Method for preparing lithium sulfide

Abstract

The present invention relates to a method for preparing lithium sulfide. According to the present invention, when preparing lithium sulfide by a reaction between a lithium raw material and hydrogen sulfide, the reaction is carried out under relatively mild conditions as compared to the prior art, and thus frequent repair or replacement due to corrosion and failure of a reactor and various piping is not required, thereby improving the economic feasibility of the process. In addition, by reusing unreacted hydrogen sulfide from which moisture has been removed and a solvent, process costs are reduced, thereby ensuring economic feasibility during mass production. Furthermore, moisture and water vapor generated by the lithium sulfide production reaction are effectively removed, thus preventing a reverse reaction back to lithium hydroxide and promoting a forward reaction, thus enabling the production of high-quality lithium sulfide with high purity and high yield. In addition, particle size adjustment can be achieved in units of μm without a separate pulverization space or pulverization step, thereby providing excellent convenience and mass production.

Description

lithium sulfide manufacturing method

[0001] The present invention relates to a method for producing lithium sulfide.

[0002] Lithium secondary batteries have high energy density and long lifespan, so they are widely used in electronic devices such as home appliances, laptop computers, and smartphones. Recently, their utilization has been greatly increasing, as they are also installed in electric vehicles (EVs) and hybrid electric vehicles (HEVs).

[0003] Lithium-ion secondary batteries, which are mainly used today, have been widely used as the main power source for mobile phones, laptops, and PCs since mass production began in 1991 due to their high energy density and output voltage. However, the organic electrolyte used to ensure smooth movement of lithium ions carries the risk of explosion in overheating and overcharge conditions, and can easily catch fire if there is an ignition source. In addition, when side reactions occur inside the battery, gas generation can cause problems such as reduced battery performance and stability.

[0004] To overcome the shortcomings of lithium-ion secondary batteries, active research and development is being conducted on lithium all-solid-state secondary batteries. Lithium all-solid-state secondary batteries not only reduce the risk of explosion by using a solid electrolyte instead of a volatile liquid electrolyte, but also offer the advantage of dramatically improving the energy density of the battery because they can use lithium metal or lithium alloy as the anode material.

[0005] Today, among the solid electrolyte candidates that can be installed in all-solid-state batteries, sulfide-based solid electrolytes, known for their high ductility and ionic conductivity, are evaluated as suitable for manufacturing high-capacity, large-scale secondary batteries. Lithium sulfide (Li2S) is considered a key material in the manufacturing process of such sulfide-based solid electrolytes. Various methods are known to synthesize lithium sulfide, but the most common method is known to be the reaction of lithium hydroxide (LiOH), lithium carbonate (Li2CO3), or metallic lithium with hydrogen sulfide (H2S).

[0006] Meanwhile, hydrogen sulfide gas is a highly corrosive gas, and when reacted with lithium compounds in a conventional metal reactor, it corrodes the reactor and various piping and other equipment, requiring frequent repairs and replacements, which reduces the economic feasibility of mass production of lithium sulfide.

[0007] In addition, when lithium compounds such as lithium hydroxide are reacted with hydrogen sulfide, water vapor is inevitably generated. The water vapor generated at this time not only interferes with the contact between the lithium compound and hydrogen sulfide, reducing the yield of lithium sulfide, but also reacts with lithium sulfide again to accelerate the reverse reaction into lithium hydroxide, thereby lowering the purity of the manufactured lithium sulfide. In addition, moisture and water vapor can cause agglomeration between the manufactured lithium sulfide particles, which can result in a decline in quality.

[0008] Accordingly, the inventors of the present invention have studied a method for economically manufacturing lithium sulfide having a size of several to several tens of microns by establishing a high-purity and high-yield process in which a lithium compound and hydrogen sulfide are reacted under relatively mild conditions, moisture is removed through gas bubbling to promote the positive reaction, and moisture is removed from the solvent and unreacted hydrogen sulfide, which is then reused in the manufacture of lithium sulfide, thereby completing the present invention.

[0009] The present invention is intended to solve the above problems, and provides a method for producing lithium sulfide, which is designed to have reaction conditions and an apparatus suitable for mass-producing lithium sulfide with high purity and high yield through a reaction between a lithium raw material and hydrogen sulfide (H2S), promotes the positive reaction through moisture removal, ensures economic feasibility by reusing unreacted hydrogen sulfide and solvent, and is capable of controlling particle size without a separate pulverization space or pulverization step, thereby providing convenience and excellent mass production potential.

[0010] The present specification provides a method for producing lithium sulfide, comprising: a) a step of supplying a lithium raw material into a reaction chamber equipped with a solvent; b) a step of supplying hydrogen sulfide (H2S) into the reaction chamber to cause a lithium sulfide (Li2S) production reaction, and simultaneously performing high-speed stirring to crush the product during the reaction; and c) a step of transferring the product obtained in step b to a lithium sulfide recovery unit to obtain lithium sulfide.

[0011] For example, after step a and before step b, the temperature inside the reaction chamber is maintained in the range of 80 to 200°C, and the reaction chamber is heated for 1 to 5 hours to remove moisture inside the reaction chamber.

[0012] For example, the solvent of step a is an aprotic solvent, and includes cycloheptane, cyclooctane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, ethylcyclohexane, diethylcyclohexane, propylcyclohexane, isopropylcyclohexane, dipropylcyclohexane, butylcyclohexane, tert-butylcyclohexane, methylcycloheptane and methylcyclooctane; octane, isooctane, nonane, isononane, decane, isodecane, undecane, dodecane, hexadecane and octadecane; Toluene, o-, m- and p-xylene, 1,3,5-trimethylbenzene (mesitylene), 1,2,4- and 1,2,3-trimethylbenzene, ethylbenzene, propylbenzene, isopropylbenzene, butylbenzene, isobutylbenzene, tert-butylbenzene and cyclohexylbenzene; naphthalene, decahydronaphthalene (decalin), 1- and 2-methylnaphthalene, 1- and 2-ethylnaphthalene; It may be one selected from among tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 1,4-dioxane, dibutyl ether, isoamyl ether, dihexyl ether, 1,2-dimethoxyethane; and combinations thereof.

[0013] For example, the solvent of step a may be provided to have a volume in the range of 50 to 80% of the total volume of the reaction chamber.

[0014] For example, the lithium raw material of step a may be one selected from lithium hydroxide (LiOH), lithium hydroxide monohydrate (LiOH·H2O), lithium carbonate (Li2CO3), and a combination thereof.

[0015] For example, the lithium sulfide production reaction of the above step b is as shown in the following <Formula 1>, and can be performed for 10 to 60 hours at a temperature in the reaction chamber in the range of 120 to 300°C and a pressure in the range of 0.01 to 5.0 bar.

[0016]

[0017] 2LiOH + H2S → Li2S + 2H2O <Equation 1>

[0018]

[0019] For example, the high-speed stirring in step b is performed at a stirring speed ranging from 1,000 to 2,000 rpm, so that the final obtained lithium sulfide average particle size (D50) can be controlled within a predetermined range.

[0020] For example, in the step b above, the solvent supplemented between reactions may be one selected from among a newly supplied solvent, a solvent recovered between processes, and a combination thereof.

[0021] For example, in the above step c, a gas flow can be generated in the lithium sulfide recovery unit to remove solvent and impurities and dry the lithium sulfide.

[0022] For example, the proportion of lithium raw material consumed by reaction through steps a to c may be 97.99% or more.

[0023] In addition, the present specification provides lithium sulfide manufactured according to the above method, having an average particle size (D50) in the range of 1 to 10 μm and a particle size of 1 to 14 m. 2 / g range of lithium sulfide.

[0024] For example, the lithium sulfide may have a carbon content of less than 0.5 wt% and a purity of 97.99% or more.

[0025] In addition, the present specification provides a lithium all-solid-state secondary battery including: a positive electrode; a negative electrode facing the positive electrode; and a sulfide-based solid electrolyte interposed between the positive electrode and the negative electrode and made of lithium sulfide.

[0026] For example, the above lithium all-solid-state secondary battery can be applied to one or more products selected from among electric vehicles (EVs), hybrid electric vehicles (HEVs), energy storage systems (ESSs), urban air mobility (UAMs), mobile devices, laptops, electronic devices, tablets, drones, robots, and home appliances.

[0027] According to the present invention, when producing lithium sulfide through a reaction between lithium raw material and hydrogen sulfide, the reaction is performed under relatively mild conditions compared to conventional techniques, eliminating the need for frequent repairs or replacement of the reactor and various piping due to corrosion and malfunction, thereby improving the economic efficiency of the process. Furthermore, by reusing the unreacted hydrogen sulfide and solvent from which moisture has been removed, process costs are reduced, ensuring economic feasibility in mass production.

[0028] Furthermore, moisture and water vapor generated during the lithium sulfide production reaction are effectively removed, preventing the reverse reaction into lithium hydroxide and promoting the forward reaction, enabling the production of high-quality lithium sulfide with high purity and yield. Furthermore, particle size can be controlled in micrometer units without a separate grinding chamber or grinding step, offering excellent convenience and mass production potential.

[0029] Figure 1 schematically illustrates each step of a method for producing lithium sulfide according to one embodiment of the present invention.

[0030] Figures 2 and 3 illustrate the results of XRD (X-Ray Diffraction) analysis and particle size analysis performed to confirm the presence of lithium sulfide prepared according to one embodiment and a comparative example of the present invention.

[0031] FIG. 4 is a schematic diagram showing an example of a lithium sulfide manufacturing device applicable to a lithium sulfide manufacturing method according to an embodiment of the present invention.

[0032] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. When designating components in each drawing, it should be noted that, where possible, identical components are given the same reference numerals, even if they appear in different drawings. Furthermore, when describing embodiments of the present invention, detailed descriptions of known components or functions will be omitted if they are deemed to hinder understanding of the embodiments of the present invention.

[0033]

[0034] Hereinafter, the lithium sulfide manufacturing method according to the present invention, the lithium sulfide manufactured thereby, and the lithium sulfide manufacturing device will be described in more detail.

[0035]

[0036] lithium sulfide manufacturing method

[0037] A method for producing lithium sulfide according to one embodiment of the present invention comprises: a) a step of supplying a lithium raw material into a reaction chamber equipped with a solvent; b) a step of supplying hydrogen sulfide (H2S) into the reaction chamber to cause a lithium sulfide (Li2S) production reaction, and simultaneously performing high-speed stirring to pulverize the product during the reaction; and c) a step of transferring the product obtained in step b to a lithium sulfide recovery unit to obtain lithium sulfide (see FIG. 1).

[0038]

[0039] First, lithium raw material is supplied into a reaction chamber equipped with a solvent (step a).

[0040] The reaction chamber is a chamber having a predetermined reaction space in which a lithium sulfide production reaction is performed, and lithium raw material and hydrogen sulfide react in the reaction space to synthesize lithium sulfide. The detailed configuration of the reaction chamber will be described later.

[0041] The solvent provided in the reaction chamber is a solvent used in a wet reaction, and may be an aprotic solvent, and specifically, cycloheptane, cyclooctane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, ethylcyclohexane, diethylcyclohexane, propylcyclohexane, isopropylcyclohexane, dipropylcyclohexane, butylcyclohexane, tert-butylcyclohexane, methylcycloheptane and methylcyclooctane; octane, isooctane, nonane, isononane, decane, isodecane, undecane, dodecane, hexadecane and octadecane; Toluene, o-, m- and p-xylene, 1,3,5-trimethylbenzene (mesitylene), 1,2,4- and 1,2,3-trimethylbenzene, ethylbenzene, propylbenzene, isopropylbenzene, butylbenzene, isobutylbenzene, tert-butylbenzene and cyclohexylbenzene; naphthalene, decahydronaphthalene (decalin), 1- and 2-methylnaphthalene, 1- and 2-ethylnaphthalene; It may be one selected from among tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 1,4-dioxane, dibutyl ether, isoamyl ether, dihexyl ether, 1,2-dimethoxyethane; and combinations thereof.

[0042] In the above step, the solvent may be provided to have a volume in the range of 50 to 80% based on the total volume of the reaction chamber. If the solvent is included in an amount less than the above volume range, there may be a problem in that the lithium sulfide particles synthesized during the lithium sulfide production reaction may stick to the wall of the reaction space or grow and become fixed. On the other hand, if the solvent exceeds the above volume range, the space for the inert gas or hydrogen sulfide gas (H2S) supplied to meet the pressure conditions required during the lithium sulfide production reaction may be reduced, making it difficult to control the pressure conditions, and the solvent may also flow back to another device configuration.

[0043] The lithium raw material of the present invention is a reactant that generates lithium sulfide by reacting with hydrogen sulfide (H2S) supplied in the step described below, and may be one selected from lithium hydroxide (LiOH), lithium hydroxide monohydrate (LiOH·H2O), lithium carbonate (Li2CO3), and combinations thereof. For example, the lithium raw material may be lithium hydroxide monohydrate (LiOH·H2O). In this case, since securing the raw material is easy and the cost is low, it may be more suitable for securing economic efficiency and mass production.

[0044]

[0045] After the above step a and before the step b described below, a step of removing moisture within the reaction chamber may be further included.

[0046] Specifically, the above step may be performed to prevent the reverse reaction between the lithium sulfide (Li2S) production reaction in step b, which will be described later, from being accelerated by removing moisture within the reaction chamber, thereby reducing the conversion rate into lithium sulfide. For example, the above step may be performed by heating the reaction space within the reaction chamber for 1 to 5 hours while maintaining a temperature range of 80 to 200°C, specifically 90 to 150°C, by the heating unit described later.

[0047] In the above step, stirring may be performed to selectively remove moisture within the reaction chamber while suppressing solvent vaporization as much as possible. For example, the stirring may be performed at a stirring speed ranging from 300 to 800 rpm. In addition, in the above step, an inert gas may be supplied by bubbling to ensure smooth moisture removal.

[0048]

[0049] Next, a process is included in which hydrogen sulfide (H2S) is supplied into the reaction chamber to cause a lithium sulfide (Li2S) production reaction, and high-speed stirring is performed simultaneously with the reaction to crush the product (step b).

[0050] The lithium raw material supplied in the above-described step a is synthesized into lithium sulfide (Li2S) through a wet reaction with hydrogen sulfide (H2S) gas supplied into the reaction chamber in step b under solvent conditions. When the lithium raw material is lithium hydroxide, the specific reaction formula may be as shown in the following <Formula 1>.

[0051]

[0052] 2LiOH + H2S → Li2S + 2H2O <Equation 1>

[0053]

[0054] The lithium sulfide production reaction according to one embodiment of the present invention may be performed at a temperature in the reaction chamber of 120 to 300°C, specifically 120 to 250°C, and more specifically 120 to 200°C, and the pressure may be performed at a pressure in the range of 0.01 to 5.0 bar, specifically 1.5 to 3.0 bar, and more specifically 2 to 2.5 bar. In addition, the reaction may be performed for 10 to 60 hours, and stirring may be performed between the reactions to promote the reaction.

[0055]

[0056] In addition, according to one embodiment of the present invention, step b may include a process of bubbling inert gas when the reaction reaches chemical equilibrium and then re-supplying hydrogen sulfide into the reaction chamber, and the inert gas bubbling and hydrogen sulfide re-supply process of step b may be repeated one or more times. Specifically, when hydrogen sulfide is supplied into the reaction chamber, a lithium sulfide production reaction proceeds, and a point comes where the rates of the forward and reverse reactions become equal during the reaction, thereby achieving chemical equilibrium. At this time, if the reaction is terminated as is, it may be difficult to obtain the desired level of lithium sulfide purity, and therefore, inert gas bubbling is supplied according to the present invention. The inert gas bubbling serves to discharge moisture remaining in the solvent and water vapor existing in the reaction chamber to the outside of the reaction chamber, thereby breaking the chemical equilibrium, so that the forward reaction can resume. At this time, if hydrogen sulfide is supplied into the reaction chamber again, the lithium sulfide production reaction proceeds again. Therefore, if the inert gas bubbling and hydrogen sulfide resupply process of step b above is repeated, the conversion rate of lithium raw material to lithium sulfide can be maximized.

[0057] Meanwhile, the inert gas may be supplied to one side or the bottom of the reaction chamber, and the bubbling supply of the inert gas may be performed for 1 to 5 hours per time, specifically 1 to 3 hours, but this may vary depending on various factors such as the amount of lithium raw material and the size of the reaction chamber. The inert gas according to one embodiment of the present invention may be one selected from nitrogen (N2), argon (Ar), helium (He), and a combination thereof, and may be nitrogen (N2) as an example. When nitrogen (N2) is used as the inert gas, it has the advantages of being inexpensive and easy to handle, without significantly affecting the lithium sulfide production reaction.

[0058]

[0059] Meanwhile, according to one embodiment of the present invention, a process for crushing a product by performing high-speed stirring during the lithium sulfide (Li2S) production reaction may be included. Specifically, the high-speed stirring may be performed by controlling the stirring speed within the range of 1,000 to 2,000 rpm, specifically 1,400 to 1,600 rpm, using a stirring member provided within the reaction chamber, thereby controlling the average particle size (D50) of the final lithium sulfide obtained within a predetermined range of several μm.

[0060] In this regard, Korean Patent Application No. 2021-0134601 (filed on October 12, 2021) discloses a method of mechanically crushing and pulverizing lithium sulfide by a method such as a ball milling or jet milling after obtaining the same, and conventionally, the particle size of lithium sulfide was generally controlled by crushing lithium sulfide in a separate space through the steps described above after finally obtaining the same. On the other hand, in the case of performing wet crushing by high-speed stirring together with the production of lithium sulfide under solvent conditions as in the present invention, unlike conventional methods, a separate crushing space or separate crushing step is not required, which is economical and also has the advantage of blocking dust generation.

[0061]

[0062] In this step, the hydrogen sulfide (H2S) supplied or re-supplied into the reaction chamber may be one selected from among hydrogen sulfide newly supplied from the hydrogen sulfide supply unit, unreacted hydrogen sulfide recovered between processes, and a combination thereof. Meanwhile, the unreacted hydrogen sulfide recovered between processes may be unreacted in step b, discharged outside the reaction chamber, and then re-supplied to the reaction chamber through a circulation process. The circulation of the unreacted hydrogen sulfide may mean passing through a condensation unit, a hydrogen sulfide re-supply unit, etc., which will be described later.

[0063] In addition, in this step, some of the solvent may be vaporized and discharged outside the reaction chamber. In this case, the solvent may be replenished between reactions, and in this case, the solvent may be one selected from among a newly supplied solvent, a solvent recovered between processes, and a combination thereof. Meanwhile, the solvent recovered between processes may be vaporized in step b, discharged outside the reaction chamber, and then re-supplied to the reaction chamber through a circulation process. The circulation of the solvent may mean passing through a condensation unit, a solvent re-supply unit, etc., which will be described later.

[0064]

[0065] Next, the product obtained in step b is transferred to a lithium sulfide recovery unit to obtain lithium sulfide (step c).

[0066] The above step may include generating a gaseous flow to remove solvent and impurities and dry the lithium sulfide.

[0067] The lithium sulfide recovery unit may include a filter reactor including at least one selected from a blower, an impeller, and a filter member (F), as described below, or a vacuum filter capable of performing vacuum drying.

[0068] Specifically, the process of removing solvent and impurities can be performed by a horizontal or vertical gas flow generated from a blower equipped in the filter reactor, and drying of lithium sulfide can be performed simultaneously in the process. The gas flow can be a flow of one inert gas selected from nitrogen (N2), argon (Ar), helium (He), and a combination thereof. Meanwhile, the gas flow can have a speed in the range of 1 to 10 kph. Meanwhile, the temperature of the lithium sulfide recovery unit in the process can have a range of 80 to 150°C, specifically, a range of 80 to 130°C.

[0069] Meanwhile, the ratio of lithium raw material consumed by reaction by steps a to c of the present invention may be 97.99% or more, specifically 98.99% or more, and more specifically 99.99% or more.

[0070]

[0071] According to the lithium sulfide manufacturing method of the present invention described above, when manufacturing lithium sulfide through a reaction between a lithium raw material and hydrogen sulfide, the reaction is performed under relatively mild conditions compared to conventional techniques, so frequent repairs or replacements due to corrosion and malfunction of the reactor and various piping are not required, thereby improving the economic efficiency of the process. In addition, since the unreacted hydrogen sulfide and solvent from which moisture has been removed are reused, the process cost is reduced, thereby ensuring economic efficiency in mass production.

[0072] Furthermore, moisture and water vapor generated during the lithium sulfide production reaction are effectively removed, preventing the reverse reaction into lithium hydroxide and promoting the forward reaction, enabling the production of high-quality lithium sulfide with high purity and yield. Furthermore, particle size can be controlled in micrometer units without a separate grinding chamber or grinding step, offering excellent convenience and mass production potential.

[0073]

[0074] lithium sulfide

[0075] Lithium sulfide (Li2S) manufactured according to one embodiment of the present invention has an average particle size (D50) in the range of 1 to 10 μm. In addition, the lithium sulfide (Li2S) has an average particle size (D50) in the range of 1 to 14 μm. 2 It can have a BET (Brunauer, Emmett, Teller Analysis) surface area in the / g range.

[0076] In addition, lithium sulfide manufactured according to an embodiment of the present invention has a carbon content of less than 0.5 wt%, specifically less than 0.3 wt%, and the carbon content may refer to a result value measured by a non-dispersive infrared (ND-IR) analysis method for the total carbon content in the finally obtained lithium sulfide. Meanwhile, the purity of the lithium sulfide finally obtained according to the present invention may be 97.99% or more, specifically 98.99% or more, and more specifically 99.99% or more, and the purity may be measured by an XRD semi-quantitative analysis method.

[0077]

[0078] Furthermore, according to an additional embodiment of the present invention, the lithium sulfide can be used as a key material in the manufacture of a sulfide-based solid electrolyte such as an argyrodite series or an LPS (Li-PS) series.

[0079] Specifically, a lithium all-solid-state secondary battery according to an embodiment of the present invention may include: a cathode; an anode facing the cathode; and a sulfide-based solid electrolyte made of lithium sulfide, interposed between the cathode and the anode. In addition, the lithium all-solid-state secondary battery may be applied to one or more product / technology fields selected from electric vehicles (EVs), hybrid electric vehicles (HEVs), energy storage systems (ESSs), urban air mobility (UAMs), mobile devices, laptops, electronic devices, tablets, drones, robots, and home appliances.

[0080]

[0081] lithium sulfide manufacturing equipment

[0082] Figure 4 is a schematic diagram showing an example of a lithium sulfide manufacturing device applicable to the lithium sulfide manufacturing method according to the present invention. Hereinafter, the manufacturing device will be described with reference to Figure 4.

[0083]

[0084] A lithium sulfide production device according to one embodiment of the present invention includes a reaction chamber (100), a heating unit (150), a hydrogen sulfide supply unit (200), a condensation unit (300), a hydrogen sulfide resupply unit (400), a solvent resupply unit (500), and a lithium sulfide recovery unit (600). Meanwhile, although not shown, a separately provided supply means, such as a circulation pump, may be used as a means for promoting material movement between each component within the production device.

[0085]

[0086] The reaction chamber (100) is a chamber having a predetermined reaction space in which a lithium sulfide production reaction is performed, and lithium raw material and hydrogen sulfide react in the reaction space to synthesize lithium sulfide (Li2S). The shape of the reaction chamber is not particularly limited as long as it has the predetermined reaction space. A solvent used for the wet reaction may be provided in the reaction space of the reaction chamber (100). As described above, the solvent may be an aprotic solvent, and the specific type is as described above.

[0087] Meanwhile, lithium raw material may be supplied to the reaction space of the reaction chamber along a lithium raw material supply line (10). The supply of lithium raw material may be performed by charging it into the reaction chamber all at once, or may be performed through a conveyor belt installed outside the reaction chamber (100) to implement an automated / semi-automated process. In addition, the lithium raw material supply line (10) may be installed vertically or inclined so that the lithium raw material is moved into the reaction chamber by gravity. In addition, the lithium raw material may be moved using a separately provided blowing means. A stirring member (110) may be installed inside the reaction chamber to promote the lithium sulfide production reaction or to crush the product, and the stirring member (110) may be, for example, a rotating disk, a rotary, a propeller, etc.

[0088]

[0089] The heating unit (150) may be provided in a form adjacent to or in contact with the reaction chamber to heat the predetermined reaction space. The heating unit (150) may be, for example, a heater, a heating wire, or an infrared heater mounted on the outer surface of the reaction chamber (100), and may perform heating so that the reaction space temperature is in the range of 120 to 300°C, specifically in the range of 120 to 250°C, and more specifically in the range of 120 to 200°C.

[0090] Meanwhile, in order for the lithium raw material and hydrogen sulfide to react smoothly, the temperature inside the reaction chamber must be sufficiently elevated. As shown in the above <Equation 1>, water (H2O) is generated as a by-product of the reaction between lithium hydroxide and hydrogen sulfide, which can cause a reverse reaction of the lithium sulfide production reaction and reduce the area of ​​the lithium raw material that reacts with hydrogen sulfide because it is located between lithium hydroxide particles or between solvents. Therefore, the reaction space is heated to a temperature of at least 120℃ or higher to remove moisture or water vapor, thereby promoting the forward reaction and obtaining high-purity lithium sulfide. However, since lithium hydroxide, as one of the lithium raw materials, has a melting point of 445℃, the temperature of the reaction space is preferably not higher than 445℃. In addition, since an excessive increase in the reaction temperature can cause corrosion of the reaction device and various piping, the heating needs to be performed within the above temperature range.

[0091] Meanwhile, as the temperature of the reaction space increases, there is a greater risk of corrosion of the inner surface of the reaction chamber (100) and various pipings due to hydrogen sulfide, so the reaction chamber (100) and various pipings may be manufactured from a material having strong heat resistance and corrosion resistance. For example, the reaction chamber (100) may be made of one material selected from the group consisting of Hastelloy, stainless steel (SUS), alumina, quartz, and combinations thereof, specifically, one material selected from the group consisting of Hastelloy X, stainless steel 304 (SUS 304), stainless steel 310 (SUS 310), stainless steel 316 (SUS 316), alumina, quartz, and combinations thereof. If the reaction chamber and various pipings have the above-mentioned materials and the temperature of the reaction space is maintained within the above-mentioned range, frequent repair or replacement of equipment such as the reaction chamber (100) and various pipings can be prevented, while sufficiently promoting the reaction between hydrogen sulfide and lithium raw materials, thereby obtaining high-purity lithium sulfide.

[0092]

[0093] The hydrogen sulfide supply unit (200) is provided to supply hydrogen sulfide to the reaction chamber (100). Specifically, the hydrogen sulfide supply unit (200) may be a device for supplying hydrogen sulfide to one side or the lower side of the reaction chamber. Meanwhile, a sparger or an inline-disperser (not shown) for bubbling supply of hydrogen sulfide may be provided in the hydrogen sulfide supply line (20) connecting the hydrogen sulfide supply unit (200) and the reaction chamber (100). The sparger and inline-disperser may be devices that mix the supplied fluids at high pressure, and these devices may be controlled to have an optimal pressure and temperature range so that hydrogen sulfide (H2S) is supplied into the reaction chamber in a bubbling state.

[0094] Hydrogen sulfide supplied into the reaction chamber along the hydrogen sulfide supply line (20) can be sprayed downward by the spray nozzle. When hydrogen sulfide is sprayed downward, the time that hydrogen sulfide (H2S) gas remains in the solvent increases, thereby increasing the efficiency of the lithium sulfide production reaction and reducing the proportion of unreacted hydrogen sulfide discharged outside the reaction chamber.

[0095]

[0096] The condenser (300) may be configured to selectively condense gas discharged from the reaction chamber (100) along the exhaust line (30), and a separate cooling means (not shown) may be provided for this purpose. For example, the condenser may be a condenser utilizing a heat exchange method. For example, if the temperature of the condenser is set to be less than 100°C, specifically less than 70°C, and more specifically less than 50°C, the water vapor and solvent discharged from the reaction chamber are liquefied, but unreacted hydrogen sulfide passes through the condenser in a gaseous state.

[0097]

[0098] The hydrogen sulfide resupply unit (400) may be a device for recovering unreacted hydrogen sulfide (H2S) that has passed through the condensation unit and supplying the recovered unreacted hydrogen sulfide to the reaction chamber (100) along the hydrogen sulfide resupply line (40). In addition, the hydrogen sulfide resupply unit (400) may include a moisture removal unit (not shown). Specifically, the unreacted hydrogen sulfide (H2S) recovered from the condensation unit may be supplied back to the reaction chamber (100) with moisture completely removed while passing through the hydrogen sulfide resupply unit, and recovering and resupplying the unreacted hydrogen sulfide in this way improves the economic efficiency of the process. Meanwhile, the moisture removal unit is not particularly limited as long as it can remove moisture / water vapor from the recovered unreacted hydrogen sulfide gas. For example, it may be a device configured to selectively liquefy and remove only water vapor by pressurizing the gas under strong pressure conditions. In this case, unlike the method of removing moisture through cooling, a separate heating process is not required before supplying the recovered unreacted hydrogen sulfide gas to the reaction chamber, which can be advantageous in terms of the economic feasibility and efficiency of the process.

[0099] The hydrogen sulfide resupply line (40) may be directly connected to the reaction chamber (100) or may be connected to the hydrogen sulfide supply line (20). If the hydrogen sulfide resupply line (40) is directly connected to the reaction chamber, the hydrogen sulfide resupply line (40) may be equipped with a sparger or an inline-disperser (not shown) for bubbling supply of hydrogen sulfide, similar to the hydrogen sulfide supply line (20) described above.

[0100]

[0101] The solvent resupply unit (500) is a device configuration that receives a mixture of solvent and water liquefied from the condensation unit (300), separates them based on the difference in boiling point or specific gravity, and then selectively recovers only the solvent. The solvent recovered from the solvent resupply unit (500) can be supplied back into the reaction chamber (100) along the solvent resupply line (50). Meanwhile, one or more solvent resupply units may be provided, and if there are two or more solvent resupply units, they may be provided in series or parallel form as needed. The solvent resupply unit (500) may be a Dean-Stark trap or an oil-water separator. Meanwhile, the water separated in the above process is removed along the water discharge line (WD).

[0102]

[0103] The lithium sulfide recovery unit (600) is a device configuration through which a product generated in the reaction chamber (100) is delivered, and the product can be delivered along the lithium sulfide recovery line (60). In the lithium sulfide recovery unit, a process for removing solvents and impurities and drying can be performed before obtaining the final lithium sulfide. Meanwhile, the lithium sulfide recovery unit is not particularly limited, but may have a chamber configuration having a shape such as a cylinder, a square, a rectangle, a cylinder, an inverted cone, etc. For example, the lithium sulfide recovery unit may include a filter reactor including at least one selected from a blower, an impeller, and a filter member (F), or a vacuum filter capable of performing vacuum drying.

[0104] A blower is a device installed at the side or top of a lithium sulfide recovery unit to generate a gas flow in a horizontal or vertical direction. The gas flow generated by the blower moves the solvent and impurities remaining on the surface of the lithium sulfide product toward the filter member to remove them. The gas supplied from the blower may be an inert gas as described above.

[0105] The impeller is provided to be able to move in the up / down / left / right directions within the lithium sulfide recovery unit, and may have at least one shape selected from a paddle, a propeller, and a turbine. Meanwhile, the impeller may be configured as a device that operates to promote the removal of impurities and drying of the product delivered to the lithium sulfide recovery unit.

[0106] The filter member (F) is configured to discharge the solvent and impurities separated from lithium sulfide to the outside as described above, and may be made of one material selected from among Hastelloy, stainless steel (SUS), and combinations thereof, specifically, one material selected from among Hastelloy X, stainless steel 304 (SUS 304), stainless steel 310 (SUS 310), stainless steel 316 (SUS 316), and combinations thereof. In addition, the filter member (F) may be a mesh filter that sieves particles having a particle size of 1 μm or more.

[0107]

[0108] The inert gas supply unit (700) is a device configuration for supplying an inert gas into the reaction chamber by bubbling it. For example, the inert gas can be supplied along an inert gas supply line (70) connected to the bottom of the reaction chamber. The inert gas can be one selected from nitrogen (N2), argon (Ar), helium (He), and a combination thereof. Meanwhile, the inert gas supply unit or the inert gas supply line can be equipped with a sparger or an inline-disperser (not shown) for bubbling supply. Meanwhile, the flow of the inert gas supplied by bubbling can be controlled to have a flow speed in the range of 1 to 10 kph.

[0109]

[0110] Example

[0111] The present invention is susceptible to various modifications and takes various forms. Specific embodiments are illustrated and described in detail below. However, this is not intended to limit the invention to any specific disclosed form, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0112]

[0113] Example 1

[0114] A cylindrical reaction chamber (100 ℓ) was prepared, and 28 kg (0.25 kmol) of an octane mixture as a solvent was introduced into the reaction chamber. Thereafter, 20 kg (0.48 kmol) of lithium hydroxide monohydrate (LiOH·H2O) was introduced into the reaction chamber, and nitrogen (N2) as an inert gas was introduced at a rate of 0.2 kph using a lower sparger, followed by reflux stirring for 2 hours. 8.6 kg of the water produced during this process was recovered / removed using an oil-water separator (corresponding to step a).

[0115] Then, hydrogen sulfide (H2S) was injected into the reaction chamber at a rate of 1.5 kph, and the reaction chamber was refluxed and stirred for 20 hours while maintaining the internal pressure of the reaction chamber at 2 bar and the temperature at 150℃. 8.25 kg of the water produced at this time was recovered using an oil-water separator, and after confirming that chemical equilibrium was achieved and no additional lithium sulfide was produced, the injection of hydrogen sulfide was stopped, the pressure in the reaction chamber was reduced to 0.01 bar, and nitrogen (N2) was bubbled using a lower sparger and injected at a rate of 1 kph while refluxing and stirring for 1 hour. Next, the nitrogen injection was stopped, and hydrogen sulfide (H2S) was injected again at a rate of 1.5 kph, and the reaction chamber was refluxed and stirred for 1 hour while maintaining the internal pressure of the reaction chamber at 2 bar and the temperature at 150℃. Meanwhile, the above-described series of processes of bubbling nitrogen (N2) and resupplying hydrogen sulfide (H2S) was repeated three times, and a stirring member was used to stir at high speed while performing the entire reaction, while maintaining a stirring speed of 1,400 rpm (corresponding to step b).

[0116] After the lithium sulfide production reaction was completed, the reaction chamber temperature was cooled to 80°C, filtered using a Nutsche filter, and dried under reduced pressure at 80°C in a glove box to obtain 9.71 kg (0.21 kmol) of lithium sulfide as a white solid (corresponding to step c).

[0117]

[0118] Comparative Example 1

[0119] The same procedure as in Example 1 was followed, except that high-speed stirring was not performed in step b.

[0120]

[0121] [Experiment. Lithium Sulfide Physical Properties Measurement Experiment]

[0122]

[0123] XRD measurement experiment

[0124] Lithium sulfide (Li2S) recovered according to the examples and comparative examples was prepared, and XRD measurement using CuKα rays was performed on each, and observation was performed focusing on the 2θ = 44.6 peak corresponding to lithium sulfide and the 2θ = 32.3 peak corresponding to lithium hydroxide. As shown in Fig. 2, Example 1 confirmed that the purity of lithium sulfide was 99.99% as a result of XRD semi-quantitative analysis.

[0125] Meanwhile, as shown in Fig. 3, Comparative Example 1 confirmed that the purity of lithium sulfide was 99.99% as a result of XRD semi-quantitative analysis.

[0126]

[0127] BET surface area measurement experiment

[0128] Lithium sulfide (Li2S) recovered according to the examples and comparative examples was prepared, and the specific surface area was measured using Nova 800 by the BET method using nitrogen gas. As a result, the lithium sulfide according to Example 1 had a specific surface area of ​​10.8 m 2 / g was confirmed.

[0129] Meanwhile, lithium sulfide according to comparative example 1 has a specific surface area of ​​9.5 m 2 / g was confirmed.

[0130]

[0131] Particle size analysis measurement experiment

[0132] Lithium sulfide (Li2S) recovered according to the examples and comparative examples was prepared, and particle size analysis was performed using a SALD-2300 device. As a result of the measurement, it was confirmed that the average particle size (D50) of Example 1 was 8.2 μm (see Fig. 2).

[0133] Meanwhile, it was confirmed that the average particle size (D50) of Comparative Example 1 was 107.3 ㎛ (see Fig. 3).

[0134]

[0135] The overall summary of the experimental results described above is as shown in Table 1 below.

[0136]

[0137] XRD semi-quantitative analysis results Lithium sulfide purity (%) BET specific surface area (m 2 / g)Average particle size (D50) (㎛)Example 199.9910.88.2Comparative example 199.999.5107.3

[0138]

[0139] Referring to the results in Table 1 above, when high-speed stirring is performed simultaneously during the lithium sulfide production reaction as in the embodiment of the present invention, it can be predicted that the desired lithium sulfide average particle size (D50) can be controlled by adjusting the stirring speed, and compared to a dry grinding method such as a jet mill, it is economical because a separate grinding space or grinding step is not required, and it also helps the safety of workers because it produces less dust.

[0140]

[0141] The above description is merely an illustrative illustration of the technical idea of ​​the present invention, and those skilled in the art will appreciate that various modifications and variations can be made without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the technical idea of ​​the present invention, and the scope of the technical idea of ​​the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted by the following claims, and all technical ideas within a scope equivalent thereto should be interpreted as being included in the scope of the rights of the present invention.

[0142]

[0143] Description of the symbol

[0144] 10: Lithium raw material supply line

[0145] 20: Hydrogen sulfide supply line 30: Exhaust line

[0146] 40: Hydrogen sulfide resupply line 50: Solvent resupply line

[0147] 60: Lithium sulfide recovery line 70: Inert gas supply line

[0148] WD: Water (H2O) discharge line

[0149] 100: Reaction chamber 110: Stirring member

[0150] 150: Heating section 200: Hydrogen sulfide supply section

[0151] 300: Condensation section 400: Hydrogen sulfide resupply section

[0152] 500: Solvent resupply unit 600: Lithium sulfide recovery unit

[0153] 700: Inert gas supply unit

[0154] F: Filter element

Claims

1. a) A step of supplying lithium raw material into a reaction chamber equipped with a solvent; b) a step including a process of supplying hydrogen sulfide (H2S) into a reaction chamber to cause a lithium sulfide (Li2S) production reaction, while simultaneously performing high-speed stirring to pulverize the product; and c) A method for producing lithium sulfide, comprising: a step of transferring the product obtained in step b to a lithium sulfide recovery unit to obtain lithium sulfide; 2. In paragraph 1, A method for producing lithium sulfide, further comprising: a step of removing moisture within the reaction chamber by heating for 1 to 5 hours while maintaining the temperature within the reaction chamber in the range of 80 to 200°C after the above step a and before the step b; 3. In paragraph 1, The solvent of the above step a is an aprotic solvent, and is selected from the group consisting of cycloheptane, cyclooctane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, ethylcyclohexane, diethylcyclohexane, propylcyclohexane, isopropylcyclohexane, dipropylcyclohexane, butylcyclohexane, tert-butylcyclohexane, methylcycloheptane and methylcyclooctane; octane, isooctane, nonane, isononane, decane, isodecane, undecane, dodecane, hexadecane and octadecane; Toluene, o-, m- and p-xylene, 1,3,5-trimethylbenzene (mesitylene), 1,2,4- and 1,2,3-trimethylbenzene, ethylbenzene, propylbenzene, isopropylbenzene, butylbenzene, isobutylbenzene, tert-butylbenzene and cyclohexylbenzene; naphthalene, decahydronaphthalene (decalin), 1- and 2-methylnaphthalene, 1- and 2-ethylnaphthalene; A method for producing lithium sulfide, wherein the lithium sulfide is selected from tetrahydrofuran, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 1,4-dioxane, dibutyl ether, isoamyl ether, dihexyl ether, 1,2-dimethoxyethane; and combinations thereof.

4. In paragraph 1, A method for producing lithium sulfide, wherein the solvent of step a is provided in a volume range of 50 to 80% of the total volume of the reaction chamber.

5. In paragraph 1, A method for producing lithium sulfide, wherein the lithium raw material of step a is one selected from lithium hydroxide (LiOH), lithium hydroxide monohydrate (LiOH·H2O), lithium carbonate (Li2CO3), and a combination thereof.

6. In paragraph 1, The lithium sulfide production reaction of the above step b is as shown in <Formula 1> below. A method for producing lithium sulfide, wherein the temperature in the reaction chamber is in the range of 120 to 300°C and the pressure is in the range of 0.01 to 5.0 bar, and the process is performed for 10 to 60 hours. 2LiOH + H2S → Li2S + 2H2O <Equation 1> 7. In paragraph 1, A method for producing lithium sulfide, wherein the high-speed stirring in step b is performed at a stirring speed ranging from 1,000 to 2,000 rpm, thereby controlling the average particle size (D50) of the lithium sulfide finally obtained within a predetermined range.

8. In paragraph 1, A method for producing lithium sulfide, wherein in the step b above, the solvent supplemented between reactions is one selected from among a newly supplied solvent, a solvent recovered between processes, and a combination thereof.

9. In paragraph 1, A method for producing lithium sulfide, wherein, in the above step c, a gas flow is generated in a lithium sulfide recovery unit to remove solvent and impurities and dry lithium sulfide.

10. In paragraph 1, A method for producing lithium sulfide, wherein the proportion of lithium raw materials consumed by reaction through steps a to c above is 97.99% or more.

11. Lithium sulfide manufactured according to the method of paragraph 1, having an average particle size (D50) in the range of 1 to 10 ㎛ and a particle diameter of 1 to 14 m 2 Lithium sulfide having a BET surface area in the / g range.

12. In paragraph 11, The above lithium sulfide has a carbon content of less than 0.5 wt% and a purity of 97.99% or more.

13. A lithium all-solid-state secondary battery comprising: a positive electrode; a negative electrode facing the positive electrode; and a sulfide-based solid electrolyte interposed between the positive electrode and the negative electrode and made of lithium sulfide according to claim 11.

14. In paragraph 13, The above lithium all-solid-state secondary battery is a lithium all-solid-state secondary battery applied to one or more products selected from among electric vehicles (EV), hybrid electric vehicles (HEV), energy storage systems (ESS), urban air mobility (UAM), mobile devices, laptops, electronic devices, tablets, drones, robots, and home appliances.

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