precipitation agglomeration caused by excessive solid content, ensuring the uniformity and operability of the reaction system, and maintaining the controllability, repeatability and feasibility of large-scale scale-up of the solvothermal process.

[0027] Furthermore, the mass-to-volume ratio of the raw material to the solvent is 0.100~0.233 g / mL.

[0028] Typically, but not limitingly, the mass-to-volume ratio of the raw material to the solvent can be, for example, 0.100 g / mL, 0.130 g / mL, 0.160 g / mL, 0.190 g / mL, 0.220 g / mL, or 0.233 g / mL, or any value within the range of 0.100 to 0.233 g / mL.

[0029] Furthermore, the solvothermal reaction is carried out at a temperature ≥100℃ for 2~5 hours. A temperature ≥100℃ ensures that water or other polar solvents are in a subcritical or near-critical state, significantly improving the efficiency of Li. + Sn 4+ The solubility and mobility of the precursor promote homogeneous coordination complexation and accelerate in-situ nucleation; while a moderate reaction time of 2-5 h is sufficient to complete the formation of crystal nuclei and the initial crystal growth, and can avoid excessive growth time leading to abnormal grain growth, agglomeration or side reactions.

[0030] If the solvothermal reaction temperature is below 100℃, it will lead to severely insufficient precursor solubility and ion mobility, sluggish coordination kinetics, and excessively high nucleation energy barriers, resulting in insufficient Li in the reaction system. + Sn 4+ Sulfur species are unable to form effective solvated complexes and active intermediates, significantly inhibiting mass transfer, coordination, and homogeneous nucleation processes in the liquid phase. As a result, the precursors are not fully converted, the products are mainly amorphous or low-crystallinity impurities, the grain size distribution is wide, and the grain boundary defects are dense. Finally, the Li4SnS4 phase obtained after heat treatment has low purity, large lattice distortion, and discontinuous lithium ion migration channels, which directly leads to a significant decrease in ionic conductivity.

[0031] Furthermore, the drying process is vacuum drying.

[0032] Preferably, the vacuum drying temperature is 120~180℃, and the time is 1~3h. This method thoroughly removes the solvent and volatile byproducts while minimizing precursor decomposition and premature crystal precipitation. This temperature range is higher than the boiling points of water and common solvents, ensuring efficient and uniform solvent removal. It is also much lower than the crystal phase transformation initiation temperature of Li4SnS4, avoiding uncontrollable solid-phase reactions or sulfur loss during the drying stage. The 1-3h duration takes into account the solvent removal kinetics. The vacuum environment further prevents low-valent tin or sulfides from being oxidized by O2 in the air to form SnO2 and SO4. 2- The presence of electrochemically inert impurities ensures the chemical purity and reducibility of the precursor, laying a clean, stable, and structurally controllable precursor foundation for subsequent precise heat treatment to obtain Li4SnS4 with high crystallinity, low defects, and high phase purity.

[0033] Typically, but not limitingly, the vacuum drying temperature can be, for example, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, or 180°C, or any value within the range of 120°C to 180°C; the vacuum drying time can be, for example, 1h, 1.5h, 2h, 2.5h, or 3h, or any value within the range of 1h to 3h.

[0034] Furthermore, the heat treatment temperature is 250~300℃, and the time is 20~90min. The dried precursor mainly undergoes solid-phase rearrangement and crystal phase densification reactions, structural ordering transformation of amorphous sulfides into crystalline Li4SnS4, and grain interface fusion and defect annealing. This temperature range matches the crystallization initiation temperature and decomposition threshold of Li4SnS4, which can drive complete crystal phase transformation, improve crystallinity and lattice integrity, and avoid lithium loss, sulfur escape or secondary phase formation caused by high temperature. The short heat treatment of 20~90min inhibits excessive grain growth, maintains fine and uniform grain size from nanometer to submicron, significantly increases the number of beneficial grain boundaries, facilitates rapid lithium ion conduction along grain boundaries, reduces energy consumption, improves process controllability and batch consistency, and ultimately achieves high ionic conductivity, excellent electrochemical stability and feasibility of large-scale preparation.

[0035] Typically, but not limitingly, the temperature of the heat treatment can be, for example, 250°C, 260°C, 270°C, 280°C, 290°C, or 300°C, or any value within the range of 250°C to 300°C; the time of the heat treatment can be, for example, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 60 min, 70 min, 80 min, or 90 min, or any value within the range of 20 to 90 min.

[0036] Without heat treatment, the precursor will not complete the crystal phase transformation and structural densification, resulting in low crystallinity of the product, insufficient content of Li4SnS4 main phase, and a large amount of amorphous sulfides or intermediate phases remaining at the grain boundaries. This significantly reduces ionic conductivity and deteriorates electrochemical stability and battery cycle performance.

[0037] Furthermore, the solvent includes water.

[0038] In some embodiments of the present invention, water is preferred as the solvent. Its advantages lie not only in its low cost, environmental friendliness, and operational safety, but more importantly, in its high volatility and zero carbon residue. Water can be thoroughly and cleanly removed during the vacuum drying stage without introducing any carbon source impurities during subsequent heat treatment. In contrast, if organic solvents are used, even after thorough drying, carbon-containing components may remain in the precursor due to high boiling points, poor polarity matching, or condensation / decomposition reactions. These carbon residues are difficult to completely remove during heat treatment and will transform into free carbon, carbides, or graphitized microdomains, significantly increasing the electronic conductivity of the product and destroying the ionic conductivity necessary for solid-state electrolytes. This leads to problems such as accelerated lithium dendrite growth, intensified interfacial side reactions, and battery self-discharge, severely restricting its practical application in all-solid-state lithium batteries.

[0039] The second aspect of the present invention provides a Li4SnS4 prepared by the preparation method described in the first aspect.

[0040] The Li4SnS4 provided by this invention has better ionic conductivity due to the advantages of the above preparation method, which is beneficial to improving the energy density, rate performance and cycle stability of solid-state batteries using it.

[0041] Li4SnS4 is a thio-LISICON configuration sulfide solid electrolyte material, with crystals in a tetrahedral configuration [SnS4]. 4- As the structural unit, lithium ions are arranged in the interstices of the lattice to achieve ion conduction. The material has two crystal forms: a stable hexagonal phase at room temperature and an orthorhombic phase at high temperature.

[0042] On the one hand, the material does not undergo violent hydrolysis in pure water, which allows the hydrothermal reaction system to maintain the coordination activity of the precursor and the uniformity of the reaction; on the other hand, it forms a transparent true solution after dissolution, which supports precise control of the precursor morphology and composition uniformity through low-temperature crystallization / drying, and is compatible with downstream electrode processing technologies such as aqueous slurry coating.

[0043] On the other hand, the solid-liquid ratio control constructed in this invention ensures sufficient ionic strength in the aqueous phase to drive [SnS4]. 4- Complexation with Li +The orderly arrangement and the mild heat treatment temperature window not only achieve the directional growth of high crystallinity of the hexagonal phase, but also avoid destroying the reversibility of hydration-dehydration and triggering reduction side reactions such as Sn or Li2S precipitation; while avoiding organic solvents and high-temperature carbonization throughout the process, the risk of increased electronic conductivity is eliminated from the source, effectively maintaining its electrolyte properties of high ionic conductivity / low electronic conductivity.

[0044] Furthermore, the ionic conductivity of the Li4SnS4 is ≥8.4×10⁻⁶. -5 S / cm.

[0045] The third aspect of the present invention provides the application of the aforementioned Li4SnS4 in solid-state batteries.

[0046] Li4SnS4 is a sulfide solid electrolyte specifically designed for all-solid-state lithium batteries. It is used to replace traditional liquid electrolytes to achieve lithium-ion conduction. Relying on its unique advantages of being soluble in water and having excellent air stability, it differs from conventional sulfide electrolytes that are easily decomposed and produce gas when exposed to water. It can be used to complete the preparation of the entire battery using an aqueous wet process.

[0047] In actual use, there are three main application scenarios: 1. Independent preparation of membrane layer: The powder can be dry-pressed into dense electrolyte sheet under high pressure, or it can be mixed with water and a small amount of water-based binder to form a slurry and directly coated into a continuous electrolyte film. No strict ultra-high dew point glove box is required. The film can be mass-produced in a normal low dew point drying room.

[0048] 2. Composite electrodes are made by incorporating positive and negative electrode active materials. Li4SnS4 powder, ternary positive / graphite negative electrode active materials and conductive agents are mixed in a fixed ratio and coated on aluminum foil and copper foil current collectors with water-based slurry. The electrolyte is uniformly dispersed in the gaps between active particles, forming a continuous lithium-ion transport pathway, improving solid-solid interface contact and reducing interface impedance.

[0049] 3. Used as an electrode surface coating modification material, Li4SnS4 is coated in a thin layer on the surface of graphite or silicon-based negative electrode particles to isolate the side reactions between the active material and the main electrolyte and optimize the interface stability.

[0050] To further improve room temperature ionic conductivity, lithium iodide and phosphorus sulfide are often added during production for composite modification. The modified powder is then processed using the same film-forming and mixing process. In the cell assembly stage, the composite positive electrode, Li4SnS4 electrolyte membrane, and lithium metal or graphite negative electrode are stacked in that order and then tightly bonded by appropriate hot pressing. Lithium ions migrate back and forth through the gaps in the Li4SnS4 lattice, and the resulting lithium metal all-solid-state soft pack or button battery is assembled. These batteries are mainly used in the research and development of energy storage and automotive solid-state batteries.

[0051] The present invention is further illustrated below with specific embodiments and comparative examples. However, it should be understood that these embodiments are merely for illustrative purposes and should not be construed as limiting the invention in any way. Unless otherwise specified, the raw materials used in the embodiments and comparative examples of the present invention were carried out under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0052] Example 1 This embodiment provides a Li4SnS4 preparation method as follows: Raw materials (molar ratio of Li2S:Sn:S = 2:1:2) are added to a high-pressure resistant container lined with PTFE. The total weight of the raw material powder is 2g. 30mL of water and a stir bar are added, and the container is sealed. The mixture is stirred in the high-pressure resistant container and heated at 150℃ for 3 hours to obtain a solution. The solution is then vacuum dried at 160℃ for 2 hours to obtain a precursor powder. Under an inert atmosphere, the precursor powder is heated to 280℃ within 0.5 hours and sintered at 280℃ for 0.5 hours to obtain the solid electrolyte Li4SnS4 powder.

[0053] Example 2 This embodiment provides a Li4SnS4, which differs from Embodiment 1 in that the total weight of the raw material powder is 3g. The other raw materials and preparation methods are the same as in Embodiment 1, and will not be repeated here.

[0054] Example 3 This embodiment provides a Li4SnS4, which differs from Embodiment 1 in that the total weight of the raw material powder is 7g. The other raw materials and preparation methods are the same as in Embodiment 1, and will not be repeated here.

[0055] Example 4 This embodiment provides a Li4SnS4, which differs from Embodiment 1 in that the total weight of the raw material powder is 10g. The other raw materials and preparation methods are the same as in Embodiment 1, and will not be repeated here.

[0056] Example 5 This embodiment provides a Li4SnS4, which differs from Embodiment 1 in that the total weight of the raw material powder is 15g. The other raw materials and preparation methods are the same as in Embodiment 1, and will not be repeated here.

[0057] Example 6 This embodiment provides a Li4SnS4, which differs from Embodiment 1 in that the total weight of the raw material powder is 20g. The other raw materials and preparation methods are the same as in Embodiment 1, and will not be repeated here.

[0058] Example 7 This embodiment provides a Li4SnS4, which differs from Embodiment 1 in that the total weight of the raw material powder is 21g. The other raw materials and preparation methods are the same as in Embodiment 1, and will not be repeated here.

[0059] Example 8 This embodiment provides a Li4SnS4, which differs from Example 1 in that the hydrothermal reaction temperature is 100°C. The other raw materials and preparation methods are the same as in Example 1, and will not be repeated here.

[0060] Example 9 This embodiment provides a Li4SnS4, which differs from Example 1 in that the hydrothermal reaction temperature is 80°C. The other raw materials and preparation methods are the same as in Example 1, and will not be repeated here.

[0061] Comparative Example 1 This comparative example provides a Li4SnS4 preparation method as follows: Raw materials (molar ratio of Li2S:Sn:S = 2:1:2) are added to a high-pressure resistant container lined with PTFE. The total weight of the raw material powder is 1g. 25mL of water and a stir bar are added, and the container is sealed. The mixture is stirred in the high-pressure resistant container and heated at 150℃ for 3 hours to obtain a solution. The solution is then vacuum dried at 150℃ for 3 hours to obtain a precursor powder. Under an argon atmosphere, the precursor powder is heated to 250℃ within 0.5 hours and sintered at 250℃ for 1 hour to obtain the solid electrolyte Li4SnS4 powder.

[0062] Comparative Example 2 This comparative example provides a Li4SnS4, which differs from Example 1 in that the total weight of the raw material powder is 1.2g. The other raw materials and preparation methods are the same as in Example 1, and will not be repeated here.

[0063] Comparative Example 3 This comparative example provides a Li4SnS4, which differs from Example 1 in that the total weight of the raw material powder is 0.5g, the vacuum drying time is 3h, and the remaining raw materials and preparation methods are the same as in Example 1, and will not be repeated here.

[0064] Comparative Example 4 This comparative example provides a Li4SnS4 precursor powder, prepared as follows: Raw materials (molar ratio Li2S:Sn:S = 2:1:2) were weighed and mixed in an argon-atmospheric glove box. Subsequently, the mixture was mechanically ground in a ball mill at 510 rpm for 10 hours using a 45 mL zirconia ball mill jar containing 90 g (approximately 500) zirconia balls with a diameter of 4 mm, to obtain Li4SnS4 precursor powder. The Li4SnS4 precursor powder was then heat-treated at 390 °C for 2 hours to obtain Li4SnS4 powder.

[0065] Comparative Example 5 This comparative example provides a Li4SnS4, which differs from Example 2 in that no heat treatment process is performed. The other raw materials and preparation methods are the same as in Example 2, and will not be repeated here.

[0066] Test Example 1: [Ionic Conductivity Measurement] The solid electrolytes obtained in the examples and comparative examples were used to prepare circular pellets with a diameter of 10 mm (resulting in a cross-sectional area S) and a height (L) of 5 cm as samples. Electrode terminals were connected to both sides of the sample, and AC impedance spectroscopy was performed at 25°C and a pressure of 690 MPa (frequency 0.1 Hz to 1 MHz, amplitude 10 mV) to obtain the Cole-Cole curve. The real part Z'(Ω) near the right end of the arc observed in the high-frequency region, where -Z''(Ω) is the minimum point, was taken as the bulk resistance R(Ω) of the electrolyte, and the ionic conductivity σ(S / cm) was calculated according to the following formula.

[0067] R = ρ(L / S); σ = 1 / ρ.

[0068] The ionic conductivity data are summarized in Table 1.

[0069] Table 1

[0070] As can be seen from Table 1, Examples 1-3 yielded high ionic conductivity, with Example 2 reaching a peak value of 1.3 × 10⁻⁶. -4 The S / cm concentration is significantly better than that of the other examples and all comparative examples. Comparative examples 1-3 show that excessively low concentrations severely impair electrical conductivity, with a clear downward trend in conductivity; in particular, the conductivity of comparative example 3 is less than 1 / 4 of the optimal value. It can be seen that excessively low solid content leads to insufficient precursor concentration, low nucleation density, and insufficient grain growth, which easily forms a large number of amorphous phases or defect grain boundaries, hindering long-range lithium-ion transport.

[0071] When the mass-to-volume ratio exceeds 0.233 g / mL, the conductivity begins to decrease: 8.6 × 10⁻⁶ in Example 4. -5 S / cm, in Example 5, increased to 9.9 × 10 -5 S / cm, but in Examples 6 and 7 the value remained stable at 8.2-8.4×10. -5 The S / cm value is lower than the baseline value in Example 1. Excessive solid content weakens solvation ability, exacerbates local concentration differences and precipitate aggregation, disrupts reaction uniformity, leads to grain coarsening and increased grain boundary impurities, and conversely inhibits ion conduction.

[0072] Comparative Example 4 has a conductivity of only 4.8 × 10⁻⁶. -5The conductivity (S / cm) is significantly lower than that of the optimal solvothermal sample, confirming the substantial progress of the method in suppressing ZrO2 impurities and improving phase purity and microstructure uniformity; while the conductivity of Comparative Example 5 drops sharply to 9.43 × 10⁻⁶. -6 The S / cm ratio indicates the crucial role of heat treatment in the complete transformation of the crystal phase and the densification of the structure.

[0073] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing Li4SnS4, characterized in that, Lithium source, tin source and sulfur source were mixed evenly in a molar ratio, and after adding solvent, the mixture was placed in a sealed container for a solvothermal reaction. After the reaction was completed, the mixture was dried and heat-treated to obtain Li4SnS4. The mass-to-volume ratio of raw materials to solvent is ≥0.067 g / mL.

2. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of the raw material to the solvent is ≤0.667 g / mL.

3. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of the raw material to the solvent is 0.100~0.233 g / mL.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The temperature of the solvothermal reaction is ≥100℃, and the time is 2~5h.

5. The preparation method according to any one of claims 1 to 3, characterized in that, The drying process is vacuum drying; Preferably, the vacuum drying temperature is 120~180℃ and the time is 1~3h.

6. The preparation method according to any one of claims 1 to 3, characterized in that, The heat treatment temperature is 250~300℃ and the time is 20~90min.

7. The preparation method according to any one of claims 1 to 3, characterized in that, The solvent includes water.

8. A Li4SnS4, characterized in that, It is prepared by the preparation method according to any one of claims 1 to 7.

9. The Li4SnS4 according to claim 8, characterized in that, Ionic conductivity ≥ 8.4 × 10 -5 S / cm.

10. The application of Li4SnS4 as described in claim 8 or 9 in a solid-state battery.

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