A method for the preparation of a sulfide material for solid state electrolytes

Abstract

This invention discloses a method for preparing sulfide materials for solid electrolytes, belonging to the technical field of solid electrolyte materials. The invention uses anhydrous LiOH solid as the lithium source, hydrogen sulfide gas as the sulfur source, and aprotic aromatic solvents and / or hydrogenated aromatic solvents as the reaction medium to carry out a gas-solid heterogeneous acid-base reaction, thereby obtaining sulfide materials for solid electrolytes. This invention utilizes the proton inertness and chemical stability of aprotic or hydrogenated aromatic solvents to suppress side reactions at the source; it constructs a controllable three-phase reaction interface by leveraging their low solubility for LiOH and moderate solubility for H2S; it achieves in-situ dehydration using high boiling point characteristics, promoting complete reaction and preventing Li2S hydrolysis; and it promotes uniform nucleation and inhibits hard agglomeration through surface tension regulation and solvent barrier effects, thereby obtaining high-purity, uniformly sized nanoscale sulfide materials.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte materials technology, and more specifically to a method for preparing sulfide materials for solid electrolytes. Background Technology

[0002] With the rapid development of electric vehicles and the large-scale energy storage market, higher demands are being placed on the energy density, safety, and cycle life of lithium batteries. Traditional lithium-ion batteries use organic liquid electrolytes, which pose safety hazards such as flammability and leakage, and their energy density is already close to its theoretical limit. All-solid-state lithium batteries use non-flammable inorganic solid electrolytes to replace liquid electrolytes and are considered an ideal choice for the next generation of high-safety, high-energy-density energy storage systems.

[0003] Among numerous solid electrolyte materials, sulfide solid electrolytes, especially systems based on Li₂S (such as Li₂S-P₂S₅ glass-ceramics, ... 10 GeP2S 12 (etc.), because it has extremely high ionic conductivity (up to 10). -2 High-performance sulfide electrolytes, characterized by conductivity on the order of S / cm (approaching or even exceeding that of liquid electrolytes) and good mechanical ductility, have become a research hotspot. However, the preparation of such high-performance sulfide electrolytes typically requires high-purity lithium sulfide (Li₂S) as a key starting material. The purity, crystallinity, particle morphology, and oxygen content of lithium sulfide directly determine the ionic conductivity, electrochemical stability, and interfacial compatibility with the electrodes of the final solid-state electrolyte.

[0004] Currently, the preparation of industrial-grade or reagent-grade lithium sulfide mainly relies on the high-temperature sulfidation reduction process of lithium carbonate (Li₂CO₃). This method typically involves reacting lithium carbonate with a sulfiding agent (such as carbon disulfide, hydrogen sulfide, or a mixture of sulfur and reducing gases) in a high-temperature reactor (usually 800℃~1200℃) for an extended period. The core reaction principle is Li₂CO₃ + H₂S → Li₂S + H₂O + CO₂. However, this preparation process has numerous drawbacks. Not only are the reaction temperatures extremely high and energy consumption enormous, but the high temperatures also place stringent requirements on the corrosion resistance of the reactor. The reaction process generates large amounts of corrosive waste gases containing sulfur and carbon (such as CS₂, H₂S, SO₂, CO₂, etc.), which are environmentally unfriendly and have high costs for exhaust gas treatment. The high temperatures also cause severe sintering and agglomeration of the product, resulting in coarse and unevenly distributed particle sizes (typically tens to hundreds of micrometers). Large, low-activity lithium sulfide particles are difficult to mix at the atomic level when subjected to subsequent mechanical alloying or heat treatment with other raw materials such as P2S5 and GeS5. This often requires higher energy input or longer processing times, and the uniformity and performance consistency of the final electrolyte are difficult to guarantee. In addition, under high-temperature processes, trace amounts of oxygen or water in the raw materials, atmosphere, or equipment can easily lead to the formation of oxygen-containing impurities (such as Li2O, LiOH, etc.) that are difficult to remove. These impurities, acting as ion insulators, will severely degrade the ion conductivity of the final solid electrolyte.

[0005] Currently, existing technology discloses a method for preparing lithium sulfide, which involves dispersing lithium hydride (LiH) powder in anhydrous tetrahydrofuran (THF) or diethyl ether as an aprotic solvent to form a suspension under an inert atmosphere. The reaction temperature is controlled within the range of 0℃ to 50℃, and dry hydrogen sulfide (H2S) gas is continuously introduced into the suspension to carry out the reaction. After the reaction is completed, the reaction mixture is filtered and washed, and finally dried under vacuum or an inert atmosphere to obtain lithium sulfide (Li2S) powder.

[0006] However, the LiH used in the above preparation methods is an expensive fine chemical (far more expensive than basic lithium salts such as lithium carbonate), and its chemical properties are extremely reactive. It reacts violently with moisture to produce flammable hydrogen gas, requiring extremely stringent dryness requirements for the production, storage, and operating environments, significantly increasing the safety risks and costs of industrial scale-up. The trace amounts of lithium oxide (Li2O) impurities typically present in the LiH raw materials are difficult to remove during the reaction and are directly introduced into the final product, resulting in high oxygen content and poor purity in the lithium sulfide product. In aprotic solvents such as anhydrous tetrahydrofuran (THF) or diethyl ether, the nucleation and growth of lithium sulfide are difficult to precisely control, and the product is prone to uncontrolled agglomeration, resulting in large particles, wide particle size distribution, and limited specific surface area, making it difficult to obtain highly reactive nano- or submicron-sized uniform particles. In summary, existing methods for preparing lithium sulfide materials generally suffer from high raw material costs, poor product purity, and large and non-uniform particle sizes, leading to poor ion conductivity of the final solid electrolyte. Summary of the Invention

[0007] This invention provides a method for preparing sulfide materials for solid electrolytes, effectively solving the technical problems of high cost, poor product purity, and poor ionic conductivity of solid electrolytes due to non-uniform particle size in existing lithium sulfide material preparation methods. At the same time, it provides a method for preparing lithium sulfide with mild process, safe and controllable process, environmental friendliness, and the ability to directly obtain high-purity, nano-sized fine particles, thereby greatly reducing the manufacturing cost of high-performance sulfide solid electrolytes and improving the electrochemical performance of solid electrolytes.

[0008] The first objective of this invention is to provide a method for preparing a sulfide material for a solid electrolyte, comprising the following steps: Using anhydrous LiOH solid as the lithium source, hydrogen sulfide gas as the sulfur source, and aprotic aromatic solvent and / or hydrogenated aromatic solvent as the reaction medium, a gas-solid heterogeneous acid-base reaction was carried out at 100℃~200℃ under vacuum and a protective atmosphere to obtain sulfide materials for solid electrolytes.

[0009] The aprotic aromatic solvent is at least one of toluene, p-xylene, and ethylbenzene, and toluene cannot be used alone as a reaction medium; the hydrogenated aromatic solvent is at least one of tetrahydronaphthalene, decahydronaphthalene, dodecane, and hexadecane.

[0010] The reaction medium selected in this invention is aprotic, meaning it does not undergo proton exchange reactions with LiOH or the generated Li₂S, thus avoiding side reactions. It possesses suitable polarity and solubility, exhibiting some solubility for H₂S, which is beneficial for gas-liquid mass transfer; its extremely low solubility for LiOH allows it to be dispersed primarily in solid particle form, facilitating control over the reaction process and product morphology. It is chemically stable, remaining stable under the reaction conditions and not reacting chemically with the reactants or products. It has a suitable boiling point, typically between 100℃ and 200℃, facilitating reaction at appropriate temperatures and subsequent solvent recovery.

[0011] In a preferred embodiment, the reaction medium is an aprotic aromatic solvent, and the aprotic aromatic solvent is p-xylene and / or ethylbenzene.

[0012] In a preferred embodiment, the reaction medium is a mixture of aprotic aromatic solvent and hydrogenated aromatic solvent, wherein the aprotic aromatic solvent is at least one of toluene, p-xylene, and ethylbenzene, and the hydrogenated aromatic solvent is at least one of tetrahydronaphthalene, decahydronaphthalene, dodecane, and hexadecane; the volume ratio of the aprotic aromatic solvent to the hydrogenated aromatic solvent is 1:1 to 9.

[0013] As a preferred embodiment, the method for preparing the sulfide material for solid electrolytes is as follows: under vacuum and a protective atmosphere, using anhydrous LiOH solid as the lithium source, a non-protic aromatic solvent and / or hydrogenated aromatic solvent as the reaction medium are added to form a suspension. Under stirring, the temperature is raised to 100℃~200℃, hydrogen sulfide gas is introduced, and a gas-solid heterogeneous acid-base reaction is carried out to obtain the sulfide material for solid electrolytes.

[0014] This invention uses a three- or four-necked round-bottom flask as a reactor, equipped with a stirrer, thermometer sleeve, gas inlet pipe (deep below the liquid surface), and gas outlet pipe (connected to a condenser reflux device and a tail gas treatment system). All components are thoroughly dried and assembled. The reactor is then evacuated and repeatedly purged with an inert gas (such as argon) 3 to 5 times to ensure an oxygen-free and water-free internal environment.

[0015] In the above-described reaction environment, the method for preparing the sulfide material for solid electrolytes according to the present invention specifically includes the following steps: S1. Suspension Preparation and Preheating: Under an inert atmosphere (continuously purging a small flow of argon or operating in a glove box), the prepared anhydrous LiOH solid powder is added to the reactor through the feed port. A predetermined volume of the treated reaction medium is added to the reactor using a metering pump or syringe. The mass-volume concentration (solid content) of LiOH in the reaction medium is controlled at 5%–20%, preferably 8%–15%, to ensure good stirring and mass transfer. Mechanical stirring is started, with the speed controlled at 300 rpm–800 rpm (depending on the reactor size), to uniformly disperse the LiOH powder in the solvent and form a stable suspension.

[0016] S2, turn on the heating mantle or oil bath and slowly heat the suspension to the target reaction temperature. The target temperature is set between 10°C below the boiling point of the reaction medium and the boiling point of the solvent. Taking decahydronaphthalene as an example, its boiling point is approximately 187°C, and the reaction temperature can be set between 177°C and 187°C. Maintain stirring and an inert atmosphere during the heating process.

[0017] In step S3, commercially available or self-produced H2S gas is sequentially passed through a drying tower containing concentrated sulfuric acid and a drying tube containing molecular sieves to remove moisture and other possible impurities, yielding pure H2S gas. Once the reaction system temperature stabilizes at a set value (e.g., 190°C), dried H2S gas is introduced, controlled by a mass flow meter. This constant-rate gas flow simplifies the operation process, reduces the complexity of process control, and facilitates standardization and automation for industrial production. It also helps maintain long-term stability of the pressure, temperature, and concentration fields within the reactor, avoiding interference from gas flow fluctuations and resulting in lithium sulfide products with more concentrated particle size distribution and more uniform morphology. Furthermore, constant gas flow reduces the workload of on-site operators and their reliance on experience-based judgment, improving production safety and operability.

[0018] S4, since the reaction is exothermic, requires close monitoring of the reaction temperature. This temperature should be controlled within ±2℃ of the set value by adjusting the heating power and / or the gas flow rate. The water produced in the reaction immediately vaporizes and is discharged from the outlet along with unreacted H2S and the carrier gas (argon). After partially recovering any entrained solvent vapors in the condenser (condensation temperature set at 5℃~10℃), the vapors are introduced into the tail gas absorption device (such as an alkali absorption tower) for treatment. The reaction progress can be indirectly monitored by installing a humidity sensor in the tail gas pipeline (in the later stages of the reaction, as water production decreases, the tail gas humidity decreases).

[0019] S5, the reaction continues. The theoretical endpoint can be calculated based on the total amount of H2S introduced (usually the introduced amount is slightly higher than the stoichiometric ratio by 105%~110% to ensure complete conversion of LiOH; in this invention, the ratio of anhydrous LiOH solid to hydrogen sulfide gas is 0.5 mol: 11.76 L~12.32 L). In actual operation, the endpoint can be comprehensively determined by monitoring the pressure of the reaction system (the pressure tends to stabilize when H2S absorption is nearly complete) or by taking samples periodically (under strictly inert conditions) for rapid chemical analysis (such as detecting Li⁺ residue in the filtrate). After reaching the endpoint, heating and H2S introduction are stopped, and inert gas is continuously introduced to purge the reaction system for 10 min~30 min to remove dissolved and residual H2S.

[0020] S6. After the reaction is complete, stop heating and aeration. Keep the reactor sealed and continuously purge with a small flow of inert gas (such as argon) for protection. Transfer the entire reaction apparatus (or its contents to a dedicated sealed container) into an inert atmosphere glove box. Ensure the container is airtight during the transfer process to prevent air ingress.

[0021] Inside the glove box, place the container containing the reaction slurry either still or on a cooling platform to allow it to cool naturally to room temperature (20℃~25℃). During cooling, the Li₂S solid gradually settles. Inside the glove box, assemble a filtration device (such as a Buchner funnel with a sintered core and a filter bottle). Lead the suction port of the filter bottle outside the glove box through a sealed pipeline and connect it to a vacuum pump located outside the box. Install a safety buffer bottle and an inlet valve for filling with inert gas on the pipeline. Pour the cooled slurry into the Buchner funnel. Start the vacuum pump and perform filtration under negative pressure. This cold filtration process utilizes the pressure difference to accelerate solid-liquid separation, yielding a filter cake.

[0022] Ether Preparation: Anhydrous ether for washing must be thoroughly dehydrated and deoxygenated and stored in a sealed bottle in a glove box. It can be cooled to room temperature or slightly below room temperature before use. Keep the filter cake in a funnel, maintaining a slight positive pressure flow of inert gas over the surface of the filter cake (e.g., placing a hood filled with argon gas above the funnel) to isolate it from air. Using a syringe or dropper, slowly and evenly pour cold anhydrous ether over the surface of the filter cake, ensuring the ether fully wets all solids. The initial addition should be approximately twice the volume of the filter cake. Allow to stand for about 30 seconds to 1 minute to allow the ether to fully dissolve any remaining high-boiling-point reaction solvent (such as p-xylene). Reapply a slight vacuum and filter out the ether wash solution. Repeat the above steps for 3–5 washes. Usually, after the third wash, the collected filtrate should be essentially colorless and transparent. After the final filtration, maintain the vacuum for about 5 minutes to remove as much ether as possible from the filter cake. Subsequently, the wet filter cake, still containing a small amount of low-boiling-point solvent, is transferred to a vacuum drying apparatus under an inert atmosphere. Because low-boiling-point solvents (such as diethyl ether) are highly volatile, this transfer operation must be rapid and ensure complete isolation from air throughout the process.

[0023] Product drying and collection: Transfer: After washing and drying, remove the filter cake (which is now moist lithium sulfide containing a small amount of residual diethyl ether) from the filtration device and quickly transfer it to an open, clean sample tray or crucible. Let the sample tray stand in a glove box for 10-15 minutes. Due to the extremely high volatility of diethyl ether, most of the residual diethyl ether will evaporate naturally at room temperature.

[0024] Vacuum drying: Place the sample tray into a vacuum drying oven. Close the oven and start the vacuum pump to reduce the system pressure to <10 Pa. Since diethyl ether has an extremely low boiling point (34.6℃), a mild drying temperature of 35℃~45℃ is sufficient. At this temperature and under high vacuum, residual trace amounts of diethyl ether and any azeotropic moisture will be efficiently removed. The drying time is only 2-4 hours.

[0025] Cooling and Collection: After drying, allow the sample to cool naturally to room temperature (<30℃) while maintaining a high vacuum. Turn off the vacuum pump and slowly fill the drying chamber with high-purity inert gas (such as argon) until atmospheric pressure is reached. Open the drying chamber in the glove box, immediately collect and weigh the dried lithium sulfide powder, and seal it in a container filled with argon.

[0026] In a preferred embodiment, the method of introducing hydrogen sulfide gas is to introduce it at a flow rate of 0.05 L / min to 0.1 L / min for 4 hours.

[0027] In a preferred embodiment, the solid content of anhydrous LiOH solid in the suspension is 5%~20%; the ratio of anhydrous LiOH solid to reaction medium is 1g:16mL~21mL. Regarding the solid content of anhydrous LiOH solid in the suspension, i.e., its mass concentration, if the mass concentration is too low, the volume becomes large and difficult to handle; if the mass concentration is too high, the volume becomes small, and due to the excessive solid matter, a suspension cannot be formed, preventing sufficient reaction with hydrogen sulfide gas in the later stages. This results in a decrease in the purity of sulfides in the product, affecting the performance of the solid electrolyte.

[0028] In a preferred embodiment, the ratio of anhydrous LiOH solid to hydrogen sulfide gas is 0.5 mol: 12 L to 25 L.

[0029] In a preferred embodiment, the anhydrous LiOH solid is obtained by drying LiOH·H2O as raw material at a vacuum degree of <100Pa and a temperature of 80℃~120℃ for 12h~24h.

[0030] In a preferred embodiment, after the gas-solid heterogeneous acid-base reaction is completed, the hydrogen sulfide gas is stopped, and the mixture is purged with an inert gas for 10 to 30 minutes.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a method for preparing sulfide materials for solid electrolytes. Anhydrous LiOH solid is used as the lithium source, hydrogen sulfide gas is used as the sulfur source, and aprotic aromatic solvent and / or hydrogenated aromatic solvent is used as the reaction medium. The gas-solid heterogeneous acid-base reaction is carried out at 100℃~200℃ under vacuum and a protective atmosphere to obtain sulfide materials for solid electrolytes.

[0032] This invention uses aprotic aromatic solvents and / or hydrogenated aromatic solvents as reaction media. These solvents do not contain active protons and will not undergo proton exchange reactions with the lithium source LiOH or the product Li₂S, thus avoiding side reactions. Furthermore, these solvents exhibit excellent chemical stability within the reaction temperature range of 100℃ to 200℃, showing no chemical reaction with LiOH, H₂S, or Li₂S, fundamentally eliminating the possibility of solvent involvement in side reactions and ensuring the high purity of the reaction system.

[0033] The reaction medium used in this invention has extremely low solubility for LiOH, allowing it to be stably suspended in the solvent as solid particles, forming an ideal solid-liquid-gas three-phase reaction interface. At the same time, the reaction medium has moderate solubility for H2S gas, which is conducive to the diffusion of H2S molecules to the surface of LiOH particles and their reaction, avoiding the runaway reaction caused by excessive dissolution of H2S, thus achieving controllability and high efficiency of the reaction process.

[0034] The reaction media used in this invention all have boiling points above 100℃, allowing the reaction to proceed above the boiling point of water. The water generated in the reaction immediately vaporizes at the reaction temperature and is carried out of the reaction system by the inert gas stream and solvent vapor. This in-situ dehydration mechanism not only continuously pushes the reaction equilibrium to the right, promoting the complete conversion of LiOH, but also effectively avoids contact between liquid water and Li2S, suppressing the hydrolysis side reaction of Li2S from the source, and significantly improving the purity and stability of the product.

[0035] The aromatic solvent used in this invention has moderate surface tension, which can form a stable solid-liquid interface on the surface of LiOH particles, promoting the uniform nucleation of Li2S on the particle surface. At the same time, the solvent molecules form a dynamic adsorption layer on the particle surface, generating a steric hindrance effect, which effectively prevents direct contact and fusion between particles, inhibits the formation of hard agglomerates, and thus obtains nanoscale or submicron-scale sulfide materials with uniform particle size and good dispersibility. Attached Figure Description

[0036] Figure 1 The image shows the XRD pattern of the Li2S powder prepared in Example 4 of this invention.

[0037] Figure 2 This is a SEM image of the Li2S powder prepared in Example 4 of the present invention.

[0038] Figure 3 This is a particle size distribution curve of the Li2S powder prepared in Example 4 of the present invention.

[0039] Figure 4 This is a particle size distribution curve of the Li2S powder prepared in Comparative Example 1 of the present invention.

[0040] Figure 5 The image shows the particle size distribution curve of the electrolyte prepared using Example 4 of this invention. Detailed Implementation

[0041] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0042] To address existing methods for preparing lithium sulfide materials, firstly, in liquid-phase synthesis methods using lithium hydride (LiH) as a raw material, LiH is expensive, far exceeding the price of basic lithium salts such as lithium carbonate, and is chemically extremely reactive. It also requires stringent dryness control during production, storage, and operation, resulting in high safety risks and high industrial scale-up costs. Secondly, the trace amounts of lithium oxide (Li₂O) impurities typically present in LiH raw materials are difficult to remove during the reaction, directly introducing them into the final product. This leads to high oxygen content and poor product purity in the lithium sulfide product, and these impurities significantly affect the ionic conductivity of the solid electrolyte. Thirdly, in aprotic solvents such as anhydrous tetrahydrofuran (THF) or diethyl ether, the nucleation and growth of lithium sulfide are difficult to precisely control, leading to uncontrolled agglomeration of the product. This results in large particles with a wide particle size distribution and limited specific surface area, making it difficult to obtain highly reactive nano- or submicron-sized uniform particles. Based on these technical problems, this invention provides a method for preparing sulfide materials for solid electrolytes.

[0043] The technical solution of the present invention will be analyzed and described in detail below.

[0044] This invention first provides a method for preparing sulfide materials for solid electrolytes, comprising the following steps: Using anhydrous LiOH solid as the lithium source, hydrogen sulfide gas as the sulfur source, and aprotic aromatic solvent and / or hydrogenated aromatic solvent as the reaction medium, a gas-solid heterogeneous acid-base reaction was carried out at 100℃~200℃ under vacuum and a protective atmosphere to obtain sulfide materials for solid electrolytes.

[0045] The aprotic aromatic solvent is at least one of toluene, p-xylene, and ethylbenzene, and toluene cannot be used alone as a reaction medium; the hydrogenated aromatic solvent is at least one of tetrahydronaphthalene, decahydronaphthalene, dodecane, and hexadecane.

[0046] In the above technical solution, aprotic aromatic solvents and / or hydrogenated aromatic solvents are used as the reaction medium. These solvents do not contain active protons and will not undergo proton exchange reactions with the lithium source LiOH or the product Li₂S, thus avoiding side reactions. Simultaneously, these solvents exhibit excellent chemical stability within the reaction temperature range of 100℃ to 200℃, without reacting with LiOH, H₂S, or Li₂S, fundamentally eliminating the possibility of solvent involvement in side reactions and ensuring the high purity of the reaction system. The reaction medium has extremely low solubility for LiOH, allowing it to remain stably suspended in the solvent as solid particles, forming an ideal solid-liquid-gas three-phase reaction interface. At the same time, the reaction medium has moderate solubility for H₂S gas, which facilitates the diffusion of H₂S molecules to the surface of LiOH particles and their reaction, avoiding runaway reactions caused by excessive H₂S dissolution, thereby achieving controllability and high efficiency in the reaction process. The boiling points of the reaction media are all above 100℃, allowing the reaction to proceed above the boiling point of water. The water generated in the reaction immediately vaporizes at the reaction temperature and is carried out of the reaction system by the inert gas flow and solvent vapor. This in-situ dehydration mechanism not only continuously drives the reaction equilibrium to the right, promoting the complete conversion of LiOH, but also effectively avoids contact between liquid water and Li2S, suppressing the hydrolysis side reaction of Li2S from the source, and significantly improving the purity and stability of the product. Aromatic solvents have moderate surface tension, which can form a stable solid-liquid interface on the surface of LiOH particles, promoting the uniform nucleation of generated Li2S on the particle surface. At the same time, solvent molecules form a dynamic adsorption layer on the particle surface, generating a steric hindrance effect, effectively preventing direct contact and fusion between particles, inhibiting the formation of hard agglomerates, thereby obtaining nanoscale or submicron-sized sulfide materials with uniform particle size and good dispersibility.

[0047] The technical effects of the present invention will be described below with reference to specific embodiments and comparative examples.

[0048] Example 1 A method for preparing a sulfide material for solid electrolytes includes the following steps: S1. In an argon-filled glove box (H2O < 1 ppm), add 12.0 g (0.5 mol) of anhydrous LiOH powder to a 500 mL three-necked flask. Add 200 mL of strictly dried p-xylene (purity > 99%, moisture < 10 ppm). Install a stirrer, reflux condenser, and thermometer, and purge the system with argon gas for protection. Heat to 138 ± 2 °C (boiling point of p-xylene), and turn on mechanical stirring (600 rpm) to form a homogeneous suspension.

[0049] After the temperature stabilized at 138℃, H2S gas, dried by molecular sieves, was introduced into the suspension of S1 at a stable flow rate of 0.05 L / min. Within 15 minutes, the system gradually changed from white to light yellow, eventually becoming a uniform grayish-yellow. The exothermic reaction accelerated the reflux, and continuous water droplets condensed at the bottom of the condenser and dripped into the water separator. The reaction continued for 4 hours. The reaction endpoint was determined by monitoring the change in exhaust gas humidity (the humidity sensor showed that the outlet humidity dropped from its peak value to near ambient levels). A total of 12 L of H2S was introduced.

[0050] S3. After the reaction is complete, heating is stopped, and argon gas is continuously purged for 20 minutes. The reactor is cooled to room temperature (approximately 25°C) and transferred to an argon glove box. In the glove box, a sintered funnel connected to an external vacuum system is used for vacuum filtration to separate the solid product, yielding a filter cake. The filter cake is washed with 3 × 50 mL of anhydrous diethyl ether, allowing it to stand for 30 seconds after each addition of ether before filtration. After washing, filtration continues for 10 minutes to remove as much residual ether as possible. The wet filter cake is transferred to a vacuum drying oven and dried at 45°C and <5 Pa for 4 hours. A pale yellow Li₂S powder with a purity of 78% is obtained.

[0051] Example 2 A method for preparing a sulfide material for solid electrolytes includes the following steps: S1. In an argon glove box (H2O < 1 ppm), weigh 12.0 g (0.5 mol) of dry LiOH and transfer it to a 500 mL dry three-necked flask equipped with a powerful mechanical stirrer, thermometer, and reflux condenser. Add 200 mL of tetrahydronaphthalene (boiling range 205℃~208℃) dried with molecular sieves and heat to 195±3℃ (solvent reflux).

[0052] When the temperature of S2 stabilizes at 195℃, H2S gas is introduced into the suspension of S2 at a flow rate of 0.1L / min. The system quickly turns dark gray, and due to the high temperature, water vapor is rapidly carried out. Clear water droplets can be seen condensing in the condenser. After about 3 hours of reaction, the humidity of the tail gas is extremely low, and the reaction is stopped. At this time, heating and gas introduction are stopped. The total amount of H2S introduced is 18L.

[0053] After reaction S2 is complete, heating is stopped, and argon gas is continuously purged for 20 minutes. The reactor is cooled to room temperature (approximately 25°C) and transferred to an argon glove box (water and oxygen content <1 ppm). In the glove box, a sintered funnel connected to an external vacuum system is used for vacuum filtration to separate the solid product, yielding a grayish-white filter cake. The filter cake is washed with 3 × 50 mL of anhydrous diethyl ether, allowing it to stand for 30 seconds after each addition of ether before filtration. After washing, filtration continues for 10 minutes to remove residual ether to the maximum extent. The wet filter cake is transferred to a vacuum drying oven and dried at 150°C and <5 Pa for 10 hours. A pale yellow Li₂S powder with a purity of 95% is obtained.

[0054] Example 3 A method for preparing a sulfide material for solid electrolytes includes the following steps: S1. In an argon glove box, weigh 12.0 g (0.5 mol) of anhydrous LiOH powder and add it to a 500 mL three-necked flask. Add 125 mL of anhydrous toluene and 125 mL of anhydrous dodecane to form a mixed solvent with a volume ratio of 1:1 and a total volume of 250 mL. Install stirring, condensation and gas introduction devices, and purify the system with argon gas. Heat the system to 162±2℃ (the reflux temperature of the mixed system), and turn on the stirrer (600 rpm) to form a uniform suspension.

[0055] S2, at a temperature of 152℃, dry H2S gas was introduced into the suspension of S1 at a flow rate of 0.1 L / min. The system changed from white to a uniform dark gray within 45 minutes, a faster rate of color change than the pure toluene system (110℃) but slower than the pure dodecane system (215℃). The rate of water droplet dripping in the condenser remained stable. After the reaction continued for 3.8 hours, the endpoint was determined by monitoring the humidity of the tail gas; the humidity decreased significantly and tended to stabilize. At this point, heating and gas introduction were stopped, with a cumulative H2S introduction of 25 L.

[0056] S2, after the reaction is complete, heating is stopped, and argon gas is continuously purged for 20 minutes. The reactor is cooled to room temperature (approximately 25°C) and transferred to an argon glove box (water and oxygen content <1ppm). In the glove box, a sand core funnel connected to an external vacuum system is used for vacuum filtration to separate the solid product, yielding a grayish-white filter cake. The filter cake is washed with 4 × 40 mL of anhydrous diethyl ether, and filtered again after each wash. To completely remove the high-boiling-point decahydronaphthalene, diethyl ether is added during the fourth wash, followed by standing for 2 minutes. After washing, filtration continues for 10 minutes to remove residual diethyl ether to the maximum extent. The wet filter cake is transferred to a vacuum drying oven and dried at 48°C and <5Pa for 4.2 hours to obtain a pale yellow Li₂S powder with a purity of 90%.

[0057] Example 4 A method for preparing a sulfide material for solid electrolytes includes the following steps: S1. In an argon-filled glove box, add 12.0 g (0.5 mol) of anhydrous LiOH powder, vacuum-dried at 120 °C, to a 500 mL three-necked flask. Add 180 mL of decahydronaphthalene dried through molecular sieves and 20 mL of dried toluene to form a mixed solvent with a volume ratio of 9:1, for a total volume of 200 mL. Install the stirring, condenser, and gas introduction device, and purge the system with argon gas for protection. Heat to 195 ± 2 °C (the reflux temperature of this mixture), and start stirring (500 rpm) to form a homogeneous suspension.

[0058] After the temperature stabilized at 195℃, dry H2S gas was introduced into the suspension of S1 at a flow rate of 100 mL / min. The system was observed to change from a white suspension to a uniform light gray within 30 minutes. The reaction temperature was approximately 20℃ lower than the pure dodecane system (215℃) due to the addition of toluene, but significantly higher than the pure toluene system (110℃). Water droplets continuously flowed down the condenser. After the reaction continued for 3.5 hours, online humidity monitoring confirmed the reaction was complete, and the H2S introduction was stopped. The total amount of H2S introduced was 21 L.

[0059] S3. After the reaction is complete, stop heating and continue purging with argon gas for 15 minutes. Cool the reactor to room temperature (approximately 25°C) and transfer the entire reactor to an argon glove box (H2O < 1 ppm, O2 < 1 ppm). Inside the glove box, vacuum filter the reaction slurry through a Buchner funnel connected to an external vacuum system (cold filtration). The filter cake is first washed with 3 × 40 mL of anhydrous diethyl ether using standard methods, and dried after each wash. Given that decahydronaphthalene is the main component and has a high viscosity, an additional wash with 20 mL of methyl tert-butyl ether (MTBE, boiling point 55°C) is added to ensure thorough removal of high-boiling-point solvent residues by utilizing its slightly stronger solubility. After washing, continue filtration for 5 minutes to remove residual diethyl ether to the maximum extent. Transfer the wet filter cake to a vacuum drying oven and dry at 48°C and <10 Pa for 4.5 hours. After drying, cool to below 30°C under continuous vacuum and then purge with argon gas to restore atmospheric pressure. The product was collected in a glove box to obtain a white, free-flowing Li2S powder with a purity of 99.9% and a more uniform particle size distribution.

[0060] To further demonstrate the technical effects of the present invention, a comparative example is also provided, as follows.

[0061] Comparative Example 1 A method for preparing a sulfide material for solid electrolytes includes the following steps: S1. In an argon-filled glove box (H2O < 1 ppm), accurately weigh 12.0 g (0.5 mol) of anhydrous LiOH powder that has been vacuum-dried at 120 °C for 24 hours, and transfer it to a 500 mL dry three-necked flask equipped with a powerful mechanical stirrer, thermometer, and reflux condenser. Add 250 mL of toluene dried with molecular sieves using a syringe pump. Remove the apparatus from the glove box and connect it to an H2S gas path that has been cooled in a cold trap (-40 °C) and dried with molecular sieves. Under continuous argon gas flow (50 mL / min) protection, start stirring (500 rpm) and heat to 110 ± 2 °C (toluene slightly boils) to form a homogeneous suspension.

[0062] After the temperature stabilizes at 110℃ in S2, the gas path is switched, and dry H2S gas is introduced into the suspension in S1 at a stable flow rate of 0.08 L / min. The reaction occurs immediately, and the solid suspension can be observed to gradually change from white to light yellowish-gray. The reaction system is kept under mild reflux. Monitoring with a humidity sensor connected to the reactor outlet shows that the initial tail gas humidity rises rapidly (due to water production), and after about 4 hours, the humidity drops significantly and tends to stabilize. At this point, heating and gas supply are stopped, and a total of 21 L of H2S has been introduced.

[0063] S3. After the reaction is complete, heating is stopped, and argon gas is continuously purged for 20 minutes. The reactor is cooled to room temperature (approximately 25°C) and transferred to an argon-filled glove box (water and oxygen content <1 ppm). In the glove box, a sintered funnel connected to an external vacuum system is used for vacuum filtration to separate the solid product, yielding a grayish-white filter cake. The filter cake is washed routinely with 3 × 40 mL of anhydrous diethyl ether, allowing it to stand for 30 seconds after each addition of ether before filtration. After washing, filtration continues for 10 minutes to remove residual diethyl ether to the maximum extent. The wet filter cake is transferred to a vacuum drying oven and dried at 48°C and <10 Pa for 4.5 hours. After drying, it is cooled to below 30°C under continuous vacuum, and argon gas is introduced to restore atmospheric pressure. The product is collected in the glove box, yielding a pale yellow Li₂S powder with a purity of 46%.

[0064] The performance of the sulfide materials for solid electrolytes prepared in the above embodiments and comparative examples was tested.

[0065] Based on the Li2S product prepared in Example 4 (toluene / dodecane mixed medium), this invention uses it as a key raw material to prepare a typical Li6PS5Cl type sulfide solid electrolyte, and conducts systematic electrochemical performance tests.

[0066] Preparation of solid electrolyte: Li2S, P2S5 (99.9%) and LiCl (99.9%) prepared in Example 4 were weighed according to the stoichiometric ratio of 6:1:1. The raw material mixture was loaded into a planetary ball mill jar under argon protection and ball-milled at 500 rpm for 20 hours. The ball-milled powder was then heat-treated at 550°C for 2 hours in an argon atmosphere to obtain pale yellow Li6PS5Cl solid electrolyte powder.

[0067] The synthesized Li6PS5Cl solid electrolyte was tested as follows and compared with a similar electrolyte prepared using commercially available high-temperature Li2S (as a control sample, purity 99.5%). The results are shown in Table 1.

[0068] Test methods and test conditions 1. Ionic conductivity: The electrochemical impedance spectroscopy was performed at room temperature (25°C) under cold-pressed sheet conditions (pressure: 370 MPa).

[0069] 2. Electronic conductivity: DC polarization method was used.

[0070] 3. Activation energy: Calculated by temperature impedance spectroscopy (25℃~80℃).

[0071] Table 1. Performance comparison between Li₂S prepared by this invention and commercially available high-temperature method Li₂S. The XRD pattern of the electrolyte prepared using the sulfide material for solid electrolytes provided in Example 4 of this invention is shown below. Figure 1 As shown, the electrolyte synthesized using Li2S prepared in Example 4 of this invention exhibits a pure-phase Argyrodite structure in its XRD pattern, with high crystallinity and no impurity peaks.

[0072] Figure 2 This is a SEM image of the Li₂S powder prepared in Example 4 of this invention. Figure 2 It can be seen that the lithium sulfide product prepared in Example 4 of the present invention has a uniform morphology and basically no agglomeration.

[0073] Figure 3 This is a particle size distribution curve of the Li2S powder prepared in Example 4 of the present invention. Figure 3 As can be seen, the particle size distribution curve of lithium sulfide prepared in Example 4 shows a single peak, D 50 =1.41μm, D 30 =3.39μm, which is relatively small in size.

[0074] Figure 4 This is a particle size distribution curve of the Li₂S powder prepared in Comparative Example 1 of this invention. Figure 4It can be seen that the Li2S powder prepared in Comparative Example 1 of this invention has low purity. 90 =27.63μm, and Figure 3 The particle size of the particles in Example 4 was significantly larger and the distribution was uneven.

[0075] The particle size analysis of the electrolyte synthesized from the sulfide material for solid electrolyte prepared using Example 4 of this invention is as follows: Figure 4 As shown, the electrolyte synthesized using the sulfide material for solid electrolytes prepared in Example 4 of this invention has a small particle size (D). 50 (1.8μm) and uniformly distributed. Uniform and fine electrolyte particles are beneficial for forming high-density, low-porosity electrolyte sheets during cold pressing, reducing grain boundary resistance, and thus improving ionic conductivity.

[0076] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a sulfide material for solid electrolytes, characterized in that, Includes the following steps: Using anhydrous LiOH solid as the lithium source, hydrogen sulfide gas as the sulfur source, and aprotic aromatic solvent and / or hydrogenated aromatic solvent as the reaction medium, a gas-solid heterogeneous acid-base reaction was carried out at 100℃~200℃ under vacuum and protective atmosphere to obtain sulfide materials for solid electrolytes. The aprotic aromatic solvent is at least one of toluene, p-xylene, and ethylbenzene, and toluene cannot be used alone as a reaction medium; the hydrogenated aromatic solvent is at least one of tetrahydronaphthalene, decahydronaphthalene, dodecane, and hexadecane.

2. The method for preparing sulfide materials for solid electrolytes according to claim 1, characterized in that, The reaction medium is an aprotic aromatic solvent, and the aprotic aromatic solvent is p-xylene and / or ethylbenzene.

3. The method for preparing sulfide materials for solid electrolytes according to claim 1, characterized in that, The reaction medium is a mixture of aprotic aromatic solvent and hydrogenated aromatic solvent. The aprotic aromatic solvent is at least one of toluene, p-xylene, and ethylbenzene, and the hydrogenated aromatic solvent is at least one of tetrahydronaphthalene, decahydronaphthalene, dodecane, and hexadecane. The volume ratio of the aprotic aromatic solvent to the hydrogenated aromatic solvent is 1:1 to 9.

4. The method for preparing sulfide materials for solid electrolytes according to claim 1, characterized in that, The method for preparing the sulfide material for solid electrolytes is as follows: under vacuum and a protective atmosphere, anhydrous LiOH solid is used as the lithium source, and a non-protic aromatic solvent and / or hydrogenated aromatic solvent are added to form a suspension. Under stirring, the temperature is raised to 100℃~200℃, hydrogen sulfide gas is introduced, and a gas-solid heterogeneous acid-base reaction is carried out to obtain the sulfide material for solid electrolytes.

5. The method for preparing sulfide materials for solid electrolytes according to claim 4, characterized in that, The method for introducing hydrogen sulfide gas is to introduce it at a flow rate of 0.05 L / min to 0.1 L / min for 4 hours.

6. The method for preparing sulfide materials for solid electrolytes according to claim 4, characterized in that, The solid content of anhydrous LiOH solid in the suspension is 5%~20%; the ratio of anhydrous LiOH solid to reaction medium is 1g:16mL~21mL.

7. The method for preparing sulfide materials for solid electrolytes according to claim 4, characterized in that, The ratio of anhydrous LiOH solid to hydrogen sulfide gas is 0.5 mol: 12 L~25 L.

8. The method for preparing sulfide materials for solid electrolytes according to claim 4, characterized in that, The anhydrous LiOH solid was obtained by drying LiOH·H2O as raw material at a vacuum degree of <100Pa and a temperature of 80℃~120℃ for 12h~24h.

Images