Process for the preparation of lithium sulfide, product and use

Abstract

The application provides a preparation method, product and application of lithium sulfide, and belongs to the technical field of inorganic compound synthesis. The lithium sulfide with high product purity and low carbon content is obtained through four steps of lithium source pretreatment, lithium sulfite intermediate synthesis, lithium sulfite reduction and product post-treatment by using anhydrous lithium hydroxide or lithium oxide as a lithium source, sulfur dioxide as an acidifying agent and hydrogen or methane as a reducing gas, and can be directly applied to high-end fields such as full solid-state batteries and lithium-sulfur batteries, and has important significance and broad industrial application prospects for breaking through the industrialization bottleneck of full solid-state batteries.

Description

Technical Field

[0001] This invention belongs to the field of inorganic compound synthesis technology, specifically relating to a method for preparing lithium sulfide, its products, and applications. Background Technology

[0002] Li₂S is a typical inorganic compound, belonging to the binary lithium salt class, and has a face-centered cubic crystal structure. At room temperature and pressure, Li₂S is a white or pale yellow crystal with a melting point of approximately 938℃ and a density of approximately 1.67 g / cm³. 3 Li₂S possesses high thermal and chemical stability. It is relatively stable in an inert atmosphere, does not readily react with oxygen at room temperature, exhibits reducing properties at high temperatures, and can react with water to produce lithium hydroxide and hydrogen sulfide gas, demonstrating strong hydrolytic activity. Therefore, its preparation, storage, and application processes must strictly control environmental humidity and oxygen content. Li₂S is a functional material that combines high theoretical specific capacity, high energy density, and interfacial stability, showing broad application prospects in multiple high-performance fields, and playing a particularly important role in electrochemical energy storage systems. In next-generation battery systems such as lithium-sulfur batteries and all-solid-state batteries, Li₂S can serve as a precursor for cathode materials and can also participate in the construction of composite solid-state electrolytes under certain conditions. The charging and excitation process of Li₂S typically involves electrochemical reactions in lithium-ion batteries. During charging, lithium ions migrate from the negative electrode to the positive electrode, while during excitation, electron transfer and chemical reactions also affect the lithiation process. Its conductivity significantly improves under high-temperature conditions, enabling it to form good interfacial matching with various sulfide electrolytes, making it a crucial fundamental material for achieving a balance between high energy density, safety, and lifespan. Beyond battery systems, Li₂S plays a unique role in thermoelectric materials, organic synthesis, and functional ceramics. In thermoelectric conversion, introducing Li₂S into solid solutions such as Li-Sn-S can effectively improve carrier mobility and the figure of merit (ZT), making it suitable for high-temperature thermoelectric devices. In fine chemicals and pharmaceutical synthesis, Li₂S, as a highly reactive sulfur source, can be used to construct various sulfur-containing organic molecules, such as thioethers, thioamides, and ligand-based functional materials, exhibiting unique advantages in highly selective synthesis and directed catalytic reactions.

[0003] In battery technology, Li₂S applications are concentrated in lithium-sulfur batteries and all-solid-state battery systems. Unlike lithium metal anodes, Li₂S exhibits higher chemical stability and lower reactivity, which helps improve the safety of battery assembly and avoids safety risks such as dendrite formation and short circuits caused by lithium metal. In lithium-sulfur batteries, Li₂S can serve as a pre-lithiated cathode precursor, with a theoretical specific capacity far exceeding that of traditional oxide or phosphate cathode materials, significantly improving overall energy density. In all-solid-state systems, Li₂S exhibits good interface compatibility with typical sulfide electrolytes, making it suitable for constructing continuous ion channel structures, which is beneficial for improving charge transfer efficiency and interface stability. These composite battery structures are particularly suitable for applications with extremely high requirements for energy density, safety, and stability, such as aerospace, military equipment, and high-end electric vehicles.

[0004] However, high-performance battery applications place stringent requirements on the purity and structure of Li₂S materials. Trace impurities, such as Li₂CO₃, LiOH, and Li₂SO₄, can interfere with electrode interface stability, increase the tendency for side reactions, and thus affect battery cycle life and coulombic efficiency. Therefore, reaction conditions must be strictly controlled during material synthesis to ensure product purity and achieve uniform particle size distribution, pure crystal form, and the absence of impurity phases. High-purity Li₂S materials should also possess good micro / nano structure control capabilities to form a large contact area electrode interface with the electrolyte, thereby improving reaction efficiency.

[0005] Currently, there are various methods for synthesizing Li2S, including solid-phase reaction, solution method, gas-phase method and carbon reduction method.

[0006] The basic process of the solid-state reaction method involves reacting lithium metal or its compounds with sulfur at high temperatures to produce Li₂S. The reaction is typically carried out in an inert atmosphere (such as nitrogen or argon). The temperature range for this reaction is controlled between 400-800℃, primarily to avoid vigorous reaction or imbalance of reactant proportions due to sulfur evaporation. The advantages of this method are its relative simplicity, low equipment requirements, and the wide availability and low cost of raw materials, making it suitable for batch reactions and a commonly used method in laboratory and early-stage engineering preparations. However, this method also has certain limitations: for example, the reaction at high temperatures can easily introduce byproducts; the reaction process is vigorous, especially when using lithium metal as a raw material, posing significant safety risks; and to improve the synthesis quality, auxiliary methods such as mechanical ball milling, cold pressing, and inert encapsulation are often introduced to improve the reaction interface, uniformity, and safety, but these methods increase the complexity of the process to some extent.

[0007] Solution-based methods primarily involve the reaction of a lithium source (such as LiOH or Li₂CO₃) with a sulfur source (such as Na₂S or CS₂) in a solvent to generate Li₂S precipitate, which is then obtained through heat treatment. This method is typically carried out under relatively mild conditions, facilitating reaction control and morphology adjustment. It is particularly suitable for preparing specific structures such as nanoparticles, spherical or sheet-like structures, and helps improve the dispersibility and interfacial reaction performance of materials in subsequent applications. However, this method may introduce more impurities, requiring additional purification steps to improve product quality. Furthermore, the post-processing steps are cumbersome, often involving multiple processes such as solvent removal, washing, and drying.

[0008] The gas-phase reaction method typically uses sulfide gases such as hydrogen sulfide (H2S) and carbon disulfide (CS2) to react with lithium vapor or lithium compounds in a high-temperature atmosphere to produce Li2S. Although it can produce products with high purity, the equipment required for the reaction process is complex and expensive, and it places high demands on the system's sealing and reaction control. Furthermore, the hydrogen sulfide gas used in the reaction is highly toxic, posing significant safety risks.

[0009] The carbon reduction method typically uses lithium sulfate (Li₂SO₄) as the lithium source, which reacts with a carbon source (usually activated carbon, carbon black, or polymeric carbon precursor) at high temperatures to produce Li₂S, releasing gases such as CO or CO₂. The reaction is usually carried out in an inert atmosphere (such as Ar or N₂) at 700-900℃, offering advantages such as simple operation and inexpensive raw materials. However, the generated gases pose a challenge to the sealing of the equipment, and controlling residual carbon impurities is difficult, requiring additional heat treatment and post-purification processes.

[0010] While existing methods can yield relatively pure Li₂S to a certain extent, effectively controlling impurity formation, improving Li₂S purity, and ensuring the controllability and economy of the synthesis process remain pressing challenges. Furthermore, since the performance of high-purity Li₂S is significantly influenced by the synthesis process and reaction conditions, in-depth research into its synthesis methods and mechanisms, and the exploration of more efficient synthetic routes, are of great importance for improving the quality of Li₂S and its applications in various fields.

[0011] Relevant patent documents retrieved:

[0012] This document, published in China (CN112520763A) on March 19, 2021, discloses a method for preparing lithium sulfide using lithium sulfate. Addressing the drawbacks of commercially available lithium sulfide, such as high price and difficulty in guaranteeing purity, this invention utilizes a simple heating method to prepare high-purity lithium sulfide. Using lithium hydride and lithium sulfate as raw materials, lithium sulfide powder can be obtained through simple heating, heat preservation, and purification processes. This method is simple, rapid, and can produce high-purity lithium sulfide at low cost. However, the purity and carbon content of the lithium sulfide prepared by this invention do not fully meet the required standards.

[0013] This document, published in China (CN121247729A) on January 2, 2026, discloses a method for preparing lithium sulfide by hydrogen reduction of lithium sulfate. The specific technical solution involves pulverizing lithium sulfate to micron-level particles and feeding it into a fluidized bed reactor. High-purity hydrogen gas, preheated to 850°C, is then introduced from the bottom of the reactor, controlling the reaction temperature at 850±20°C and the reaction time at 5-10 minutes. This invention utilizes a hydrogen reduction method with a relatively low reaction temperature (700-900°C), and hydrogen acts as a clean reducing agent, with water as the only byproduct. This avoids the problems of insufficient purity, high energy consumption, and significant environmental pollution associated with traditional lithium sulfide preparation methods. The introduction of fluidized bed technology can greatly enhance the gas-solid phase heat and mass transfer efficiency, enabling continuous and automated processes, which is an important path to the industrialization of this reaction. However, the reduction temperature disclosed in this application is still above 700°C, and the purity and carbon content of the obtained lithium sulfide do not better meet the requirements.

[0014] Relevant non-patent literature retrieved:

[0015] The journal is *Green Chemistry*, and the article title is "Preparation of high-quality lithium sulfide by reducing lithium sulfate with hydrogen: a green and cost-effective method" (Green Chem., 2024, 26, 7231), published on May 15, 2024. This article discloses a novel method for preparing lithium sulfide by reducing lithium sulfate with hydrogen. First, the optimal pretreatment method for lithium sulfate was experimentally determined (sample III, using anhydrous ethanol as a dispersant for wet ball milling, drying, and then grinding with a pulverizer), and the optimal temperature for the reduction reaction was determined to be 700℃. During the subsequent lithium sulfide purification process, a small amount of lithium thiosulfate (Li₂S₂) impurity was found, which was subsequently completely removed using a reducing atmosphere. High-purity lithium sulfide (H-Li₂S) was finally obtained, with a purity of 99.96%. However, the article describes the need for complex pretreatment of the sample before the reduction reaction, requiring a "calcination-grinding-recalcination" process, and the reaction temperature still needs to reach 700℃. Summary of the Invention

[0016] Based on the shortcomings of existing technologies, this invention uses anhydrous lithium hydroxide or lithium oxide as the lithium source, sulfur dioxide as the acidifying agent, and hydrogen or methane as the reducing gas to prepare lithium sulfide. This method has advantages such as stable raw material sources, strong reaction controllability, environmental safety, simple post-processing, and high product purity (≥99.9%) and low carbon content (≤0.1%).

[0017] In order to achieve the above objectives, the present invention aims to provide:

[0018] A method for preparing lithium sulfide, and related technologies, to solve technical problems such as high reaction temperature, complex reaction and post-processing steps, or combinations thereof, in the prior art.

[0019] This invention obtains a lithium sulfide with high purity and low carbon content by using anhydrous lithium hydroxide or lithium oxide as the lithium source, sulfur dioxide as the acidifying agent, and hydrogen or methane as the reducing gas, through four steps: lithium source pretreatment, lithium sulfite intermediate synthesis, lithium sulfite reduction, and product post-treatment. It can be directly applied to high-end fields such as all-solid-state batteries and lithium-sulfur batteries. In particular, it is of great significance for breaking through the industrialization bottleneck of all-solid-state batteries and has broad prospects for industrial application.

[0020] Terminology Explanation:

[0021] Unless otherwise defined, all technical terms in this document have the same meanings as commonly understood by one of ordinary skill in the art to which the subject matter of the claims pertains. Unless otherwise stated, all patents, patent inventions, and publications cited in this document are incorporated herein by reference in their entirety. If multiple definitions exist for terms in this document, the definitions in this chapter shall prevail.

[0022] It should be understood that the above brief description and the following detailed description are exemplary and for illustrative purposes only, and do not limit the subject matter of the invention in any way. In this invention, the singular is used in conjunction with the plural unless otherwise specifically stated. It should also be noted that, unless otherwise stated, the use of “or” or “or” means “and / or”. Furthermore, the use of the term “comprising” and other forms such as “including,” “containing,” and “contains” are not limiting.

[0023] Unless otherwise stated, conventional methods within the scope of the art, such as mixing and stirring, shall be used.

[0024] Unless specifically defined herein, the use of various commercially available products herein employs standard techniques. For example, they may be implemented in a manner known in the art or as described in this invention. The techniques and methods described herein can generally be implemented according to conventional methods well known in the art, based on the descriptions in the various summary and more specific documents cited and discussed in this specification.

[0025] The terms “optional / arbitrary” or “optionally / arbitrarily” mean that the event or situation described below may or may not occur, including both the occurrence and non-occurrence of the event or situation.

[0026] In a first aspect, the present invention provides a method for preparing lithium sulfide.

[0027] The preparation method includes the following steps:

[0028] (1) Lithium source pretreatment: The lithium source is subjected to vacuum drying to remove water, and the pretreated lithium source is obtained;

[0029] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source is fed into the reactor and sulfur dioxide gas with a purity of ≥99.5% is introduced to react and produce lithium sulfite intermediate;

[0030] (3) Preparation of lithium sulfide: A reducing gas is introduced into the reactor to react with the lithium sulfite intermediate to obtain crude lithium sulfide.

[0031] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature, and then subjected to air jet milling to precisely control the particle size. After milling, it is directly vacuum dried to obtain the finished lithium sulfide product.

[0032] in:

[0033] The lithium source mentioned in step (1) above is anhydrous lithium hydroxide or lithium oxide, and the purity of the lithium source is ≥98%;

[0034] Preferably, the purity of the lithium source is ≥98.5%;

[0035] As a further preferred embodiment, the purity of the lithium source is any point or range of ≥98%, and can be selected from 98%, 98.5%, 98.9%, 99%, 99.2%, 99.5%, or 99.9%.

[0036] As the most preferred embodiment, the purity of the lithium source is ≥99%.

[0037] The specific preprocessing operations described in step (1) above are as follows:

[0038] When the lithium source is anhydrous lithium hydroxide, the drying temperature is 200-430℃, the vacuum degree is -0.05~-0.08MPa, and the drying time is 2-3h.

[0039] Preferably, the drying temperature is 250-400℃, the vacuum degree is -0.06~-0.07MPa, and the drying time is 2.5-3h;

[0040] As a further preferred embodiment, the drying temperature is any point or range between 250-400℃, and can be selected from 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃ or 400℃;

[0041] As a further preferred embodiment, the drying temperature is any point or range between 250-400℃, and can be selected from 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃ or 380℃.

[0042] As a further preferred embodiment, the drying temperature is any point or range between 250-400°C, and can be selected from 330°C, 340°C, 350°C or 360°C.

[0043] As the most preferred option, the drying temperature is 350°C.

[0044] As a further preferred embodiment, the vacuum degree is any point or range value between -0.05 and -0.08 MPa, and can be selected from -0.05 MPa, -0.055 MPa, -0.06 MPa, -0.065 MPa, -0.07 MPa, -0.075 MPa or -0.08 MPa;

[0045] As a further preferred embodiment, the vacuum degree is any point or range value between -0.05 and -0.08 MPa, and can be selected from -0.06 MPa, -0.065 MPa or -0.07 MPa;

[0046] As a further preferred embodiment, the vacuum degree is any point or range value between -0.05 and -0.08 MPa, and can be selected from -0.06 MPa or -0.065 MPa;

[0047] As the most preferred embodiment, the vacuum degree is -0.06 MPa.

[0048] As a further preferred embodiment, the drying time is any value or range between 2 and 3 hours, and can be selected from 2 hours, 2.2 hours, 2.5 hours, 2.8 hours or 3 hours;

[0049] As a further preferred embodiment, the drying time is any value or range between 2 and 3 hours, and can be selected from 2.2 hours, 2.5 hours, or 2.8 hours;

[0050] As the most preferred method, the drying time is 2.5 hours.

[0051] As a preferred embodiment, when the lithium source is anhydrous lithium hydroxide, the drying temperature for vacuum drying of the lithium source in the pretreatment step is 350°C, the vacuum degree is -0.06MPa, and the drying time is 2.5h.

[0052] The specific preprocessing operations described in step (1) above are as follows:

[0053] When the lithium source is lithium oxide, the drying temperature is 120-160℃, the vacuum degree is -0.05~-0.08MPa, and the drying time is 2-4h.

[0054] Preferably, the drying temperature is 130-150℃, the vacuum degree is -0.06~-0.07MPa, and the drying time is 2.5-3.5h;

[0055] As a further preferred embodiment, the drying temperature is any point or range between 120-160℃, and can be selected from 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃ or 160℃.

[0056] As a further preferred embodiment, the drying temperature is any point or range between 120-160℃, and can be selected from 140℃, 145℃, 150℃, 155℃ or 160℃.

[0057] As a further preferred embodiment, the drying temperature is any point or range between 120-160°C, and can be selected from 140°C, 145°C or 150°C.

[0058] As the most preferred embodiment, the drying temperature is 150°C.

[0059] As a further preferred embodiment, the vacuum degree is any point or range value between -0.05 and -0.08 MPa, and can be selected from -0.05 MPa, -0.055 MPa, -0.06 MPa, -0.065 MPa, -0.07 MPa, -0.075 MPa or -0.08 MPa;

[0060] As a further preferred embodiment, the vacuum degree is any point or range value between -0.05 and -0.08 MPa, and can be selected from -0.06 MPa, -0.065 MPa or -0.07 MPa;

[0061] As a further preferred embodiment, the vacuum degree is any point or range value between -0.05 and -0.08 MPa, and can be selected from -0.06 MPa or -0.065 MPa;

[0062] As the most preferred embodiment, the vacuum degree is -0.06 MPa.

[0063] As a further preferred embodiment, the drying time is any value or range between 2 and 4 hours, and can be selected from 2 hours, 2.2 hours, 2.5 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.5 hours, 3.8 hours or 4 hours;

[0064] As a further preferred embodiment, the drying time is any value or range between 2 and 4 hours, and can be selected from 3 hours, 3.2 hours, 3.4 hours, or 3.5 hours.

[0065] As the most preferred method, the drying time is 3.5 hours.

[0066] As a preferred embodiment, when the lithium source is lithium oxide, the drying temperature is 150°C, the vacuum degree is -0.06MPa, and the drying time is 3.5h.

[0067] The purpose of the above-mentioned pretreatment of the lithium source is to efficiently remove free water from the lithium source through vacuum drying, so as to avoid the adverse effects of moisture on subsequent reactions.

[0068] The reactor mentioned in step (2) above is a rotary kiln or a fluidized bed;

[0069] When the reactor is a rotary kiln, the rotation speed is controlled at 1-10 r / min, the filling rate is 10-30%, the reaction temperature in the low-temperature section is 50-80℃, and the reaction conditions are a gas space velocity of 500-1000 h⁻¹. -1 The reaction time is 6-8 hours; the reaction temperature in the mesophilic range is 100-320℃, and the reaction conditions are a gas space velocity of 1000-2000 h⁻¹. -1 The reaction time is 3-6 hours.

[0070] When the reactor is a rotary kiln, preferably, the rotation speed is controlled at 2-9 r / min, the filling rate is 12-28%, the reaction temperature in the low-temperature section is 55-75℃, and the reaction conditions are a gas space velocity of 600-900 h⁻¹. -1 The reaction time is 6.2-7.8 h; the reaction temperature in the mesophilic range is 120-300℃, and the reaction conditions are a gas space velocity of 1200-1800 h⁻¹. -1 The reaction time is 3-6 hours.

[0071] When the reactor is a rotary kiln, more preferably, the rotation speed is controlled at 3-8 r / min, the filling rate is 15-25%, the reaction temperature in the low-temperature section is 60-70℃, and the reaction conditions are a gas space velocity of 700-800 h⁻¹. -1 The reaction time is 6.5-7.5 h; the reaction temperature in the meso-temperature range is 150-250℃, and the reaction conditions are a gas space velocity of 1300-1600 h⁻¹. -1 The reaction time is 4-5 hours.

[0072] When the reactor is a rotary kiln, as a further preferred embodiment, the rotational speed is any point or range between 1 and 10 r / min, and can be selected from 1 r / min, 2 r / min, 3 r / min, 4 r / min, 5 r / min, 6 r / min, 7 r / min, 8 r / min, 9 r / min or 10 r / min;

[0073] When the reactor is a rotary kiln, as a further preferred embodiment, the rotational speed is any point or range between 1 and 10 r / min, and can be selected from 4 r / min, 5 r / min, 6 r / min, 7 r / min or 8 r / min;

[0074] When the reactor is a rotary kiln, as a further preferred embodiment, the rotational speed is any point or range between 1 and 10 r / min, and can be selected from 5 r / min, 6 r / min or 7 r / min;

[0075] When the reactor is a rotary kiln, as a more preferred embodiment, the rotational speed is any point or range between 1 and 10 r / min, and can be selected from 5 r / min;

[0076] When the reactor is a rotary kiln, as a further preferred embodiment, the filling rate is any point or range between 10% and 30%, which may be selected from 10%, 12%, 14%, 15%, 16%, 18%, 19%, 20%, 22%, 24%, 25%, 26%, 27%, 28%, or 30%.

[0077] When the reactor is a rotary kiln, as a further preferred embodiment, the filling rate is any point or range between 10-30%, which may be selected from 15%, 16%, 18%, 19%, 20%, 22%, 24%, or 25%.

[0078] When the reactor is a rotary kiln, as a further preferred embodiment, the filling rate is any value or range between 10-30%, which may be selected from 18%, 19%, 20% or 22%;

[0079] When the reactor is a rotary kiln, as a more preferred embodiment, the filling rate is any value or range between 10-30%, and may be selected from 20%;

[0080] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction temperature of the low-temperature section is any point or range between 50-80℃, which can be selected from 50℃, 52℃, 54℃, 55℃, 56℃, 57℃, 58℃, 60℃, 62℃, 64℃, 65℃, 66℃, 68℃, 70℃, 72℃, 75℃, 78℃ or 80℃;

[0081] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction temperature of the low-temperature section is any point or range between 50-80℃, which can be selected from 60℃, 62℃, 64℃, 65℃, 66℃, 68℃, 70℃, 72℃ or 75℃.

[0082] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction temperature of the low-temperature section is any point or range between 50-80°C, which can be selected from 60°C, 62°C, 64°C, 65°C, 66°C, 68°C or 70°C.

[0083] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction temperature of the low-temperature section is any point or range between 50-80°C, and can be selected from 65°C.

[0084] When the reactor is a rotary kiln, as a further preferred embodiment, the gas space velocity in the low-temperature section is 500-1000 h⁻¹. -1 Any point or range of values ​​between 500h -1 550h -1 600h -1 650h -1 700h-1 750h -1 800h -1 850h -1 900h -1 950h -1 or 1000h -1 ;

[0085] When the reactor is a rotary kiln, as a further preferred embodiment, the gas space velocity in the low-temperature section is 500-1000 h⁻¹. -1 Any point or range of values ​​between 600h -1 650h -1 700h -1 750h -1 800h -1 850h -1 or 900h -1 ;

[0086] When the reactor is a rotary kiln, as a further preferred embodiment, the gas space velocity in the low-temperature section is 500-1000 h⁻¹. -1 Any point or range of values ​​between 700h -1 750h -1 800h -1 or 850h -1 ;

[0087] When the reactor is a rotary kiln, as a further preferred embodiment, the gas space velocity in the low-temperature section is 500-1000 h⁻¹. -1 Any point or range of values ​​between 800h -1 ;

[0088] When the reactor is a rotary kiln, as a further preferred embodiment, any point or range of the reaction time in the low-temperature section between 6 and 8 hours can be selected from 6 hours, 6.2 hours, 6.5 hours, 6.8 hours, 7 hours, 7.2 hours, 7.5 hours, 7.8 hours, or 8 hours.

[0089] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction time of the low-temperature section can be any value or range between 6 and 8 hours, and can be selected from 6.5 hours, 6.8 hours, 7 hours, 7.2 hours, or 7.5 hours.

[0090] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction time of the low-temperature section can be any value or range between 6 and 8 hours, and can be selected from 6.5 hours, 6.8 hours or 7 hours.

[0091] When the reactor is a rotary kiln, as a further preferred embodiment, any point or range of the reaction time in the low-temperature section between 6 and 8 hours may be selected from 7 hours.

[0092] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction temperature in the intermediate temperature section is any point or range between 100-320℃, which can be selected from 100℃, 120℃, 130℃, 150℃, 180℃, 200℃, 220℃, 250℃, 260℃, 280℃, 300℃ or 310℃.

[0093] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction temperature in the intermediate temperature section is any point or range between 100-320℃, which can be selected from 150℃, 180℃, 200℃, 220℃ or 250℃.

[0094] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction temperature in the intermediate temperature section is any point or range between 100-320°C, and can be selected from 200°C, 220°C or 250°C.

[0095] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction temperature in the intermediate temperature section is any point or range between 100-320°C, and can be selected from 250°C.

[0096] When the reactor is a rotary kiln, as a further preferred embodiment, the gas space velocity in the intermediate temperature section is 1000-2000 h⁻¹. -1 Any point or range of values ​​between 1000h -1 1100h -1 1200h -1 1300h -1 1400h -1 1500h -1 1600h -1 1700h -1 1800h -1 1900h -1 or 2000h -1 ;

[0097] When the reactor is a rotary kiln, as a further preferred embodiment, the gas space velocity in the intermediate temperature section is 1000-2000 h⁻¹. -1 Any point or range of values ​​between 1200h -1 1300h -1 1400h -1 1500h -1 1600h -1 1700h -1 or 1800h -1 ;

[0098] When the reactor is a rotary kiln, as a further preferred embodiment, the gas space velocity in the intermediate temperature section is 1000-2000 h⁻¹. -1 Any point or range of values ​​between 1500h -1 1600h -1 1700h -1 or 1800h -1 ;

[0099] When the reactor is a rotary kiln, as a further preferred embodiment, the gas space velocity in the intermediate temperature section is 1000-2000 h⁻¹. -1 Any point or range of values ​​between 1800h -1 ;

[0100] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction time in the intermediate temperature section is any value or range between 3 and 6 hours, and can be selected from 3 hours, 3.2 hours, 3.5 hours, 3.8 hours, 4 hours, 4.2 hours, 4.5 hours, 4.8 hours, 5.0 hours, 5.2 hours, 5.5 hours, 5.8 hours or 6 hours.

[0101] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction time in the intermediate temperature section is any value or range between 3 and 6 hours, and can be selected from 4 hours, 4.2 hours, 4.5 hours, 4.8 hours, 5.0 hours, 5.2 hours or 5.5 hours;

[0102] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction time in the intermediate temperature section is any value or range between 3 and 6 hours, and can be selected from 5.0 hours, 5.2 hours or 5.5 hours;

[0103] When the reactor is a rotary kiln, as a further preferred embodiment, the reaction time in the intermediate temperature section is any value or range between 3 and 6 hours, and can be selected from 5.0 hours.

[0104] As a preferred embodiment, when the reactor is a rotary kiln, the rotation speed is controlled at 5 r / min, the filling rate is 20%, the reaction temperature in the low-temperature section is 65°C, and the reaction conditions are a gas space velocity of 800 h⁻¹. -1 The reaction time was 7 hours; the reaction temperature in the mesophilic phase was 250°C, and the reaction conditions were a gas space velocity of 1800 h⁻¹. -1 The reaction time is 5 hours.

[0105] When the reactor is a fluidized bed, the apparent gas velocity is controlled at 0.1-0.5 m / s, the bed temperature uniformity is ±5℃, the reaction temperature in the low temperature section is 50-80℃, and the reaction time is 4-6 h; the reaction temperature in the medium temperature section is 200-440℃, and the reaction time is 2-4 h.

[0106] When the reactor is a fluidized bed, preferably, the apparent gas velocity is controlled at 0.2-0.4 m / s, the bed temperature uniformity is ±5℃, the reaction temperature in the low-temperature section is 60-70℃, and the reaction time is 4.5-5.5 h; the reaction temperature in the medium-temperature section is 300-400℃, and the reaction time is 2.5-3.5 h.

[0107] When the reactor is a fluidized bed, as a further preferred embodiment, the apparent gas velocity of the control gas can be selected from any point or range between 0.1 and 0.5 m / s, including 0.1 m / s, 0.15 m / s, 0.2 m / s, 0.25 m / s, 0.3 m / s, 0.35 m / s, 0.4 m / s, 0.45 m / s, or 0.5 m / s.

[0108] When the reactor is a fluidized bed, as a further preferred embodiment, the apparent gas velocity of the control gas can be selected from any point or range between 0.1-0.5 m / s, such as 0.2 m / s, 0.25 m / s, 0.3 m / s, 0.35 m / s, or 0.4 m / s.

[0109] When the reactor is a fluidized bed, as a further preferred embodiment, the apparent gas velocity of the control gas can be selected as any point or range value between 0.1-0.5 m / s, such as 0.3 m / s, 0.35 m / s, or 0.4 m / s.

[0110] When the reactor is a fluidized bed, as a further preferred embodiment, the apparent gas velocity of the control gas can be selected as 0.35 m / s at any point or range between 0.1 and 0.5 m / s.

[0111] When the reactor is a fluidized bed, as a further preferred embodiment, the reaction temperature of the low-temperature section is any point or range between 50-80℃, which can be selected from 50℃, 52℃, 54℃, 55℃, 57℃, 60℃, 62℃, 65℃, 68℃, 70℃, 72℃, 75℃, 78℃ or 80℃.

[0112] When the reactor is a fluidized bed, as a further preferred embodiment, the reaction temperature of the low-temperature section is any point or range between 50-80℃, which can be selected from 60℃, 62℃, 65℃, 68℃, 70℃, 72℃ or 75℃.

[0113] When the reactor is a fluidized bed, as a further preferred embodiment, the reaction temperature of the low-temperature section is any point or range between 50-80°C, which can be selected from 65°C, 68°C, 70°C, 72°C or 75°C.

[0114] When the reactor is a fluidized bed, as a further preferred embodiment, the reaction temperature of the low-temperature section is any point or range between 50-80°C, and can be selected from 70°C;

[0115] When the reactor is a fluidized bed, as a further preferred embodiment, any point or range of the low-temperature reaction time between 4 and 6 hours can be selected from 4 hours, 4.2 hours, 4.5 hours, 4.8 hours, 5 hours, 5.2 hours, 5.5 hours, 5.8 hours, or 6.0 hours.

[0116] When the reactor is a fluidized bed, as a further preferred embodiment, any point or range of the low-temperature reaction time between 4 and 6 hours can be selected from 4.5 hours, 4.8 hours, 5 hours, 5.2 hours, or 5.5 hours.

[0117] When the reactor is a fluidized bed, as a further preferred embodiment, any point or range of the low-temperature reaction time between 4 and 6 hours can be selected from 4.8 hours, 5 hours, or 5.2 hours.

[0118] When the reactor is a fluidized bed, as a further preferred embodiment, any point or range of the low-temperature reaction time between 4 and 6 hours can be selected from 5.0 hours.

[0119] When the reactor is a fluidized bed, as a further preferred embodiment, the intermediate temperature zone reaction temperature is any point or range between 200-440℃, and can be selected from 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, or 440℃;

[0120] When the reactor is a fluidized bed, as a further preferred embodiment, the intermediate temperature zone reaction temperature is any point or range between 200-440℃, and can be selected from 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃ or 400℃;

[0121] When the reactor is a fluidized bed, as a further preferred embodiment, the reaction temperature in the intermediate temperature range is any point or range between 200-440℃, and can be selected from 300℃, 310℃, 320℃, 330℃, 340℃ or 350℃.

[0122] When the reactor is a fluidized bed, as a further preferred embodiment, the intermediate temperature zone reaction temperature is any point or range between 200-440°C, and can be selected from 300°C.

[0123] When the reactor is a fluidized bed, as a further preferred embodiment, any point or range of the intermediate temperature reaction time between 2 and 4 hours can be selected from 2 hours, 2.2 hours, 2.5 hours, 2.8 hours, 3 hours, 3.2 hours, 3.5 hours, 3.8 hours, or 4.0 hours.

[0124] When the reactor is a fluidized bed, as a further preferred embodiment, any point or range of the reaction time in the intermediate temperature section between 2 and 4 hours can be selected from 2.5 hours, 2.8 hours, 3 hours, 3.2 hours, or 3.5 hours.

[0125] When the reactor is a fluidized bed, as a further preferred embodiment, any point or range of the intermediate temperature reaction time between 2 and 4 hours can be selected from 3 hours, 3.2 hours, or 3.5 hours.

[0126] When the reactor is a fluidized bed, as a further preferred embodiment, any point or range of the intermediate temperature reaction time between 2 and 4 hours can be selected from 3 hours.

[0127] As a preferred embodiment, when the reactor is a fluidized bed, the apparent gas velocity is controlled at 0.35 m / s, the bed temperature uniformity is ±5℃, the low-temperature reaction temperature is 70℃, and the reaction time is 5h; the medium-temperature reaction temperature is 300℃, and the reaction time is 3h.

[0128] The molar ratio of lithium source to sulfur dioxide in step (2) above is 1:1.0-1.2. Preferably, the molar ratio of lithium source to sulfur dioxide is 1:1.05-1.15. More preferably, the molar ratio of lithium source to sulfur dioxide is 1:1.1.

[0129] As a further preferred embodiment, the molar ratio of the lithium source to sulfur dioxide is any point or range between 1:1.0 and 1.2, and can be selected from 1:1, 1:1.02, 1:1.05, 1:1.08, 1:1.1, 1:1.12, 1:1.15, 1:1.18 or 1:1.2;

[0130] As a further preferred embodiment, the molar ratio of the lithium source to sulfur dioxide is any point or range between 1:1.0 and 1.2, and can be selected from 1:1.0, 1:1.05, 1:1.08, 1:1.1, 1:1.12 or 1:1.15;

[0131] As a further preferred embodiment, the molar ratio of the lithium source to sulfur dioxide is any point or range between 1:1.0 and 1.2, and can be selected from 1:1.0, 1:1.12 or 1:1.15;

[0132] As a further preferred embodiment, the molar ratio of the lithium source to sulfur dioxide is any value or range between 1:1.0 and 1.2, and can be selected from 1:1.0;

[0133] That is, measured in Li element, i.e., 1 mol Li₂O or 2 mol LiOH corresponds to 1.0-1.2 mol SO₂.

[0134] The reducing gas mentioned in step (3) above is hydrogen or methane;

[0135] If a rotary kiln with a series reduction section is used, and hydrogen is used as the reducing gas, first purge and replace the reduction section with an inert gas of ≥99.99% purity for 30-60 minutes, ensuring the oxygen content is <100ppm. Then, hydrogen is introduced, controlling the rotary kiln speed at 1-8 r / min and the filling rate at 10-25%. The hydrogen reduction conditions (purity ≥99.9%) are a temperature of 300-450℃ and a gas space velocity of 800-1500 h⁻¹. - ¹Reaction time: 4-7 hours;

[0136] If a rotary kiln with a series reduction section is used, and hydrogen is used as the reducing gas, preferably, an inert gas with a purity ≥99.99% is first introduced into the reduction section for purging and replacement for 40-50 minutes to ensure an oxygen content <100ppm. Then, hydrogen is introduced, and the rotary kiln speed is controlled at 3-6 r / min and the filling rate at 15-20%. The hydrogen reduction conditions (purity ≥99.9%) are a temperature of 350-400℃ and a gas space velocity of 1000-1200 h⁻¹. - ¹Reaction time: 5-6 hours;

[0137] As a further preferred embodiment, the control of the rotary kiln speed at any point or range between 1 and 8 r / min can be selected from 1 r / min, 2 r / min, 3 r / min, 4 r / min, 5 r / min, 6 r / min, 7 r / min or 8 r / min;

[0138] As a further preferred embodiment, the control of the rotary kiln speed at any point or range between 1 and 8 r / min can be selected from 4 r / min, 5 r / min, 6 r / min, 7 r / min or 8 r / min;

[0139] As a further preferred embodiment, the control of the rotary kiln speed at any point or range between 1-8 r / min can be selected from 5 r / min or 6 r / min;

[0140] As a further preferred embodiment, the control of the rotary kiln speed at any point or range between 1-8 r / min can be selected from 5 r / min;

[0141] As a further preferred embodiment, any point or range of the fill rate between 10% and 25% may be selected from 10%, 12%, 14%, 15%, 16%, 18%, 19%, 20%, 22%, 24%, or 25%.

[0142] As a further preferred embodiment, the fill rate is any point or range between 10-25%, and can be selected from 15%, 16%, 18%, 19%, or 20%.

[0143] As a further preferred embodiment, the fill rate is any point or range between 10-25%, and may be selected from 15%, 16% or 18%;

[0144] As a more preferred embodiment, the fill rate is any value or range between 10% and 25%, and may be selected from 15%;

[0145] As a further preferred embodiment, the reaction temperature for hydrogen reduction is any point or range between 300-450℃, and can be selected from 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃ or 450℃;

[0146] As a further preferred embodiment, the reaction temperature for hydrogen reduction is any point or range between 300-450℃, and can be selected from 300℃, 310℃, 320℃, 330℃, 340℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃ or 450℃;

[0147] As a further preferred embodiment, the reaction temperature of the hydrogen reduction is any point or range between 300-450°C, and can be selected from 380°C, 390°C, 400°C or 420°C.

[0148] As a further preferred embodiment, the reaction temperature of the hydrogen reduction is any point or range between 300-450°C, and can be selected from 400°C.

[0149] As a further preferred embodiment, the gas space velocity for hydrogen reduction is 800-1500 h⁻¹. - Any point or range of values ​​between ¹, selectable from 800h -1 900h -1 1000h -1 1100h -1 1200h -1 1300h -1 1400h -1 Or 1500h-1 ;

[0150] As a further preferred embodiment, the gas space velocity for hydrogen reduction is 800-1500 h⁻¹. - Any point or range of values ​​between ¹, selectable from 1000h -1 1100h -1 1200h -1 Or 1300h -1 ;

[0151] As a further preferred embodiment, the gas space velocity for hydrogen reduction is 800-1500 h⁻¹. - Any point or range of values ​​between ¹, selectable from 1100h -1 1200h -1 Or 1300h -1 ;

[0152] As a further preferred embodiment, the gas space velocity for hydrogen reduction is 800-1500 h⁻¹. - Any point or range of values ​​between ¹, selectable from 1200h -1 ;

[0153] As a further preferred embodiment, the reaction time of the hydrogen reduction can be any value or range between 4 and 7 hours, and can be selected from 4 hours, 4.2 hours, 4.5 hours, 4.8 hours, 5 hours, 5.2 hours, 5.5 hours, 5.8 hours, 6.0 hours, 6.2 hours, 6.5 hours, 6.8 hours, or 7.0 hours.

[0154] As a further preferred embodiment, the reaction time for hydrogen reduction can be any value or range between 4 and 7 hours, and can be selected from 5 hours, 5.2 hours, 5.5 hours, 5.8 hours, 6.0 hours, 6.2 hours, or 6.5 hours.

[0155] As a further preferred embodiment, the reaction time for hydrogen reduction can be any value or range between 4 and 7 hours, specifically 5.5 hours, 5.8 hours, or 6.0 hours.

[0156] As a further preferred embodiment, the reaction time for hydrogen reduction can be any value or range between 4 and 7 hours, and can be selected from 6.0 hours.

[0157] As a preferred embodiment, if a rotary kiln with a series reduction section is used, and hydrogen is used as the reducing gas, preferably, an inert gas with a purity ≥99.99% is first introduced into the reduction section for purging and replacement for 45 minutes to ensure that the oxygen content is <100ppm. Subsequently, hydrogen is introduced, and the rotary kiln speed is controlled at 5r / min and the filling rate at 15%. The hydrogen reduction (purity ≥99.9%) conditions are a temperature of 400℃ and a gas space velocity of 1200h⁻¹. - ¹Reaction time: 6 hours.

[0158] If a rotary kiln with a series reduction section is used, and methane is used as the reducing gas, first purge and replace the reduction section with an inert gas of ≥99.99% purity for 30-60 minutes, ensuring the oxygen content is <100ppm. Then, methane (≥99.5% purity) is introduced for reduction under the following conditions: reaction temperature 450-600℃ and gas hourly space velocity 600-1200 h⁻¹. -1 The reaction time is 7-10 hours.

[0159] If a rotary kiln with a series reduction section is used, and methane is used as the reducing gas, preferably, an inert gas with a purity ≥99.99% is first introduced into the reduction section to purge and replace it for 30-60 minutes, ensuring that the oxygen content is <100ppm. Subsequently, methane (purity ≥99.5%) is introduced for reduction, under the following conditions: reaction temperature 500-550℃ and gas space velocity 800-1000h. -1 The reaction time is 8-9 hours.

[0160] As a further preferred embodiment, the reaction temperature for methane reduction is any point or range between 450-600℃, and can be selected from 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃;

[0161] As a further preferred embodiment, the reaction temperature for methane reduction is any point or range between 450-600℃, and can be selected from 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃.

[0162] As a further preferred embodiment, the reaction temperature for methane reduction is any point or range between 450-600℃, and can be selected from 520℃, 530℃, 540℃, 550℃ or 560℃.

[0163] As a more preferred embodiment, the reaction temperature for methane reduction is any point or range between 450-600°C, and may be selected from 550°C.

[0164] As a further preferred embodiment, the gas hourly space velocity (GHV) for methane reduction is 600-1200 h⁻¹. -1 Any point or range of values ​​between 600h -1 700h -1 800h -1 900h -1 1000h -1 1100h -1 or 1200h-1 ;

[0165] As a further preferred embodiment, the gas space velocity for methane reduction is 600-1200 h⁻¹. -1 Any point or range of values ​​between 800h -1 900h -1 1000h -1 1100h -1 or 1200h -1 ;

[0166] As a further preferred embodiment, the gas hourly space velocity (GHSV) for methane reduction is 600-1200 h⁻¹. -1 Any point or range of values ​​between 800h -1 900h -1 or 1000h -1 ;

[0167] As a further preferred embodiment, the gas hourly space velocity (GHV) for methane reduction is 600-1200 h⁻¹. -1 Any point or range of values ​​between 1000h -1 ;

[0168] As a further preferred embodiment, the reaction time for methane reduction is any value or range between 7 and 10 hours, and can be selected from 7 hours, 7.2 hours, 7.5 hours, 7.8 hours, 8 hours, 8.2 hours, 8.5 hours, 8.8 hours, 9.0 hours, 9.2 hours, 9.5 hours, 9.8 hours, or 10.0 hours.

[0169] As a further preferred embodiment, the reaction time for methane reduction is any value or range between 7 and 10 hours, and can be selected from 8 hours, 8.2 hours, 8.5 hours, 8.8 hours, 9.0 hours, 9.2 hours, or 9.5 hours.

[0170] As a further preferred embodiment, the reaction time for methane reduction is any value or range between 7 and 10 hours, and can be selected from 8.5 hours, 8.8 hours, or 9.0 hours.

[0171] As a further preferred embodiment, the reaction time for methane reduction is any value or range between 7 and 10 hours, and may be selected from 9.0 hours.

[0172] As a preferred embodiment, if a rotary kiln with a series reduction section is used, and methane is used as the reducing gas, the reduction section is first purged and replaced with an inert gas of ≥99.99% purity for 50 minutes to ensure that the oxygen content is <100ppm. Then, methane (≥99.5% purity) is introduced for reduction under the following conditions: reaction temperature 550℃ and gas space velocity 1000h⁻¹. -1 The reaction time is 9 hours.

[0173] If a fluidized bed integrated synthesis-reduction method is adopted, hydrogen is used as the reducing gas. First, the bed is replaced with an inert gas for 20-40 minutes, and then hydrogen is switched to control the apparent gas velocity at 0.1-0.6 m / s, the reduction temperature at 300-450℃, and the reaction time at 3-6 h.

[0174] If a fluidized bed integrated synthesis-reduction method is adopted, with hydrogen as the reducing gas, preferably, the bed is first replaced with an inert gas for 20-40 minutes, and then switched to hydrogen, with the apparent gas velocity controlled at 0.2-0.5 m / s, the reduction temperature at 350-400℃, and the reaction time at 4-5 h.

[0175] As a further preferred embodiment, the apparent gas velocity for hydrogen reduction, any point or range between 0.1 and 0.6 m / s, can be selected from 0.1 m / s, 0.12 m / s, 0.14 m / s, 0.15 m / s, 0.18 m / s, 0.2 m / s, 0.22 m / s, 0.25 m / s, 0.28 m / s, 0.30 m / s, 0.32 m / s, 0.35 m / s, 0.38 m / s, 0.4 m / s, 0.42 m / s, 0.45 m / s, 0.48 m / s, 0.5 m / s, 0.52 m / s, 0.55 m / s, or 0.6 m / s;

[0176] As a further preferred embodiment, the apparent gas velocity for hydrogen reduction, any point or range between 0.1 and 0.6 m / s, can be selected from 0.2 m / s, 0.22 m / s, 0.25 m / s, 0.28 m / s, 0.30 m / s, 0.32 m / s, 0.35 m / s, 0.38 m / s, 0.4 m / s, 0.42 m / s, 0.45 m / s, 0.48 m / s, or 0.5 m / s;

[0177] As a further preferred embodiment, the apparent gas velocity for hydrogen reduction, any point or range between 0.1 and 0.6 m / s, may be selected from 0.30 m / s, 0.32 m / s, 0.35 m / s, 0.38 m / s, 0.4 m / s, 0.42 m / s, or 0.45 m / s;

[0178] As a further preferred embodiment, the apparent gas velocity for hydrogen reduction is any point or range between 0.1 and 0.6 m / s, and may be selected from 0.4 m / s.

[0179] As a further preferred embodiment, the reaction temperature of the hydrogen reduction is any point or range between 300-450℃, and can be selected from 300℃, 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃ or 450℃.

[0180] As a further preferred embodiment, the reaction temperature of the hydrogen reduction is any point or range between 300-450℃, and can be selected from 350℃, 360℃, 370℃, 380℃, 390℃, 400℃ or 420℃.

[0181] As a further preferred embodiment, the reaction temperature of the hydrogen reduction is any point or range between 300-450°C, and can be selected from 400°C or 420°C.

[0182] As a further preferred embodiment, the reaction temperature for hydrogen reduction is any point or range between 300-450°C, and can be selected from 400°C.

[0183] As a further preferred embodiment, the reaction time for hydrogen reduction is any value or range between 3 and 6 hours, and can be selected from 3 hours, 3.2 hours, 3.5 hours, 3.8 hours, 4 hours, 4.2 hours, 4.5 hours, 4.8 hours, 5.0 hours, 5.2 hours, 5.5 hours, 5.8 hours, or 6.0 hours.

[0184] As a further preferred embodiment, the reaction time for hydrogen reduction is any value or range between 3 and 6 hours, and can be selected from 4 hours, 4.2 hours, 4.5 hours, 4.8 hours, 5.0 hours, 5.2 hours, or 5.5 hours.

[0185] As a further preferred embodiment, the reaction time for hydrogen reduction is any value or range between 3 and 6 hours, and can be selected from 4.5 hours, 4.8 hours, or 5.0 hours.

[0186] As a further preferred embodiment, the reaction time for hydrogen reduction is any value or range between 3 and 6 hours, and can be selected from 4.5 hours.

[0187] As a preferred embodiment, if a fluidized bed integrated synthesis-reduction is adopted, with hydrogen as the reducing gas, preferably, the bed is first replaced with an inert gas for 30 minutes, and then switched to hydrogen, with the apparent gas velocity controlled at 0.4 m / s, the reduction temperature at 400℃ and the reaction time at 4.5 h.

[0188] If a fluidized bed integrated synthesis-reduction method is adopted, with methane as the reducing gas, the bed is first replaced by an inert gas for 20-40 minutes, and then switched to methane. The reaction temperature for methane reduction is 450-600℃ and the reaction time is 6-9 hours.

[0189] If a fluidized bed integrated synthesis-reduction method is adopted, with methane as the reducing gas, preferably, the bed is first replaced with an inert gas for 20-40 minutes, and then switched to methane. The reaction temperature for methane reduction is 500-550℃ and the reaction time is 7-8 hours.

[0190] As a further preferred embodiment, the reaction temperature for methane reduction is any point or range between 450-600℃, and can be selected from 450℃, 460℃, 470℃, 480℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃;

[0191] As a further preferred embodiment, the reaction temperature for methane reduction is any point or range between 450-600℃, and can be selected from 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃ or 600℃.

[0192] As a further preferred embodiment, the reaction temperature for methane reduction is any point or range between 450-600℃, and can be selected from 500℃, 510℃, 520℃, 530℃, 540℃ or 550℃.

[0193] As a further preferred embodiment, the reaction temperature for methane reduction is any point or range between 450-600°C, and may be selected from 550°C.

[0194] As a further preferred embodiment, the reaction time for methane reduction is any value or range between 6 and 9 hours, specifically 6 hours, 6.2 hours, 6.5 hours, 6.8 hours, 7 hours, 7.2 hours, 7.5 hours, 7.8 hours, 8.0 hours, 8.2 hours, 8.5 hours, 8.8 hours, or 9.0 hours.

[0195] As a further preferred embodiment, the reaction time for methane reduction is any value or range between 6 and 9 hours, specifically 7 hours, 7.2 hours, 7.5 hours, 7.8 hours, or 8.0 hours.

[0196] As a further preferred embodiment, the reaction time for methane reduction is any value or range between 6 and 9 hours, and can be selected from 7.5 hours, 7.8 hours, or 8.0 hours.

[0197] As a further preferred embodiment, the reaction time for methane reduction is any value or range between 6 and 9 hours, and may be selected from 7.5 hours.

[0198] As a preferred embodiment, if a fluidized bed integrated synthesis-reduction is adopted, with methane as the reducing gas, the bed is first replaced by an inert gas for 30 minutes, and then switched to methane. The reaction temperature for methane reduction is 550°C and the reaction time is 7.5 hours.

[0199] The airflow pulverization process parameters mentioned in step (4) above are: inlet pressure of 0.7-1.0MPa, feed rate of 10-30kg / h, and classifier speed of 20000-30000r / min, to ensure that the particle size D50 of lithium sulfide product is controlled within 3μm;

[0200] Preferably, the airflow pulverization process parameters are: inlet pressure of 0.8-1.0 MPa, feed rate of 15-25 kg / h, and classifier rotation speed of 22000-28000 r / min, to ensure that the particle size D50 of lithium sulfide product is controlled within 3 μm;

[0201] As a further preferred embodiment, the inlet pressure of the airflow pulverizer is any value or range between 0.7 and 1.0 MPa, and can be selected from 0.7 MPa, 0.72 MPa, 0.75 MPa, 0.78 MPa, 0.80 MPa, 0.82 MPa, 0.85 MPa, 0.88 MPa, 0.90 MPa, 0.92 MPa, 0.95 MPa, 0.98 MPa or 1.0 MPa;

[0202] As a further preferred embodiment, the inlet pressure of the airflow pulverizer is any point or range between 0.7 and 1.0 MPa, and can be selected from 0.80 MPa, 0.82 MPa, 0.85 MPa, 0.88 MPa, 0.90 MPa, 0.92 MPa or 0.95 MPa;

[0203] As a further preferred embodiment, the inlet pressure of the airflow pulverizer is any value or range between 0.7 and 1.0 MPa, and can be selected from 0.85 MPa, 0.88 MPa or 0.90 MPa;

[0204] As a further preferred embodiment, the inlet pressure of the airflow pulverizer is any value or range between 0.7 and 1.0 MPa, and can be selected from 0.90 MPa.

[0205] As a further preferred embodiment, the feed rate of the airflow pulverizer is any value or range between 10-30 kg / h, and can be selected from 10 kg / h, 11 kg / h, 12 kg / h, 13 kg / h, 14 kg / h, 15 kg / h, 16 kg / h, 17 kg / h, 18 kg / h, 19 kg / h, 20 kg / h, 21 kg / h, 22 kg / h, 23 kg / h, 24 kg / h, 25 kg / h, 26 kg / h, 27 kg / h, 28 kg / h, 29 kg / h or 30 kg / h;

[0206] As a further preferred embodiment, the feed rate of the airflow pulverizer is any value or range between 10-30 kg / h, and can be selected from 15 kg / h, 16 kg / h, 17 kg / h, 18 kg / h, 19 kg / h, 20 kg / h, 21 kg / h, 22 kg / h, 23 kg / h, 24 kg / h or 25 kg / h;

[0207] As a further preferred embodiment, the feed rate of the air jet mill is any value or range between 10-30 kg / h, and can be selected from 18 kg / h, 19 kg / h, 20 kg / h, 21 kg / h or 22 kg / h;

[0208] As a further preferred embodiment, the feed rate of the air jet mill is any value or range between 10-30 kg / h, and can be selected from 20 kg / h.

[0209] As a further preferred embodiment, the speed of the classifying wheel in the airflow pulverizer is any point or range between 20,000 and 30,000 r / min, and can be selected from 20,000 r / min, 21,000 r / min, 22,000 r / min, 23,000 r / min, 24,000 r / min, 25,000 r / min, 26,000 r / min, 27,000 r / min, 28,000 r / min, 29,000 r / min or 30,000 r / min;

[0210] As a further preferred embodiment, the speed of the classifying wheel in the airflow pulverizer is any point or range between 20,000 and 30,000 r / min, and can be selected from 22,000 r / min, 23,000 r / min, 24,000 r / min, 25,000 r / min, 26,000 r / min, 27,000 r / min or 28,000 r / min;

[0211] As a further preferred embodiment, the speed of the classifying wheel in the airflow pulverizer is any point or range between 20,000 and 30,000 r / min, and can be selected from 24,000 r / min, 25,000 r / min or 26,000 r / min;

[0212] As a further preferred embodiment, the speed of the classifying wheel in the air jet mill is any point or range between 20,000 and 30,000 r / min, and can be selected from 25,000 r / min.

[0213] As a preferred embodiment, the airflow pulverization process parameters are: inlet pressure of 0.9 MPa, feed rate of 20 kg / h, and classifier rotation speed of 25000 r / min, to ensure that the particle size D50 of lithium sulfide product is controlled within 3 μm.

[0214] The inert gas mentioned in step (3) above is nitrogen or argon.

[0215] The vacuum drying process described in step (4) above involves a drying temperature of 80-120℃, a vacuum degree of -0.08~-0.1MPa, and a drying time of 3-6h.

[0216] Preferably, the vacuum drying process involves a drying temperature of 100-120℃, a vacuum degree of -0.08 to -0.09 MPa, and a drying time of 4-5 hours.

[0217] As a further preferred embodiment, the drying temperature of the vacuum drying is any point or range between 80-120℃, which can be selected from 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃ or 120℃.

[0218] As a further preferred embodiment, the drying temperature of the vacuum drying is any point or range between 80-120°C, and can be selected from 90°C, 95°C, 100°C, 105°C or 110°C.

[0219] As a further preferred embodiment, the drying temperature of the vacuum drying is any point or range between 80-120°C, which may be selected from 95°C, 100°C or 105°C.

[0220] As a further preferred embodiment, the drying temperature of the vacuum drying is any point or range between 80-120°C, and can be selected from 100°C.

[0221] As a further preferred embodiment, the vacuum degree of the vacuum drying is any point or range value between -0.08 and -0.1 MPa, and can be selected from -0.08 MPa, -0.085 MPa, -0.09 MPa, -0.095 MPa or -1.0 MPa;

[0222] As a further preferred embodiment, the vacuum degree of the vacuum drying is any point or range value between -0.08 and -0.1 MPa, and can be selected from -0.09 MPa, -0.095 MPa or -1.0 MPa;

[0223] As a further preferred embodiment, the vacuum degree of the vacuum drying is any point or range between -0.08 and -0.1 MPa, and can be selected from -0.09 MPa;

[0224] As a further preferred embodiment, the drying time of the vacuum drying is any value or range between 3 and 6 hours, and can be selected from 3 hours, 3.2 hours, 3.5 hours, 3.8 hours, 4.0 hours, 4.2 hours, 4.5 hours, 4.8 hours, 5.0 hours, 5.2 hours, 5.5 hours, 5.8 hours or 6 hours;

[0225] As a further preferred embodiment, the drying time of the vacuum drying is any value or range between 3 and 6 hours, and can be selected from 4.0 hours, 4.2 hours, 4.5 hours, 4.8 hours or 5.0 hours;

[0226] As a further preferred embodiment, the drying time of the vacuum drying is any value or range between 3 and 6 hours, and can be selected from 4.5 hours, 4.8 hours or 5.0 hours;

[0227] As a further preferred embodiment, the drying time of the vacuum drying is any value or range between 3 and 6 hours, and can be selected from 4.5 hours.

[0228] As a preferred embodiment, the vacuum drying in step (4) is performed at a drying temperature of 100°C, a vacuum degree of -0.09 MPa, and a drying time of 4.5 h.

[0229] As some preferred embodiments, the preparation method includes the following steps:

[0230] (1) Pretreatment of lithium source: The anhydrous lithium hydroxide was vacuum dried at a temperature of 200-430℃, a vacuum degree of -0.05~-0.08MPa, and a drying time of 2-3h to obtain the pretreated lithium source;

[0231] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source is fed into a rotary kiln, and sulfur dioxide gas with a purity of ≥99.5% is introduced for reaction. The rotation speed is controlled at 1-10 r / min, the filling rate is 10-30%, the reaction temperature in the low-temperature section is 50-80℃, and the reaction conditions are gas space velocity of 500-1000 h⁻¹. -1 The reaction time is 6-8 hours; the reaction temperature in the mesophilic range is 100-320℃, and the reaction conditions are a gas space velocity of 1000-2000 h⁻¹. -1 The reaction time is 3-6 hours to produce lithium sulfite intermediate;

[0232] (3) Lithium sulfide preparation: First, nitrogen gas with a purity of ≥99.99% is introduced into the reduction section for purging and replacement for 45 min to ensure that the oxygen content is <100 ppm. Then, hydrogen gas is introduced to react with the lithium sulfite intermediate. The rotary kiln speed is controlled at 1-8 r / min and the filling rate is 10-25%. The hydrogen reduction conditions are a temperature of 300-450℃ and a gas space velocity of 800-1500 h⁻¹. - ¹ The reaction time is 4-7 hours, and crude lithium sulfide is obtained.

[0233] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.7-1.0 MPa inlet pressure, 10-30 kg / h feed rate and 20000-30000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 80-120℃, vacuum degree of -0.08~-0.1 MPa and drying time of 3-6 h to obtain the finished lithium sulfide product.

[0234] In some other preferred embodiments, the preparation method includes the following steps:

[0235] (1) Pretreatment of lithium source: The anhydrous lithium hydroxide was vacuum dried at a temperature of 200-430℃, a vacuum degree of -0.05~-0.08MPa, and a drying time of 2-3h to obtain the pretreated lithium source;

[0236] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source is fed into a rotary kiln, and sulfur dioxide gas with a purity of ≥99.5% is introduced for reaction. The rotation speed is controlled at 1-10 r / min, the filling rate is 10-30%, the reaction temperature in the low-temperature section is 50-80℃, and the reaction conditions are gas space velocity of 500-1000 h⁻¹. -1 The reaction time is 6-8 hours; the reaction temperature in the mesophilic range is 100-320℃, and the reaction conditions are a gas space velocity of 1000-2000 h⁻¹. -1 The reaction time is 3-6 hours to produce lithium sulfite intermediate;

[0237] (3) Lithium sulfide preparation: First, nitrogen gas with a purity of ≥99.99% is introduced into the reduction section for purging and replacement for 45 min to ensure that the oxygen content is <100 ppm. Then, methane is introduced to react with the lithium sulfite intermediate under the following conditions: reaction temperature of 450-600℃ and gas space velocity of 600-1200 h⁻¹. -1 The reaction time is 7-10 hours, and crude lithium sulfide is obtained.

[0238] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.7-1.0 MPa inlet pressure, 10-30 kg / h feed rate and 20000-30000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 80-120℃, vacuum degree of -0.08~-0.1 MPa and drying time of 3-6 h to obtain the finished lithium sulfide product.

[0239] In some further preferred embodiments, the preparation method includes the following steps:

[0240] (1) Lithium source pretreatment: The drying temperature of lithium oxide is 120-160℃, the vacuum degree is -0.05~-0.08MPa, and the drying time is 2-4h to obtain the pretreated lithium source;

[0241] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source is fed into a rotary kiln, and sulfur dioxide gas with a purity of ≥99.5% is introduced for reaction. The rotation speed is controlled at 1-10 r / min, the filling rate is 10-30%, the reaction temperature in the low-temperature section is 50-80℃, and the reaction conditions are gas space velocity of 500-1000 h⁻¹. -1 The reaction time is 6-8 hours; the reaction temperature in the mesophilic range is 100-320℃, and the reaction conditions are a gas space velocity of 1000-2000 h⁻¹. -1 The reaction time is 3-6 hours to produce lithium sulfite intermediate;

[0242] (3) Lithium sulfide preparation: First, nitrogen gas with a purity of ≥99.99% is introduced into the reduction section for purging and replacement for 45 min to ensure that the oxygen content is <100 ppm. Then, hydrogen gas is introduced to react with the lithium sulfite intermediate. The rotary kiln speed is controlled at 1-8 r / min and the filling rate is 10-25%. The hydrogen reduction conditions are a temperature of 300-450℃ and a gas space velocity of 800-1500 h⁻¹. - ¹ The reaction time is 4-7 hours, and crude lithium sulfide is obtained.

[0243] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.7-1.0 MPa inlet pressure, 10-30 kg / h feed rate and 20000-30000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 80-120℃, vacuum degree of -0.08~-0.1 MPa and drying time of 3-6 h to obtain the finished lithium sulfide product.

[0244] In some further preferred embodiments, the preparation method includes the following steps:

[0245] (1) Lithium source pretreatment: The drying temperature of lithium oxide is 120-160℃, the vacuum degree is -0.05~-0.08MPa, and the drying time is 2-4h to obtain the pretreated lithium source;

[0246] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source is fed into a rotary kiln, and sulfur dioxide gas with a purity of ≥99.5% is introduced for reaction. The rotation speed is controlled at 1-10 r / min, the filling rate is 10-30%, the reaction temperature in the low-temperature section is 50-80℃, and the reaction conditions are gas space velocity of 500-1000 h⁻¹. -1The reaction time is 6-8 hours; the reaction temperature in the mesophilic range is 100-320℃, and the reaction conditions are a gas space velocity of 1000-2000 h⁻¹. -1 The reaction time is 3-6 hours to produce lithium sulfite intermediate;

[0247] (3) Lithium sulfide preparation: First, nitrogen gas with a purity of ≥99.99% is introduced into the reduction section for purging and replacement for 45 min to ensure that the oxygen content is <100 ppm. Then, methane is introduced to react with the lithium sulfite intermediate under the following conditions: reaction temperature of 450-600℃ and gas space velocity of 600-1200 h⁻¹. -1 The reaction time is 7-10 hours, and crude lithium sulfide is obtained.

[0248] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.7-1.0 MPa inlet pressure, 10-30 kg / h feed rate and 20000-30000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 80-120℃, vacuum degree of -0.08~-0.1 MPa and drying time of 3-6 h to obtain the finished lithium sulfide product.

[0249] In some further embodiments, the preparation method includes the following steps:

[0250] (1) Pretreatment of lithium source: The anhydrous lithium hydroxide was vacuum dried at a temperature of 200-430℃, a vacuum degree of -0.05~-0.08MPa, and a drying time of 2-3h to obtain the pretreated lithium source;

[0251] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source is fed into a fluidized bed and sulfur dioxide gas with a purity of ≥99.5% is introduced for reaction. The apparent gas velocity is controlled at 0.1-0.5 m / s and the bed temperature uniformity is ±5℃. The reaction temperature in the low temperature section is 50-80℃ and the reaction time is 4-6h; the reaction temperature in the medium temperature section is 200-440℃ and the reaction time is 2-4h to produce lithium sulfite intermediate.

[0252] (3) Preparation of lithium sulfide: First, the bed is replaced with nitrogen for 20-40 min, then switch to hydrogen, control the apparent gas velocity at 0.1-0.6 m / s, reduce the temperature at 300-450℃ and react for 3-6 h to obtain crude lithium sulfide.

[0253] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.7-1.0 MPa inlet pressure, 10-30 kg / h feed rate and 20000-30000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 80-120℃, vacuum degree of -0.08~-0.1 MPa and drying time of 3-6 h to obtain the finished lithium sulfide product.

[0254] In some further preferred embodiments, the preparation method includes the following steps:

[0255] (1) Pretreatment of lithium source: The drying temperature of lithium oxide by vacuum drying to remove water is 120-160℃, the vacuum degree is -0.05~-0.08MPa, and the drying time is 2-4h to obtain the pretreated lithium source;

[0256] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source is fed into a fluidized bed and sulfur dioxide gas with a purity of ≥99.5% is introduced for reaction. The apparent gas velocity is controlled at 0.1-0.5 m / s and the bed temperature uniformity is ±5℃. The reaction temperature in the low temperature section is 50-80℃ and the reaction time is 4-6h; the reaction temperature in the medium temperature section is 200-440℃ and the reaction time is 2-4h to produce lithium sulfite intermediate.

[0257] (3) Preparation of lithium sulfide: First, the bed is replaced with nitrogen for 20-40 min, then switch to hydrogen, control the apparent gas velocity at 0.1-0.6 m / s, reduce the temperature at 300-450℃ and react for 3-6 h to obtain crude lithium sulfide.

[0258] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.7-1.0 MPa inlet pressure, 10-30 kg / h feed rate and 20000-30000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 80-120℃, vacuum degree of -0.08~-0.1 MPa and drying time of 3-6 h to obtain the finished lithium sulfide product.

[0259] The mechanism of the above reaction is as follows:

[0260] When the lithium source is lithium hydroxide, it reacts with sulfur dioxide in an acid-base neutralization reaction to produce lithium sulfite. The reaction equation is shown in equation (1).

[0261] 2LiOH + SO2= Li2SO3+ H2O Formula (1)

[0262] When the lithium source is lithium oxide, it reacts with sulfur dioxide to form lithium sulfite, and the reaction equation is shown in equation (2).

[0263] Li2O + SO2 = Li2SO3 (Equation 2)

[0264] The generated lithium sulfite is then reduced by hydrogen to form lithium sulfide, and the reaction equation is shown in equation (3):

[0265] Li2SO3 + 3H2 = Li2S + 3H2O Equation (3)

[0266] The generated lithium sulfite is then reduced by methane to produce lithium sulfide, and the reaction equation is shown in equation (4):

[0267] 2Li2SO3 + CH4 = 2Li2S + CO2 + 2H2O Equation (4)

[0268] Secondly, the present invention provides: a lithium sulfide prepared by the above method, wherein the lithium sulfide has a purity ≥99.9%, a carbon content ≤0.1%, and a particle size D50 ≤3μm.

[0269] Thirdly, the present invention provides the application of lithium sulfide prepared by the above method in the preparation of lithium-sulfur batteries or semiconductor electronic materials.

[0270] Examples 1-11 of this invention at least support the protection scope of the lithium source, reducing agent, and reactor.

[0271] The term "lithium source" is derived from the common feature "lithium source" in the foregoing explanation and / or the corresponding technical features such as anhydrous lithium hydroxide and lithium oxide in Examples 1-11. Therefore, those skilled in the art can reasonably infer that the subordinate concepts of the technical features containing lithium compounds, substantially equivalent technical means, and technical means that can replace anhydrous lithium hydroxide and lithium oxide based on existing technology and conventional technical means and common knowledge should all fall within the scope of protection of this invention. For example, replacing the lithium source with lithium carbonate while keeping other technical features unchanged still falls within the scope of protection of this invention.

[0272] The term "reducing agent" is derived from the aforementioned explanations and / or the corresponding technical features of hydrogen, methane, etc., in Examples 1-11, using the common feature "reducing agent." Therefore, those skilled in the art can reasonably infer that the subordinate concept of the technical feature "reducing gas," substantially equivalent technical means, and technical means that can replace hydrogen or methane within the scope of conventional technical means and common knowledge based on the existing technical level should all fall within the protection scope of this invention. For example, replacing the reducing agent with carbon monoxide, etc., while keeping other technical features unchanged, still falls within the protection scope of this invention.

[0273] The term "reactor" is derived from the common feature "reactor" in the foregoing explanation and / or examples 1-11, such as rotary kilns and fluidized beds. Therefore, those skilled in the art can reasonably infer that the subordinate concept of the technical feature "reactor," the substantially equivalent technical means, and the technical means that can replace rotary kilns and fluidized beds based on existing technology and conventional technical means and common knowledge should all fall within the scope of protection of this invention. For example, replacing the reactor with a microtube reactor while keeping other technical features unchanged still falls within the scope of protection of this invention.

[0274] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0275] 1) Raw material system optimization: Lithium hydroxide or lithium oxide is used as the lithium source, combined with sulfur dioxide and hydrogen / methane as raw materials. All of these are basic chemical raw materials that are available on an industrial scale, with stable sources and low costs. When lithium oxide is used as the lithium source, it has the additional advantages of low initial water content and simplified pretreatment process, which can further reduce production costs.

[0276] 2) Mild and controllable reaction conditions suitable for large-scale production: The temperature of lithium sulfite synthesis stage is only 50-440℃, and the temperature of reduction stage is 300-600℃, both significantly lower than that of carbothermal reduction method; using rotary kiln or fluidized bed reactor, no high pressure environment is required (atmospheric pressure or slight positive pressure is sufficient), which is more suitable for continuous large-scale production. Reaction parameters (temperature, gas velocity, rotation speed, etc.) are easy to control precisely, and the difficulty of industrial scale-up is low.

[0277] 3) High environmental protection and safety: The entire process avoids the use of highly toxic hydrogen sulfide gas and highly active lithium metal, and there is no emission of toxic and harmful gases during the reaction process; the amount of solid waste is low, which meets the requirements of green chemical production and significantly reduces the operational safety risks.

[0278] 4) Excellent product quality: By precisely controlling the lithium source pretreatment, reaction parameters and post-processing (air jet milling + vacuum drying), the product purity can be stably controlled at over 99.9%, carbon content ≤0.1%, and particle size D50≤3μm without washing. The particles have regular morphology and good dispersibility. They can meet the stringent requirements of all-solid-state batteries (especially sulfide-based solid electrolytes) for material purity, carbon content and particle size without additional purification. At the same time, they can also adapt to the application needs of other high-end fields such as lithium-sulfur batteries. Attached Figure Description

[0279] Figure 1 SEM image of lithium sulfide prepared in Example 7;

[0280] Figure 2 XPS plot of lithium sulfide prepared in Example 7;

[0281] Figure 3The image shows the XRD pattern of lithium sulfide prepared in Example 7. Detailed Implementation

[0282] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0283] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all instruments, devices, equipment, reagents, products, etc., used in the embodiments of the present invention are obtained through conventional commercial means.

[0284] Example 1: A method for preparing lithium sulfide

[0285] Lithium sulfide was prepared using anhydrous lithium hydroxide as the lithium source and hydrogen as the reducing agent in a medium-temperature system. The specific steps are as follows:

[0286] 1) Lithium source pretreatment: Take 24.0g (1.0mol) of anhydrous lithium hydroxide powder with a purity of 99%, place it in a vacuum drying oven, control the vacuum degree to -0.06MPa and the drying temperature to 220℃, and dry for 3h to remove free water to obtain pretreated anhydrous lithium hydroxide;

[0287] 2) Lithium sulfite synthesis: Pretreated anhydrous lithium hydroxide is continuously fed into a rotary kiln reactor (5 r / min, 20% filling rate), and sulfur dioxide gas with a purity of 99.8% is introduced, with the sulfur dioxide gas space velocity controlled at 1500 h⁻¹. - ¹, The molar ratio of lithium hydroxide to sulfur dioxide is 2:1.1 (measured in terms of Li element), the reaction temperature is maintained at 200℃ (medium temperature range), the operation is carried out at atmospheric pressure, and the reaction is carried out at a constant temperature for 4 hours to generate lithium sulfite intermediate.

[0288] 3) Lithium sulfite reduction: Lithium sulfite enters the subsequent reduction section as the rotary kiln rotates (3 r / min, 15% filling rate). First, 99.99% pure nitrogen is introduced to purge and replace the lithium sulfite for 40 min (ensuring oxygen content <100 ppm). Then, 99.9% pure hydrogen is introduced, and the hydrogen gas space velocity is controlled at 1200 h⁻¹. - ¹, After heating to 200℃ at a rate of 9℃ / min, switch to heating to 400℃ at a rate of 6℃ / min, maintain atmospheric pressure and constant temperature for 5h (constant temperature fluctuation ≤±3℃), lithium sulfite is reduced to lithium sulfide.

[0289] 4) Post-processing of the product: After the reaction is completed, the product is naturally cooled to room temperature. The product is then subjected to air jet milling with the inlet pressure controlled at 0.8 MPa, the feed rate at 20 kg / h, and the classifier speed at 25,000 r / min. The particle size D50 after milling is 2.8 μm. The product is then placed directly in a vacuum drying oven with the drying temperature controlled at 120℃ and the vacuum degree at -0.1 MPa for 3 hours to obtain 21.6 g of lithium sulfide product.

[0290] The product was tested and found to have a purity of 99.90% and a carbon content of 0.09%.

[0291] The characterization data are as follows:

[0292] (1) Scanning electron microscopy (SEM) analysis: The product is a uniform spherical particle with excellent dispersibility, no agglomeration, smooth and dense surface, and an average particle size of 2.8 μm;

[0293] (2) X-ray diffraction (XRD) analysis (Cu Kα radiation, 2θ=10°-80°): The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks and excellent crystallinity;

[0294] (3) X-ray photoelectron spectroscopy (XPS) analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, corresponding to S 2- Characteristic peaks were observed, and no impurity sulfur species or excess carbon were detected.

[0295] (4) Particle size analysis: D50=2.8μm, particle size distribution range 0.9-5.1μm, which fully meets the control requirements within 3μm;

[0296] (5) Carbon content analysis: The carbon content was detected by an elemental analyzer and was 0.09%, which meets the control standard of ≤0.1%, proving that low carbon content control can be achieved without washing.

[0297] Example 2: A method for preparing lithium sulfide

[0298] Lithium sulfide was prepared using anhydrous lithium hydroxide as the lithium source and hydrogen as the reducing agent in a low-temperature system. The specific steps are as follows:

[0299] 1) Pretreatment: Take 16.8g (0.7mol) of anhydrous lithium hydroxide (powder) with a purity of 99%, place it in a vacuum drying oven, control the vacuum degree to -0.06MPa, and dry it at 220℃ for 3h to remove moisture;

[0300] 2) First stage reaction: The dried lithium hydroxide is fed into a fluidized bed reactor, sealed, and then sulfur dioxide gas with a purity of 99.8% is introduced. The apparent gas velocity of sulfur dioxide gas is controlled at 0.3 m / s, the bed temperature is 100℃ (medium temperature system), and the operation is at atmospheric pressure. The molar ratio of lithium hydroxide to sulfur dioxide is 2:1.1, and the reaction time is 4 h to generate lithium sulfite intermediate.

[0301] 3) Second stage reaction: Stop the introduction of sulfur dioxide, introduce nitrogen gas with a purity of 99.99% into the fluidized bed reactor to replace the bed for 30 min (apparent gas velocity 0.2 m / s); then introduce hydrogen gas with a purity of 99.9% as a reducing gas, control the apparent gas velocity of hydrogen to 0.35 m / s, and raise the temperature to 200℃ at a rate of 9℃ / min, then switch to a rate of 6℃ / min to raise the temperature to 400℃, and react at a constant temperature under normal pressure for 5 h (temperature fluctuation ≤ ±3℃).

[0302] 4) Post-processing: After the reaction is completed, the product is naturally cooled to room temperature. The product is then subjected to air jet milling with the inlet pressure controlled at 0.7 MPa, the feed rate at 15 kg / h, and the classifier speed at 22000 r / min. The particle size D50 after milling is 2.5 μm. The filter cake is then placed directly in a vacuum drying oven and dried at 100℃ and -0.09 MPa for 4 h to obtain 15.3 g of lithium sulfide product.

[0303] The product was tested and found to have a purity of 99.95% and a carbon content of 0.06%.

[0304] Product characterization data:

[0305] (1) XRD analysis (Cu Kα radiation, 2θ=10°-80°): The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks and excellent crystallinity;

[0306] (2) XPS analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, corresponding to S 2- Characteristic peaks, SO3² not detected - SO4² - Impurities and excess carbon;

[0307] (3) Particle size analysis: D50 = 2.5 μm, distribution range 0.8-5.2 μm, which meets the control requirements within 3 μm;

[0308] (4) SEM analysis: The product is a spherical particle with good dispersibility, no obvious agglomeration, smooth surface and regular crystal morphology;

[0309] (5) Carbon content analysis: The elemental analyzer detected 0.06%, which is lower than the control limit of 0.1%.

[0310] Example 3: A method for preparing lithium sulfide

[0311] The preparation of lithium sulfide using lithium hydroxide, sulfur dioxide, and hydrogen as raw materials includes the following steps:

[0312] 1) Pretreatment: Take 24g (1.0mol) of anhydrous lithium hydroxide (granular) with a purity of 99%, place it in a vacuum drying oven, control the vacuum degree to -0.05MPa, and dry at 310℃ for 2.5h to remove moisture;

[0313] 2) First stage reaction: The dried lithium hydroxide was placed in a high-pressure reactor, sealed, and stirred (stirring speed 180 r / min). Sulfur dioxide gas with a purity of 99.8% was introduced, and the sulfur dioxide introduction rate was controlled at 0.8 L / (h·mol lithium hydroxide). The molar ratio of lithium hydroxide to sulfur dioxide was 2:1.05. The reaction temperature was controlled at 60℃ (low temperature system), the reaction pressure was 0.15 MPa, and the reaction time was 7 h, to generate lithium sulfite intermediate.

[0314] 3) Second stage reaction: Stop the introduction of sulfur dioxide, and introduce nitrogen gas with a purity of 99.99% into the reactor to replace the residual gas. The nitrogen introduction rate is 0.25 L / min, and the replacement time is 25 min. Then, introduce hydrogen gas with a purity of 99.9% as a reducing gas, and control the hydrogen introduction rate at 1.5 L / (h·mol lithium sulfite). Increase the temperature to 200℃ at a rate of 10℃ / min, and then switch to a rate of 7℃ / min to increase the temperature to 350℃. Maintain the reaction pressure at 0.4 MPa and react at a constant temperature for 6 h (temperature fluctuation ≤ ±4℃).

[0315] 4) Post-processing: After the reaction is completed, the product is naturally cooled to room temperature. The product is then subjected to air jet milling with the inlet pressure controlled at 0.9 MPa, the feed rate at 25 kg / h, and the classifier speed at 28,000 r / min. The particle size D50 after milling is 2.7 μm. The filter cake is then placed directly in a vacuum drying oven and dried at 90℃ and -0.085 MPa for 2.5 h. The temperature is then raised to 110℃ and -0.095 MPa for another 2 h, for a total drying time of 4.5 h, yielding 21.8 g of lithium sulfide product.

[0316] The product was tested and found to have a purity of 99.93% and a carbon content of 0.07%.

[0317] Product characterization data:

[0318] (1) XRD analysis: The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks;

[0319] (2) XPS analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, which are only slightly higher than those of the S 2p orbitals. 2- Characteristic peaks, free of impurities, sulfur species, and excess carbon;

[0320] (3) Particle size analysis: D50 = 2.7 μm, distribution range 1.0-5.5 μm, which meets the control requirements within 3 μm;

[0321] (4) SEM analysis: The product is a spherical particle with good dispersibility, slight local agglomeration, and good surface smoothness;

[0322] (5) Carbon content analysis: The elemental analyzer detected a carbon content of 0.07%, which meets the control requirement of ≤0.1%.

[0323] Example 4: A method for preparing lithium sulfide

[0324] The preparation of lithium sulfide using anhydrous lithium hydroxide, sulfur dioxide, and hydrogen as raw materials includes the following steps:

[0325] 1) Pretreatment: Take 24g (1.0mol) of anhydrous lithium hydroxide (granular) with a purity of 99%, place it in a vacuum drying oven, control the vacuum degree to -0.05MPa, and dry at 410℃ for 2.5h to remove moisture;

[0326] 2) First stage reaction: The dried anhydrous lithium hydroxide was placed in a high-pressure reactor, sealed, and stirred (stirring speed 180 r / min). Sulfur dioxide gas with a purity of 99.8% was introduced, and the sulfur dioxide introduction rate was controlled at 0.8 L / (h·mol anhydrous lithium hydroxide). The molar ratio of anhydrous lithium hydroxide to sulfur dioxide was 2:1.05. The reaction temperature was controlled at 60℃ (low temperature system), the reaction pressure was 0.15 MPa, and the reaction time was 7 h, generating lithium sulfite intermediate.

[0327] 3) Second stage reaction: Stop the introduction of sulfur dioxide, and introduce nitrogen gas with a purity of 99.99% into the reactor to replace the residual gas. The nitrogen introduction rate is 0.25 L / min, and the replacement time is 25 min. Then, hydrogen gas with a purity of 99.9% is introduced as a reducing gas, and the hydrogen introduction rate is controlled at 1.5 L / (h·mol lithium sulfite). The temperature is increased to 200℃ at a rate of 10℃ / min, and then switched to a rate of 7℃ / min to increase to 350℃. The reaction pressure is maintained at 0.4 MPa, and the reaction is carried out at a constant temperature for 6 h (temperature fluctuation ≤ ±4℃).

[0328] 4) Post-processing: After the reaction is completed, the product is naturally cooled to room temperature. The product is then subjected to air jet milling with the inlet pressure controlled at 0.9 MPa, the feed rate at 25 kg / h, and the classifier speed at 28,000 r / min. The particle size D50 after milling is 2.7 μm. The filter cake is then placed directly in a vacuum drying oven and dried at 90℃ and -0.085 MPa for 2.5 h. The temperature is then raised to 110℃ and -0.095 MPa for another 2 h, for a total drying time of 4.5 h, yielding 21.8 g of lithium sulfide product.

[0329] The product was tested and found to have a purity of 99.93% and a carbon content of 0.07%.

[0330] Product characterization data:

[0331] (1) XRD analysis: The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks;

[0332] (2) XPS analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, which are only slightly higher than those of the S 2p orbitals. 2- Characteristic peaks, free of impurities, sulfur species, and excess carbon;

[0333] (3) Particle size analysis: D50 = 2.7 μm, distribution range 1.0-5.5 μm, which meets the control requirements within 3 μm;

[0334] (4) SEM analysis: The product is a spherical particle with good dispersibility, slight local agglomeration, and good surface smoothness;

[0335] (5) Carbon content analysis: The elemental analyzer detected a carbon content of 0.07%, which meets the control requirement of ≤0.1%.

[0336] Example 5: A method for preparing lithium sulfide

[0337] The preparation of lithium sulfide using lithium hydroxide, sulfur dioxide, and hydrogen as raw materials includes the following steps:

[0338] 1) Pretreatment: Take 33.4g (1.0mol) of lithium hydroxide monohydrate (powder) with a purity of 98%, place it in a vacuum drying oven, control the vacuum degree to -0.07MPa, and dry at 240℃ for 4h to remove water of crystallization;

[0339] 2) First stage reaction: The dried lithium hydroxide was placed in a high-pressure reactor, sealed, and stirred (stirring rate 280 r / min). Sulfur dioxide gas with a purity of 99.5% was introduced, and the sulfur dioxide introduction rate was controlled at 1.8 L / (h·mol lithium hydroxide). The molar ratio of lithium hydroxide to sulfur dioxide was 2:1.2. The reaction temperature was controlled at 110℃ (medium temperature system), the reaction pressure was 0.4 MPa, and the reaction time was 3.5 h, generating lithium sulfite intermediate.

[0340] 3) Second stage reaction: Stop the introduction of sulfur dioxide, and introduce 99.99% pure argon gas into the reactor to replace the residual gas. The argon gas introduction rate is 0.4 L / min, and the replacement time is 35 min. Then, introduce 99.9% pure hydrogen gas as a reducing gas, and control the hydrogen gas introduction rate at 2.8 L / (h·mol lithium sulfite). Increase the temperature to 200℃ at a rate of 8℃ / min, and then switch to a rate of 5℃ / min to increase the temperature to 450℃. Maintain the reaction pressure at 0.6 MPa and react at a constant temperature for 4 h (temperature fluctuation ≤ ±2℃).

[0341] 4) Post-processing: After the reaction is completed, the product is naturally cooled to room temperature. The product is then subjected to air jet milling with the inlet pressure controlled at 0.85 MPa, the feed rate at 22 kg / h, and the classifier speed at 26000 r / min. The particle size D50 after milling is 2.8 μm. The filter cake is then placed directly in a vacuum drying oven and dried at 120℃ and -0.1 MPa for 3 h to obtain 21.6 g of lithium sulfide product.

[0342] The product was tested and found to have a purity of 99.94% and a carbon content of 0.05%.

[0343] Product characterization data:

[0344] (1) XRD analysis: The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks and high crystallinity;

[0345] (2) XPS analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, corresponding to S 2- Free from impurities, sulfur species, and excess carbon;

[0346] (3) Particle size analysis: D50 = 2.8 μm, distribution range 1.0-5.8 μm, which meets the control requirements within 3 μm;

[0347] (4) SEM analysis: The product is a uniform spherical particle with excellent dispersibility, no agglomeration, smooth and dense surface, and complete and defect-free crystal morphology;

[0348] (5) Carbon content analysis: The elemental analyzer detected 0.05%, which is far below the control limit of 0.1%.

[0349] Example 6: A method for preparing lithium sulfide

[0350] Includes the following steps:

[0351] (1) Lithium source pretreatment: Anhydrous lithium hydroxide was vacuum dried at a temperature of 350℃, a vacuum degree of -0.06MPa and a drying time of 2.5h to obtain the pretreated lithium source;

[0352] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source was fed into a rotary kiln, and sulfur dioxide gas with a purity of ≥99.5% was introduced for reaction. The rotation speed was controlled at 5 r / min, the filling rate was 20%, the reaction temperature in the low-temperature section was 65℃, and the reaction conditions were a gas space velocity of 800 h⁻¹. -1 The reaction time was 7 hours; the reaction temperature in the mesophilic phase was 250°C, and the reaction conditions were a gas space velocity of 1800 h⁻¹. -1 The reaction time is 5 hours to produce lithium sulfite intermediate;

[0353] (3) Lithium sulfide preparation: First, nitrogen gas with a purity ≥99.99% is introduced into the reduction section for purging and replacement for 45 min to ensure that the oxygen content is <100 ppm. Then, hydrogen gas is introduced to react with the lithium sulfite intermediate. The rotary kiln speed is controlled at 5 r / min and the filling rate is 15%. The hydrogen reduction (purity ≥99.9%) conditions are 400℃ and 1200 h⁻¹. - ¹ The reaction time is 6 hours, and crude lithium sulfide is obtained.

[0354] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.9 MPa inlet pressure, 20 kg / h feed rate and 25000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 100℃, vacuum degree of -0.09 MPa and drying time of 4.5 h to obtain the finished lithium sulfide product.

[0355] The product was tested and found to have a purity of 99.92% and a carbon content of 0.07%.

[0356] Product characterization data:

[0357] (1) XRD analysis: The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks and high crystallinity;

[0358] (2) XPS analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, corresponding to S 2-Free from impurities, sulfur species, and excess carbon;

[0359] (3) Particle size analysis: D50 = 2.8 μm, distribution range 1.0-5.8 μm, which meets the control requirements within 3 μm;

[0360] (4) SEM analysis: The product is a uniform spherical particle with excellent dispersibility, no agglomeration, smooth and dense surface, and complete and defect-free crystal morphology;

[0361] (5) Carbon content analysis: The elemental analyzer detected 0.07%, which is far below the control limit of 0.1%.

[0362] Example 7: A method for preparing lithium sulfide

[0363] Includes the following steps:

[0364] (1) Lithium source pretreatment: Anhydrous lithium hydroxide was vacuum dried at a temperature of 350℃, a vacuum degree of -0.06MPa and a drying time of 2.5h to obtain the pretreated lithium source;

[0365] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source was fed into a rotary kiln, and sulfur dioxide gas with a purity of ≥99.5% was introduced for reaction. The rotation speed was controlled at 5 r / min, the filling rate was 20%, the reaction temperature in the low-temperature section was 65℃, and the reaction conditions were a gas space velocity of 800 h⁻¹. -1 The reaction time was 7 hours; the reaction temperature in the mesophilic phase was 250°C, and the reaction conditions were a gas space velocity of 1800 h⁻¹. -1 The reaction time is 5 hours to produce lithium sulfite intermediate;

[0366] (3) Lithium sulfide preparation: First, nitrogen gas with a purity of ≥99.99% is introduced into the reduction section for purging and replacement for 45 min to ensure that the oxygen content is <100 ppm. Then, methane is introduced to react with the lithium sulfite intermediate under the following conditions: reaction temperature 550℃ and gas space velocity 1000 h⁻¹. -1 The reaction time is 9 hours, and crude lithium sulfide is obtained.

[0367] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.9 MPa inlet pressure, 20 kg / h feed rate and 25000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 100℃, vacuum degree of -0.09 MPa and drying time of 4.5 h to obtain the finished lithium sulfide product.

[0368] The product was tested and found to have a purity of 99.91% and a carbon content of 0.08%.

[0369] Product characterization data:

[0370] (1) XRD analysis: The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks and high crystallinity;

[0371] (2) XPS analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, corresponding to S 2- Free from impurities, sulfur species, and excess carbon;

[0372] (3) Particle size analysis: D50 = 2.8 μm, distribution range 1.0-5.8 μm, which meets the control requirements within 3 μm;

[0373] (4) SEM analysis: The product is a uniform spherical particle with excellent dispersibility, no agglomeration, smooth and dense surface, and complete and defect-free crystal morphology;

[0374] (5) Carbon content analysis: The elemental analyzer detected 0.08%, which is far below the control limit of 0.1%.

[0375] Example 8: A method for preparing lithium sulfide

[0376] Includes the following steps:

[0377] (1) Lithium source pretreatment: The lithium oxide was vacuum dried to remove water at a temperature of 150℃, a vacuum degree of -0.06MPa and a drying time of 3.5h to obtain the pretreated lithium source;

[0378] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source was fed into a rotary kiln, and sulfur dioxide gas with a purity of ≥99.5% was introduced for reaction. The rotation speed was controlled at 5 r / min, the filling rate was 20%, the reaction temperature in the low-temperature section was 65℃, and the reaction conditions were a gas space velocity of 800 h⁻¹. -1 The reaction time was 7 hours; the reaction temperature in the mesophilic phase was 250°C, and the reaction conditions were a gas space velocity of 1800 h⁻¹. -1 The reaction time is 5 hours to produce lithium sulfite intermediate;

[0379] (3) Lithium sulfide preparation: First, nitrogen gas with a purity of ≥99.99% is introduced into the reduction section for purging and replacement for 45 min to ensure that the oxygen content is <100 ppm. Then, methane is introduced to react with the lithium sulfite intermediate under the following conditions: reaction temperature 550℃ and gas space velocity 1000 h⁻¹. -1 The reaction time is 9 hours, and crude lithium sulfide is obtained.

[0380] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.9 MPa inlet pressure, 20 kg / h feed rate and 25000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 100℃, vacuum degree of -0.09 MPa and drying time of 4.5 h to obtain the finished lithium sulfide product.

[0381] The product was tested and found to have a purity of 99.94% and a carbon content of 0.05%.

[0382] Product characterization data:

[0383] (1) XRD analysis: The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks and high crystallinity;

[0384] (2) XPS analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, corresponding to S 2- Free from impurities, sulfur species, and excess carbon;

[0385] (3) Particle size analysis: D50 = 2.8 μm, distribution range 1.0-5.8 μm, which meets the control requirements within 3 μm;

[0386] (4) SEM analysis: The product is a uniform spherical particle with excellent dispersibility, no agglomeration, smooth and dense surface, and complete and defect-free crystal morphology;

[0387] (5) Carbon content analysis: The elemental analyzer detected 0.05%, which is far below the control limit of 0.1%.

[0388] Example 9: A method for preparing lithium sulfide

[0389] Includes the following steps:

[0390] (1) Lithium source pretreatment: The lithium oxide was vacuum dried to remove water at a temperature of 150℃, a vacuum degree of -0.06MPa and a drying time of 3.5h to obtain the pretreated lithium source;

[0391] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source was fed into a rotary kiln, and sulfur dioxide gas with a purity of ≥99.5% was introduced for reaction. The rotation speed was controlled at 5 r / min, the filling rate was 20%, the reaction temperature in the low-temperature section was 65℃, and the reaction conditions were a gas space velocity of 800 h⁻¹. -1 The reaction time was 7 hours; the reaction temperature in the mesophilic phase was 250°C, and the reaction conditions were a gas space velocity of 1800 h⁻¹. -1 The reaction time is 5 hours to produce lithium sulfite intermediate;

[0392] (3) Lithium sulfide preparation: First, nitrogen gas with a purity ≥99.99% is introduced into the reduction section for purging and replacement for 45 min to ensure that the oxygen content is <100 ppm. Then, hydrogen gas is introduced to react with the lithium sulfite intermediate. The rotary kiln speed is controlled at 5 r / min and the filling rate is 15%. The hydrogen reduction (purity ≥99.9%) conditions are 400℃ and 1200 h⁻¹. - ¹ The reaction time is 6 hours, and crude lithium sulfide is obtained.

[0393] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.9 MPa inlet pressure, 20 kg / h feed rate and 25000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 100℃, vacuum degree of -0.09 MPa and drying time of 4.5 h to obtain the finished lithium sulfide product.

[0394] The product was tested and found to have a purity of 99.98% and a carbon content of 0.01%.

[0395] Product characterization data:

[0396] (1) XRD analysis: The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks and high crystallinity;

[0397] (2) XPS analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, corresponding to S 2- Free from impurities, sulfur species, and excess carbon;

[0398] (3) Particle size analysis: D50 = 2.8 μm, distribution range 1.0-5.8 μm, which meets the control requirements within 3 μm;

[0399] (4) SEM analysis: The product is a uniform spherical particle with excellent dispersibility, no agglomeration, smooth and dense surface, and complete and defect-free crystal morphology;

[0400] (5) Carbon content analysis: The elemental analyzer test result was 0.01%.

[0401] Example 10: A method for preparing lithium sulfide

[0402] Includes the following steps:

[0403] (1) Lithium source pretreatment: Anhydrous lithium hydroxide was vacuum dried at a temperature of 350℃, a vacuum degree of -0.06MPa and a drying time of 2.5h to obtain the pretreated lithium source;

[0404] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source is fed into a fluidized bed and sulfur dioxide gas with a purity of ≥99.5% is introduced for reaction. The apparent gas velocity is controlled at 0.35 m / s and the bed temperature uniformity is ±5℃. The reaction temperature in the low temperature section is 70℃ and the reaction time is 5h; the reaction temperature in the medium temperature section is 300℃ and the reaction time is 3h to produce lithium sulfite intermediate.

[0405] (3) Preparation of lithium sulfide: First, the bed is replaced with nitrogen for 30 min, then hydrogen is switched to control the apparent gas velocity at 0.4 m / s, the reduction temperature is 400℃ and the reaction time is 4.5 h to obtain crude lithium sulfide;

[0406] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.9 MPa inlet pressure, 20 kg / h feed rate and 25000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 100℃, vacuum degree of -0.09 MPa and drying time of 4.5 h to obtain the finished lithium sulfide product.

[0407] The product was tested and found to have a purity of 99.91% and a carbon content of 0.08%.

[0408] Product characterization data:

[0409] (1) XRD analysis: The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks and high crystallinity;

[0410] (2) XPS analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, corresponding to S 2- Free from impurities, sulfur species, and excess carbon;

[0411] (3) Particle size analysis: D50 = 2.8 μm, distribution range 1.0-5.8 μm, which meets the control requirements within 3 μm;

[0412] (4) SEM analysis: The product is a uniform spherical particle with excellent dispersibility, no agglomeration, smooth and dense surface, and complete and defect-free crystal morphology;

[0413] (5) Carbon content analysis: The elemental analyzer detected 0.08%, which is far below the control limit of 0.1%.

[0414] Example 11: A method for preparing lithium sulfide

[0415] Includes the following steps:

[0416] (1) Lithium source pretreatment: The lithium oxide was vacuum dried to remove water at a temperature of 150℃, a vacuum degree of -0.06MPa and a drying time of 3.5h to obtain the pretreated lithium source;

[0417] (2) Preparation of lithium sulfite intermediate: The pretreated lithium source is fed into a fluidized bed and sulfur dioxide gas with a purity of ≥99.5% is introduced for reaction. The apparent gas velocity is controlled at 0.35 m / s and the bed temperature uniformity is ±5℃. The reaction temperature in the low temperature section is 70℃ and the reaction time is 5h; the reaction temperature in the medium temperature section is 300℃ and the reaction time is 3h to produce lithium sulfite intermediate.

[0418] (3) Preparation of lithium sulfide: First, the bed is replaced with nitrogen for 30 min, then hydrogen is switched to control the apparent gas velocity at 0.4 m / s, the reduction temperature is 400℃ and the reaction time is 4.5 h to obtain crude lithium sulfide;

[0419] (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature and then subjected to air jet milling with parameters of 0.9 MPa inlet pressure, 20 kg / h feed rate and 25000 r / min classifier speed to precisely control the particle size. After milling, it is directly vacuum dried at 100℃, vacuum degree of -0.09 MPa and drying time of 4.5 h to obtain the finished lithium sulfide product.

[0420] The product was tested and found to have a purity of 99.93% and a carbon content of 0.06%.

[0421] Product characterization data:

[0422] (1) XRD analysis: The characteristic diffraction peaks completely match the lithium sulfide standard card (Li2S-PDF#00-023-0369), with no impurity peaks and high crystallinity;

[0423] (2) XPS analysis: The binding energies of the S 2p orbitals are 160.1 eV and 161.3 eV, corresponding to S 2- Free from impurities, sulfur species, and excess carbon;

[0424] (3) Particle size analysis: D50 = 2.8 μm, distribution range 1.0-5.8 μm, which meets the control requirements within 3 μm;

[0425] (4) SEM analysis: The product is a uniform spherical particle with excellent dispersibility, no agglomeration, smooth and dense surface, and complete and defect-free crystal morphology;

[0426] (5) Carbon content analysis: The elemental analyzer detected 0.06%, which is far below the control limit of 0.1%.

[0427] Comparative Example 1:

[0428] The specific steps for preparing lithium sulfide by direct reduction of lithium sulfate with hydrogen are as follows:

[0429] Lithium sulfate (Li2SO4) was prepared by reacting lithium carbonate (Li2CO3) with concentrated sulfuric acid, and then washed and dried to obtain pure phase lithium sulfate.

[0430] Lithium sulfate powder was placed in a tube furnace, and hydrogen gas with a purity of ≥99.9% was introduced. The temperature was increased to 750℃ at 5℃ / min, and the reaction was carried out at a constant temperature for 8 h with a hydrogen gas flow rate of 500 mL / min. After the reaction was completed, the mixture was allowed to cool naturally, and the product was ground and then tested.

[0431] result:

[0432] Product purity: 96.2%; carbon content: 0.25%; reaction temperature: 750℃; D50 particle size: 12.5 μm (due to severe agglomeration caused by high-temperature sintering); XRD showed the presence of a small amount of unreacted Li2SO4 and Li2O impurity peaks.

[0433] Comparative Example 2:

[0434] The specific steps for preparing lithium sulfide by high-temperature reduction of lithium sulfate with methane are as follows:

[0435] Lithium sulfate (Li2SO4) was prepared by reacting lithium carbonate (Li2CO3) with concentrated sulfuric acid, and then washed and dried to obtain pure phase lithium sulfate.

[0436] In a fluidized bed reactor, methane (purity ≥99.5%) was used as the reducing agent, the apparent gas velocity was 0.4 m / s, the temperature was programmed to 850℃, and the reaction was carried out for 10 h. After cooling, the product was pulverized by air jet (parameters are the same as in Example 1 of this invention) and then detected.

[0437] result:

[0438] Product purity: 97.5%; carbon content: 0.18% (carbon deposition due to methane cracking); reaction temperature: 850℃; D50 particle size: 8.7 μm; SEM showed that the particle surface was rough and there was obvious carbon coating.

[0439] Comparative Example 3:

[0440] The one-step high-temperature reduction of lithium hydroxide and sulfur dioxide to prepare lithium sulfide involves the following steps:

[0441] Anhydrous lithium hydroxide and sulfur dioxide were added directly to the rotary kiln at a molar ratio of 2:1.1.

[0442] Without nitrogen purging, hydrogen gas was directly introduced, and the temperature was increased from room temperature to 700°C at a rate of 10°C / min, and the reaction was maintained at this temperature for 6 hours. The post-reaction treatment was the same as in Example 1.

[0443] result:

[0444] Product purity: 94.8%; carbon content: 0.30%; reaction temperature: 700℃.

[0445] Note: Due to the lack of a lithium sulfite intermediate formation step, the reaction pathway is unclear, side reactions are increased, and Li2SO4, Li2O and a small amount of Li2S2O3 were detected in the product.

[0446] Comparative Example 4:

[0447] The specific steps for high-temperature reduction of lithium sulfite with hydrogen are as follows:

[0448] Pure-phase lithium sulfite intermediate was prepared according to the method in Example 1; lithium sulfite was heated to 700°C at 10°C / min under a hydrogen atmosphere and reduced at a constant temperature for 5 h; post-treatment was the same as in Example 1.

[0449] result:

[0450] Product purity: 98.1%; carbon content: 0.12%; reaction temperature: 700℃.

[0451] Note: Although the purity is slightly higher than that of direct reduction of lithium sulfate, the temperature is still significantly higher than that of this invention (300-450℃), and the particle size distribution of the product is wider (D50=6.2 μm), which proves that lithium sulfite will still undergo partial decomposition or sintering at high temperatures.

[0452] Comparative Example 5:

[0453] The specific steps for preparing lithium sulfide by low-temperature hydrogen reduction of lithium sulfate are as follows:

[0454] step:

[0455] Lithium sulfate (Li2SO4) was prepared by reacting lithium carbonate (Li2CO3) with concentrated sulfuric acid. After washing and drying, pure phase lithium sulfate was obtained. It was then reduced at 450°C for 10 h under a hydrogen atmosphere. The post-treatment was the same as in Example 1.

[0456] result:

[0457] Product purity: 68.5%; XRD showed that it was mainly unreacted Li2SO4 with only a small amount of Li2S generated.

[0458] This demonstrates that lithium sulfate is difficult to be effectively reduced by hydrogen at low temperatures, resulting in an extremely low conversion rate.

[0459] Based on the above test results, it can be concluded that:

[0460] 1. The reaction pathway determines the reaction temperature and purity:

[0461] Lithium sulfate (Li2SO4) has high S=O bond energy and stable structure, so it can only be reduced at a high temperature of ≥700℃. The purity of the product is generally no more than 98%, and it is accompanied by problems such as sintering and carbon deposition (Comparative Example 1 and Comparative Example 2).

[0462] The present invention uses lithium sulfite (Li2SO3) as an intermediate, which has a low SO bond energy and can be efficiently reduced to Li2S at 300-450℃, with the product purity easily reaching over 99.9%.

[0463] 2. The key role of intermediates:

[0464] Comparative Example 3 confirms that without a clear lithium sulfite intermediate generation step, direct high-temperature reduction leads to a chaotic reaction pathway, increased byproducts, and a significant decrease in purity. Comparative Example 4 further illustrates that even when lithium sulfite is used, if the reduction temperature is too high (700°C), it will still lead to product sintering and increased particle size, proving that the medium-low temperature reduction window (300-450°C) of the present invention has both high conversion rate and excellent product morphology.

[0465] 3. Verification of the infeasibility of low-temperature reduction:

[0466] Comparative Example 5 confirms that lithium sulfate is almost impossible to reduce at 450°C, highlighting the irreplaceable role of the lithium sulfite pathway in terms of low energy consumption and high reaction efficiency.

[0467] In summary, this invention, through a progressive reaction path of "lithium source → lithium sulfite → lithium sulfide" combined with a medium-low temperature reduction process, successfully achieves the green and efficient preparation of high-purity (≥99.9%), low-impurity, and fine-particle-size (D50≤3μm) lithium sulfide. It is significantly superior to the traditional direct reduction process of lithium sulfate in terms of reaction temperature, product purity, and morphology control, and has clear innovative and industrialization advantages.

[0468] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing lithium sulfide, characterized in that: The preparation method includes the following steps: (1) Lithium source pretreatment: The lithium source is subjected to vacuum drying to remove water, and the pretreated lithium source is obtained; the lithium source is anhydrous lithium hydroxide or lithium oxide; (2) Preparation of lithium sulfite intermediate: The pretreated lithium source is fed into the reactor and sulfur dioxide gas with a purity of ≥99.5% is introduced to react and produce lithium sulfite intermediate; The reactor is a rotary kiln or a fluidized bed; When the reactor is a rotary kiln, the rotation speed is controlled at 1-10 r / min, the filling rate is 10-30%, the reaction temperature in the low-temperature section is 50-80℃, and the reaction conditions are a gas space velocity of 500-1000 h⁻¹. -1 The reaction time is 6-8 hours; the reaction temperature in the mesophilic range is 100-320℃, and the reaction conditions are a gas space velocity of 1000-2000 h⁻¹. -1 The reaction time is 3-6 hours. When the reactor is a fluidized bed, the apparent gas velocity is controlled at 0.1-0.5 m / s, the bed temperature uniformity is ±5℃, the reaction temperature in the low temperature section is 50-80℃, and the reaction time is 4-6 h; the reaction temperature in the medium temperature section is 200-440℃, and the reaction time is 2-4 h. (3) Preparation of lithium sulfide: A reducing gas is introduced into the reactor to react with the lithium sulfite intermediate to obtain crude lithium sulfide. The reducing gas is hydrogen. A rotary kiln with a series reduction section is used, with hydrogen as the reducing gas. First, an inert gas with a purity ≥99.99% is introduced into the reduction section for purging and replacement for 30-60 minutes, ensuring an oxygen content <100ppm. Then, hydrogen is introduced, controlling the rotary kiln speed at 1-8 r / min and the filling rate at 10-25%. The hydrogen reduction conditions are a temperature of 300-450℃ and a gas hourly space velocity of 800-1500 h⁻¹. -1 Reaction time: 4-7 hours; The fluidized bed synthesis-reduction process is adopted, with hydrogen as the reducing gas. The bed is first replaced by an inert gas for 20-40 minutes, and then switched to hydrogen. The apparent gas velocity is controlled at 0.1-0.6 m / s, the reduction temperature is 300-450℃, and the reaction time is 3-6 h. (4) Post-processing: After the reaction is completed, the crude lithium sulfide is cooled to room temperature, then subjected to air jet milling, and then vacuum dried to obtain the finished lithium sulfide product.

2. The preparation method according to claim 1, characterized in that: The purity of the lithium source mentioned in step (1) is ≥98%.

3. The preparation method according to claim 1, characterized in that: The specific preprocessing operations described in step (1) are as follows: When the lithium source is anhydrous lithium hydroxide, the drying temperature is 200-430℃, the vacuum degree is -0.05~-0.08MPa, and the drying time is 2-3h. When the lithium source is lithium oxide, the drying temperature is 120-160℃, the vacuum degree is -0.05~-0.08MPa, and the drying time is 2-4h.

4. The preparation method according to claim 3, characterized in that: The specific preprocessing operations described in step (1) are as follows: When the lithium source is anhydrous lithium hydroxide, the drying temperature is 350℃, the vacuum degree is -0.06MPa, and the drying time is 2.5h. When the lithium source is lithium oxide, the drying temperature is 150℃, the vacuum degree is -0.06MPa, and the drying time is 3.5h.

5. The preparation method according to claim 1, characterized in that: When the reactor is a rotary kiln, the rotation speed is controlled at 5 r / min, the filling rate is 20%, the reaction temperature in the low-temperature section is 65℃, and the reaction conditions are a gas space velocity of 800 h⁻¹. -1 The reaction time was 7 hours; the reaction temperature in the mesophilic phase was 250°C, and the reaction conditions were a gas space velocity of 1800 h⁻¹. -1 The reaction time is 5 hours.

6. The preparation method according to claim 1, characterized in that: When the reactor is a fluidized bed, the apparent gas velocity is controlled at 0.35 m / s, the bed temperature uniformity is ±5℃, the low temperature reaction temperature is 70℃, and the reaction time is 5h; the medium temperature reaction temperature is 300℃, and the reaction time is 3h.

7. The preparation method according to claim 1, characterized in that: The molar ratio of lithium source to sulfur dioxide in step (2) is 1:1.0-1.

2.

8. The preparation method according to claim 7, characterized in that: The molar ratio of lithium source to sulfur dioxide in step (2) is 1:1.

1.

9. The preparation method according to claim 1, characterized in that: A rotary kiln with a series reduction section was used, with hydrogen as the reducing gas. The specific steps were as follows: First, an inert gas with a purity ≥99.99% was introduced into the reduction section for purging and replacement for 45 minutes to ensure that the oxygen content was <100ppm. Then, hydrogen was introduced, and the rotary kiln speed was controlled at 5r / min and the filling rate at 15%. The hydrogen reduction conditions were a temperature of 400℃ and a gas space velocity of 1200h⁻¹. -1 The reaction time is 6 hours.

10. The preparation method according to claim 1, characterized in that: The reducing gas mentioned in step (3) can also be methane.

11. The preparation method according to claim 10, characterized in that: A rotary kiln with a series reduction section is used, with methane as the reducing gas. First, an inert gas with a purity ≥99.99% is introduced into the reduction section for purging and replacement for 30-60 minutes, ensuring an oxygen content <100 ppm. Then, methane is introduced for reduction under the following conditions: reaction temperature 450-600℃ and gas hourly space velocity 600-1200 h⁻¹. -1 The reaction time is 7-10 hours.

12. The preparation method according to claim 1, characterized in that: A rotary kiln with a series reduction section was used, with methane as the reducing gas. First, an inert gas with a purity ≥99.99% was introduced into the reduction section for purging and replacement for 50 minutes to ensure an oxygen content <100 ppm. Then, methane was introduced for reduction under the following conditions: reaction temperature 550℃ and gas hourly space velocity (GHSV) 1000 h⁻¹. -1 The reaction time is 9 hours.

13. The preparation method according to claim 1, characterized in that: The fluidized bed synthesis-reduction method was adopted, with hydrogen as the reducing gas. The specific steps were as follows: first, the bed was replaced with an inert gas for 30 minutes, and then hydrogen was switched to control the apparent gas velocity at 0.4 m / s, the reduction temperature at 400℃, and the reaction time at 4.5 h.

14. The preparation method according to claim 1, characterized in that: The fluidized bed synthesis-reduction process was adopted, with methane as the reducing gas. The bed was first replaced with an inert gas for 30 minutes, and then switched to methane. The methane reduction reaction temperature was 550℃ and the reaction time was 7.5 hours.

15. The preparation method according to claim 1, characterized in that: The airflow pulverization process parameters mentioned in step (4) are: inlet pressure of 0.7-1.0MPa, feed rate of 10-30kg / h, classifier rotation speed of 20000-30000r / min, and the particle size D50 of the resulting lithium sulfide product is controlled within 3μm.

16. The preparation method according to claim 1, characterized in that: The vacuum drying in step (4) is performed at a drying temperature of 80-120℃, a vacuum degree of -0.08~-0.1MPa, and a drying time of 3-6h.

17. Lithium sulfide prepared by the preparation method according to any one of claims 1-16, characterized in that: The lithium sulfide has a purity of ≥99.9%, a carbon content of ≤0.1%, and a particle size D50 of ≤3μm.

18. The use of lithium sulfide prepared by the preparation method according to any one of claims 1-16 in the preparation of lithium-sulfur batteries or semiconductor electronic materials.

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