A method for preparing high-purity lithium sulfide using battery-grade metallic lithium

Abstract

The present invention provides a method for preparing high-purity lithium sulfide using battery-grade metallic lithium. The method comprises the following steps: step A: placing metallic lithium and corresponding sulfur powder in a sealed container in proportion under inert conditions; step B: placing the sealed container containing lithium and sulfur powder in step A in a vacuum oven for 2-4 hours; step C: crushing the crude lithium sulfide product obtained after the primary reaction by a crusher under inert gas. The method for preparing high-purity lithium sulfide using battery-grade metallic lithium of the present invention has simple and practical process, low production cost, low pollution, and high production safety. The prepared high-purity lithium sulfide has small primary particles, high purity, good crystallinity, and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to a method for preparing high-purity lithium sulfide by utilizing battery-grade metallic lithium. Background Art

[0002] Lithium-ion batteries are not only widely used in consumer electronics and communications, but also have broad development prospects in electric vehicles, smart grids and other fields. At present, commercial lithium batteries generally use liquid batteries. Although they have good high conductivity, they have problems such as insufficient electrochemical and thermal stability and poor safety. Replacing liquid batteries with inorganic solid-state batteries can well avoid the above problems. At present, inorganic solid electrolytes are relatively close to commercial applications. Among them, sulfide electrolytes have the advantages of high ionic conductivity, easy to form skeleton structure, and good electrochemical stability, which have attracted great attention from academia and the business community. Lithium sulfide is an important raw material for synthesizing sulfide solid electrolytes, but its high price restricts the promotion of lithium sulfide solid-state batteries. According to public reports, Toyota, Samsung and other companies have launched mature sulfide solid-state battery structures, and it is expected that lithium sulfide solid-state battery cars will be commercialized in 2025. Summary of the invention

[0003] Based on this, it is necessary to provide a method for preparing high-purity lithium sulfide using battery-grade metallic lithium to address the above problems.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A method for preparing high-purity lithium sulfide using battery-grade metallic lithium, the method comprising the following steps:

[0006] A. Primary batching: put metallic lithium and corresponding sulfur powder into a sealed container in an inert condition according to the molar ratio;

[0007] B. Primary reaction: Put the sealed container containing metallic lithium and sulfur powder in step A into a vacuum oven and keep it warm for a period of time, take it out and wait for cooling to room temperature to obtain a pale yellow lithium sulfide crude material;

[0008] C. Primary pulverization: Under an inert gas, the crude lithium sulfide product obtained after the primary reaction is pulverized by a pulverizer to obtain a crude lithium sulfide powder;

[0009] D. Secondary batching: Under inert gas, take out the crude lithium sulfide product of the powder, weigh it, then add sulfur powder, stir and mix evenly, and put it into a container;

[0010] E. Secondary reaction: Place the container containing the crude lithium sulfide product in a vacuum drying oven and heat it under vacuum for a period of time. Take it out, cool it to room temperature, and crush it to obtain white lithium sulfide.

[0011] F. Ball milling: The crushed white lithium sulfide is ball milled under the protection of inert gas to obtain high-purity white lithium sulfide with uniform particle size, and its main content reaches more than 99.9%.

[0012] Furthermore, the sealed container involved in step A is made of titanium, and the amount of metallic lithium put into the sealed container does not exceed 0.025 kg / L to prevent the metallic lithium from reacting with sulfur to release a large amount of heat and damage the sealed container.

[0013] Furthermore, the sealed container containing lithium and sulfur powder in step B is placed in a vacuum oven at 250-350° C. for 2-4 hours, and the metallic lithium reacts with the sulfur at high temperature to obtain a mixture of lithium sulfide and a small amount of metallic lithium and sulfur.

[0014] Furthermore, the crude lithium sulfide product in step C is crushed by a crusher to a particle size of 50-300 meshes to increase the specific surface area of ​​the residual metallic lithium and make the next step reaction more complete.

[0015] Furthermore, in step D, 0.2-2.5% sulfur powder is added based on the mass of the crude lithium sulfide, and the mixture is stirred and mixed evenly to allow the sulfur to fully contact with the residual metallic lithium.

[0016] Furthermore, the inert gas in steps A, C, D, E and F is argon.

[0017] Furthermore, the container containing the crude lithium sulfide product in step E is placed in a vacuum drying oven at 450-600° C. for vacuum insulation for 2-4 hours, and the residual metallic lithium and sulfur are completely reacted through a secondary calcination reaction at a higher temperature, and the excess sulfur is vaporized and removed under high temperature vacuum to obtain a pure high-purity lithium sulfide product.

[0018] The present invention discloses a method for preparing high-purity lithium sulfide using battery-grade metallic lithium. The metallic lithium and sulfur are difficult to react under normal temperature conditions. While sulfur is in a liquid state above 100°C, the melting point of metallic lithium is 180°C. At 250°C-350°C, when the two substances are in a liquid state, their contact surface will be increased, thereby reacting. Controlling the reaction temperature at 250°C-350°C can make the reaction more gentle and avoid violent heat release of the reaction. After the initial reaction, most of the metallic lithium (about 95% or more) has reacted. At the same time, the remaining ductile metallic lithium after the high temperature reaction treatment is easy to change to a hard and brittle state, and after being crushed into lithium powder, the contact area is increased. The remaining metallic lithium powder and the added sulfur can fully and completely react under high temperature conditions of 450-600°C, and the excess sulfur will be vaporized and separated under vacuum conditions. After being crushed, the primary particles of the lithium sulfide are finer, the crystal state is better, and the particle size is uniform, the consistency is good, and the activity is high.

[0019] Currently, the price of battery-grade lithium metal is about 3 million yuan per ton, and the price of high-grade sulfur powder is around 1,000 to 2,000 yuan per ton. The final cost of high-purity lithium sulfide prepared by the reaction of lithium metal and sulfur will be less than 2,000 yuan / kg after mass production, while the current commercial lithium sulfide price is generally 10,000 yuan / kg. Therefore, the cost of high-purity lithium sulfide prepared by the reaction of battery-grade lithium metal and sulfur will be able to greatly reduce costs, ultimately facilitating the full promotion of lithium sulfide solid electrolytes.

[0020] The method of preparing high-purity lithium sulfide using battery-grade metallic lithium of the present invention has the advantages of simple and practical process, low production cost, no pollution and high production safety compared with the prior art. The prepared high-purity lithium sulfide has uniform particle size, good consistency and high activity, and is suitable for industrial production. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to embodiments, but the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0023] The present invention provides a method for preparing high-purity lithium sulfide using battery-grade metallic lithium, comprising the following steps:

[0024] A. Primary batching: put metallic lithium and corresponding sulfur powder into a sealed container in an inert condition according to the molar ratio;

[0025] B. Primary reaction: Put the sealed container containing metallic lithium and sulfur powder in step A into a vacuum oven and keep it warm for a period of time, take it out and wait for cooling to room temperature to obtain a pale yellow lithium sulfide crude material;

[0026] C. Primary pulverization: Under an inert gas, the crude lithium sulfide product obtained after the primary reaction is pulverized by a pulverizer to obtain a crude lithium sulfide powder;

[0027] D. Secondary batching: Under inert gas, take out the crude lithium sulfide product of the powder, weigh it, then add sulfur powder, stir and mix evenly, and put it into a container;

[0028] E. Secondary reaction: Place the container containing the crude lithium sulfide product in a vacuum drying oven and heat it under vacuum for a period of time. Take it out, cool it to room temperature, and crush it to obtain white lithium sulfide.

[0029] F. Ball milling: The crushed white lithium sulfide is ball milled under the protection of inert gas to obtain high-purity white lithium sulfide with uniform particle size, and its main content reaches more than 99.9%.

[0030] Furthermore, the sealed container involved in step A is made of titanium, and the amount of metallic lithium put into the sealed container does not exceed 0.025 kg / L to prevent the metallic lithium from reacting with sulfur to release a large amount of heat and damage the sealed container.

[0031] Furthermore, the sealed container containing lithium and sulfur powder in step B is placed in a vacuum oven at 250-350° C. for 2-4 hours, and the metallic lithium reacts with the sulfur at high temperature to obtain a mixture of lithium sulfide and a small amount of metallic lithium and sulfur.

[0032] Furthermore, the crude lithium sulfide product in step C is crushed by a crusher to a particle size of 50-300 meshes to increase the specific surface area of ​​the residual metallic lithium and make the next step reaction more complete.

[0033] Furthermore, in step D, 0.2-2.5% sulfur powder is added based on the mass of the crude lithium sulfide, and the mixture is stirred and mixed evenly to allow the sulfur to fully contact with the residual metallic lithium.

[0034] Furthermore, the inert gas in steps A, C, D, E and F is argon.

[0035] Furthermore, the container containing the crude lithium sulfide product in step E is placed in a vacuum drying oven at 450-600° C. for vacuum insulation for 2-4 hours, and the residual metallic lithium and sulfur are completely reacted through a secondary calcination reaction at a higher temperature, and the excess sulfur is vaporized and removed under high temperature vacuum to obtain a pure high-purity lithium sulfide product.

[0036] The present invention discloses a method for preparing high-purity lithium sulfide using battery-grade metallic lithium. The metallic lithium and sulfur are difficult to react under normal temperature conditions. However, sulfur is in a liquid state above 100°C, and the melting point of metallic lithium is 180°C. When the two substances are in a liquid state, their contact surface will be increased, thereby reacting. Controlling the reaction temperature at 250°C to 350°C can make the reaction more gentle and avoid violent heat release of the reaction. After the initial reaction, most of the metallic lithium (about 95% or more) has reacted. At the same time, the remaining ductile metallic lithium after the high temperature reaction treatment is easy to change to a hard and brittle state, and after being crushed into lithium powder, the contact area is increased. The remaining metallic lithium powder and the added sulfur can fully and completely react under high temperature conditions of 450 to 600°C, and the excess sulfur will be vaporized and separated under vacuum conditions. After being crushed, the primary particles of the lithium sulfide are finer, the crystal state is better, and the particle size is uniform, the consistency is good, and the activity is high.

[0037] This method creatively invents a secondary calcination reaction to prepare high-purity lithium sulfide, whose main content is ≥99.9%. The specific principle is that in the first reaction, battery-grade metallic lithium and sulfur powder are used to carry out a liquid-liquid reaction in a sealed container at a relatively high temperature to control the intensity of the reaction and make the reaction proceed gently. In the second reaction, coarse lithium sulfide powder crushed to 50-300 mesh is mixed with sulfur powder, and a gas-liquid reaction is carried out under high temperature and high vacuum conditions, so that the reaction can be completely sufficient, that is, the metallic lithium remaining in the first reaction is completely reacted, and the excess sulfur overflows the reaction container in a vaporized state. Through the two calcination reactions at different temperatures, the obtained lithium sulfide can be ball-milled to obtain high-purity white lithium sulfide with uniform particle size and good consistency, and its main content reaches more than 99.9%.

[0038] The method of preparing high-purity lithium sulfide using battery-grade metallic lithium of the present invention has the advantages of simple and practical process, low production cost, no pollution and high production safety compared with the prior art. The prepared high-purity lithium sulfide has uniform particle size, good consistency and high activity, and is suitable for industrial production.

[0039] Example 1

[0040] A. Primary batching: Under argon conditions, 0.05 kg of metallic lithium and corresponding sulfur powder are placed in a 5 L sealed container at a molar ratio of 2:1.05 under inert conditions.

[0041] B. Primary reaction: Place the sealed container containing lithium and sulfur powder in step A into a 250°C vacuum oven for 4 hours. Then take it out and wait for it to cool to room temperature to obtain a pale yellow lithium sulfide crude material.

[0042] C. Primary crushing: Under argon conditions, the crude lithium sulfide product obtained after the primary reaction is crushed into 300 meshes by a crusher.

[0043] D. Secondary batching: Under argon conditions, take out the crushed lithium sulfide crude product, weigh it, then add 2.5% sulfur powder, stir and mix evenly, and put it into a 5L container.

[0044] E. Secondary reaction: Under argon conditions, place the container containing the crude lithium sulfide product into a 600°C vacuum drying oven for vacuum insulation for 2 hours, take it out, cool it to room temperature, and crush it to obtain white lithium sulfide.

[0045] F. Ball milling: The crushed white lithium sulfide is ball milled at 300 rad / min for 60 min under argon protection to obtain high-purity white lithium sulfide with uniform particle size and good consistency, and its main content reaches 99.93%.

[0046] Example 2

[0047] A. Primary batching: Under argon conditions, 0.065 kg of metallic lithium and corresponding sulfur powder were placed in a 7 L sealed container at a molar ratio of 2:0.98 under inert conditions.

[0048] B. Primary reaction: Place the sealed container containing lithium and sulfur powder in step A into a 280°C vacuum oven for 2.5 hours. Then take it out and wait for it to cool to room temperature to obtain a pale yellow lithium sulfide crude material.

[0049] C. Primary crushing: Under argon conditions, the crude lithium sulfide product obtained after the primary reaction is crushed into 200 meshes by a crusher.

[0050] D. Secondary batching: Under argon conditions, take out the crushed lithium sulfide crude product, weigh it, then add 1.5% sulfur powder, stir and mix evenly, and put it into a 7.5L container.

[0051] E. Secondary reaction: Under argon conditions, place the container containing the crude lithium sulfide product into a 515°C vacuum drying oven for vacuum insulation for 3 hours, take it out, cool it to room temperature, and crush it to obtain white lithium sulfide.

[0052] F. Ball milling: The crushed white lithium sulfide is ball milled at 350 rad / min for 85 min under argon protection to obtain high-purity white lithium sulfide with uniform particle size and good consistency, and its main content reaches 99.92%.

[0053] Example 3

[0054] A. Primary batching: Under argon conditions, 0.1 kg of metallic lithium and corresponding sulfur powder are placed in a 10 L sealed container at a molar ratio of 2:0.95 under inert conditions.

[0055] B. Primary reaction: Place the sealed container containing lithium and sulfur powder in step A into a 350°C vacuum oven for 2 hours. Then take it out and wait for it to cool to room temperature to obtain a pale yellow lithium sulfide crude material.

[0056] C. Primary crushing: Under argon conditions, the crude lithium sulfide product obtained after the primary reaction is crushed into 50 meshes by a crusher.

[0057] D. Secondary batching: Under argon conditions, take out the crushed lithium sulfide crude product, weigh it, then add 0.2% sulfur powder, stir and mix evenly, and put it into a 10L container.

[0058] E. Secondary reaction: Under argon conditions, place the container containing the crude lithium sulfide product into a 150°C vacuum drying oven for vacuum insulation for 4 hours, take it out, cool it to room temperature, and crush it to obtain white lithium sulfide.

[0059] F. Ball milling: The crushed white lithium sulfide is ball milled at 400 rad / min for 90 min under argon protection to obtain high-purity white lithium sulfide with uniform particle size and good consistency, and its main content reaches 99.94%.

[0060] The above only describes the specific embodiments of the present invention, but cannot be regarded as the protection scope of the present invention. Any equivalent changes or modifications made according to the design spirit of the present invention should be considered to fall within the protection scope of the present invention.

Claims

1. A method for preparing high-purity lithium sulfide using battery-grade metallic lithium, characterized in that: The method comprises the following steps: A. Primary batching: put metallic lithium and corresponding sulfur powder into a sealed container in an inert condition according to the molar ratio; B. Primary reaction: Put the sealed container containing metallic lithium and sulfur powder in step A into a vacuum oven and keep it warm for a period of time, take it out and wait for cooling to room temperature to obtain a pale yellow lithium sulfide crude material; C. Primary pulverization: Under an inert gas, the crude lithium sulfide product obtained after the primary reaction is pulverized by a pulverizer to obtain a crude lithium sulfide powder; D. Secondary batching: Under inert gas, take out the crude lithium sulfide product of the powder, weigh it, then add sulfur powder, stir and mix evenly, and put it into a container; E. Secondary reaction: put the container containing the crude lithium sulfide product into a vacuum drying oven, heat and keep it in vacuum for a period of time, take it out, cool it to room temperature, and crush it to obtain white lithium sulfide; F. Ball milling: The crushed white lithium sulfide is ball milled under the protection of inert gas to obtain high-purity white lithium sulfide with uniform particle size, and its main content reaches more than 99.9%; In step A, the metallic lithium and the corresponding sulfur powder are in a molar ratio of 2:0.95-1, the amount of metallic lithium added is 0.05-0.1 kg, and the volume of the sealed container is 5-10 L; The temperature of the vacuum drying oven in step B is 250-350° C., and the insulation time is 2-4 hours; The particle size of the crude lithium sulfide after being crushed by the crusher in step C is 50-300 mesh; The sulfur powder added to the lithium sulfide crude material in step D is 0.2-2.5% of its mass, and the volume of the container is not less than 1.1 times the volume of the mixture; The temperature of the vacuum drying oven described in step E is 450-600° C., and the holding time is 2-4 hours; The rotation speed of the ball mill described in step F is 300-400 rad / min, and the ball milling is 60-90 min.