Lithium sulfide powder and modification method thereof, solid electrolyte, battery and electric equipment

Abstract

The invention provides lithium sulfide powder and a modification method thereof, a solid electrolyte, a battery and electric equipment, and relates to the technical field of lithium batteries. The modification method of the lithium sulfide powder comprises the following steps: dissolving target lithium sulfide coarse powder in a first organic solvent to obtain a dissolving solution; adding a second organic solvent into the dissolving solution, and carrying out shock cooling treatment to obtain precipitated lithium sulfide microcrystalline powder; the solubility of the first organic solvent to lithium sulfide is greater than that of the second organic solvent. By controlling the solubility and the temperature of the lithium sulfide in different solvents, the method of avoiding high-energy-consumption solvent evaporation and separating out crystals by utilizing solubility difference and shock cooling treatment is adopted, so that the complex process links are reduced, the energy consumption is reduced, high-purity lithium sulfide microcrystals are quickly separated out, the production period is shortened, and the efficiency is improved. Through the improvements, the cost is reduced, the consistency and reliability of products are improved, and the production of the lithium sulfide powder is more economical, efficient and environment-friendly.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and more particularly, to a lithium sulfide powder, a modification method thereof, a solid electrolyte, a battery, and an electricity-related device. Background Art

[0002] The all-solid-state battery technology is regarded as an important development direction of lithium-ion battery technology due to its advantages in energy density, safety, and cycle stability. As a key technical route among them, the sulfide-based all-solid-state battery has received extensive attention from global researchers and the industrial community due to its excellent ionic conductivity and good thermal stability. As the core material of this technical route, the performance of the sulfide solid electrolyte directly affects the overall performance of the battery. Therefore, its batch preparation technology has become a key factor restricting the development of all-solid-state batteries.

[0003] In the preparation process of sulfide solid electrolytes, lithium sulfide, as a key raw material, its synthesis technology has a decisive impact on the efficiency and cost of the entire preparation process. Currently, the preparation processes of lithium sulfide are mainly divided into two categories: liquid-phase synthesis and solid-phase synthesis. Solid-phase synthesis has become the mainstream process commonly used at home and abroad due to its advantages in production efficiency, safety, environmental protection, and process difficulty. However, despite its excellent performance in many aspects, there are still significant challenges in the purification and particle size control of lithium sulfide.

[0004] Specifically, in the traditional solid-phase synthesis process for purifying lithium sulfide, impurities are usually removed by dissolving the crude product and then filtering, and high-purity lithium sulfide is obtained by evaporating the solvent for recrystallization. In this process, due to the low solubility of lithium sulfide in organic solvents, it is often necessary to reduce the solid content to achieve complete dissolution, resulting in extremely high energy consumption during the solvent evaporation process. In addition, the lithium sulfide obtained by evaporating the solvent and recrystallizing has a large particle size, which is difficult to meet the particle size requirements for the preparation of sulfide solid electrolytes and requires an additional grinding step. Lithium sulfide has active chemical properties, and these additional process steps not only increase the production cost but also may lead to a decline in product quality due to chemical reactions or physical damage.

[0005] In summary, the existing lithium sulfide preparation technologies have deficiencies in purification efficiency, energy consumption, particle size control, and product quality. These defects limit the batch production of sulfide solid electrolytes, and thus affect the development and application of all-solid-state battery technology. Therefore, developing a new lithium sulfide preparation technology to solve the defects in the existing technology is of great significance for promoting the progress of all-solid-state battery technology.

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

[0007] The object of the present invention is to provide a method for modifying lithium sulfide powder, and the method for modifying lithium sulfide powder has the advantages of reducing production cost and simplifying the process flow, etc.

[0008] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted:

[0009] The object of the present invention is to provide a method for modifying lithium sulfide powder. In the method for modifying lithium sulfide powder, based on the solubility difference of the target lithium sulfide coarse powder under different solvents and temperature conditions, crystals are precipitated by the cooling-induced recrystallization method to obtain lithium sulfide microcrystalline powder.

[0010] In an alternative embodiment, the method for modifying lithium sulfide powder includes:

[0011] Dissolve the target lithium sulfide coarse powder in a first organic solvent to obtain a solution;

[0012] Add a second organic solvent to the solution and perform a rapid cooling treatment to obtain precipitated lithium sulfide microcrystalline powder; wherein, the solubility of the first organic solvent in lithium sulfide is greater than that of the second organic solvent.

[0013] In an alternative embodiment, the step of dissolving the target lithium sulfide coarse powder in a first organic solvent to obtain a solution includes:

[0014] Under heating conditions, add the target lithium sulfide coarse powder to the first organic solvent and mix to obtain a mixture;

[0015] Maintain the heating conditions and perform solid-liquid separation treatment on the mixture to obtain the solution;

[0016] In an alternative embodiment, the heating temperature of the heating conditions is not higher than the boiling point of the first organic solvent.

[0017] In an alternative embodiment, the addition amount of the target lithium sulfide coarse powder is at least sufficient to precipitate the lithium sulfide microcrystalline powder after adding the second organic solvent to the solution and performing a rapid cooling treatment;

[0018] In an alternative embodiment, the addition amount of the target lithium sulfide coarse powder in the first organic solvent is not less than the amount corresponding to the maximum solubility of lithium sulfide in the first organic solvent under the heating conditions;

[0019] In an alternative embodiment, under heating conditions, the target lithium sulfide coarse powder added to the first organic solvent for mixing should satisfy that the first organic solvent cannot dissolve the newly added target lithium sulfide coarse powder anymore, so as to obtain a saturated mixture.

[0020] In an alternative embodiment, before adding the second organic solvent to the dissolution solution, the method further includes: pre-cooling the second organic solvent; wherein the temperature of the pre-cooling treatment is not lower than the freezing point of the second organic solvent; and / or,

[0021] the temperature of the quenching treatment is not lower than the freezing point of the solution after mixing the saturated dissolution solution and the second organic solvent; and / or,

[0022] the cooling medium for the pre-cooling treatment and / or the quenching treatment includes at least one of water, heat transfer oil, dry ice, and liquid nitrogen; and / or,

[0023] the cooling rate of the quenching treatment is: not lower than 20 °C / s; and not higher than 50 °C / s.

[0024] In an alternative embodiment, adding the second organic solvent to the dissolution solution and performing a quenching treatment to obtain precipitated lithium sulfide microcrystalline powder includes:

[0025] adding the second organic solvent to the dissolution solution and performing a quenching treatment to obtain a microcrystalline mixed solution in which microcrystals precipitate;

[0026] performing a solid-liquid separation treatment on the microcrystalline mixed solution to obtain a microcrystalline precursor;

[0027] performing a heat treatment on the microcrystalline precursor to obtain the lithium sulfide microcrystalline powder;

[0028] In an alternative embodiment, the solid-liquid separation treatment includes centrifugation and / or filtration;

[0029] In an alternative embodiment, the atmosphere of the heat treatment includes an inert gas atmosphere and / or vacuum;

[0030] In an alternative embodiment, the temperature of the heat treatment is 200 °C to 700 °C.

[0031] In an alternative embodiment, the first organic solvent is a solvent that is easily soluble or extremely soluble in lithium sulfide; the second organic solvent is a solvent that is poorly soluble or insoluble in lithium sulfide;

[0032] In an alternative embodiment, the first organic solvent is a solvent that is easily soluble or extremely soluble in lithium sulfide and is poorly soluble or insoluble in impurity substances other than lithium sulfide;

[0033] In an alternative embodiment, the solubility of the first organic solvent in lithium sulfide at room temperature is not lower than 1 wt%; the solubility of the second organic solvent in lithium sulfide at room temperature is not higher than 0.05 wt%;

[0034] In an alternative embodiment, the impurity substance includes at least one of lithium sulfate, lithium carbonate, and lithium hydroxide;

[0035] In an alternative embodiment, the first organic solvent includes at least one of methanol, ethanol, propanol, acetone, acetonitrile, ethylene glycol, aniline, and N-methylpyrrolidone;

[0036] In an alternative embodiment, the second organic solvent is at least one of an ether solvent, a ketone solvent, and an alkane solvent.

[0037] The second object of the present invention is to provide a lithium sulfide microcrystalline powder, which is prepared by the modification method of the lithium sulfide powder in the above-mentioned embodiment.

[0038] The third object of the present invention is to provide a solid electrolyte, which includes the lithium sulfide microcrystalline powder as described in the above-mentioned embodiment.

[0039] The fourth object of the present invention is to provide a battery, which includes a solid electrolyte; the solid electrolyte includes the lithium sulfide microcrystalline powder as described in the above-mentioned embodiment.

[0040] The fifth object of the present invention is an electric device, which includes the battery as described in the above-mentioned embodiment.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] The present invention provides a lithium sulfide powder and its modification method, a solid electrolyte, a battery, and an electric device. The modification method of the lithium sulfide powder significantly simplifies the process flow by precisely controlling the solubility of lithium sulfide in different solvents. This method avoids the high-energy-consuming solvent evaporation step in the traditional process. By directly using the solubility difference and rapid cooling treatment to precipitate the microcrystalline powder, it not only reduces multiple complex process steps but also greatly reduces energy consumption; and can rapidly precipitate high-purity lithium sulfide microcrystals, effectively shortening the production cycle and improving production efficiency.

[0043] In summary, the modification method of the lithium sulfide powder provided by the present invention not only reduces production costs but also helps to improve the consistency and reliability of products, making the production process of lithium sulfide powder more economical, efficient, and environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0045] Figure 1 XRD pattern of the lithium sulfide microcrystalline powder obtained in Example 1 of the modification method of a lithium sulfide powder according to the present application;

[0046] Figure 2 XRD pattern of the lithium sulfide microcrystalline powder obtained in Example 2 of the modification method of a lithium sulfide powder according to the present application. Detailed implementation manners

[0047] The following will describe in detail the implementation schemes of the present invention in conjunction with the embodiments. However, those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. For those not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained through commercial procurement as conventional products.

[0048] A modification method of a lithium sulfide powder is provided in an embodiment of the present application, including:

[0049] Step S1, dissolving the target lithium sulfide coarse powder in a first organic solvent to obtain a solution.

[0050] Step S2, adding a second organic solvent to the solution and performing a rapid cooling treatment to obtain a precipitated lithium sulfide microcrystalline powder; wherein, the solubility of the lithium sulfide in the first organic solvent is greater than that in the second organic solvent.

[0051] As mentioned above, the target lithium sulfide powder refers to the lithium sulfide coarse powder to be processed and modified in this embodiment, that is, the lithium sulfide raw material containing certain impurities. It can be an important raw material for preparing sulfide solid electrolytes in sulfide-based all-solid-state batteries, and its purity and particle size have important effects on the battery performance. As the starting material in this embodiment, impurities can be removed and the particle size can be regulated through subsequent dissolution, precipitation and other steps, and finally a lithium sulfide microcrystalline powder with high purity and appropriate particle size can be obtained.

[0052] The first organic solvent refers to an organic solvent with a relatively high solubility in lithium sulfide, which is used to dissolve the target lithium sulfide coarse powder to form a solution of lithium sulfide. Due to its relatively high solubility, it can fully dissolve lithium sulfide and provide a sufficient solute basis for the subsequent precipitation process.

[0053] The second organic solvent refers to an organic solvent with a relatively low solubility in lithium sulfide. When added to the solution, it reduces the solubility of the solution in lithium sulfide and promotes the rapid precipitation of lithium sulfide microcrystals. Due to its relatively low solubility, it can effectively control the precipitation process of lithium sulfide and realize the regulation of the particle size of lithium sulfide.

[0054] As described above, the quenching treatment refers to the process of rapidly reducing the temperature of the mixed system after adding the second organic solvent, causing lithium sulfide microcrystals to precipitate rapidly. By rapid cooling, the growth rate and morphology of lithium sulfide microcrystals can be controlled, enabling the formation of fine and uniform microcrystals, which is beneficial for subsequent heat treatment and the preparation of sulfide solid electrolytes. The quenching treatment can be achieved by exposing the solution to a low-temperature environment or directly adding a pre-cooled solvent.

[0055] The solubility of lithium sulfide in the first organic solvent is greater than that in the second organic solvent, which is to effectively control the dissolution and precipitation processes of lithium sulfide. Using a first organic solvent with high solubility can fully dissolve the target lithium sulfide coarse powder to form a dissolved solution, providing sufficient solute for subsequent precipitation. After adding a second organic solvent with low solubility, the solubility of the solution in lithium sulfide rapidly decreases, prompting the rapid precipitation of lithium sulfide microcrystals. This difference in solubility is the key to achieving the purification and particle size regulation of lithium sulfide. By controlling the solubility difference of the solvents, the process flow can be simplified, production energy consumption can be reduced, production efficiency can be improved, and at the same time, lithium sulfide microcrystal powders with high purity and appropriate particle size can be obtained to meet the preparation requirements of sulfide solid electrolytes.

[0056] As described above, the lithium sulfide microcrystal powder refers to a high-purity, fine-particle-size lithium sulfide powder obtained after steps such as dissolution, precipitation, quenching treatment, and heat treatment. Its particle size can generally be in the nanometer or micrometer range. As a raw material for the preparation of sulfide solid electrolytes, its high purity and appropriate particle size help improve the ionic conductivity and mechanical properties of the battery, thereby enhancing the overall performance of all-solid-state batteries.

[0057] In this embodiment, a method of inducing the recrystallization of substances by using temperature changes is adopted. Specifically, this method can be applied to solute / solvent systems with low solubility under low-temperature conditions but with a large influence of temperature changes on solubility. Under certain conditions, such as normal temperature or high temperature, a large amount of solute can dissolve in the solvent, and when the solution cools, due to the decrease in the solubility of the solute under low-temperature conditions, it will gradually reach a supersaturated state, thereby inducing the re-precipitation of solute crystals.

[0058] This method can be effectively used to purify solid substances or separate substances mixed together. By controlling the cooling rate, the precipitation process of crystals can be precisely controlled, thereby achieving the purpose of purification or separation.

[0059] In the above method, the use of solubility differences under different solvents and temperature conditions refers to optimizing and controlling the dissolution and crystallization processes of lithium sulfide according to the changes in the dissolution properties of lithium sulfide in different solvents and at different temperatures. By precisely controlling the cooling rate and temperature, the rate and particle size of lithium sulfide crystallization can be controlled. Rapid cooling can promote the rapid formation of lithium sulfide microcrystals, while slow cooling may result in the formation of larger particles.

[0060] The modification method of lithium sulfide powder provided by the embodiments of the present application can achieve the efficient purification of lithium sulfide coarse powder by utilizing the solubility differences of lithium sulfide under different solvent and temperature conditions. By precisely controlling the dissolution and precipitation processes, this method optimizes the solubility of lithium sulfide, thereby improving the purification efficiency. At the same time, since the solvent evaporation step with high energy consumption in traditional technologies is reduced, the new method reduces energy consumption, simplifies the process flow by directly controlling the cooling rate and the selection of solvents, and realizes the rapid precipitation of lithium sulfide. In addition, this method also allows precise control of the particle size of lithium sulfide microcrystals to meet the requirements of specific applications. Combining these improvements, the new method not only improves production efficiency, reduces production time and costs, but also helps to reduce production costs and improve economic benefits.

[0061] In step S1, the target lithium sulfide coarse powder is dissolved in a first organic solvent to obtain a solution, including:

[0062] In step S11, under heating conditions, the target lithium sulfide coarse powder is added to the first organic solvent and mixed to obtain a mixture.

[0063] As described above, in this step, the lithium sulfide coarse powder is added to the first organic solvent to form a mixture of the lithium sulfide coarse powder and the first organic solvent. This step is the start of the dissolution process and lays the foundation for subsequent dissolution and purification. It can be achieved through a simple mixing operation, mixing the solid lithium sulfide coarse powder with the liquid first organic solvent.

[0064] As described above, under heating conditions, the lithium sulfide coarse powder can be added to the first organic solvent in batches. Through the mixing treatment method, the substances in the lithium sulfide coarse powder can be dissolved in the first organic solvent. During this period, continuous mixing treatment (such as stirring) can be carried out, and the heating conditions can be maintained at the same time, so that the solvent system of the first organic solvent can always be maintained at a certain high solubility, thereby obtaining a mixture of lithium sulfide in the first organic solvent.

[0065] The heating conditions help to increase the solubility of lithium sulfide in the first organic solvent and accelerate the dissolution process. Specifically, the mixing method can be achieved by heating and stirring, ultrasonic oscillation, etc., and the heating temperature and stirring speed can be controlled to optimize the dissolution efficiency. In this embodiment, mixing by stirring is preferably used.

[0066] In step S12, while maintaining the heating conditions, the mixture is subjected to solid-liquid separation treatment to obtain the solution.

[0067] As described above, while maintaining heating, solid-liquid separation is performed on the mixed solution to remove insoluble substances. A pure lithium sulfide solution is obtained, and insoluble solid impurities are removed. Solid-liquid separation ensures that the solution contains only dissolved lithium sulfide, improving the purity of the product and providing a pure raw material for subsequent crystallization steps.

[0068] As described above, while maintaining heating, solid-liquid separation is performed on the mixed solution to retain the product and remove insoluble substances. Thereby, a pure lithium sulfide solution is obtained, and insoluble solid impurities are removed. Solid-liquid separation ensures that the solution contains only dissolved lithium sulfide, improving the purity of the product and providing a pure raw material for subsequent crystallization steps.

[0069] It can be achieved by solid-liquid separation techniques such as filtration and centrifugation. The selection of an appropriate separation technique depends on the properties of the solution and the characteristics of the impurities.

[0070] It should be noted that during the dissolution process, lithium sulfide may already be close to or reach its solubility limit in the first organic solvent. If the heating condition is removed, the solution may cool rapidly, resulting in a decrease in the solubility of lithium sulfide and thus forming a precipitate. Maintaining the heating condition can prevent this from happening and ensure that lithium sulfide remains in a dissolved state. Heating can increase the solubility of lithium sulfide in the organic solvent. Performing solid-liquid separation under heating conditions can ensure that the solubility of lithium sulfide remains at a high level, which helps to remove more insoluble impurities and improve the purity of the solution. Also, if the solution cools during the separation process, lithium sulfide may crystallize due to temperature changes. Maintaining the heating condition can avoid this temperature-induced crystallization and ensure that only the addition of the second organic solvent and rapid cooling treatment are the triggering factors for crystallization.

[0071] Furthermore, the heating temperature of the heating condition is not higher than the boiling point of the first organic solvent.

[0072] In the method for modifying lithium sulfide powder, the heating condition is limited, especially by controlling the heating temperature not to exceed the boiling point of the first organic solvent. The reason is that if the heating temperature exceeds the boiling point of the first organic solvent, the solvent will start to boil and evaporate, resulting in solvent loss and environmental pollution, while also increasing energy consumption and production costs. Heating below the solvent boiling point can maintain the liquid state of the solvent, thereby maintaining the dissolution efficiency of lithium sulfide and ensuring that lithium sulfide can be fully dissolved.

[0073] In addition, in industrial production, controlling the heating temperature not to exceed the solvent boiling point can simplify the operating conditions, making the process more stable and repeatable, and by precisely controlling the heating temperature, unnecessary energy waste can be avoided and the energy efficiency of the entire process can be improved.

[0074] In some embodiments, the addition amount of the target lithium sulfide coarse powder is at least sufficient to precipitate the lithium sulfide microcrystalline powder after adding a second organic solvent to the dissolution solution and performing a quenching treatment.

[0075] The above limitation requires that the amount of lithium sulfide coarse powder added in the dissolution stage be large enough to ensure that the required lithium sulfide microcrystalline powder can be precipitated after adding a second organic solvent and performing a quenching treatment in the subsequent process. This is to ensure the yield and quality of the final product that can be obtained.

[0076] Furthermore, the addition amount of the target lithium sulfide coarse powder in the first organic solvent is not less than the amount corresponding to the maximum solubility of lithium sulfide in the first organic solvent under the heating condition.

[0077] The above limitation requires that under the heating condition, the amount of lithium sulfide coarse powder added should reach or exceed the maximum solubility of lithium sulfide in the first organic solvent. This is to ensure that the solution can reach a saturated state and provide a sufficient solute basis for the subsequent precipitation process.

[0078] Herein, not less than means that the addition amount of the lithium sulfide coarse powder cannot be lower than the amount corresponding to the maximum solubility of lithium sulfide in the first organic solvent under a specific heating condition. The addition amount can either reach or exceed this solubility limit.

[0079] By adding the target lithium sulfide coarse powder equal to or exceeding the maximum solubility of the first organic solvent at a specific temperature (heating temperature), a supersaturated solution can be formed. The solution in this state contains more solutes, providing a greater material basis for the subsequent crystallization process. A supersaturated solution is more likely to induce crystallization because the solute concentration in the solution exceeds the equilibrium solubility, which helps to quickly form lithium sulfide crystals.

[0080] It should be noted that in the method of quenching treatment and inducing precipitation of crystals, the dissolution solution is more likely to form microcrystals due to its high solute concentration. When the dissolution solution cools, the solubility of the solute decreases, rapidly leading to a state close to saturation and exceeding the solubility critical point to reach a supersaturated state, which promotes the aggregation of solute molecules to form crystal nuclei, thus accelerating the growth of crystals. Controlling the cooling rate can precisely regulate the crystallization rate and the size of microcrystals, making the crystallization process more uniform and efficient. In addition, the high concentration of solutes helps to reduce the influence of impurities and improve the purity of the final product. Therefore, the saturated solution not only improves the crystallization efficiency in the method of quenching treatment and precipitating microcrystals, but also helps to obtain microcrystals with a uniform particle size distribution and high purity, which is crucial for preparing materials with specific performance requirements.

[0081] In this embodiment, by forming a dissolution solution, this method can increase the amount of lithium sulfide microcrystals that can precipitate out in a unit volume of the solution, thereby potentially increasing the yield of the product. By finely adjusting the cooling rate of the supersaturated solution and the conditions of solid-liquid separation, the crystallization rate and the particle size of the final product can be controlled, and further, the product performance such as conductivity and mechanical strength can be optimized. In addition, the solid-liquid separation step can effectively remove the undissolved lithium sulfide precipitate, simplifying the subsequent purification step because most of the purification work has been completed during the crystallization process. This technical solution also provides flexibility, allowing the process parameters to be adjusted to meet different production requirements and optimize the product characteristics. At the same time, by increasing the amount of lithium sulfide added, the dissolution capacity of the first organic solvent can be more fully utilized, reducing the amount of solvent used and lowering the cost. Therefore, adding an excessive amount of lithium sulfide coarse powder to form a supersaturated solution and then removing the undissolved precipitate by solid-liquid separation is an effective technical solution for increasing the yield, controlling the crystallization process, and optimizing the performance of the final product, and is widely used in industrial crystallization processes that require products with high purity and a specific particle size distribution.

[0082] Further, under heating conditions, the target lithium sulfide coarse powder added to the first organic solvent for mixing should be such that the first organic solvent can no longer dissolve the newly added target lithium sulfide coarse powder, so as to obtain a saturated mixture.

[0083] The above limitation requires that in actual operation, lithium sulfide coarse powder is continuously added until the first organic solvent can no longer dissolve more lithium sulfide, thereby obtaining a saturated mixture. The above limitation is to determine the critical point of the dissolution of lithium sulfide by the first organic solvent under heating conditions by continuously adding the target lithium sulfide powder, in order to ensure the sufficiency of the dissolution process and the saturation of the solution.

[0084] For example, taking anhydrous ethanol as an example, assume that under the condition of heating to 60 °C, lithium sulfide coarse powder is started to be added to 1 liter of anhydrous ethanol, with 50 grams added each time. When adding for the 4th time (a total of 200 grams), it is found that the newly added lithium sulfide coarse powder no longer dissolves, that is, the solvent has reached a saturated state. At this time, the addition is stopped to obtain a saturated mixture. If lithium sulfide coarse powder continues to be added, not only will it not dissolve, but it may also cause the solution to become turbid or affect the subsequent precipitation process.

[0085] Further, before adding the second organic solvent to the dissolution solution, it further includes:

[0086] Performing a precooling treatment on the second organic solvent; wherein, the temperature of the precooling treatment is not lower than the freezing point of the second organic solvent.

[0087] In the above steps, the pre-cooled second organic solvent is added to the saturated solution containing lithium sulfide, and rapid cooling (quenching treatment) is carried out to induce the rapid precipitation of lithium sulfide microcrystals, thereby obtaining a microcrystalline mixed solution containing lithium sulfide microcrystals.

[0088] As described above, the pre-cooled second organic solvent can rapidly reduce the temperature of the microcrystalline mixed solution, thereby rapidly inducing the crystallization of lithium sulfide, which helps to control the crystallization rate and particle size. The pre-cooling treatment can increase the supersaturation of the solution, promote the rapid crystallization of lithium sulfide, and improve the crystallization efficiency.

[0089] In some embodiments, the temperature of the quenching treatment is not lower than the freezing point of the solution after mixing the saturated solution and the second organic solvent.

[0090] First of all, if the temperature of the pre-cooling treatment of the second organic solvent is lower than its freezing point, the solvent will solidify into a solid state and the mixing and crystallization induction processes cannot be carried out. Keeping the temperature condition of the pre-cooling treatment above the freezing point of the second organic solvent can ensure that it remains in a liquid state, so that it can effectively mix with the lithium sulfide saturated solution and induce crystallization.

[0091] Through the pre-cooling treatment, the temperature of the microcrystalline mixed solution can be rapidly reduced, thereby controlling the crystallization rate of lithium sulfide and avoiding uneven particle size of the product caused by too fast crystallization.

[0092] The reason why the temperature of the quenching treatment is not lower than the freezing point of the mixed solution is that if the temperature of the quenching treatment is lower than the freezing point of the mixed solution, the solution may freeze, which will interrupt the crystallization process and affect the quality and yield of the product. Keeping the temperature above the freezing point ensures that the solution remains in a liquid state, which is convenient for processing and operation, and also helps to maintain the continuity of the crystallization process. By controlling the temperature near the freezing point, the supersaturation of the solution can be increased, promoting the crystallization of lithium sulfide, while avoiding too slow or incomplete crystallization due to too low temperature. In addition, appropriate temperature control helps to form uniform crystals and avoid uneven crystal growth or defects caused by too low temperature.

[0093] In summary, the temperature conditions of pre-cooling and quenching are to ensure that the crystallization step can be carried out under the best conditions during the modification process of lithium sulfide powder, so as to obtain high-quality lithium sulfide microcrystalline powder. By precisely controlling the temperature, the crystallization process can be optimized, the purity and performance of the product can be improved, and at the same time, the safety and controllability of the process are ensured.

[0094] In some embodiments, the cooling medium for the pre-cooling treatment and / or the quenching treatment includes at least one of water, heat transfer oil, dry ice, and liquid nitrogen.

[0095] In some embodiments, the cooling rate of the quenching treatment is not lower than 20 °C / s and not higher than 50 °C / s.

[0096] As described above, the cooling rate has a significant impact on the crystallization behavior of lithium sulfide microcrystals. An excessively fast cooling rate may lead to the formation of overly fine microcrystals, while an overly slow cooling rate may result in overly large crystal growth. Within the cooling rate range of 20 °C / s to 50 °C / s, the formation of uniform and appropriately sized microcrystals can be promoted, which is crucial for the final properties of the material. At a controlled cooling rate, the incorporation of impurities can be reduced, maintaining the high purity of the product. Excessive cooling may cause impurities to be encapsulated in the crystals, while slow cooling may cause impurities to redistribute during crystal growth.

[0097] In addition, the selection of the cooling rate is also related to energy consumption. An excessively fast cooling rate may require more energy input, while an appropriate cooling rate can balance energy efficiency and process requirements.

[0098] In some embodiments, in step S2, a second organic solvent is added to the dissolution solution, and a quenching treatment is performed to obtain precipitated lithium sulfide microcrystal powder, including:

[0099] Step S21, adding the second organic solvent to the dissolution solution and performing a quenching treatment to obtain a microcrystal mixture solution in which microcrystals are precipitated.

[0100] Step S22, performing a solid-liquid separation treatment on the microcrystal mixture solution to obtain a microcrystal precursor.

[0101] After the quenching treatment, the microcrystal mixture solution will contain microcrystals of lithium sulfide and the remaining solvent. The solid-liquid separation treatment aims to remove these solvents, leaving behind the lithium sulfide microcrystal precursor.

[0102] Solid-liquid separation can significantly improve the purity of the product, remove the excess solvent, and prepare for the subsequent heat treatment step.

[0103] Specifically, solid-liquid separation can be achieved through centrifugation and / or filtration treatment. These are common physical separation techniques that can effectively remove the solvent.

[0104] Step S23, performing a heat treatment on the microcrystal precursor to obtain the lithium sulfide microcrystal powder.

[0105] As described above, the solid-liquid separation treatment is used to separate the precipitated microcrystal precursor solid from the solution, and solid-liquid separation can be performed by means such as filtration, suction filtration, and centrifugation.

[0106] As described above, during the heat treatment of the microcrystal precursor, the remaining solvent is further removed, and at the same time, some heat-induced physical or chemical changes may occur to improve the properties of the powder, so that pure lithium sulfide microcrystal powder can be obtained.

[0107] Heat treatment can ensure the purity of the powder, remove all residual solvents, and prevent chemical reactions or physical instabilities in subsequent applications.

[0108] In some embodiments, the solid-liquid separation treatment includes centrifugation and / or filtration.

[0109] In some embodiments, the atmosphere of the heat treatment includes an inert gas atmosphere and / or vacuum. Here, the inert gas is a gas that does not affect the recrystallization of lithium sulfide. For example, it may include, but is not limited to, helium, neon, argon, etc.

[0110] In some embodiments, the temperature of the heat treatment is 200°C to 700°C. For example, the temperature can be 200°C, 300°C, 500°C, 600°C, 700°C, etc.

[0111] The heat treatment can be carried out in an inert gas atmosphere or in a vacuum to prevent oxidation or other unwanted side reactions. The temperature is controlled between 200°C and 700°C to ensure the effective removal of the solvent and the optimization of the powder properties.

[0112] In some embodiments, the first organic solvent is a solvent that is highly soluble or extremely soluble in lithium sulfide; the second organic solvent is a solvent that is poorly soluble or insoluble in lithium sulfide.

[0113] The first organic solvent is highly soluble or extremely soluble in lithium sulfide, which helps to better form a solution, and the second organic solvent is poorly soluble or insoluble in lithium sulfide, which helps the crystallization of lithium sulfide.

[0114] As mentioned above, "highly soluble" means that a substance can dissolve in another substance in a relatively large amount. Generally, if the solubility of a substance in a solvent reaches or exceeds 1 g / 100 mL at room temperature, it can be considered highly soluble.

[0115] As mentioned above, "extremely soluble" means that a substance can dissolve in another substance in a very large amount. Generally, if the solubility of a substance in a solvent is much greater than 1 g / 100 mL, it can be considered extremely soluble.

[0116] As mentioned above, "poorly soluble" means that a substance can only dissolve in another substance in a relatively small amount. Generally, if the solubility of a substance in a solvent is less than 1 g / 100 mL at room temperature, it can be considered poorly soluble.

[0117] As mentioned above, "insoluble" means that a substance can hardly dissolve in another substance. Generally, if the solubility of a substance in a solvent is very low and can be almost ignored, it can be considered insoluble.

[0118] In this embodiment, the first organic solvent that is easily soluble or extremely soluble in lithium sulfide is selected to ensure that lithium sulfide can be fully dissolved to form a dissolution solution; while the second organic solvent that is poorly soluble or insoluble in lithium sulfide is selected to promote the precipitation of lithium sulfide in subsequent steps, so as to achieve the purpose of purification and particle size control.

[0119] In some embodiments, the first organic solvent is a solvent that is easily soluble or extremely soluble in lithium sulfide and poorly soluble or insoluble in impurity substances other than lithium sulfide.

[0120] The lithium sulfide crude powder is added to the first organic solvent, and lithium sulfide can be completely dissolved under certain conditions (such as heating and stirring) to form a uniform saturated dissolution solution, thereby obtaining a dissolution solution of lithium sulfide. Among them, the first organic solvent is required to have the following properties: (1) It is easily soluble or extremely soluble in lithium sulfide. (2) It is a solvent that is poorly soluble or insoluble in impurity substances other than lithium sulfide in the target lithium sulfide crude powder. Among them, the impurity substances may include at least one of lithium sulfate, lithium carbonate, and lithium hydroxide.

[0121] In this embodiment, using the first organic solvent that is easily soluble or extremely soluble in lithium sulfide can ensure the high solubility of lithium sulfide, laying a foundation for subsequent purification and particle size control; moreover, the poor solubility or insolubility of the first organic solvent in impurity substances such as lithium sulfate, lithium carbonate, and lithium hydroxide can achieve one-step purification through the addition of the first organic solvent and the solvent step, greatly reducing the entry of impurities into the obtained saturated dissolution solution and improving the purity of the final product.

[0122] Specifically, it can be achieved through a simple dissolution process, and the temperature and stirring speed need to be controlled to optimize the dissolution efficiency.

[0123] In some embodiments, the solubility of the first organic solvent in lithium sulfide at room temperature is not less than 1 wt%; the solubility of the second organic solvent in lithium sulfide at room temperature is not higher than 0.05 wt%.

[0124] In some embodiments, the first organic solvent includes at least one of methanol, ethanol, propanol, acetone, acetonitrile, ethylene glycol, aniline, and N-methylpyrrolidone;

[0125] In some embodiments, the second organic solvent is at least one of an ether solvent, a ketone solvent, and an alkane solvent.

[0126] As described above, in the second organic solvent, it can be a weakly polar and low-boiling solvent such as an ether, a ketone, or an alkane that is poorly soluble or insoluble in lithium sulfide, and it can be a single solvent or a mixed solvent of multiple different solvents.

[0127] For example, ether solvents can be dimethyl ether, diethyl ether; ketone solvents can be acetone, methyl ethyl ketone, cyclohexanone, etc.; alkane solvents can be pentane, hexane, heptane, octane, and so on.

[0128] Furthermore, the addition amount of the target lithium sulfide coarse powder in the first organic solvent is not less than the amount corresponding to the maximum solubility of lithium sulfide in the first organic solvent at the heating temperature.

[0129] In addition, an embodiment of the present application also provides a lithium sulfide microcrystalline powder body, which is prepared by the modification method of the lithium sulfide powder body in the above-described embodiment.

[0130] In addition, an embodiment of the present application also provides a solid electrolyte, including the lithium sulfide microcrystalline powder body as described in the above embodiment.

[0131] In addition, an embodiment of the present application also provides a battery, including a solid electrolyte; the solid electrolyte includes the lithium sulfide microcrystalline powder body as described in the above embodiment.

[0132] In addition, an embodiment of the present application also provides an electricity-related device, including the battery as described in the above embodiment.

[0133] The above electricity-related device may include, but is not limited to, the following types:

[0134] (1) Portable electronic devices: such as smart phones, tablet computers, laptop computers, cameras, music players, etc.

[0135] (2) Wearable devices: such as smart watches, health trackers, virtual reality helmets, etc.

[0136] (3) Household appliances: such as vacuum cleaners, rice cookers, refrigerators, washing machines, air conditioners, microwave ovens, etc.

[0137] (4) Personal care devices: such as electric toothbrushes, razors, hair dryers, massagers, etc.

[0138] (5) Power tools: such as electric drills, electric saws, sanders, cutting machines, etc.

[0139] (6) Electric vehicles: including battery electric vehicles (BEV), plug-in hybrid electric vehicles (PHEV), and hybrid electric vehicles (HEV).

[0140] (7) Electric bicycles and electric scooters: Electric transportation tools for short-distance travel and commuting.

[0141] (8) Drones: Remote-controlled or autonomous flying devices for purposes such as photography, monitoring, and logistics distribution.

[0142] (9) Medical devices: such as cardiac pacemakers, hearing aids, medical monitoring devices, etc.

[0143] (10) Industrial equipment: such as automated production lines, robots, control systems, etc.

[0144] (11) Communication base stations: for power supply of mobile phone networks and other wireless communication networks.

[0145] (12) Solar energy storage systems: used to store electrical energy generated by solar power for emergencies.

[0146] (13) Emergency power and backup power systems: such as uninterruptible power supplies (UPS) and emergency lighting systems.

[0147] (14) Energy storage power stations: large-scale energy storage systems for balancing grid loads and storing renewable energy.

[0148] These electrical equipment usually require batteries as the energy source. In the embodiments of the present application, due to its high capacity and good cycle stability, the battery can be widely applied to the above-mentioned equipment to provide persistent and reliable power support.

[0149] The present invention will be further described below through specific embodiments. However, it should be understood that these embodiments are only for more detailed description and should not be construed as limiting the present invention in any form.

[0150] Table 1. Parameter comparison table in each embodiment

[0151] Item Example 1 Example 2 Example 3 Example 4 Example 5 First organic solvent Absolute ethanol Absolute ethanol Absolute ethanol Absolute ethanol Isopropyl alcohol anhydrous Heating temperature °C 60 60 40 60 70 Second organic solvent Hexane Hexane Hexane Hexane n-Heptane Pre-cooling treatment temperature °C -10 0 -10 0 -30 Cooling medium Silicone oil Silicone oil Silicone oil Silicone oil Silicone oil Quenching treatment temperature °C -20 0 -20 0 -30 Heat treatment atmosphere Vacuum Vacuum Vacuum Argon Vacuum

[0152] In Table 1, the heating temperature is the temperature when the first organic solvent is heated and stirred in step (1) of the experimental method of the embodiment.

[0153] Example 1

[0154] In this embodiment, modification treatment of lithium sulfide coarse powder is carried out.

[0155] Experimental method:

[0156] (1) The target lithium sulfide coarse powder containing impurities is added to 100 mL of absolute ethanol (the first organic solvent) in portions, heated to 60 °C, and stirred for 1 hour until the newly added lithium sulfide coarse powder can no longer dissolve, obtaining a mixed solution of lithium sulfide containing insoluble impurities.

[0157] (2) Using a filter with a heating jacket, under the condition of maintaining the temperature at 60 °C, the above solution is hot-filtered to remove insoluble impurities, obtaining a saturated solution of lithium sulfide.

[0158] (3) Add hexane (the second organic solvent) that has been pre-cooled to -10 °C in silicone oil (pre-cooling treatment) to the above-mentioned saturated solution. While stirring at 500 rpm, immerse the mixed system in silicone oil (medium) at -20 °C for rapid cooling (quenching treatment) to rapidly precipitate lithium sulfide microcrystals and obtain a microcrystal mixed solution;

[0159] (4) Filter the above microcrystal mixed solution to obtain a microcrystal precursor.

[0160] (5) Heat-treat the microcrystal precursor under vacuum conditions at 500 °C for 2 hours to remove the residual solvent and obtain lithium sulfide microcrystal powder.

[0161] Example 2

[0162] In this example, modification treatment of the lithium sulfide coarse powder was carried out.

[0163] Experimental method: The method in this example is basically the same as that in Example 1. The differences are referred to the parameters in Table 1.

[0164] Example 3

[0165] In this example, modification treatment of the lithium sulfide coarse powder was carried out.

[0166] Experimental method: The method in this example is basically the same as that in Example 1. The differences are referred to the parameters in Table 1.

[0167] Example 4

[0168] In this example, modification treatment of the lithium sulfide coarse powder was carried out.

[0169] Experimental method: The method in this example is basically the same as that in Example 1. The differences are referred to the parameters in Table 1.

[0170] Example 5

[0171] In this example, modification treatment of the lithium sulfide coarse powder was carried out.

[0172] Experimental method: The method in this example is basically the same as that in Example 1. The differences are referred to the parameters in Table 1.

[0173] Horizontal test experiment and results:

[0174] Test method:

[0175] For the final products prepared in the implementation, the following tests were carried out respectively:

[0176] (1) Use an X-ray powder diffractometer to test the phase purity of the material;

[0177] (2) Use a laser particle size analyzer to test the particle size of the material;

[0178] (3) Calculate the yield based on the feeding amount of lithium sulfide coarse powder and the mass of lithium sulfide microcrystalline powder.

[0179] Test results:

[0180] Reference Figure 1 , which is the XRD pattern of the lithium sulfide microcrystalline powder obtained in Example 1. Figure 2 It is the XRD pattern of the lithium sulfide microcrystalline powder obtained in Example 2.

[0181] Table 2. Lithium sulfide particle size and product yield in different examples

[0182] Example <![CDATA[D 50 > Yield Example 1 2.3 μm 90％ Example 2 4.6 μm 82％ Example 3 5.1 μm 75％ Example 4 6.3 μm 81％ Example 5 6.9 μm 87％

[0183] Analysis: According to the horizontal test results in Table 2, the particle size (D 50 ) and yield of the lithium sulfide microcrystalline powder in different examples can be analyzed, as well as the relationship between these results and different parameters in the examples.

[0184] (1) Lower cooling temperatures (such as -20°C and -30°C) are helpful for forming smaller lithium sulfide microcrystals, while higher cooling temperatures (such as 0°C) lead to an increase in particle size.

[0185] (2) Higher heating temperatures are helpful for the full dissolution and precipitation of lithium sulfide, thereby increasing the yield; heat treatment in a vacuum atmosphere is also helpful for increasing the yield and reducing the influence of impurities.

[0186] (3) In addition, different first organic solvents (such as absolute ethanol and isopropyl alcohol) and second organic solvents (such as hexane and n-heptane) have different effects on the solubility and precipitation process of lithium sulfide, thereby affecting the particle size and yield of the final product.

[0187] Through these analyses, the influence of different process parameters on the preparation process of lithium sulfide microcrystalline powder can be better understood, providing guidance for optimizing the process and improving product quality.

[0188] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements 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 modifying lithium sulfide powder, characterized in that: include: dissolving the target lithium sulfide coarse powder in a first organic solvent to obtain a solution; A second organic solvent is added to the dissolving solution, and a quenching treatment is performed to obtain precipitated lithium sulfide microcrystalline powder; wherein the solubility of the first organic solvent for lithium sulfide is greater than that of the second organic solvent.

2. The method for modifying lithium sulfide powder according to claim 1, characterized in that: The step of dissolving the target lithium sulfide coarse powder in a first organic solvent to obtain a solution comprises: Under heating conditions, adding the target lithium sulfide coarse powder to the first organic solvent and mixing to obtain a mixed solution; Maintaining the heating conditions, performing solid-liquid separation on the mixed liquid to obtain the dissolved liquid; Preferably, the heating temperature of the heating condition is not higher than the boiling point of the first organic solvent.

3. The method for modifying lithium sulfide powder according to claim 2, characterized in that: The amount of the target lithium sulfide coarse powder added is at least sufficient to precipitate the lithium sulfide microcrystalline powder after adding the second organic solvent to the dissolving solution and performing a quenching treatment; Preferably, the amount of the target lithium sulfide coarse powder added to the first organic solvent is not less than the amount of the first organic solvent corresponding to the maximum solubility of lithium sulfide under the heating conditions; Preferably, under heating conditions, the target lithium sulfide coarse powder is added to the first organic solvent until the first organic solvent can no longer dissolve the newly added target lithium sulfide coarse powder, so as to obtain a saturated mixed solution.

4. The method for modifying lithium sulfide powder according to claim 1, characterized in that: Before adding the second organic solvent to the dissolving solution, the method further includes: precooling the second organic solvent; wherein the precooling temperature is not lower than the freezing point of the second organic solvent; and / or, The temperature of the quenching treatment is not lower than the freezing point of the solution obtained by mixing the saturated solution and the second organic solvent; and / or The cooling medium of the pre-cooling treatment and / or the quenching treatment comprises: at least one of water, heat transfer oil, dry ice and liquid nitrogen; and / or, The cooling rate of the quenching treatment is: not less than 20°C / s; and not more than 50°C / s.

5. The method for modifying lithium sulfide powder according to claim 1, characterized in that: The step of adding a second organic solvent to the dissolving solution and performing a quenching treatment to obtain precipitated lithium sulfide microcrystalline powder comprises: adding the second organic solvent to the dissolving solution, and performing a quenching treatment to obtain a microcrystalline mixed solution from which microcrystals are precipitated; Performing solid-liquid separation on the microcrystal mixed solution to obtain a microcrystal precursor; heat-treating the microcrystalline precursor to obtain the lithium sulfide microcrystalline powder; Preferably, the solid-liquid separation process comprises centrifugation and / or filtration; Preferably, the atmosphere of the heat treatment includes an inert gas atmosphere and / or a vacuum; Preferably, the heat treatment temperature is 200°C to 700°C.

6. The method for modifying lithium sulfide powder according to claim 1, characterized in that: The first organic solvent is a solvent that is easily soluble or very soluble in lithium sulfide; the second organic solvent is a solvent that is poorly soluble or insoluble in lithium sulfide; Preferably, the first organic solvent is a solvent that is easily soluble or very soluble in lithium sulfide and poorly soluble or insoluble in impurities other than lithium sulfide; Preferably, the solubility of the first organic solvent for lithium sulfide at room temperature is not less than 1wt%; the solubility of the second organic solvent for lithium sulfide at room temperature is not more than 0.05wt%; Preferably, the impurity material includes at least one of lithium sulfate, lithium carbonate and lithium hydroxide; Preferably, the first organic solvent comprises at least one of methanol, ethanol, propanol, acetone, acetonitrile, ethylene glycol, aniline and N-methylpyrrolidone; Preferably, the second organic solvent is at least one of an ether solvent, a ketone solvent and an alkane solvent.

7. A lithium sulfide microcrystalline powder, characterized in that: The method is prepared by the modification method of lithium sulfide powder as described in any one of claims 1 to 6.

8. A solid electrolyte, characterized in that Comprising the lithium sulfide microcrystalline powder as described in claim 7.

9. A battery, characterized in that: Comprising the solid electrolyte as claimed in claim 8.

10. An electrical equipment, characterized in that: Comprising the battery as claimed in claim 9.

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