Process for preparing high-purity lithium sulfide through layer interface induction strengthening

Abstract

The invention provides a process for preparing high-purity lithium sulfide through layer interface induction strengthening, which comprises the following steps: dissolving lithium chloride and sodium sulfide in N-methyl pyrrolidone, and stirring to form uniform slurry; pumping the obtained slurry into a fixed bed reactor filled with a molybdenum disulfide catalyst layered module, and reacting to obtain turbid liquid; performing temperature-controlled crystallization on the turbid liquid, filtering and separating to obtain sodium chloride crystals; performing reduced pressure distillation on the filtrate to obtain a lithium sulfide crude product; and dissolving the lithium sulfide crude product in absolute ethyl alcohol for washing, and carrying out suction filtration and drying to obtain lithium sulfide. According to the method disclosed by the invention, fixed bed catalytic reaction and programmed cooling crystallization separation are integrated, and process parameters are optimized, so that the core pain points of high energy consumption, poor safety, difficulty in separation, easiness in catalyst deactivation and the like in a traditional method are successfully solved; a green closed loop of the whole process flow is realized, and a reliable technical path is provided for industrial production of the high-performance lithium sulfide material.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of battery materials, in particular to a process for preparing high-purity lithium sulfide by layer interface-induced strengthening. BACKGROUND

[0002] Lithium ion battery technology is evolving towards high energy density and high safety, among which, the solid-state battery system using inorganic solid-state electrolyte (especially sulfide electrolyte) is considered as an ideal path to solve the key problems of traditional liquid lithium battery such as insufficient electrochemical / thermal stability and poor safety. Among the many solid-state electrolyte materials, sulfide electrolyte has become the focus of research and development in the academic and industrial fields because it has extremely high ionic conductivity (comparable to liquid electrolyte), excellent mechanical ductility (easy to form a dense interface), and good electrochemical stability.

[0003] As an indispensable lithium source and sulfur source precursor for synthesizing sulfide solid-state electrolyte, the material purity, morphology and cost of lithium sulfide directly determine the performance and commercial feasibility of the final electrolyte and battery system. However, the wide 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-state batteries. ② Material environmental sensitivity: Li2S is prone to hydrolysis reaction (Li2S + 2H2O → 2LiOH + H2S↑) in air, releasing toxic hydrogen sulfide gas, so all synthesis, storage and post-processing processes must be carried out in a strictly controlled inert atmosphere (such as argon glove box), significantly increasing the process complexity and cost. ③ Balance between nanocrystallization and purity control: In order to improve the interface contact and ion transport efficiency of solid-state batteries, nanoscale Li2S materials are usually required. However, nanocrystallization will further exacerbate its surface activity, making it extremely difficult to control purity, prevent oxidation and ensure dispersion stability.

[0004] The methods for preparing Li2S in laboratories and industries can be mainly divided into three categories: ball milling method, carbon thermal reduction method and compound reaction method. The ball milling method has a top-down physical crushing method and a bottom-up mechanical force chemical synthesis method. This kind of method has a simple process route, low equipment requirement and large-scale production potential. The carbon thermal reduction method usually uses lithium sulfate as a lithium source and a carbon source to react at high temperature; this kind of method has a mature process and can directly prepare Li2S-carbon composite materials, which is suitable for specific electrode systems. The compound reaction method uses lithium-containing compounds (such as LiH, lithium carbonate) and active sulfur sources (such as hydrogen sulfide) to react in gas or liquid phase to generate Li2S. This kind of method has various reaction paths and can to some extent regulate the morphology of the product through precursor design.

[0005] In summary, lithium sulfide as a key basic material to promote the breakthrough of the next generation of solid-state battery technology, its high performance potential and harsh preparation challenges coexist. Future technological development will focus on developing low-cost, low-energy, high-purity, and green synthesis of new routes that can achieve nanoscale precise control. Breaking through the limitations of existing ball milling, carbon thermal reduction, and inter-compound reaction methods is of decisive significance to accelerate the commercialization process of sulfide solid-state batteries. SUMMARY

[0006] To solve the above problems, the present application aims to provide a process for preparing high-purity lithium sulfide by layer interface induced strengthening, which is a new technology that can balance low cost, high purity, good morphology control, and safety and environmental protection for large-scale synthesis.

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

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

[0009] Step 2): Pump the slurry obtained in step 1) into a fixed bed reactor containing a molybdenum disulfide catalyst module, react to obtain a suspension;

[0010] Step 3): Control the temperature of the suspension to crystallize, filter and separate to obtain sodium chloride crystals; distill the filtrate under reduced pressure to obtain lithium sulfide crude product;

[0011] Step 4): Dissolve the lithium sulfide crude product 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, and any one of the ranges formed by any two of the above values.

[0013] In some embodiments, the volume-to-mass ratio of N-methyl pyrrolidone to lithium chloride is 30:(1-2). Preferably, it is 30:1, 30:1.5, 30:2, and any one of the ranges formed by any two of the above values.

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

[0015] In some embodiments, the slurry is pumped at a space velocity of 1 h -1 to 5 h -1 , and preferably 1 h -1 , 2 h -1 , 3 h -1 , 4 h -1 , 5 h -1 , and any one of the ranges formed by any two of the above values. The choice of space velocity needs to balance the reaction conversion rate and the processing capacity of the equipment. The fixed bed reactor provides a stable reaction environment, which is conducive to mass transfer and reaction control. The slurry undergoes metathesis reaction when passing through the catalyst bed, and lithium chloride and sodium sulfide react to form lithium sulfide and sodium chloride.

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

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

[0018] In some embodiments, the molybdenum disulfide catalyst module is prepared by mixing molybdenum disulfide nanosheets with a binder, then adding anhydrous ethanol to make a slurry, coating it on a cordierite honeycomb ceramic carrier, and drying to make a molybdenum disulfide catalyst module. The molybdenum disulfide catalyst provides high-efficiency catalytic active centers, significantly reducing the reaction activation energy, allowing the reaction to proceed efficiently at a mild temperature.

[0019] In some embodiments, the binder is one of tetraethyl orthosilicate, hydroxyethyl methacrylate, methyl acrylate. The amount of binder is 1% to 10% of the weight of the molybdenum disulfide nanosheet, preferably any one of the ranges formed by any two of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% and above. The catalyst prepared with tetraethyl orthosilicate as the binder has better fluidity and stability, can reduce the coating frequency and the disengagement rate while ensuring the coating amount, and the coating is relatively firm. The amount of anhydrous ethanol is 10% to 20% of the weight of the molybdenum disulfide nanosheet, preferably any one of the ranges formed by any two of 10%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20% and above.

[0020] In some embodiments, in step 2), the reaction is carried out at normal pressure and at 50-70°C. Preferably, any one of the ranges formed by any two of 50°C, 60°C and 70°C and above.

[0021] In some embodiments, the temperature-controlled crystallization refers to transferring the suspension into a crystallization kettle, and cooling to 5°C at a rate of 1-5°C / min, preferably any one of the ranges formed by any two of 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min and above. If necessary, a small amount of sodium chloride seed crystal can be added to induce crystallization. The combination of programmed cooling and seed crystal addition is the core of high-efficiency separation by taking advantage of the difference in solubility of Li2S and NaCl in NMP with temperature (the solubility of NaCl decreases significantly with temperature, while the solubility of Li2S changes relatively gently). Slow cooling and control of nucleation rate help to obtain large particles of NaCl crystals that are easy to filter, reducing the wrapping and entrainment of Li2S.

[0022] In some embodiments, the temperature of the reduced pressure distillation is 70-90°C, and the vacuum degree is -0.095 MPa, preferably any one of the ranges formed by any two of 70°C, 80°C, 90°C and above.

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

[0024] The vacuum distillation realizes efficient recovery of NMP solvent, greatly reduces production cost and environmental impact. The selection of ethanol as the washing solvent is the key, which can selectively dissolve and remove LiCl impurities, while the solubility of Li2S product is extremely low, thereby significantly improving the product purity while ensuring high recovery rate. The vacuum drying completely removes the residual volatile solvent.

[0025] Further, after the reaction is continuously carried out for 48 hours (or when the Li2S content in the reactor outlet material is obviously reduced, indicating that the catalyst activity is attenuated), the fixed bed catalyst is flushed with an ethanol solution of sodium sulfide in the opposite direction of the normal reaction flow for 2 hours, then flushed with anhydrous ethanol, and dried with nitrogen, to complete the catalyst regeneration. The regular reverse cleaning can effectively loosen the bed and flush away the physical blockage. The ethanol regeneration solution containing sodium sulfide can chemically remove specific poisons. This regeneration process is simple and effective, which can significantly prolong the service life of the catalyst and ensure the continuous and stable operation of the entire system.

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

[0027] Advantages

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

[0029] (2) The present application uses a molybdenum disulfide catalyst module installed in a fixed bed reactor, which significantly accelerates the double decomposition reaction rate and improves the raw material conversion rate. The fixed bed continuous operation mode is beneficial to process control and scale-up.

[0030] (3) The present application uses programmed cooling crystallization technology to selectively precipitate by-product sodium chloride, and uses the solubility difference of lithium sulfide and sodium chloride in NMP solvent with temperature change to realize efficient separation of by-products; the present application optimizes the cooling rate and end temperature, and adds crystal seeds, to obtain sodium chloride crystals with uniform particle size and easy filtration, thereby ensuring the high purity of the subsequent lithium sulfide solution.

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

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

[0033] (6) The present application designs a special catalyst regeneration step, which can effectively restore the activity of the catalyst deactivated due to salt deposition or slight poisoning, so that the activity is restored to more than 96% of the initial activity, ensuring long-term stable operation of the reactor and reducing the frequency and cost of catalyst replacement.

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

[0035] (8) The present application integrates fixed-bed catalytic reaction with programmed temperature reduction crystallization separation, and optimizes the process parameters, forming a high-efficiency, clean, stable and economical continuous preparation method of lithium sulfide. This scheme not only successfully solves the core pain points of high energy consumption, poor safety, difficult separation and easy deactivation of catalyst in traditional methods, but also realizes the green closed loop of the entire process through the recycling of solvents and the resource utilization of by-products, providing a reliable technical path for the industrial production of high-performance lithium sulfide materials. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 XRD pattern of lithium sulfide prepared in Example 1.

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

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

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

[0040] TERMS

[0041] Certain embodiments of the application are now described in detail by reference to the accompanying figures and the following description. The application is intended to encompass all alternatives, modifications and equivalents thereof which are included within the scope of the application as defined by the claims. One skilled in the art will recognize that many methods and materials equivalent to those described herein can be used in the practice of the application. The present application is not limited to the methods and materials described herein. In the event of a conflict between the incorporated documents, patents and similar materials and the present application, including but not limited to defined terms, term application, described techniques, and the like, the present application controls.

[0042] It is to be further understood that, for brevity, certain aspects of the application are described in terms of separate embodiments or examples. It is to be understood that these aspects, features, structures, characteristics and the like described in connection with one embodiment or example can be applied to any other embodiment or example described herein or in connection with which an analogous feature, structure, characteristic or the like is described. In other words, the described aspects, features, structures, characteristics and the like are not limited to the particular embodiment or example with which they are described.

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

[0044] In the description of the specification, the description using the terms "one embodiment", "some embodiments", "an example", "a specific example" or "some examples" and the like means that the particular feature, structure, material or characteristic following the term is included in at least one embodiment or example of the application. The illustrative appearances of the above-mentioned terms in the description are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics can be combined in any suitable manner in one or more embodiments or examples. In addition, the terms "comprising", "containing", "having" and the like when used in the specification mean that the respective feature, structure, material or characteristic can or can not be present, but when present, can be present in any suitable amount.

[0045] In the following disclosure, all numbers disclosed herein are approximations that can vary depending on the desired properties sought to be obtained by those of ordinary skill in the art. The numerical values in some embodiments can vary by 1%, 2%, 5%, 7%, 8%, 10%, 15%, or 20% of the indicated value. Whenever a numerical range is disclosed, any number within that range is also expressly disclosed. In some embodiments, the number of steps within a disclosed process can vary so long as the required results are achieved. Other values for materials such steps and the like can be used. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with examples. The specific examples described herein are only used to explain the present application and do not constitute any limitation on the present application. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present disclosure. Such structures and technologies are also described in many publications.

[0047] The reagents used in the present application can be purchased from the market or can be prepared by the methods described in the present application.

[0048] Anhydrous lithium chloride with a purity of ≥99.9% and pre-processed by vacuum drying at 120°C to completely remove water to avoid adverse effects on subsequent reactions and catalysts.

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

[0050] N-methyl pyrrolidone (NMP) dried by 4A molecular sieve to ensure that the water content is less than 50 ppm, which is a key prerequisite for maintaining high activity and reaction selectivity of the catalyst.

[0051] Preparation of molybdenum disulfide catalyst module

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

[0053] 2) After stirring the transparent solution of mixture A, place it in a 40 mL hydrothermal reactor and heat it at 200°C for 24 hours. After the reaction is completed, naturally cool it to room temperature. The product is centrifuged, washed with water and ethanol several times, and then vacuum dried at 60°C for 12 hours to obtain molybdenum disulfide nanosheet powder.

[0054] 3) Mix the molybdenum disulfide nanosheet powder with the binder tetraethyl orthosilicate (mass ratio of 10:1), add 20% of the weight of the molybdenum disulfide nanosheet anhydrous ethanol dilution to make a slurry, and coat it on the cordierite honeycomb ceramic carrier to make a molybdenum disulfide catalyst module. The molybdenum disulfide nanosheet (specific surface area 800 m 2 / g) has unique electronic structure and surface properties, which provides an efficient catalytic path for the metathesis reaction.

[0055] Example 1

[0056] Step 1: Raw material homogenization: In a glove box under nitrogen protection, 10.0 g of anhydrous lithium chloride and 15.6 g of anhydrous sodium sulfide were weighed into a 500 mL three-necked flask, and 300 mL of molecular sieve-dried N-methyl pyrrolidone was added as a solvent. The solids were fully dispersed by magnetic stirring at room temperature at a speed of 500 rpm for 30 minutes to form a homogeneous slurry.

[0057] Step 2: Catalytic reaction: The slurry was pumped into a fixed-bed reactor (2 cm in diameter and 20 cm in length) containing the above-mentioned molybdenum disulfide catalyst module at a space velocity of 2 h -1 -1 under normal pressure and at 60°C to obtain a flow-out liquid. The flow-out liquid was a suspension containing lithium sulfide, sodium chloride, and unreacted raw materials.

[0058] Step 3: Crystallization and separation: The reaction flow-out liquid was transferred to a crystallization kettle and was programmed to cool at a rate of 1°C / min at a stirring speed of 100 rpm. When the temperature dropped to about 15°C, 0.1 g of pre-prepared pure NaCl seed crystals were added to induce crystallization. After reaching 5°C, the temperature was maintained for 2 hours to allow the crystals to grow completely and uniformly. Subsequently, the suspension was transferred to a pre-cooled Buchner funnel for suction filtration to separate the NaCl crystals. The filtrate was an NMP solution rich in Li2S.

[0059] Step 4: Solvent recovery and product purification: The filtrate was subjected to vacuum distillation (temperature 80°C, vacuum degree -0.095 MPa) to recover the NMP solvent. The distillation residue was a crude Li2S. The crude Li2S was washed with 50 mL of anhydrous ethanol in three batches, each for 15 minutes, to dissolve and remove trace amounts of LiCl impurities. After washing, the solid was suction filtered and dried at 80°C under vacuum for 6 hours to obtain a white powder of high-purity lithium sulfide product.

[0060] Step 5: Catalyst regeneration: After the reactor was continuously operated for 48 hours, the catalyst bed was 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 finally dried with nitrogen for 2 hours to complete the catalyst regeneration.

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

[0062] As shown in the XRD analysis chart of the lithium sulfide product prepared in Example 1, the XRD test of the lithium sulfide product obtained in Example 1 had a diffraction spectrum that matched well with the Li2S standard card, with no obvious impurity peaks, indicating that the product had good crystallinity and high purity. Figure 1 ​

[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 running for 48 hours, the reaction is continued without regeneration. It is found that the Li2S content in the reaction effluent has dropped to less than 85% of the initial value by 72 hours, indicating that the catalyst activity has dropped significantly and regeneration of the catalyst is required.

[0077] Example 5

[0078] The catalyst is regenerated according to the process described in Step 5 of Example 1. After regeneration, the reaction process is restarted and the Li2S content of the initial reaction effluent is monitored. The results show that the initial activity of the catalyst after regeneration has recovered to 96% of the activity of the fresh catalyst. This shows that the regeneration process designed in the present application can effectively recover the activity of the catalyst and meet the needs of long-term industrial operation.

[0079] Example 1

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

[0081] 2) Elements 1-54 are detected by ICP-MS; elements 55-63 are detected by ICP.

[0082] 3) Except for lithium (Li), which is diluted 400 times for detection, the rest of the elements are not diluted.

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

[0084] Table 3 Detection of each element in the samples prepared in the examples

[0085]

[0086] Continuation of Table 3

[0087]

[0088] Continuation of Table 3

[0089]

[0090] As can be seen from Table 3, the purity of lithium sulfide obtained in Example 1 and Example 2-3 is 99.9%, and the impurity content of each substance is very low.

[0091] The methods of the present application have been described by way of preferred embodiments, and modifications or suitable variations and adaptations of the methods and applications described herein can be made by those skilled in the art in the light of the content, spirit and scope of the present application, to implement and apply the present technology. Those skilled in the art can make appropriate modifications to the process parameters based on the content herein to implement. It is particularly important to note that all such obvious substitutions and modifications are within the scope of the present application.

Claims

1. A process for the production of high purity lithium sulfide by interfacial strengthening induction, characterized in that, The application relates to a preparation method of lithium sulfide. Step 1): lithium chloride and sodium sulfide are dissolved in N-methylpyrrolidone to form a uniform slurry by stirring; Step 2): the slurry obtained in step 1) is pumped into a fixed-bed reactor provided with a molybdenum disulfide catalyst module, and reaction is carried out to obtain a suspension; Step 3): the suspension is subjected to temperature-controlled crystallization, filtration separation is carried out, and sodium chloride crystals are obtained; the filtrate is subjected to vacuum distillation to obtain lithium sulfide crude products; Step 4): the lithium sulfide crude products are dissolved in anhydrous ethanol, washed, filtered and dried to obtain lithium sulfide.

2. The process of claim 1 wherein, The mass ratio of the lithium chloride and the sodium sulfide is 1: (1-2); the volume-mass ratio of the N-methylpyrrolidone and the lithium chloride is 30: (1-2).

3. The process of claim 1 wherein, In step 1), the stirring speed is 500 rpm-1500 rpm, and the stirring time is 20 min-40 min; the reaction temperature is 15 DEG C-35 DEG C.

4. The process of claim 1 wherein, The slurry is pumped in at 1 h -1 ~5 h -1 of air speed. The molybdenum disulfide is at least one of molybdenum disulfide nanosheets and molybdenum sulfide / titanium carbide composite materials.

5. The process of claim 4 wherein, The molybdenum disulfide nanosheets are prepared by dissolving sodium molybdate and thiourea in deionized water to form a uniform solution, then reacting at 150 DEG C-250 DEG C for 24 h-36 h, cooling, centrifuging, washing with water and drying; The molybdenum disulfide catalyst module is prepared by mixing the molybdenum disulfide nanosheets with a binder, adding anhydrous ethanol to prepare a slurry, coating the slurry on a cordierite honeycomb ceramic carrier and air-drying.

6. The process of claim 5 wherein, The binder is one of tetraethyl orthosilicate, hydroxyethyl methacrylate and methyl acrylate; the amount of the binder is 1%-10% of the weight of the molybdenum disulfide nanosheets.

7. The process of claim 1 wherein, In step 2), the reaction is carried out at normal pressure and 50 DEG C-70 DEG C.

8. The process of claim 1 wherein, The temperature-controlled crystallization refers to that the suspension is transferred into a crystallization kettle, and the temperature is lowered to 5 DEG C at a speed of 1 DEG C / min-5 DEG C / min; the temperature of the vacuum distillation is 70 DEG C-90 DEG C, and the vacuum degree is -0.095 MPa.

9. The process of claim 1 wherein, In step 4), the drying temperature is 70 DEG C-90 DEG C; The drying time is 5 h-9 h.

10. The process of claim 1 wherein, After the reaction is continuously carried out for 48 h, the fixed-bed catalyst module is washed with an ethanol solution of sodium sulfide in a direction opposite to the normal reaction flow direction for 2 h, then washed with anhydrous ethanol, dried with nitrogen, and catalyst regeneration is completed; the concentration of the ethanol solution of sodium sulfide is 0.05 mol / L-0.2 mol / L.

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