Method for producing lithium sulfide based on ammonia gas purging lithium chloride double decomposition reaction
By introducing ammonia gas into the metathesis reaction of lithium chloride and ammonium sulfide, the hydrolysis problem of ammonium sulfide was solved by utilizing chemical equilibrium inhibition and physical gas stripping, thus achieving efficient production of high-purity lithium sulfide and improving the reaction rate and safety.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-04
- Publication Date
- 2026-03-31
AI Technical Summary
In existing technologies, the risk of hydrolysis of ammonium sulfide leads to low reaction temperature, slow reaction rate, long production cycle, and difficulty in controlling stoichiometry, which affects product purity.
The lithium chloride metathesis reaction was purged with ammonia gas. By continuously introducing ammonia gas into the reaction system, the hydrolysis reaction of ammonium sulfide was suppressed by chemical equilibrium inhibition and physical gas stripping, and the reaction was carried out at a higher temperature.
This improved the reaction rate, shortened the production cycle, increased production efficiency, and yielded high-purity lithium sulfide products, ensuring reaction safety and product purity.
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium sulfide production technology, specifically a method for producing lithium sulfide based on the metathesis reaction of lithium chloride purged with ammonia. Background Technology
[0002] Lithium sulfide, as a key precursor material for lithium-ion conductors, plays a central role in the development of sulfide solid electrolytes and the construction of all-solid-state lithium battery technology. Liquid-phase chemical synthesis, particularly the metathesis reaction of lithium chloride and ammonium sulfide, is a major technical route for preparing lithium sulfide powder. This route, with its relatively mild reaction conditions, high reaction conversion rate, and low equipment requirements, has great potential for industrial production.
[0003] Among the numerous lithium sulfide synthesis routes, the metathesis reaction using lithium chloride (LiCl) and ammonium sulfide ((NH4)2S) in an organic solvent is a wet chemical method with potential for industrial application. This method has the initial advantages of relatively readily available raw materials and mild reaction conditions. Therefore, existing techniques typically control the reaction temperature within a relatively low range, such as 20-40°C. After the reaction, the product is a solid mixture of lithium sulfide and the byproduct ammonium chloride, which is usually purified by solvent washing or heat treatment.
[0004] However, existing production technologies for ammonium sulfide suffer from inherent thermal instability. In the presence of trace amounts of moisture in the reaction system, it is prone to hydrolysis, releasing highly toxic and corrosive hydrogen sulfide gas. To mitigate this risk, the process is forced to operate at low temperatures, resulting in extremely slow kinetics of the main reaction, lengthy production cycles, and low unit yield. Furthermore, under low-temperature conditions, hydrolysis is difficult to completely suppress, making precise control of the stoichiometry of the reaction environment challenging and easily generating impurities such as lithium hydrosulfide, ultimately compromising the phase purity of the product. Therefore, this invention provides a method for producing lithium sulfide based on an ammonia-purged lithium chloride metathesis reaction, addressing the shortcomings of existing technologies. Summary of the Invention
[0005] To address the shortcomings of existing technologies, this invention provides a method for producing lithium sulfide based on the lithium chloride metathesis reaction purged with ammonia, which solves the technical defects of low reaction temperature and slow reaction rate caused by the risk of ammonium sulfide hydrolysis in existing technologies.
[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for producing lithium sulfide based on the lithium chloride metathesis reaction purged with ammonia, comprising the following steps: S1. Dissolve lithium chloride in an N-methyl-2-pyrrolidone solvent to form a liquid-phase reaction medium; S2. Add ammonium sulfide to the liquid reaction medium to initiate a metathesis reaction between lithium chloride and ammonium sulfide to generate insoluble lithium sulfide solid. Continuously pass a purge gas containing ammonia to remove hydrogen sulfide gas generated by the side reaction, thereby obtaining a lithium sulfide suspension composed of the insoluble lithium sulfide solid dispersed in the liquid phase after the reaction. S3. Perform solid-liquid separation on the lithium sulfide suspension to separate the lithium sulfide solid from the liquid phase after the reaction, and obtain a crude solid product containing lithium sulfide.
[0007] By adopting the above technical solution, and utilizing a purge gas containing ammonia, the hydrolysis side reaction of ammonium sulfide is synergistically suppressed in the metathesis reaction of lithium chloride and ammonium sulfide. This is specifically reflected in the following two aspects: Chemical equilibrium inhibition: Ammonium sulfide undergoes hydrolysis when it encounters trace amounts of water in aprotic polar solvents (such as N-methyl-2-pyrrolidone). This invention continuously introduces ammonia gas into the reaction system, increasing the ammonia concentration in the reactor headspace and liquid phase. According to the principle of chemical equilibrium shift (Le Chatelier's principle), this will shift the above hydrolysis equilibrium towards the reverse reaction direction, inhibiting the hydrolysis of ammonium sulfide from the root of chemical kinetics, thereby reducing the generation of toxic and harmful hydrogen sulfide gas.
[0008] Physical scavenging and gas lift: The continuously introduced purge gas physically lifts the reaction system. Even if a very small amount of hydrogen sulfide gas is generated due to hydrolysis, it will be immediately carried away from the reaction system by the continuously flowing gas, preventing its accumulation in the reactor.
[0009] Through the synergistic effect of the aforementioned chemical inhibition and physical scavenging, the technical challenge of ammonium sulfide's easy hydrolysis at high temperatures has been solved, breaking the limitation of existing processes that require the reaction to be carried out in a low-temperature range (such as 20-40℃). This allows the entire metathesis reaction to proceed safely at higher temperatures, thereby increasing the reaction rate of the main reaction, shortening the production cycle, and improving production efficiency.
[0010] Preferably, in step S1, the initial water content of the N-methyl-2-pyrrolidone solvent in the liquid reaction medium is controlled to be below 50 ppm.
[0011] By adopting this technical solution, the concentration of water participating in the hydrolysis reaction is further reduced, forming a double guarantee with ammonia purging, which maximizes the suppression of side reactions and provides a foundation for the production of high-purity products.
[0012] Preferably, in step S2, the reaction temperature of the metathesis reaction is set to 40-80°C.
[0013] By adopting this technical solution, this temperature range is an optimized choice that balances reaction rate and process stability. Compared with low-temperature processes, the reaction kinetic advantages of this temperature range are fully demonstrated. At this temperature, N-methyl-2-pyrrolidone solvent has good stability, and side reactions remain at an extremely low level under the control of ammonia purging, thus achieving a balance between high efficiency and high quality.
[0014] Preferably, in step S2, the purging gas is a mixture of high-purity nitrogen and dry ammonia.
[0015] By adopting this technical solution, high-purity nitrogen, as a chemically stable inert gas, can provide the main physical purging power and ensure that the entire reaction system is in an oxygen-free atmosphere, thus avoiding the oxidation of products or raw materials.
[0016] Preferably, by providing a first post-processing path, the process further includes the following after step S3: The separated crude lithium sulfide solid product is mixed with an organic solvent to dissolve and remove soluble impurities adhering to its surface; the crude lithium sulfide solid product is then subjected to solid-liquid separation and vacuum drying to obtain pure lithium sulfide. The organic solvent may be anhydrous ethanol, and the vacuum drying may be carried out at a temperature of 100-200°C. By adopting the above post-processing scheme, the byproduct ammonium chloride and possibly excess lithium chloride have a certain solubility in organic solvents such as anhydrous ethanol, while the main product lithium sulfide is insoluble. Soluble impurities are effectively removed by washing, and the subsequent vacuum drying step is used to remove the washing solvent, thereby obtaining a high-purity lithium sulfide powder product.
[0017] Preferably, by providing a second parallel post-processing path, after step S3, the process further includes: calcining the separated crude lithium sulfide solid product at high temperature under inert gas protection; utilizing the difference in physical properties between the byproduct ammonium chloride and the crude lithium sulfide solid product at high temperature, removing ammonium chloride from the solid product by sublimation to generate a composite material of lithium sulfide and lithium chloride. The high-temperature calcination step may further include: continuously introducing inert gas into the calcination equipment before starting the heating program to fully replace the air in the calcination equipment; heating the crude lithium sulfide solid product from room temperature to a target calcination temperature of 400-500°C at a preset heating rate of 1-10°C / min; maintaining the temperature at the target calcination temperature for 1-3 hours; and cooling the product to room temperature under inert gas protection after the isothermal calcination is completed.
[0018] By employing the above post-treatment scheme, this step is used to prepare a lithium sulfide-lithium chloride composite material. The sublimation temperature of the byproduct ammonium chloride is approximately 338°C, while the main product lithium sulfide and excess lithium chloride remain stable within this temperature range and at higher temperatures of 400-500°C. Therefore, through a precisely controlled high-temperature calcination process, ammonium chloride can be completely removed in the gaseous phase, resulting in a pure binary composite material composed of lithium sulfide and lithium chloride.
[0019] Preferably, in step S2, when the target product is pure lithium sulfide, the molar ratio of lithium chloride to ammonium sulfide can be set to 1.9-2.2:1.
[0020] By adopting this technical solution, the molar ratio is close to the stoichiometric ratio of 2:1, which can ensure a high conversion rate of reactants, while avoiding a large amount of residue of any reactant and reducing the burden on subsequent purification steps.
[0021] Preferably, in step S2, the purging gas is a mixture of inert gas and ammonia, and the volume flow ratio of the inert gas to the ammonia is 2-4:1.
[0022] By adopting this technical solution, the volumetric flow rate ratio is within the optimized range for achieving the synergistic effect of chemical inhibition and physical removal of ammonia. It ensures sufficient ammonia partial pressure in the system to effectively suppress hydrolysis equilibrium, while guaranteeing that the total gas flow rate is sufficient to rapidly remove trace amounts of byproduct gas, thus achieving the best balance between technical effectiveness and economic cost.
[0023] This invention provides a method for producing lithium sulfide based on an ammonia-purged lithium chloride metathesis reaction. It has the following beneficial effects: 1. This invention, by continuously introducing a purge gas containing ammonia into the reaction system during the metathesis reaction, effectively suppresses the hydrolysis side reaction of ammonium sulfide at higher temperatures through the dual effects of chemical equilibrium inhibition and physical stripping. This reduces the generation and accumulation of toxic and harmful hydrogen sulfide gas, improves the safety of the production process, and avoids product contamination caused by hydrolysis, thus ensuring the acquisition of high-purity final products.
[0024] 2. The ammonia purging process of this invention successfully solves the problem of ammonium sulfide hydrolysis and enables the metathesis reaction to proceed stably in a higher temperature range of 60-80℃. This breaks through the limitation of existing technologies that must be carried out in a low-temperature range due to safety risks. According to the principle of reaction kinetics, the increase in temperature greatly increases the reaction rate, thereby shortening the production cycle and improving the output per unit time and production efficiency.
[0025] 3. The present invention provides two clear and efficient post-processing paths, demonstrating the flexibility of the process and the diversity of products. High-purity pure lithium sulfide can be obtained by washing with organic solvents; by a specific high-temperature calcination process, the byproduct ammonium chloride can be effectively sublimated and removed to obtain a lithium sulfide-lithium chloride composite material with uniform composition. This allows the present invention to prepare two different forms of high-end sulfide products with controllable quality according to the different needs of downstream applications. Detailed Implementation
[0026] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.
[0027] N-Methyl-2-pyrrolidone (NMP), CAS No.: 872-50-4, has the chemical structural formula C5H9NO. It is a cyclic amide compound and requires deep dehydration treatment before use. See the preparation example for details. Lithium chloride (LiCl), CAS No.: 7447-41-8; Ammonium sulfide ((NH4)2S), CAS No.: 12135-76-1; Anhydrous methanol (CH3OH), CAS No.: 67-56-1; Anhydrous ethanol (C2H5OH), CAS No.: 64-17-5.
[0028] Preparation example: 1000 mL of analytical grade NMP (initial water content approximately 50 ppm) was placed in a 2000 mL three-necked flask, and 100 parts by weight of 4A molecular sieve activated at 350 °C for 8 hours were added. The mixture was then sealed and stirred at room temperature (25 °C) for 24 hours under a nitrogen atmosphere (flow rate 50 mL / min). After stirring, the NMP was transferred to a dry glass storage tank under positive nitrogen pressure using a double-row tube technique. The final water content of the NMP was measured using a Karl Fischer moisture analyzer, and the water content was less than 30 ppm.
[0029] Example 1-Example 2.
[0030] Example 1: This embodiment provides a method for producing lithium sulfide based on the lithium chloride metathesis reaction purged with ammonia gas. The raw material components used, by mass parts, include: Lithium chloride: 12.45 parts; Ammonium sulfide: 10 parts; N-Methyl-2-pyrrolidone (NMP): 720.3 parts; O-Anhydrous Ethanol: 331 parts.
[0031] The specific preparation steps are as follows: 720.3 parts of NMP, which had been deeply dehydrated as in Preparation Example 1, were added to a 1000 mL jacketed glass reactor. Start mechanical stirring (300 rpm), add 12.45 parts of dried lithium chloride, set the jacket temperature to 60°C, and stir until the lithium chloride is completely dissolved; Using a mass flow controller, high-purity nitrogen gas was introduced at a flow rate of 150 mL / min and dry ammonia gas at a flow rate of 50 mL / min. Under continuous stirring and gas purging conditions, 10 parts of ammonium sulfide powder were slowly and in batches added to the NMP solution of lithium chloride within 30 minutes. After the feed is added, the mixture is continuously stirred and purged with gas at 60°C for 4 hours. After the reaction is complete, heating and gas introduction are stopped. Under nitrogen protection, the reaction mixture is subjected to solid-liquid separation to obtain crude lithium sulfide solid. The solid was transferred to a beaker, and 110.3 parts of anhydrous ethanol were added for washing. After stirring for 15 minutes, solid-liquid separation was performed again. This washing step was repeated three times. The washed pure lithium sulfide was placed in a vacuum drying oven and dried under vacuum at 160°C for 6 hours to obtain white powdered lithium sulfide. Example
[0032] This embodiment provides a method for producing lithium sulfide based on the lithium chloride metathesis reaction purged with ammonia gas. The raw material components used, by mass parts, include: Lithium chloride: 18.65 parts; Ammonium sulfide: 10 parts; N-Methyl-2-pyrrolidone (NMP): 756.2 parts.
[0033] The specific preparation steps are as follows: 756.2 parts of NMP, which had been deeply dehydrated as in Preparation Example 1, were added to a 1000 mL jacketed glass reactor. Start mechanical stirring (300 rpm) and add 18.65 parts of dried lithium chloride. Set the jacket temperature to 70°C and stir until the lithium chloride is completely dissolved. High-purity nitrogen gas was introduced at a flow rate of 150 mL / min and dry ammonia gas at a flow rate of 50 mL / min using a mass flow controller. Under continuous stirring and gas purging conditions, 10 parts of ammonium sulfide powder were slowly and batch-wise added to the lithium chloride NMP solution over 30 minutes. After the feed is added, the mixture is continuously stirred and purged with gas at 70°C for 3 hours. After the reaction is complete, heating and gas introduction are stopped. Under nitrogen protection, the reaction mixture is subjected to solid-liquid separation to obtain crude lithium sulfide solid containing ammonium chloride and excess lithium chloride. The obtained crude lithium sulfide solid was spread evenly in a quartz boat and placed in a tube furnace. High-purity nitrogen gas was introduced into the tube furnace at a flow rate of 500 mL / min for 30 minutes. Then, the temperature was increased from room temperature to 450°C at a rate of 5°C / min, and calcined at 450°C for 2 hours. After calcination, the mixture was naturally cooled to room temperature under a nitrogen atmosphere to obtain a lithium sulfide composite material containing a specific proportion of lithium chloride.
[0034] Comparative Examples 1-5.
[0035] Comparative Example 1: Compared with Example 1, the difference is that dry ammonia gas is not introduced during the reaction process, and only high-purity nitrogen gas is introduced at a flow rate of 200 mL / min, while the rest are the same.
[0036] Comparative Example 2: Compared with Example 1, the difference is that the reaction temperature is set to 30°C and the reaction time is extended to 6 hours, while the rest are the same.
[0037] Comparative Example 3: Compared with Example 1, the difference is that the reaction temperature is set to 30°C, the reaction time is extended to 6 hours, and dry ammonia gas is not introduced during the reaction process; only high-purity nitrogen gas is introduced at a flow rate of 200 mL / min. All other aspects are the same.
[0038] Comparative Example 4: Compared with Example 2, the difference is that dry ammonia gas is not introduced during the reaction process, but high-purity nitrogen gas is introduced at a flow rate of 200 mL / min. The rest of the steps are the same as in Example 2.
[0039] Comparative Example 5: Compared with Example 1, the difference is that the crude lithium sulfide solid containing ammonium chloride and excess lithium chloride obtained after the reaction was not subjected to high-temperature calcination at 450°C, but was directly vacuum dried at 160°C for 6 hours, while the rest were the same.
[0040] Test Case 1-Test Case 3.
[0041] Test Example 1: Experimental objective: This test aims to evaluate the decisive role of each process in suppressing the generation of hydrogen sulfide (H2S) gas due to the hydrolysis of ammonium sulfide during the reaction of lithium chloride and ammonium sulfide in NMP solvent.
[0042] Experimental steps: The inlet of the calibrated high-precision electrochemical hydrogen sulfide gas sensor (range 0-100ppm, accuracy ±2ppm) was connected via a PTFE tubing to the tail gas outlet (after the condenser and before the tail gas absorption bottle) of the reaction vessel used in each example and comparative example. Before each test, the sensor was zero-calibrated using high-purity nitrogen.
[0043] Before the reaction begins (i.e. before adding ammonium sulfide to the reactor), the data recording system connected to the sensor is activated, and the sampling frequency is set to 1Hz.
[0044] From the moment ammonium sulfide is added until the set reaction time ends, the concentration change of hydrogen sulfide in the exhaust gas pipeline is continuously recorded.
[0045] After the reaction is complete, data recording is stopped. Two key indicators are extracted and recorded from the collected concentration data: the maximum peak hydrogen sulfide concentration during the reaction (peak H2S concentration), and the time-weighted average hydrogen sulfide concentration (average H2S concentration) throughout the entire reaction process.
[0046] Experimental data (see Table 1): Table 1: Monitoring data on hydrogen sulfide emission from tail gas under different preparation conditions Sample number Reaction temperature (°C) Ammonia purging (mL / min) <![CDATA[H2S concentration peak value (ppm)]]> <![CDATA[Average H2S concentration (ppm)]]> Sample number Example 1 60 50 3.2 0.9 Example 1 Example 2 70 50 3.9 1.1 Example 2 Comparative Example 1 60 0 78.4 30.2 Comparative Example 1 Comparative Example 2 30 50 1.9 0.5 Comparative Example 2 Comparative Example 4 70 0 85.1 35.6 Comparative Example 4 in conclusion: The data in Table 1 show that, compared with Comparative Example 1, at the same reaction temperature of 60°C, the elimination of ammonia purging caused the peak H2S concentration to increase sharply from 3.2 ppm to 78.4 ppm, and the average concentration also increased by tens of times. This directly proves that ammonia purging, through its physical stripping effect, can efficiently remove H2S molecules generated by trace hydrolysis in the reaction system, thereby preventing their accumulation in the headspace of the equipment and fundamentally eliminating the safety hazards of the process.
[0047] This conclusion was also verified in the process route of Example 2. Comparing Example 2 and Comparative Example 4, the absence of ammonia purging during the preparation of lithium sulfide-lithium chloride composite materials at 70°C also led to a significant increase in the peak H2S concentration from 3.9 ppm to 85.1 ppm. This indicates that ammonia purging plays a universal and necessary role in ensuring the safety of high-temperature reactions, regardless of whether the target product is pure lithium sulfide or its composite material.
[0048] Test Example 2: Experimental objective: This test aims to verify the effect of the ammonia purging process on the yield by comparing the reaction time and final yield at different reaction temperatures.
[0049] Experimental steps: Using ammonium sulfide ((NH4)2S) as the limited reactant in each embodiment and comparative example, the theoretical mass of lithium sulfide (Li2S) produced was calculated; The product powders that were finally prepared and dried in each example and comparative example were accurately weighed using an analytical balance with an accuracy of 0.1 mg in a glove box filled with high-purity argon gas, and their actual mass was recorded. Calculate and record the lithium sulfide yield for each sample, and record all the calculated yield data and corresponding preparation conditions in a data table.
[0050] Experimental data (see Table 2): Table 2: Comparison of lithium sulfide yield under different preparation conditions Sample number Reaction temperature ℃ reaction time h Ammonia purging mL / min Lithium sulfide yield (%) Example 1 60 4 50 94.1 Example 2 70 3 50 95.7 Comparative Example 1 60 4 0 86.2 Comparative Example 2 30 6 50 87.9 Comparative Example 4 70 3 0 85.5 in conclusion: Table 2 shows that Example 2, reacting at 30°C for 6 hours, yielded only 87.9%; while Example 1, by increasing the reaction temperature to 60°C and shortening the reaction time to 4 hours, achieved a yield of 94.1%. Example 2, reacting at 70°C, further shortened the reaction time to 3 hours, achieving a yield of 95.7%. This data directly demonstrates that the reaction rate in the 60-70°C temperature range is significantly higher than in the 30°C low-temperature range, thereby greatly shortening the production cycle and improving conversion efficiency.
[0051] Secondly, ammonia purging is crucial for achieving high yields at high temperatures. Comparative Example 1 and Comparative Example 1 (both at 60°C), omitting ammonia purging significantly reduced the yield from 94.1% to 86.2%. Similarly, Comparative Example 2 and Comparative Example 4 (both at 70°C) also saw a substantial decrease in yield from 95.7% to 85.5% due to the lack of ammonia purging. This indicates that at higher temperatures, without ammonia purging, the accumulated byproducts such as H2S in the reaction system interfere with the main reaction, leading to yield loss. Ammonia purging maintains the stability of the reaction environment, ensuring the efficient conduct of the main reaction.
[0052] Test Example 3: Experimental objective: This test aims to verify the key role of each process in obtaining high-purity lithium sulfide or high-quality lithium sulfide-lithium chloride composite materials by quantitatively analyzing the content of main components and key impurities in the final product.
[0053] Experimental steps: All the dried product powders to be tested were sampled and pretreated in a glove box filled with high-purity argon to prevent them from reacting with air or moisture.
[0054] Determination of the content of the main component (Li2S): Accurately weigh approximately 0.2g of sample and quickly dissolve it in 200mL of pre-deoxygenated deionized water; The above sample solution was subjected to potentiometric titration using an automatic potentiometric titrator with a 0.01 mol / L standard iodine solution as the titrant. Calculate the sulfide ion (S) content in the sample based on the amount of iodine solution consumed. 2- The content of lithium sulfide (Li2S) was calculated and converted into the mass percentage of lithium sulfide (Li2S) in the total sample.
[0055] Determination of impurity ion content: Accurately weigh approximately 0.1g of the sample, quickly dissolve it in 100mL of deoxygenated deionized water, and bring the volume up to a final volume. Take an appropriate amount of sample solution, filter it through a 0.22 μm filter membrane, and then inject it into an ion chromatography (IC) system; An anion analysis system equipped with an AS11-HC separation column and corresponding guard column was used to determine chloride ions (Cl-) in the sample by gradient elution with KOH eluent. - The concentration of ); A cation analysis system equipped with a CS12A separation column and corresponding guard column was used to determine the ammonium ion (NH4+) in the sample by isocratic elution with methanesulfonic acid eluent. + The concentration of ions is determined, and their mass percentage in the original sample is calculated based on the measured ion concentration.
[0056] Experimental data (see Table 3): Table 3: Analysis data on product purity and impurity content under different preparation conditions Sample number <![CDATA[Li2S content %]]> <![CDATA[Cl - Content (wt%) <![CDATA[NH4 + Content (wt%) Target product Example 1 99.2 0.05 0.01 <![CDATA[Pure Li2S]]> Example 2 65.8 33.1 <0.01 <![CDATA[Li2S-LiCl composite material]]> Comparative Example 1 96.1 0.14 0.09 <![CDATA[Pure Li2S]]> Comparative Example 2 99.0 0.06 0.02 <![CDATA[Pure Li2S]]> Comparative Example 4 63.5 34.2 <0.01 <![CDATA[Li2S-LiCl composite material]]> Comparative Example 5 64.1 30.5 2.58 <![CDATA[Li2S-LiCl-NH4Cl mixture]]> in conclusion: Table 3 shows that, compared to Comparative Example 1, both reacted at 60°C, but the removal of ammonia purging led to a significant decrease in Li₂S purity from 99.2% to 96.1%, while Cl… - and NH4 + The impurity content increased significantly. This indicates that at higher temperatures, without ammonia purging, accumulated byproducts in the system can interfere with the reaction or introduce impurities, thereby impairing product purity. The ammonia purging method of this invention effectively suppresses such side reactions by maintaining a stable reaction environment.
[0057] For the preparation of lithium sulfide-lithium chloride composite materials in Example 2, the purification steps of this invention are necessary. Comparative Example 2 and Comparative Example 5, Comparative Example 5, which did not undergo high-temperature calcination, had lower NH4 content. + The content was as high as 2.58%, indicating a large amount of residual ammonium chloride byproduct; while in Example 2, after calcination, the NH4 content was significantly lower. +The content was below the detection limit, proving that high-temperature calcination at 450℃ is a key and necessary purification method for effectively removing ammonium chloride and obtaining the target composite material.
[0058] Even in the preparation of composite materials, ammonia purging is equally important for ensuring the quality of the initial reaction. Comparing Example 2 and Comparative Example 4, although both underwent effective high-temperature calcination, the Li2S content of the final product in Comparative Example 4 (63.5%) was lower than that in Example 2 (65.8%) due to the lack of ammonia purging during the reaction stage. This indicates that impurities generated in the initial reaction stage affected the component ratio of the final product.
[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. Process for the production of lithium sulfide based on the metathesis reaction of lithium chloride purged with ammonia, characterized in that, The method comprises the following steps: S1, dissolving lithium chloride in an N-methyl-2-pyrrolidone solvent to form a liquid-phase reaction medium; S2, adding ammonium sulfide to the liquid-phase reaction medium to initiate a metathesis reaction between lithium chloride and ammonium sulfide to generate insoluble lithium sulfide solids, and continuously introducing a purge gas containing ammonia to remove hydrogen sulfide gas generated by a side reaction, to obtain a lithium sulfide suspension composed of the insoluble lithium sulfide solids dispersed in a post-reaction liquid phase; S3, performing solid-liquid separation on the lithium sulfide suspension to separate the lithium sulfide solids from the post-reaction liquid phase, to obtain a lithium sulfide-containing crude solid product.
2. The method for producing lithium sulfide based on the lithium chloride metathesis reaction with ammonia gas purging according to claim 1, characterized by, In step S1, the initial water content of the N-methyl-2-pyrrolidone solvent in the liquid-phase reaction medium is controlled to be less than 50 ppm.
3. The method for producing lithium sulfide based on the lithium chloride metathesis reaction with ammonia gas purging according to claim 2, characterized by, In step S2, the reaction temperature of the metathesis reaction is set to 40-80°C.
4. The method for producing lithium sulfide based on the lithium chloride metathesis reaction with ammonia gas purging according to claim 1, characterized by, In step S2, the purge gas is composed of high-purity nitrogen gas mixed with dry ammonia gas, to maintain an inert atmosphere of the system while removing the byproduct gas.
5. The method for producing lithium sulfide based on the lithium chloride metathesis reaction with ammonia gas purging according to claim 1, characterized by, In step S3, after the step of obtaining the lithium sulfide-containing crude solid product, further comprising: mixing the separated lithium sulfide-containing crude solid product with an organic solvent to dissolve and remove surface-attached soluble impurities; performing solid-liquid separation on the lithium sulfide-containing crude solid product and vacuum drying to obtain a pure lithium sulfide product.
6. The method for producing lithium sulfide based on the lithium chloride metathesis reaction with ammonia gas purging according to claim 5, characterized by, The organic solvent is anhydrous ethanol, and the vacuum drying is performed at a temperature of 100-200°C.
7. The method for producing lithium sulfide based on the lithium chloride metathesis reaction with ammonia gas purging according to claim 1, characterized by, In step S3, after the step of obtaining the lithium sulfide-containing crude solid product, further comprising: performing high-temperature calcination on the separated lithium sulfide-containing crude solid product under inert gas protection, using the difference in physical properties of the byproduct ammonium chloride and the lithium sulfide-containing crude solid product at high temperature to remove ammonium chloride from the solid product by sublimation, to generate a lithium sulfide and lithium chloride composite material.
8. The method for producing lithium sulfide based on the lithium chloride metathesis reaction with ammonia gas purging according to claim 7, characterized by, The high-temperature calcination step further comprises: Before starting the heating program, continuously introducing inert gas into the calcination equipment to fully replace the air in the calcination equipment; heating the lithium sulfide-containing crude solid product from room temperature to a calcination target temperature of 400-500°C at a preset heating rate of 1-10°C / min; at the calcination target temperature, maintaining a constant temperature for 1-3 hours, and after the constant-temperature calcination is completed, cooling the product to room temperature under inert gas protection.
9. The method for producing lithium sulfide based on the lithium chloride metathesis reaction with ammonia gas purging according to claim 1, characterized by, In step S2, the molar ratio of lithium chloride to ammonium sulfide is 1.9-2.2:
1.
10. The method for producing lithium sulfide based on the lithium chloride metathesis reaction with ammonia gas purging according to claim 1, characterized by, In step S2, the purge gas is a mixed gas of inert gas and ammonia gas, and the volume flow ratio of the inert gas to the ammonia gas is 2-4:1.