Precursor for producing lithium sulfide and lithium sulfide powder

Abstract

The present invention relates to a method for producing lithium sulfide, which includes the steps of mixing a carbon raw material and a lithium compound to produce a lithium-carbon compound, filtering a solution obtained by mixing the lithium-carbon compound and a solvent, spray-drying the filtrate at a temperature of 110 to 160°C in an inert loop structure, and heat-treating the spray-dried product, thereby producing lithium sulfide having an oxygen content of less than 2.8%.

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state electrolyte, and more particularly to a precursor for producing lithium sulfide and a lithium sulfide powder for an all-solid-state electrolyte. [Background technology]

[0002] Secondary batteries are widely used in a wide range of devices, from small electronic devices such as mobile phones and laptops to large devices such as electric vehicles (EVs) and energy storage systems (ESSs). As the application of secondary batteries expands to all areas of life, there is a growing demand for them to have not only high energy density and long life, but also stability.

[0003] Conventionally, most of the electrolytes used in lithium secondary batteries have been liquid electrolytes using organic solvents, but these liquid electrolytes have required strict packaging due to risks such as leakage and fire, and this strict packaging has limited the ability to increase energy density beyond a certain level. This has led to the need for all-solid-state batteries that use inorganic solid electrolytes instead of organic liquid electrolytes.

[0004] The all-solid-state battery eliminates the need for organic solvents, unlike liquid electrolytes, allowing for safe battery cell fabrication. Furthermore, inorganic solid electrolytes are stable and do not decompose over a wide voltage range, making them suitable for use as high-voltage electrode materials.

[0005] Solid electrolytes are classified into oxide-based and sulfide-based solid electrolytes, and sulfide-based solid electrolytes are characterized by higher ionic conductivity than oxide-based solid electrolytes. The main raw material for sulfide-based solid electrolytes is lithium sulfide (LiS). LiS can be synthesized using a high-energy ball mill, a wet plasma process, or a wet / dry method using lithium metal. However, the above methods have problems with kinetic control, high costs of starting materials, high process costs, and environmental issues, making commercialization difficult.

[0006] In contrast, the carbonthermal reduction method has the advantage of not using toxic H2S gas and instead using environmentally friendly, low-cost Li2SO4. However, since the extraction solvent must be used again after the heat treatment in the solid-phase heat treatment reduction reaction step, product purity control issues must be resolved through the management of the physical properties of the extraction solution, the extraction solution drying step, heat treatment, or crystallization step.

[0007] In particular, since the physical properties of the dried product vary depending on the drying method of the extract solution, an appropriate drying method for the extract solution is a key factor for obtaining high-quality lithium sulfide. Therefore, there is a need for a method for synthesizing lithium sulfide by controlling the drying method of the extract solution in which lithium sulfide is dissolved. Summary of the Invention [Problem to be solved by the invention]

[0008] The technical problem to be solved by the present invention is to provide a lithium sulfide precursor that can be used to produce high-purity lithium sulfide powder.

[0009] Another technical problem to be solved by the present invention is to provide lithium sulfide powder, which is a high-purity sulfide-based solid electrolyte raw material. [Means for solving the problem]

[0010] The precursor for preparing lithium sulfide powder according to one embodiment of the present invention relates to a precursor used for preparing lithium sulfide powder, has a hollow shape, and can satisfy the following formula 1: <Expression 1> (Dmax-Dmin) / D50≦15 (In the above formula 1, Dmax, Dmin, and D50 respectively mean the maximum particle size, the minimum particle size, and the particle size when particles are accumulated up to 50% by volume.)

[0011] In one embodiment, the hollow shape may have a hemispherical shape. In one embodiment, the standard deviation (STD DEV) of the particle size may be 11.0 or less.

[0012] In one embodiment, the precursor has a wave number of 2,600 to 3,250 cm in Raman analysis. -1 The first peak appears at a wave number of 2,500 to 2,600 cm -1 The second peak appears at wavenumbers 850 to 1,500 cm -1 In one embodiment, the first peak may be a peak of EtOH, the second peak may be a peak of LiSH, and the third peak may be a peak of LiOEt.

[0013] In one embodiment, the Dmax may be in the range of 10 to 100 μm. In one embodiment, the Dmin may be in the range of 0.1 to 2.5 μm. In one embodiment, the formula 1 may be 11.30 or less.

[0014] According to another embodiment of the present invention, the lithium sulfide powder for an all-solid-state electrolyte is manufactured from a hollow-shaped precursor for manufacturing lithium sulfide powder, and may contain any one of lithium sulfide (LiS) and lithium oxide (LiO), lithium carbonate (LiCO3), and lithium sulfide (LiSO4) as impurities, and may have an oxygen content of less than 2.8%. In one embodiment, the impurities may be free of lithium carbonate (LiCO3) and lithium sulfide (LiSO4), except for lithium oxide (LiO).

[0015] In one embodiment, the lithium sulfide powder can satisfy the following formula 2: <Expression 2> [Li2O] × oxygen content ≦ 5.0 (In the formula 2, [Li2O] means the content of lithium oxide in the lithium sulfide powder.)

[0016] In one embodiment, the formula 2 may be 2.5 or less. In one embodiment, the formula 2 may be 0.64 to 2.11. In one embodiment, the lithium oxide (Li2O) may satisfy 1.6% or less by weight. [Effects of the Invention]

[0017] The lithium sulfide powder according to an embodiment of the present invention provides a precursor, which is a raw material for a high-purity sulfide-based solid electrolyte, by controlling the drying method of the extraction solution in which lithium sulfide is dissolved.

[0018] Another embodiment of the present invention provides a high purity lithium sulfide powder produced from a precursor having the above-mentioned advantages. [Brief explanation of the drawings]

[0019] [Figure 1a] Figures 1a and 1b show the XRD peak values ​​of lithium sulfide in the dry form.

[0020] [Figure 1b]Figures 1a and 1b show the XRD peak values ​​of lithium sulfide in the dry form.

[0021] [Figure 2a] 2a to 2c are SEM photographs of Example 2 at different magnifications (×300, ×1K) and a particle size distribution graph.

[0022] [Figure 2b] 2a to 2c are SEM photographs of Example 2 at different magnifications (×300, ×1K) and a particle size distribution graph.

[0023] [Figure 2c] 2a to 2c are SEM photographs of Example 2 at different magnifications (×300, ×1K) and a particle size distribution graph.

[0024] [Figure 2d] 2d to 2g are SEM photographs of Example 3 at different magnifications (×100, ×300, ×1K) and a particle size distribution graph.

[0025] [Figure 2e] 2d to 2g are SEM photographs of Example 3 at different magnifications (×100, ×300, ×1K) and a particle size distribution graph.

[0026] [Figure 2f] 2d to 2g are SEM photographs of Example 3 at different magnifications (×100, ×300, ×1K) and a particle size distribution graph.

[0027] [Figure 2g] 2d to 2g are SEM photographs of Example 3 at different magnifications (×100, ×300, ×1K) and a particle size distribution graph.

[0028] [Figure 3] 1 shows the Raman characteristics of powder obtained by drying the filtered material according to a manufacturing method of an example of the present invention.

[0029] [Figure 4a]4a to 4f show the concentrations of gases generated during thermal treatment of a spray-dried product according to one embodiment of the present invention.

[0030] [Figure 4b] 4a to 4f show the concentrations of gases generated during thermal treatment of a spray-dried product according to one embodiment of the present invention.

[0031] [Figure 4c] 4a to 4f show the concentrations of gases generated during thermal treatment of a spray-dried product according to one embodiment of the present invention.

[0032] [Figure 4d] 4a to 4f show the concentrations of gases generated during thermal treatment of a spray-dried product according to one embodiment of the present invention.

[0033] [Figure 4e] 4a to 4f show the concentrations of gases generated during thermal treatment of a spray-dried product according to one embodiment of the present invention.

[0034] [Figure 4f] 4a to 4f show the concentrations of gases generated during thermal treatment of a spray-dried product according to one embodiment of the present invention.

[0035] [Figure 5a] 5a and 5b are diagrams illustrating the reaction process with and without an inert loop structure in the drying step.

[0036] [Figure 5b] 5a and 5b are diagrams illustrating the reaction process with and without an inert loop structure in the drying step.

[0037] [Figure 6a] 6a and 6b show XRD peaks obtained when LiS was synthesized by controlling the drying temperature during spraying and drying of filtered water in accordance with an embodiment of the present invention and a comparative example, followed by a final heat treatment after varying the rapid heat treatment temperature.

[0038] [Figure 6b] 6a and 6b show XRD peaks obtained when LiS was synthesized by controlling the drying temperature during spraying and drying of filtered water in accordance with an embodiment of the present invention and a comparative example, followed by a final heat treatment after varying the rapid heat treatment temperature.

[0039] [Figure 7a] 7a and 7b show XRD peaks of a high-concentration filtrate during heat treatment after spray drying, in which the concentration of the filtrate is controlled when spraying and drying the filtrate according to an embodiment of the present invention.

[0040] [Figure 7b] 7a and 7b show XRD peaks of a high-concentration filtrate during heat treatment after spray drying, in which the concentration of the filtrate is controlled when spraying and drying the filtrate according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0041] Terms such as "first," "second," and "third" are used to describe various parts, components, regions, layers, and / or sections, but are not limited thereto. These terms are used only to distinguish one part, component, region, layer, or section from another part, component, region, layer, or section. Thus, a first part, component, region, layer, or section described below can be referred to as a second part, component, region, layer, or section without departing from the scope of the present invention.

[0042] The terminology used herein is for the purpose of referring to particular embodiments and is not intended to limit the invention. As used herein, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. As used herein, the term "comprises" refers to the inclusion of certain properties, regions, integers, steps, operations, elements, and / or components, and does not exclude the presence or addition of other properties, regions, integers, steps, operations, elements, and / or components.

[0043] When a part is described as being "on" or "above" another part, it may be exactly on or above the other part, or it may have other parts between them. In contrast, when a part is referred to as being "on" another part, there are no other parts between them.

[0044] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by a person of ordinary skill in the art to which this invention belongs. Terms defined in commonly used dictionaries are additionally interpreted to have a meaning consistent with the relevant technical literature and the presently disclosed content, and are not interpreted in an ideal or very formal sense unless defined. Also, unless otherwise specified, % means % by weight, and 1 ppm is 0.0001% by weight.

[0045] The present invention will now be described in detail with reference to exemplary embodiments so that those skilled in the art can easily implement the present invention. However, the present invention may be embodied in many different forms and is not limited to the exemplary embodiments set forth herein.

[0046] According to an embodiment of the present invention, a precursor for producing lithium sulfide has a hollow shape. The precursor for producing lithium is a spray produced through spray drying in a process for producing lithium sulfide, which will be described later.

[0047] The hollow shape refers to a shape with an empty space inside, and the precursor for producing lithium sulfide has a hollow shape. The hollow shape of the precursor is a characteristic that is exhibited by the evaporation of ethanol during the spray drying process. The hollow shape of the precursor has the advantage of ensuring uniformity of the interior and exterior of the particles during heat treatment.

[0048] In one embodiment, the hollow shape may have a hemispherical shape, which is advantageous for mixing with other particles added to control physical properties during heat treatment.

[0049] In one embodiment, the precursor for preparing lithium sulfide may satisfy the following formula 1: <Expression 1> (Dmax-Dmin) / D50≦15 (In the above formula 1, Dmax, Dmin, and D50 respectively mean the maximum particle size, the minimum particle size, and the particle size when particles are accumulated up to 50% by volume.)

[0050] In this specification, particle size D0.9 means the particle size when particles of active material having various particle sizes distributed such as 0.1, 0.2, 0.3...3, 5, 7...10, 20, 30 μm are accumulated to 0.9% by volume, D10 means the particle size when particles are accumulated to 10% by volume, D50 particle size means the particle size when particles are accumulated to 50% by volume, D6 particle size means the particle size when particles are accumulated to 6% by volume, D95 means the particle size when particles are accumulated to 95% by volume, D min is the minimum particle size, D max means the maximum particle size.

[0051] The formula 1 is an index showing the degree of uniformity in the particle distribution of the precursor. The formula 1 may be 15 or less, specifically, 11.30 or less.

[0052] By satisfying the value of Equation 1, it is possible to obtain advantages that the particle distribution is uniform, the reaction during heat treatment is uniform, and the quality of lithium sulfide can be ensured with little deviation. If the value of Equation 1 exceeds the above range, the deviation of the quality of lithium sulfide may become large. To prevent this, it is necessary to ensure the uniformity by additionally grinding the obtained lithium sulfide precursor, which may result in a problem of reduced processability.

[0053] In one embodiment, the standard deviation (STD DEV) of the precursor particle size may be 11.0 or less. Specifically, the standard deviation may be 9.2 or less. When the standard deviation satisfies the above range, as described above, it is possible to ensure a uniform particle distribution, a uniform reaction during heat treatment, and quality of lithium sulfide with little deviation.

[0054] In one embodiment, the Dmax of the precursor may be in the range of 10 to 100 μm, specifically, in the range of 12.82 to 66.84 μm.

[0055] In one embodiment, the Dmin of the precursor may be in the range of 0.1 to 2.5 μm, specifically, in the range of 0.12 to 1.24 μm.

[0056] In one embodiment, the precursor has a wave number of 2,600 to 3,250 cm in Raman analysis. -1 The first peak appears at a wave number of 2,500 to 2,600 cm -1 The second peak appears at 850-1,500 cm -1 The first peak may be a peak of EtOH, the second peak may be a peak of LiSH, and the third peak may be a peak of LiOEt.

[0057] In the case of the precursor of the present invention, when only LiOET is contained, there is a problem that LiS conversion is low and it may be converted to other impurities (LiCO3, Li2SO4). On the other hand, when only LiSH is contained, there is a problem that when H2S is released in the reaction according to the following reaction formula, S loss continues and the yield of Li2S decreases. [Reaction scheme] LiSH+LiSH→Li2S+H2S↑

[0058] As a result, the precursor simultaneously contains the first peak, the second peak, and the third peak, which has the advantage of preventing sulfur loss and enabling the production of high-purity lithium sulfide as described below. Specifically, the precursor simultaneously contains the first peak, the second peak, and the third peak, which satisfies the following reaction formula, enabling the production of high-purity lithium sulfide. [Reaction scheme] LiSH+LiOEt→Li2S+EtOH

[0059] The lithium sulfide powder according to another embodiment of the present invention relates to a lithium sulfide powder for an all-solid-state electrolyte, and includes lithium sulfide (LiS) and at least one impurity selected from lithium oxide (LiO), lithium carbonate (LiCO3), and lithium sulfate (LiSO4). High-purity lithium sulfide powder can contain impurities such as lithium oxide (LiO), lithium carbonate (LiCO3), or lithium sulfate (LiSO4) by undergoing a heat treatment process.

[0060] In one embodiment, the oxygen content in the whole powder is less than 2.8%. Specifically, the oxygen content may be 1.3 to 1.6%, more specifically, 1.32 to 1.32 to 1.60%.

[0061] If the oxygen content exceeds the above range, there is a problem that lithium conductivity is reduced when synthesizing argyrodite using LiS, and there is also a problem that it is affected by the ratio of impurities such as LiO, LiCO3, LiSO4, or LiOH.

[0062] In one embodiment, the impurities may be free of lithium carbonate (Li2CO3) and lithium sulfate (Li2SO4), excluding lithium oxide (Li2O). In one embodiment, the content of lithium oxide (Li2O) may be 3.0% or less. Specifically, the content of lithium oxide (Li2O) may be 1.6% or less. The lithium oxide (Li2O) corresponds to an impurity, and when the content of the lithium oxide (Li2O) satisfies the above-mentioned range, high-purity lithium sulfide with a low impurity content can be achieved. When the content of the lithium oxide (Li2O) exceeds the above-mentioned range, there is a problem in that lithium conductivity decreases during the synthesis of azirodite using Li2S. In one embodiment, the lithium sulfide powder of the present invention may satisfy the following formula 2: <Expression 2> [Li2O] × oxygen content ≦ 5.0 (In the formula 2, [Li2O] means the content of lithium oxide in the powder.)

[0063] The formula 2 represents the relationship between lithium oxide (Li2O) and the oxygen content, and the product of the lithium oxide and oxygen content being 5.0 or less is an indicator of high-purity lithium sulfide. The formula 1 may be 5 or less, specifically 2.5 or less, and more specifically 0.64 to 2.11 or less.

[0064] If the value of the formula 2 exceeds the above range, there is a problem that the electrical properties are deteriorated during the synthesis of azirodite.

[0065] A method for producing lithium sulfide according to another embodiment of the present invention includes the steps of: mixing a carbon raw material and a lithium compound to produce a lithium-carbon compound; filtering a solution obtained by mixing the lithium-carbon compound and a solvent; spray-drying the filtrate in an inert loop structure; and heat-treating the dried product. For details about lithium sulfide, please refer to the above description.

[0066] In one embodiment, the carbon raw material may include, but is not limited to, at least one of soft carbon, hard carbon, petroleum coke, coal-based needle coke, coal-based pitch coke, natural graphite, and artificial graphite. In one embodiment, the lithium-carbon compound may include at least one of lithium sulfate, lithium hydroxide, lithium oxide, and lithium carbonate. The step of preparing the lithium-carbon compound by mixing the carbon raw material and the lithium compound may be performed by heat-treating the carbon raw material and the lithium compound.

[0067] The step of spray-drying the filtrate in an inert loop structure is specifically carried out by a spray drying method. The filtrate may be in the form of a slurry, for example, and may be spray-dried while controlling the concentration of the liquid medium from which the filtrate is extracted. The spray drying method can produce a spray-dried product with a uniform particle size.

[0068] In one embodiment, the step of drying the filtered material can be performed at a temperature in the range of 100 to 160°C. Specifically, the temperature range is 110 to 160°C.

[0069] If the temperature exceeds the upper limit of the above range, impurities such as lithium carbonate (Li2CO3) and lithium sulfide (Li2SO4) may be generated in addition to the lithium sulfide compound produced, and the oxygen concentration may also increase.If the temperature exceeds the lower limit of the above range, drying may become insufficient during spray drying, and dried material containing a large amount of solvent may gradually accumulate in the spray drying circulation passage, making circulation difficult and reducing process efficiency.

[0070] In one embodiment, the step of drying the filtrate may include controlling the average particle size of the spray-dried product to 0.1 to 100 μm, specifically, the average particle size may be controlled to 1.0 to 10.0 μm.

[0071] If the average particle size exceeds the upper limit, problems may occur with uniformity during heat treatment of the dried product obtained by spray drying. If the concentration of the spray liquid or the injection speed is increased to increase the average particle size, the spray drying nozzle may become clogged, and cross-spraying to prevent this may reduce processability. If the average particle size exceeds the lower limit, the proportion of fine particles in the dried product increases, which may quickly clog the pre-filter of the aspirator that circulates the powder and solvent during spray drying, reducing processability. During heat treatment, the dried product may be blown away by the inert gas flowing into the tube furnace, resulting in loss of the heat-treated product.

[0072] In one embodiment, the step of spray-drying the filtrate at a temperature in the range of 110 to 160°C may include controlling the concentration of the extract (based on Li-ICP) extracted during spray-drying to 5 to 15 g / L. Specifically, the concentration of the extract may be controlled to 6 to 14 g / L.

[0073] If the concentration of the extract exceeds the upper limit, the process efficiency may be reduced due to clogging of the spray drying nozzle or the need for cross-spraying to prevent this.If the concentration of the extract exceeds the lower limit, the yield per unit time may be reduced and excessive time may be required to obtain a certain amount of dried material.

[0074] In one embodiment, the step of spray-drying the filtrate in an inert loop structure may include a step of controlling the shape of the spray-dried product to be spherical. The step of controlling the shape of the spray-dried product may be controlled by adjusting the concentration of the extract, the flow rate of the inert gas, or the injection rate of the extract. By including the step of controlling the shape of the spray-dried product to be spherical, uniform heat transfer can be achieved during heat treatment after drying.

[0075] In one embodiment, the step of spray-drying the filtrate in an inert loop structure can recycle a portion of the gas generated during drying and an inert gas. In one embodiment, the step of drying the filtrate can include a partially pure loop structure that induces a reaction of the gas generated from the spray-dried product during drying. In the drying step, an inert loop structure can be formed to recycle a portion of the gas generated during drying of the extract and an inert gas. During drying, the gas (H2S) generated from the spray-dried product and LiOET of the dried product can induce a sufficient reaction. Specifically, H2S gas can participate in the re-reaction according to the following reaction formula: [Reaction scheme] 2H2S+2LiOET→Li2S+2EtOH

[0076] This has the advantage that the aforementioned inactive loop structure contains a partially pure ring structure, which reduces the amount of LiOEt, which is a raw material for impurities, reduces the oxygen content, and enables the production of high-purity lithium sulfide.

[0077] In one embodiment, the spray-dried material may include lithium ethoxide (LiOEt, C2H5O-Li), ethanol (C2H5O-H, EtOH), and lithium bisulfide (LiSH, Lithium Hydrogen Sulfide).

[0078] The step of heat-treating the dried product involves applying heat to the dried spray-dried product to obtain final lithium sulfide (LiS). In one embodiment, the dried product, specifically the spray-dried product, can be heated in a temperature range of 400 to 800°C, more specifically, in a temperature range of 500 to 800°C. In one embodiment, the heat-treating step can be performed at a temperature increase rate of 5 to 20°C per minute.

[0079] In one embodiment, the maximum temperature may be maintained for 1 to 6 hours in the heat-treating step, and the heat-treating step may include a step of naturally cooling the dried material after the heat-treatment for the above-mentioned period.

[0080] If the temperature, heating rate, and maintenance time exceed the upper limits, lithium sulfide may be converted into lithium oxide, whereas if the temperature, heating rate, and maintenance time exceed the lower limits, impurities such as lithium hydroxide or lithium carbonate may not be easily removed, resulting in a decrease in the purity of lithium sulfide.

[0081] In one embodiment, the heat treatment of the dried material may be performed in an inert gas atmosphere, for example, the inert gas may include at least one of helium, neon, krypton, xenon, nitrogen, and argon.

[0082] Specific examples of the present invention will be described below. However, the following examples are specific examples of the present invention, and the present invention is not limited to the following examples.

[0083] Drying method 2 S comparison

[0084] <Experimental Example>

[0085] The steps were as follows: a carbothermal reduction step (Li2SO4 + 2C → Li2S + 2CO2↑) in which carbon and lithium sulfate were mixed and heat-treated in an inert gas atmosphere, Ar, to obtain a lithium sulfide-carbon mixture; a step in which the lithium sulfide-carbon mixture was mixed with ethanol to make an extract; a step in which the extract was dried to obtain a dried product; and a step in which the dried product was heat-treated in an inert gas atmosphere, Ar, to produce lithium sulfide (Li2S).

[0086] <Example 1> - Lithium sulfide manufacturing method based on low concentration-high temperature-spray drying synthesis method

[0087] In the step of controlling the spraying and drying temperature of the filtrate, the filtrate was sprayed under low concentration conditions (6 g / L, Li-ICP standard) by adjusting the ratio of the ethanol and lithium sulfide mixture, and rapidly dried at room temperature at 160 °C, except that the same procedure as in the experimental example was carried out.

[0088] <Comparative Example 1> - Lithium sulfide manufacturing method based on low-concentration reduced pressure dry synthesis method

[0089] In the step of controlling the spraying and drying temperature of the filtrate, the ratio of the ethanol and lithium sulfide mixture was adjusted to a low concentration condition (6 g / L, Li-ICP standard) and the temperature of the filtrate was set between 45°C and 50°C, and rotary evaporation and drying were performed under reduced pressure at 60 mbar under atmospheric pressure.

[0090] Figures 1a and 1b show the XRD peak values ​​of the dried lithium sulfide powder.

[0091] 1a and 1b show the XRD peak values ​​of Example 1 and Comparative Example 1. It was confirmed that lithium carbonate (Li2CO3) appeared in addition to lithium sulfide in Comparative Example 1. This confirmed that this method is superior in terms of Li2S purity compared to other drying methods.

[0092] Controlling the average particle size of the spray by controlling the concentration of the extract

[0093] 2a to 2g are SEM photographs and particle size distribution graphs showing the average particle size depending on the extract concentration, and FIGS. 2f to 2k are SEM photographs and particle size distribution graphs showing the average particle size depending on the reduced pressure drying method.

[0094] Figures 2a to 2c are SEM photographs at different magnifications (300x, 1Kx) and particle size distribution graphs of Example 2. Figures 2d to 2g are SEM photographs at different magnifications (100x, 300x, 1Kx) and particle size distribution graphs of Example 3. Figures 2f to 2k are SEM photographs at different magnifications (100x, 300x, 1Kx) and particle size distribution graphs of Comparative Example 2, which was subjected to reduced pressure drying.

[0095] Example 2: Low concentration spray-dried product

[0096] As in the drying method of Example 1, when spray drying was performed, the concentration of the extract was controlled to a low concentration of 6 g / L, and it was confirmed that the average particle size of the dried spray product after the drying process was 1.13 μm.

[0097] Example 3 - High concentration - spray dried product

[0098] When spray drying was performed as in Example 1, the concentration of the extract was changed to a high concentration of 10 g / L, and the average particle size of the dried spray product after the drying process was confirmed to be 8.65 μm.

[0099] <Comparative Example 2> - Low concentration - dried under reduced pressure

[0100] When the reduced pressure drying method was used as in Comparative Example 1, it was confirmed that the particle size was distributed widely from 1.75 to 224.59 μm, and the particle shape was not uniform.

[0101] Table 1 below shows particle size distribution data according to examples of the present invention and comparative examples.

[0102] [Table 1]

[0103] Referring to Table 1, it was confirmed through Examples 2 and 3 that the spray-dried product of the present invention, which is a precursor for preparing lithium sulfide, has a small standard deviation and a low (Dmax-Dmin) / D50 value, and thus has a uniform particle size.

[0104] Raman characterization of spray-dried materials

[0105] FIG. 3 shows the Raman characteristics of the lithium sulfide powder produced by the manufacturing method of the embodiment of the present invention.

[0106] Figure 3 shows the Raman spectra of Examples 4 and 5. Specifically, when the spray-dried product was examined, peaks of lithium ethoxide (LiOEt, CHO-Li), ethanol (EtOH, CHO-H), and lithium bisulfide (LiSH) were confirmed.

[0107] Example 4 - Low Concentration - High Temperature - Spray Dried

[0108] In the step of controlling the spraying and drying temperature of the filtrate, the filtrate was sprayed under low concentration conditions (6 g / L, Li-ICP standard) by adjusting the ratio of ethanol and lithium sulfide mixture, and then rapidly dried at room temperature at 150°C.

[0109] Example 5 - Low Concentration - Low Temperature - Spray Dried

[0110] In the step of controlling the spraying and drying temperature of the filtrate, the filtrate was sprayed under low concentration conditions (6g / L, Li-ICP standard) by adjusting the ratio of ethanol and lithium sulfide mixture, and then rapidly dried at room temperature at 115℃.

[0111] Exhaust gas characteristics during heat treatment of dried materials with and without an inert loop

[0112] 4a to 4d show the concentrations of gases generated during heat treatment of a spray-dried product according to one embodiment of the present invention.

[0113] 4a to 4c show the concentrations of C3H8, CH4, and H2S gases, respectively. Specifically, they show the concentrations of gases generated during heat treatment in Example 6 and Comparative Example 3 below. As shown, it was confirmed that the aforementioned gases were generated when the spray-dried material was heat-treated at 800°C.

[0114] Figures 5a and 5b are schematic diagrams of the reaction process during the drying step with and without an inert loop structure. Referring to Figures 5a and 5b, the inert loop structure recirculates a portion of the gases and inert gases generated during the drying of the extract, allowing for a sufficient reaction between H2S, the gas generated from the spray-dried material during drying, and LiOET in the dried material. When H2S gas re-participates in the reaction, the LiOEt, the source of impurities, is reduced, as shown in the following reaction equation, resulting in a reduction in impurities and a lower oxygen content. This can be confirmed by Table 1, which compares XRD data for different drying methods. [Reaction scheme] 2H2S+2LiOET-->Li2S+2EtOH

[0115] Example 6 - Low Concentration - Low Temperature - Spray Dried

[0116] In the same manner as in Example 1, in the step of controlling the spraying and drying temperature of the filtrate, the filtrate was sprayed under low concentration conditions (6 g / L, Li-ICP standard) by adjusting the ratio of ethanol and lithium sulfide mixture, and then rapidly dried at room temperature at 160°C.

[0117] <Comparative Example 3> - Low concentration - dried under reduced pressure

[0118] A vacuum drying method was carried out as in Comparative Example 1. In the step of controlling the spraying and drying temperature of the filtrate, the ratio of the ethanol and lithium sulfide mixture in the filtrate was adjusted, and the temperature of the rice bran was set between 45 and 50°C under low concentration conditions (6 g / L, Li-ICP standard), and rotary evaporation and drying were carried out by applying a vacuum of 60 mbar at atmospheric pressure.

[0119] XRD analysis of heat-treated products by temperature

[0120] 6a and 6b show XRD peaks obtained when the rapid thermal treatment temperature was controlled in spraying and drying filtered water according to examples and comparative examples of the present invention. Specifically, the XRD peaks of the roughly heat-treated filtered sprays obtained when the drying temperature was controlled at 110°C, 170°C, and 180°C, respectively, as in Example 7, Comparative Example 4, and Comparative Example 5, compared to Example 1, were confirmed.

[0121] <Example 7> - Low concentration - Low temperature spray drying synthesis method based lithium sulfide

[0122] The same procedure as in Example 1 was carried out except that the drying temperature was 110°C.

[0123] <Comparative Example 4> - Low concentration - High temperature spray drying synthesis method based lithium sulfide

[0124] The same procedure as in Example 1d was carried out except that the drying temperature was 170°C.

[0125] <Comparative Example 5> - Low concentration - High temperature spray drying synthesis method based lithium sulfide

[0126] The same procedure as in Example 1 was carried out except that the drying temperature was 180°C.

[0127] Looking at Example 7, Comparative Example 4, and Comparative Example 5, at temperatures above 170°C, in addition to Li2S, impurities Li2CO3 and Li2S O4 It was confirmed that oxygen was generated and the oxygen concentration also increased. This confirmed that the appropriate heat treatment temperature range was 110 to 160°C.

[0128] <Example 8> - High concentration - High temperature spray drying synthesis method based lithium sulfide

[0129] The same procedure as in Example 1 was carried out, except that the extract concentration was high (10 g / L).

[0130] XRD peak analysis of heat-treated high-concentration spray-dried material

[0131] 7a and 7b show XRD peaks of a high-concentration (10 g / L) filtrate during heat treatment after spray drying, in accordance with one embodiment of the present invention, in which the filtrate concentration is controlled when spraying and drying the filtrate.

[0132] 7a and 7b, it was confirmed that only Li2O was present in the impurity peak after the final heat treatment even in Example 8, where the lithium concentration was relatively high.

[0133] Table 2 below shows the impurity peaks and oxygen contents of lithium sulfide produced in the examples and comparative examples of the present invention.

[0134] [Table 2]

[0135] From Table 2, it was confirmed that when the lithium concentration of the extract filtrate for drying was within the range of the present invention, specifically, when low-concentration extract filtrate (6 g / L, Examples 1 and 7) and high-concentration extract filtrate (10 g / L, Example 8) were spray-dried and heat-treated, Li2S with an oxygen content in the 1% range was synthesized. In the examples of the present invention, as the extract concentration and heat-treatment temperature were within the range of the present invention, Li -2 It was confirmed that the O content was 1.6 wt% or less, and that it was possible to produce high-purity lithium sulfide with a low oxygen content.

[0136] The present invention is not limited to the above-described embodiments and / or examples, and may be manufactured in various different forms, and those skilled in the art will understand that the present invention can be embodied in other specific forms without changing the technical spirit or essential characteristics of the present invention. Therefore, it should be understood that the above-described embodiments and / or examples are illustrative in all respects and are not limiting.

Claims

1. Regarding precursors used in the production of lithium sulfide powder, It has a hollow shape, A precursor for producing lithium sulfide powder that satisfies the following formula 1: <Formula 1> (Dmax-Dmin) / D50≦15 (In the above formula 1, Dmax, Dmin, and D50 respectively mean the maximum particle size, the minimum particle size, and the particle size when particles are accumulated up to 50% by volume.)

2. The precursor for producing lithium sulfide powder according to claim 1 , wherein the hollow shape has a hemispherical shape.

3. 2. The precursor for producing lithium sulfide powder according to claim 1, wherein the standard deviation of particle size (STD DEV) is 11.0 or less.

4. The precursor exhibits a Raman spectrum of 2,600 to 3,250 cm －１ The first peak appears at wave numbers 2,500 to 2,600 cm －１ The second peak appears at a wave number of 850 to 1,500 cm- １ 2. The precursor for producing lithium sulfide powder according to claim 1, comprising a third peak appearing in

5. The first peak is an EtOH peak, the second peak is a LiSH peak, 5. The precursor for producing lithium sulfide powder according to claim 4, wherein the second peak is a peak of LiOEt.

6. 2. The precursor for producing lithium sulfide powder according to claim 1, wherein the Dmax is in the range of 10 to 100 μm.

7. 2. The precursor for producing lithium sulfide powder according to claim 1, wherein Dmin is in the range of 0.1 to 2.5 μm.

8. The precursor for producing lithium sulfide powder according to claim 1, wherein the formula 1 is 11.30 or less.

9. The present invention relates to a lithium sulfide powder for all-solid-state electrolytes, which is produced from a hollow-shaped precursor for producing lithium sulfide powder, Lithium sulfide (Li ２ S) and lithium oxide (Li ２ O), lithium carbonate (Li ２ CO ３ ) and lithium sulfide (Li ２ SO ４ ) containing any one of the impurities, Lithium sulfide powder having an oxygen content of less than 2.8%.

10. Among the impurities, lithium oxide (Li ２ Lithium carbonate (Li ２ CO ３ ), lithium sulfide (Li ２ SO ４ 10. The lithium sulfide powder according to claim 9, wherein no cations are present.

11. The lithium sulfide powder according to claim 9, which satisfies the following formula 2: <Formula 2> [Li] ２ O] × Oxygen content ≤ 5.0 (In the above formula 2, [Li ２ O] means the content of lithium oxide in the lithium sulfide powder)

12. The lithium sulfide powder according to claim 11, wherein the formula 2 is 2.5 or less.

13. The lithium sulfide powder according to claim 11, wherein the formula 2 is 0.64 to 2.

11.

14. The lithium oxide (Li ２ The lithium sulfide powder according to claim 9, wherein O) satisfies 1.6% or less by weight.

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