Process for preparing high-purity lithium sulfide by layer interface-induced strengthening

Abstract

The application provides a process for preparing high-purity lithium sulfide by layer interface induction strengthening, comprising the following steps: dissolving lithium chloride and sodium sulfide in N-methyl pyrrolidone and stirring to form a uniform slurry; pumping the obtained slurry into a fixed bed reactor provided with a layered module of a molybdenum disulfide catalyst, reacting to obtain a suspension; controlling the temperature of the suspension to crystallize, filtering and separating to obtain sodium chloride crystals; performing vacuum distillation on the filtrate to obtain lithium sulfide crude products; dissolving the lithium sulfide crude products in anhydrous ethanol, washing, suction filtering and drying to obtain lithium sulfide. The application integrates the fixed bed catalytic reaction and the programmed temperature reduction crystallization separation, and optimizes the process parameters, successfully solves the core pain points such as high energy consumption, poor safety, difficult separation and easy deactivation of the catalyst in the traditional method, and realizes the green closed loop of the whole process through the recycling of the solvent and the resource utilization of the by-products, thereby providing a reliable technical path for the industrial production of high-performance lithium sulfide materials.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a process for preparing high-purity lithium sulfide through layer-interface induced strengthening. Background Technology

[0002] Lithium-ion battery technology is evolving towards higher energy density and higher safety. Among these advancements, solid-state battery systems employing inorganic solid electrolytes (especially sulfide electrolytes) are considered an ideal solution to address key issues such as insufficient electrochemical / thermal stability and poor safety in traditional liquid lithium batteries. Among numerous solid-state electrolyte materials, sulfide electrolytes have become a focus of research and development in both academia and industry due to their extremely high ionic conductivity (comparable to liquid electrolytes), excellent mechanical ductility (facilitating the formation of dense interfaces), and good electrochemical stability.

[0003] Lithium sulfide, as an indispensable lithium source and sulfur source precursor for the synthesis of sulfide solid electrolytes, directly determines the performance and commercial feasibility of the final electrolyte and battery system due to its material purity, morphology, and cost. However, the widespread application of Li2S faces three core challenges: ① High raw material cost: The market price of high-purity Li2S is a key factor restricting the cost reduction of sulfide solid batteries. ② Environmental sensitivity of materials: Li2S is prone to hydrolysis in air (Li2S + 2H2O → 2LiOH + H2S↑), releasing highly toxic hydrogen sulfide gas. Therefore, all synthesis, storage, and post-processing processes must be carried out in a strictly controlled inert atmosphere (such as an argon glove box), significantly increasing the complexity and cost of the process. ③ Balancing nanoscale and purity control: To improve the interfacial contact and ion transport efficiency of solid batteries, nanoscale Li2S materials are usually required. However, nanoscale formation further intensifies its surface activity, placing extremely high demands on purity control, oxidation prevention, and dispersion stability.

[0004] Methods for preparing Li₂S in the laboratory and industry can be mainly divided into three categories: ball milling, carbothermal reduction, and inter-compound reaction. Ball milling includes top-down physical pulverization and bottom-up mechanochemical synthesis methods. This type of method has a simple process route, low equipment requirements, and potential for large-scale production. Carbothermal reduction typically uses lithium sulfate or similar materials as a lithium source, which reacts with a carbon source at high temperatures. This method is mature and can directly prepare Li₂S-carbon composite materials, suitable for specific electrode systems. Inter-compound reaction utilizes lithium-containing compounds (such as LiH, lithium carbonate) to react with active sulfur sources (such as hydrogen sulfide) in the gas or liquid phase to generate Li₂S. This type of method has diverse reaction pathways, and the product morphology can be controlled to some extent through precursor design.

[0005] In summary, lithium sulfide, as a key foundational material driving breakthroughs in next-generation solid-state battery technology, presents both high-performance potential and stringent preparation challenges. Future technological development will inevitably focus on developing new green synthesis routes that are low-cost, low-energy, high-purity, and capable of precise nanoscale control. Overcoming the limitations of existing methods such as ball milling, carbothermal reduction, and inter-compound reaction methods is crucial for accelerating the commercialization of sulfide solid-state batteries. Summary of the Invention

[0006] To address the aforementioned issues, this invention aims to provide a process for preparing high-purity lithium sulfide through layer-interface induction enhancement. This process is a new large-scale synthesis technology that can achieve low cost, high purity, good morphology control, and is safe and environmentally friendly.

[0007] In a first aspect, the present invention provides a process for preparing high-purity lithium sulfide through layer interface induced strengthening, comprising:

[0008] Step 1): Dissolve lithium chloride and sodium sulfide in N-methylpyrrolidone and stir to form a homogeneous slurry;

[0009] Step 2): The slurry obtained in Step 1) is pumped into a fixed-bed reactor containing a molybdenum disulfide catalyst module, and reacted to obtain a suspension;

[0010] Step 3): The suspension is crystallized under controlled temperature, filtered and separated to obtain sodium chloride crystals; the filtrate is then distilled under reduced pressure to obtain crude lithium sulfide.

[0011] Step 4): Dissolve the crude lithium sulfide in anhydrous ethanol, wash, filter and dry to obtain lithium sulfide.

[0012] In some embodiments, the mass ratio of lithium chloride to sodium sulfide is 1:(1~2). Preferably, it is 1:1, 1:1.5, 1:2, or any two of the above values ​​forming a range.

[0013] In some embodiments, the volume-to-mass ratio of N-methylpyrrolidone to lithium chloride is 30:(1~2). Preferably, it is 30:1, 30:1.5, 30:2, or any two of the above values ​​forming a range.

[0014] In some embodiments, in step 1), the stirring speed is 500 rpm to 1500 rpm, and the stirring time is 20 minutes to 40 minutes. Preferably, the stirring speed is any one of 500 rpm, 1000 rpm, and 1500 rpm, or any two of the above values, and the stirring time is any one of 20 minutes, 30 minutes, and 40 minutes, or any two of the above values. In some embodiments, the reaction temperature in step 1) is 15℃ to 35℃, preferably any one of 15℃, 20℃, 25℃, 30℃, and 35℃, or any two of the above values. Sufficient mechanical stirring ensures high dispersion of the raw material particles, increasing the contact area for subsequent catalytic reactions.

[0015] In some embodiments, the slurry is prepared at a concentration of 1 hour. -1 ~5h -1 The air velocity pumping is preferably 1 hour. -1 2h -1 3h -1 4h -1 5h -1 And any two of the above values ​​constitute any one of the ranges. The choice of space velocity requires a trade-off between reaction conversion rate and equipment processing capacity. Fixed-bed reactors provide a stable reaction environment, which is beneficial for mass transfer and reaction control. The slurry undergoes a metathesis reaction as it passes through the catalyst bed, where lithium chloride and sodium sulfide react to produce lithium sulfide and sodium chloride.

[0016] In some embodiments, the molybdenum disulfide is at least one of molybdenum disulfide nanosheets and molybdenum sulfide / titanium carbide composite material.

[0017] In some embodiments, the molybdenum disulfide nanosheets are prepared by dissolving sodium molybdate and thiourea in deionized water to form a homogeneous solution, reacting it at 150°C to 250°C for 24 to 36 hours, and then cooling, centrifuging, washing with water, and drying.

[0018] In some embodiments, the preparation process of the molybdenum disulfide catalyst module is as follows: molybdenum disulfide nanosheets are mixed with a binder, and anhydrous ethanol is added to form a slurry. This slurry is then coated onto a cordierite honeycomb ceramic support and dried to form the molybdenum disulfide catalyst module. The molybdenum disulfide catalyst provides highly efficient catalytic active centers, significantly reducing the reaction activation energy and enabling the reaction to proceed efficiently at a mild temperature.

[0019] In some embodiments, the binder is one of tetraethyl orthosilicate, hydroxyethyl methacrylate, and methyl acrylate. The amount of binder used is 1% to 10% of the weight of the molybdenum disulfide nanosheets, preferably 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any two of the above values. Catalysts prepared using tetraethyl orthosilicate as a binder have better flowability and stability, reducing the number of coating applications and detachment rate while ensuring the coating amount, resulting in a more robust coating. The amount of anhydrous ethanol used is 10% to 20% of the weight of the molybdenum disulfide nanosheets, preferably 10%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, or any two of the above values.

[0020] In some embodiments, in step 2), the reaction is carried out at atmospheric pressure and at a temperature of 50°C to 70°C. Preferably, the temperature is 50°C, 60°C, and 70°C, or any two of these values ​​forming a range.

[0021] In some embodiments, the temperature-controlled crystallization refers to transferring the suspension to a crystallization vessel and cooling it to 5°C at a rate of 1°C / min to 5°C / min, preferably at a rate of 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, or any two of the above values ​​forming a range. If necessary, a small amount of sodium chloride seed crystals can be added to induce crystallization. The combination of programmed cooling and seed crystal addition is the core of achieving efficient separation by utilizing the difference in solubility of Li₂S and NaCl in NMP with temperature (NaCl solubility decreases significantly with decreasing temperature, while Li₂S solubility changes relatively slowly). Slow cooling and controlled nucleation rate help obtain large, easily filterable NaCl crystals, reducing entrainment of Li₂S.

[0022] In some embodiments, the temperature of the vacuum distillation is 70℃~90℃ and the vacuum degree is -0.095MPa, preferably any one of the ranges of 70℃, 80℃, 90℃ and any two of the above values.

[0023] In some embodiments, in step 4), the drying temperature is 70°C to 90°C, preferably any one of any two values ​​from 70°C, 80°C, 90°C, and above, and the drying time is 5 hours to 9 hours, preferably any one of any two values ​​from 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, and above.

[0024] Vacuum distillation enables efficient recovery of NMP solvent, significantly reducing production costs and environmental impact. Choosing ethanol as the washing solvent is crucial; it selectively dissolves and removes LiCl impurities while exhibiting extremely low solubility for Li2S products, thus significantly improving product purity while ensuring high recovery rates. Vacuum drying thoroughly removes residual volatile solvents.

[0025] Furthermore, after the reaction has proceeded continuously for 48 hours (or when the Li2S content in the reactor outlet material significantly decreases, indicating catalyst activity degradation), the fixed-bed catalyst module is flushed with a sodium sulfide ethanol solution in the opposite direction to the normal reaction flow for 2 hours, followed by flushing with anhydrous ethanol and drying with nitrogen to complete catalyst regeneration. Regular reverse cleaning effectively loosens the bed and removes physical blockages. The ethanol regeneration solution containing sodium sulfide chemically removes specific poisons. This regeneration process is simple and effective, significantly extending catalyst lifespan and ensuring continuous and stable operation of the entire system.

[0026] In some embodiments, the concentration of the sodium sulfide ethanol solution is 0.05 mol / L to 0.2 mol / L.

[0027] Beneficial effects

[0028] (1) The present invention uses a slurry of lithium chloride and sodium sulfide to carry out a liquid-phase catalytic reaction with molybdenum disulfide in a fixed bed. The reaction temperature is much lower than that of the high-temperature solid-phase method, only about 60°C. The energy consumption is low, the equipment requirements are relatively simple, the operation is safe, the reaction conditions are mild and safe, the use of highly toxic hydrogen sulfide gas is avoided, the raw materials are readily available, and the environment is friendly.

[0029] (2) This invention uses a molybdenum disulfide catalyst module installed in a fixed-bed reactor, which significantly accelerates the metathesis reaction rate and improves the feed conversion rate. The fixed-bed continuous operation mode is beneficial for process control and large-scale scale-up.

[0030] (3) The present invention uses programmed cooling crystallization technology to selectively precipitate by-product sodium chloride. By utilizing the difference in solubility of lithium sulfide and sodium chloride in NMP solvent with temperature changes, the by-products are separated efficiently. The present invention obtains sodium chloride crystals with uniform particle size and easy filtration by optimizing the cooling rate and the final temperature, and by adding seed crystals, thereby ensuring the high purity of the subsequent lithium sulfide solution.

[0031] (4) After removing most of the sodium chloride by crystallization separation, the present invention combines the solvent recovery by vacuum distillation and the washing of crude lithium sulfide with a specific solvent (such as ethanol) to effectively remove trace amounts of residual lithium chloride and other impurities. The final product purity can reach 99.9% and the impurity content is extremely low.

[0032] (5) The NMP solvent recovery rate of this invention is as high as 95% or more, which significantly reduces solvent consumption and waste liquid treatment costs. The by-product sodium chloride crystals also have high purity (>98%), which can be sold or reused as industrial raw materials, realizing comprehensive utilization of resources and conforming to the principles of green chemistry.

[0033] (6) The present invention has designed a special catalyst regeneration step, which can effectively restore the activity of catalysts that have been deactivated by salt deposition or slight poisoning, restoring their activity to more than 96% of their initial activity, ensuring that the reactor can operate stably for a long period of time, and reducing the frequency and cost of catalyst replacement.

[0034] (7) The preparation process of this invention is continuous and can be produced continuously. By organically combining steps such as homogenization, reaction, crystallization, separation, purification, solvent recovery and catalyst regeneration, a complete process system that can be operated continuously or semi-continuously is formed, providing a feasible technical solution for the industrial production of lithium sulfide.

[0035] (8) This invention integrates fixed-bed catalytic reaction with temperature-programmed crystallization separation and optimizes process parameters to form a highly efficient, clean, stable, and economical continuous preparation method for lithium sulfide. This method not only successfully solves the core problems of traditional methods, such as high energy consumption, poor safety, difficult separation, and easy catalyst deactivation, but also achieves a green closed loop for the entire process through solvent recycling and by-product resource utilization, providing a reliable technical path for the industrial production of high-performance lithium sulfide materials. Attached Figure Description

[0036] Figure 1 The image shows the XRD pattern of lithium sulfide prepared in Example 1.

[0037] Figure 2 The image shows a SEM image of the lithium sulfide product prepared in Example 1.

[0038] Figure 3 The image shows the SEM morphology of the molybdenum disulfide catalyst before use in Example 1.

[0039] Figure 4 The image shows the SEM morphology of the molybdenum disulfide catalyst regenerated after 10 cycles in Example 1.

[0040] Terminology Explanation

[0041] Certain embodiments of the invention will now be described in detail, examples of which are illustrated by the accompanying structural and chemical formulas. The invention is intended to cover all alternatives, modifications, and equivalents, all of which are included within the scope of the invention as defined in the claims. Those skilled in the art will recognize that many similar or equivalent methods and materials can be used to practice the invention. The invention is by no means limited to the methods and materials described herein. In the event that one or more of the incorporated documents, patents, and similar materials differ from or contradict this application (including, but not limited to, defined terminology, application of terminology, described techniques, etc.), this application shall prevail.

[0042] It should be further appreciated that certain features of the invention, for clarity, have been described in multiple independent embodiments, but may also be provided in combination in a single embodiment. Conversely, various features of the invention, for brevity, have been described in a single embodiment, but may also be provided individually or in any suitable sub-combination.

[0043] Unless otherwise stated, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. All patents and publications related to this invention are incorporated herein by reference in their entirety.

[0044] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0045] In the following content, all numbers disclosed herein, whether or not they use words such as "approximately" or "about," are approximate values. The value of each number may vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20%. Whenever a number with a value of N is disclosed, any numbers with values ​​of N+ / -1%, N+ / -2%, N+ / -3%, N+ / -5%, N+ / -7%, N+ / -8%, N+ / -10%, N+ / -15%, or N+ / -20% will be explicitly disclosed, where "+ / -" indicates addition or subtraction. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0047] All reagents used in this invention can be purchased commercially or prepared by the methods described in this invention.

[0048] Anhydrous lithium chloride with a purity of ≥99.9% is pretreated by vacuum drying at 120℃ to completely remove moisture and avoid its adverse effects on subsequent reactions and catalysts.

[0049] Anhydrous sodium sulfide, with a purity of ≥99.9%, also requires strict drying treatment.

[0050] N-methylpyrrolidone (NMP) is deeply dried using 4A molecular sieves to ensure a moisture content of less than 50 ppm, which is a key prerequisite for maintaining high catalyst activity and reaction selectivity.

[0051] Preparation of molybdenum disulfide catalyst module

[0052] 1) Mix 67.5 mg sodium molybdate and 135.0 mg thiourea (Mo / S molar ratio of 1:6.5) with 30 mL of deionized water to obtain mixture A;

[0053] 2) After mixing mixture A into a transparent solution, place it in a 40mL hydrothermal reactor and heat it at 200℃ for 24 hours. After the reaction is completed, allow it to cool naturally to room temperature. After centrifugation, washing with water and ethanol several times, the product is vacuum dried at 60℃ for 12 hours to obtain molybdenum disulfide nanosheet powder.

[0054] 3) Molybdenum disulfide nanosheet powder was mixed with tetraethyl orthosilicate (mass ratio 10:1), and then diluted with anhydrous ethanol equal to 20% of the weight of the molybdenum disulfide nanosheets to form a slurry. This slurry was then coated onto a cordierite honeycomb ceramic carrier to prepare a molybdenum disulfide catalyst module. The molybdenum disulfide nanosheets (specific surface area 800 m²) 2 (g), whose unique electronic structure and surface properties provide an efficient catalytic pathway for metathesis reactions.

[0055] Example 1

[0056] Step 1: Homogenization of Raw Materials: In a nitrogen-protected glove box, weigh 10.0 g of anhydrous lithium chloride and 15.6 g of anhydrous sodium sulfide into a 500 mL three-necked flask, and add 300 mL of N-methylpyrrolidone dried with molecular sieves as a solvent. Stir magnetically at 500 rpm for 30 minutes at room temperature to fully disperse the solids and form a homogeneous slurry.

[0057] Step 2: Catalytic reaction: The above slurry is subjected to a 2-hour reaction. -1 The catalyst was pumped at high air velocity into a fixed-bed reactor (2 cm in diameter, 20 cm in length) containing the aforementioned molybdenum disulfide catalyst module. The reaction was carried out at atmospheric pressure and 60 °C, yielding an effluent. The effluent was a suspension containing lithium sulfide, sodium chloride, and unreacted raw materials.

[0058] Step 3: Crystallization Separation: The reaction effluent was transferred to a crystallization vessel and cooled at a programmed rate of 1℃ / min at 100 rpm. When the temperature dropped to approximately 15℃, 0.1 g of pre-prepared pure NaCl seed crystals were added to induce crystallization. After reaching 5℃, the mixture was kept at this temperature for 2 hours to ensure complete crystal growth and uniform particle size. Subsequently, the suspension was transferred to a pre-cooled Buchner funnel for filtration to separate the NaCl crystals. The filtrate was a Li₂S-rich NMP solution.

[0059] Step 4: Solvent Recovery and Product Purification: The filtrate was subjected to vacuum distillation (80℃, -0.095MPa) to recover the NMP solvent. The distillation residue was crude Li₂S. The crude Li₂S was washed three times with 50mL of anhydrous ethanol, stirring for 15 minutes each time, to dissolve and remove trace amounts of LiCl impurities. After washing, the product was filtered, and the solid was dried under vacuum at 80℃ for 6 hours to obtain a white powdery high-purity lithium sulfide product.

[0060] Step 5: Catalyst regeneration: After the reactor has been running continuously for 48 hours, the catalyst bed is backwashed with a 0.1 mol / L sodium sulfide ethanol solution at a low flow rate for 2 hours, then rinsed with pure ethanol for 1 hour, and dried with nitrogen for 2 hours to complete catalyst regeneration.

[0061] Results: Chemical analysis showed that the lithium sulfide product obtained in this example had a purity of over 99.9%, with a LiCl residue of less than 0.1%. The by-product NaCl crystals had a purity exceeding 98% and could be used as an industrial raw material. The NMP solvent recovery rate was greater than 95%. After regeneration, the catalyst activity was restored to over 96% of its initial activity.

[0062] like Figure 1 The XRD analysis diagram of the lithium sulfide product prepared in Example 1 is shown. The XRD test of the lithium sulfide product obtained in Example 1 shows that its diffraction pattern matches well with the Li2S standard card and there are no obvious impurity phase peaks, indicating that the product has good crystallinity and high purity.

[0063] like Figure 2 The SEM image of the lithium sulfide product prepared in Example 1 shows the morphology of the lithium sulfide powder obtained in Example 1, which is relatively uniform in shape.

[0064] like Figures 3-4 As shown, SEM morphology analysis of the catalyst before and after regeneration confirmed that after 10 regenerations, the catalyst surface still has a large number of interfacial layers, which can effectively provide catalytic reaction interfaces and have high catalytic activity.

[0065] Example 2

[0066] The difference from Example 1 is that the reaction temperature in step 2 is changed, while the rest is the same as in Example 1. Details are shown in Table 1 below:

[0067] Table 1. Effect of reaction temperature change on the product

[0068]

[0069] As shown in Table 1, reaction temperature has a significant impact on product purity and catalyst lifetime. At excessively low temperatures (25℃), the reaction rate is slow, conversion is incomplete, leading to decreased product purity and increased impurity content; however, the catalyst deactivation rate is relatively slow. At excessively high temperatures (80℃), a small number of side reactions or slight solvent decomposition may occur, and carbonization or sintering on the catalyst surface is accelerated, resulting in a shorter single-cycle operating time. 60℃ is the optimal temperature range, at which the reaction rate, product purity, and catalyst lifetime achieve the best balance.

[0070] Example 3

[0071] The difference from Example 1 is that the process of crystallization separation in step 3 is changed, while the rest is the same as in Example 1. See Table 2 below for details:

[0072] Table 2 Effect of Crystallization Condition Adjustment on Byproducts

[0073]

[0074] The cooling rate directly affects crystal nucleation and crystal growth. An excessively fast rate (>2℃ / min) easily leads to the formation of numerous fine crystals, which is detrimental to filtration. The cooling rate of 1℃ / min and the endpoint temperature of 5℃ selected in Example 1, combined with the addition of seed crystals, represent the preferred solution for achieving efficient separation and high-quality products.

[0075] Example 4

[0076] The difference from Example 1 is that, after 48 hours of operation in Example 1, no regeneration was performed, and the reaction continued. It was found that after 72 hours, the Li2S content in the reaction effluent had dropped to below 85% of the initial value, indicating a significant decrease in catalyst activity and necessitating catalyst regeneration.

[0077] Example 5

[0078] The catalyst was regenerated according to the process described in step 5 of Example 1. After regeneration, the reaction process was restarted, and the Li2S content in the initial reaction effluent was monitored. The results showed that the initial activity of the catalyst after regeneration was restored to 96% of the activity of the fresh catalyst. This indicates that the regeneration process designed in this invention can effectively restore catalyst activity and meet the requirements of long-term industrial operation.

[0079] Detection Example 1

[0080] 1) Sample pretreatment: Weigh about 0.05g of the sample prepared in Examples 1 and 2-3, add pure water, heat to remove hydrogen sulfide; add hydrochloric acid to adjust the pH, add hydrogen peroxide to oxidize the precipitate, and then make up to 25ml with pure water.

[0081] 2) Elements numbered 1-54 were detected using ICP-MS; elements numbered 55-63 were detected using ICP.

[0082] 3) Except for lithium (Li), which was diluted 400 times before detection, all other elements were not diluted.

[0083] The test results are shown in Table 3 below:

[0084] Table 3. Detection of elements in samples prepared in the examples

[0085]

[0086] Continued from Table 3

[0087]

[0088] Continued from Table 3

[0089]

[0090] As can be seen from Table 3, the purity of lithium sulfide obtained in Examples 1 and 2-3 all reached 99.9%, and the impurity content of each substance was extremely low.

[0091] The method of this invention has been described through preferred embodiments. Those skilled in the art will readily be able to modify or appropriately alter and combine the methods and applications described herein within the scope, spirit, and context of this invention to implement and apply the technology of this invention. Those skilled in the art can refer to the content herein to appropriately improve process parameters. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the scope of this invention.

Claims

1. A process for preparing high-purity lithium sulfide through interfacial induction and strengthening, characterized in that, include: Step 1): Dissolve lithium chloride and sodium sulfide in N-methylpyrrolidone and stir to form a homogeneous slurry; Step 2): The slurry obtained in Step 1) is pumped into a fixed-bed reactor containing a molybdenum disulfide catalyst module and reacted to obtain a suspension. The reaction is carried out at atmospheric pressure and 50°C to 70°C. Step 3): The suspension is crystallized under controlled temperature, filtered and separated to obtain sodium chloride crystals; the filtrate is then distilled under reduced pressure to obtain crude lithium sulfide. Step 4): Dissolve the crude lithium sulfide in anhydrous ethanol, wash, filter and dry to obtain lithium sulfide.

2. The process according to claim 1, characterized in that, The mass ratio of lithium chloride to sodium sulfide is 1:(1~2); the volume mass ratio of N-methylpyrrolidone to lithium chloride is 30:(1~2).

3. The process according to claim 1, characterized in that, Step 1), the stirring speed is 500 rpm to 1500 rpm, the stirring time is 20 minutes to 40 minutes, and the reaction temperature is 15℃ to 35℃.

4. The process according to claim 1, characterized in that, The slurry was prepared at 1 hour. -1 ~5h -1 The air velocity pumped in; The molybdenum disulfide is at least one of molybdenum disulfide nanosheets and molybdenum sulfide / titanium carbide composite materials.

5. The process according to claim 4, characterized in that, The molybdenum disulfide nanosheets were prepared by dissolving sodium molybdate and thiourea in deionized water to form a homogeneous solution, reacting it at 150℃~250℃ for 24 to 36 hours, and then cooling, centrifuging, washing with water and drying. The preparation process of the molybdenum disulfide catalyst module is as follows: molybdenum disulfide nanosheets are mixed with a binder and then anhydrous ethanol is added to form a slurry, which is then coated onto a cordierite honeycomb ceramic carrier and dried.

6. The process according to claim 5, characterized in that, The binder is one of tetraethyl orthosilicate, hydroxyethyl methacrylate, and methyl acrylate; the amount of binder used is 1% to 10% of the weight of molybdenum disulfide nanosheets.

7. The process according to claim 1, characterized in that, The temperature-controlled crystallization refers to transferring the suspension to a crystallization vessel and cooling it to 5°C at a rate of 1°C / min to 5°C / min; the vacuum distillation temperature is 70°C to 90°C and the vacuum degree is -0.095MPa.

8. The process according to claim 1, characterized in that, In step 4), the drying temperature is 70℃~90℃; The drying time is 5 to 9 hours.

9. The process according to claim 1, characterized in that, After the reaction proceeds continuously for 48 hours, the fixed-bed catalyst module is flushed with an ethanol solution of sodium sulfide in the opposite direction to the normal reaction flow for 2 hours, then flushed with anhydrous ethanol and dried with nitrogen to complete catalyst regeneration; the concentration of the ethanol solution of sodium sulfide is 0.05 mol / L to 0.2 mol / L.

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