Preparation method of high-purity lithium sulfide and high-purity lithium sulfide

Abstract

The invention provides a preparation method of high-purity lithium sulfide and the high-purity lithium sulfide.The method comprises the following steps that S1, a lithium source and sulfur powder are mixed in an organic solvent, ground and dried, and a uniformly-mixed material is obtained; s2, putting the uniformly mixed material into a reactor for reaction, and performing roasting reaction on the mixed material which is in a flowing and suspended state in the reactor to obtain low-quality lithium sulfide; and S3, introducing organic sulfur source gas into the low-quality lithium sulfide, and then continuing roasting reaction for purification to obtain the high-quality lithium sulfide. By utilizing the characteristic that lithium hydroxide and organic sulfur source gas are fully contacted and reacted, the content of lithium hydroxide in the product is effectively reduced, the purity of the lithium sulfide product is improved, and the corrosion of an equipment system is reduced; according to the preparation method of the high-purity lithium sulfide, the organic sulfur source gas is utilized to perform purification reaction in the roasting process, and further purification of the lithium sulfide by an organic solvent is not needed, so that the production cost is effectively reduced, and the production process is simplified.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium sulfide, and in particular to a preparation method of high-purity lithium sulfide and high-purity lithium sulfide. Background Art

[0002] Lithium sulfide is the cathode material of high-capacity lithium-sulfur batteries and an important component of new high-energy, high-safety solid-state lithium-ion batteries. It is also the raw material for the preparation of solid sulfide electrolytes. Its production process development, optimization and commercial application are increasingly receiving widespread attention and attention.

[0003] The existing lithium sulfide purification methods mainly include alcohol solvent purification method and high-temperature hydrogen reduction purification method, but the lithium sulfide obtained by the alcohol solvent purification method has weak reaction activity, and the high-temperature hydrogen reduction purification method has harsh conditions and high requirements for equipment. At the same time, the side reactions of these two purification methods during the purification process are difficult to control. The present invention provides a lithium sulfide purification method, which uses an organic sulfur source gas to purify the lithium sulfide in the lithium sulfide synthesis stage, without the generation of side reactions, and without further organic solvent purification of lithium sulfide, high-activity and high-purity lithium sulfide can be obtained, effectively reducing the production cost and simplifying the production process. Summary of the invention

[0004] Based on this, the purpose of the present invention is to provide a method for preparing high-purity lithium sulfide and high-purity lithium sulfide.

[0005] The invention provides the following technical solutions: A method for preparing high-purity lithium sulfide, comprising the following steps:

[0006] Step S1: mixing a lithium source and sulfur powder in an organic solvent, grinding and drying to obtain a mixed material;

[0007] Step S2: placing the mixed material into a reactor for reaction, and obtaining low-quality lithium sulfide after calcination of the mixed material in a flowing and suspended state in the reactor;

[0008] Step S3: introducing an organic sulfur source gas into the low-quality lithium sulfide, and then continuing the roasting reaction for purification to obtain the high-quality lithium sulfide.

[0009] Furthermore, in the step S1, the lithium source and the sulfur powder are mixed in the organic solvent at a molar ratio of Li2O to S of 1:0.5-2.

[0010] Furthermore, in step S1, the organic solvent is one or more combinations of methanol, acetonitrile, ethanol and acetone.

[0011] Furthermore, in step S2, the reactor is a rotary kiln.

[0012] Furthermore, in step S2, the mixed material in a flowing or suspended state in the rotary kiln is achieved by combining one or more of the following methods: kiln body rotation, kiln body tilt angle, and hot air flow in the kiln.

[0013] Furthermore, the calcination reaction in the method for preparing high-purity lithium sulfide adopts a step-by-step multi-stage temperature increase reaction.

[0014] Furthermore, in the step-type multi-stage temperature-raising reaction: the first stage reaction temperature is 200-400°C, the second stage reaction temperature is 400-600°C and the third stage reaction temperature is 675-775°C; in the step S2, the mixture is subjected to the first stage reaction temperature and the second stage reaction temperature of the roasting reaction in turn to obtain low-quality lithium sulfide; in the step S3, the high-quality lithium sulfide is obtained after the mixture is subjected to the third stage reaction temperature of the roasting reaction.

[0015] Furthermore, in step S3, the organic sulfur source gas is one or more of methyl mercaptan, methyl sulfide, carbonyl sulfide and dimethyl disulfide.

[0016] Furthermore, in step S3, the rate of introduction of the organic sulfur source gas is controlled at 1 L / h to 10 L / h.

[0017] A high-purity lithium sulfide is obtained by the above-mentioned preparation method.

[0018] The beneficial effects of the invention are:

[0019] The method for preparing high-purity lithium sulfide proposed by the present invention utilizes the characteristics of lithium hydroxide and organic sulfur source gas fully contacting and reacting to effectively reduce the content of lithium hydroxide in the product, improve the purity of the lithium sulfide product, and reduce the corrosion of the equipment system;

[0020] The method for preparing high-purity lithium sulfide proposed by the present invention utilizes an organic sulfur source gas to perform a purification reaction during the roasting process, and does not require further organic solvent purification of lithium sulfide, thereby effectively reducing the production cost and simplifying the production process;

[0021] The present invention proposes a method for preparing high-purity lithium sulfide, in which lithium hydroxide or lithium carbonate is calcined with sulfur powder, and sulfuric acid is produced using a mature sulfurization process, thereby effectively optimizing the product structure and maximizing the economic benefits of the enterprise.

[0022] The invention provides a method for preparing high-purity lithium sulfide, which has the advantages of simple process, convenient operation and control, low corrosion to equipment, low cost, large-scale production and better suitability for industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the process of the present invention. DETAILED DESCRIPTION

[0024] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, 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 disclosure of the present invention more thorough and comprehensive.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. 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 related listed items.

[0026] First of all, it is known in the prior art that the physicochemical properties of lithium sulfide, such as poor solubility and easy hydrolysis, determine that the purification of this substance is difficult. This shows that the purification method of lithium sulfide is best solved as much as possible during the synthesis process of lithium sulfide. The present invention provides a method for preparing high-purity lithium sulfide, which uses an organic sulfur source gas for purification during the lithium sulfide synthesis stage, without the generation of side reactions, and without the need for further organic solvent purification of lithium sulfide, to obtain high-activity and high-purity lithium sulfide, effectively reducing the production cost and simplifying the production process; please refer to the following embodiments for details:

[0027] Embodiment 1:

[0028] A method for preparing high-purity lithium sulfide, such as Figure 1 As shown, the following steps are included:

[0029] Step S1: mixing a lithium source and sulfur powder in an organic solvent, grinding and drying to obtain a mixed material;

[0030] It can be understood that by mixing the lithium source and sulfur powder in an organic solvent and grinding them by ball milling, sand milling or a combination of these methods, the sulfur powder and the lithium source are tightly combined, which is conducive to achieving uniform coating, thereby improving the conversion efficiency of lithium sulfide.

[0031] Specifically, lithium hydroxide and sulfur powder are mixed in ethanol at a molar ratio of LiOH:S=1:1, ground by a ball mill, and dried to obtain a mixed material; wherein the drying temperature is 100°C.

[0032] Step S2: placing the mixed material into a reactor for reaction, and obtaining low-quality lithium sulfide after calcination of the mixed material in a flowing and suspended state in the reactor;

[0033] It can be understood that in order to enhance the contact environment between the solid material and the organic gas, the mixed material is in a flowing and suspended state in the rotary kiln. The mixed material is continuously contacted and mixed with the gas phase, thereby avoiding the problem of uneven mixing in the reaction, improving the purity of lithium sulfide while improving the conversion efficiency of lithium sulfide; the organic sulfur source gas is heated during the sintering process and further reacts with the unreacted LiOH and the by-product Li2O: 2LiOH+CH3SH→Li2S+CO↑+H2O, removing the excess unreacted LiOH and the by-product Li2O, improving the purity of lithium sulfide while improving the conversion efficiency of lithium sulfide;

[0034] Specifically, the mixed material prepared in step S1 is placed in a reactor for reaction, and the kiln body is rotated in the reactor to make the mixed material flow and suspended, and then low-quality lithium sulfide is obtained after roasting reaction; the roasting reaction is specifically as follows: the mixed material is reacted at a first reaction temperature of 300°C for 5h in an inert atmosphere, and then reacted at a second reaction temperature of 500°C for 4h to obtain a low-grade lithium sulfide composite; wherein the heating rate is 5°C / min, the content of low-quality lithium sulfide in the obtained composite is 75wt.%, and the inert gas is argon.

[0035] Step S3: introducing an organic sulfur source gas into the low-quality lithium sulfide, and then continuing the roasting reaction for purification to obtain the high-quality lithium sulfide.

[0036] It can be understood that the organic sulfur source gas not only provides an additional sulfur source but also reacts with the lithium source, which positively promotes the reaction between the sulfur powder and the lithium source, greatly reduces the generation of Li2O in the final product, and is beneficial to improve the purity of the Li2S product.

[0037] Specifically, methyl mercaptan gas is introduced into the low-quality lithium sulfide in step S2, and the gas introduction rate is controlled at 10 L / h. The temperature is 700° C. in an inert atmosphere for 5 hours, which can be understood as the third stage reaction temperature, and finally high-quality lithium sulfide is obtained, wherein the lithium sulfide content is 99.0 wt.%.

[0038] Embodiment 2:

[0039] A method for preparing high-purity lithium sulfide, such as Figure 1 As shown, the following steps are included:

[0040] Step S1: lithium hydroxide and sulfur powder are mixed in methanol at a molar ratio of LiOH:S=1:1.5, ground by a ball mill, and dried to obtain a mixed material; wherein the drying temperature is 100°C.

[0041] Step S2: placing the mixed material prepared in step S1 into a reactor for reaction, rotating the kiln body in the reactor to make the mixed material flow and suspended, and then obtaining low-quality lithium sulfide after roasting reaction; the roasting reaction is specifically as follows: the mixed material is reacted at a first reaction temperature of 300° C. for 5 hours in an inert atmosphere, and then reacted at a second reaction temperature of 500° C. for 4 hours to obtain a low-grade lithium sulfide complex; wherein the heating rate is 5° C. / min, the content of low-quality lithium sulfide in the obtained complex is 75wt.%, and the inert gas is argon.

[0042] Step S3: introducing methyl mercaptan gas into the low-quality lithium sulfide in step S2 at a gas introduction rate of 1 L / h. The reaction temperature is 700° C. in an inert atmosphere for 5 hours, which can be understood as the third stage reaction temperature, and finally obtaining high-quality lithium sulfide, wherein the lithium sulfide content is 99.0 wt.%.

[0043] Embodiment three:

[0044] A method for preparing high-purity lithium sulfide, such as Figure 1 As shown, the following steps are included:

[0045] Step S1: lithium hydroxide and sulfur powder are mixed in ethanol at a molar ratio of LiOH:S=1:1, ground by a ball mill, and dried to obtain a mixed material; wherein the drying temperature is 100°C.

[0046] Step S2: placing the mixed material prepared in step S1 into a reactor for reaction, rotating the kiln body in the reactor to make the mixed material flow and suspended, and then obtaining low-quality lithium sulfide after roasting reaction; the roasting reaction is specifically as follows: the mixed material reacts at a first reaction temperature of 300° C. for 5 hours in an inert atmosphere, and then reacts at a second reaction temperature of 400° C. for 4 hours to obtain a low-grade lithium sulfide complex; wherein the heating rate is 5° C. / min, the content of low-quality lithium sulfide in the obtained complex is 75wt.%, and the inert gas is argon.

[0047] Step S3: introducing carbonyl sulfide gas into the low-quality lithium sulfide in step S2 at a gas introduction rate of 5 L / h. The reaction temperature is 700° C. in an inert atmosphere for 5 h, which can be understood as the third stage reaction temperature, and finally obtaining high-quality lithium sulfide, wherein the lithium sulfide content is 98.8 wt.%.

[0048] Embodiment 4:

[0049] A method for preparing high-purity lithium sulfide, such as Figure 1 As shown, the following steps are included:

[0050] Step S1: lithium hydroxide and sulfur powder are mixed in ethanol at a molar ratio of LiOH:S=1:1.5, ground by a ball mill, and dried to obtain a mixed material; wherein the drying temperature is 100°C.

[0051] Step S2: placing the mixed material prepared in step S1 into a reactor for reaction, rotating the kiln body in the reactor to make the mixed material flow and suspended, and then obtaining low-quality lithium sulfide after roasting reaction; the roasting reaction is specifically as follows: the mixed material is reacted at a first reaction temperature of 300° C. for 5 hours in an inert atmosphere, and then reacted at a second reaction temperature of 500° C. for 4 hours to obtain a low-grade lithium sulfide complex; wherein the heating rate is 5° C. / min, the content of low-quality lithium sulfide in the obtained complex is 75wt.%, and the inert gas is argon.

[0052] Step S3: Dimethyl sulfide gas is introduced into the low-quality lithium sulfide in step S2 at a gas introduction rate of 5 L / h. The reaction is carried out at 675° C. in an inert atmosphere for 5 hours, which can be understood as the third stage reaction temperature, and finally high-quality lithium sulfide is obtained, wherein the lithium sulfide content is 99.1 wt.%.

[0053] Embodiment five:

[0054] On the other hand, this embodiment provides a high-purity lithium sulfide, which is obtained by the preparation method described in any one of the above embodiments one, two, three, and four.

[0055] The preparation method provided by the present invention has a reaction principle as follows (taking lithium hydroxide as an example):

[0056] 6LiOH+4S→2Li2S+2Li2S2O3;

[0057] 2Li2S2O3→Li2S+SO3↑;

[0058] 2LiOH+CH3SH→Li2S+CO↑+H2O;

[0059] Sulfur powder reacts with lithium hydroxide to generate lithium sulfide and lithium thiosulfate, and then lithium thiosulfate is decomposed at high temperature to obtain lithium sulfide. Finally, methyl mercaptan is introduced for further purification reaction to purify lithium sulfide and generate high-purity lithium sulfide. Therefore, high-purity lithium sulfide can be obtained without purification by organic solvents, and the corrosion to equipment is reduced. The operation is safe and easy to process production.

[0060] In summary, the method for preparing high-purity lithium sulfide proposed in the present invention utilizes the characteristics of lithium hydroxide and organic sulfur source gas fully contacting and reacting, effectively reduces the content of lithium hydroxide in the product, improves the purity of the lithium sulfide product, and reduces the corrosion of the equipment system;

[0061] The preparation method of high-purity lithium sulfide proposed in the present invention utilizes organic sulfur source gas to carry out purification reaction during the roasting process, and no further organic solvent is required to purify the lithium sulfide, thereby effectively reducing the production cost and simplifying the production process; that is, after a one-step reaction, low-quality lithium sulfide is purified, and the product purity can reach more than 99%.

[0062] The present invention provides a method for preparing high-purity lithium sulfide, wherein a mature sulfidation process can be used to produce sulfuric acid, thereby effectively optimizing the product structure and maximizing the economic benefits of the enterprise.

[0063] The invention provides a method for preparing high-purity lithium sulfide, which has the advantages of simple process, convenient operation and control, low corrosion to equipment, low cost, large-scale production and better suitability for industrialization.

[0064] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0065] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the patent of the present invention. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing high-purity lithium sulfide, characterized in that: The following steps are involved: Step S1: mixing a lithium source and sulfur powder in an organic solvent, grinding and drying to obtain a mixed material; Step S2: placing the mixed material into a reactor for reaction, and obtaining low-quality lithium sulfide after calcination of the mixed material in a flowing and suspended state in the reactor; Step S3: introducing an organic sulfur source gas into the low-quality lithium sulfide, and then continuing the roasting reaction for purification to obtain the high-quality lithium sulfide.

2. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In the step S1, the lithium source and the sulfur powder are mixed in the organic solvent at a molar ratio of Li2O to S of 1:0.5-2.

3. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In the step S1, the organic solvent is one or more of methanol, acetonitrile, ethanol and acetone.

4. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In the step S2, the mixture is subjected to a calcination reaction to obtain low-quality lithium sulfide; wherein the reactor is a rotary kiln.

5. The method for preparing high-purity lithium sulfide according to claim 4, characterized in that: In the step S2, the mixed material in the flowing and suspended state in the rotary kiln is realized by combining one or more of the following methods: the rotation of the kiln body, the inclination angle of the kiln body, and the flow of hot air in the kiln.

6. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: The calcination reaction in the method for preparing high-purity lithium sulfide adopts a step-by-step multi-stage temperature increase reaction.

7. The method for preparing high-purity lithium sulfide according to claim 6, characterized in that: In the step-by-step multi-stage temperature-raising reaction, the reaction temperature of the first stage is 200-400°C, the reaction temperature of the second stage is 400-600°C and the reaction temperature of the third stage is 675-775°C.

8. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In step S3, the organic sulfur source gas is one or more of methyl mercaptan, methyl sulfide, carbonyl sulfide and dimethyl disulfide.

9. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In the step S3, the introduction rate of the organic sulfur source gas is controlled at 1 L / h to 10 L / h.

10. A high-purity lithium sulfide, characterized in that: The high-purity lithium sulfide is obtained by the preparation method according to any one of claims 1 to 9.

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