Preparation method of battery-grade lithium sulfide

Abstract

The invention discloses a preparation method of battery-grade lithium sulfide, which comprises the following step: under the condition of oxygen isolation, reacting high-purity carbonyl sulfide serving as a sulfur source with a lithium source to prepare the battery-grade lithium sulfide. The method is low in production cost and simple in process, large-scale production is easy to realize, full-automatic unmanned factories are easy to realize, and the purity of the final product lithium sulfide prepared by using high-purity carbonyl sulfide as the raw material is very high; the raw material supply requirement and the harsh quality requirement of sulfide solid batteries, semi-solid batteries and the like on battery-grade lithium sulfide can be met, and the preparation method is suitable for the preparation requirement of various sulfide lithium batteries.

Description

Technical Field

[0001] The invention relates to the technical field of batteries, and in particular to a method for preparing battery-grade lithium sulfide. Background Art

[0002] Sulfide solid-state batteries have very strict quality requirements for raw material lithium sulfide, including high purity, appropriate particle size and particle size, optimized preparation process and cost control, and good stability and safety. Specifically, the quality requirements for raw material lithium sulfide of sulfide solid-state batteries include but are not limited to:

[0003] 1. Purity requirements

[0004] As one of the main raw materials for sulfide solid electrolytes, the purity of lithium sulfide (Li2S) has a crucial impact on the performance of the battery. The purity of battery-grade lithium sulfide is usually required to reach more than 99.9% to ensure high ionic conductivity, high energy density and good safety of the battery. High-purity lithium sulfide can reduce the adverse effects of impurities on battery performance and improve the cycle stability and service life of the battery.

[0005] 2. Particle size and particle size requirements

[0006] In addition to purity requirements, the particle size and diameter of lithium sulfide are also key factors affecting battery performance. The particle size of battery-grade lithium sulfide is generally required to reach the nanometer (1-1000nm) or micrometer (≤10μm) level, and the CV value of the particle size is less than 10% to ensure its uniform distribution and effective conduction in the solid electrolyte. Smaller particle size helps to improve the solubility and diffusion rate of lithium sulfide in the electrolyte, thereby improving the ionic conductivity and energy density of the battery.

[0007] 3. Preparation process and cost control

[0008] The preparation process of battery-grade lithium sulfide is complex and costly, which is one of the important factors restricting the commercial application of sulfide solid-state batteries. At present, the preparation methods of lithium sulfide mainly include new preparation technologies such as high-temperature solid-phase method and sol-gel method. However, these preparation methods still face challenges in improving the purity and crystallinity of lithium sulfide, and need further optimization and improvement. In addition, battery-grade lithium sulfide is expensive and accounts for a large proportion of the cost of all-solid-state sulfide solid-state batteries. Therefore, reducing the preparation cost of lithium sulfide and improving its production efficiency are the key to the commercial application of sulfide solid-state batteries.

[0009] IV. Stability and safety requirements

[0010] During the preparation and storage process, lithium sulfide easily reacts with water or oxygen in the air to produce toxic gases, so its stability and safety are also important considerations. In order to ensure the stability and safety of lithium sulfide, it is necessary to strictly control the reaction conditions and process parameters during the preparation process, and take effective measures to prevent it from contacting with the air. In addition, corresponding protective measures must also be taken during the assembly and use of the battery to ensure the safe operation of the battery.

[0011] Based on the above extremely stringent quality requirements, the synthesis and preparation of battery-grade lithium sulfide is a complex process involving multiple synthesis routes and methods. The following is a brief description of the existing common high-purity lithium sulfide synthesis routes and methods:

[0012] 1. Dry ball milling: In an inert atmosphere, elemental sulfur S and metallic lithium Li / lithium hydride LiH are mixed in proportion and then subjected to mechanical ball milling reaction to obtain lithium sulfide. Advantages and disadvantages: The process is simple, environmentally friendly, and no waste liquid is generated, but the material cost is high (metallic lithium), the reaction time is long, and the conversion rate is low. Although the purity of metallic lithium and sublimated sulfur can reach 3N~4N, the products prepared by this technical route contain impurities and by-products such as lithium polysulfide Li2S2, which are not easy to purify, and it is not easy to select industrial equipment.

[0013] 2. Organic solvent thermal method: lithium / lithium compounds and sulfur / sulfur compounds are mixed and reacted in an anhydrous solvent medium to prepare lithium sulfide. The solvent is an organic solvent or liquid ammonia; organic solvents are mostly aliphatic hydrocarbons, aromatic hydrocarbons or ether solvents, such as ethanol, hexane, toluene, ether, tetrahydrofuran THF, nitrogen methyl pyrrolidone NMP, etc. Advantages and disadvantages: liquid phase reaction is complete, raw material conversion rate is high, energy consumption is low; the process is simple and the working conditions are easy to control. However, organic solvents are flammable, explosive, volatile, serious environmental pollution, and difficult to recycle; the working conditions are highly dangerous and difficult to control.

[0014] 3. Double decomposition method: Sodium sulfide Na2S and lithium chloride LiCl are subjected to double decomposition reaction in ethanol solution, and the products are lithium sulfide with high solubility and sodium chloride with extremely low solubility. Advantages and disadvantages: extremely low cost; liquid phase reaction is fully complete and energy consumption is low; the process is simple and the working conditions are easy to control. However, organic solvents are flammable, explosive, and volatile, causing serious environmental pollution and are difficult to recycle; the purity of the product still has a lot of room for improvement, chloride ions and sodium ions are difficult to remove completely, and the product is difficult to reach 3N~4N.

[0015] 4. Thermal reduction method: In a reducing atmosphere (such as hydrogen), high temperature and high pressure, lithium / lithium compounds and sulfur / sulfur compounds are reduced or reacted in the gas phase to prepare lithium sulfide. Or by using the strong reducing property of carbon, carbon materials / carbon material precursors are directly added to the reaction of preparing lithium sulfide, and lithium sulfide / carbon composite materials with uniform dispersion, good performance and controllable morphology are synthesized in one step. Main disadvantages: high production cost, large equipment investment, and it is difficult to achieve a product purity of 3N~4N.

[0016] 5. Lithium amide method: ball-mill the defective lithium amide to obtain lithium amide granular powder, which is then reacted with hydrogen sulfide gas at high temperature to prepare lithium sulfide. Advantages and disadvantages: This method can recycle the defective lithium amide and prepare high-purity lithium sulfide at the same time. The prepared lithium sulfide can also enhance its ionic conductivity by synthesizing sulfide electrolyte. However, high-temperature reactions pose safety risks, hydrogen sulfide is prone to leakage, the preparation cost of lithium amide is high, and the post-processing and purification of the product is difficult.

[0017] 6. One-pot method: grind the sulfur source and lithium source (such as sulfur powder and lithium hydroxide), mix with anhydrous hydrazine after grinding to obtain a mixture; react the mixture to obtain lithium sulfide slurry; heat and dry the lithium sulfide slurry, then add sulfur powder and anhydrous hydrazine, heat and dry again to obtain high-purity lithium sulfide powder. Advantages: The one-pot preparation reaction is simple to operate. Disadvantages: The product has a high hydroxide content, and the highest purity is only 95%. It is reported that if special post-treatment is performed, the product purity can reach more than 99.9%, and the hydroxide content is less than 0.01%, but the cost of subsequent treatment is high. Since anhydrous hydrazine is extremely flammable and explosive, it is very dangerous, and the reaction involving anhydrous hydrazine must be absolutely oxygen-free, which is difficult to achieve in industrial mass production equipment.

[0018] 7. High-temperature carbon reduction method: High-temperature carbon reduction method is used to prepare lithium sulfide. The selected lithium sources are lithium sulfate, lithium carbonate, lithium hydroxide, etc., which saves production costs. Disadvantages: High-temperature reaction has certain safety risks and high energy consumption. The product purity is difficult to reach more than 99%; there is still a gap from the quality requirements of battery-grade lithium sulfide.

[0019] 8. Hydrogen sulfide reaction method: lithium hydroxide and hydrogen sulfide gas are reacted in an anhydrous solvent to prepare lithium sulfide, but this method requires the use of highly toxic hydrogen sulfide gas, which has high requirements for process safety. Disadvantages: Hydrogen sulfide is highly toxic and has a pungent smell, with a high risk of leakage and strict environmental supervision requirements.

[0020] It should be noted that the information disclosed in the above background technology section is only used for understanding the background of the present application, and therefore may include information that does not constitute prior art known to ordinary technicians in the field. Summary of the invention

[0021] The main purpose of the present invention is to provide a method for preparing battery-grade lithium sulfide.

[0022] In order to achieve the above object, the present invention adopts the following technical scheme:

[0023] A method for preparing battery-grade lithium sulfide comprises the following steps: under the condition of isolating oxygen, using high-purity carbonyl sulfide as a sulfur source to react with a lithium source to prepare battery-grade lithium sulfide.

[0024] Furthermore, the purity of the high-purity carbonyl sulfide is ≥99.9%.

[0025] Furthermore, the preparation method comprises the following steps: using liquefied carbonyl sulfide as a sulfur source, and directly carrying out a liquid-solid reaction with a solid powder of a lithium source in an excess amount of carbonyl sulfide to prepare battery-grade lithium sulfide.

[0026] Furthermore, the lithium source is at least one of lithium oxide, lithium carbonate and lithium hydroxide, and the reaction equations thereof are as follows:

[0027] COS+Li2O=Li2S+CO2↑;

[0028] COS+Li2CO3=Li2S+2CO2↑;

[0029] COS+2LiOH=Li2S+CO2↑+H2O↑.

[0030] Furthermore, the preparation method comprises the following steps:

[0031] S1. liquefying carbonyl sulfide and adding it to a reactor in liquid form; preferably, liquid carbonyl sulfide is added to the reactor at a feed temperature between -70°C and 80°C;

[0032] S2, preparing the lithium source into micron-sized fine powder, and feeding the solid powder into the reactor; preferably, the lithium source is added to the reactor at room temperature;

[0033] S3. Under the reaction pressure ensuring that the carbonyl sulfide is in liquid state and at the set reaction temperature, the carbonyl sulfide and the lithium source are fully reacted after vigorous stirring in the reactor. The reaction liquid obtained after the reaction is completed enters the gas-liquid separator, and the unreacted raw material carbonyl sulfide and the by-product carbon dioxide and water that can be gasified are separated under reduced pressure, and the product lithium sulfide that cannot be gasified is left at the bottom of the gas-liquid separator; preferably, the reaction temperature is -50°C to 80°C; preferably, the reaction pressure is between 0.1-8MPa.

[0034] Furthermore, the preparation method comprises the following steps:

[0035] A1. Dissolve carbonyl sulfide in an anhydrous organic solvent as material A;

[0036] A2, suspending the lithium source in powder form in an organic solvent that has absorbed ammonia as material B;

[0037] A3, fully react material A and material B in a reactor; preferably the reaction temperature is 40-50°C;

[0038] A4. After the reaction is completed, the volatile gas is removed through a gas-liquid separator to obtain a mixture containing urea and lithium sulfide;

[0039] A5. Separate urea from the mixture of urea and lithium sulfide, and grind to obtain battery-grade ultrafine lithium sulfide powder.

[0040] Furthermore, the lithium source is at least one of lithium oxide, lithium carbonate and lithium hydroxide, and the reaction equations thereof are as follows:

[0041] COS+2NH3+Li2O=CO(NH2)2+Li2S+H2O↑;

[0042] COS+2NH3+Li2CO3=CO(NH2)2+Li2S+H2O↑+CO2↑;

[0043] COS+2NH3+2LiOH=CO(NH2)2+Li2S+2H2O↑;

[0044] Preferably, the lithium source is lithium oxide.

[0045] Furthermore, the preparation method comprises the following steps:

[0046] B1. In an anhydrous organic solvent, carbonyl sulfide reacts with ammonia to prepare high-purity thiourea solid powder. The reaction equation is as follows:

[0047] COS+2NH3=CS(NH2)2+H2O↑;

[0048] B2. The thiourea solid powder obtained in step B1 is mixed with the solid powder of lithium hydroxide by dry ball milling, and the thiourea is reacted in an excess amount. After the reaction is completed, the excess thiourea is removed by heating and vacuuming to prepare a battery-grade lithium sulfide ultrafine powder. The reaction equation is as follows:

[0049] CS(NH2)2+2LiOH=Li2S+CO2↑+2NH3↑.

[0050] Furthermore, the anhydrous organic solvent in step B1 is at least one of methanol and ethanol.

[0051] Furthermore, in step B2, the reaction temperature is between 40°C and 180°C, preferably between 90°C and 120°C.

[0052] The present invention has the following beneficial effects: the present invention provides a method for preparing battery-grade lithium sulfide with high product purity and excellent product quality, which can meet various quality requirements of sulfide batteries, and the raw materials of the method are easily available and the impurities from the raw material end are extremely small. The present invention has low production cost, simple process, easy to realize large-scale production, easy to realize a fully automatic unmanned factory, and the final product lithium sulfide prepared by using high-purity carbonyl sulfide as raw material has very high purity (≥99.9%, even 5N-6N), which can meet the raw material supply demand and strict quality requirements of sulfide solid batteries and semi-solid batteries for battery-grade lithium sulfide, and is suitable for the preparation of various sulfide lithium batteries.

[0053] In a preferred embodiment, carbonyl sulfide can be purified to 3N-5N by means of double-tower distillation, etc.; the battery-grade lithium carbonate, lithium hydroxide, lithium oxide and other materials used as lithium sources are in sufficient supply and widely available, and can meet the raw material requirements of the present invention. The entire production process produces very little waste, meeting green environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 These are actual photos of the appearance of the battery-grade lithium sulfide prepared in Examples 1-3 of the present invention.

[0055] Figure 2 It is the result of XRD analysis of the samples prepared in Examples 1-3 of the present invention using Bruker EVA analysis software. DETAILED DESCRIPTION

[0056] The following is a detailed description of the embodiments of the present invention. It should be emphasized that the following description is only exemplary and is not intended to limit the scope and application of the present invention. In the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0057] Herein, "normal temperature" refers to 25°C ± 15°C.

[0058] A specific embodiment of the present invention provides a method for preparing battery-grade lithium sulfide, which includes the following steps: under the condition of isolating oxygen (for example, under the protection of nitrogen or inert gas), using high-purity carbonyl sulfide as a sulfur source, reacting with a lithium source to prepare battery-grade lithium sulfide.

[0059] In some embodiments, the purity of the high-purity carbonyl sulfide is ≥99.9%, ensuring the high purity of the sulfur source raw material.

[0060] Among them, carbonyl sulfide can be purchased and purified by distillation to obtain the high-purity carbonyl sulfide required for the specific embodiment of the present invention. It can also be prepared. The method for preparing carbonyl sulfide is well known in the art. The specific method includes but is not limited to the preparation method of carbonyl sulfide mentioned in many documents such as Chinese patent application CN109231207A. After the carbonyl sulfide is prepared, it can be purified by distillation to obtain the high-purity carbonyl sulfide required for the specific embodiment of the present invention.

[0061] In some embodiments, the preparation method includes the following steps: using liquefied carbonyl sulfide as a sulfur source, and directly reacting the solid powder of the lithium source with an excess of carbonyl sulfide to obtain battery-grade lithium sulfide. In this embodiment, carbonyl sulfide is used as both a reactant and a reaction solvent, which greatly improves the reaction rate and the controllability of the production process. Specifically, carbonyl sulfide has a high critical temperature and can be liquefied by pressurization at room temperature. Under normal pressure, the boiling point of carbonyl sulfide is only -50.2°C and it is extremely volatile. In order to promote the complete conversion of lithium-containing raw materials, the method of excessive feeding of carbonyl sulfide is adopted. Since excess carbonyl sulfide is easy to volatilize and separate due to its low boiling point, there is very little residue in the lithium sulfide product, which is conducive to ensuring the ultra-high purity of the product. Compared with hydrogen sulfide, carbonyl sulfide is less toxic and easy to automatically identify with sensors to reduce the risk of leakage.

[0062] The lithium source preferably has a purity of ≥99.9%, and the content of various impurity elements in the raw material is less than 20 ppm.

[0063] In some embodiments, the lithium source is at least one of lithium oxide, lithium carbonate, and lithium hydroxide, and the reaction equations thereof are as follows:

[0064] COS+Li2O=Li2S+CO2↑;

[0065] COS+Li2CO3=Li2S+2CO2↑;

[0066] COS+2LiOH=Li2S+CO2↑+H2O↑.

[0067] In some embodiments, the preparation method comprises the following steps:

[0068] S1. liquefying carbonyl sulfide and adding it to a reactor in liquid form; preferably, liquid carbonyl sulfide is added to the reactor at a feed temperature between -70°C and 80°C;

[0069] S2, preparing the lithium source into micron-sized (preferably not higher than 100 μm) fine powder, and feeding the solid powder into the reactor; preferably, the lithium source is added to the reactor at room temperature;

[0070] S3. Under a reaction pressure (usually 0.1 MPa to 8.0 MPa) that ensures that the carbonyl sulfide is in liquid state and at a set reaction temperature, the carbonyl sulfide and the lithium source are fully reacted in the reactor after vigorous stirring (preferably the stirring speed is ≥300 rpm (revolutions / minute) per second). The reaction liquid obtained after the reaction is completed enters a gas-liquid separator through a nozzle, and the unreacted raw material carbonyl sulfide and by-product carbon dioxide and water that can be gasified are separated under reduced pressure, leaving the product lithium sulfide that cannot be gasified at the bottom of the gas-liquid separator; preferably, the reaction temperature is -50°C to 80°C; preferably, the reaction pressure is between 0.1-8.0 MPa.

[0071] More preferably, the preparation method comprises the following steps:

[0072] S1, liquefying carbonyl sulfide and pumping it into a tubular reactor in liquid form through a feed pump;

[0073] S2, grinding the lithium source into micron-sized fine powder by ball milling, and feeding the fine powder into the tubular reactor in the form of fluid solid powder through a solid powder propeller such as a screw feeder;

[0074] S3. Under the reaction pressure to ensure that the carbonyl sulfide is liquid and at the set reaction temperature, the carbonyl sulfide and the lithium source are fully reacted in the reactor after vigorous stirring (within a specific temperature range, after the two are fully mixed, the reaction is completed after a residence time of 10-30 minutes to obtain a reaction solution containing lithium sulfide). After the reaction is completed, the reaction solution obtained enters a gas-liquid separator, and the unreacted raw material carbonyl sulfide and the by-product carbon dioxide and water that can be gasified are separated under reduced pressure, and then enter an alkali liquid absorption tower as tail gas to be absorbed and then discharged; the product lithium sulfide that cannot be gasified is left at the bottom of the gas-liquid separator, and is collected in a hopper after being purged with nitrogen to remove other gaseous impurities, and then the product containing lithium sulfide in the hopper is sent to a rotary dryer to remove the solvent to obtain the product lithium sulfide, and then sealed and packaged in plastic bags and aluminum foil bags.

[0075] Among them, the molar ratio of carbonyl sulfide to lithium element in the lithium source is 3-20:1. Specifically, when lithium oxide is used as the lithium source, the molar ratio of carbonyl sulfide to lithium oxide is 1.5-10:1; when lithium carbonate is used as the lithium source, the molar ratio of carbonyl sulfide to lithium carbonate is 1.5-10:1; when lithium hydroxide is used as the lithium source, the molar ratio of carbonyl sulfide to lithium hydroxide is 3-20:1, that is, the molar amount of carbonyl sulfide is much higher than the molar amount required for the reaction, thereby promoting the complete conversion of the lithium-containing raw materials participating in the reaction, and the excess carbonyl sulfide can be used as a reaction solvent to promote full contact of the reaction materials.

[0076] In some embodiments, the preparation method comprises the following steps:

[0077] A1. Dissolve carbonyl sulfide in an anhydrous organic solvent as material A;

[0078] A2. Suspending a lithium source in powder form in an organic solvent that has absorbed ammonia as material B; wherein the lithium source is also preferably of a purity ≥ 99.9%, and the contents of various impurity elements in the raw materials are all less than 20 ppm; preferably, the mass fraction of ammonia in the organic solvent that has absorbed ammonia is not less than 1%, and the maximum mass fraction of ammonia depends on the saturated solubility of ammonia in the organic solvent, and a better choice is that the mass fraction of ammonia is close to but lower than the saturated solubility; preferably, the organic solvents in step A1 and step A2 are the same to reduce the cost of solvent recovery, and the organic solvent is a polar organic solvent with a large solubility of carbonyl sulfide and ammonia, such as anhydrous methanol, anhydrous ethanol, anhydrous acetone, etc., to ensure that the solvent does not participate in the reaction.

[0079] A3. Fully react material A and material B in a reactor; preferably, the carbon sulfide in material A and the lithium source in material B are added in a molar ratio of 1-1.05 of the theoretical molar ratio required for the reaction, that is, carbon sulfide is added in a theoretical molar ratio or in a slightly excessive manner. Preferably, the reaction temperature is 40-50°C. A4. After the reaction is completed, the volatile gas is removed through a gas-liquid separator, and then purged with nitrogen, for example, to obtain a mixture containing urea and lithium sulfide;

[0080] A5. Separate urea from the mixture of urea and lithium sulfide (for example, dissolve and separate urea with an organic solvent such as anhydrous acetone), and grind to obtain battery-grade ultrafine lithium sulfide powder (and then dry to obtain a finished product).

[0081] For example, in some embodiments, material A and material B are continuously conveyed to a tubular reactor by a feed pump. After the two are fully mixed, the reaction is completed at a specific reaction temperature after a residence time of 10-30 minutes to obtain a reaction liquid containing lithium sulfide and urea. The volatile gas is removed by a gas-liquid separator, and the solvent is removed by evaporation to obtain a mixture containing lithium sulfide and urea. The mixture is then purified by recrystallization with another organic solvent, and the urea is removed by dissolving to obtain a lithium sulfide crystalline product. A battery-grade lithium sulfide ultrafine powder product is obtained through the steps of recrystallization, filtration, drying, and grinding.

[0082] In some embodiments, the lithium source is at least one of lithium oxide, lithium carbonate, and lithium hydroxide, and the reaction equations thereof are as follows:

[0083] COS+2NH3+Li2O=CO(NH2)2+Li2S+H2O↑;

[0084] COS+2NH3+Li2CO3=CO(NH2)2+Li2S+H2O↑+CO2↑;

[0085] COS+2NH3+2LiOH=CO(NH2)2+Li2S+2H2O↑.

[0086] Preferably, the lithium source is lithium oxide.

[0087] In some embodiments, the preparation method comprises the following steps:

[0088] B1. In an anhydrous organic solvent, carbonyl sulfide reacts with ammonia to prepare a high-purity thiourea solid powder; wherein, thiourea will precipitate during the reaction, and after the reaction is completed, thiourea will precipitate through the removal of solvent and recrystallization process to obtain a high-purity thiourea with a purity of ≥99.9%. The reaction equation is as follows:

[0089] COS+2NH3=CS(NH2)2+H2O↑.

[0090] B2. In the absence of solvent, the solid thiourea powder obtained in step B1 is reacted with the solid powder of lithium hydroxide in an excess amount of thiourea. After the reaction is completed, the excess thiourea is removed by heating and vacuuming to prepare a battery-grade ultrafine lithium sulfide powder. The reaction equation is as follows:

[0091] CS(NH2)2+2LiOH=Li2S+CO2↑+2NH3↑.

[0092] Wherein, step B2 is a solid phase reaction carried out by dry ball milling under solvent-free conditions, and the solid powder of thiourea and the solid powder of lithium hydroxide are ground into micron-sized particles, and the thiourea is in excess, and the solid phase reaction temperature is in the range of 40-180°C. The remaining thiourea in the reaction is gradually heated to the range of 180-220°C and removed by vacuuming or negative pressure sublimation. An appropriate excess of thiourea (compared with the theoretical value, the molar excess is 1%-10%) can promote the complete conversion of lithium hydroxide. After the reaction is completed, vacuuming and heating under the protection of an inert gas such as nitrogen can remove excess thiourea, thereby obtaining battery-grade anhydrous lithium sulfide ultrafine powder.

[0093] In some embodiments, the anhydrous organic solvent in step B1 is at least one of methanol and ethanol.

[0094] In some embodiments, the reaction temperature in step B2 is between 40°C and 180°C, preferably between 90°C and 120°C.

[0095] The specific embodiments of the present invention are further described below.

[0096] Example 1: Preparation of lithium sulfide by direct reaction of liquefied carbonyl sulfide with lithium source solid powder

[0097] The preparation is carried out using a tubular reactor as an example. Among them, material A is liquid carbonyl sulfide (purity ≥ 99.99%), the feeding temperature is -52°C, and 20,000 grams are fed per hour; material B is powdered lithium oxide with a purity ≥ 99.9%, which is fed into the reactor by a screw under nitrogen protection, and 6,503 grams are fed per hour. After the two are evenly mixed in a mixer, they are fed into a continuous flow tubular reactor by a peristaltic pump. The tubular reactor has a built-in heat source, the reaction temperature is 40-50°C, the reaction pressure is 2-3MPa, and the residence time in the reactor (ie, the reaction time) is 60 minutes.

[0098] After the reaction is completed, the synthetic liquid enters the gas-liquid separator after throttling and pressure reduction, and is separated by hydrocyclone and cyclone, and the slurry containing lithium sulfide solid powder is collected from the bottom of the hopper; the by-product carbon dioxide and excess carbonyl sulfide are sent to the tail gas absorption tower from the top pipeline of the separator, washed with cold ethanol, and then passed through the spray tower. After absorption and washing with sodium hydroxide aqueous solution, it is confirmed that there is no carbonyl sulfide residue in the tail gas (content <0.1ppm), and then it can be discharged to the outside.

[0099] The slurry collected in the hopper is injected into the double cone dryer in batches for vacuum drying. The drying temperature is set to 90-120°C. After drying for 30 minutes, the vacuum is broken with nitrogen and the drying is continued for another 30 minutes. Stop heating and cool naturally to room temperature under nitrogen protection. About 10kg of lithium sulfide product can be obtained per hour. Samples are taken for inspection, and the test report obtained is shown in Table 1 below:

[0100] Table 1

[0101]

[0102]

[0103] Example 2: Preparation of lithium sulfide by reaction of carbonyl sulfide, a lithium source, and ammonia in an organic solvent

[0104] Take a continuous flow tubular reactor as an example. 1307.3g of high-purity carbonyl sulfide is dissolved in 5000ml of anhydrous ethanol to prepare material A; 741.24g of liquid ammonia and 1042g of anhydrous lithium hydroxide are dispersed and dissolved in 5000ml of anhydrous ethanol in turn to prepare material B. Material A and material B are then pumped to the tubular reactor respectively, and the flow rate is controlled at 80-85ml / minute. The reaction temperature is controlled at 40-50°C, and the reaction time is controlled at about 1 hour. After the reaction is completed, the synthetic liquid is sent to a vacuum evaporator to remove most of the solvent, and the solid product can be gradually precipitated. After filtering and washing, the solid product obtained contains about 1000g of lithium sulfide and about 1307 grams of urea. The mixture is then dissolved in an organic solvent such as dichloroethane to separate lithium sulfide from the above solid mixture. The lithium sulfide product can be obtained by heating and evaporating to remove the solvent again. The obtained lithium sulfide was ball-milled under nitrogen protection to obtain about 960g of battery-grade lithium sulfide product with a particle size in the range of 0.1-10 microns. Samples were taken for inspection, and the obtained test report is shown in Table 2 below:

[0105] Table 2

[0106]

[0107] Example 3: Preparation of thiourea from carbonyl sulfide and then preparation of battery-grade lithium sulfide

[0108] 1307.3g of high-purity carbonyl sulfide is dissolved in 5000ml of anhydrous ethanol to obtain an ethanol solution containing carbonyl sulfide, which is then reacted with 741.3g of liquid ammonia, firstly completing low-temperature absorption at 0-10°C, then heating to 40-80°C for 2 hours, and then removing the solvent ethanol by reduced pressure evaporation to obtain about 1657.5g of thiourea. After testing, it is confirmed that the purity of thiourea is ≥99.9%.

[0109] After the above thiourea is mixed with 1042g of anhydrous lithium hydroxide (purity ≥ 99.9%) as a solid, it is ground by a ball mill for 4-8 hours, and then heated from 40°C to 180°C slowly, and the temperature rise rate per hour does not exceed 20°C. The carbon dioxide and ammonia produced by the reaction are promptly pumped away by a vacuum pump to promote the reaction. After the reaction is completed, the ball milling is stopped, the material is kept warm at 180°C, and the vacuum is continued for about 2 hours to remove excess thiourea, and about 1000g of battery-grade lithium sulfide powder can be obtained.

[0110] The samples were taken for testing, and the test report obtained is shown in Table 3 below:

[0111] Table 3

[0112]

[0113]

[0114] like Figure 1 As shown, it is a real photo of the appearance of the battery-grade lithium sulfide product obtained in Example 1-3, which is a pure white or milky white powder. Figure 2 The XRD test results of the samples prepared in Examples 1-3 of the present invention were analyzed by Bruker EVA analysis software, and the diffraction peaks completely overlapped with the PDF card (PDF 23-0369) of lithium sulfide (Li2S).

[0115] The high-purity and small-particle lithium sulfide white powder prepared by the present invention can meet the quality requirements of solid-state and semi-solid-state batteries for high-purity lithium sulfide, and is suitable for the preparation of various sulfide lithium batteries.

[0116] The above content is a further detailed description of the present invention in combination with specific / preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, without departing from the concept of the present invention, it can also make several substitutions or modifications to these described embodiments, and these substitutions or modifications should be regarded as belonging to the protection scope of the present invention. In the description of this specification, the description of the reference terms "an embodiment", "some embodiments", "preferred embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily target the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In the absence of mutual contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. A method for preparing battery-grade lithium sulfide, characterized in that: The method comprises the following steps: under the condition of isolating oxygen, using high-purity carbonyl sulfide as a sulfur source to react with a lithium source to prepare battery-grade lithium sulfide.

2. The method for preparing battery-grade lithium sulfide according to claim 1, characterized in that: The purity of the high-purity carbonyl sulfide is ≥99.9%.

3. The method for preparing battery-grade lithium sulfide according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: using liquefied carbonyl sulfide as a sulfur source, and directly carrying out a liquid-solid reaction with solid powder of a lithium source in an excessive amount of carbonyl sulfide to prepare battery-grade lithium sulfide.

4. The method for preparing battery-grade lithium sulfide according to claim 3, characterized in that: The lithium source is at least one of lithium oxide, lithium carbonate and lithium hydroxide, and the reaction equations thereof are as follows: COS+Li2O=Li2S+CO2↑; COS+Li2CO3=Li2S+2CO2↑; COS+2LiOH=Li2S+CO2↑+H2O↑.

5. The method for preparing battery-grade lithium sulfide according to claim 3, characterized in that: The preparation method comprises the following steps: S1. liquefying carbonyl sulfide and adding it to a reactor in liquid form; preferably, liquid carbonyl sulfide is added to the reactor at a feed temperature between -70°C and 80°C; S2, preparing the lithium source into micron-sized fine powder, and feeding the solid powder into the reactor; preferably, the lithium source is added to the reactor at room temperature; S3. Under the reaction pressure ensuring that the carbonyl sulfide is in liquid state and at the set reaction temperature, the carbonyl sulfide and the lithium source are fully reacted after vigorous stirring in the reactor. The reaction liquid obtained after the reaction is completed enters the gas-liquid separator, and the unreacted raw material carbonyl sulfide and the by-product carbon dioxide and water that can be gasified are separated under reduced pressure, and the product lithium sulfide that cannot be gasified is left at the bottom of the gas-liquid separator; preferably, the reaction temperature is -50°C to 80°C; preferably, the reaction pressure is between 0.1-8MPa.

6. The method for preparing battery-grade lithium sulfide according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: A1. Dissolve carbonyl sulfide in an anhydrous organic solvent as material A; A2, suspending the lithium source in powder form in an organic solvent that has absorbed ammonia as material B; A3, fully react material A and material B in a reactor; preferably the reaction temperature is 40-50°C; A4. After the reaction is completed, the volatile gas is removed through a gas-liquid separator to obtain a mixture containing urea and lithium sulfide; A5. Separate urea from the mixture of urea and lithium sulfide, and grind to obtain battery-grade ultrafine lithium sulfide powder.

7. The method for preparing battery-grade lithium sulfide according to claim 6, characterized in that: The lithium source is at least one of lithium oxide, lithium carbonate and lithium hydroxide, and the reaction equations thereof are as follows: COS+2NH3+Li2O=CO(NH2)2+Li2S+H2O↑; COS+2NH3+Li2CO3=CO(NH2)2+Li2S+H2O↑+CO2↑; COS+2NH3+2LiOH=CO(NH2)2+Li2S+2H2O↑; Preferably, the lithium source is lithium oxide.

8. The method for preparing battery-grade lithium sulfide according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: B1. In an anhydrous organic solvent, carbonyl sulfide reacts with ammonia to prepare high-purity thiourea solid powder. The reaction equation is as follows: COS+2NH3=CS(NH2)2+H2O↑; B2. The thiourea solid powder obtained in step B1 is mixed with the solid powder of lithium hydroxide by dry ball milling, and the thiourea is reacted in an excess amount. After the reaction is completed, the excess thiourea is removed by heating and vacuuming to prepare a battery-grade lithium sulfide ultrafine powder. The reaction equation is as follows: CS(NH2)2+2LiOH=Li2S+CO2↑+2NH3↑.

9. The preparation method according to claim 8, characterized in that: The anhydrous organic solvent in step B1 is at least one of methanol and ethanol.

10. The preparation method according to claim 8, characterized in that: The reaction temperature in step B2 is between 40°C and 180°C, preferably between 90°C and 120°C.

Images