A method for preparing high-purity lithium sulfide by a low-temperature melting method
By combining a low-temperature melting method with a modified sulfur ion stabilizer, the impurity problem during the high-temperature preparation of lithium sulfide was solved, enabling the low-cost preparation of high-purity lithium sulfide and reducing energy consumption and impurity content.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HANGZHOU WANLIDA NEW ENERGY TECH CO LTD
- Filing Date
- 2026-05-12
- Publication Date
- 2026-06-19
AI Technical Summary
Existing methods for preparing lithium sulfide suffer from problems such as raw material volatilization and decomposition under high-temperature conditions, introduction of impurities, complex equipment, and high costs, making it difficult to obtain high-purity products.
High-purity lithium sulfide was prepared by using a low-temperature melting method combined with a modified sulfide ion stabilizer, through stirring, mixing, low-temperature melting reaction, crushing, and vacuum drying. The modified sulfide ion stabilizer inhibited impurity formation and reduced volatilization through coordination and hydrogen bonding.
This method enables the efficient preparation of high-purity lithium sulfide under mild reaction conditions, reducing energy consumption, simplifying separation steps, and significantly reducing impurity content.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium sulfide preparation technology, and in particular to a method for preparing high-purity lithium sulfide by low-temperature melting. Background Technology
[0002] Lithium sulfide is an important inorganic compound with wide applications in lithium-ion batteries, catalysts, and optical materials. With the rapid development of related industries, the demand for high-purity lithium sulfide is increasing daily.
[0003] Chinese Patent CN119243178A discloses a method for preparing lithium sulfide. This application provides a method for preparing lithium sulfide using metallic lithium or a lithium alloy as the negative electrode, a carbon-sulfur composite as the positive electrode, and a solid electrolyte membrane as the electrolyte layer. An electrochemical reaction is carried out via discharge from an electrochemical workstation. Metallic lithium or the lithium alloy reacts at the negative electrode to obtain metallic lithium ions, while the carbon-sulfur composite reacts at the positive electrode to obtain sulfur ions. The metallic lithium ions are transported to the positive electrode through the solid electrolyte membrane and react with the sulfur ions to obtain the target product, lithium sulfide.
[0004] Chinese Patent CN113788458A: Belonging to the field of battery technology, it discloses a lithium sulfide and its preparation method and apparatus. The preparation method of lithium sulfide includes the following steps: preheating the lithium source, then adding sulfur in batches for mixing, and stirring and shearing under the conditions of 120-425℃ and 50-150Pa to obtain lithium sulfide.
[0005] Currently, the main methods for preparing lithium sulfide include high-temperature solid-phase method, gas-phase method, and solution method. The high-temperature solid-phase method typically requires high temperatures for the reaction, which not only consumes a lot of energy but also easily leads to raw material volatilization and product decomposition under high temperatures, and may also introduce impurities, affecting product purity. The gas-phase method has harsh reaction conditions, requires complex equipment, and the reaction process is difficult to control, resulting in high production costs. Although the solution method has lower reaction temperatures, it easily generates byproducts during the reaction, and subsequent separation and purification steps are complex, making it difficult to obtain high-purity lithium sulfide products. Summary of the Invention
[0006] To address the above problems, this invention provides a method for preparing high-purity lithium sulfide using a low-temperature melting method, the operation steps of which are as follows, in parts by mass: S1 Raw Material Mixing: Place 68-78 parts of sodium sulfide, 88-106 parts of lithium chloride, and 0.6-1.8 parts of modified sulfur ion stabilizer in a mixing device, and mix thoroughly under nitrogen protection to obtain mixed raw materials; S2 Low-Temperature Melting Reaction: The mixed raw materials are transferred to a reaction vessel and subjected to a low-temperature melting reaction under nitrogen protection; S3 post-processing: After the reaction is completed, cool to room temperature, crush the reaction product, wash 2-3 times with anhydrous ethanol, filter, and vacuum dry to obtain high-purity lithium sulfide.
[0007] The stirring speed of S1 is 300-500 rpm.
[0008] The heating rate of the S2 low-temperature melting reaction is 5-10℃ / min, the temperature is raised to 350-450℃, and the reaction time is 3-5h.
[0009] The vacuum degree of the S3 vacuum drying is 0.08-0.1 MPa, the drying temperature is 60-80℃, and the drying time is 4-6 hours.
[0010] The preparation method of the modified sulfide ion stabilizer is as follows: A1: According to the mass fractions, add 30-50 parts of pentaerythritol glycidyl ether, 120-150 parts of dichloroethane, 10-17 parts of 2,5-dimercaptothiadiazole dilithium salt, and 2-4 parts of ethylenediamine to a reaction vessel, stir and heat to 40-60℃ under a nitrogen atmosphere, and react for 2-4 hours; A2: After the reaction is complete, dichloroethane is removed by rotary evaporation and then dried under vacuum to obtain a modified sulfide ion stabilizer.
[0011] The modified sulfide ion stabilizer was prepared by vacuum drying at a temperature of 50-60℃ for 5-7 hours.
[0012] I. Reaction Mechanism of Modified Sulfide Ion Stabilizer Ethylenediamine, acting as a basic catalyst, can abstract a proton from the -SLi group in the 2,5-dimercaptothiadiazole dilithium salt, generating a more nucleophilic thiol anion. This thiol anion attacks the potentiophilic site of the epoxy ring in the pentaerythritol glycidyl ether molecule, inducing a ring-opening reaction of the epoxy ring and forming an oxygen anion intermediate. Subsequently, it is converted into a stable hydroxyl group via proton transfer, completing a single addition reaction. Since the pentaerythritol glycidyl ether molecule contains multiple epoxy groups, and the 2,5-dimercaptothiadiazole dilithium salt contains multiple reactant -SLi groups, the remaining functional groups after the single reaction will continue to undergo addition reactions, ultimately forming a three-dimensional cross-linked polymer-type modified sulfide ion stabilizer containing CS bonds, hydroxyl groups, and a thiadiazole heterocyclic structure.
[0013] II. Technical Effects The modified sulfur ion stabilizer prepared by this invention can anchor S in the molten system through coordination or hydrogen bonding. 2- To avoid S 2- It reacts with oxygen to generate oxidative impurities, while simultaneously reducing sulfur through physical encapsulation. 2-It reduces the volatilization loss; the hydroxyl groups in its molecule can also coordinate with metal ions, preventing the formation of inorganic impurities, thereby significantly reducing the total amount of impurities in lithium sulfide products.
[0014] The modified sulfide ion stabilizer has good thermal stability, can adapt to the reaction conditions of the low-temperature melting preparation process, will not undergo thermal decomposition, and can synergistically suppress side reactions in the reaction process; moreover, the stabilizer is an organic polymer, which has significantly different physical properties from lithium sulfide, can be easily separated by simple means without residue, and effectively ensures the purity of lithium sulfide.
[0015] Compared with traditional high-temperature preparation processes, the low-temperature melting process used in this invention has milder reaction conditions, which can reduce the volatilization and decomposition of raw materials caused by high temperatures, and at the same time reduce energy consumption. Combined with the effect of modified sulfur ion stabilizers, the reaction process can be further optimized, the generation of by-products can be reduced, and high-purity lithium sulfide can be prepared efficiently. Detailed Implementation
[0016] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description is provided in conjunction with embodiments and comparative examples: 1. Lithium sulfide purity: Detected using X-ray diffraction (XRD). 2. Impurity content: The content of major impurities (such as sodium and chlorine) in the product is detected by inductively coupled plasma optical emission spectrometry (ICP-OES).
[0017] Example 1 A method for preparing high-purity lithium sulfide by low-temperature melting, comprising the following steps: S1 Raw Material Mixing: Place 68g sodium sulfide, 88g lithium chloride, and 0.6g modified sulfur ion stabilizer in a mixing device and mix thoroughly under nitrogen protection to obtain mixed raw materials; S2 Low-temperature melting reaction: The mixed raw materials are transferred to the reaction vessel, and under nitrogen protection, the temperature is increased to 350℃ at a heating rate of 5℃ / min, and the reaction is carried out for 3 hours; S3 Post-processing: After the reaction is completed, the product is cooled to room temperature, crushed, washed twice with anhydrous ethanol, filtered, and vacuum dried to obtain high-purity lithium sulfide.
[0018] The stirring speed of S1 is 300 rpm.
[0019] The heating rate of the S2 low-temperature melting reaction is 5℃ / min, the temperature is raised to 350℃, and the reaction time is 3h.
[0020] The vacuum degree of the S3 vacuum drying is 0.08 MPa, the drying temperature is 60℃, and the drying time is 4 hours.
[0021] The preparation method of the modified sulfide ion stabilizer is as follows: A1: Add 30g pentaerythritol glycidyl ether, 120g dichloroethane, 10g 2,5-dimercaptothiadiazole dilithium salt (CAS No.: 140481-31-8), and 2g ethylenediamine to a reaction vessel. Under a nitrogen atmosphere, stir and heat to 40°C, and react for 2 hours. A2: After the reaction is complete, dichloroethane is removed by rotary evaporation and then dried under vacuum to obtain a modified sulfide ion stabilizer.
[0022] The vacuum drying temperature is 50℃ and the time is 5 hours.
[0023] Example 2 A method for preparing high-purity lithium sulfide by low-temperature melting, comprising the following steps: S1 Raw Material Mixing: Place 72g sodium sulfide, 96g lithium chloride, and 1g modified sulfur ion stabilizer in a mixing device and mix thoroughly under nitrogen protection to obtain mixed raw materials; S2 Low-temperature melting reaction: The mixed raw materials are transferred to the reactor and heated to 380°C at a heating rate of 6°C / min under nitrogen protection, and the reaction is carried out for 4 hours. S3 Post-processing: After the reaction is completed, the product is cooled to room temperature, crushed, washed twice with anhydrous ethanol, filtered, and vacuum dried to obtain high-purity lithium sulfide.
[0024] The stirring speed of S1 is 400 rpm.
[0025] The heating rate of the S2 low-temperature melting reaction is 6℃ / min, the temperature is raised to 380℃, and the reaction time is 4h.
[0026] The vacuum degree of the S3 vacuum drying is 0.09 MPa, the drying temperature is 65℃, and the drying time is 5 hours.
[0027] The preparation method of the modified sulfide ion stabilizer is as follows: A1: Add 35g pentaerythritol glycidyl ether, 130g dichloroethane, 12g 2,5-dimercaptothiadiazole dilithium salt (CAS No.: 140481-31-8), and 3g ethylenediamine to a reaction vessel, stir and heat to 45°C under a nitrogen atmosphere, and react for 3 hours. A2: After the reaction is complete, dichloroethane is removed by rotary evaporation and then dried under vacuum to obtain a modified sulfide ion stabilizer.
[0028] The vacuum drying temperature is 55℃ and the time is 6 hours.
[0029] Example 3 A method for preparing high-purity lithium sulfide by low-temperature melting, comprising the following steps: S1 Raw Material Mixing: Place 75g sodium sulfide, 100g lithium chloride, and 1.5g modified sulfur ion stabilizer in a mixing device and mix thoroughly under nitrogen protection to obtain mixed raw materials; S2 Low-temperature melting reaction: The mixed raw materials are transferred to the reactor and heated to 430°C at a heating rate of 8°C / min under nitrogen protection, and reacted for 4 hours. S3 Post-processing: After the reaction is completed, the product is cooled to room temperature, crushed, washed three times with anhydrous ethanol, filtered, and vacuum dried to obtain high-purity lithium sulfide.
[0030] The stirring speed of S1 is 400 rpm.
[0031] The heating rate of the S2 low-temperature melting reaction is 8℃ / min, the temperature is raised to 430℃, and the reaction time is 4h.
[0032] The vacuum degree of the S3 vacuum drying is 0.09 MPa, the drying temperature is 75℃, and the drying time is 5 hours.
[0033] The preparation method of the modified sulfide ion stabilizer is as follows: A1: Add 45g pentaerythritol glycidyl ether, 140g dichloroethane, 16g 2,5-dimercaptothiadiazole dilithium salt (CAS No.: 140481-31-8), and 3g ethylenediamine to a reaction vessel. Under a nitrogen atmosphere, stir and heat to 55°C, and react for 3 hours. A2: After the reaction is complete, dichloroethane is removed by rotary evaporation and then dried under vacuum to obtain a modified sulfide ion stabilizer.
[0034] The vacuum drying temperature is 55℃ and the time is 6 hours.
[0035] Example 4 A method for preparing high-purity lithium sulfide by low-temperature melting, comprising the following steps: S1 Raw Material Mixing: Place 78g sodium sulfide, 106g lithium chloride, and 1.8g modified sulfur ion stabilizer in a mixing device and mix thoroughly under nitrogen protection to obtain mixed raw materials; S2 Low-temperature melting reaction: The mixed raw materials are transferred to the reactor and heated to 450°C at a heating rate of 10°C / min under nitrogen protection, and the reaction is carried out for 5 hours. S3 Post-processing: After the reaction is completed, the product is cooled to room temperature, crushed, washed three times with anhydrous ethanol, filtered, and vacuum dried to obtain high-purity lithium sulfide.
[0036] The stirring speed of S1 is 500 rpm.
[0037] The heating rate of the S2 low-temperature melting reaction is 10℃ / min, the temperature is raised to 450℃, and the reaction time is 5h.
[0038] The vacuum degree of the S3 vacuum drying is 0.1 MPa, the drying temperature is 80℃, and the drying time is 6 hours.
[0039] The preparation method of the modified sulfide ion stabilizer is as follows: A1: Add 50g pentaerythritol glycidyl ether, 150g dichloroethane, 17g 2,5-dimercaptothiadiazole dilithium salt (CAS No.: 140481-31-8), and 4g ethylenediamine to a reaction vessel. Under a nitrogen atmosphere, stir and heat to 60°C, and react for 4 hours. A2: After the reaction is complete, dichloroethane is removed by rotary evaporation and then dried under vacuum to obtain a modified sulfide ion stabilizer.
[0040] The vacuum drying temperature is 60℃ and the time is 7 hours.
[0041] Comparative Example 1 A method for preparing high-purity lithium sulfide by low-temperature melting, comprising the following steps: S1 Raw Material Mixing: Place 68g of sodium sulfide and 88g of lithium chloride in a mixing device, and mix thoroughly under nitrogen protection to obtain mixed raw materials; S2 Low-temperature melting reaction: The mixed raw materials are transferred to the reaction vessel, and under nitrogen protection, the temperature is increased to 350℃ at a heating rate of 5℃ / min, and the reaction is carried out for 3 hours; S3 Post-processing: After the reaction is completed, the product is cooled to room temperature, crushed, washed twice with anhydrous ethanol, filtered, and vacuum dried to obtain high-purity lithium sulfide.
[0042] The stirring speed of S1 is 300 rpm.
[0043] The heating rate of the S2 low-temperature melting reaction is 5℃ / min, the temperature is raised to 350℃, and the reaction time is 3h.
[0044] The vacuum degree of the S3 vacuum drying is 0.08 MPa, the drying temperature is 60℃, and the drying time is 4 hours.
[0045] Comparative Example 2 A method for preparing high-purity lithium sulfide by low-temperature melting, comprising the following steps: S1 Raw Material Mixing: Place 68g sodium sulfide, 88g lithium chloride, and 0.6g stabilizer in a mixing device and mix thoroughly under nitrogen protection to obtain mixed raw materials; S2 Low-temperature melting reaction: The mixed raw materials are transferred to the reaction vessel, and under nitrogen protection, the temperature is increased to 350℃ at a heating rate of 5℃ / min, and the reaction is carried out for 3 hours; S3 Post-processing: After the reaction is completed, the product is cooled to room temperature, crushed, washed twice with anhydrous ethanol, filtered, and vacuum dried to obtain high-purity lithium sulfide.
[0046] The stirring speed of S1 is 300 rpm.
[0047] The heating rate of the S2 low-temperature melting reaction is 5℃ / min, the temperature is raised to 350℃, and the reaction time is 3h.
[0048] The vacuum degree of the S3 vacuum drying is 0.08 MPa, the drying temperature is 60℃, and the drying time is 4 hours.
[0049] The stabilizer is 2,5-dimercaptothiadiazole bislithium salt, CAS No.: 140481-31-8.
[0050] Comparative Example 3 A method for preparing high-purity lithium sulfide by low-temperature melting, comprising the following steps: S1 Raw Material Mixing: Place 68g sodium sulfide, 88g lithium chloride, and 0.6g stabilizer in a mixing device and mix thoroughly under nitrogen protection to obtain mixed raw materials; S2 Low-temperature melting reaction: The mixed raw materials are transferred to the reaction vessel, and under nitrogen protection, the temperature is increased to 350℃ at a heating rate of 5℃ / min, and the reaction is carried out for 3 hours; S3 Post-processing: After the reaction is completed, the product is cooled to room temperature, crushed, washed twice with anhydrous ethanol, filtered, and vacuum dried to obtain high-purity lithium sulfide.
[0051] The stirring speed of S1 is 300 rpm.
[0052] The heating rate of the S2 low-temperature melting reaction is 5℃ / min, the temperature is raised to 350℃, and the reaction time is 3h.
[0053] The vacuum degree of the S3 vacuum drying is 0.08 MPa, the drying temperature is 60℃, and the drying time is 4 hours.
[0054] The stabilizer is pentaerythritol glycidyl ether.
[0055] The test results of the examples and comparative examples are shown in Table 1.
[0056] Table 1
[0057] The test results of the examples and comparative examples in Table 1 clearly show that the lithium sulfide product prepared by the method of the present invention has a much higher purity than the products without the addition of a modified sulfide ion stabilizer (Comparative Example 1) or with only the addition of a single-component stabilizer (Comparative Examples 2 and 3). At the same time, the sodium and chlorine impurity contents in the product are also significantly lower than those in the comparative examples. This result fully demonstrates that the present invention, through the combination of a "low-temperature melting process + a specific modified sulfide ion stabilizer," can effectively solve the problems of low purity and high impurities in traditional preparation methods, exhibiting significant technical advantages.
[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for preparing high-purity lithium sulfide by low-temperature melting, comprising the following steps, in parts by mass: S1 Raw Material Mixing: Place 68-78 parts of sodium sulfide, 88-106 parts of lithium chloride, and 0.6-1.8 parts of modified sulfur ion stabilizer in a mixing device, and mix thoroughly under nitrogen protection to obtain mixed raw materials; S2 Low-Temperature Melting Reaction: The mixed raw materials are transferred to a reaction vessel and subjected to a low-temperature melting reaction under nitrogen protection; S3 post-processing: After the reaction is completed, cool to room temperature, crush the reaction product, wash 2-3 times with anhydrous ethanol, filter, and vacuum dry to obtain high-purity lithium sulfide. The modified sulfide ion stabilizer is prepared by reacting pentaerythritol glycidyl ether, 2,5-dimercaptothiadiazole bislithium salt, and ethylenediamine.
2. The method for preparing high-purity lithium sulfide by low-temperature melting according to claim 1, characterized in that: The stirring speed of S1 is 300-500 rpm.
3. The method for preparing high-purity lithium sulfide by low-temperature melting according to claim 1, characterized in that: The heating rate of the S2 low-temperature melting reaction is 5-10℃ / min, the temperature is raised to 350-450℃, and the reaction time is 3-5h.
4. The method for preparing high-purity lithium sulfide by low-temperature melting according to claim 1, characterized in that: The vacuum degree of the S3 vacuum drying is 0.08-0.1 MPa, the drying temperature is 60-80℃, and the drying time is 4-6 hours.
5. The method for preparing high-purity lithium sulfide by low-temperature melting according to claim 1, characterized in that: The preparation method of the modified sulfide ion stabilizer is as follows: A1: According to the mass fractions, add 30-50 parts of pentaerythritol glycidyl ether, 120-150 parts of dichloroethane, 10-17 parts of 2,5-dimercaptothiadiazole dilithium salt, and 2-4 parts of ethylenediamine to a reaction vessel, stir and heat to 40-60℃ under a nitrogen atmosphere, and react for 2-4 hours; A2: After the reaction is complete, dichloroethane is removed by rotary evaporation and then dried under vacuum to obtain a modified sulfide ion stabilizer.
6. The method for preparing high-purity lithium sulfide by low-temperature melting according to claim 5, characterized in that: The vacuum drying temperature is 50-60℃, and the time is 5-7 hours.