Method for preparing high-purity lithium sulfide based on organic amine solvent
By using aprotic organic amine solvents and rotary evaporation technology, the problems of high energy consumption, high risk, and low purity in lithium sulfide preparation have been solved, providing a low-cost, high-purity lithium sulfide preparation method suitable for high-end battery materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-03-24
AI Technical Summary
Existing lithium sulfide preparation technologies suffer from high energy consumption, high risk, high cost, or low product purity, making it difficult to meet the requirements of high-end battery materials.
High-purity lithium sulfide was prepared by using an aprotic organic amine with nitrogen-coordinating atoms as a solvent, reacting under mild conditions, and then proceeding through rotary evaporation and washing-drying steps.
It has achieved the preparation of lithium sulfide with low energy consumption, high safety, low cost and high product purity, which is suitable for high-end battery materials.
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Figure CN121717331A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of inorganic chemical material synthesis technology, specifically to a method for preparing high-purity lithium sulfide based on organic amine solvents. Background Technology
[0002] Lithium sulfide (Li2S), as a key cathode material precursor for lithium-sulfur batteries and an important raw material for sulfide solid electrolytes, has seen its market demand grow rapidly with the development of high-energy-density energy storage technologies. High-purity Li2S is crucial for ensuring the energy density, cycle stability, and safety of batteries.
[0003] Currently, the industrial preparation of lithium sulfide mainly relies on the high-temperature solid-state method, which involves reacting elemental lithium or lithium carbonate with a sulfur source in a reducing atmosphere (such as hydrogen or hydrogen sulfide) exceeding 700°C. This method has inherent drawbacks such as high energy consumption, severe equipment corrosion, and harsh reaction conditions. More seriously, the high temperature easily leads to product sintering and agglomeration, and introduces impurities such as lithium oxide (Li2O), making it difficult to meet the stringent requirements for precursor purity and uniformity in high-end battery materials.
[0004] To reduce the synthesis temperature, researchers have developed various liquid-phase synthesis routes, but all of them have obvious shortcomings: (1) Organolithium reagent method: In ether solvents such as tetrahydrofuran, alkyl lithium such as n-butyllithium reacts with sulfur. Although the conditions are mild, organolithium reagents are expensive, extremely sensitive to water and oxygen, and extremely dangerous to store and use (flammable and explosive). They also introduce organic impurities, leading to complicated post-processing and making it difficult to scale up applications. (2) Alcohol solvent method: Attempts are made to react lithium metal with sulfur in solvents such as ethanol. However, lithium metal reacts violently with alcohols to produce hydrogen gas, posing a serious safety hazard. In addition, the reaction inevitably produces lithium alcohol byproducts, which contaminate the final product and cannot obtain high-purity Li2S.
[0005] Therefore, developing a solid-state Li2S liquid-phase preparation route that can overcome the above-mentioned defects and integrate mildness, safety, low cost, and high purity has significant industrial value. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of existing lithium sulfide preparation technologies, such as high energy consumption, high risk, high cost, or low product purity, and to provide a method for preparing high-purity lithium sulfide based on organic amine solvents. The method of this invention for preparing lithium sulfide not only features mild reaction conditions, a simple process flow, high safety, but also produces high-purity products.
[0007] The core concept of this invention lies in: creatively using an aprotic organic amine with nitrogen-coordinating atoms as a reaction solvent, utilizing its good wettability for sulfur and lithium, as well as its excellent solubility for the reaction intermediate lithium polysulfide, to promote a homogeneous and complete reaction under gentle heating, and finally efficiently removing the solvent and promoting the reaction through a rotary evaporation step. The product is obtained by crystallizing in solid form, followed by washing and drying. This preparation method has a simple process flow and produces lithium sulfide with high purity and few impurities, making it particularly suitable for high-end applications such as solid-state electrolytes.
[0008] The present invention solves the above-mentioned technical problems through the following technical solutions:
[0009] This invention provides a method for preparing high-purity lithium sulfide based on an organic amine solvent, comprising the following steps:
[0010] An anhydrous mixture containing elemental sulfur and metallic lithium is reacted in a mixed state. After the reaction is complete, the solvent is removed by rotary evaporation, followed by washing and drying to obtain high-purity lithium sulfide. The solvent in the anhydrous mixture is an aprotic organic amine with nitrogen-coordinating atoms.
[0011] In this invention, the water content of the anhydrous organic mixture is preferably not higher than 50 ppm, where water content refers to the mass concentration of water in the system as measured by the Karl Fischer coulometric method.
[0012] In this invention, the aprotic organic amine having nitrogen-coordinating atoms is preferably one or more of ethylenediamine, 1,3-propanediamine, and 1,4-butanediamine. The aprotic organic amine having nitrogen-coordinating atoms is preferably dehydrated before use.
[0013] The dehydration treatment preferably includes the following steps: co-soaking the solvent with the vacuum-activated molecular sieve, followed by filtration under inert gas protection; or, distillation after reflux with calcium hydride. The type of molecular sieve can be conventional in the art, such as 3A and / or 4A molecular sieves. The co-soaking time is preferably not less than 48 hours.
[0014] In this invention, the chemical formula of the sulfur element can be conventional in the art, such as S and / or S8. The sulfur element is generally in the form of sulfur powder, and the particle size of the sulfur powder is preferably 100-1000 mesh, such as 200 mesh, 300 mesh, 400 mesh, 600 mesh or 800 mesh.
[0015] In this invention, the morphology of the metallic lithium can be foil, powder, or shavings, preferably lithium strips and / or lithium shavings to increase the reaction contact area.
[0016] In this invention, the molar ratio of sulfur atoms in the elemental sulfur to the metallic lithium can be 1:(1.7-2.2), for example, 1:1.8, 1:1.9, 1:2.0, or 1:2.1. In the anhydrous mixture containing elemental sulfur and metallic lithium, the molar concentration of the elemental sulfur can be 0.1-0.5 mol / L, for example, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.4 mol / L, or 0.45 mol / L.
[0017] In this invention, the method for preparing the anhydrous mixture containing elemental sulfur and metallic lithium preferably includes the following steps: under an inert atmosphere, elemental sulfur and metallic lithium are added to an aprotic organic amine solvent having nitrogen coordinating atoms to form a mixture.
[0018] The inert atmosphere can be conventional in the art, such as argon. During the preparation of the anhydrous mixture containing elemental sulfur and metallic lithium, all operations are preferably carried out in a glove box with moisture and oxygen content both below 0.1 ppm, or in a closed reaction vessel.
[0019] In this invention, the reaction is generally carried out in a sealed reaction flask. The reaction temperature is preferably 30-80°C, for example 32°C, 35°C, 40°C, 45°C, 48°C, 50°C, or 55°C, more preferably 35-60°C, and is generally precisely controlled by an oil bath or water bath. The reaction time can be 0.5-4 hours, preferably 1-3 hours, for example 1 hour, 1.5 hours, or 2 hours. During the reaction in a mixed state, the mixing method can be conventional in the art, such as stirring or ultrasonication. The stirring speed can be 200-800 rpm, preferably 300-600 rpm, for example 350 rpm, 400 rpm, 450 rpm, or 500 rpm.
[0020] In this invention, the rotary evaporation is generally carried out in a rotary evaporator; the water bath temperature during rotary evaporation is preferably 40-60°C, for example 45°C, 48°C, 50°C, or 55°C; the vacuum degree during rotary evaporation is preferably -0.09 MPa to -0.1 MPa. The rotary evaporation is generally continued until a uniform solid deposit appears on the inner wall of the reaction flask and the solvent is completely evaporated.
[0021] In this invention, the solvent used for washing is preferably a non-polar organic solvent that is sensitive to water and oxygen, preferably one or more of anhydrous n-hexane, anhydrous toluene, and anhydrous diethyl ether; the number of washing cycles is preferably 2-5 times, for example 3 or 4 times; the amount of solvent used each time during the washing process is sufficient to completely submerge and rinse the solid product; the washing is preferably carried out in a glove box.
[0022] In this invention, the drying is preferably vacuum drying; the drying temperature can be 80-120°C, for example 85°C, 90°C, 100°C, or 110°C; the drying time can be 6-12 hours, for example 7 hours, 8 hours, or 10 hours; the vacuum degree during drying is preferably below -0.095 MPa. The drying is preferably carried out in a vacuum oven protected by an inert atmosphere.
[0023] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.
[0024] The reagents and raw materials used in this invention are all commercially available.
[0025] The positive and progressive effects of this invention are as follows:
[0026] (1) The preparation conditions are extremely mild: the reaction temperature is much lower than that of the traditional high temperature method (>700℃), the energy consumption is significantly reduced, and the equipment requirements are low.
[0027] (2) High safety: It avoids the use of high-risk organic lithium reagents or alcohol solvents that can react violently with lithium, and the production process is highly safe.
[0028] (3) Excellent product purity: The aprotic organic amine solvent with nitrogen coordination atoms effectively promotes the homogeneous reaction. Combined with rotary evaporation and subsequent washing and drying, impurities can be effectively removed to obtain high-purity lithium sulfide suitable for high-end electrochemical applications.
[0029] (4) Simple process and low cost: The process is simple and the raw material cost is much lower than that of the method using organic lithium reagents. It is easy to scale up production. Attached Figure Description
[0030] Figure 1 The X-ray diffraction pattern of the high-purity lithium sulfide prepared in Example 1 is shown. Detailed Implementation
[0031] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.
[0032] Example 1
[0033] In an argon-atmospheric glove box, accurately weigh 0.32 g (10 mmol, 300 mesh, chemical formula S) of sulfur powder and 0.14 g (20 mmol, 0.5 mm thick, 10 mm diameter) of lithium metal sheets and place them in a 100 mL double-necked round-bottom flask. Add 40 mL of anhydrous ethylenediamine (sulfur concentration 0.25 mol / L, water content less than 10 ppm) to the flask. Remove the sealed reaction flask from the glove box and place it on a magnetic stirrer. Under oil bath heating, stir the reaction at 40 °C and 500 rpm for 2 hours. During the reaction, the solution color gradually changes from dark yellow to light yellow. After the reaction is complete, connect the flask to a rotary evaporator and evaporate under a 50 °C water bath and a vacuum of -0.095 MPa until the solvent is completely evaporated, yielding a grayish-white solid. The solid product was transferred back to the glove box, washed three times with 20 mL of anhydrous n-hexane, and then dried at 100 °C and -0.098 MPa vacuum for 8 hours to obtain the final product, high-purity lithium sulfide. The ethylenediamine required dehydration before use: ethylenediamine was soaked together with 3A molecular sieves activated under high vacuum for 48 hours, followed by filtration through a sand core funnel under an inert atmosphere to obtain anhydrous ethylenediamine.
[0034] Example 2
[0035] Compared with Example 1, the operation and conditions were the same as in Example 1, except that the reaction temperature was adjusted to 30°C.
[0036] Example 3
[0037] Compared with Example 1, the operation and conditions were the same as in Example 1, except that the reaction temperature was adjusted to 50°C.
[0038] Example 4
[0039] Compared with Example 1, the operation and conditions are the same as in Example 1, except that the reaction time is adjusted to 1 hour.
[0040] Example 5
[0041] Compared with Example 1, the operation and conditions were the same as in Example 1, except that the amount of lithium was adjusted to 0.126 g (18 mmol).
[0042] Example 6
[0043] Compared with Example 1, the operation and conditions were the same as in Example 1, except that the particle size of the sulfur powder used was adjusted to 800 mesh.
[0044] Example 7
[0045] Compared with Example 1, the operation and conditions were the same as in Example 1, except that lithium scrap (obtained by scraping lithium strips) was used instead of lithium sheets.
[0046] Example 8
[0047] Compared with Example 1, the operation and conditions were the same as in Example 1, except that the stirring speed during the reaction was adjusted to 350 rpm.
[0048] Example 9
[0049] Compared with Example 1, except that the water bath temperature during rotary evaporation was adjusted to 45°C, all other operations and conditions were the same as in Example 1.
[0050] Example 10
[0051] Compared with Example 1, except that anhydrous toluene was used as the washing solvent, all other operations and conditions were the same as in Example 1.
[0052] Example 11
[0053] Compared with Example 1, except that the vacuum drying temperature in Example 1 was adjusted to 90°C, all other operations and conditions were the same as in Example 1.
[0054] Comparative Example 1
[0055] 0.32 g (10 mmol) of sulfur powder and 0.14 g (20 mmol) of lithium flakes were lightly mixed in an agate mortar under argon protection, and then placed into a sealed tantalum crucible. The crucible was placed in a tube furnace and heated to 700 °C at 5 °C / min under argon atmosphere, and held at that temperature for 10 hours. After natural cooling, a heavily agglomerated grayish-black product was obtained.
[0056] Comparative Example 2
[0057] In an argon-filled glove box, 0.32 g (10 mmol) of sulfur powder was dissolved in 40 mL of anhydrous THF. Under ice-water bath cooling and vigorous stirring, 12.5 mL of a 1.6 M n-butyllithium / hexane solution (containing 20 mmol n-BuLi) was slowly added dropwise. After the addition was complete, the ice bath was removed, and the reaction was continued at room temperature for 2 hours. The solvent was removed by rotary evaporation to obtain a white solid.
[0058] Comparative Example 3
[0059] Compared with Example 1, except that the solid-liquid separation method of rotary evaporation is changed to the sedimentation method described below, all other operations and conditions are the same as in Example 1.
[0060] Sedimentation: After the reaction is complete, a large amount of anhydrous diethyl ether is added to the reaction solution to precipitate the product. The precipitation process is slow, and the resulting product is gel-like, making it difficult to filter and wash thoroughly.
[0061] Comparative Example 4
[0062] Compared with Example 1, except for the use of ethylenediamine (water content greater than 250 ppm) that has not been dehydrated by molecular sieves, all other operations and conditions are the same as in Example 1.
[0063] Comparative Example 5
[0064] Compared with Example 1, except that no stirring was performed during the reaction and the reaction was allowed to stand, all other operations and conditions were the same as in Example 1.
[0065] Effect Example
[0066] The products obtained in Examples 1-11 and Comparative Examples 1-5 were characterized and their performance was tested.
[0067] 1. Phase and purity analysis: X-ray diffraction was used to analyze the phases, and the results are shown in the figure. Figure 1 And Table 1. The diffraction peaks of the product in Example 1 are in complete agreement with the Li2S standard card, with no impurity peaks.
[0068] 2. Yield calculation: Calculate the theoretical yield of Li2S based on the amount of sulfur added as reactant, and calculate the yield by comparing it with the actual yield.
[0069] 3. Impurity content analysis: The content of major impurities was analyzed using EDS elemental analysis.
[0070] The test results are shown in Table 1:
[0071] Table 1: Performance Comparison of Products from Different Examples and Comparative Examples
[0072]
[0073] According to the data in Table 1, the lithium sulfide prepared by the preparation method of the present invention has not only high purity, but also high yield and low oxygen content.
[0074] By comparing Examples 1-11 with Comparative Example 1, it can be seen that the preparation method of Comparative Example 1, which uses high-temperature calcination, not only has high energy consumption, but also contains impurities such as lithium oxide and has a high oxygen content, resulting in severe oxidation.
[0075] By comparing Examples 1-11 and Comparative Example 2, it can be seen that Comparative Example 2 uses an organolithium reagent for the reaction, resulting in a higher oxygen content and severe oxidation.
[0076] By comparing Examples 1-11 and Comparative Example 3, it can be seen that Comparative Example 3 uses sedimentation for solid-liquid separation, resulting in low lithium sulfide yield, high oxygen content, and severe oxidation.
[0077] By comparing Examples 1-11 and Comparative Example 4, it can be seen that Comparative Example 4 uses undehydrated ethylenediamine to prepare lithium sulfide, resulting in lithium sulfide containing more impurities, low yield, high oxygen content, and severe oxidation.
[0078] By comparing Examples 1-11 and Comparative Example 5, it can be seen that Comparative Example 5 adopted a static reaction method during the reaction process, which resulted in the prepared lithium sulfide containing more impurities, as well as low yield, high oxygen content, and severe oxidation.
[0079] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.
Claims
1. A method for preparing high-purity lithium sulfide based on organic amine solvent, characterized in that, Includes the following steps: An anhydrous mixture containing elemental sulfur and metallic lithium is reacted in a mixed state. After the reaction is complete, the solvent is removed by rotary evaporation, followed by washing and drying to obtain high-purity lithium sulfide. The solvent in the anhydrous mixture is an aprotic organic amine with nitrogen-coordinating atoms.
2. The method for preparing high-purity lithium sulfide based on organic amine solvent as described in claim 1, characterized in that, The water content of the anhydrous organic mixture is not higher than 50 ppm; And / or, the aprotic organic amine having a nitrogen coordinating atom is one or more of ethylenediamine, 1,3-propanediamine, and 1,4-butanediamine; And / or, the aprotic organic amine having nitrogen-coordinating atoms needs to be dehydrated before use.
3. The method for preparing high-purity lithium sulfide based on organic amine solvent as described in claim 2, characterized in that, The dehydration process includes the following steps: soaking the solvent together with a vacuum-activated molecular sieve, followed by filtration under inert gas protection; or, distilling after reflux with calcium hydride.
4. The method for preparing high-purity lithium sulfide based on organic amine solvent as described in claim 1, characterized in that, The chemical formula of the sulfur element is S and / or S8; And / or, the sulfur element is in the form of sulfur powder; the particle size of the sulfur powder is preferably 100-1000 mesh, for example 200 mesh, 300 mesh, 400 mesh, 600 mesh or 800 mesh; And / or, the lithium metal is in the form of foil, powder, or shavings.
5. The method for preparing high-purity lithium sulfide based on organic amine solvent as described in claim 1, characterized in that, The molar ratio of sulfur atoms in the sulfur element to the metallic lithium is 1:(1.7-2.2), for example, 1:1.8, 1:1.9, 1:2.0 or 1:2.1; And / or, in the anhydrous mixture containing elemental sulfur and metallic lithium, the molar concentration of elemental sulfur is 0.1-0.5 mol / L, for example 0.15 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.4 mol / L or 0.45 mol / L.
6. The method for preparing high-purity lithium sulfide based on organic amine solvent as described in claim 1, characterized in that, The method for preparing the anhydrous mixture containing elemental sulfur and metallic lithium includes the following steps: under an inert atmosphere, elemental sulfur and metallic lithium are added to an aprotic organic amine solvent with nitrogen coordinating atoms to form a mixture.
7. The method for preparing high-purity lithium sulfide based on organic amine solvent as described in claim 1, characterized in that, The reaction temperature is 30-80°C, for example 32°C, 35°C, 40°C, 45°C, 48°C, 50°C or 55°C, preferably 35-60°C; And / or, the reaction time is 0.5-4 h, preferably 1-3 h, for example 1 h, 1.5 h or 2 h; And / or, during the reaction in the mixed state, the mixing method is stirring or ultrasound; the stirring speed is preferably 200-800 rpm, more preferably 300-600 rpm, for example 350 rpm, 400 rpm, 450 rpm or 500 rpm.
8. The method for preparing high-purity lithium sulfide based on organic amine solvent as described in claim 1, characterized in that, The water bath temperature during rotary evaporation is 40-60°C, for example, 45°C, 48°C, 50°C or 55°C; And / or, the vacuum level during the rotary evaporation is -0.09 MPa to -0.1 MPa.
9. The method for preparing high-purity lithium sulfide based on organic amine solvent as described in claim 1, characterized in that, The solvent used for washing is a non-polar organic solvent that is sensitive to water and oxygen, preferably one or more of anhydrous n-hexane, anhydrous toluene, and anhydrous diethyl ether.
10. The method for preparing high-purity lithium sulfide based on organic amine solvent as described in claim 1, characterized in that, The drying temperature is 80-120°C, for example 85°C, 90°C, 100°C or 110°C; And / or, the drying time is 6-12 hours, for example 7 hours, 8 hours or 10 hours; And / or, the vacuum level during the drying process is less than -0.095 MPa.