Process for the preparation of high purity lithium sulfide

Abstract

The present application relates to a method for preparing high-purity lithium sulfide, and belongs to the technical field of high-purity lithium sulfide preparation. The present application solves the technical problem of providing a method for preparing high-purity lithium sulfide. The method comprises the following steps: a. grinding and mixing: uniformly mixing a sulfur source and a lithium source, while adding anhydrous hydrazine, and obtaining a reaction material after the feeding is completed; b. defoaming link: placing the reaction material into a defoaming device for defoaming treatment for 1-3 hours, and obtaining lithium sulfide slurry after the bubbles are eliminated; c. drying: spray drying the lithium sulfide slurry at 150-200 DEG C to obtain a high-purity lithium sulfide product. The present application prepares high-purity lithium sulfide by liquid phase method with anhydrous material, reduces the water brought into the reaction system, thereby reducing the hydrolysis of lithium sulfide, and obtains a high-purity lithium sulfide product with a purity greater than 99%. The method is simple, non-polluting, green and environmentally friendly, low in energy consumption, low in requirements for equipment, low in cost, and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to a method for preparing high-purity lithium sulfide, and belongs to the field of high-purity lithium sulfide preparation technology. Background Technology

[0002] Lithium sulfide, as a key precursor material for the synthesis of sulfur-based solid electrolytes, is mainly produced by two major methods: solvent methods and pyrolysis methods. Solvent methods include: preparing lithium metal or organolithium with elemental sulfur in an organic solvent; and preparing lithium metal or organolithium with hydrogen sulfide in an organic solvent. High-temperature pyrolysis methods include: preparing lithium sulfide precursors (one or more of lithium sulfate, lithium sulfite, lithium hydrogen sulfate, and lithium dithionate) with relevant reducing agents at high temperatures. However, these methods are difficult to promote industrially due to the high risk of raw materials, harsh production environment, and high cost.

[0003] Patent CN112678781A discloses a novel method for preparing lithium sulfide. This technology boasts advantages such as simple operation, no use of hazardous raw materials, low energy consumption, low equipment requirements, stable batch production, no generation of toxic gases, and no secondary pollution. Specifically, the technology involves mixing and grinding sulfur powder and lithium hydroxide monohydrate, followed by a redox reaction under a reducing agent hydrazine hydrate atmosphere. After spray drying, lithium sulfide product is obtained, with a main content reaching over 90%. However, it cannot produce high-purity lithium sulfide products. Summary of the Invention

[0004] To address the above deficiencies, the technical problem solved by this invention is to provide a method for preparing high-purity lithium sulfide.

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

[0006] a. Grinding and mixing: The sulfur source and lithium source are mixed evenly, and anhydrous hydrazine is added at the same time. After the addition is completed, the reaction material is obtained; the lithium source is lithium oxide, lithium thiosulfate or lithium sulfite, and the sulfur source is sulfur powder, lithium thiosulfate or lithium sulfite.

[0007] b. Defoaming process: The reactants are placed in a defoaming device and defoamed for 1 to 3 hours. After the bubbles are eliminated, lithium sulfide slurry is obtained.

[0008] c. Drying: The lithium sulfide slurry is spray-dried at 150-200℃ to obtain high-purity lithium sulfide product.

[0009] In one embodiment of the present invention, the molar ratio of lithium source, sulfur source and anhydrous hydrazine is Li2O:S:N2H4 = 1:1~2.2:1~2.

[0010] In one embodiment of the present invention, in step b, the defoaming treatment is vacuum defoaming or inert gas defoaming.

[0011] In one embodiment of the present invention, the pressure of vacuum defoaming is below 0.1 MPa.

[0012] In one embodiment of the present invention, the inert gas used for defoaming is helium, neon, argon, krypton, xenon, or radon.

[0013] In one embodiment of the present invention, the purity of the high-purity lithium sulfide is >99%.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] This invention prepares high-purity lithium sulfide from anhydrous materials via a liquid-phase method, reducing the introduction of moisture into the reaction system and thus minimizing the hydrolysis of lithium sulfide, resulting in a high-purity lithium sulfide product with a purity greater than 99%. The method is simple, pollution-free, environmentally friendly, energy-efficient, requires minimal equipment, and has low cost, making it suitable for industrial production. Attached Figure Description

[0016] Figure 1 The image shows the XRD pattern of the lithium sulfide product prepared in Example 1 of this invention. Detailed Implementation

[0017] The present invention provides a method for preparing high-purity lithium sulfide, comprising the following steps:

[0018] a. Grinding and mixing: The sulfur source and lithium source are mixed evenly, and anhydrous hydrazine is added at the same time. After the addition is completed, the reaction material is obtained; the lithium source is lithium oxide, lithium thiosulfate or lithium sulfite, and the sulfur source is sulfur powder, lithium thiosulfate or lithium sulfite.

[0019] b. Defoaming process: The reactants are placed in a defoaming device and defoamed for 1 to 3 hours. After the bubbles are eliminated, lithium sulfide slurry is obtained.

[0020] c. Drying: The lithium sulfide slurry is spray-dried at 150-200℃ to obtain high-purity lithium sulfide product.

[0021] Studies have found that lithium sulfide, as a material with high air sensitivity, will undergo severe hydrolysis when exposed to moisture. Therefore, this invention strictly controls the added raw materials and improves the preparation method to obtain high-purity lithium sulfide products.

[0022] In one embodiment of the present invention, the lithium source is lithium oxide and the sulfur source is sulfur powder.

[0023] In one embodiment of the present invention, the molar ratio of lithium source, sulfur source and anhydrous hydrazine is Li2O:S:N2H4 = 1:1~2.2:1~2.

[0024] In one embodiment of the present invention, in step b, the defoaming treatment is vacuum defoaming or inert gas defoaming.

[0025] In one embodiment of the present invention, the pressure of vacuum defoaming is below 0.1 MPa.

[0026] Inert gas defoaming is performed at atmospheric pressure. Commonly used inert gases are suitable for this invention. In one embodiment of this invention, the inert gas used for inert gas defoaming is helium, neon, argon, krypton, xenon, or radon.

[0027] In one embodiment of the present invention, the purity of the high-purity lithium sulfide is >99%.

[0028] The specific embodiments of the present invention will be further described below with reference to examples, but the present invention is not limited to the scope of the embodiments described herein.

[0029] Example 1

[0030] (1) Weigh lithium oxide, sulfur powder and anhydrous hydrazine according to the molar ratio Li2O:S:N2H4=1:1:1. Mix the sulfur powder and lithium oxide and grind them thoroughly. Then slowly add the anhydrous hydrazine while grinding until it is completely added to obtain the reaction material.

[0031] (2) Place the reactants into a vacuum defoaming tank, evacuate to below 0.1 MPa, react for 3 hours, and obtain lithium sulfide slurry after the bubbles are completely eliminated.

[0032] (3) The lithium sulfide slurry was spray-dried at 150°C using a spray dryer to granulate it. The resulting material is a high-purity spherical lithium sulfide product, and its XRD pattern is shown below. Figure 1 Its purity and composition analysis are shown in Table 1.

[0033] Example 2

[0034] (1) Weigh lithium oxide, sulfur powder and anhydrous hydrazine according to the molar ratio Li2O:S:N2H4=1:2.2:2. Mix the sulfur powder and lithium oxide and grind them thoroughly. Then slowly add the anhydrous hydrazine while grinding until it is completely added to obtain the reaction material.

[0035] (2) Place the reactants into a vacuum defoaming tank, evacuate to below 0.1 MPa, react for 1 hour, and obtain lithium sulfide slurry after the bubbles are completely eliminated.

[0036] (3) The lithium sulfide slurry was spray-dried at 200°C using a spray dryer to granulate it. The resulting material was a high-purity spherical lithium sulfide product, and its XRD pattern was similar to... Figure 1 Similarly, its purity and composition analysis are shown in Table 1.

[0037] Example 3

[0038] (1) Weigh lithium oxide, sulfur powder and anhydrous hydrazine according to the molar ratio Li2O:S:N2H4=1:1.5:1.5. Mix the sulfur powder and lithium oxide and grind them thoroughly. Then slowly add the anhydrous hydrazine while grinding until it is completely added to obtain the reaction material.

[0039] (2) Place the reactants into a three-necked round-bottom flask with a stirrer, introduce inert gas through the gas inlet, control the gas flow rate to be 600 mL / min, the stirring rate to be 100 r / min, react for 2 h, and after the bubbles are completely eliminated, obtain lithium sulfide slurry.

[0040] (3) The lithium sulfide slurry was spray-dried at 170°C using a spray dryer to granulate it. The resulting material was a high-purity spherical lithium sulfide product, and its XRD pattern was similar to... Figure 1 Similarly, its purity and composition analysis are shown in Table 1.

[0041] Example 4

[0042] (1) Weigh out lithium sulfite and hydrazine at a ratio of 1:2 according to the molar ratio, grind and mix them evenly to obtain the reaction material.

[0043] (2) Place the reactants into a vacuum defoaming tank, evacuate to below 0.1 MPa, react for 1 hour, and obtain lithium sulfide slurry after the bubbles are completely eliminated.

[0044] (3) The lithium sulfide slurry was spray-dried at 200°C using a spray dryer to granulate it. The resulting material was a high-purity spherical lithium sulfide product, and its XRD pattern was similar to... Figure 1 Similarly, its purity and composition analysis are shown in Table 1.

[0045] Example 5

[0046] (1) The reaction material is obtained by grinding and mixing the materials evenly with a mass ratio of lithium thiosulfate: hydrazine = 1:2.

[0047] (2) Place the reactants into a three-necked round-bottom flask with a stirrer, introduce inert gas through the gas inlet, control the gas flow rate to be 600 mL / min, the stirring rate to be 100 r / min, react for 2 h, and after the bubbles are completely eliminated, obtain lithium sulfide slurry.

[0048] (3) The lithium sulfide slurry was spray-dried at 170°C using a spray dryer to granulate it. The resulting material was a high-purity spherical lithium sulfide product, and its XRD pattern was similar to... Figure 1 Similarly, its purity and composition analysis are shown in Table 1.

[0049] Comparative Example 1

[0050] (1) Weigh out lithium hydroxide monohydrate, sulfur powder and 80% hydrazine hydrate in the ratio of Li2O:S:N2H4·H2O→1:1:1. Mix the lithium hydroxide monohydrate and sulfur powder and grind them evenly. Then slowly add the hydrazine hydrate to the mixed powder while grinding until the hydrazine hydrate is completely added to obtain the reaction material.

[0051] (2) The obtained reaction material is placed in a vacuum defoaming tank, and the vacuum is drawn to below 0.1 MPa. The reaction continues until bubbles are no longer generated. The vacuum state is maintained for 3 hours. The valve of the vacuum defoaming tank is opened until the air pressure reaches the normal pressure state to obtain lithium sulfide slurry.

[0052] (3) The lithium sulfide slurry was spray-dried and granulated at 150°C using a spray dryer to obtain lithium sulfide products. The purity and composition analysis are shown in Table 1.

[0053] Comparative Example 2

[0054] (1) Weigh out lithium hydroxide monohydrate, sulfur powder and 80% hydrazine hydrate in the ratio of Li2O:S:N2H4·H2O→1:2.2:2. Mix the lithium hydroxide monohydrate and sulfur powder and grind them evenly. Then slowly add the hydrazine hydrate to the mixed powder while grinding until the hydrazine hydrate is completely added to obtain the reaction material.

[0055] (2) The obtained reaction material is placed in a vacuum defoaming tank, and the vacuum is drawn to below 0.1 MPa. The reaction continues until bubbles are no longer generated. The vacuum state is maintained for 1 hour. The valve of the vacuum defoaming tank is opened until the air pressure reaches the normal pressure state to obtain lithium sulfide slurry.

[0056] (3) The lithium sulfide slurry was spray-dried and granulated at 200°C using a spray dryer to obtain lithium sulfide products. The purity and composition analysis are shown in Table 1.

[0057] Comparative Example 3

[0058] (1) Weigh lithium oxide, sulfur powder and anhydrous hydrazine according to the molar ratio Li2O:S:N2H4=1:1:1. Mix the sulfur powder and lithium oxide and grind them thoroughly. Then slowly add the anhydrous hydrazine while grinding until it is completely added to obtain the reaction material.

[0059] (2) Place the reactants into a vacuum defoaming tank, evacuate to below 0.1 MPa, react for 3 hours, and obtain lithium sulfide slurry after the bubbles are completely eliminated.

[0060] (3) Transfer the lithium sulfide slurry to a vacuum freeze dryer and freeze dry it at a low temperature of -60℃ and a pressure of less than 100Pa for 6 hours. After drying, vacuum press the material and take it out to obtain the lithium sulfide product. Its purity and composition analysis are shown in Table 1.

[0061] Table 1

[0062] serial number <![CDATA[OH - %]]> Purity % (reverse subtraction method) (Metal-based) Na+K+Ca+Mg+Al+Si+Fe+TI% Example 1 —— ≈99.9 0.012 Example 2 —— ≈99.9 0.015 Example 3 —— ≈99.9 0.014 Example 4 —— ≈99.9 0.016 Example 5 —— ≈99.9 0.014 Comparative Example 1 2.55 ≈97.4 0.018 Comparative Example 2 3.14 ≈96.8 0.023 Comparative Example 3 1.83 ≈98.1 0.021

[0063] Note: "—" indicates not detected. The purity calculation method for the product of this invention is the reverse subtraction method: purity % = 100% - (metal-based impurities + OH- impurities)%.

Claims

1. A method for preparing high-purity lithium sulfide, characterized in that, Includes the following steps: a. Grinding and mixing: The sulfur source and lithium source are mixed evenly, and anhydrous hydrazine is added at the same time. After the addition is completed, the reaction material is obtained; the lithium source is lithium oxide, lithium thiosulfate or lithium sulfite, and the sulfur source is sulfur powder, lithium thiosulfate or lithium sulfite. b. Defoaming process: The reactants are placed in a defoaming device and defoamed for 1 to 3 hours. After the bubbles are eliminated, lithium sulfide slurry is obtained. c. Drying: The lithium sulfide slurry is spray-dried at 150-200℃ to obtain high-purity lithium sulfide product.

2. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: The molar ratio of lithium source, sulfur source and anhydrous hydrazine is Li2O:S:N2H4 = 1:1~2.2:1~2.

3. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: In step b, the defoaming process is performed using vacuum defoaming or inert gas defoaming.

4. The method for preparing high-purity lithium sulfide according to claim 3, characterized in that: The pressure for vacuum defoaming is below 0.1 MPa.

5. The method for preparing high-purity lithium sulfide according to claim 3, characterized in that: In inert gas defoaming, the inert gas is helium, neon, argon, krypton, xenon, or radon.

6. The method for preparing high-purity lithium sulfide according to claim 1, characterized in that: The purity of the high-purity lithium sulfide is >99%.

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