Preparation method of high-purity and low-cost lithium sulfide and prepared lithium sulfide

Abstract

The invention provides a preparation method of high-purity and low-cost lithium sulfide and lithium sulfide prepared by the preparation method, and relates to the field of lithium sulfide materials. According to the preparation method of the high-purity and low-cost lithium sulfide, on the basis of the characteristics of high-efficiency heat and mass transfer and uniform dispersion of a fluidized bed fluidization technology, lithium source small liquid drops are coated on the surface of a fluidized precursor, then hydrogen sulfide gas is introduced, the lithium source melt liquid drops or the precursor coated with the lithium source solution liquid drops are subjected to a contact reaction with the hydrogen sulfide gas, and the high-purity and low-cost lithium sulfide is obtained. The lithium sulfide is prepared. According to the preparation method of the high-purity and low-cost lithium sulfide, the problems of more reaction byproducts, low hydrogen sulfide gas utilization rate, easiness in product agglomeration and non-uniform particle size distribution in the existing lithium sulfide preparation process can be effectively solved, the reaction temperature is further reduced, and the production safety is improved; and the problem that the product purity and quality are influenced by water vapor in the preparation process is effectively avoided, and stable and efficient lithium sulfide production is realized.

Description

Technical Field

[0001] The present invention relates to the field of lithium sulfide materials, and in particular to a method for preparing high-purity and low-cost lithium sulfide and the lithium sulfide obtained thereby. Background Art

[0002] Sulfide solid electrolytes have gradually been established as the consensus of the all-solid-state battery technology route in the academic and industrial circles due to their leading advantages in ionic conductivity. Among them, the key material links in the upstream of the industrial chain, including the performance control of electrolyte materials and their precursors, the optimization of large-scale preparation processes, and cost control, have become important bottlenecks restricting the industrialization process of sulfide all-solid-state batteries.

[0003] The core challenge currently faced by the industrial chain lies in the high raw material costs: the price of commercially available lithium sulfide raw materials remains at a high level of 5 million yuan / ton, and the price of sulfide electrolyte materials is even as high as 20 million yuan / ton. As a result, the total cost of all-solid-state battery cells using a high-nickel cathode / silicon-based anode system exceeds 20 yuan / Wh, which is more than 40 times higher than that of traditional liquid lithium batteries (about 0.5 yuan / Wh), seriously restricting commercial promotion. Industry analysis shows that only when the price of sulfide electrolyte materials drops to 500,000 yuan / ton can the cost of all-solid-state battery cells possibly reach the industrial critical point of 0.6 yuan / Wh, thus having the basic conditions to compete with traditional batteries.

[0004] The mainstream technical routes for synthesizing lithium sulfide include ball milling method, solvent method, high temperature and high pressure method, direct carbon composite method, etc. However, each preparation method still has significant technical bottlenecks. For example, the metal lithium / lithium hydride raw materials used in the ball milling method have high costs, and there are defects such as long reaction time, low conversion efficiency, and many polysulfide impurities that are not easy to purify; the process operation of the solvent method is complex (involving solvothermal synthesis, centrifugal washing, etc.), the preparation process is difficult to control, and the amount of organic solvents used is large; the high temperature and high pressure method has strict requirements for equipment selection, high raw material costs, and high comprehensive production costs; the direct carbon composite method, as the current technical path with the deepest industrialization exploration, requires specific carbon materials and high temperature conditions to synthesize lithium sulfide with smaller particle sizes, and the process is relatively complex.

[0005] Therefore, there is an urgent need to provide a new low-cost method for preparing lithium sulfide to solve the above problems. In the prior art, it is disclosed that lithium carbonate is melted and then sprayed into a reaction vessel filled with hydrogen sulfide for contact reaction, and then washed, filtered, and spray-dried to obtain lithium sulfide. However, this method has problems such as many reaction by-products, low utilization rate of hydrogen sulfide gas, easy agglomeration of products, and uneven particle size distribution during the preparation process. At the same time, the contact reaction temperature between molten lithium carbonate and hydrogen sulfide gas is high, and the production safety is poor; and it is easily affected by water vapor during the preparation process, reducing the product purity and quality, and unable to maintain stable and efficient production of lithium sulfide. Summary of the Invention

[0006] To solve the technical problems existing in the prior art, the present invention provides a method for preparing lithium sulfide with high purity and low cost and the lithium sulfide obtained thereby, which can effectively overcome the problems of many reaction by-products, low utilization rate of hydrogen sulfide gas, easy agglomeration of products and uneven particle size distribution existing in the preparation process of lithium sulfide, further reduce the reaction temperature, improve production safety; and effectively avoid the problem of affecting the product purity and quality due to water vapor in the preparation process, and realize stable and efficient production of lithium sulfide.

[0007] To solve the above technical problems, the technical solutions adopted by the present invention are as follows: A method for preparing lithium sulfide with high purity and low cost, comprising the following steps: Step S001: Put the precursor powder into a fluidized bed reactor, continuously introduce an inert gas into the fluidized bed reactor, keep the precursor powder in the fluidized bed reactor in a fluidized state, and preheat it to 610 - 660 °C for heat preservation; The precursor powder is D 50 Lithium sulfide with a particle size of 0.1 - 3 μm; Step S002: Divide the lithium source melt or lithium source solution into 2 - 5 portions, and spray them into lithium source spray droplets respectively in the subsequent steps and enter the fluidized bed reactor; The lithium source melt is a melt of lithium chloride and / or lithium hydroxide; The solute of the lithium source solution is lithium naphthalide or lithium hydroxide; Step S003: The first portion of lithium source spray droplets enters the fluidized bed reactor and coats the precursor powder; Step S004: After introducing the first portion of hydrogen sulfide gas into the fluidized bed reactor for reaction, stop introducing hydrogen sulfide gas; repeat the above operation, and the remaining portions of lithium source spray droplets enter the fluidized bed reactor in sequence, and after each portion of lithium source spray droplets enters the fluidized bed reactor, introduce the corresponding portion of hydrogen sulfide gas into the fluidized bed reactor for reaction; until after the last portion of lithium source spray enters the fluidized bed reactor, introduce the last portion of hydrogen sulfide gas into the fluidized bed reactor for reaction; Step S005: After the reaction is completed, cool down to obtain a crude product; the crude product is prepared into lithium sulfide through post-treatment.

[0008] Preferably, in the step S002, the preparation method of the lithium source melt is to melt lithium chloride and / or lithium hydroxide in an inert gas environment, control the melting temperature to be 500 - 630 °C, and obtain the lithium source melt.

[0009] Preferably, in the step S002, the particle size of the lithium source spray droplets is 3 - 15 μm; The spray rate is 50 - 400 mL / min.

[0010] Preferably, in the step S004, it is controlled that the total mass of the lithium source spray droplets in the latter portion is greater than that of the lithium source spray droplets in the former portion.

[0011] Preferably, in the step S004, it is controlled that in each portion of the lithium source spray droplets and the corresponding portion of hydrogen sulfide gas, the molar ratio of lithium to hydrogen sulfide is 1:0.6 - 2.

[0012] Preferably, in the step S004, when the lithium source spray droplets are prepared from a lithium source melt, the total reaction time for introducing hydrogen sulfide gas is 2 - 6 h; when the lithium source spray droplets are prepared from a lithium source solution, the total reaction time for introducing hydrogen sulfide gas is 2 - 8 h.

[0013] Further, in the step S004, after introducing the first portion of hydrogen sulfide gas into the fluidized bed reactor for reaction, the introduction of hydrogen sulfide gas is stopped; after the second portion of lithium source spray enters the fluidized bed reactor, the second portion of hydrogen sulfide gas is introduced into the fluidized bed reactor for reaction; The mass ratio of the first portion of lithium source spray droplets to the second portion of lithium source spray droplets is 10 - 30:70 - 90.

[0014] Further, in the step S005, the post - treatment is to wash the crude product with an organic solvent, and then through filtration, drying, and pulverization, lithium sulfide is obtained.

[0015] Preferably, the organic solvent is at least one of the following: ethanol, dimethyl sulfoxide, N,N - dimethylformamide, and acetonitrile.

[0016] A lithium sulfide prepared by the foregoing method, the D 50 particle size of the lithium sulfide is 0.2 - 15 μm, the purity is 99.40 - 99.99 wt%, and the particle size distribution width is 0.75 - 2.4.

[0017] Compared with the prior art, the beneficial effects of the present invention are: (1) The high-purity, low-cost preparation method of lithium sulfide of the present invention is based on the high-efficiency heat and mass transfer and uniform dispersion characteristics of fluidized bed fluidization technology. After the lithium source droplets are coated on the surface of the fluidized precursor, hydrogen sulfide gas is introduced. The precursor coated with the lithium source melt droplets (i.e., molten lithium chloride and / or lithium hydroxide) and the hydrogen sulfide gas form a gas-solid-liquid three-phase state in the fluidized bed, or after the lithium source solution droplets (i.e., the solute is lithium naphthalene or lithium hydroxide) enter the fluidized bed and the solvent is rapidly vaporized, the lithium source solute and the hydrogen sulfide gas form a gas-solid two-phase state in the fluidized bed. The two are fully contacted and reacted, the reaction time is shortened, the utilization rate of hydrogen sulfide gas is improved, the generation of reaction by-products is suppressed, the reaction energy consumption is reduced, and the spray dispersion characteristics are combined to effectively prepare a lithium sulfide material with a higher particle size distribution concentration; at the same time, the reaction temperature is further reduced, and the production safety is improved; the problem of water vapor affecting the product purity and quality during the preparation process is effectively avoided, and stable and efficient lithium sulfide production is achieved.

[0018] (2) The method for preparing high-purity, low-cost lithium sulfide of the present invention has relatively low-priced and easily available reaction raw materials, a simple preparation process, and an easy-to-control preparation process. The BOM cost (Bill of Material Cost) is even lower, which is conducive to large-scale industrial production.

[0019] (3) The high-purity, low-cost preparation method of the present invention requires a lower reaction temperature and does not introduce new impurities during the preparation process. The purity of the prepared lithium sulfide can reach 99.93wt%, and the particle size distribution is concentrated and controllable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of a method for preparing high-purity, low-cost lithium sulfide according to an embodiment of the present invention.

[0021] Figure 2 This is the particle size distribution diagram of lithium sulfide prepared in Example 3. DETAILED DESCRIPTION

[0022] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific embodiments of the present invention are now described. It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by those of ordinary skill in the art to which the present invention belongs.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, "first", "second", etc. are used to distinguish similar objects and are not used to describe a specific order or sequence. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] As Figure 1 shown, an embodiment of the present invention provides a method for preparing lithium sulfide with high purity and low cost, including the following steps: Step S001: Put the precursor powder into a fluidized bed reactor, and by purging a carrier gas into the fluidized bed reactor, keep the precursor powder in the fluidized bed reactor in a continuous fluidized state and preheat it to 610 - 660 °C for heat preservation.

[0025] In step S001, the carrier gas is an inert gas, preferably nitrogen or argon; The precursor powder is D 50 lithium sulfide powder with a particle size of 0.1 - 3 μm.

[0026] In step S001, according to the particle size of the precursor powder and the scale of the fluidized bed reactor, the carrier gas purge flow rate range is 1 - 100 L / min to keep the precursor powder in the fluidized bed reactor evenly dispersed and in a continuous fluidized state.

[0027] Step S002: Divide the lithium source melt or lithium source solution into 2 - 5 parts, and then spray them into the fluidized bed reactor respectively to contact with the fluidized materials in the fluidized bed reactor.

[0028] In step S002, the preparation method of the lithium source melt is to melt the lithium source powder at a melting temperature of 500 - 630 °C in an inert gas environment to obtain the lithium source melt; the lithium source powder is lithium chloride and / or lithium hydroxide.

[0029] In step S002, the lithium source solution is at least one of the following: lithium naphthalide tetrahydrofuran solution, lithium hydroxide water / ethanol solution.

[0030] Step S003: The first portion of the lithium source spray droplets enters the fluidized bed reactor and contacts the fluidized precursor powder, coating the outer surface of the precursor powder; the first portion of the lithium source spray droplets is small droplets with a particle size of 3 - 15 μm formed by spraying the first portion of the lithium source melt or lithium source solution through a spraying device.

[0031] Step S004: Introduce the first portion of hydrogen sulfide gas into the fluidized bed reactor. After the lithium source reacts with hydrogen sulfide, stop introducing hydrogen sulfide gas. Then, the second portion of the lithium source spray droplets enters the fluidized bed reactor. After the spraying of the second portion of the lithium source spray droplets is completed, continue to introduce the second portion of hydrogen sulfide gas into the fluidized bed reactor for reaction, and then stop introducing hydrogen sulfide gas. Repeat the above operation, and the remaining portions of the lithium source spray droplets sequentially enter the fluidized bed reactor. After the spraying of each portion of the lithium source spray droplets is completed, continue to introduce the corresponding portion of hydrogen sulfide gas into the fluidized bed reactor for reaction. Until the spraying of the last portion of the lithium source spray droplets is completed, introduce the last portion of hydrogen sulfide gas into the fluidized bed reactor for reaction.

[0032] In step S004, control the spraying rate to be 50 - 400 mL / min. Each portion of the lithium source spray droplets is formed by spraying each portion of the lithium source melt or lithium source solution through a spraying device to form small droplets with a particle size of 3 - 15 μm.

[0033] In step S004, during the process of spraying each portion of the lithium source spray droplets into the fluidized bed reactor, stop introducing hydrogen sulfide gas. And control the total mass of the lithium source spray droplets in the latter portion to be greater than that in the former portion. By adding the lithium source spray droplets multiple times and fully reacting with the fluidized materials in the fluidized bed reactor, the reaction time is shortened, the utilization rate of hydrogen sulfide gas is improved, and the generation of reaction by-products is inhibited. At the same time, in combination with the precursor powder coated with lithium source, the particle size distribution of the lithium sulfide material is further adjusted.

[0034] In step S004, during the preparation of lithium sulfide, control the molar ratio of lithium source to hydrogen sulfide in each portion of the lithium source spray droplets and each portion of hydrogen sulfide gas to be 1:0.6 - 2.

[0035] In step S004, during the preparation of lithium sulfide, when the lithium source spray droplets are prepared from the lithium source melt, the total reaction time for introducing hydrogen sulfide gas is 2 - 6 h; when the lithium source spray droplets are prepared from the lithium source solution, the total reaction time for introducing hydrogen sulfide gas is 2 - 8 h.

[0036] Preferably, in step S004, divide the lithium source spray droplets into two portions and transport them into the fluidized bed reactor. The mass ratio of the first portion of the lithium source spray droplets to the second portion of the lithium source spray droplets is 10 - 30:70 - 90.

[0037] Step S005: After the reaction is completed, introduce an inert gas to completely displace the hydrogen sulfide gas in the fluidized bed reactor. After cooling to room temperature, obtain the crude product and discharge it. The crude product is washed with an organic solvent, filtered, dried, and polished to obtain the final product lithium sulfide.

[0038] In step S005, the organic solvent used for washing is at least one of the following: ethanol, dimethyl sulfoxide, N,N-dimethylformamide, and acetonitrile.

[0039] An embodiment of the present invention also provides lithium sulfide prepared by the foregoing method, with a purity of 99.40 - 99.99 wt%, D 50 a particle size of 0.2 - 15 μm, and a particle size distribution width (Span = (D 90 - D 10 ) / D 50 ) of 0.75 - 2.4.

[0040] The following further illustrates the present invention in conjunction with some specific embodiments.

[0041] Example 1 This example provides a method for preparing lithium sulfide with high purity and low cost, and the specific steps are as follows: Step S001: Put the precursor powder with a particle size of 0.5 μm into a fluidized bed reactor, purge the carrier gas (nitrogen) into the fluidized bed reactor, and control the purge flow rate of the carrier gas (nitrogen) to increase from 1 L / min to 10 L / min, keep the precursor powder in the fluidized bed reactor in a continuous fluidized state, and preheat to 650 °C for heat preservation. 50

[0042] Step S002: In an argon atmosphere environment, control the melting temperature to be 620 °C, melt the lithium source powder (lithium chloride) to obtain a lithium source melt; divide the lithium source melt into two parts, and subsequently control the spraying rate to be 50 mL / min. Each part of the lithium source melt is sprayed through a spraying device to form small droplets with a particle size of 3 μm, forming a first part of lithium source spray droplets and a second part of lithium source spray droplets.

[0043] Step S003: The first part of the lithium source spray droplets enters the fluidized bed reactor and contacts the fluidized precursor powder, coating the outer surface of the precursor powder.

[0044] Step S004: Continuously introduce the first part of hydrogen sulfide gas into the fluidized bed reactor at a feeding rate of 400 L / h, control the total feeding and reaction time of the first part of hydrogen sulfide gas to be 1 h, stop introducing hydrogen sulfide gas after the lithium source reacts with hydrogen sulfide; then the second part of the lithium source spray droplets enters the fluidized bed reactor. After the spraying of the second part of the lithium source spray droplets is completed, continue to introduce the second part of hydrogen sulfide gas into the fluidized bed reactor at a feeding rate of 400 L / h, and control the total feeding and reaction time of the second part of hydrogen sulfide gas to be 1 h, and continue to make the lithium source react with hydrogen sulfide.

[0045] In steps S003 and S004, the mass ratio of the first part of the lithium source spray droplets to the second part of the lithium source spray droplets is 20:80.​

[0046] Among the lithium source spray droplets and hydrogen sulfide gas used, the molar ratio of lithium chloride to hydrogen sulfide is 1:1.5; that is, the molar ratio of lithium chloride to hydrogen sulfide in the first portion of lithium source spray droplets and the first portion of hydrogen sulfide gas is 1:1.5; the molar ratio of lithium chloride to hydrogen sulfide in the second portion of lithium source spray droplets and the second portion of hydrogen sulfide gas is 1:1.5.

[0047] Step S005: After the reaction ends, an inert gas (nitrogen) is introduced to completely displace the hydrogen sulfide gas in the fluidized bed reactor. After cooling to room temperature, a crude product is obtained and discharged; the crude product is washed with dimethyl sulfoxide, and then filtered, dried, and polished to obtain the final product lithium sulfide.

[0048] This example also provides lithium sulfide prepared by the aforementioned method. The purity measured by a carbon-sulfur analyzer (detecting C / S content) and ICP full-element scanning is 99.45 wt%; the D 50 particle size is 1.2 μm, and the particle size distribution width (Span = (D 90 - D 10 ) / D 50 ) is 2.33.

[0049] Example 2 This example provides a method for preparing lithium sulfide with high purity and low cost, and the specific steps are as follows: Step S001: Put the precursor powder with a D 50 particle size of 2 μm into the fluidized bed reactor, purge the carrier gas (argon) into the fluidized bed reactor, and control the purge flow rate of the carrier gas (argon) to increase from 20 L / min to 50 L / min, keep the precursor powder in the fluidized bed reactor in a continuous fluidized state, and preheat to 630 °C for heat preservation.

[0050] Step S002: In a nitrogen atmosphere, control the melting temperature to be 530 °C, melt the lithium source powder (lithium hydroxide) to obtain a lithium source melt; divide the lithium source melt into two portions, and then control the spraying rate to be 100 mL / min. Each portion of the lithium source melt is sprayed through a spraying device to form small droplets with a particle size of 12 μm, forming the first portion of lithium source spray droplets and the second portion of lithium source spray droplets.

[0051] Step S003: The first portion of lithium source spray droplets enters the fluidized bed reactor and contacts the fluidized precursor powder, and coats the outer surface of the precursor powder.

[0052] Step S004, continuously introducing the first portion of hydrogen sulfide gas into the fluidized bed reactor at a rate of 18 L / h, controlling the total time of the introduction and reaction of the first portion of hydrogen sulfide gas to be 3 hours, and stopping the introduction of hydrogen sulfide gas after the lithium source is contacted with hydrogen sulfide for reaction; then the second portion of lithium source spray droplets enter the fluidized bed reactor, and after the second portion of lithium source spray droplets are transported, continue to introduce the second portion of hydrogen sulfide gas into the fluidized bed reactor at a rate of 18 L / h, controlling the total time of the introduction and reaction of the second portion of hydrogen sulfide gas to be 3 hours, and continue to contact and react with the lithium source.

[0053] In step S003 and step S004, the mass ratio of the first portion of lithium source spray droplets to the second portion of lithium source spray droplets is 30:70.

[0054] In each portion of lithium source spray droplets and each portion of hydrogen sulfide gas used, the molar ratio of lithium hydroxide to hydrogen sulfide is 1:0.7; that is, the molar ratio of lithium hydroxide to hydrogen sulfide in the first portion of lithium source spray droplets and the first portion of hydrogen sulfide gas is 1:0.7; the molar ratio of lithium hydroxide to hydrogen sulfide in the second portion of lithium source spray droplets and the second portion of hydrogen sulfide gas is 1:0.7.

[0055] Step S005: After the reaction is completed, an inert gas (argon) is introduced to completely replace the hydrogen sulfide gas in the fluidized bed reactor, and the temperature is cooled to room temperature to obtain a crude product, which is then discharged; the crude product is washed with ethanol, filtered, dried, and sanded to obtain the final product, lithium sulfide.

[0056] This embodiment also provides lithium sulfide prepared by the above method, the purity of which is 99.89wt% as measured by a carbon sulfur analyzer (to detect C / S content) and ICP full element scanning; the purity of D 50 The particle size is 8.4 μm, and the particle size distribution width (Span = (D 90 -D 10 ) / D 50 ) is 0.774.

[0057] Example 3 This embodiment provides a method for preparing high-purity, low-cost lithium sulfide, and the specific steps are as follows: Step S001: D 50 Precursor powder with a particle size of 0.1 μm was put into the fluidized bed reactor, and the carrier gas (nitrogen) was purged into the fluidized bed reactor. The carrier gas (nitrogen) purging flow rate was controlled from 5 L / min to 30 L / min to keep the precursor powder in the fluidized bed reactor continuously fluidized, and preheated to 650°C and kept warm.

[0058] Step S002: adding 0.5 mol / L lithium naphthalene Li(C 10The tetrahydrofuran solution of lithium naphthalenide (i.e., the lithium source solution) is divided into two portions. Subsequently, the spraying rate is controlled at 200 mL / min, and each portion of the lithium source solution is sprayed through a spraying device to form small droplets with a particle size of 5 μm, forming the first portion of lithium source spray droplets and the second portion of lithium source spray droplets.

[0059] Step S003: The first portion of lithium source spray droplets enters the fluidized bed reactor and contacts the fluidized precursor powder, coating the outer surface of the precursor powder.

[0060] Step S004: At a feeding rate of 30 L / h, the first portion of hydrogen sulfide gas is continuously fed into the fluidized bed reactor. The total feeding and reaction time of the first portion of hydrogen sulfide gas is controlled at 0.5 h. After the lithium source reacts with hydrogen sulfide, the feeding of hydrogen sulfide gas is stopped; then the second portion of lithium source spray droplets enters the fluidized bed reactor. After the transportation of the second portion of lithium source spray droplets is completed, the second portion of hydrogen sulfide gas is continuously fed into the fluidized bed reactor at a feeding rate of 30 L / h, and the total feeding and reaction time of the second portion of hydrogen sulfide gas is controlled at 2.5 h, and the reaction between the lithium source and hydrogen sulfide continues.

[0061] In Step S003 and Step S004, the mass ratio of the first portion of lithium source spray droplets to the second portion of lithium source spray droplets is 10:90.

[0062] In each portion of lithium source spray droplets and each portion of hydrogen sulfide gas used, the molar ratio of lithium naphthalenide to hydrogen sulfide is 1:1; that is, the molar ratio of lithium naphthalenide to hydrogen sulfide in the first portion of lithium source spray droplets and the first portion of hydrogen sulfide gas is 1:1; the molar ratio of lithium naphthalenide to hydrogen sulfide in the second portion of lithium source spray droplets and the second portion of hydrogen sulfide gas is 1:1.

[0063] Step S005: After the reaction ends, an inert gas (nitrogen) is introduced to completely displace the hydrogen sulfide gas in the fluidized bed reactor. After cooling to room temperature, the crude product is obtained and discharged; after the crude product is washed with N,N-dimethylformamide, it is filtered, dried, and polished to obtain the final product lithium sulfide.

[0064] This example also provides lithium sulfide prepared by the aforementioned method. The purity measured by a carbon-sulfur analyzer (detecting the C / S content) and ICP full-element scanning is 99.93 wt%; the D 50 particle size is 0.5 μm, and the particle size distribution width (Span = (D 90 -D 10 ) / D 50 ) is 1.2, and the particle size distribution diagram is as shown in Figure 2 Figure

[0065] Example 4 This example provides a method for preparing lithium sulfide with high purity and low cost, and the specific steps are as follows: Step S001: Put the precursor powder with a particle size of 3 μm of D 50 into a fluidized bed reactor, purge the carrier gas (nitrogen) into the fluidized bed reactor, and control the purge flow rate of the carrier gas (nitrogen) to increase from 15 L / min to 40 L / min, keep the precursor powder in the fluidized bed reactor in a continuous fluidized state, and preheat it to 660 °C for heat preservation.

[0066] Step S002: Divide the water / ethanol solution of lithium hydroxide with a concentration of 100 g / L (i.e., the lithium source solution) into two portions. Subsequently, control the spraying rate to be 400 mL / min. Each portion of the lithium source solution is sprayed through a spraying device to form small droplets with a particle size of 10 μm, forming the first portion of lithium source spray droplets and the second portion of lithium source spray droplets.

[0067] Among them, in the water / ethanol solution of lithium hydroxide, the volume ratio of water to ethanol as the solvent is 9:1.

[0068] Step S003: The first portion of lithium source spray droplets enters the fluidized bed reactor, contacts with the fluidized precursor powder, and coats on the outer surface of the precursor powder.

[0069] Step S004: Continuously introduce the first portion of hydrogen sulfide gas into the fluidized bed reactor at an introduction rate of 110 L / h, control the total introduction and reaction time of the first portion of hydrogen sulfide gas to be 2 h, stop introducing hydrogen sulfide gas after the lithium source reacts with hydrogen sulfide; then the second portion of lithium source spray droplets enters the fluidized bed reactor. After the spraying of the second portion of lithium source spray droplets is completed, continue to introduce the second portion of hydrogen sulfide gas into the fluidized bed reactor at an introduction rate of 110 L / h, and control the total introduction and reaction time of the second portion of hydrogen sulfide gas to be 6 h, and continue to make the lithium source react with hydrogen sulfide.

[0070] In Step S003 and Step S004, the mass ratio of the first portion of lithium source spray droplets to the second portion of lithium source spray droplets is 20:80.

[0071] In each portion of lithium source spray droplets and each portion of hydrogen sulfide gas used, the molar ratio of lithium hydroxide to hydrogen sulfide is 1:2; that is, the molar ratio of lithium hydroxide to hydrogen sulfide in the first portion of lithium source spray droplets and the first portion of hydrogen sulfide gas is 1:2; the molar ratio of lithium hydroxide to hydrogen sulfide in the second portion of lithium source spray droplets and the second portion of hydrogen sulfide gas is 1:2.

[0072] Step S005: After the reaction ends, introduce an inert gas (nitrogen) to completely displace the hydrogen sulfide gas in the fluidized bed reactor. After cooling to room temperature, obtain the crude product and discharge it; after the crude product is washed with acetonitrile, it is filtered, dried, and polished to obtain the final product lithium sulfide.

[0073] This embodiment also provides lithium sulfide prepared by the aforementioned method. The purity is measured to be 99.77 wt% by a carbon-sulfur analyzer (detecting C / S content) and ICP full-element scanning; the D 50 particle size is 12.3 μm by laser diffraction method, and the particle size distribution width (Span = (D 90 - D 10 ) / D 50 ) is 1.22.

[0074] Comparative Example 1 The preparation method of lithium sulfide in Comparative Example 1 adopts the technical solution of Example 1, and the difference is that: without using the precursor powder, the lithium source spray droplets are directly sprayed into the fluidized bed reactor, and then hydrogen sulfide gas is introduced for reaction.

[0075] The lithium sulfide finally prepared by the preparation method of Comparative Example 1 is measured to have a purity of 97.56 wt% by a carbon-sulfur analyzer (detecting C / S content) and ICP full-element scanning; the D 50 particle size is 10 μm by laser diffraction method, and the particle size distribution width (Span = (D 90 - D10) / D50) is 5.23. After analysis, after the lithium source spray droplets enter the fluidized bed reactor, the formed small lithium source droplets have no matrix to adhere to and are prone to self-aggregation, forming not only particles with larger particle sizes, but also the particle size distribution is uncontrollable; at the same time, the formed larger particles will also cause incomplete reaction with hydrogen sulfide, resulting in a decrease in purity.

[0076] Comparative Example 2 The preparation method of lithium sulfide in Comparative Example 2 adopts the technical solution of Example 1, and the difference is that: the first portion of lithium source spray droplets and the second portion of lithium source spray droplets are combined and changed to be sprayed into the fluidized bed reactor all at once.

[0077] The lithium sulfide finally prepared by the preparation method of Comparative Example 2 is measured to have a purity of 98.10 wt% by a carbon-sulfur analyzer (detecting C / S content) and ICP full-element scanning; the D 50 particle size is 1.5 μm by laser diffraction method, and the particle size distribution width (Span = (D 90 - D10) / D50) is 2.7. After analysis, during the one-time spraying process, an overly thick coating layer is formed on the surface of the precursor powder, increasing the difficulty of the reaction between hydrogen sulfide and the inner-layer lithium source, resulting in a decrease in the purity of the finally prepared lithium sulfide.

[0078] Unless otherwise specified, the percentages used in the present invention are all mass percentages.

[0079] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing high-purity, low-cost lithium sulfide, characterized in that: The following steps are involved: Step S001, putting the precursor powder into a fluidized bed reactor, continuously introducing an inert gas into the fluidized bed reactor to keep the precursor powder in the fluidized bed reactor fluidized, and preheating to 610-660° C. and keeping the temperature; The precursor powder is D 50 Lithium sulfide with a particle size of 0.1-3 μm; Step S002, dividing the lithium source melt or lithium source solution into 2-5 portions, spraying them into lithium source spray droplets in subsequent steps and entering the fluidized bed reactor; The lithium source melt is a melt of lithium chloride and / or lithium hydroxide; The solute of the lithium source solution is lithium naphthalene or lithium hydroxide; Step S003, the first portion of lithium source spray droplets enters the fluidized bed reactor to coat the precursor powder; Step S004, after the first portion of hydrogen sulfide gas is introduced into the fluidized bed reactor for reaction, the introduction of hydrogen sulfide gas is stopped; the aforementioned operation is repeated, the remaining portions of the lithium source spray droplets enter the fluidized bed reactor in sequence, and after each portion of the lithium source spray droplets enters the fluidized bed reactor, a corresponding portion of hydrogen sulfide gas is introduced into the fluidized bed reactor for reaction; until the last portion of the lithium source spray liquid enters the fluidized bed reactor, the last portion of hydrogen sulfide gas is introduced into the fluidized bed reactor for reaction; Step S005, after the reaction is completed, the temperature is lowered to obtain a crude product; the crude product is post-treated to obtain lithium sulfide.

2. The method for preparing high-purity, low-cost lithium sulfide according to claim 1, characterized in that: In step S002, the method for preparing the lithium source melt is to melt lithium chloride and / or lithium hydroxide in an inert gas environment at a melting temperature of 500-630° C. to obtain the lithium source melt.

3. The method for preparing high-purity, low-cost lithium sulfide according to claim 1, characterized in that: In the step S002, the particle size of the lithium source spray droplets is 3-15 μm; The spray rate is 50-400 mL / min.

4. The method for preparing high-purity, low-cost lithium sulfide according to claim 1, characterized in that: In the step S004, the total mass of the latter portion of lithium source spray droplets is controlled to be greater than the total mass of the former portion of lithium source spray droplets.

5. The method for preparing high-purity, low-cost lithium sulfide according to claim 1, characterized in that: In the step S004, the molar ratio of the lithium source to hydrogen sulfide in each portion of the lithium source spray droplets and the corresponding portion of the hydrogen sulfide gas is controlled to be 1:0.6-2.

6. The method for preparing high-purity, low-cost lithium sulfide according to claim 1, characterized in that: In step S004, when the lithium source spray droplets are prepared using lithium source melt, the total reaction time of introducing hydrogen sulfide gas is 2-6 hours; when the lithium source spray droplets are prepared using lithium source solution, the total reaction time of introducing hydrogen sulfide gas is 2-8 hours.

7. The method for preparing high-purity, low-cost lithium sulfide according to claim 1, characterized in that: In step S004, after the first portion of hydrogen sulfide gas is introduced into the fluidized bed reactor for reaction, the introduction of hydrogen sulfide gas is stopped; after the second portion of the lithium source spray liquid enters the fluidized bed reactor, the second portion of hydrogen sulfide gas is introduced into the fluidized bed reactor for reaction; The mass ratio of the first lithium source spray droplets to the second lithium source spray droplets is 10-30:70-90.

8. The method for preparing high-purity, low-cost lithium sulfide according to claim 1, characterized in that: In step S005, the post-treatment is to wash the crude product with an organic solvent, filter, dry and crush to obtain lithium sulfide.

9. The method for preparing high-purity, low-cost lithium sulfide according to claim 8, characterized in that: The organic solvent is at least one of the following: ethanol, dimethyl sulfoxide, N,N-dimethylformamide, and acetonitrile.

10. A lithium sulfide prepared by the method according to any one of claims 1 to 9, wherein the D 50 The particle size is 0.2-15μm, the purity is 99.40-99.99wt%, and the particle size distribution width is 0.75-2.4.

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