Method for producing lithium halide compound

Abstract

The present invention provides a method for producing a lithium halide compound, which produces a lithium halide compound with a low water content, especially lithium bromide and lithium iodide, in an industrially advantageous manner with high reaction efficiency without a direct water removal process. The method comprises: mixing a halogen molecule of at least one of lithium sulfide, bromine and iodine, and a first solvent; and removing the first solvent, wherein the first solvent is a solvent for dissolving the lithium halide containing the halogen element of the halogen molecule.

Description

Technical Field

[0001] The present invention relates to a method for producing a lithium halide compound. Background Art

[0002] In recent years, with the rapid spread of information-related and communication devices such as personal computers, video cameras, and mobile phones, the development of batteries used as their power sources has also gained significant attention. Batteries used for these applications have traditionally used electrolytes containing flammable organic solvents. However, the development of fully solid-state batteries eliminates the use of flammable organic solvents, simplifies safety features, and improves manufacturing costs and productivity. Consequently, the development of batteries that replace the electrolyte with a solid electrolyte layer is gaining momentum.

[0003] Sulfide solid electrolytes are conventionally known as solid electrolytes for use in solid electrolyte layers. For example, it is known that sulfide glass can be produced by reacting lithium sulfide with phosphorus sulfide, and then heat-treating the sulfide glass to obtain a glass-ceramic electrolyte having high ionic conductivity (see, for example, Patent Document 1). Furthermore, with the demand for higher ionic conductivity, methods for producing sulfide solid electrolytes containing halogen atoms using lithium halide are also known (see, for example, Patent Document 2).

[0004] For lithium halide used as a raw material in the manufacture of sulfide solid electrolytes containing halogen atoms, since aqueous solution raw materials are used or reacted in water during the synthesis process, it is usually manufactured as a hydrate (for example, see Patent Documents 3 and 4). If the lithium halide contains water, the ionic conductivity of the sulfide solid electrolyte is likely to decrease, so it is necessary to remove water from the lithium halide, and methods such as azeotropy with an organic solvent, drying and removing it (for example, see Patent Document 4) or heating under reduced pressure to remove water (for example, see Patent Documents 5 and 6) have been studied. However, no matter which method is used, it is not easy to remove water from the lithium halide hydrate.

[0005] Therefore, methods for producing anhydrous lithium halides such as lithium halides without removing water have been studied. For example, a method is disclosed in which lithium sulfide is reacted with halogen molecules using a pulverizer in a solvent such as an aromatic hydrocarbon in which alkali metal sulfide is poorly soluble (see, for example, Patent Document 7).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-228570

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2013-201110

[0010] Patent Document 3: Japanese Patent Application Laid-Open No. 2013-103851

[0011] Patent Document 4: Japanese Patent Application Laid-Open No. 2013-256416

[0012] Patent Document 5: Japanese Patent Application Laid-Open No. 2014-65637

[0013] Patent Document 6: Japanese Patent Application Laid-Open No. 2014-65638

[0014] Patent Document 7: International Publication No. 2017 / 159665 Summary of the Invention

[0015] Technical problem to be solved by the invention

[0016] The present invention has been completed in view of such actual conditions, and its object is to provide a method for producing lithium halide compounds with low water content, especially lithium bromide and lithium iodide, in an industrially advantageous manner with high reaction efficiency without a direct water removal process.

[0017] Solutions for solving the above technical problems

[0018] The preparation method of the lithium halide compound of the present invention comprises:

[0019] mixing lithium sulfide, a halogen molecule of at least one of bromine and iodine, and a first solvent; and

[0020] removing the solvent,

[0021] The first solvent is a solvent that dissolves lithium halide containing the halogen element of the halogen molecule.

[0022] Effects of the Invention

[0023] According to the present invention, a method for producing lithium halide compounds, particularly lithium bromide and lithium iodide, having a low water content can be provided without a direct water removal step with high reaction efficiency and in an industrially advantageous manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 These are the X-ray diffraction spectra of the lithium sulfide used in Example 1 and the lithium iodide obtained in Example 1.

[0025] Figure 2 These are the X-ray diffraction spectra of the lithium halide complex and lithium iodide obtained in Example 2.

[0026] Figure 3 This is the X-ray diffraction spectrum of lithium bromide and lithium iodide obtained in Example 3.

[0027] Figure 4 1 and 2 show the X-ray diffraction spectra of the lithium iodide complex and lithium iodide obtained in Example 4.

[0028] Figure 5 This is the X-ray diffraction spectrum of the lithium iodide obtained in Example 5.

[0029] Figure 6 This is a SEM (scanning electron microscope) image of the sample obtained in Comparative Example 1.

[0030] Figure 7 This is an EDS image of sulfur element constituting the sample obtained in Comparative Example 1.

[0031] Figure 8 This is an EDS image of the iodine element constituting the sample obtained in Comparative Example 1. DETAILED DESCRIPTION

[0032] The following describes an embodiment of the present invention (hereinafter sometimes referred to as "the present embodiment"). In addition, in this specification, the upper and lower limits of the numerical ranges of "above", "below", and "to" are numerical values ​​that can be combined arbitrarily, and the numerical values ​​of the Examples can also be used as the upper and lower limits.

[0033] (Discovery made by the inventors to complete the present invention)

[0034] The present inventors have conducted intensive studies to solve the above-mentioned technical problems, and as a result, have found the following matters and have completed the present invention.

[0035] As described in paragraph

[0013] of Patent Document 7, a method is known in which the surface of the alkali metal sulfide is scraped by crushing it with a pulverizer during the reaction between the alkali metal sulfide and the halogen molecules, thereby facilitating the reaction of the halogen molecules. However, this method requires the use of a pulverizer to promote the reaction, and therefore, the reaction is significantly delayed when the pulverizer is not used. The present inventors conducted an in-depth investigation into this phenomenon and determined that the cause is that lithium halide, a reactant obtained by the primary reaction between the alkali metal sulfide and the halogen molecules, precipitates on the surface of the alkali metal sulfide.

[0036] Therefore, the present inventors considered whether dissolving the generated lithium halide in a solvent could expose new lithium sulfide surfaces and promote the reaction with halogen molecules as a method to eliminate or minimize the use of a pulverizer, and thus studied changing the type of solvent.

[0037] The desired properties of the solvent used are the ability to dissolve lithium halides, particularly lithium bromide and lithium iodide, in order to reduce the precipitation of lithium halides on the surface of the alkali metal sulfide. On the other hand, since it is known from experience that solvents that dissolve lithium bromide and lithium iodide have difficulty dissolving solid iodine, the use of solvents that dissolve iodine was particularly studied.

[0038] Based on the above studies, it was finally discovered that by selecting a solvent that dissolves lithium halide as a solvent and mixing lithium sulfide and halogen molecules in the solvent, the reaction between lithium sulfide and halogen molecules proceeds without delay even without using a pulverizer.

[0039] [Method for producing lithium halide compounds]

[0040] The method for producing a lithium halide compound according to the first embodiment of the present invention includes:

[0041] mixing lithium sulfide, a halogen molecule of at least one of bromine and iodine, and a first solvent; and

[0042] removing the first solvent,

[0043] The first solvent is a solvent that dissolves lithium halide containing the halogen element of the halogen molecule.

[0044] Patent Document 7, mentioned above, reacts lithium sulfide with halogen molecules in a solvent such as an aromatic hydrocarbon, in which alkali metal sulfide is poorly soluble, thereby producing anhydrous lithium halides, such as lithium halides, without removing water. In this respect, the lithium halide can be produced more easily than the conventional methods described in Patent Documents 3 to 6. However, as mentioned above, since this method requires the use of a pulverizer, it lacks mass production capabilities and cannot be considered an industrially advantageous method. Furthermore, when a pulverizer is not used, there is the problem of lithium halide precipitating on the surface of the alkali metal sulfide, significantly slowing the reaction.

[0045] According to the first embodiment, by using a solvent that dissolves lithium halide corresponding to the halogen molecules used as the raw material, lithium halide obtained by the reaction between lithium sulfide and the halogen molecules and precipitated on the surface of the lithium sulfide is dissolved in the solvent. This suppresses the precipitation of lithium halide on the surface of the lithium sulfide, allowing the reaction between the lithium sulfide with newly exposed surfaces and the halogen molecules to occur consistently and thus promoting this reaction. Furthermore, by promoting this reaction, the reaction between the lithium sulfide and the halogen molecules can proceed simply by mixing without pulverization, thus eliminating the need for pulverization and providing an industrially advantageous production method.

[0046] Furthermore, in the first embodiment, the halogen element of the halogen molecule used as the raw material corresponds to the halogen element in the lithium halide soluble in the first solvent and the halogen element in the obtained lithium halide compound, that is, they are the same element.

[0047] When bromine is used as the halogen molecule, the lithium halide that can be dissolved by the first solvent is lithium bromide, and the obtained lithium halide compound is a lithium bromide compound. When iodine is used as the halogen molecule, the same is true for bromine molecules. Furthermore, when bromine and iodine atoms are used as the halogen molecules, the lithium halide that can be dissolved by the first solvent is lithium bromide and lithium iodide, and the obtained lithium halide compounds are lithium bromide compounds and lithium iodide compounds.

[0048] The method for producing a lithium halide compound according to the second embodiment of the present invention includes:

[0049] mixing lithium sulfide, halogen molecules, and a second solvent;

[0050] Then adding the first solvent and mixing; and

[0051] removing the second solvent,

[0052] The second solvent is a solvent that does not dissolve lithium halide including the halogen element of the halogen molecule.

[0053] The main feature of the second embodiment is that, in the first embodiment, lithium sulfide and halogen molecules are mixed using a second solvent before the first solvent is used, the first solvent is then added and mixed, and the second solvent is removed. As in the first embodiment, the halogen element in the halogen molecule, the halogen element in the lithium halide insoluble in the second solvent, and the halogen element in the resulting lithium halide compound are the same halogen element.

[0054] According to the second embodiment, by using a second solvent before using the first solvent, the reactivity of halogen molecules, particularly iodine, that are difficult to dissolve in the first solvent can be increased. If the first solvent is a solvent that dissolves iodine at least in trace amounts, then the use of a second solvent is unnecessary. However, as mentioned above, empirically, solvents that readily dissolve lithium halides also have the property of being difficult to dissolve halogen molecules, particularly iodine. In other words, it can be said that solvents that do not dissolve lithium halides also have the property of dissolving halogen molecules, particularly iodine. Furthermore, by using a second solvent that dissolves halogen molecules, particularly iodine, even when using iodine, a low-reactivity solid raw material, the reaction with lithium sulfide is facilitated, thereby improving reaction efficiency.

[0055] In view of the above findings, the use of a second solvent has been shown to have a beneficial effect by increasing the reactivity of halogen molecules, particularly iodine, thereby improving reaction efficiency. Furthermore, the use of a second solvent improves the dispersibility of lithium sulfide and halogen molecules used as raw materials, thereby also providing a secondary effect of increased reactivity when added to the first solvent.

[0056] Regarding the removal of the solvent, in the second embodiment, the second solvent is removed, but in the first embodiment, the first solvent is removed. Therefore, as a result, all the solvents used in the production method of this embodiment are removed.

[0057] In the method for producing a lithium halide compound according to the third aspect of the present embodiment,

[0058] The lithium halide compound includes a lithium halide complex.

[0059] The lithium halide complex is not only a lithium halide, i.e., lithium bromide or lithium iodide, but also a substance obtained by forming a complex with a solvent. The first solvent is a solvent having a property of dissolving the lithium halide. As a solvent having this property, a solvent having heteroatoms such as nitrogen atoms in its molecule is preferably used as described later. In this case, the heteroatom is defined as an atom that can coordinate (bond) with the atoms constituting the lithium halide, particularly the lithium atom, to form a complex (also referred to as a "lithium halide complex").

[0060] The inclusion of the lithium halide complex in the third embodiment means that the contribution of the halogen molecules to the reaction between lithium sulfide and the halogen molecules is increased by using such a first solvent, thereby promoting the reaction and further reducing the residual halogen molecules, thereby improving the reaction efficiency and achieving higher reaction efficiency.

[0061] In the method for producing a lithium halide compound according to the fourth embodiment of the present invention,

[0062] The first solvent is a solvent in which the solubility of lithium bromide and lithium iodide is 1 g / L or more.

[0063] The property of not dissolving lithium halide is specifically defined as the solubility of lithium halide such as lithium bromide and lithium iodide being 1 g / L or more.

[0064] By making the first solvent have such properties, the precipitation of lithium halide on the surface of lithium sulfide can be suppressed, and the reaction between lithium sulfide with newly exposed surfaces and halogen molecules can be always caused to occur and promoted, thereby improving the reaction efficiency.

[0065] In the method for producing a lithium halide compound according to the fifth aspect of the present embodiment,

[0066] The second solvent is a solvent in which the solubility of lithium bromide and lithium iodide is less than 1 g / L.

[0067] The property of dissolving lithium halide is specifically defined as the solubility of lithium halide such as lithium bromide and lithium iodide being less than 1 g / L.

[0068] By making the second solvent have such properties, the effect of increasing the reactivity of the halogen molecules, particularly iodine, which are difficult to dissolve in the first solvent can be easily achieved. As a result, the reaction between lithium sulfide and the halogen molecules is accelerated, and the reaction efficiency is improved.

[0069] In the method for producing a lithium halide compound according to the sixth aspect of the present embodiment,

[0070] This in turn involves cleaning and removing sulfur molecules.

[0071] The reaction between lithium sulfide and halogen molecules generates sulfur molecules as by-products along with the lithium halide. According to the sixth embodiment, the sulfur molecules generated as by-products are washed and removed, thereby producing a lithium halide compound with high purity.

[0072] In the method for producing a lithium halide compound according to the seventh aspect of the present embodiment,

[0073] In the cleaning and removing, a third solvent is used.

[0074] Furthermore, in the method for producing a lithium halide compound of the eighth embodiment,

[0075] The third solvent is removed by at least one treatment selected from filtration and heating under reduced pressure.

[0076] Washing and removal of sulfur molecules can be performed by washing with a third solvent, and removal of the third solvent used in washing can be performed by treatment such as filtration. Both methods are easy, and thus sulfur molecules produced as by-products can be easily removed.

[0077] In the method for producing a lithium halide compound according to the ninth aspect of the present embodiment,

[0078] The first solvent is an aprotic solvent having at least one functional group selected from an ester group, an ether group, and an amino group.

[0079] As described above, by using a solvent containing heteroatoms such as nitrogen atoms and oxygen atoms as the first solvent, more specifically, by using an aprotic solvent having a functional group containing these heteroatoms, a lithium halide complex can be formed. Furthermore, by increasing the contribution of the halogen molecules to the reaction between lithium sulfide and the halogen molecules, the reaction can be accelerated, further reducing the amount of residual halogen molecules. This improves the reaction efficiency, resulting in a higher reaction efficiency.

[0080] In the method for producing a lithium halide compound according to the tenth aspect of the present embodiment,

[0081] The second solvent is at least one of an aromatic hydrocarbon and an aliphatic hydrocarbon,

[0082] And in the method for producing a lithium halide compound of the eleventh embodiment,

[0083] The second solvent has a boiling point of 150° C. or lower.

[0084] As described above, the second solvent can easily enhance the reactivity of halogen molecules, particularly iodine, which are difficult to dissolve in the first solvent. Aromatic hydrocarbons, aliphatic hydrocarbons, or solvents with a boiling point of 150°C or higher are advantageous solvents for easily achieving this effect. Using such a second solvent promotes the reaction between lithium sulfide and the halogen molecules, improving reaction efficiency.

[0085] In the method for producing a lithium halide compound according to the twelfth aspect of this embodiment,

[0086] The third solvent is a solvent having a solubility of sulfur molecules of 0.1 g / L or more.

[0087] And in the method for producing a lithium halide compound of the thirteenth embodiment,

[0088] The third solvent is at least one of the aromatic hydrocarbon and the aliphatic hydrocarbon.

[0089] The third solvent is a solvent used to clean and remove sulfur molecules generated as by-products in the reaction between lithium sulfide and halogen molecules. By using a solvent with the above-mentioned solubility, specifically aromatic hydrocarbons, aliphatic hydrocarbons, etc., good cleaning and removal effects can be obtained, and lithium halide with high product purity can be easily obtained.

[0090] In the method for producing a lithium halide compound according to the fourteenth embodiment of the present invention,

[0091] The second solvent is the same as the third solvent.

[0092] As in the tenth and thirteenth embodiments, aromatic hydrocarbons and aliphatic hydrocarbons are preferably used as the second and third solvents. Using the same type of solvent is easier to handle than using different types of solvents and is more efficient in production management.

[0093] The manufacturing method of this embodiment will be described in more detail below in correspondence with the above-mentioned embodiment.

[0094] (lithium sulfide)

[0095] The lithium sulfide used in the production method of this embodiment is typically in particulate form and can be a commercially available product, or lithium sulfide produced by known methods can be used. Lithium sulfide is one of the alkali metal sulfides, and the ionic conductivity of sulfide solid electrolytes tends to improve with the use of lighter alkali metals. Therefore, the lithium halide obtained by the production method of this embodiment using lithium sulfide as a raw material is a relatively light metal among alkali metals and is an effective compound for improving ionic conductivity.

[0096] Known methods for obtaining lithium sulfide include, for example, a method in which lithium hydroxide and hydrogen sulfide are reacted at 70° C. to 300° C. in a hydrocarbon organic solvent to produce lithium hydrosulfide, followed by dehydrogensulfide treatment of the reaction solution to synthesize lithium sulfide (Japanese Patent Application Laid-Open No. 2010-163356 ); and a method in which lithium hydroxide and hydrogen sulfide are reacted at 130° C. to 445° C. to synthesize lithium sulfide (Japanese Patent Application Laid-Open No. 9-278423 ).

[0097] The average particle size (D 50 ) is preferably from 10 μm to 2000 μm, more preferably from 30 μm to 1500 μm, and even more preferably from 50 μm to 1000 μm. In this specification, the average particle size (D 50 ) is the particle size when the cumulative particle size distribution curve is drawn from the smallest particle to reach 50% of the total particle size, and the volume distribution is, for example, the average particle size that can be measured using a laser diffraction / scattering particle size distribution measuring device.

[0098] From the perspective of reducing the amount of water in the obtained lithium halide, and further reducing the amount of water in the solid electrolyte when the lithium halide is used as a raw material for a sulfide solid electrolyte, and suppressing the decrease in ionic conductivity and battery performance caused by water, it is preferred that the amount of water contained as an impurity in the lithium sulfide is less. The amount of water contained in the lithium sulfide is preferably 1.5% by mass or less, more preferably 1% by mass or less, and further preferably 0.5% by mass or less. In addition, as the lower limit, since the less the better, it is not particularly limited, and is usually about 0.1% by mass. In this specification, the amount of water in lithium sulfide is a value measured using a Karl Fischer moisture meter using a vaporization method and 280°C.

[0099] (Halogen molecule)

[0100] The halogen molecule used in the production method of this embodiment is at least one of bromine and iodine, and is a molecule represented by the following general formula (1).

[0101] X2…(1)

[0102] (In general formula (1), X represents bromine and iodine.)

[0103] As halogen molecules, generally, fluorine (F2), chlorine (Cl2), bromine (Br2) and iodine (I2) can be preferably exemplified, wherein bromine (Br2) and iodine (I2) are used as objects. In the production method of the present embodiment, the halogen molecules can be used alone or in combination. That is, bromine can be used alone, iodine can be used alone, and bromine and iodine can also be used in combination. In addition, in the production method of the present embodiment, as the halogen molecule, at least one of bromine and iodine is used as the object, but fluorine and chlorine as other halogen molecules can also be applied.

[0104] In the production method of this embodiment, lithium sulfide and halogen molecules react according to the reaction formula represented by the following reaction formula (2). Therefore, the amount of halogen molecules used may be the same molar amount relative to 1 mol of lithium sulfide. When multiple halogen molecules are used, the total molar amount of the multiple halogen molecules may be the same molar amount relative to 1 mol of lithium sulfide.

[0105] Li2S+X2→2LiX+S (2)

[0106] (In formula (2), X2 is a halogen molecule of bromine or iodine.)

[0107] As described above and as shown in reaction formula (2), lithium halide is generated by the reaction between lithium sulfide and halogen molecules. However, since the lithium halide is formed by precipitation on the surface of the lithium sulfide, further reaction of the lithium sulfide is difficult to proceed. According to the production method of this embodiment, since a first solvent that dissolves the lithium halide is used, the lithium halide is not precipitated on the surface of the lithium sulfide, and a new surface is always exposed, thereby promoting this reaction.

[0108] Furthermore, as shown in the above reaction formula (2), sulfur is produced as a by-product. In addition to the methods of Patent Documents 3 and 4, lithium halide can also be obtained by reacting lithium hydroxide with hydrogen halide, but water is produced as a by-product.

[0109] By choosing lithium sulfide and halogen molecules, which are readily available and amenable to mass production, as raw materials, the combination of lithium sulfide and halogen molecules is extremely useful, as it eliminates the production of water as a byproduct and allows for industrialization.

[0110] (First Solvent)

[0111] The first solvent used in the production method of this embodiment is a solvent that dissolves lithium halides. The lithium halide varies depending on the type of halogen molecule used with lithium sulfide, and specifically can include lithium bromide and lithium iodide. In other words, the first solvent is a solvent capable of dissolving these lithium halides.

[0112] The first solvent is not particularly limited as long as it can dissolve lithium halides such as lithium bromide and lithium iodide. Examples of such solvents include those having a solubility (20°C) of preferably 1 g / L or greater, more preferably 3 g / L or greater, and even more preferably 5 g / L or greater. If the solubility of the lithium halide is within this range, the lithium halide produced by the reaction between lithium sulfide and halogen molecules will not precipitate on the surface of the lithium sulfide but will rapidly dissolve in the first solvent, thereby further suppressing such precipitation. The upper limit of the solubility is not particularly limited, but is generally approximately 1000 g / L or less.

[0113] In this specification, the solubility of lithium halide is measured by the following method. Lithium halide is added to a solvent and thoroughly mixed at 20°C. The presence of lithium halide that is not dissolved in the solvent is visually observed in the solution. Next, the obtained solution is subjected to inductively coupled plasma (ICP) emission spectrometry using an inductively coupled plasma (ICP) emission spectrometry apparatus. The content of lithium in the resulting solution, i.e., the content of lithium dissolved in the solvent, is measured, and the solubility (g / L) of the lithium halide is calculated.

[0114] As such a first solvent, a complexing agent can be preferably exemplified. A complexing agent is a compound capable of forming a complex (also referred to as a "lithium halide complex") that coordinates (bonds) with lithium atoms, sulfur atoms, and halogen atoms, particularly lithium atoms, contained in the lithium sulfide, halogen molecules, or lithium halide obtained by reaction thereof used in the production method of this embodiment. Any complexing agent having such properties can be used without particular limitation. In particular, compounds containing atoms with a high affinity for lithium atoms, such as nitrogen atoms, oxygen atoms, and chlorine atoms, are preferably exemplified, and compounds having groups containing such heteroatoms are more preferably exemplified.

[0115] The use of a complexing agent as the first solvent promotes the reaction between lithium sulfide and halogen molecules, further reducing residual halogen molecules, thereby improving reaction efficiency and achieving higher reaction efficiency. Furthermore, the use of a complexing agent as the first solvent allows the lithium halide formed by the reaction between lithium sulfide and halogen atoms to dissolve as a complex in the solvent. Removal of the solvent makes the resulting lithium halide porous, resulting in a sulfide solid electrolyte with higher ionic conductivity.

[0116] In the manufacture method of the present embodiment, when using a complexing agent as the first solvent, the material obtained by mixing and removing the solvent is a complex compound produced by the above-mentioned coordination (bonding) and composed of a lithium halide and a complexing agent, and strictly speaking, it can not be said to be a lithium halide. That is, the lithium halide compound obtained by the manufacture method of the present embodiment is not only a lithium halide, but also a lithium halide complex, or when using a variety of halogen molecules, it can also include a material that is also referred to as a lithium halide complex containing a halogen atom brought by the various halogen molecules. Moreover, any of the above-mentioned materials is suitable for use as a raw material for a sulfide solid electrolyte, so the lithium halide compound obtained by the manufacture method of the present embodiment can be any one of a lithium halide, a lithium halide complex, and a lithium halide complex.

[0117] As heteroatoms, nitrogen atoms and oxygen atoms are more preferred. As groups containing these heteroatoms, and as groups containing nitrogen atoms, amino groups, amide groups, nitro groups, and nitrile groups are preferred, with amino groups being more preferred. Furthermore, as groups containing oxygen atoms, ester groups and ether groups are preferred, with ester groups being more preferred. Therefore, in the production method of this embodiment, it is particularly preferred that the solvent used as the first solvent is a complexing agent, particularly an aprotic solvent having at least one functional group selected from ester groups, ether groups, and amino groups.

[0118] Examples of the complexing agent having an amino group include amine compounds such as aliphatic amines, alicyclic amines, heterocyclic amines, and aromatic amines, and these can be used alone or in combination of two or more.

[0119] Representative preferred examples of the aliphatic amine include: primary aliphatic diamines such as ethylenediamine, diaminopropane, and diaminobutane; secondary aliphatic diamines such as N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N'-dimethyldiaminopropane, and N,N'-diethyldiaminopropane; tertiary aliphatic diamines such as N,N,N',N'-tetramethyldiaminomethane, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetraethylethylenediamine, N,N,N',N'-tetramethyldiaminopropane, N,N,N',N'-tetraethyldiaminopropane, N,N,N',N'-tetramethyldiaminobutane, N,N,N',N'-tetramethyldiaminopentane, and N,N,N',N'-tetramethyldiaminohexane; and the like. Here, in the examples of this specification, for example, diaminobutane includes all isomers such as linear and branched isomers of butane, in addition to isomers related to the position of the amino group such as 1,2-diaminobutane, 1,3-diaminobutane, and 1,4-diaminobutane, unless otherwise specified.

[0120] The number of carbon atoms in the aliphatic amine is preferably 2 or more, more preferably 4 or more, and even more preferably 6 or more, and the upper limit is preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. Furthermore, the number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic amine is preferably 2 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0121] Examples of the alicyclic amines include, for example, primary alicyclic diamines such as cyclopropylene diamine and cyclohexane diamine; secondary alicyclic diamines such as bisaminomethylcyclohexane; tertiary alicyclic diamines such as N,N,N',N'-tetramethyl-cyclohexane diamine and bis(ethylmethylamino)cyclohexane; and the like. Examples of the heterocyclic amines include, for example, primary heterocyclic diamines such as isophorone diamine; secondary heterocyclic diamines such as piperazine and dipiperidylpropane; and tertiary heterocyclic diamines such as N,N-dimethylpiperazine and bismethylpiperidylpropane.

[0122] The carbon number of the alicyclic amine or heterocyclic amine is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0123] In addition, representative and preferred examples of aromatic amines include: aromatic primary diamines such as phenylenediamine, toluenediamine, and naphthalenediamine; aromatic secondary diamines such as N-methylphenylenediamine, N,N'-dimethylphenylenediamine, N,N'-dimethylphenylphenylenediamine, N,N'-dimethylnaphthalenediamine, and N-naphthylethylenediamine; aromatic tertiary diamines such as N,N-dimethylphenylenediamine, N,N,N',N'-tetramethylphenylenediamine, N,N,N',N'-tetramethyldiaminodiphenylmethane, and N,N,N',N'-tetramethylnaphthalenediamine; and other aromatic diamines.

[0124] The number of carbon atoms in the aromatic amine is preferably 6 or more, more preferably 7 or more, and even more preferably 8 or more, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less.

[0125] The amine compound used in the present embodiment may be an amine compound substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxy group, a hydroxyl group, a cyano group, or a halogen atom.

[0126] Furthermore, although diamines are exemplified as specific examples, the amine compounds that can be used in this embodiment are obviously not limited to diamines. For example, trimethylamine, triethylamine, ethyldimethylamine, aliphatic monoamines corresponding to various diamines such as the above-mentioned aliphatic diamines; piperidine compounds such as piperidine, methylpiperidine, and tetramethylpiperidine; pyridine compounds such as pyridine and methylpyridine; morpholine compounds such as morpholine, methylmorpholine, and thiomorpholine; imidazole compounds such as imidazole and methylimidazole; and cyclopentadiene compounds corresponding to the above-mentioned alicyclic diamines. In addition to alicyclic monoamines such as monoamine; heterocyclic monoamines corresponding to the above-mentioned heterocyclic diamines; and aromatic monoamines corresponding to the above-mentioned aromatic diamines, polyamines having three or more amino groups such as diethylenetriamine, N,N',N"-trimethyldiethylenetriamine, N,N,N',N",N"-pentamethyldiethylenetriamine, triethylenetetramine, N,N'-bis[(dimethylamino)ethyl]-N,N'-dimethylethylenediamine, hexamethylenetetramine, and tetraethylenepentamine can also be used.

[0127] Among the above, from the viewpoints of promoting the reaction between lithium sulfide and halogen molecules to improve reaction efficiency, and rapidly dissolving lithium halide to suppress precipitation on the surface of lithium sulfide, tertiary amines having a tertiary amino group as the amino group are preferred, tertiary diamines having two tertiary amino groups are more preferred, tertiary diamines having two tertiary amino groups at both terminals are further preferred, and aliphatic tertiary diamines having tertiary amino groups at both terminals are even more preferred. Among the above amine compounds, aliphatic tertiary diamines having tertiary amino groups at both terminals are preferred, including tetramethylethylenediamine, tetraethylethylenediamine, tetramethyldiaminopropane, and tetraethyldiaminopropane. Considering availability, tetramethylethylenediamine (also known as "TMEDA") and tetramethyldiaminopropane (also known as "TMPDA") are preferred.

[0128] Although not specifically mentioned, compounds having groups other than amino groups containing nitrogen atoms as heteroatoms, such as amide groups, nitro groups, and nitrile groups, can also achieve the same effects as compounds containing amino groups.

[0129] Next, examples of the complexing agent having the above-mentioned ether group as the group containing an oxygen atom include ether compounds such as aliphatic ether, alicyclic ether, heterocyclic ether, and aromatic ether, and these can be used alone or in combination of two or more.

[0130] Examples of the aliphatic ether include monoethers such as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, and tert-butyl methyl ether; diethers such as dimethoxymethane, dimethoxyethane, diethoxymethane, and diethoxyethane; polyethers having three or more ether groups such as diethylene glycol dimethyl ether (diglyme) and triethylene glycol dimethyl ether; and ethers containing hydroxyl groups such as diethylene glycol and triethylene glycol.

[0131] The carbon number of the aliphatic ether is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more, and the upper limit is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less.

[0132] The carbon number of the aliphatic hydrocarbon group in the aliphatic ether is preferably 1 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0133] Examples of the alicyclic ether include ethylene oxide, propylene oxide, tetrahydrofuran, tetrahydropyran, dimethoxytetrahydrofuran, cyclopentyl methyl ether, dioxane, and dioxolane. Examples of the heterocyclic ether include furan, benzofuran, benzopyran, dioxine, dioxin, morpholine, methoxyindole, and hydroxymethyldimethoxypyridine.

[0134] The carbon number of the alicyclic ether or heterocyclic ether is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0135] Examples of the aromatic ether include methyl phenyl ether (anisole), ethyl phenyl ether, dibenzyl ether, diphenyl ether, benzyl phenyl ether and naphthyl ether.

[0136] The number of carbon atoms in the aromatic ether is preferably 7 or more, more preferably 8 or more, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less.

[0137] The ether compound used in the present embodiment may be an ether compound substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxy group, a hydroxyl group, a cyano group, or a halogen atom.

[0138] From the viewpoints of promoting the reaction between lithium sulfide and halogen molecules to improve reaction efficiency and rapidly dissolving lithium halide to suppress precipitation on the surface of lithium sulfide, the ether compound used in this embodiment is preferably an aliphatic ether, more preferably dimethoxyethane or tetrahydrofuran.

[0139] Examples of the complexing agent having the aforementioned ester group as the group containing an oxygen atom include ester compounds such as aliphatic esters, alicyclic esters, heterocyclic esters, and aromatic esters, and these can be used alone or in combination of two or more.

[0140] Examples of the aliphatic ester include formic acid esters such as methyl formate, ethyl formate, and triethyl formate; acetates such as methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, and isobutyl acetate; propionic acid esters such as methyl propionate, ethyl propionate, propyl propionate, and butyl propionate; oxalic acid esters such as dimethyl oxalate and diethyl oxalate; malonic acid esters such as dimethyl malonate and diethyl malonate; and succinic acid esters such as dimethyl succinate and diethyl succinate.

[0141] The number of carbon atoms in the aliphatic ester is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more, and the upper limit is preferably 10 or less, more preferably 8 or less, and even more preferably 7 or less. Furthermore, the number of carbon atoms in the aliphatic hydrocarbon group in the aliphatic ester is preferably 1 or more, more preferably 2 or more, and the upper limit is preferably 6 or less, more preferably 4 or less, and even more preferably 3 or less.

[0142] Examples of the alicyclic ester include methyl cyclohexanecarboxylate, ethyl cyclohexanecarboxylate, dimethyl cyclohexanedicarboxylate, dibutyl cyclohexanedicarboxylate, and dibutyl cyclohexenedicarboxylate. Examples of the heterocyclic ester include methyl pyridinecarboxylate, ethyl pyridinecarboxylate, propyl pyridinecarboxylate, methyl pyrimidinecarboxylate, ethyl pyrimidinecarboxylate, and lactones such as acetolactone, propiolactone, butyrolactone, and valerolactone.

[0143] The carbon number of the alicyclic ester or heterocyclic ester is preferably 3 or more, more preferably 4 or more, and the upper limit is preferably 16 or less, more preferably 14 or less.

[0144] Examples of the aromatic ester include benzoates such as methyl benzoate, ethyl benzoate, propyl benzoate, and butyl benzoate; phthalates such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, and dicyclohexyl phthalate; and trimellitic esters such as trimethyl trimellitate, triethyl trimellitate, tripropyl trimellitate, tributyl trimellitate, and trioctyl trimellitate.

[0145] The number of carbon atoms in the aromatic ester is preferably 8 or more, more preferably 9 or more, and the upper limit is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less.

[0146] The ester compound used in the present embodiment may be an ester compound substituted with a substituent such as an alkyl group, an alkenyl group, an alkoxy group, a hydroxyl group, a cyano group, or a halogen element.

[0147] From the viewpoint of promoting the reaction between lithium sulfide and halogen molecules to improve reaction efficiency and rapidly dissolving lithium halide to suppress precipitation on the surface of lithium sulfide, the ester compound used in this embodiment is preferably an aliphatic ester, more preferably an acetate, and particularly preferably ethyl acetate.

[0148] The substances exemplified as complexing agents preferably used as the first solvent basically form lithium halide complexes obtained by coordination (bonding) of the heteroatoms of the complexing agent with the lithium atoms of lithium sulfide. Some substances do not form such complexes, and substances having an oxygen atom as a heteroatom serving as an ester group tend to be difficult to form complexes. However, even if such complexes are not formed, the effect of improving the reaction efficiency will not be hindered. This is because they have the property of dissolving lithium halide and the property of dissolving halogen molecules, particularly iodine, which can reduce residual halogen molecules, thereby improving the reaction efficiency.

[0149] In the production method of this embodiment, the amount of the first solvent used is preferably 100 mL or more, more preferably 200 mL or more, even more preferably 250 mL or more, and even more preferably 300 mL or more, relative to 1 kg of the total amount of lithium sulfide and halogen molecules. The upper limit is preferably 3000 mL or less, more preferably 2500 mL or less, even more preferably 2000 mL or less, and even more preferably 1550 mL or less. When the amount of the first solvent used is within this range, the lithium halide dissolves rapidly, and precipitation on the surface of the lithium sulfide is easily suppressed.

[0150] (mix)

[0151] The production method of this embodiment includes mixing the lithium sulfide, halogen molecules, and a first solvent that dissolves the lithium halide. This mixing produces lithium halide through a reaction between the lithium sulfide and the halogen molecules. The resulting lithium halide does not precipitate on the surface of the lithium sulfide but dissolves in the first solvent. Therefore, newly formed surfaces of the lithium sulfide are always in contact with the halogen molecules, promoting the reaction.

[0152] When lithium sulfide, halogen molecules, and the first solvent dissolving the lithium halide are mixed, the mixing method is not particularly limited. The lithium sulfide, halogen molecules, and the first solvent may be placed in a device capable of mixing them and mixed.

[0153] Here, as halogen molecules, for example, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid at room temperature and pressure. Therefore, the halogen molecules can be supplied and mixed using a method appropriate to the state of the halogen molecules. For example, if the halogen molecules are liquid, they can be supplied to the tank together with the first solvent. If the halogen molecules are gaseous, they can be supplied by blowing them into a complexing agent containing lithium sulfide. If the halogen molecules are solid, they can be supplied to the tank together with lithium sulfide.

[0154] In the manufacturing method of the present embodiment, it is characterized by including mixing lithium sulfide, halogen molecules and a first solvent, and even without using a device generally referred to as a pulverizer such as a ball mill, a bead mill, or other media type pulverizer (without pulverization), lithium halide can be efficiently manufactured. In the manufacturing method of the present embodiment, "mixing" refers to a process carried out by stirring or other treatments to such an extent that the lithium sulfide and halogen molecules (iodine) as solid raw materials are not pulverized. In addition, in order to shorten the mixing time or micronization for obtaining the complex, the raw materials can also be pulverized by a pulverizer, but from the viewpoint of industrialization, it is preferably not to use a pulverizer, i.e., not to pulverize. It can also be said that being able to manufacture lithium halide even without pulverization is one of the advantages of the manufacturing method of the present embodiment.

[0155] As a device for mixing lithium sulfide, halogen molecules and the first solvent, it is sufficient to select an appropriate device according to the scale. For example, if it is a small scale, a device such as a Schrank flask with a stirring bar can be used. In addition, if it is a medium to large scale, a mechanical stirring mixer with stirring blades in the tank can be used.

[0156] Mechanical stirring type mixer can exemplify high-speed stirring type mixer, double-arm type mixer etc., from the viewpoint of improving the uniformity of the raw material in the mixture of raw material and complexing agent and obtaining higher ion conductivity, preferably use high-speed stirring type mixer.In addition, as high-speed stirring type mixer, vertical axis rotation type mixer, horizontal axis rotation type mixer etc. can be exemplified, also can use any type of mixer.

[0157] The shape of the stirring blade used in the mechanical stirring mixer may, for example, be a blade type, an arm type, an anchor type, a paddle type, a stirring paddle type, a belt type, a multi-stage blade type, a double-arm type, a bucket type, a biaxial blade type, a flat blade type, a C-shaped blade type, etc. From the viewpoint of efficiently carrying out the reaction between lithium sulfide and halogen molecules, rapidly dissolving the obtained lithium halide, and easily suppressing precipitation on the surface of lithium sulfide, a bucket type, a flat blade type, a C-shaped blade type, an anchor type, a paddle type, and a stirring paddle type are preferred, and an anchor type, a paddle type, and a stirring paddle type are more preferred.

[0158] The temperature conditions during mixing are not particularly limited, but are generally -30 to 100°C, preferably 5 to 50°C, more preferably 10 to 30°C, and even more preferably around room temperature (23°C) (e.g., around ±5°C from room temperature). The mixing time is generally 0.1 to 500 hours, but from the perspective of efficiently and fully promoting the reaction between lithium sulfide and the halogen atom, it is preferably 0.5 to 100 hours, more preferably 1 to 50 hours, even more preferably 2 to 25 hours, and even more preferably 3 to 10 hours.

[0159] (Second Solvent)

[0160] In the manufacturing method of this embodiment, in addition to the above-mentioned first solvent, a second solvent that does not dissolve lithium halide can also be used as a solvent other than the first solvent. As mentioned above, the first solvent has the property of dissolving lithium halide, and according to experience, it also has the property of being difficult to dissolve halogen molecules, especially iodine. In contrast, the second solvent has the property of not dissolving lithium halide, and has the property of easily dissolving halogen molecules, especially iodine. Therefore, it can also be said that the second solvent is a solvent that is preferably used to improve the reactivity of iodine, which is difficult to dissolve in the first solvent. Moreover, by using the second solvent before using the first solvent, the reaction between lithium sulfide and halogen molecules, especially iodine, can be promoted, thereby achieving an improvement in reaction efficiency. When bromine is used as the halogen molecule, bromine is a liquid at room temperature and can be dispersed without using a second solvent, so a second solvent is not necessarily required. Therefore, when iodine is used as the halogen molecule, the second solvent is particularly effective.

[0161] The second solvent is a solvent that does not dissolve lithium halide. There are no particular restrictions as long as it is a solvent that does not dissolve lithium halide. Examples include solvents that have a solubility (20°C) of preferably less than 1 g / L, more preferably 0.5 g / L or less, further preferably 0.1 g / L or less, and even more preferably 0.07 g / L or less.

[0162] When the solubility of the lithium halide is within the above range, the dispersion of the lithium sulfide and the halogen molecules can be improved. Furthermore, the lithium halide generated by the reaction between the lithium sulfide and the halogen molecules does not precipitate on the surface of the lithium sulfide but rapidly dissolves in the first solvent, thereby further suppressing such precipitation. The lower limit is not particularly limited, but is generally 0.01 mg / L or greater.

[0163] In addition, the second solvent is preferably a solvent that dissolves halogen molecules, particularly iodine. As its solubility (25° C.), it is preferably 0.03% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more. In addition, there is no limit to the upper limit, but for example, a solubility of less than 60% by mass, less than 55% by mass, or less than 10% by mass can be exemplified. If the solubility of iodine in the second solvent is within the above range, the effect of using the above-mentioned second solvent can be efficiently obtained, and the same effect can be obtained even if bromine is used as the other halogen molecule.

[0164] In this specification, the solubility of halogen molecules is measured by the following method.

[0165] Iodine (2 g) was added to 3 mL of solvent and stirred at 25°C for 20 minutes. 0.1 g of the supernatant was weighed, and 1 g of an aqueous sodium thiosulfate solution (10% by mass, Na₂S₂O₃) was added to the supernatant. The mixture was shaken for approximately 1 minute to confirm that the solution had lost its color. The iodine concentration of the solution was quantified using ICP emission spectrometry (high-frequency inductively coupled plasma spectrophotometry) to calculate the iodine solubility.

[0166] Preferred examples of the second solvent having such properties include hydrocarbon solvents such as aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons; and solvents containing carbon atoms such as solvents containing carbon atoms and heteroatoms.

[0167] Examples of aliphatic hydrocarbons include hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, and tridecane; examples of alicyclic hydrocarbons include cyclohexane and methylcyclohexane; examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, mesitylene, tert-butylbenzene, trifluoromethylbenzene, and nitrobenzene; and examples of solvents containing carbon atoms and heteroatoms include carbon disulfide, diethyl ether, dibutyl ether, and tetrahydrofuran.

[0168] As the second solvent, one kind thereof can be used alone, or a plurality of kinds thereof can be used in combination.

[0169] Among them, hydrocarbon solvents are preferred from the viewpoint of rapidly dissolving lithium halide and suppressing precipitation on the surface of lithium sulfide, and aromatic hydrocarbons and aliphatic hydrocarbons are more preferred. As the aromatic hydrocarbon, toluene is preferred.

[0170] Furthermore, as aliphatic hydrocarbons, those having a carbon number of 2 or more and 8 or less are preferred, those having a carbon number of 3 or more and 7 or less are more preferred, and those having a carbon number of 4 or more and 6 or less are even more preferred. Furthermore, alicyclic hydrocarbons are preferred, and the carbon number of the cyclic portion is preferably 3 or more and 8 or less, more preferably 4 or more and 7 or less, even more preferably 4 or more and 6 or less, and particularly preferably 6. As an alicyclic hydrocarbon, cyclohexane is particularly preferred.

[0171] The boiling point of the second solvent is preferably 150° C. or lower, more preferably 140° C. or lower. The lower limit is not particularly limited, as long as it is 90° C. or higher. When the boiling point is within this range, the second solvent has an appropriate viscosity, allowing for a good dispersion of lithium sulfide and halogen molecules.

[0172] The second solvent is a solvent that does not dissolve lithium halide, but in addition to this property, it also has the property of easily dissolving sulfur molecules. In the manufacturing method of this embodiment, lithium sulfide and halogen molecules react according to the reaction formula shown in the above reaction formula (2), and sulfur molecules are generated as by-products together with the lithium halide. That is, the mixture obtained by mixing lithium sulfide, halogen molecules, the first solvent, and the second solvent also contains sulfur molecules. In order to obtain lithium halide, it is necessary to remove the sulfur molecules as by-products. Since the second solvent has the property of dissolving sulfur molecules, the second solvent can be removed by removing the solvent described later, thereby also removing the sulfur molecules dissolved in the solvent. Therefore, the effect of removing sulfur molecules by cleaning can also be expected by removing the solvent described later. In addition, from the perspective of improving the quality of the obtained lithium halide compound, it is preferred to clean and remove the sulfur molecules as described later.

[0173] Regarding the property of the second solvent to readily dissolve sulfur molecules, specifically, a solvent having a sulfur solubility (25°C) of preferably 1 g / L or greater, more preferably 0.3 g / L or greater, even more preferably 0.5 g / L or greater, and particularly preferably 10 g / L or greater is used as the second solvent. The upper limit of the sulfur solubility is not particularly limited, but may be, for example, 600 g / L or less, 550 g / L or less, or 100 g / L or less. In this specification, the sulfur solubility is a value measured as follows.

[0174] (Measurement of Sulfur Solubility)

[0175] To 10 g of sulfur, add 50 ml of solvent, adjust the temperature to 25°C in an oil bath, and stir for 2 hours. Then, separate the supernatant using a cannula (transfer tube) fitted with a glass filter. The separated supernatant is evacuated to obtain dry sulfur. The sulfur solubility (mass %) is calculated based on the mass of the dry sulfur and the mass of the solvent in which the dry sulfur is dissolved.

[0176] When using a second solvent, it is preferred to mix lithium sulfide and halogen molecules with the second solvent before adding the first solvent for mixing. Specifically, prior to mixing with the first solvent, the lithium sulfide and halogen molecules are mixed in the second solvent, and then the first solvent is added to mix the lithium sulfide, halogen molecules, and the first solvent with the second solvent. By mixing the lithium sulfide and halogen molecules in the second solvent before mixing with the first solvent, the halogen molecules, particularly iodine, dissolve in the second solvent, increasing reactivity, promoting the reaction between the lithium sulfide and halogen molecules, and improving reaction efficiency. Furthermore, by preliminarily increasing the dispersibility of the lithium sulfide and halogen molecules in the second solvent, when using a complexing agent as the first solvent, the formation of a lithium halide complex is facilitated. As described above, this can further reduce residual halogen molecules, thereby improving reaction efficiency and achieving a higher reaction efficiency.

[0177] The mixing time of lithium sulfide and halogen molecules in the second solvent is preferably 0.5 hours or longer, more preferably 1 hour or longer, and even more preferably 1.5 hours or longer. The upper limit is preferably 4 hours or shorter, more preferably 3 hours or shorter, and even more preferably 2.5 hours or shorter. If the mixing time in the second solvent is within this range, the dispersion state of lithium sulfide and halogen molecules can be improved, and the precipitation of lithium halide on the surface of lithium sulfide can be suppressed.

[0178] When a second solvent is used, the amount of the second solvent used is preferably 2000 mL or more, more preferably 3500 mL or more, even more preferably 5000 mL or more, and even more preferably 6000 mL or more, per 1 kg of the total amount of lithium sulfide and halogen molecules. The upper limit is preferably 10000 mL or less, more preferably 9000 mL or less, even more preferably 8000 mL or less, and even more preferably 7500 mL or less. When the amount of the second solvent used is within the above range, the dispersion of lithium sulfide and halogen molecules can be improved, and the precipitation of lithium halide on the surface of lithium sulfide can be suppressed.

[0179] (Solvent removal)

[0180] The manufacture method of present embodiment comprises removing solvent.By removing solvent, lithium halide compound can be obtained.Removing solvent comprises removing solvent existing as liquid from the mixture of lithium sulfide, halogen molecule, first solvent and the second solvent used as needed, and removing the first solvent from the lithium halide complex doped with the first solvent.For removing solvent, it is possible to adjust which form of removal is carried out by the method for removing solvent. When carrying out the former removal, methods such as solid-liquid separation such as filtration and decantation are adopted. When carrying out the latter removal, a drying method is adopted.About these methods will be described later.

[0181] As described above, the lithium halide compound may include lithium halide, lithium halide complex, lithium halide complex containing multiple halogen atoms, etc. More specifically, when a complexing agent is used as the first solvent, the lithium halide compound includes both lithium halide and lithium halide complex, when multiple halogen molecules are used, the lithium halide compound includes both lithium halide and lithium halide complex containing multiple halogen atoms, and when a complexing agent is used as the first solvent and multiple halogen molecules are used, the lithium halide compound may include both lithium halide and lithium halide complex and lithium halide complex.

[0182] Therefore, for example, when a complexing agent is used as the first solvent and multiple halogen molecules are used, if the solvent is removed by filtration, lithium halide, lithium halide complex and lithium halide complex can be obtained, and if the solvent is removed by drying, lithium halide and lithium halide complex can be obtained.

[0183] Focusing on the substances removed by solvent removal, when only the first solvent is used, the first solvent is removed, while when the first solvent is used in combination with the second solvent, both the first and second solvents are removed. Furthermore, as described above, when the second solvent is used, the second solvent can dissolve sulfur molecules produced as a byproduct, so the sulfur molecules can also be removed by solvent removal.

[0184] As described later, when a third solvent is used to clean the lithium halide compound and sulfur molecules, the third solvent also becomes a solvent removed by the solvent removal, and the sulfur molecules can be removed together with the second solvent in the same manner. In this case, the solvent removal can be performed once after the above-mentioned mixing, or again after cleaning, that is, twice. This point will also be explained in detail when cleaning is explained.

[0185] As the method for removing the solvent, as described above, filtration, drying, etc. can be preferably mentioned, and these methods may be combined.

[0186] Filtration is a method used to remove a solvent in a liquid state, and can be performed using, for example, a glass filter. As the glass filter, for example, a glass filter having a pore size of about 10 to 200 μm, preferably 20 to 150 μm can be used.

[0187] Drying is a method capable of removing the solvent present as a liquid and capable of removing the first solvent (complexing agent) incorporated into the lithium halide complex.

[0188] Drying can be carried out by drying under reduced pressure, heat drying etc., for example, can after drying under reduced pressure, then carry out heat drying, in addition, also can carry out heat drying under reduced pressure.If by drying and removing solvent, then solvent is removed by volatilization etc., therefore in the lithium halide compound, comprise under the situation of lithium halide complex, the first solvent is volatilized from this complex and is removed, becomes lithium halide.Therefore, when using the first solvent, when wanting to make lithium halide complex become lithium halide, by drying and removing solvent and get final product.

[0189] As described above, drying is a method for removing the first solvent incorporated into the lithium halide complex. However, by adjusting the heating temperature to a level that does not remove the incorporated first solvent, the lithium halide complex can be maintained in its current state. Alternatively, by further heating and drying the lithium halide complex at a temperature that removes the first solvent, the first solvent can be removed from the lithium halide complex to produce lithium halide. During heating and drying, the heating temperature can be adjusted as desired.

[0190] Drying under reduced pressure can be performed using, for example, a vacuum pump, and is preferably performed under vacuum from the viewpoint of shortening the drying time.

[0191] When drying is performed by heating, the drying can be performed at a temperature appropriate to the type of the first solvent and, if necessary, the second solvent and the third solvent, for example, at a temperature above the boiling point of these solvents. In this case, since it depends on the degree of reduced pressure, it cannot be determined in a general manner. However, the heating temperature is generally 5 to 100°C, preferably 10 to 85°C, more preferably 15 to 70°C, and even more preferably 20 to 60°C.

[0192] Furthermore, as a drying method, a method utilizing solid-liquid separation can also be preferably mentioned. Solid-liquid separation can be performed, for example, by decantation or using a centrifuge.

[0193] In the case of decantation, specifically, a mixture of lithium sulfide, halogen molecules, a first solvent, and a second solvent used as needed, or a mixture containing a third solvent used for washing as needed, is transferred to a container, and after solid precipitation, the first solvent, second solvent, and third solvent that become the supernatant are removed for drying.

[0194] (cleans and removes sulfur molecules)

[0195] The manufacturing method of this embodiment may further include cleaning and removing sulfur molecules. In this embodiment, as shown in the above reaction formula (2), sulfur molecules are generated as by-products by the reaction between lithium sulfide and halogen molecules. Therefore, by removing these sulfur molecules, a lithium halide compound with higher purity can be produced.

[0196] When a second solvent is used, since sulfur molecules are generally dissolved in the second solvent, the sulfur molecules can be removed by removing the second solvent. Therefore, it can be said that removing the solvent also essentially involves washing and removing the sulfur molecules. When a second solvent is not used, or even when a second solvent is used, it is preferable to perform washing and removal in addition to the above-mentioned solvent removal in order to further remove the sulfur molecules and thereby obtain a lithium halide compound of higher purity.

[0197] The washing can be performed after or before the solvent is removed. However, from the viewpoint of more efficiently removing the sulfur molecules, it is preferably performed after the solvent is removed. That is, the mixture containing the lithium halide compound and the sulfur molecules is washed. The mixture containing the lithium halide compound and the sulfur molecules is obtained by removing the first solvent and the second solvent from the mixture containing the lithium halide compound, the sulfur molecules, the first solvent, and the second solvent used as needed, obtained by the above mixing.

[0198] As a cleaning method, a third solvent is preferred because cleaning is easier. To facilitate the removal of sulfur molecules, a third solvent that can dissolve sulfur molecules is preferred. Examples of such solvents include those with a sulfur solubility (20°C) of preferably 0.1 g / L or greater, more preferably 0.3 g / L or greater, even more preferably 0.5 g / L or greater, and particularly preferably 1 g / L or greater. The upper limit is not limited, but is 600 g / L or less, 550 g / L or less, or 100 g / L or less. Specifically, the third solvent can be appropriately selected from the solvents exemplified as the second solvent. Similar to the second solvent, examples include hydrocarbon solvents such as aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons; and solvents containing carbon atoms, such as solvents containing carbon atoms and heteroatoms. Hydrocarbon solvents are preferred, aromatic hydrocarbons and aliphatic hydrocarbons are more preferred, aromatic hydrocarbons are further preferred, and toluene is particularly preferred. Therefore, it is preferred that the second and third solvents be the same (of the same type).

[0199] Regarding the washing of the mixture of lithium halide and sulfur molecules, when washing is performed using a third solvent, for example, the third solvent may be added to a mixture of the reactant lithium halide compound and the by-product sulfur molecules, obtained by removing the solvent from the mixture obtained by mixing lithium sulfide, halogen molecules, the first solvent, and the second solvent used as needed, and after the lithium halide compound is precipitated as a solid, washing may be performed by discarding the solvent as the supernatant liquid in the same manner as the above-mentioned decantation. Alternatively, the above-mentioned treatment may be repeated.

[0200] When washing is performed after solvent removal, and when a third solvent is used for washing, it is preferred to further remove the solvent after washing. This removes the third solvent and sulfur molecules, thereby further reducing the sulfur content in the lithium halide compound. In this case, the solvent removal can be performed by appropriately selecting from the above-mentioned solvent removal methods.

[0201] Thus, in the production method of this embodiment, the solvent removal may be performed twice. In this case, the first solvent removal is to remove the first solvent and the second solvent from the mixture containing the lithium halide compound, sulfur molecules, the first solvent, and the second solvent used as needed, obtained by the above mixing, and to remove the sulfur molecules contained in the second solvent. The second solvent removal is to remove the third solvent from the mixture containing the lithium halide compound, sulfur molecules, and the third solvent after washing with the third solvent, and to remove the sulfur molecules contained in the third solvent.

[0202] As described above, the lithium halide compound obtained by the production method of this embodiment includes, in addition to lithium halide, a lithium halide complex and a lithium halide composite. These lithium halide compounds are all compounds with low water content and high quality even without water removal, and are therefore suitable for use as raw materials for sulfide solid electrolytes.

[0203] The lithium halide compound obtained by the production method of this embodiment contains water at a content of 1% by mass or less, preferably 0.5% by mass or less, or 0.3% by mass or less. The lower limit is generally about 0.01% by mass. In this specification, the water content of the lithium halide compound, like the water content in lithium sulfide, is a value measured using a Karl Fischer titrator using the vaporization method at 280°C.

[0204] The lithium halide compound obtained by the production method of this embodiment is a porous compound as described above, and its specific surface area measured by the BET method is 1.0 m 2 / g or more, further 5.0m 2 / g or above, 10.0m 2 / g or more. In addition, the upper limit is usually 80.0m 2 / g or less. In this specification, the specific surface area is a value measured by the BET method (gas adsorption method). As the gas, nitrogen (nitrogen method) or krypton (krypton method) can be used, and the measurement method can be appropriately selected according to the size of the specific surface area. The specific surface area can be measured using a commercially available device such as a gas adsorption measurement device (for example, AUTOSORB6 (manufactured by Sysmex Co., Ltd.)).

[0205] (Method for producing sulfide solid electrolyte)

[0206] As described above, the lithium halide compound obtained by the production method of this embodiment is preferably used as a raw material for a sulfide solid electrolyte. For example, a sulfide solid electrolyte can be obtained by a production method comprising reacting the lithium halide compound obtained by the production method of this embodiment, a lithium compound other than a lithium halide, and a phosphorus compound. Production methods comprising reacting a lithium halide compound, a lithium compound other than a lithium halide, and a phosphorus compound are well-known methods, and specific processing and operations can be carried out according to well-known methods.

[0207] Examples of the lithium halide compound include lithium fluoride, lithium chloride, lithium bromide, lithium iodide, and the like, depending on the halogen molecule used, with lithium bromide and lithium iodide being preferred.

[0208] Preferred examples of lithium compounds other than lithium halide compounds include lithium sulfide (Li 2 S), lithium oxide (Li 2 O), and lithium carbonate (Li 2 CO 3 ). Among them, lithium sulfide is preferred from the viewpoint of ion conductivity.

[0209] As the phosphorus compound, for example, phosphorus sulfides such as phosphorus trisulfide (P2S3) and phosphorus pentasulfide (P2S5), phosphoric acid compounds such as sodium phosphate (Na3PO4) and lithium phosphate (Li3PO4) can be preferably exemplified. Among them, phosphorus sulfide is preferred, and phosphorus pentasulfide (P2S5) is more preferred. As long as phosphorus compounds such as phosphorus pentasulfide (P2S5) are industrially manufactured and sold, they can be used without particular limitation. These phosphorus compounds can be used alone or in combination.

[0210] In addition, as substances containing halogen atoms other than lithium halide compounds, halogen molecules, namely fluorine (F2), chlorine (Cl2), bromine (Br2), and iodine (I2), can also be used. Preferably, chlorine (Cl2), bromine (Br2), and iodine (I2) are used, and more preferably, bromine (Br2) and iodine (I2) are used.

[0211] Among the above, lithium sulfide, phosphorus pentasulfide and a lithium halide compound; and a combination of lithium sulfide, phosphorus pentasulfide, a lithium halide compound and a halogen molecule are preferred.

[0212] When lithium sulfide, phosphorus pentasulfide, and lithium halide are used as raw materials, the ratio of lithium sulfide to the total of lithium sulfide and phosphorus pentasulfide is preferably 70 to 80 mol%, more preferably 72 to 78 mol%, and even more preferably 74 to 78 mol%, from the viewpoint of obtaining higher chemical stability and higher ion conductivity.

[0213] In addition, when lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of improving ion conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, further preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0214] When lithium bromide and lithium iodide are used in combination as the lithium halide, from the viewpoint of improving ion conductivity, the ratio of lithium bromide to the total of lithium bromide and lithium iodide is preferably 1 to 99 mol%, more preferably 20 to 90 mol%, further preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0215] When lithium sulfide, phosphorus pentasulfide, a halogen monomer, and a lithium halide are used, the content of the halogen monomer relative to the total amount of these (α mol%) and the content of the lithium halide relative to the total amount of these (β mol%) preferably satisfy the following mathematical formula (2), more preferably satisfy the following mathematical formula (3), further preferably satisfy the following mathematical formula (4), and even more preferably satisfy the following mathematical formula (5).

[0216] 2≤2α+β≤100…(2)

[0217] 4≤2α+β≤80…(3)

[0218] 6≤2α+β≤50…(4)

[0219] 6≤2α+β≤30…(5)

[0220] When reacting a lithium halide compound, a lithium compound other than a lithium halide, and a phosphorus compound, the reaction can be carried out by subjecting these raw materials to treatments such as mixing, stirring, and pulverizing. For example, when performing a mixing or stirring treatment, a mechanical stirring mixer used for mixing in the production method of this embodiment can be used. Furthermore, when performing a pulverization treatment, a device generally referred to as a pulverizer, such as a media pulverizer such as a ball mill or a bead mill, can be used.

[0221] In addition, when reacting by mixing and stirring, starting from the point of obtaining a solid electrolyte without pulverizing, it is preferred that the complexing agent exemplified as the preferred solvent for the above-mentioned first solvent is stirred (mixed) together with various solvents used as needed (for example, the solvent exemplified as the above-mentioned second solvent, etc.), lithium halide compounds, lithium compounds other than lithium halides, and raw materials of phosphorus compounds. In this case, if stirring (mixing) is performed, a slurry comprising an electrolyte precursor composed of the raw material and the complexing agent, a liquid complexing agent, and a solvent can be obtained, which is then dried to remove the liquid complexing agent and solvent, and further heated to obtain a sulfide solid electrolyte.

[0222] The above-mentioned drying can be carried out by any of the drying methods in the manufacturing method of this embodiment. Since the solvent used is the same as the solvent used in the manufacturing method of this embodiment, the temperature conditions when drying by heating are the same as the heating drying conditions in the manufacturing method of this embodiment.

[0223] The sulfide solid electrolyte obtained by the above method contains lithium, sulfur, phosphorus, and halogen elements and is essentially an amorphous sulfide solid electrolyte. In this specification, an amorphous sulfide solid electrolyte refers to an X-ray diffraction pattern in which substantially no peaks other than those derived from the material are observed, regardless of the presence or absence of peaks derived from the raw materials of the solid electrolyte.

[0224] Representative examples of amorphous sulfide solid electrolytes obtained using a lithium halide compound obtained by the production method of this embodiment include, for example, solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr. Solid electrolytes further containing other elements such as oxygen and silicon, such as Li2S-P2S5-Li2O-LiI and Li2S-SiS2-P2S5-LiI, are preferred. From the perspective of achieving higher ionic conductivity, solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as Li2S-P2S5-LiI, Li2S-P2S5-LiCl, Li2S-P2S5-LiBr, and Li2S-P2S5-LiI-LiBr, are preferred.

[0225] The types of elements constituting the amorphous solid electrolyte can be confirmed by, for example, an ICP emission spectrometer.

[0226] Furthermore, the above-mentioned amorphous sulfide solid electrolyte can be converted into a crystalline sulfide solid electrolyte by further heating. In this specification, a crystalline solid electrolyte refers to a solid electrolyte in which a peak originating from the solid electrolyte is observed in the X-ray diffraction pattern during X-ray diffraction measurement, regardless of whether or not peaks originating from the solid electrolyte's raw materials are present. That is, a crystalline solid electrolyte contains a crystalline structure originating from the solid electrolyte, and may contain a portion or all of the crystalline structure originating from the solid electrolyte. Furthermore, as long as a crystalline solid electrolyte exhibits the above-mentioned X-ray diffraction pattern, it may also contain a portion of an amorphous solid electrolyte. Therefore, crystalline solid electrolytes include so-called glass ceramics obtained by heating an amorphous solid electrolyte to a temperature above its crystallization temperature.

[0227] Since the heating temperature can be appropriately selected depending on the structure of the amorphous sulfide solid electrolyte, it cannot be generally stated. For example, using a differential thermal analyzer (DTA) apparatus, differential thermal analysis (DTA) is performed under the condition of a temperature increase of 10°C / minute. The starting point is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, with the temperature at the peak top of the exothermic peak observed on the lowest temperature side as the starting point. The upper limit is not particularly limited, but can be approximately 40°C or lower. Specifically, it is generally preferably 130°C or higher, more preferably 135°C or higher, and even more preferably 140°C or higher. The upper limit is not particularly limited, but is preferably 300°C or lower, more preferably 280°C or lower, and even more preferably 250°C or lower.

[0228] The heating time is not particularly limited as long as it is a time sufficient to obtain the desired crystalline sulfide solid electrolyte, but is preferably 1 minute or longer, more preferably 10 minutes or longer, even more preferably 30 minutes or longer, and even more preferably 1 hour or longer. The upper limit of the heating time is not particularly limited, but is preferably 24 hours or shorter, more preferably 10 hours or shorter, even more preferably 5 hours or shorter, and even more preferably 3 hours or shorter.

[0229] In addition, heating is preferably carried out in an inert gas atmosphere (for example, a nitrogen atmosphere, an argon atmosphere) or in a reduced pressure atmosphere (particularly in a vacuum). This is because it is possible to prevent degradation (for example, oxidation) of the crystalline solid electrolyte. The method of heating is not particularly limited, and for example, methods using a hot plate, a vacuum heating device, an argon atmosphere furnace, a firing furnace, and the like can be exemplified. In addition, in industry, a horizontal dryer, a horizontal vibrating flow dryer, etc. having a heating unit and a feeding mechanism can also be used, and the method can be selected according to the processing capacity of the heating.

[0230] Examples of crystalline sulfide solid electrolytes obtained using the lithium halide compound obtained by the production method of this embodiment include those having a Li3PS4 crystal structure, a Li4P2S6 crystal structure, a Li7PS6 crystal structure, a Li7P3S 11 A sulfide solid electrolyte having a crystal structure, a crystal structure having peaks near 2θ=20.2° and 23.6° (for example, Japanese Patent Application Laid-Open No. 2013-16423), or the like.

[0231] In addition, Li 4-x Ge 1-x P x S4 type sulfide crystalline lithium superion conductor region II (thio-LISICONRegion II) type crystal structure (see Kanno et al., Journal of The Electrochemical Society, 148 (7) A742-746 (2001)), and Li 4-x Ge 1-x P x S4 type thio-LISICON Region II type crystal structure (see Solid State Ionics, 177 (2006), 2721-2725). From the perspective of ionic conductivity, the thio-LISICON Region II type crystal structure is preferred. Here, the "thio-LISICON Region II type crystal structure" means Li 4-x Ge 1-x P x S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) type crystal structure, and Li 4-x Ge 1-x P x Any crystal structure similar to the S4 type sulfide crystalline lithium superion conductor region II (thio-LISICON Region II) type crystal structure.

[0232] Since the sulfide solid electrolyte obtained in this way is a sulfide solid electrolyte obtained using a water-free lithium halide compound as a raw material, it has low moisture content, high ion conductivity, and excellent battery performance. Therefore, the sulfide solid electrolyte obtained using the lithium halide compound obtained by the manufacturing method of this embodiment can be used for any application requiring lithium ion conductivity, and is particularly preferably used in batteries. The sulfide solid electrolyte can be used in the positive electrode layer, the negative electrode layer, or the electrolyte layer. In addition, each layer can be manufactured by a known method.

[0233] Furthermore, the battery preferably includes a current collector in addition to the positive electrode layer, electrolyte layer, and negative electrode layer. A known current collector can be used. For example, a layer obtained by coating a substance that reacts with a sulfide solid electrolyte, such as Au, Pt, Al, Ti, or Cu, with Au or the like can be used.

[0234] Example

[0235] Next, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[0236] (Manufacturing Example: Manufacture of Lithium Sulfide (Li2S))

[0237] Toluene (manufactured by Sumitomo Corporation) was used as a non-aqueous medium for dehydration treatment. Under a nitrogen flow, 303.8 kg of toluene having a moisture content of 100 ppm as measured by a Karl Fischer titrator was added to a 500 L stainless steel reactor. Subsequently, 33.8 kg of anhydrous lithium hydroxide (manufactured by Honjo Chemical Co., Ltd.) was added and maintained at 95° C. while stirring at 131 rpm with a twinstir stirring blade.

[0238] Hydrogen sulfide (manufactured by Sumitomo Seika Co., Ltd.) was blown into the slurry at a rate of 100 L / min while the temperature was raised to 104°C. A azeotropic gas of water and toluene was continuously discharged from the reactor. This azeotropic gas was condensed using a condenser outside the system to remove water. During this time, an amount of toluene equal to the distilled toluene was continuously supplied to maintain a constant reaction liquid level.

[0239] The amount of water in the condensate gradually decreased, and no distilled water was observed 24 hours after the introduction of hydrogen sulfide. During the reaction, the solid was dispersed in toluene and stirred, and no water separated from the toluene was present.

[0240] Then, the hydrogen sulfide was switched to nitrogen gas, and the nitrogen gas was circulated at 100 L / min for 1 hour.

[0241] (Example 1)

[0242] Under a nitrogen atmosphere, 0.50 g (10.9 mmol) of lithium sulfide (Li2S) was introduced into a Schlenk flask (capacity: 100 mL) with a stirrer. 20 mL of toluene was added as a second solvent, and after the stirrer was rotated, 2.76 g (10.9 mmol) of iodine was added as a halogen molecule. The lithium sulfide and iodine were mixed in the second solvent for 2 hours, and 4 mL of ethyl acetate that had been dehydrated was added as the first solvent, and the mixture was further mixed for 2 hours. After visually confirming that there was no coloring caused by iodine in the supernatant, the toluene and ethyl acetate used as solvents were removed under vacuum, and then heated and dried at 100°C for 2 hours. After drying, 50 mL of toluene was added and stirred for 10 minutes. After stirring, the mixture was allowed to stand to allow the solid component to settle, and 40 mL of supernatant was removed. This decantation was repeated 3 times. After decantation, the mixture was heated and dried at 100°C for 2 hours under vacuum to obtain a powder.

[0243] The powder obtained was subjected to powder X-ray diffraction (XRD) measurement by the following method. In addition, the lithium sulfide used as the raw material was also subjected to XRD measurement by the same method. The results of these XRD measurements are shown in Figure 1 .like Figure 1 As shown, the obtained powder had a peak due to lithium sulfide disappeared and a peak due to lithium iodide remained, confirming that it was a powder of lithium iodide.

[0244] In this specification, powder X-ray diffraction (XRD) measurement is performed as follows.

[0245] The powders obtained in the examples and comparative examples were filled into a 20 mm diameter, 0.2 mm deep cell and leveled with glass to prepare a sample. The sample was sealed with a Kapton film for XRD to prevent contact with air, and measurements were performed under the following conditions.

[0246] Measuring device: D2 PHASER, manufactured by Bruker Corporation

[0247] Tube voltage: 30kV

[0248] Tube current: 10mA

[0249] X-ray wavelength: Cu-Kα ray

[0250] Optical system: Concentration method

[0251] Slit configuration: Soller slit 4°, divergence slit 1mm, Kβ filter (Ni plate)

[0252] Detector: semiconductor detector

[0253] Measuring range: 2θ = 10-60 degrees

[0254] Step width, scanning speed: 0.05deg, 0.05deg / second

[0255] (Example 2)

[0256] Under a nitrogen atmosphere, 0.50 g (10.9 mmol) of lithium sulfide (Li2S) was introduced into a Schlenk flask (capacity: 100 mL) equipped with a stirrer. 20 mL of toluene was added as a second solvent, and after rotating the stirrer, 2.76 g (10.9 mmol) of iodine was added as a halogen molecule. The lithium sulfide and iodine were mixed in the second solvent for 2 hours. 4 mL of tetramethylethylenediamine (TMEDA) was added as the first solvent and mixed for a further 2 hours. After mixing, the toluene and tetramethylethylenediamine used as solvents were removed under vacuum, and the mixture was further dried by heating at 100°C for 2 hours to obtain a powder.

[0257] The obtained powder was subjected to powder X-ray diffraction (XRD) measurement in the same manner as in Example 1. The results of the XRD measurement of the powder are shown in FIG. Figure 2 Regarding this powder, although the peak of lithium sulfide disappeared, a peak different from the peak of lithium iodide in Example 1 appeared, and it was considered not to be lithium sulfide or lithium iodide, but to be a lithium iodide complex formed by lithium iodide and tetramethylethylenediamine.

[0258] The powder was then dried at 200°C for 2 hours. The powder obtained by drying was subjected to powder X-ray diffraction (XRD) measurement in the same manner as in Example 1. The results of the XRD measurement of the powder are shown in FIG. Figure 2 This powder had the same peak as that of the powder obtained in Example 1, namely, lithium iodide, and was confirmed to be lithium iodide.

[0259] (Example 3)

[0260] Under a nitrogen atmosphere, 0.50 g (10.9 mmol) of lithium sulfide (Li2S) was introduced into a Schlenk flask (capacity: 100 mL) equipped with a stirrer. 20 mL of toluene was added as a second solvent, and after rotating the stirrer, 0.87 g (5.44 mmol) of bromine and 1.38 g (5.44 mmol) of iodine were added as halogen molecules. The lithium sulfide, bromine, and iodine were mixed in the second solvent for 2 hours. 4 mL of dehydrated ethyl acetate was added as the first solvent, and mixing was continued for a further 2 hours. After mixing, the toluene and ethyl acetate used as solvents were removed under vacuum, and the mixture was further dried by heating at 100°C for 2 hours to obtain a powder.

[0261] The obtained powder was subjected to powder X-ray diffraction (XRD) measurement in the same manner as in Example 1. Figure 3As shown, the obtained powder had no peak attributable to lithium sulfide and had peaks attributable to lithium bromide and lithium iodide, confirming that it was a powder of lithium bromide and lithium iodide.

[0262] (Example 4)

[0263] Under a nitrogen atmosphere, 0.50 g (10.9 mmol) of lithium sulfide (Li2S) was introduced into a Schlenk flask (capacity: 100 mL) equipped with a stirrer. 20 mL of toluene was added as a second solvent, and after rotating the stirrer, 2.76 g (10.9 mmol) of iodine was added as a halogen molecule. The lithium sulfide and iodine were mixed in the second solvent for 2 hours. 4 mL of dehydrated tetrahydrofuran (THF) was added as the first solvent and mixed for a further 2 hours. After mixing, the toluene and tetrahydrofuran used as solvents were removed under vacuum at room temperature (23°C) to obtain a powder.

[0264] The obtained powder was subjected to powder X-ray diffraction (XRD) measurement in the same manner as in Example 1. The results of the XRD measurement of the powder are shown in FIG. Figure 4 Regarding this powder, although the peak of lithium sulfide disappeared, a peak different from the peak of lithium iodide in Example 1 appeared, and it was considered not to be lithium sulfide or lithium iodide, but to be a lithium iodide complex formed by lithium iodide and tetrahydrofuran.

[0265] The powder was then heated and dried at 100°C for 2 hours. The powder obtained by drying was subjected to powder X-ray diffraction (XRD) measurement in the same manner as in Example 1. The results of the XRD measurement of the powder are shown in FIG. Figure 4 This powder had the same peak as that of the powder obtained in Example 1, namely, lithium iodide, and was confirmed to be lithium iodide.

[0266] (Example 5)

[0267] Under a nitrogen atmosphere, 0.50 g (10.9 mmol) of lithium sulfide (Li2S) was introduced into a Schlenk flask (capacity: 100 mL) equipped with a stirrer. 20 mL of cyclohexane was added as a second solvent, and after rotating the stirrer, 2.76 g (10.9 mmol) of iodine, a halogen molecule, was added. The lithium sulfide and iodine were mixed in the second solvent for 2 hours. 4 mL of dehydrated tetrahydrofuran (THF) was added as the first solvent and mixed for a further 2 hours. After mixing, the toluene and tetrahydrofuran used as solvents were removed under vacuum at room temperature (23°C) to obtain a powder.

[0268] The powder was then heated and dried at 100°C for 2 hours. The powder obtained by drying was subjected to powder X-ray diffraction (XRD) measurement in the same manner as in Example 1. The results of the XRD measurement of the powder are shown in FIG. Figure 5 This powder had the same peak as that of the powder obtained in Example 1, namely, lithium iodide, and was confirmed to be lithium iodide.

[0269] (Comparative Example 1)

[0270] Under a nitrogen atmosphere, 0.50 g (10.9 mmol) of lithium sulfide (Li2S) was introduced into a Schlenk flask (capacity: 100 mL) with a stirrer. 20 mL of toluene was added as a second solvent, and after rotating the stirrer, 2.76 g (10.9 mmol) of iodine was added as a halogen molecule, and the lithium sulfide and iodine were mixed in the second solvent for 50 hours. After mixing, the mixture was allowed to stand to allow powder to settle, and the supernatant was extracted and treated with an aqueous sodium thiosulfate solution. Composition analysis by ICP analysis (inductively coupled plasma emission spectrometry) revealed that 28% of the iodine used as the raw material remained unreacted.

[0271] The sample obtained in Comparative Example 1 was photographed using a scanning electron microscope (SEM) and subjected to elemental analysis using an energy dispersive X-ray spectrometer (EDS). The SEM image obtained by the scanning electron microscope (SEM) is shown in FIG. Figure 6 .according to Figure 6 It is seen that lithium iodide (represented as a lighter region of LiI in the figure) is generated around lithium sulfide (represented as a denser region of Li2S in the figure). This confirms that unreacted lithium sulfide remains in the method of Comparative Example 1.

[0272] In addition, the EDS images of the elemental analysis results of sulfur and iodine in the sample using an energy dispersive X-ray spectrometer (EDS device) are shown in FIG. Figure 7 and Figure 8 The EDS image results also confirmed that sulfur was present in the region where lithium sulfide existed, and iodine was present in the region where lithium iodide existed, and that sulfur remained due to unreacted lithium sulfide.

[0273] Industrial Applicability

[0274] The production method of the present invention enables the production of lithium halide compounds, particularly lithium bromide and lithium iodide, with low water content, without requiring a direct water removal step, with high reaction efficiency and in an industrially advantageous manner. The resulting lithium halide compounds, due to their low water content, can be preferably used as raw materials for sulfide solid electrolytes.

Claims

1. A method for producing a lithium halide compound, characterized in that: include: mixing lithium sulfide, a halogen molecule of at least one of bromine and iodine, and a second solvent; Then, adding the first solvent and mixing; as well as removing the first solvent and the second solvent, The first solvent is a solvent that dissolves lithium halide containing the halogen element of the halogen molecule. The second solvent is a solvent of lithium halide that does not dissolve the halogen element including the halogen molecule, The first solvent is a solvent having a solubility of lithium bromide and lithium iodide of 1 g / L or more and 1000 g / L or less. The second solvent is a solvent in which the solubility of lithium bromide and lithium iodide is less than 1 g / L.

2. The method for producing a lithium halide compound according to claim 1, wherein The lithium halide compound includes a lithium halide complex.

3. The method for producing a lithium halide compound according to claim 1 or 2, wherein: The first solvent is a solvent having a solubility of lithium bromide and lithium iodide of 5 g / L or more and 1000 g / L or less.

4. The method for producing a lithium halide compound according to claim 1 or 2, wherein: The first solvent is an aprotic solvent having at least one functional group selected from an ester group, an ether group, and an amino group.

5. The method for producing a lithium halide compound according to claim 4, wherein The aprotic solvent having an ester group is an ester compound selected from aliphatic esters, alicyclic esters, heterocyclic esters, and aromatic esters.

6. The method for producing a lithium halide compound according to claim 5, wherein The aprotic solvent having the ester group is an ester compound selected from aliphatic esters.

7. The method for producing a lithium halide compound according to claim 5 or 6, wherein: The aliphatic ester is an ester compound having 2 or more and 10 or less carbon atoms.

8. The method for producing a lithium halide compound according to claim 4, wherein The aprotic solvent having an ether group is an ether compound selected from aliphatic ethers, alicyclic ethers, heterocyclic ethers, and aromatic ethers.

9. The method for producing a lithium halide compound according to claim 8, wherein The aprotic solvent having the ether group is an ether compound selected from alicyclic ethers.

10. The method for producing a lithium halide compound according to claim 8 or 9, wherein: The alicyclic ether is an ether compound having 3 to 16 carbon atoms.

11. The method for producing a lithium halide compound according to claim 4, wherein The aprotic solvent having an amino group is an amine compound selected from aliphatic amines, alicyclic amines, heterocyclic amines, and aromatic amines.

12. The method for producing a lithium halide compound according to claim 11, wherein The aprotic solvent having the amino group is an amine compound selected from aliphatic amines.

13. The method for producing a lithium halide compound according to claim 11 or 12, wherein: The aliphatic amine has a carbon number of 2 or more and 10 or less.

14. The method for producing a lithium halide compound according to claim 4, wherein The aprotic solvent having the amino group is a tertiary amine having a tertiary amino group.

15. The method for producing a lithium halide compound according to claim 4, wherein: The aprotic solvent having the amino group is a tertiary diamine having two tertiary amino groups.

16. The method for producing a lithium halide compound according to claim 4, wherein: The aprotic solvent having the amino group is an aliphatic tertiary diamine having two tertiary amino groups at both ends.

17. The method for producing a lithium halide compound according to claim 1 or 2, wherein: The usage-amount of the first solvent is 100 mL or more and 3000 mL or less relative to 1 kg of the total amount of the lithium sulfide and the halogen molecules.

18. The method for producing a lithium halide compound according to claim 1 or 2, wherein: The usage-amount of the first solvent is 300 mL or more and 1550 mL or less relative to 1 kg of the total amount of the lithium sulfide and the halogen molecules.

19. The method for producing a lithium halide compound according to claim 1 or 2, wherein: The first solvent is removed by a method selected from solid-liquid separation, reduced pressure drying, and heat drying.

20. The method for producing a lithium halide compound according to claim 19, wherein: The first solvent is removed by filtration.

21. The method for producing a lithium halide compound according to claim 1, wherein The second solvent is a solvent in which the solubility of lithium bromide and lithium iodide is greater than or equal to 0.01 mg / L and less than 1 g / L.

22. The method for producing a lithium halide compound according to claim 1, wherein The second solvent is a solvent in which the solubility of lithium bromide and lithium iodide is 0.01 mg / L or more and 0.5 g / L or less.

23. The method for producing a lithium halide compound according to claim 1, wherein The second solvent is a solvent having a solubility of halogen molecules of 0.03 mass % or more and 60 mass % or less.

24. The method for producing a lithium halide compound according to claim 1, wherein The second solvent is a solvent having a solubility of halogen molecules of 0.1% by mass or more and 10% by mass or less.

25. The method for producing a lithium halide compound according to claim 1, wherein The second solvent has a sulfur solubility of 0.3 g / L or more.

26. The method for producing a lithium halide compound according to claim 1, wherein The second solvent has a sulfur solubility of 0.3 g / L to 600 g / L.

27. The method for producing a lithium halide compound according to claim 1, wherein The second solvent is at least one selected from aromatic hydrocarbons, alicyclic hydrocarbons, and aliphatic hydrocarbons.

28. The method for producing a lithium halide compound according to claim 1, wherein The second solvent is at least one selected from aromatic hydrocarbons and aliphatic hydrocarbons.

29. The method for producing a lithium halide compound according to claim 1, wherein The second solvent is at least one selected from aromatic hydrocarbons and alicyclic hydrocarbons.

30. The method for producing a lithium halide compound according to claim 1, wherein The second solvent has a boiling point of 150° C. or lower.

31. The method for producing a lithium halide compound according to claim 1, wherein The second solvent is removed by a method selected from solid-liquid separation, reduced pressure drying, and heat drying.

32. The method for producing a lithium halide compound according to claim 31, wherein The removal of the second solvent is performed by filtration.

33. The method for producing a lithium halide compound according to claim 1 or 2, wherein: It also involves cleaning and removing sulfur molecules.

34. The method for producing a lithium halide compound according to claim 33, wherein In the washing and removing, a third solvent is used.

35. The method for producing a lithium halide compound according to claim 34, wherein: The third solvent is removed by at least one treatment selected from filtration and heating under reduced pressure.

36. The method for producing a lithium halide compound according to claim 33, wherein: The cleaning and removal of sulfur molecules are performed after removing the first solvent and removing the second solvent.

37. The method for producing a lithium halide compound according to any one of claims 34 to 36, wherein The third solvent is a solvent having a solubility of sulfur molecules of 0.1 g / L or more.

38. The method for producing a lithium halide compound according to any one of claims 34 to 36, wherein The third solvent is a solvent having a solubility of sulfur molecules of not less than 0.1 g / L and not more than 600 g / L.

39. The method for producing a lithium halide compound according to any one of claims 34 to 36, wherein The third solvent is at least one selected from aromatic hydrocarbons and aliphatic hydrocarbons.

40. The method for producing a lithium halide compound according to any one of claims 34 to 36, wherein The second solvent is the same as the third solvent.

41. The method for producing a lithium halide compound according to claim 34, wherein The third solvent is removed by a method selected from solid-liquid separation, reduced pressure drying, and heat drying.

42. The method for producing a lithium halide compound according to claim 41, wherein The removal of the third solvent is performed by filtering.

Images