Liquid-phase synthesis system of lithium sulfide

Abstract

The utility model discloses a liquid-phase synthesis system of lithium sulfide. Comprising a first lithium sulfate dissolving device, a first barium sulfide dissolving device, a chemical combination reaction device, a first separation device and a second separation device, the liquid phase after-treatment unit is used for concentrating, purifying and drying the liquid phase to obtain lithium sulfide, and the solid phase after-treatment unit is used for washing and drying the solid phase to obtain barium sulfate; the first lithium sulfate dissolving device and the first barium sulfide dissolving device are both connected with a raw material inlet of the combination reaction device; and a reaction product outlet of the combination reaction device is connected with the first separation device. The liquid-phase synthesis system of the lithium sulfide has the advantages that products are easy to separate, the purity of the lithium sulfide products is high, the liquid-phase synthesis system of the lithium sulfide is very suitable for industrial-scale production, and the produced high-purity anhydrous lithium sulfide is very suitable for solid-state battery anode materials and has huge potential economic benefits.

Description

Technical Field

[0001] The utility model belongs to the field of batteries, and in particular relates to an electrolyte synthesis system. Background Art

[0002] Lithium-ion batteries are a rapidly emerging and promising new energy industry sector. All-solid-state lithium batteries, utilizing non-flammable solid electrolytes, can effectively improve battery safety. Among various solid electrolytes, sulfide solid electrolytes show excellent potential due to their high ionic conductivity. Lithium sulfide, a key raw material, is currently difficult to produce industrially. Existing methods for producing lithium sulfide include direct synthesis and solution methods. The direct synthesis method involves reacting metallic lithium and sulfur at high temperatures to produce lithium sulfide. This method is simple to operate, but the product purity can be low. The solution method involves reacting lithium salts and sulfides in a suitable solvent to produce lithium sulfide. This method involves the challenges of solvent treatment and recovery, as well as separation of the lithium sulfide from other substances in the solution. Overall, current industrial production of lithium sulfide is difficult to scale due to issues with product purity and product separation. Therefore, developing a synthesis system that produces high-purity lithium sulfide and facilitates its separation from the solution is key to advancing the practical application of sulfide electrolytes and sulfide solid-state batteries. Utility Model Content

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a liquid phase synthesis system for lithium sulfide with high purity and easy separation of lithium sulfide from the solution system.

[0004] In order to solve the above technical problems, the technical solutions proposed by the present invention are as follows:

[0005] A liquid-phase synthesis system for lithium sulfide comprises a first lithium sulfate dissolving device, a first barium sulfide dissolving device, a chemical reaction device, a first separation device for solid-liquid separation of reaction products in the chemical reaction device to obtain a liquid phase and a solid phase, a liquid-phase post-processing unit for concentrating, purifying, and drying the liquid phase to obtain lithium sulfide, and a solid-phase post-processing unit for washing and drying the solid phase to obtain barium sulfate. The first lithium sulfate dissolving device and the first barium sulfide dissolving device are both connected to a raw material inlet of the chemical reaction device, and a reaction product outlet of the chemical reaction device is connected to the first separation device.

[0006] In the above-mentioned liquid-phase synthesis system of lithium sulfide, preferably, the liquid-phase post-processing unit includes, in order according to the flow direction of lithium sulfide, a first evaporation and concentration device, a slicer, a first dryer, a recrystallization kettle, a second centrifuge, and a calcining furnace. The liquid phase separated by the first separation device is mainly a crude lithium sulfide solution. The lithium sulfide solution is first evaporated and concentrated by the first evaporation and concentration device, and then sliced ​​to obtain hydrous lithium sulfide. The hydrous lithium sulfide is then dried by the first dryer. In order to further improve the purity of the lithium sulfide, the lithium sulfide is dissolved again and recrystallized using a recrystallization kettle. The crystallized product is separated by a second centrifuge and the solid phase is collected, i.e., high-purity lithium sulfide. The high-purity lithium sulfide is calcined in a calcining furnace to remove volatiles, i.e., the final high-purity lithium sulfide product is obtained, which can be directly used as an electrolyte for solid-state batteries.

[0007] In the above-mentioned liquid phase synthesis system of lithium sulfide, preferably, the first dryer is a vacuum dryer with two connected sections.

[0008] In the above-mentioned liquid-phase synthesis system for lithium sulfide, the solid-phase post-processing unit preferably includes, in order of barium sulfate flow, a slurrying tank, a third centrifuge, a second dryer, and a packaging machine. The solid phase separated by the first separation device is primarily crude barium sulfate. This crude barium sulfate is slurried and washed in the slurrying tank, then dehydrated in the third centrifuge to collect the solid barium sulfate. The solid barium sulfate is dried in the second dryer and then packaged in the packaging machine to obtain the barium sulfate product. The mother liquor obtained after dehydration in the third centrifuge is then fed into the second barium sulfide dissolution unit.

[0009] The above-mentioned liquid-phase lithium sulfide synthesis system preferably further includes a second barium sulfide dissolution unit for dissolving unqualified barium sulfide raw material. The mother liquor separated by the third centrifuge is connected to the second barium sulfide dissolution unit, which, after passing through an impurity removal unit, is connected to the first barium sulfide dissolution unit. The provision of the second barium sulfide dissolution unit and the impurity removal unit allows impurities to be removed from unqualified barium sulfide raw material with high impurity content to improve its purity, thereby reducing the impurity content in the raw material and improving the purity of the lithium sulfide product. The unqualified barium sulfide raw material is first dissolved in the second barium sulfide dissolution unit to produce a barium sulfide solution. After the impurities are removed by the impurity removal unit (for example, to remove elements such as iron), the barium sulfide solution can be directly returned to the first barium sulfide dissolution unit for use in synthesizing raw material. The mother liquor separated by the third centrifuge primarily contains the useful component lithium sulfide. This lithium sulfide can be fed into the second barium sulfide solution unit, then into the chemical reaction vessel, and finally into the product, thereby avoiding lithium sulfide waste and improving product yield.

[0010] The above-mentioned lithium sulfide liquid phase synthesis system preferably also includes a lithium sulfate impurity removal and refining unit for removing impurities and refining unqualified lithium sulfate raw materials. More preferably, the lithium sulfate impurity removal and refining unit includes a second lithium sulfate solution device, a second evaporation and concentration device, a cooling crystallization kettle, and a fourth centrifuge in order according to the flow direction of lithium sulfate, and the solid phase separated by the fourth centrifuge is connected to the first lithium sulfate dissolution device. The lithium sulfate impurity removal and refining unit can be used to purify and remove impurities from unqualified lithium sulfate raw materials with high impurity content, which is beneficial to reduce the impurity content in the raw materials and improve the purity of the product lithium sulfide. In the above-mentioned lithium sulfate impurity removal and refining unit, the lithium sulfide is first dissolved in the second lithium sulfate solution device to obtain a lithium sulfide solution, and then the lithium sulfide solution is evaporated and concentrated in the second evaporation and concentration device. The lithium sulfate is then cooled and crystallized in the cooling crystallization kettle to precipitate lithium sulfate. Finally, the solid phase is collected by centrifugation in the fourth centrifuge to obtain high-purity lithium sulfate. The lithium sulfate can be directly returned to the first lithium sulfate dissolution device to be dissolved again for use in synthesizing raw materials. The mother liquor centrifuged by the fourth centrifuge can be used for the impurity removal process.

[0011] In the above-mentioned lithium sulfide liquid-phase synthesis system, preferably, a lithium sulfate solution metering tank is provided between the first lithium sulfate dissolving device and the chemical combination reaction device, and a barium sulfide solution metering tank is provided between the first barium sulfide dissolving device and the chemical combination reaction device. The lithium sulfate solution metering tank can accurately control the amount of lithium sulfate added to the chemical combination reaction device. Similarly, the barium sulfide solution metering tank can accurately control the amount of barium sulfide added to the chemical combination reaction device. By controlling the amount of lithium sulfate and barium sulfide added, the reaction between the two is facilitated and unnecessary waste of raw materials is reduced.

[0012] In the above-mentioned liquid-phase synthesis system of lithium sulfide, preferably, the first separation device is a butterfly centrifuge.

[0013] The lithium sulfide liquid-phase synthesis system of the present invention is used to synthesize lithium sulfide. The main process can be as follows: raw material pretreatment, chemical reaction, solid-liquid separation, washing, dehydration, and drying of barium sulfate, concentration of the lithium sulfide solution, slicing, two-stage vacuum drying, recrystallization, centrifugal dehydration, and calcination under inert gas protection. The final products are high-purity anhydrous lithium sulfide and barium sulfate. The raw materials are lithium sulfate and barium sulfide, both of which can be solid or liquid. Generally, the dry salt impurity content of either raw material is required to be no more than 5%. If the dry salt impurity content exceeds 5%, it should undergo appropriate pretreatment to remove impurities before use. During the reaction, the lithium sulfate and barium sulfide can be added in various forms, including but not limited to solid or liquid. The order of addition includes but is not limited to sequential addition or simultaneous addition. The methods of addition include but are not limited to all-in-one addition, dropwise addition, and microchannel mixing. The desired reaction ratio is preferably a molar ratio of lithium sulfate:barium sulfide of 1.05:1, but varying the ratio and raw material concentration within any range does not hinder the production of lithium sulfide. During the reaction, lithium sulfate and barium sulfide react chemically to produce water-insoluble barium sulfate and soluble lithium sulfide. Methods for separating lithium sulfide and barium sulfate from the above-mentioned chemical reaction device include, but are not limited to, natural sedimentation, centrifugation, filter press, and suction filtration. After washing, dehydration, and drying, the barium sulfate is directly sold as a product for use as an additive in automotive coatings, etc. Methods for concentrating the lithium sulfide solution include, but are not limited to, atmospheric evaporation, flash evaporation, vacuum evaporation, and spraying. After concentration, the water content of the lithium sulfide is preferably 40-60%. However, relaxing or limiting this water content does not affect the subsequent production of hydrous or non-hydrous lithium sulfide by slicing or other methods. The hydrous lithium sulfide is then dried, preferably using two-stage vacuum drying, with a maximum vacuum of -0.098 MPa. Changing the drying method or maximum vacuum does not hinder the production of crude anhydrous lithium sulfide. To further improve purity, crude anhydrous lithium sulfide is dissolved in an organic solvent and recrystallized. The separated crystals are then centrifuged and dehydrated. The organic solvent used to dissolve the crude anhydrous lithium sulfide includes, but is not limited to, methanol, ethanol, and propanol. Calcination is performed under an inert gas atmosphere, including, but not limited to, hydrogen, argon, and nitrogen. Varying the inert gas, calcination temperature, and calcination time does not hinder the production of high-purity anhydrous lithium sulfide.

[0014] Compared with the prior art, the advantages of the present invention are:

[0015] The liquid-phase synthesis system of lithium sulfide of the present invention includes a first lithium sulfate dissolving device, a first barium sulfide dissolving device, a chemical reaction device, a first separation device, a liquid-phase post-processing unit, and a solid-phase post-processing unit. The raw materials dissolved in the first lithium sulfate dissolving device and the first barium sulfide dissolving device enter the chemical reaction device for chemical reaction to generate water-insoluble barium sulfate and soluble lithium sulfide, which are mutually insoluble and easily separated. The barium sulfate is passed through the solid-phase post-processing unit to obtain a barium sulfate product, and the lithium sulfide is passed through the liquid-phase post-processing unit to obtain a high-purity lithium sulfide product. The entire liquid-phase synthesis system has the advantages of easy product separation and high purity of the lithium sulfide product. At the same time, in the liquid-phase synthesis system of lithium sulfide of the present invention, the synthetic raw materials are widely available and low in cost, making it very suitable for industrial-scale production. The high-purity anhydrous lithium sulfide produced is very suitable for use as a positive electrode material for solid-state batteries, with huge potential economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 Schematic diagram of the process of the liquid phase synthesis system of lithium sulfide in the embodiment.

[0018] Legend

[0019] 1. First lithium sulfate dissolving device; 2. First barium sulfide dissolving device; 3. Combination reaction device; 4. First separation device; 5. First evaporation concentration device; 6. Slicer; 7. First dryer; 8. Recrystallization kettle; 9. Second centrifuge; 10. Calcination furnace; 11. Beating tank; 12. Third centrifuge; 13. Second dryer; 14. Packaging machine; 15. Second barium sulfide dissolving device; 16. Impurity removal unit; 17. Second lithium sulfate solution device; 18. Second evaporation concentration device; 19. Cooling crystallization kettle; 20. Fourth centrifuge; 21. Lithium sulfate solution metering tank; 22. Barium sulfide solution metering tank. DETAILED DESCRIPTION

[0020] In order to facilitate the understanding of the present invention, the present invention will be described in more comprehensive and detailed manner below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

[0021] It should be noted that when an element is described as being "fixed, fixed, connected or communicated with" another element, it can be directly fixed, fixed, connected or communicated with the other element, or it can be indirectly fixed, fixed, connected or communicated with the other element through other intermediate connectors.

[0022] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0023] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0024] Example:

[0025] like Figure 1 As shown, the liquid-phase synthesis system of lithium sulfide in this embodiment includes a first lithium sulfate dissolving device 1 (which can be a dissolving kettle), a first barium sulfide dissolving device 2 (which can be a dissolving kettle), a chemical reaction device 3 (which can be a reactor), a first separation device 4 (specifically, a butterfly centrifuge) for solid-liquid separation of the reaction product in the chemical reaction device 3 to obtain a liquid phase and a solid phase, a liquid phase post-treatment unit for concentrating, purifying and drying the liquid phase to obtain lithium sulfide, and a solid phase post-treatment unit for washing and drying the solid phase to obtain barium sulfate. The first lithium sulfate dissolving device 1 and the first barium sulfide dissolving device 2 are both connected to the raw material inlet of the chemical reaction device 3, and the reaction product outlet of the chemical reaction device 3 is connected to the first separation device 4.

[0026] In this embodiment, the liquid-phase post-processing unit includes, in order of lithium sulfide flow, a first evaporation and concentration device 5 (which may be a dissolution kettle), a slicer 6, a first dryer 7, a recrystallization kettle 8, a second centrifuge 9, and a calcining furnace 10. Specifically, the first dryer 7 is a two-stage connected vacuum dryer.

[0027] In this embodiment, the solid phase post-processing unit includes a beating tank 11, a third centrifuge 12, a second dryer 13 and a packaging machine 14 in order according to the flow direction of barium sulfate.

[0028] In this embodiment, a second barium sulfide dissolving device 15 (which can be a dissolving kettle) for dissolving unqualified barium sulfide raw materials is also included. The mother liquor separated by the third centrifuge 12 is connected to the second barium sulfide dissolving device 15. The second barium sulfide dissolving device 15 is connected to the first barium sulfide dissolving device 2 after passing through an impurity removal unit 16.

[0029] This embodiment also includes a lithium sulfate impurity removal and purification unit for removing impurities and refining unqualified lithium sulfate raw materials. Specifically, the lithium sulfate impurity removal and purification unit includes, in order of lithium sulfate flow, a second lithium sulfate solution device 17 (which can be a dissolution kettle), a second evaporation and concentration device 18, a cooling crystallization kettle 19, and a fourth centrifuge 20. The solid phase separated by the fourth centrifuge 20 is connected to the first lithium sulfate dissolution device 1.

[0030] In this embodiment, a lithium sulfate solution metering tank 21 is provided between the first lithium sulfate dissolving device 1 and the chemical combination reaction device 3 , and a barium sulfide solution metering tank 22 is provided between the first barium sulfide dissolving device 2 and the chemical combination reaction device 3 .

[0031] In order to better understand the above-mentioned liquid phase synthesis system of lithium sulfide, this embodiment also provides a typical method for synthesizing lithium sulfide using the above-mentioned liquid phase synthesis system of lithium sulfide, which is specifically described as follows:

[0032] (1) The raw materials used are lithium sulfate and barium sulfide, which are dissolved in the first lithium sulfate dissolving device 1 and the first barium sulfide dissolving device 2 respectively using boiled deionized water. Under normal circumstances, the TDS (total dissolved solids) of the deionized water does not exceed 20 mg / L. Preferably, the concentration of the lithium sulfate solution and the barium sulfide solution is 0.5 mol / L. For the raw materials, the dry salt impurity content is generally required to be no more than 5%. If the impurity content is high, appropriate impurity removal and purification are required. For the purification and impurity removal of lithium sulfate, first, 85°C hot water is used to dissolve lithium sulfide through the second lithium sulfate solution device 17 to obtain a saturated lithium sulfide solution, and then the lithium sulfide solution is evaporated and concentrated by the second evaporation and concentration device 18, and then the cooling crystallization kettle 19 is used to cool and crystallize to precipitate lithium sulfate, and finally the fourth centrifuge 20 is used for centrifugation to collect the solid phase, which is high-purity lithium sulfate. The lithium sulfate can be directly returned to the first lithium sulfate dissolving device 1 to be dissolved again for synthesizing raw materials. For the purification and impurity removal of barium sulfide, firstly, the barium sulfide is dissolved by the second barium sulfide dissolving device 15 to obtain a barium sulfide solution. After the barium sulfide solution is removed by the impurity removal unit 16 (for example, to remove elements such as iron), the solution can be directly returned to the first barium sulfide dissolving device 2 for use in synthesizing raw materials.

[0033] (2) The raw materials in the first lithium sulfate dissolving device 1 and the first barium sulfide dissolving device 2 are metered into the compound reaction device 3 through the lithium sulfate solution metering tank 21 and the barium sulfide solution metering tank 22 respectively. The barium sulfide solution can be added dropwise to the lithium sulfate solution for sufficient stirring. The reaction of lithium sulfate and barium sulfide is realized in the compound reaction device 3. In industrial production, the addition of barium sulfide solution can be achieved by interlocking the barium sulfide solution metering tank 22 and the regulating valve. The required ratio of the reaction is preferably a molar ratio of lithium sulfate: barium sulfide of 1.05:1. In actual production, it can be achieved by weighing and liquid level control of the lithium sulfate solution metering tank 21 and the barium sulfide solution metering tank 22. The reaction end point is generally controlled by checking auxiliary parameters such as pH, and the appropriate pH should be 6-7.

[0034] (3) After the reaction is complete, water-insoluble barium sulfate and soluble lithium sulfide are produced. Generally, a butterfly centrifuge is used for solid-liquid separation. The collected solid is crude barium sulfate, which enters the solid phase post-processing unit, and the collected clear liquid is lithium sulfide solution, which enters the liquid phase post-processing unit.

[0035] (4) The crude barium sulfate enters the solid phase post-processing unit. The specific process is as follows: the barium sulfate is sent to the beating tank 11 for beating and washing, and then sent to the third centrifuge 12 for dehydration. The solid phase is then sent to the second dryer 13 (such as a hollow blade dryer) for drying, and then automatically packaged by the packaging machine 14 and sold as a product. The liquid phase obtained by dehydration in the third centrifuge 12 enters the second barium sulfide dissolution device 15 to achieve the return of lithium sulfide, thereby increasing the yield of the product lithium sulfide.

[0036] (5) The specific process of the lithium sulfide solution entering the liquid phase post-processing unit is as follows: the clarified lithium sulfide solution is evaporated and concentrated to 40-60% water content by the first evaporation concentration device 5, and then sliced ​​by the slicer 6 to obtain hydrous lithium sulfide. The suitable evaporation temperature is 85°C and the vacuum degree is -0.07MPa. The hydrous lithium sulfide is then subjected to two stages of vacuum drying to obtain crude anhydrous lithium sulfide. The suitable first stage vacuum drying temperature is 85°C and the time is 1h; the second stage vacuum drying temperature is 115°C and the time is 0.5h. In order to further improve the purity, the crude anhydrous lithium sulfide is dissolved in an organic solvent and recrystallized using a recrystallization kettle 8. The separated crystals are centrifuged and dehydrated by a second centrifuge 9, and then calcined in a calcination furnace 10 under the protection of inert gas to remove volatiles, and finally high-purity anhydrous lithium sulfide is obtained. The suitable organic solvent is methanol, the suitable inert gas is hydrogen, the suitable calcination temperature is a maximum of 400°C, a heating rate of 5°C / min, and a constant temperature calcination for 0.5h.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A liquid phase synthesis system for lithium sulfide, characterized in that: The invention comprises a first lithium sulfate dissolving device (1), a first barium sulfide dissolving device (2), a chemical reaction device (3), a first separation device (4) for separating the reaction product in the chemical reaction device (3) into a liquid phase and a solid phase, a liquid phase post-processing unit for concentrating, purifying and drying the liquid phase to obtain lithium sulfide, and a solid phase post-processing unit for washing and drying the solid phase to obtain barium sulfate. The first lithium sulfate dissolving device (1) and the first barium sulfide dissolving device (2) are both connected to the raw material inlet of the chemical reaction device (3), and the reaction product outlet of the chemical reaction device (3) is connected to the first separation device (4).

2. The liquid phase synthesis system of lithium sulfide according to claim 1, characterized in that: The liquid phase post-processing unit comprises, in order according to the flow direction of lithium sulfide, a first evaporation concentration device (5), a slicer (6), a first dryer (7), a recrystallization kettle (8), a second centrifuge (9) and a calcining furnace (10).

3. The liquid phase synthesis system of lithium sulfide according to claim 2, characterized in that: The first dryer (7) is a vacuum dryer with two connected sections.

4. The liquid phase synthesis system of lithium sulfide according to claim 1, characterized in that: The solid phase post-processing unit comprises, in order according to the flow direction of the barium sulfate, a pulping tank (11), a third centrifuge (12), a second dryer (13) and a packaging machine (14).

5. The liquid phase synthesis system of lithium sulfide according to claim 4, characterized in that: The invention also includes a second barium sulfide dissolving device (15) for dissolving unqualified barium sulfide raw materials, wherein the mother liquor separated by the third centrifuge (12) is connected to the second barium sulfide dissolving device (15), and the second barium sulfide dissolving device (15) is connected to the first barium sulfide dissolving device (2) after passing through an impurity removal unit (16).

6. The liquid phase synthesis system for lithium sulfide according to any one of claims 1 to 5, characterized in that: It also includes a lithium sulfate impurity removal and refining unit for removing impurities and refining unqualified lithium sulfate raw materials.

7. The liquid phase synthesis system of lithium sulfide according to claim 6, characterized in that: The lithium sulfate impurity removal and refining unit comprises, in order according to the flow direction of lithium sulfate, a second lithium sulfate solution device (17), a second evaporation concentration device (18), a cooling crystallization kettle (19), and a fourth centrifuge (20); the solid phase separated by the fourth centrifuge (20) is connected to the first lithium sulfate dissolution device (1).

8. The liquid phase synthesis system for lithium sulfide according to any one of claims 1 to 5, characterized in that: A lithium sulfate solution metering tank (21) is provided between the first lithium sulfate dissolving device (1) and the chemical combination reaction device (3), and a barium sulfide solution metering tank (22) is provided between the first barium sulfide dissolving device (2) and the chemical combination reaction device (3).

9. The liquid phase synthesis system for lithium sulfide according to any one of claims 1 to 5, characterized in that: The first separation device (4) is a butterfly centrifuge.

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