Preparation method of lithium sulfide

Abstract

According to the preparation method of the lithium sulfide, a solid sulfur layer, a catalyst layer and a lithium source layer are sequentially arranged in a reactor. And injecting reaction gas into the reactor along a single direction. Reaction gas sequentially passes through the solid sulfur layer, the catalyst layer and the lithium source layer, so that high-purity lithium sulfide can be effectively prepared.

Description

Technical Field

[0001] The present invention relates to a method for preparing lithium sulfide. More specifically, the present invention relates to a method for preparing high-purity lithium sulfide. Background Art

[0002] In recent years, secondary batteries have been widely used and developed as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptop computers, and vehicles such as hybrid vehicles and electric vehicles. Lithium secondary batteries, which are secondary batteries, have high operating voltage and energy density per unit weight, and are advantageous in charging speed and light weight, so lithium secondary batteries are actively developed and applied.

[0003] All-solid batteries using solid electrolytes in secondary batteries do not contain flammable liquid electrolytes, so they are safe. In addition, the energy density and life of all-solid batteries are higher than those of existing secondary batteries using liquid electrolytes. Due to the high energy density and long life characteristics, all-solid batteries are being actively developed in recent years.

[0004] Sulfide-based solid electrolytes have high lithium ion conductivity and are safe over a wide voltage range. Sulfide-based solid electrolytes exist in the form of Li2S-P2S5, Li2S-P2S5-LiCl, etc., and are prepared from lithium sulfide.

[0005] However, lithium sulfide cannot be produced from natural minerals and therefore needs to be produced through synthesis, which has problems in terms of production scale and price due to the synthesis process.

[0006] In the preparation process of lithium sulfide, when metallic lithium is used as a lithium source, there is a problem in terms of price, and when lithium hydroxide is used as a lithium source, the reaction efficiency may be reduced or side reactions may occur. In addition, hydrogen sulfide (H2S) as a sulfur source is toxic and therefore difficult to handle. Therefore, it is necessary to design a process for effectively preparing high-purity lithium sulfide. Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] A technical problem of the present invention relates to a method for effectively preparing high-purity lithium sulfide.

[0009] (II) Technical solution

[0010] In the method for preparing lithium sulfide according to the exemplary embodiment, a solid sulfur layer, a catalyst layer, and a lithium source layer are sequentially disposed in a reactor, and a reaction gas is injected into the reactor in a single direction.

[0011] In some embodiments, the reaction gas may be injected from one end of the reactor and sequentially pass through the solid sulfur layer, the catalyst layer, and the lithium source layer.

[0012] In some embodiments, the method may further include the step of collecting lithium sulfide from the other end of the reactor.

[0013] In some embodiments, the catalyst layer may include an active metal and a support.

[0014] In some embodiments, the support may include alumina, and the active metal may include at least one of Ni, Mo, Co, and W.

[0015] In some embodiments, the lithium source layer may include at least one of lithium hydroxide and lithium oxide.

[0016] In some embodiments, the lithium source contained in the lithium source layer may be a lithium source recovered from waste positive electrode materials of a lithium secondary battery.

[0017] In some embodiments, a ratio of the total number of moles of lithium atoms included in the lithium source layer to the total number of moles of sulfur atoms included in the solid sulfur layer may be 1 to 3.

[0018] In some embodiments, the reaction gas may include hydrogen or a mixed gas of hydrogen and nitrogen.

[0019] In some embodiments, the reaction gas may include a mixed gas of the hydrogen and nitrogen, and a volume ratio of the hydrogen in the mixed gas of the hydrogen and nitrogen may be greater than or equal to 30 volume % and less than 100 volume %.

[0020] In some embodiments, the reaction temperature in the reactor may be 300°C to 500°C.

[0021] In some embodiments, the reaction pressure in the reactor may be 0.1 bar to 5 bar.

[0022] In some embodiments, the reactor may include a first reactor and a second reactor.

[0023] In some embodiments, the solid sulfur layer and the catalyst layer can be disposed in the first reactor, the lithium source layer can be disposed in the second reactor, and the reaction gas can be supplied from the first reactor to the second reactor to sequentially contact the solid sulfur layer, the catalyst layer, and the lithium source layer.

[0024] In some embodiments, the reactors may include a first reactor, a second reactor, and a third reactor.

[0025] In some embodiments, the solid sulfur layer can be disposed in the first reactor, the catalyst layer can be disposed in the second reactor, the lithium source layer can be disposed in the third reactor, and the reaction gas can be supplied from the first reactor to the second reactor and the third reactor to sequentially contact the solid sulfur layer, the catalyst layer, and the lithium source layer.

[0026] (III) Beneficial effects

[0027] According to the above exemplary embodiment, a solid sulfur layer, a catalyst layer and a lithium source layer are sequentially arranged in one or more reactors, and a reaction gas is injected in a single direction so that the reaction gas sequentially contacts the above layers, thereby preparing high-purity lithium sulfide under mild conditions.

[0028] According to an exemplary embodiment, high-purity lithium sulfide can be obtained in an environmentally friendly and low-cost manner by using lithium hydroxide or lithium oxide generated in the treatment process of waste batteries as a lithium source.

[0029] According to an exemplary embodiment, solid sulfur can be obtained from byproducts produced after oil refining processing and is easy to control, so lithium sulfide can be prepared environmentally friendly and efficiently. In addition, lithium sulfide can be prepared without operators directly contacting harmful gases.

[0030] According to an exemplary embodiment, by including a catalyst layer, the purity of lithium sulfide may be increased without using an additional solvent or requiring an additional purification step. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic process sequence diagram for explaining a method for preparing lithium sulfide according to an exemplary embodiment.

[0032] Figure 2 is a schematic process flow chart for explaining a method for preparing lithium sulfide according to an exemplary embodiment.

[0033] Figure 3 and Figure 4 is a schematic process flow chart for illustrating a method for preparing lithium sulfide according to some exemplary embodiments.

[0034] Description of reference numerals:

[0035] 100: Reactor 100a: First reactor

[0036] 100b: second reactor 100c: third reactor

[0037] 110: solid sulfur layer 120: catalyst layer

[0038] 130: Lithium source layer 140: Gas supply unit

[0039] 150: Lithium sulfide collection department DETAILED DESCRIPTION

[0040] Embodiments of the present invention provide a method for preparing lithium sulfide from solid sulfur, a catalyst, and a lithium source with high purity and high yield.

[0041] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, these are merely exemplary embodiments, and the present invention is not limited to the specific embodiments exemplarily described.

[0042] Figure 1 is a schematic process sequence diagram for explaining a method for preparing lithium sulfide according to an exemplary embodiment. Figure 2 is a schematic process flow chart for explaining a method for preparing lithium sulfide according to an exemplary embodiment.

[0043] Reference Figure 1 , a solid sulfur layer, a catalyst layer and a lithium source layer can be formed sequentially inside the reactor (for example, S10 process).

[0044] Reference Figure 2 The reactor 100 may include a solid sulfur layer 110, a catalyst layer 120, and a lithium source layer 130. The reactor 100 may be disposed opposite to a gas supply part 140 and a lithium sulfide collection part 150.

[0045] The solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130 may be filled inside the reactor 100 to sequentially arrange the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130. According to the above arrangement order, the reaction gas may sequentially pass through the above layers. For example, the reaction gas may sequentially pass through the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130.

[0046] The form in which the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130 are arranged is not particularly limited. In some embodiments, the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130 may be arranged in separately divided spaces, respectively. In some embodiments, the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130 may be arranged in the same space in a state divided by a separator.

[0047] In an exemplary embodiment, one or more of the solid sulfur layer 110 , the catalyst layer 120 , and the lithium source layer 130 may exist in a state of contacting each other.

[0048] For example, the solid sulfur layer 110 and the catalyst layer 120 may exist in a contact state and the lithium source layer 130 may exist in a separated state, or the catalyst layer 120 and the lithium source layer 130 may exist in a contact state and the solid sulfur layer 110 may exist in a separated state.

[0049] In an exemplary embodiment, the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130 may exist in a state where the layers are separated from each other. In this case, the sequential contact of the reaction gas with the layers can be increased, so that the flow of the reaction gas can be promoted. Therefore, high-purity and high-yield lithium sulfide can be prepared in an economical and environmentally friendly manner.

[0050] After the solid sulfur layer 110 , the catalyst layer 120 , and the lithium source layer 130 are sequentially disposed, a reaction gas may be injected in a single direction (eg, S20 process).

[0051] In an exemplary embodiment, the reaction gas may be injected from one end of the reactor 100 and sequentially pass through the solid sulfur layer 110 , the catalyst layer 120 , and the lithium source layer 130 .

[0052] The reaction gas may be injected from the gas supply part 140 in one direction to generate a single-direction flow.

[0053] For example, when the reaction gas is injected from both directions of the reactor 100 (e.g., from the solid sulfur layer to the lithium source layer and from the lithium source layer to the solid sulfur layer), gas flow may not be generated or the gas residence time may be prolonged, and high-purity lithium sulfide may not be prepared.

[0054] When the reaction gas does not sequentially pass through the solid sulfur layer 110 , the catalyst layer 120 , and the lithium source layer 130 , lithium sulfide may not be prepared, or the purity of the prepared lithium sulfide may be significantly reduced.

[0055] For example, when the solid sulfur layer 110, the lithium source layer 130, and the catalyst layer 120 are arranged in this order and the reaction gas passes in this order, low-purity lithium sulfide may be produced, or impurities may be generated due to side reactions. Alternatively, for example, when the lithium source layer 130, the catalyst layer 120, and the solid sulfur layer 110 are arranged in this order and the reaction gas passes in this order, no reaction may occur, and lithium sulfide may not be produced.

[0056] For example, when the catalyst layer 120 is not provided, a reaction according to a reaction gas injection speed may not occur rapidly, and thus impurities may be generated.

[0057] The reaction gas is injected into the reactor 100 in a single direction, and a step of collecting lithium sulfide from the other end of the reactor 100 may be further included (eg, S30 process).

[0058] Since the reaction gas is injected into the reactor 100 in one direction, high-purity lithium sulfide can be obtained at the other end of the reactor 100 .

[0059] For example, the other end may exist in a state of being connected or separated from the reactor 100. For example, the other end may be connected to the reactor 100 through a pipe in a separate space. Alternatively, the other end may exist in a state of being connected and merged with the reactor 100.

[0060] The other end may include a lithium sulfide collecting portion 150. The lithium sulfide collecting portion 150 may be located on the opposite side of the gas supply portion 140, and the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130 disposed in the reactor 100 are located between the lithium sulfide collecting portion 150 and the gas supply portion 140.

[0061] In an exemplary embodiment, the lithium sulfide collecting part 150 may be located on the opposite side of the gas supply part 140, and lithium sulfide formed by gas phase synthesis by sequentially passing the reaction gas through the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130 may be obtained in the lithium sulfide collecting part 150. Since the reaction gas is injected in one direction, lithium sulfide may be obtained in the lithium sulfide collecting part 150 instead of obtaining lithium sulfide inside the reactor 100.

[0062] In an exemplary embodiment, a solid sulfur layer 110 may be provided inside the reactor 100 so that the reaction gas first passes through the solid sulfur layer 110. The solid sulfur contained in the solid sulfur layer 110 may use solid sulfur in all forms regardless of morphology, particle size, particle distribution, and the like.

[0063] The solid sulfur may be prepared, for example, in a desulfurization process of petroleum, crude oil, etc. For example, the desulfurization process may include: wet desulfurization by physical absorption treatment with sodium hydroxide, polyethylene glycol, potassium carbonate, ferrous chloride, etc.; dry desulfurization by chemical adsorption with an adsorbent such as silica gel; biological desulfurization using sulfur oxidizing bacteria such as Thiobacillus, etc.

[0064] By using solid sulfur produced as a byproduct in the desulfurization process, lithium sulfide can be produced in an environmentally friendly and low-cost manner. In addition, solid sulfur is easy to control and can be sequentially arranged in the reactor, and the generation of harmful gases during the preparation of lithium sulfide can be reduced.

[0065] In an exemplary embodiment, the catalyst layer 120 may include an active metal and a support for the active metal. For example, the catalyst layer 120 may include a support and an active metal supported in the support.

[0066] According to an exemplary embodiment, the catalyst layer 120 may include a hydroprocessing catalyst.

[0067] For example, the catalyst layer 120 may include alumina, magnesia, zirconia, silica, etc. as a carrier.

[0068] For example, the catalyst layer 120 may include one or more selected from Ni, Co, Fe, Mo, Cu, V, and W as active metals supported in a carrier.

[0069] In an exemplary embodiment, the support may include alumina, and the active metal may include at least one of Ni, Co, Mo, and W.

[0070] In an exemplary embodiment, the active metal may include NiMo, CoMo, or NiW.

[0071] When the catalyst includes at least one of Ni, Mo, Co and W as an active metal, the injected reaction gas contacts the catalyst layer 120, thereby promoting continuous flow. By promoting continuous reaction gas flow, the reaction gas can contact and react with the lithium source.

[0072] In an exemplary embodiment, the lithium source may include at least one of lithium hydroxide and lithium oxide.

[0073] The lithium hydroxide and lithium oxide may each be present alone in the lithium source layer 130, or may be present in a mixed state in the lithium source layer 130. For example, lithium hydroxide powder or lithium oxide powder may be used. When the lithium hydroxide, lithium oxide, or a combination thereof is included in the form of a powder, the average particle diameter of the powder may be 2 mm or less.

[0074] In an exemplary embodiment, the lithium source included in the lithium source layer 130 may use a lithium source recovered from waste positive electrode materials.

[0075] For example, the lithium source may be obtained by preparing a spent positive electrode active material mixture from the spent positive electrode material, reacting the spent positive electrode active material mixture with a reaction gas to form a primary precursor mixture, and then selectively recovering the lithium precursor to obtain the lithium source.

[0076] For example, the waste positive electrode material may include a positive electrode current collector (eg, aluminum (Al)) and a positive electrode active material layer, and the positive electrode active material layer may include a positive electrode active material, a conductive material, and a binder.

[0077] The conductive material may include carbon-based materials such as graphite, carbon black, graphene, carbon nanotubes, etc. The adhesive may include resin materials such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethylmethacrylate, etc.

[0078] For example, the waste positive electrode active material mixture can be generated by pulverization. For example, the waste positive electrode active material mixture can be heat-treated, and impurities contained in the waste positive electrode active material mixture can be removed or reduced by the heat treatment. Therefore, the purity of the primary precursor mixture can be improved, and the purity of the recovered lithium precursor can be improved.

[0079] For example, the reaction gas reacting with the spent positive electrode active material mixture may be a reducing gas. The primary precursor mixture prepared by reacting with the spent positive electrode active material mixture may include, for example, lithium hydroxide, lithium oxide, transition metals, transition metal oxides, and the like.

[0080] The primary precursor mixture may be washed with water to recover the lithium precursor, and the lithium precursor may be separated from the transition metal and the lithium precursor may be preferentially recovered by the water washing process. The lithium precursor may include lithium hydroxide or a hydrate thereof.

[0081] The recovered lithium precursor may be crystallized by a dry process or the like.

[0082] The lithium source may use materials recovered from waste positive electrode materials, so lithium sulfide may be prepared in an environmentally friendly manner.

[0083] In an exemplary embodiment, the reactor 100 may include a reactor into which a reaction gas may be injected in one direction. For example, the reactor 100 may include a tubular reactor, a tower reactor, a stirred tank reactor, a fluidized bed reactor, and the like.

[0084] In an exemplary embodiment, the reactor 100 may include a fluidized bed reactor. A reactor body having a diameter that increases gradually or gradually from a lower portion may be included to enhance mixing of gas and solids.

[0085] For example, when a fluidized bed reactor is used as the reactor 100 used in the process of preparing the lithium sulfide, lithium sources can be recovered from waste positive electrode materials and lithium sulfide can be prepared in the same reactor, thereby improving the preparation efficiency.

[0086] In addition, when a fluidized bed reactor is used, the lithium sulfide collecting part 150 may exist in a state of being combined with the fluidized bed reactor. The diameter of the fluidized bed reactor may gradually increase at a constant inclination angle in the direction from the gas supply part 140 to the lithium sulfide collecting part 150. As the diameter changes, the fluidization efficiency is improved, thereby increasing the yield of lithium sulfide.

[0087] In an exemplary embodiment, a ratio of the total number of moles of lithium atoms included in the lithium source layer 130 to the total number of moles of sulfur atoms included in the solid sulfur layer 110 may be 1 to 3.

[0088] In some embodiments, the ratio of the total moles of lithium atoms contained in the lithium source layer 130 to the total moles of sulfur atoms contained in the solid sulfur layer 110 may be 1.2 to 2.8, 1.4 to 2.6, or 1.5 to 2.5. Lithium sulfide may be prepared by making the molar ratio of lithium atoms to sulfur atoms within the above range.

[0089] The reaction gas injected into the reactor may include, for example, hydrogen, a mixed gas of hydrogen and nitrogen, argon, nitrogen, helium and other inert gases.

[0090] In an exemplary embodiment, the reaction gas may include hydrogen or a mixed gas of hydrogen and nitrogen. For example, the reaction gas may include hydrogen, hydrogen and nitrogen, hydrogen and argon, and the like.

[0091] Lithium sulfide can be prepared by sequentially passing the reaction gas containing hydrogen through the solid sulfur layer 110 , the catalyst layer 120 , and the lithium source layer 130 .

[0092] In an exemplary embodiment, the reaction gas may include a mixed gas of hydrogen and nitrogen, and a volume ratio of hydrogen in the mixed gas of hydrogen and nitrogen may be 30 volume % or more and less than 100 volume %.

[0093] When the volume ratio of hydrogen included in the reaction gas is less than 30%, the preparation time of lithium sulfide may increase, and thus the efficiency may decrease.

[0094] In an exemplary embodiment, the temperature of the step of injecting the reaction gas and performing the reaction may be 300° C. to 500° C. In some embodiments, the reaction temperature may be 300° C. to 450° C.

[0095] When the reaction temperature is lower than 300° C., even if the reaction gas contacts solid sulfur, the reaction may not be activated or the activity may be low, so that the yield of lithium sulfide may be low, and a side reaction may occur, so that the purity of lithium sulfide may be reduced. When the reaction temperature exceeds 500° C., a constant flow rate of the reaction gas cannot be maintained, so that the yield of lithium sulfide may be reduced, and the obtained lithium sulfide may solidify, so that the final yield may be reduced.

[0096] In an exemplary embodiment, the pressure of the step of injecting the reaction gas and performing the reaction may be 0.1 bar to 5 bar.

[0097] The reaction pressure can be maintained at a level similar to atmospheric pressure, or can be maintained at a level slightly higher than atmospheric pressure depending on the amount of reaction gas injected. In some embodiments, the reaction pressure can be 0.5 bar to 4 bar, 1 bar to 3 bar. Within the above pressure range, lithium sulfide can be prepared with high purity.

[0098] Figure 3 and Figure 4 is a schematic process flow diagram for illustrating a method for preparing lithium sulfide according to some embodiments.

[0099] Reference Figure 3 , the reactor 100 may include a first reactor 100a and a second reactor 100b. Figure 4 , the reactor may include a first reactor 100a, a second reactor 100b and a third reactor 100c.

[0100] The first reactor 100a, the second reactor 100b, and the third reactor 100c may be the same as or different from each other, and may be the same as the reactors described above.

[0101] The first reactor 100a may be connected to the gas supply part 140, and the second reactor 100b or the third reactor 100c may be connected to the lithium sulfide collecting part 150. The first reactor 100a, the second reactor 100b, and the third reactor 100c may be connected to each other.

[0102] For example, the first reactor 100a may be connected to the second reactor 100b, and the second reactor 100b may be connected to the third reactor 100c.

[0103] The connection method of the first reactor 100a, the second reactor 100b, and the third reactor 100c is not particularly limited, and may include all connection methods within a range that does not expose the reaction gas, reactants, etc. and does not cause a change in the reaction.

[0104] The first reactor 100a, the second reactor 100b, and the third reactor 100c may be connected to each other so that the reaction gas supplied to the first reactor 100a may be supplied to the second reactor 100b and / or the third reactor 100c.

[0105] The layers included in the first reactor 100a, the second reactor 100b, and the third reactor 100c may be arranged in the same direction. The reaction gas may be supplied to the first reactor 100a in a single direction through the gas supply unit 140. The reaction gas may be supplied in a direction toward the second reactor 100b or the third reactor 100c connected to the first reactor 100a, so that a single direction flow of the reaction gas may be formed from the first reactor 100a to the second reactor 100b or the third reactor 100c.

[0106] In an exemplary embodiment, the solid sulfur layer 110 and the catalyst layer 120 may be disposed in the first reactor 100a, and the lithium source layer 130 may be disposed in the second reactor 100b.

[0107] In an exemplary embodiment, the solid sulfur layer 110 may be disposed in the first reactor 100a, and the catalyst layer 120 and the lithium source layer 130 may be disposed in the second reactor 100b.

[0108] For example, the solid sulfur layer 110 and the catalyst layer 120 in the first reactor 100 a and the catalyst layer 120 and the lithium source layer 130 in the second reactor 100 b may be disposed in a state of being in contact with or spaced apart from each other.

[0109] After the above-mentioned layers are provided, a reaction gas may be supplied so that the reaction gas sequentially contacts the solid sulfur layer 110 , the catalyst layer 120 , and the lithium source layer 130 .

[0110] In an exemplary embodiment, the solid sulfur layer 110 may be disposed in the first reactor 100a, the catalyst layer 120 may be disposed in the second reactor 100b, and the lithium source layer 130 may be disposed in the third reactor 100c.

[0111] Even if the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130 are respectively present in physically separated reactors, lithium sulfide can be efficiently prepared according to a single direction flow of reaction gas without generating impurities.

[0112] In an exemplary embodiment, the lithium sulfide obtained in the lithium sulfide collecting part 150 may have high purity even without an additional purification step. Since the reaction gas is injected in a single direction and passes through the catalyst layer 120 located between the solid sulfur layer 110 and the lithium source layer 130, high-purity (e.g., 95% or more, 98% or more, 99% or more) lithium sulfide may be prepared even without a purification step.

[0113] In an exemplary embodiment, no solvent may be used when providing the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130. For example, the solid sulfur layer 110, the catalyst layer 120, and the lithium source layer 130 may not contain a solvent. For example, organic solvents such as isopropanol, hexane, toluene, dimethylformamide, N-methylcaprolactam, and N-methylpyrrolidone may not be used. Therefore, an additional residual solvent treatment process may not be included after the lithium sulfide is prepared. Since no organic solvent is used in the preparation process, lithium sulfide can be prepared in an environmentally friendly manner.

[0114] Below, specific experimental examples are proposed to help understand the present invention, but this is only used to illustrate the present invention and is not used to limit the scope of rights. Various changes and modifications can be made to the embodiments within the scope of the present invention and the technical idea, which is obvious to those skilled in the art, and these variations and modifications also fall within the scope of rights.

[0115] Example 1

[0116] Solid sulfur, catalyst (active metal: NiMo / carrier: Al2O3) and lithium hydroxide monohydrate (LiOH·H2O) are sequentially filled in the reactor. Hydrogen (100% by volume) is injected into the reactor so that the hydrogen contacts the solid sulfur layer, the NiMo / Al2O3 catalyst layer and the lithium hydroxide layer in sequence. While injecting hydrogen, the reaction pressure is maintained at 2 bar and the reaction temperature is maintained at 400°C for 5 hours. Afterwards, the reactor is moved to a glove box and the product located at the top is separated to obtain lithium sulfide.

[0117] Example 2

[0118] The reaction was carried out by the same process as in Example 1, except that the reaction temperature was 350°C.

[0119] Example 3

[0120] The reaction was carried out by the same process as in Example 1, except that the reaction temperature was 300°C.

[0121] Example 4

[0122] The reaction was performed by the same process as in Example 1, except that a mixed gas of hydrogen (50 volume %) and nitrogen (50 volume %) was used as the reaction gas.

[0123] Comparative Example 1

[0124] The reaction is carried out by the same process as in Example 1, except that lithium hydroxide, NiMo / Al2O3 catalyst and solid sulfur are filled in the reactor in this order so that the reaction gas contacts the lithium hydroxide layer, the catalyst layer and the solid sulfur layer in sequence.

[0125] Comparative Example 2

[0126] The reaction was carried out by the same process as in Example 1, except that only solid sulfur and lithium hydroxide were used except for the catalyst.

[0127] Comparative Example 3

[0128] The reaction was carried out by the same process as in Example 1, except that the reaction temperature was 120°C.

[0129] Comparative Example 4

[0130] The reaction was carried out by the same process as in Example 1, except that the reaction temperature was 250°C.

[0131] Comparative Example 5

[0132] The reaction was carried out by the same process as in Example 1, except that the reaction temperature was 600°C.

[0133] Experimental example

[0134] The products obtained in the above examples and comparative examples were subjected to X-ray diffraction (XRD) measurement, and their crystal structures were analyzed by Rietveld refinement.

[0135] The analysis results are collectively recorded in Table 1 below.

[0136] [Table 1]

[0137]

[0138] Referring to Table 1, according to the embodiment, lithium sulfide was obtained by contacting the reaction gas with the solid sulfur layer, the catalyst layer, and the lithium hydroxide layer in sequence. In addition, high-purity lithium sulfide was obtained within the reaction temperature range of 300°C to 450°C.

[0139] In Comparative Example 1 where the reaction gas did not sequentially contact the solid sulfur layer, the catalyst layer, and the lithium hydroxide layer, no reaction occurred. In Comparative Example 2 where no catalyst was used, although lithium sulfide was produced, the purity was reduced and a lithium compound (H2S2O4) was generated as a by-product.

[0140] In Comparative Example 3 where the reaction temperature was low, almost no reaction occurred, so less than 20% of lithium sulfide was produced. In Comparative Example 4 where the reaction temperature was higher than that of Comparative Example 3 but the reaction temperature was lower than 300° C., less than 75% of lithium sulfide was produced. In Comparative Example 5 where the reaction temperature was high, although more than 90% of lithium sulfide was produced, lithium sulfide solidified in the lithium sulfide collection section, so loss occurred during the lithium sulfide recovery process. In addition, it was confirmed that lithium hydroxide remained unreacted due to the high reaction temperature.

Claims

1. A method for preparing lithium sulfide, comprising the following steps: A solid sulfur layer, a catalyst layer and a lithium source layer are sequentially arranged in a reactor; as well as The reaction gas is injected into the reactor in a single direction.

2. The method for preparing lithium sulfide according to claim 1, wherein: The reaction gas is injected from one end of the reactor and sequentially passes through the solid sulfur layer, the catalyst layer, and the lithium source layer.

3. The method for preparing lithium sulfide according to claim 1, wherein: The method further comprises the step of collecting lithium sulfide from the other end of the reactor.

4. The method for preparing lithium sulfide according to claim 1, wherein: The catalyst layer includes an active metal and a support.

5. The method for preparing lithium sulfide according to claim 4, wherein: The support includes alumina, and the active metal includes at least one of Ni, Mo, Co, and W.

6. The method for preparing lithium sulfide according to claim 1, wherein: The lithium source layer includes at least one of lithium hydroxide and lithium oxide.

7. The method for preparing lithium sulfide according to claim 6, wherein: The lithium source contained in the lithium source layer is a lithium source recovered from waste positive electrode materials of lithium secondary batteries.

8. The method for preparing lithium sulfide according to claim 1, wherein: The ratio of the total number of moles of lithium atoms included in the lithium source layer to the total number of moles of sulfur atoms included in the solid sulfur layer is 1 to 3.

9. The method for preparing lithium sulfide according to claim 1, wherein: The reaction gas includes hydrogen or a mixed gas of hydrogen and nitrogen.

10. The method for preparing lithium sulfide according to claim 1, wherein: The reaction gas includes a mixed gas of hydrogen and nitrogen, and a volume ratio of hydrogen in the mixed gas of hydrogen and nitrogen is greater than or equal to 30 volume % and less than 100 volume %.

11. The method for preparing lithium sulfide according to claim 1, wherein: The reaction temperature in the reactor is 300°C to 500°C.

12. The method for preparing lithium sulfide according to claim 1, wherein: The reaction pressure in the reactor is 0.1 bar to 5 bar.

13. The method for preparing lithium sulfide according to claim 1, wherein: The reactor includes a first reactor and a second reactor.

14. The method for preparing lithium sulfide according to claim 13, wherein: The solid sulfur layer and the catalyst layer are arranged in the first reactor, and the lithium source layer is arranged in the second reactor. The reaction gas is supplied from the first reactor to the second reactor to sequentially contact the solid sulfur layer, the catalyst layer, and the lithium source layer.

15. The method for preparing lithium sulfide according to claim 1, wherein: The reactor includes a first reactor, a second reactor and a third reactor.

16. The method for preparing lithium sulfide according to claim 15, wherein: The solid sulfur layer is disposed in the first reactor, the catalyst layer is disposed in the second reactor, and the lithium source layer is disposed in the third reactor. The reaction gas is supplied from the first reactor to the second reactor and the third reactor to sequentially contact the solid sulfur layer, the catalyst layer, and the lithium source layer.

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