Liquid-phase synthesis method of lithium sulfide, sulfide-based solid electrolyte and lithium ion battery

Abstract

The embodiment of the invention discloses a liquid-phase synthesis method of lithium sulfide, sulfide-based solid electrolyte and a lithium ion battery, the method comprises the following steps: preparing lithium chloride and sulfur salt into a first suspension containing lithium hydrosulfide, and filtering to obtain a first lithium hydrosulfide solution; the first lithium hydrosulfide solution is cooled at the first temperature, crystals can be separated out from the second lithium hydrosulfide solution, meanwhile, the solubility of the solution is further reduced through separated-out water, impurity ions are further separated out, the impurity ions in the second lithium hydrosulfide solution are effectively reduced, and the lithium hydrosulfide solution is more stable in performance. Therefore, low impurity content in subsequently prepared lithium sulfide is ensured.

Description

Technical Field

[0001] This application relates to the technical field of battery material preparation, specifically to a liquid-phase synthesis method for lithium sulfide, a sulfide-based solid electrolyte, and a lithium-ion battery. Background Technology

[0002] Lithium sulfide (Li2S), as an important inorganic lithium compound, is a key precursor material for the preparation of sulfide-based solid electrolytes and is widely used in high-energy-density and high-safety next-generation energy storage devices such as all-solid-state lithium-ion batteries.

[0003] Sulfide-based solid electrolytes (such as the Li2S-P2S5 system) have advantages such as high ionic conductivity, wide electrochemical window and good compatibility with electrode materials, and have been actively used in all-solid-state batteries in recent years.

[0004] However, lithium sulfide does not have a natural mineral source in nature and must be prepared through synthetic methods. The uniformity of its morphology and the content of impurities directly affect the battery performance. Summary of the Invention

[0005] This application provides a liquid-phase synthesis method for lithium sulfide, a sulfide-based solid electrolyte, and a lithium-ion battery, aiming to ensure that the synthesized lithium sulfide has a low impurity content.

[0006] This application provides a liquid-phase synthesis method for lithium sulfide, comprising the following steps: Lithium chloride and sulfur salts were used to prepare a first suspension containing lithium hydrosulfide, and the first lithium hydrosulfide solution was obtained by filtration. The first lithium hydrosulfide solution was cooled at a first temperature and filtered to obtain a second lithium hydrosulfide solution. The second lithium hydrosulfide solution was desulfurized under an inert atmosphere and filtered to obtain the lithium sulfide.

[0007] Optionally, in some embodiments of this application, the step of preparing a first suspension containing lithium hydrosulfide from lithium chloride and sulfur salt includes: Lithium chloride is dissolved in an organic solvent to obtain a lithium chloride solution; A sulfur salt is added to the lithium chloride solution, and the reaction is carried out at a second temperature. The solution is then filtered to obtain a first suspension containing lithium hydrosulfide. The second temperature is higher than the first temperature.

[0008] Optionally, in some embodiments of this application, the first temperature ranges from -20°C. o C to 10 o C; and / or The second temperature range is 50. o C to 140 o C.

[0009] Optionally, in some embodiments of this application, the organic solvent includes polar aprotic organic solvents; The polar aprotic organic solvents include at least one of dimethyl sulfoxide, dimethylformamide, N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropionamide, N-alkylcaprolactam, and N-alkylpyrrolidone.

[0010] Optionally, in some embodiments of this application, the first lithium hydrosulfide solution is cooled at a first temperature to obtain a second suspension; The second suspension comprises chloride-containing crystals and a lithium hydrosulfide solution; and / or The second lithium hydrosulfide solution is desulfurized under an inert atmosphere to obtain a third suspension, which includes lithium sulfide, lithium chloride solution and lithium hydrosulfide solution.

[0011] Optionally, in some embodiments of this application, the molar ratio of lithium chloride to sulfur salt ranges from 1 to 1.5; and / or The sulfur salts include hydrosulfide salts; The hydrosulfide salt includes at least one of potassium hydrosulfide and sodium hydrosulfide.

[0012] Optionally, in some embodiments of this application, the desulfurization temperature is 150°C. o C to 200 o C; and / or The desulfurization time is from 0.5 h to 20 h.

[0013] Optionally, in some embodiments of this application, the lithium sulfide is a single crystal particle; and / or The D50 particle size of the lithium sulfide ranges from 7 μm to 8 μm; and / or The lithium sulfide contains a metal base content of greater than 99.92% and an impurity ion content of less than 200 ppm.

[0014] Accordingly, this application also provides a sulfide-based solid electrolyte, which is prepared by the liquid-phase synthesis method of lithium sulfide as described above.

[0015] In addition, this application also provides a lithium-ion battery, which includes a sulfide-based solid electrolyte as described above.

[0016] The synthesis method of this application embodiment includes preparing a first suspension containing lithium hydrosulfide from lithium chloride and sulfur salt, filtering to obtain a first lithium hydrosulfide solution; cooling the first lithium hydrosulfide solution at a first temperature helps to precipitate crystals from the second lithium hydrosulfide solution, while the precipitation of some water further reduces the solubility of the solution, significantly reducing impurity ions in the second lithium hydrosulfide solution, thereby ensuring that the impurity content in the subsequently prepared lithium sulfide is low. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of the synthesis method provided by an exemplary embodiment of this disclosure; Figure 2 This is a schematic diagram of a cycle of the synthesis method provided by an exemplary embodiment of this disclosure; Figure 3 This is an XRD pattern of lithium sulfide provided in an exemplary embodiment of this disclosure; Figure 4 This is a SEM image of lithium sulfide provided in an exemplary embodiment of this disclosure. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] The commonly used methods for industrial synthesis of lithium sulfide mainly include the following: 1. Carbothermic reduction method: Lithium sulfate and carbon are reacted at high temperature to produce lithium sulfide and carbon dioxide. Although this method is relatively mature, it has high reaction temperature and high energy consumption, and the product often contains impurities such as carbon, oxygen, and sulfur with a wide particle size distribution, making it difficult to meet the high purity requirements of battery-grade products. 2. The method of directly reacting metallic lithium with elemental sulfur under mechanical ball milling conditions to produce lithium sulfide is simple, but it is prone to local overheating, combustion or even explosion during the reaction, resulting in poor safety; moreover, the reaction is incomplete, the conversion rate and yield are low, the product consistency is poor, and it is difficult to scale up production. 3. Metathesis method: Lithium sulfide is usually prepared by metathesis reaction of lithium chloride and sodium sulfide in water or organic solvent. This method has mild reaction conditions, but often results in a large amount of residual sodium ions and low product purity. 4. Gas-solid reaction method: This method involves reacting lithium hydroxide or lithium carbonate with hydrogen sulfide gas at high temperatures. While this method can yield high-purity lithium sulfide, the raw material, hydrogen sulfide gas, is highly toxic and corrosive.

[0021] In view of this, embodiments of this application provide a liquid-phase synthesis method for lithium sulfide, a sulfide-based solid electrolyte, and a lithium-ion battery, aiming to ensure that the synthesized lithium sulfide has a low impurity content.

[0022] According to a first aspect of the embodiments of this application, a liquid-phase synthesis method for lithium sulfide is provided. Please refer to [link to relevant documentation]. Figure 1 It includes the following steps: S100. Prepare a first suspension containing lithium hydrosulfide by lithium chloride and sulfur salt, and filter to obtain a first lithium hydrosulfide solution. S200: Cool the first lithium hydrosulfide solution at the first temperature and filter to obtain the second lithium hydrosulfide solution; S300: The second lithium hydrosulfide solution is desulfurized under an inert atmosphere and filtered to obtain lithium sulfide.

[0023] By adopting the above scheme, the method includes preparing a first suspension containing lithium hydrosulfide from lithium chloride and sulfur salt, filtering to obtain a first lithium hydrosulfide solution; cooling the first lithium hydrosulfide solution at a first temperature, cooling and crystallizing to precipitate crystals containing water and impurity ions, while the precipitated water will further reduce the solubility of the solution, effectively reducing the impurity ions in the second lithium hydrosulfide solution, thereby ensuring that the impurity content in the subsequently prepared lithium sulfide is low.

[0024] In some embodiments of this application, the step of preparing a first suspension containing lithium hydrosulfide from lithium chloride and sulfur salt includes: Lithium chloride is dissolved in an organic solvent to obtain a lithium chloride solution; A sulfide salt is added to a lithium chloride solution, and the reaction is carried out at a second temperature. The solution is then filtered to obtain a first suspension containing lithium hydride; wherein the second temperature is higher than the first temperature.

[0025] By adopting the above scheme, lithium chloride is first dissolved in an organic solvent to form a homogeneous and stable lithium chloride solution. Then, a sulfur salt is added to react at a second temperature to generate a first suspension containing lithium hydride. Filtration can then remove the insoluble byproducts (inorganic salt precipitates insoluble in organic solvents) generated in the reaction. This step can significantly reduce the content of impurity ions, thereby ensuring the high purity of the subsequent products.

[0026] In some embodiments of this application, the first temperature ranges from -20°C. o C to 10 o C. Furthermore, the range of the first temperature is -10. o C to 10 o C. For example, the first temperature can be -20°C. o C, -15 o C, -10 o C, -5 o C, 0 o C, 5 o C, 10 o C and any value between the two adjacent values ​​mentioned above.

[0027] By adopting the above scheme, the first temperature is set in a lower temperature range, which promotes the precipitation of chloride salts that are insoluble in organic solvents in the form of crystals. These crystals are superior to the common ion effect during the crystallization process, which is conducive to the precipitation of impurity ions in the form of crystals, thereby achieving the effect of removing most of the water and most of the impurity ions.

[0028] In some embodiments of this application, the second temperature ranges from 50°C. o C to 140 o C. Furthermore, the range of the second temperature is 60. o C to 130 o C. For example, the second temperature can be 50. o C, 60 o C, 70 o C, 80 o C, 90 o C, 100 o C, 110 o C, 120 o C, 130 o C, 140 o C and any value between the two adjacent values ​​mentioned above.

[0029] By employing the above scheme, maintaining the second temperature within the aforementioned range is beneficial for breaking ionic bonds, promoting ion exchange, and generating lithium hydrosulfide. The second temperature should not be too high, as this will make lithium hydrosulfide unstable and decompose into lithium sulfide and hydrogen sulfide. The reaction temperature should be controlled at 140°C. o Below a certain temperature, lithium hydrosulfide can be effectively inhibited from decomposing prematurely during the reaction stage, ensuring that lithium hydrosulfide remains stably present in the first suspension.

[0030] In some embodiments of this application, a first lithium hydrosulfide solution is cooled at a first temperature to obtain a second suspension; wherein the second suspension comprises chloride-containing crystals and a lithium hydrosulfide solution.

[0031] By adopting the above scheme, the first lithium hydrosulfide solution contains a small amount of chloride (containing impurity ions). Cooling the first lithium hydrosulfide solution at the first temperature reduces its solubility, and the chloride precipitates out as crystals. At the same time, water molecules also precipitate out of the crystals, further reducing the solubility of the chloride. This step effectively removes impurities, thereby ensuring the content of salt ions (i.e., impurity ions) contained in the chloride in the subsequent product, and thus ensuring the high purity of the subsequent lithium sulfide.

[0032] In some embodiments of this application, the second lithium hydrosulfide solution is desulfurized under an inert atmosphere to obtain a third suspension, which includes lithium sulfide, lithium chloride solution and lithium hydrosulfide solution.

[0033] By adopting the above scheme, the third suspension after desulfurization contains lithium sulfide, lithium chloride solution and lithium hydrosulfide solution, among which lithium sulfide is the core product, and the mixture of lithium chloride solution and lithium hydrosulfide can be recycled as raw material.

[0034] In some embodiments of this application, the organic solvent includes polar aprotic organic solvents.

[0035] By employing the above scheme, polar aprotic organic solvent molecules do not contain transferable active hydrogen, thus avoiding uncontrolled proton exchange reactions between solvent molecules and hydrosulfide ions and preventing the generation of hydrogen sulfide gas. Furthermore, polar aprotic organic solvents possess high dielectric constants and dipole moments, characteristics that enable them to effectively dissolve ionic compounds and promote the ion dissociation of these salts through solvation. Simultaneously, polar aprotic organic solvents can also dissolve lithium hydrosulfide and stabilize the ions within lithium hydrosulfide through their strong solvation shell, preventing hydrolysis, disproportionation, or premature decomposition.

[0036] In some embodiments of this application, the polar aprotic organic solvent includes at least one of dimethyl sulfoxide, dimethylformamide, N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropionamide, N-alkylcaprolactam, and N-alkylpyrrolidone.

[0037] N-Methylpyrrolidone exhibits high solubility for lithium salts, good thermal stability, and relatively low toxicity; dimethyl sulfoxide (DMSO) is highly polar and has outstanding solubility, making it suitable for processes requiring slightly lower desulfurization temperatures; dimethylformamide and N,N-dimethylacetamide possess excellent solubility and moderate boiling points, making them widely applicable; similar to N-alkylcaprolactam and N-alkylpyrrolidone, the solubility, viscosity, and boiling point of the solvent can be adjusted by changing the length of the alkyl chain, allowing for the selection of suitable solvents to meet different needs and promote the optimization of product crystal morphology.

[0038] In some embodiments of this application, the molar ratio of lithium chloride to sulfur salt ranges from 1 to 1.5. Exemplarily, the molar ratio of lithium chloride to sulfur salt can be 1, 1.1, 1.2, 1.3, 1.4, 1.5, or any value between two adjacent values ​​mentioned above.

[0039] By adopting the above scheme, the first lithium hydride solution is obtained by filtration after the reaction of lithium chloride with sulfur salt. When lithium chloride is in excess, there is a high concentration of lithium ions and chloride ions in the reaction system, which helps to inhibit the dissolution of chloride salt (impurity ions) in organic solvent and facilitates the crystallization and precipitation of more impurity ions during subsequent cooling.

[0040] In some embodiments of this application, the sulfur salt includes hydrosulfide salts. It is understood that hydrosulfide salts often exist in a state containing water of crystallization.

[0041] By adopting the above scheme, the sulfide ion in the hydrosulfide salt is a highly reactive sulfur source. Its reaction with lithium ions in lithium chloride in organic solvents is milder and more efficient, and lithium hydrosulfide can be directly generated. The reaction pathway is clear and there are few side reactions.

[0042] In some embodiments of this application, the hydrosulfide salt includes at least one of potassium hydrosulfide and sodium hydrosulfide.

[0043] By adopting the above scheme, potassium hydrosulfide and sodium hydrosulfide are decomposed into potassium chloride or sodium chloride as byproducts. These alkali metal chlorides have low solubility in organic solvents. At the second temperature, potassium chloride or sodium chloride will precipitate out in the form of solid precipitate, so that lithium hydrosulfide can be removed by simple filtration after it is generated.

[0044] In some embodiments of this application, the desulfurization temperature is 150°C. o C to 200 o C. Furthermore, the desulfurization temperature is 170°C. o C to 190 o C. For example, the desulfurization temperature can be 170°C. o C, 175 o C, 180 o C, 185 o C, 190 o C and any value between the two adjacent values ​​mentioned above.

[0045] By adopting the above scheme, lithium hydrosulfide is decomposed into lithium sulfide and hydrogen sulfide. At the above desulfurization temperature, it is beneficial to ensure the decomposition reaction of lithium hydrosulfide. Moreover, the inert atmosphere is also beneficial to promote the forward reaction. At the same time, the inert atmosphere can also carry away the trace amount of hydrogen sulfide gas generated from the reaction system, which is beneficial to obtaining high-purity lithium sulfide.

[0046] In some embodiments of this application, the desulfurization time is from 0.5h to 20h. Further, the desulfurization time is from 1h to 6h. Exemplarily, the desulfurization time can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, or any value between two adjacent values ​​mentioned above.

[0047] In some embodiments of this application, the D50 particle size of lithium sulfide ranges from 7 μm to 8 μm.

[0048] By adopting the above scheme, the D50 particle size distribution of lithium sulfide is narrower and the particle uniformity is higher, which is beneficial to improving the rate performance and cycle stability of lithium sulfide in batteries.

[0049] In some embodiments of this application, lithium sulfide is a single crystal particle.

[0050] In some embodiments of this application, the content of metal base in lithium sulfide is greater than 99.92%, and the content of impurity ions is less than 200 ppm.

[0051] By adopting the above scheme, the lithium sulfide prepared in the embodiments of this application has a low level of impurity ions. These impurity ions can introduce defects into the solid electrolyte, interfere with the lithium ion transport channel, or cause unnecessary side reactions when in contact with the electrode, thereby reducing ionic conductivity, increasing interface impedance, and accelerating battery performance degradation.

[0052] In summary, the liquid-phase synthesis method for lithium sulfide according to the embodiments of this application has the following beneficial effects: 1. The first lithium hydrosulfide solution is cooled at a first temperature and filtered to obtain a second lithium hydrosulfide solution, which significantly reduces the content of impurity ions in the second lithium hydrosulfide solution, thereby reducing the effective content of impurity ions in lithium sulfide during the desulfurization process. The main methods adopted are ① excess lithium chloride, ② cooling.

[0053] Measure ①: Reduce impurity ions based on the common ion effect; Measure ② involves cooling to precipitate crystals (containing water, organic solvent, lithium chloride, and chloride salt), effectively reducing the moisture content and the salt ion content (i.e., impurity ions) of the chloride salt, thus ensuring low impurity content in subsequent products. Furthermore, cooling crystallization primarily reduces the concentration of lithium chloride in the lithium hydrosulfide solution, thereby reducing the chloride ion content in lithium sulfide.

[0054] 2. The lithium sulfide prepared by this method has high crystallinity and a relatively concentrated particle size distribution; 3. A production process for solvent recycling was developed.

[0055] According to a second aspect of the embodiments of this application, a sulfide-based solid electrolyte is provided, which is prepared by the liquid-phase synthesis method of lithium sulfide as described above.

[0056] By adopting the above-described scheme, the sulfide-based solid electrolyte of this application embodiment includes all the beneficial effects of the aforementioned liquid-phase synthesis method of lithium sulfide, which will not be repeated here.

[0057] According to a third aspect of the embodiments of this application, a lithium-ion battery is provided, the lithium-ion battery comprising a sulfide-based solid electrolyte as described above.

[0058] By adopting the above-described scheme, the lithium-ion battery of this application embodiment includes all the beneficial effects of the aforementioned sulfide-based solid electrolyte, which will not be repeated here.

[0059] The present application will be specifically described below through specific embodiments. These embodiments are only some embodiments of the present application and are not intended to limit the present application. Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0060] Example 1 For a liquid-phase synthesis method of lithium sulfide, please refer to [link / reference]. Figure 2 It includes the following steps: S100. Dissolve lithium chloride in an organic solvent (NMP) to obtain a lithium chloride solution; S200. Add sodium hydrosulfide to the lithium chloride solution and heat to 90°C. o C, react for 2 hours to obtain a first suspension containing lithium hydride, the first suspension including a solution containing sodium chloride and lithium hydride; S300. The first suspension is filtered to obtain a first lithium hydrosulfide solution and sodium chloride precipitate; wherein the molar ratio of lithium chloride to sodium hydrosulfide is 1.2. S400, the first lithium hydride solution (containing a small amount of NaCl) is heated at 0... o Cooling at C yields a second suspension, which comprises lithium hydrosulfide solution, NaCl-LiCl-NMP-H2O crystals, and sodium chloride. S500. Filter the second suspension to obtain a second lithium hydrosulfide solution. S600, the second lithium hydride solution is desulfurized under a nitrogen atmosphere at a temperature of 180°C. o C, the desulfurization time is 5 hours, and a third suspension is obtained; wherein, the third suspension includes lithium hydrosulfide solution, lithium chloride solution and lithium sulfide; S700, the third suspension is filtered to obtain lithium sulfide and filtrate; The filtrate can be used as the lithium chloride solution in step S200; lithium sulfide is washed with an organic solvent to obtain lithium sulfide and a washing solution. The washing solution can be recycled as sodium chloride precipitate in step S300 or added to the lithium chloride solution in step S200; wherein the washing temperature is 105°C. o C, time 60 min, washing 3 times, lithium sulfide yield 50%.

[0061] Examples 2 to 3 Except for the first temperature shown in Table 1, the other steps are the same as in Example 1.

[0062] Table 1

[0063] Examples 4 to 5 Except for the second temperature shown in Table 2, the other steps are the same as in Example 1.

[0064] Table 2

[0065] Comparative Example 1 The difference from Example 1 is the absence of the cooling step at the first temperature. The steps in this comparative example include: Lithium chloride was dissolved in N-methylpyrrolidone (NMP) to obtain a lithium chloride solution; Sodium hydrosulfide was added to the lithium chloride solution at 90°C. o The reaction was carried out at temperature C for 2 hours to obtain a first suspension containing lithium hydrosulfide. The first suspension included a solution containing sodium chloride and lithium hydrosulfide. The solution was filtered to obtain the first lithium hydrosulfide solution and sodium chloride precipitate. The molar ratio of lithium chloride to sodium hydrosulfide was 1.2. The first lithium hydrosulfide solution was desulfurized under a nitrogen atmosphere, followed by filtration and washing to obtain lithium sulfide; the desulfurization temperature was 180°C. o C, the desulfurization time is 5 hours; the washing temperature is 105°C. o C, time 60 min, lithium sulfide yield 75%.

[0066] Performance testing: 1. XRD test: Lithium sulfide in the examples and comparative examples was tested by XRD powder diffraction; 2. SEM morphology test: The lithium sulfide of the examples and comparative examples was examined using a scanning electron microscope; 3. D50 particle size: The particle size of lithium sulfide in the examples and comparative examples was tested using a dry laser particle size analyzer. 4. Purity test: ICP was used to test the lithium sulfide in the examples and comparative examples.

[0067] The test results are shown in Table 3. Table 3

[0068] Compared with Comparative Example 1, Examples 1-5 all involved reacting lithium chloride with sodium hydrosulfide and then filtering to obtain a first lithium hydrosulfide solution, followed by cooling and further filtering of the first lithium hydrosulfide solution (containing a small amount of NaCl). In contrast, Comparative Example 1 directly filtered the first lithium hydrosulfide solution without cooling and crystallization. As shown in Table 3, the methods in Examples 1-5, after cooling, precipitated crystals (containing water-NMP-LiCl-NaCl). The precipitation of these crystals removed a large amount of water and sodium chloride, reducing solubility and further precipitating some sodium chloride, thus lowering the impurity content in the subsequent product. This ensured the purity of the subsequent product, lithium sulfide, resulting in a lithium-sulfur ratio close to 2. In contrast, the lithium sulfide in Comparative Example 1 had a significantly higher lithium-sulfur ratio than 2 and a higher impurity content.

[0069] Compared with Examples 1-3, the difference lies in the first temperature. Compared with Example 1, Example 2 lowered the first temperature, while Example 3 increased the first temperature. As shown in Table 3, Example 2 had the lowest first temperature, indicating that Example 2 had the best precipitation effect, resulting in lower sodium ion and other cation content in the final product lithium sulfide, and a lithium-sulfur ratio closest to 2.

[0070] Compared to Examples 1 and 4-5, the difference lies in the second temperature. In Example 4, the second temperature is 60°C, unlike Example 1. o C, the second temperature in Example 5 is 130 o C. As shown in Table 3, the second temperature in Example 4 was too low, resulting in an incomplete reaction and a high impurity content in lithium sulfide. Furthermore, water could not be effectively removed, leading to an increase in the lithium-sulfur ratio. In contrast, the second temperature in Example 5 was too high, potentially causing the decomposition of lithium hydride.

[0071] Figure 3 This is an XRD pattern of lithium sulfide from Example 1 of this application. Figure 3 The presence of fewer impurity peaks indicates that lithium sulfide has high purity; at the same time, the smaller half-width of the diffraction peaks in the figure indicates that lithium sulfide has good crystallinity.

[0072] Figure 4 This is a SEM image of lithium sulfide from Example 1 of this application. Figure 4 It can be seen that lithium sulfide is distributed relatively evenly and the particle size is relatively uniform.

[0073] The above provides a detailed description of a liquid-phase synthesis method for lithium sulfide, a sulfide-based solid electrolyte, and a lithium-ion battery provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A liquid-phase synthesis method for lithium sulfide, characterized in that, Includes the following steps: Lithium chloride and sulfur salts were used to prepare a first suspension containing lithium hydrosulfide, and the first lithium hydrosulfide solution was obtained by filtration. The first lithium hydrosulfide solution was cooled at a first temperature and filtered to obtain a second lithium hydrosulfide solution. The second lithium hydrosulfide solution was desulfurized under an inert atmosphere and filtered to obtain the lithium sulfide.

2. The liquid-phase synthesis method for lithium sulfide according to claim 1, characterized in that, The steps of preparing a first suspension containing lithium hydrosulfide from lithium chloride and sulfur salts include: Lithium chloride is dissolved in an organic solvent to obtain a lithium chloride solution; A sulfur salt is added to the lithium chloride solution, and the reaction is carried out at a second temperature to obtain a first suspension containing lithium hydrosulfide; wherein the second temperature is higher than the first temperature.

3. The liquid-phase synthesis method for lithium sulfide according to claim 2, characterized in that, The first temperature range is -20°C. o C to 10 o C; and / or The second temperature range is 50. o C to 140 o C.

4. The liquid-phase synthesis method for lithium sulfide according to claim 2, characterized in that, The organic solvents include polar aprotic organic solvents; The polar aprotic organic solvents include at least one of dimethyl sulfoxide, dimethylformamide, N,N-dimethylacetamide, 3-methoxy-N,N-dimethylpropionamide, N-alkylcaprolactam, and N-alkylpyrrolidone.

5. The liquid-phase synthesis method for lithium sulfide according to claim 1, characterized in that, The first lithium hydrosulfide solution was cooled at a first temperature to obtain a second suspension; The second suspension comprises chloride-containing crystals and a lithium hydrosulfide solution; and / or The second lithium hydrosulfide solution is desulfurized under an inert atmosphere to obtain a third suspension, which includes lithium sulfide, lithium chloride solution and lithium hydrosulfide solution.

6. The liquid-phase synthesis method for lithium sulfide according to claim 1, characterized in that, The molar ratio of lithium chloride to sulfur salt ranges from 1 to 1.5; and / or The sulfur salts include hydrosulfide salts; The hydrosulfide salt includes at least one of potassium hydrosulfide and sodium hydrosulfide.

7. The liquid-phase synthesis method for lithium sulfide according to claim 1, characterized in that, The desulfurization temperature is 150°C. o C to 200 o C; and / or The desulfurization time is from 0.5 h to 20 h.

8. The liquid-phase synthesis method for lithium sulfide according to claim 1, characterized in that, The lithium sulfide is a single crystal particle; and / or The D50 particle size of the lithium sulfide ranges from 7 μm to 8 μm; and / or The lithium sulfide contains a metal base content of greater than 99.92% and an impurity ion content of less than 200 ppm.

9. A sulfide-based solid electrolyte, characterized in that, The sulfide-based solid electrolyte is prepared using the liquid-phase synthesis method of lithium sulfide as described in any one of claims 1 to 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the sulfide-based solid electrolyte as described in claim 9.

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