Method for producing lithium halide

Abstract

To provide a method for producing lithium halide which does not involve a step of directly removing moisture, does not use an elemental halogen which is difficult to handle, and does not require excessive energy for production.SOLUTION: A method for producing lithium halide comprises mixing lithium carbonate and ammonium halide.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] With the rapid spread of information-related devices and communication devices such as personal computers, video cameras, and mobile phones in recent years, the development of batteries used as their power sources has been emphasized. Conventionally, an electrolyte solution containing a flammable organic solvent has been used in batteries for such applications. However, by making the battery all-solid-state, a flammable organic solvent is not used inside the battery, the safety device can be simplified, and the manufacturing cost and productivity are excellent. Therefore, the development of all-solid-state batteries in which the electrolyte solution is replaced with a solid electrolyte layer has been carried out.

[0003] As a solid electrolyte used for the solid electrolyte layer, sulfide solid electrolytes have been conventionally known. For example, it is known that a sulfide glass is produced by reacting lithium sulfide and phosphorus sulfide, and a glass-ceramic electrolyte having high ionic conductivity can be obtained by subjecting this sulfide glass to heat treatment (see, for example, Patent Document 1). Further, with the demand for higher ionic conductivity, a production method using lithium halide as a sulfide solid electrolyte containing a halogen atom is also known (see, for example, Patent Document 2).

[0004] Lithium halide used as a raw material for producing a sulfide solid electrolyte containing a halogen atom is generally produced as a hydrate because an aqueous solution raw material is used in the synthesis process or the reaction is carried out in water (see, for example, Patent Documents 3 and 4). Since the ionic conductivity of the sulfide solid electrolyte may decrease if lithium halide contains moisture, it is necessary to remove moisture from lithium halide, and methods such as azeotroping with an organic solvent and drying for removal (see, for example, Patent Document 4) have been studied. However, in any case, it is not easy to remove moisture from lithium halide hydrate. Also disclosed is a method for producing lithium halide using lithium sulfide and ammonium halide as raw materials (see, for example, Patent Document 5). Furthermore, a method for obtaining anhydrous lithium halide by reacting lithium carbonate with hydrochloric acid is also known (see, for example, Patent Document 6).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention has been made in view of such circumstances, and an object thereof is to provide a method for producing lithium halide that does not involve a step of directly removing moisture, does not use elemental halogen that makes handling complicated, and does not require excessive energy for production.

Means for Solving the Problems

[0007] The method for producing a lithium halide compound according to the present invention is a method for producing lithium halide including mixing lithium carbonate and ammonium halide.

Effects of the Invention

[0008] According to the present invention, it is possible to provide a method for producing lithium halide that does not involve a step of directly removing moisture, does not use elemental halogens that are cumbersome to handle, and does not require excessive energy for production.

Brief Description of the Drawings

[0009]

Figure 1

Modes for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention (hereinafter sometimes referred to as "the present embodiments") will be described. In this specification, the upper and lower limit numerical values related to the numerical ranges of "above", "below", and "~" are numerical values that can be arbitrarily combined, and the numerical values of the examples can also be used as the upper and lower limit numerical values.

[0011] (Findings Obtained by the Inventors in Reaching the Present Invention) As a result of intensive studies to solve the above problems, the present inventors have found the following matters and have completed the present invention. As described above, in the methods of Patent Documents 1 to 4, it is necessary to remove moisture, but the removal of moisture is not easy. On the other hand, although the manufacturing method described in Patent Document 5 does not require moisture removal like the methods of Patent Documents 1 to 4, it uses expensive lithium sulfide as a raw material. In promoting the mass production of sulfide solid electrolytes, in the production of lithium halide used as a raw material, it is necessary to expand the options for lithium sources, and a manufacturing method with better cost performance is required. In addition, regarding the method for obtaining anhydrous lithium halide by reacting lithium carbonate and hydrochloric acid disclosed as a prior art in Patent Document 6, there is a problem that a large amount of labor is required for dehydration. Therefore, when the present inventors examined a method for producing lithium halide using other relatively inexpensive lithium compounds as raw materials, they found that it is possible to produce lithium halide using lithium carbonate as a raw material.

[0012] [Method for producing lithium halide] The method for producing lithium halide according to the first aspect of the present embodiment is a method for producing lithium halide, which includes mixing lithium carbonate and ammonium halide.

[0013] According to the first aspect, since ammonium halide is used as a raw material for supplying a halogen element, there is no need to use elemental halogen, which is cumbersome to handle, as a raw material. In addition, since the by-products generated by using these raw materials are ammonia, moisture, and carbon dioxide, which are gases, it is extremely easy to remove the by-products.

[0014] The method for producing lithium halide according to the second aspect of the present embodiment is such that, in the method for producing lithium halide according to the first aspect, the mixing ratio of the lithium carbonate and the ammonium halide is in the ratio of 1.50 to 2.50 moles of ammonium halide per 1 mole of lithium carbonate. According to the second aspect, it becomes possible to efficiently convert lithium carbonate, which is a raw material, into lithium halide.

[0015] The method for producing lithium halide according to the third aspect of the present embodiment is such that, in the method for producing lithium halide according to the first or second aspect, the lithium carbonate and the ammonium halide are preliminarily mixed and then further heated and mixed. By preliminarily mixing lithium carbonate and ammonium halide and then heating and mixing, the reaction can be promoted efficiently.

[0016] The method for producing lithium halide according to the fourth aspect of the present embodiment is such that, in the method for producing lithium halide according to the third aspect, the temperature condition of the heating and mixing is 90 to 400 °C. By setting the temperature condition during heating and mixing within the above range, the reaction can be promoted, and lithium halide can be obtained efficiently.

[0017] The method for producing lithium halide according to the fifth aspect of the present embodiment is that, in the production method of the third or fourth aspect, the heat mixing is performed under reduced pressure or in an inert gas atmosphere. Performing the heat mixing under reduced pressure or in an inert gas atmosphere is preferable from the viewpoint of suppressing side reactions.

[0018] The method for producing a sulfide solid electrolyte according to the sixth aspect of the present embodiment includes reacting lithium halide obtained by the production method of the first to fifth aspects with a phosphorus compound. According to the above method, it becomes possible to produce a sulfide solid electrolyte using lithium carbonate as a lithium source.

[0019] The method for producing a sulfide solid electrolyte according to the seventh aspect of the present embodiment is that, in the production method of the sixth aspect, further, a lithium compound other than lithium halide is reacted. The lithium compound other than lithium halide to be reacted in the present embodiment is prepared separately from the above-mentioned lithium halide and phosphorus compound.

[0020] Hereinafter, the production method of the present embodiment will be described in more detail in accordance with the above embodiments.

[0021] [Lithium carbonate] The lithium carbonate used in the production method of the present embodiment is usually in the form of particles, and may be a commercially available product, or a product produced by a known method can also be used.

[0022] The average particle size (D 50 ) of the lithium carbonate used in the production method of the present embodiment is preferably 0.1 μm or more and 200 μm or less, more preferably 0.3 μm or more and 150 μm or less, still more preferably 0.5 μm or more and 100 μm or less. In this specification, the average particle size (D 50) is the particle diameter at which, when drawing a cumulative particle size distribution curve, the cumulative value reaches 50% of the total starting from the particle with the smallest particle diameter. The volume distribution is, for example, the average particle diameter that can be measured using a laser diffraction / scattering particle size distribution measuring device.

[0023] Lithium carbonate preferably contains a small amount of moisture as an impurity from the viewpoint of reducing the moisture content in the resulting lithium halide and further, when using lithium halide as a raw material for a sulfide solid electrolyte, reducing the moisture content in the solid electrolyte and suppressing a decrease in ionic conductivity and battery performance due to water. The moisture content in lithium carbonate is preferably 1.5% by mass or less, more preferably 1% by mass or less, still more preferably 0.5% by mass or less. Also, as the lower limit, although there is no particular limitation because the less the better, it is usually about 0.1% by mass. In this specification, the moisture content in lithium carbonate is the value measured by a Karl Fischer moisture meter under the conditions of the vaporization method and 280°C.

[0024] [Ammonium halide] As the ammonium halide used in the production method of this embodiment, one corresponding to the desired lithium halide may be adopted. It is preferable to use one or more selected from ammonium fluoride (NH 4 F), ammonium chloride (NH 4 Cl), ammonium bromide (NH 4 Br), and ammonium iodide (NH 4 I). Among them, it is more preferable to use at least one selected from ammonium bromide (NH 4 Br) and ammonium iodide (NH 4 I).

[0025] In the manufacturing method of the present embodiment, lithium carbonate and ammonium halide react according to the reaction formulas shown by the following reaction formulas (1) to (3). Therefore, the mixing ratio of lithium carbonate and ammonium halide is preferably 1.50 to 2.50 moles of ammonium halide with respect to 1 mole of lithium carbonate, more preferably 1.70 to 2.30 moles, and even more preferably 1.80 to 2.20 moles.

[0026] Li 2 CO 3 +2NH 4 X→2LiX+(NH 4 ) 2 CO 3 (1) Li 2 CO 3 +2NH 4 X→2LiX+NH 4 HCO 3 +NH 3 (2) Li 2 CO 3 +2NH 4 X→2LiX+H 2 O+CO 2 +2NH 3 (3) (In formulas (1) to (3), X is a halogen atom.)

[0027] As is clear from the above reaction formulas (1) to (3), in the manufacturing method of the present embodiment, lithium halide is generated by the reaction of lithium carbonate and ammonium halide, and at the same time, water, carbon dioxide, and ammonia are generated as by-products. However, since carbon dioxide and ammonia are gases, they are easily removed. Also, regarding the water generated as a by-product, it is preferable to remove it by, for example, mixing lithium carbonate and ammonium halide under heating conditions.

[0028] [Mixing] In the manufacturing method of the present embodiment, it is necessary to mix the lithium carbonate and the ammonium halide. The temperature conditions for the above mixing are not particularly limited and may be carried out at room temperature. However, from the viewpoint of promoting the reaction between lithium carbonate and ammonium halide and removing the water generated as a by-product as described above, it is preferable to mix while heating. As the temperature conditions in the heat mixing, 90 °C or higher is preferable, 150 °C or higher is more preferable, 180 °C or higher is further preferable, 200 °C or higher is particularly preferable. Also, from the viewpoint of reducing the energy required for the production of lithium halide, 400 °C or lower is preferable, 350 °C or lower is more preferable, 300 °C or lower is further preferable, 280 °C or lower is particularly preferable. Therefore, specifically, 90 to 400 °C is preferable, 150 to 350 °C is more preferable, 180 to 300 °C is further preferable, 200 to 280 °C is particularly preferable.

[0029] The above mixing treatment can be carried out in the absence of a solvent or using a solvent to react lithium carbonate and ammonium halide. Also, the above mixing treatment is preferably carried out under an inert gas such as nitrogen or argon to effectively remove by-products such as ammonia, water, and carbon dioxide and promote the reaction. In the production method of this embodiment, the lithium halide produced may form a complex with ammonia generated as a by-product. However, by carrying out the above mixing treatment, it becomes possible to remove ammonia.

[0030] In the production method of this embodiment, by mixing the above lithium carbonate and ammonium halide, lithium halide is obtained by the reaction between lithium carbonate and ammonium halide, and by-products such as ammonia and carbon dioxide become gases and are removed. Therefore, the reverse reaction hardly occurs and the reaction is promoted. When mixing the above lithium carbonate, ammonium halide, and a solvent used as necessary, there is no particular limitation on the mixing method. It is only necessary to put lithium carbonate, ammonium halide, and a solvent used as necessary into a device capable of mixing them and mix while heating to the above predetermined temperature. When mixing the above lithium carbonate and ammonium halide in the absence of a solvent, for example, it can be mixed by a mechanical milling method in which a pulverizer such as a ball mill or a bead mill is used for the reaction. When mixing the above lithium carbonate and ammonium halide using a solvent, these raw materials may be charged into a large excess of the solvent and stirred, or a small amount of the solvent may be charged together with lithium carbonate and ammonium halide into a device or a pulverizer capable of mixing the above raw materials for mixing.

[0031] As a device for mixing lithium carbonate and ammonium halide with the addition of a small amount of a solvent as necessary, it may be appropriately selected according to the scale. For example, for a small scale, a device such as a Schlenk with a stir bar may be used, and for a medium to large scale, a mechanical stirring type mixer equipped with a stirring blade in the tank may be used. Examples of the mechanical stirring type mixer include a high-speed stirring type mixer and a double-arm type mixer. From the viewpoint of enhancing the uniformity of the raw material mixture, the high-speed stirring type mixer is preferably used. Examples of the high-speed stirring type mixer include a vertical axis rotation type mixer and a horizontal axis rotation type mixer, and either type of mixer may be used.

[0032] Examples of the shape of the stirring blade used in the above mechanical stirring type mixer include a blade type, an arm type, an anchor type, a paddle type, a full zone type, a ribbon type, a multi-stage blade type, a double-arm type, a shovel type, a two-axis blade type, a flat blade type, and a C-type blade type.

[0033] The mixing time of the above mixing treatment is usually about 0.1 to 500 hours. From the viewpoint of sufficiently advancing the reaction between lithium carbonate and ammonium halide, it is preferably 0.5 to 100 hours, more preferably 1.0 to 50 hours, and still more preferably 1.5 to 20 hours.

[0034] [Preliminary mixing] In the production method of the present embodiment, it is preferable from the viewpoint of promoting the reaction to perform the above heat mixing after preliminarily mixing lithium carbonate and ammonium halide. The mixing method and solvent used for preliminary mixing are the same as those used in the above mixing step.

[0035] [Solvent] As the solvent used in this embodiment, hydrocarbon solvents such as aliphatic hydrocarbon solvents, alicyclic hydrocarbon solvents, and aromatic hydrocarbon solvents; solvents containing carbon atoms and heteroatoms, etc., solvents containing carbon atoms are preferably mentioned. Examples of aliphatic hydrocarbon solvents include hexane, pentane, 2-ethylhexane, heptane, octane, decane, undecane, dodecane, tridecane, etc. Examples of alicyclic hydrocarbon solvents include cyclohexane, methylcyclohexane, etc. Examples of aromatic hydrocarbon solvents include benzene, toluene, xylene, mesitylene, ethylbenzene, tert-butylbenzene, chlorobenzene, trifluoromethylbenzene, nitrobenzene, etc. Examples of solvents containing carbon atoms and heteroatoms include carbon disulfide, diethyl ether, dibutyl ether, tetrahydrofuran, etc. Among these solvents, alicyclic hydrocarbon solvents or solvents containing carbon atoms and heteroatoms are preferred. Among alicyclic hydrocarbon solvents, cyclohexane is preferred. Among solvents containing carbon atoms and heteroatoms, solvents containing oxygen atoms are preferred, and tetrahydrofuran is more preferred. Among the above solvents, tetrahydrofuran is particularly preferred. Note that using water as the solvent is not preferred because it deteriorates the performance of the solid electrolyte.

[0036] The usage amount of the solvent is preferably such that the total usage amount of lithium carbonate and ammonium halide with respect to 1 liter of the solvent is 0.1 to 1 kg, more preferably 0.05 to 0.8 kg, and even more preferably 0.2 to 0.7 kg. When the usage amount of the solvent is within the above range, the raw materials can react more smoothly, and it can be easily removed when it is necessary to remove the solvent.

[0037] [Removal of Solvent] When a solvent is used in the production method of the present embodiment, lithium halide can be obtained by removing the solvent. When removing the solvent, methods such as solid-liquid separation such as filtration, decantation, and centrifugation can be adopted, or a method by drying can be adopted. These methods will be described later.

[0038] Filtration is a method adopted for removing the solvent existing as a liquid. For example, it can be carried out using a glass filter or the like. As the glass filter, for example, those having a pore size of about 10 to 200 μm, preferably 20 to 150 μm, may be used. When decantation is performed, it can be carried out by removing the solvent that becomes the supernatant after the solid has precipitated. Centrifugation can be carried out using a centrifuge.

[0039] Drying can be carried out by drying under reduced pressure, drying by heating, etc. For example, after drying under reduced pressure, drying by heating can also be carried out, or drying by heating under reduced pressure can also be carried out.

[0040] Drying under reduced pressure can be carried out using, for example, a vacuum pump or the like, and it is preferable to dry under reduced pressure from the viewpoint of shortening the drying time. When drying is carried out by heating, it can be carried out at a temperature corresponding to the type of the solvent. For example, it can be carried out at a temperature above the boiling point of these solvents. In this case, since it also depends on the degree of reduced pressure, it cannot be generally stated, but as the heating temperature, it is usually 30 to 140 °C, preferably 40 to 130 °C, more preferably 50 to 120 °C, and even more preferably 60 to 100 °C.

[0041] The lithium halide compound obtained by the production method of the present embodiment includes, as described above, a lithium halide complex in addition to lithium halide. The water content contained in the lithium halide obtained by the production method of the present embodiment is 1% by mass or less, more preferably 0.5% by mass or less, and 0.3% by mass or less. The lower limit is usually about 0.01% by mass. In this specification, the water content of the lithium halide compound is the value measured by the Karl Fischer moisture meter under the conditions of the vaporization method and 280 °C, similar to the water content in lithium carbonate.

[0042] <Method for Producing Sulfide Solid Electrolyte> The lithium halide obtained by the production method of the lithium halide of the present embodiment is preferably used as a raw material for the sulfide solid electrolyte as described above. The production method of the sulfide solid electrolyte of the present embodiment includes reacting the above lithium halide with a phosphorus compound, and preferably, is obtained by a production method including reacting the above lithium halide, a lithium compound other than lithium halide, and a phosphorus compound. The production method including reacting a lithium halide, a lithium compound other than lithium halide, and a phosphorus compound is a known method, and specific treatments, operations, etc. may be carried out according to known methods.

[0043] Examples of the lithium halide include lithium fluoride, lithium chloride, lithium bromide, lithium iodide, etc., and lithium bromide and lithium iodide are preferred. Examples of the lithium compound other than lithium halide include, for example, lithium sulfide (Li 2 S), lithium oxide (Li 2 O), lithium carbonate (Li 2 CO 3 ), etc., and among them, lithium sulfide is preferred from the viewpoint of ionic conductivity.

[0044] Examples of the phosphorus compound include, for example, phosphorus sulfides such as diphosphorus trisulfide (P 2 S 3 ), diphosphorus pentasulfide (P 2 S 5 ), sodium phosphate (Na 3 PO 4 ), lithium phosphate (Li 3PO 4 ) and the like, such as phosphate compounds, are preferably mentioned. Among them, phosphorus sulfide is preferable, and diphosphorus pentasulfide (P 2 S 5 ) is more preferable. Diphosphorus pentasulfide (P 2 S 5 ) and other phosphorus compounds can be used without particular limitation as long as they are industrially manufactured and sold. These phosphorus compounds can be used alone or in combination of multiple kinds.

[0045] In addition, as those containing halogen atoms other than lithium halide, halogen molecules, that is, fluorine (F 2 ), chlorine (Cl 2 ), bromine (Br 2 ), iodine (I 2 ), preferably chlorine (Cl 2 ), bromine (Br 2 ), iodine (I 2 ), more preferably bromine (Br 2 ), iodine (I 2 ) can also be used.

[0046] Among the above, a combination of lithium sulfide, diphosphorus pentasulfide and lithium halide, or a combination of lithium sulfide, diphosphorus pentasulfide, lithium halide and halogen molecule is preferable.

[0047] When using a combination of lithium sulfide, diphosphorus pentasulfide and lithium halide as raw materials, the ratio of lithium sulfide to the total of lithium sulfide and diphosphorus pentasulfide is preferably 70 to 80 mol%, more preferably 72 to 78 mol%, and still more preferably 74 to 78 mol% from the viewpoint of obtaining higher chemical stability and higher ionic conductivity. In addition, when using a combination of lithium bromide and lithium iodide as lithium halide, from the viewpoint of improving ionic 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%, still more preferably 40 to 80 mol%, and particularly preferably 50 to 70 mol%.

[0048] When using lithium sulfide, diphosphorus pentasulfide, a halogen element, and lithium halide, the content of the halogen element (α mol%) and the content of lithium halide (β mol%) with respect to the total amount of these are preferably such that the following formula (2) is satisfied, more preferably such that the following formula (3) is satisfied, still more preferably such that the following formula (4) is satisfied, and even more preferably such that the following formula (5) is satisfied. 2 ≦ 2α + β ≦ 100…(2) 4 ≦ 2α + β ≦ 80 …(3) 6 ≦ 2α + β ≦ 50 …(4) 6 ≦ 2α + β ≦ 30 …(5)

[0049] In reacting lithium halide, a lithium compound other than lithium halide, and a phosphorus compound, the reaction can be carried out by treating these raw materials by methods such as mixing, stirring, and pulverizing. For example, when performing the treatment of mixing and stirring, a mechanical stirring type mixer used in the mixing in the production method of the present embodiment may be used, and when performing the treatment of pulverizing, equipment generally referred to as a pulverizer, such as a medium type pulverizer such as a ball mill or a bead mill, may be used.

[0050] Also, when reacting the raw materials, a complexing agent or a solvent may be further added as necessary. In this case, a slurry containing an electrolyte precursor composed of the raw materials and the complexing agent and a liquid complexing agent and solvent is obtained, and by drying this, the liquid complexing agent and solvent are removed, and by further heating, a sulfide solid electrolyte is obtained. The above drying can be carried out by any of the methods capable of performing drying in the production method of the present embodiment. The temperature conditions and the like when performing drying by heating are the same as the conditions for drying by heating in the production method of the present embodiment because the solvent used is the same as the solvent used in the production method of the present embodiment. As the solvent used in the production method of the sulfide solid electrolyte of the present embodiment described above, the same solvents as those used in the production method of the lithium halide of the present embodiment described above are used.

[0051] [Complexing agent] The complexing agent is one that can coordinate (bond) with the lithium atoms, sulfur atoms, and halogen atoms contained in the above-mentioned lithium sulfide and lithium halide, especially with the lithium atoms, to form a complex. As the complexing agent, any one having such performance can be used without particular limitation. In particular, compounds containing heteroatoms such as nitrogen atoms, oxygen atoms, and chlorine atoms, which have a high affinity for lithium atoms, are preferred, and compounds having groups containing these heteroatoms are more preferred.

[0052] As the above-mentioned heteroatoms, nitrogen atoms and oxygen atoms are more preferred. As the group containing the above-mentioned nitrogen atom, an amino group, an amide group, a nitro group, and a nitrile group are preferred, and an amino group is more preferred. As the group containing the above-mentioned oxygen atom, an ester group and an ether group are preferred, and an ester group is more preferred.

[0053] Examples of the complexing agent having an amino group include amine compounds such as aliphatic amines, alicyclic amines, heterocyclic amines, and aromatic amines, which can be used alone or in combination of multiple types.

[0054] Examples of aliphatic amines include aliphatic primary diamines such as ethylenediamine, diaminopropane, and diaminobutane; aliphatic secondary diamines such as N,N'-dimethylethylenediamine, N,N'-diethylethylenediamine, N,N'-dimethyldiaminopropane, and N,N'-diethyldiaminopropane; aliphatic tertiary 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. Among these, aliphatic diamines are typically preferred. Here, in the examples in this specification, for example, in the case of diaminobutane, unless otherwise specified, all isomers including isomers regarding the positions of amino groups such as 1,2-diaminobutane, 1,3-diaminobutane, and 1,4-diaminobutane, as well as linear and branched isomers of butane, are included.

[0055] The number of carbon atoms of the aliphatic amine is preferably 2 or more, more preferably 4 or more, still more preferably 6 or more, and the upper limit is preferably 10 or less, more preferably 8 or less, still more preferably 7 or less. Also, the number of carbon atoms of 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, still more preferably 3 or less.

[0056] Examples of the alicyclic amine include alicyclic primary diamines such as cyclopropanediamine and cyclohexanediamine; alicyclic secondary diamines such as bis(aminomethyl)cyclohexane; alicyclic tertiary diamines such as N,N,N',N'-tetramethyl-cyclohexanediamine and bis(ethylmethylamino)cyclohexane; and the like. Among these, alicyclic diamines are typically preferred. Examples of the heterocyclic amine include heterocyclic primary diamines such as isophoronediamine; heterocyclic secondary diamines such as piperazine and dipiperidylpropane; heterocyclic tertiary diamines such as N,N-dimethylpiperazine and bis(methylpiperidyl)propane; and the like. Among these, heterocyclic diamines are typically preferred. The number of carbon atoms of the alicyclic amine and the heterocyclic amine is preferably 3 or more, more preferably 4 or more, and preferably 16 or less, more preferably 14 or less as the upper limit.

[0057] Examples of the aromatic amine include aromatic primary diamines such as phenylenediamine, tolylenediamine, and naphthalenediamine; aromatic secondary diamines such as N-methylphenylenediamine, N,N'-dimethylphenylenediamine, N,N'-bis(methylphenyl)phenylenediamine, 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 the like. Among these, aromatic diamines are typically preferred. The number of carbon atoms of the aromatic amine is preferably 6 or more, more preferably 7 or more, still more preferably 8 or more, and preferably 16 or less, more preferably 14 or less, still more preferably 12 or less as the upper limit.

[0058] The amine compound used in this embodiment may be substituted with substituents such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, and a cyano group, or a halogen atom. Although diamines have been exemplified as specific examples, it goes without saying that the amine compounds that can be used in the present embodiment are not limited to diamines. For example, aliphatic monoamines corresponding to various diamines such as trimethylamine, triethylamine, ethyldimethylamine, and the above-mentioned aliphatic diamines; also piperidine compounds such as piperidine, methylpiperidine, and tetramethylpiperidine; pyridine compounds such as pyridine and picoline; morpholine compounds such as morpholine, methylmorpholine, and thiomorpholine; imidazole compounds such as imidazole and methylimidazole; alicyclic monoamines such as alicyclic monoamines corresponding to the above-mentioned alicyclic diamines; heterocyclic monoamines corresponding to the above-mentioned heterocyclic diamines; in addition to monoamines such as aromatic monoamines corresponding to the above-mentioned aromatic diamines, for example, 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.

[0059] Among the above, it is preferably a tertiary amine having a tertiary amino group as the amino group, more preferably a tertiary diamine having two tertiary amino groups, still more preferably a tertiary diamine having two tertiary amino groups at both ends, and even more preferably an aliphatic tertiary diamine having tertiary amino groups at both ends. In the above amine compound, as the aliphatic tertiary diamine having tertiary amino groups at both ends, tetramethylethylenediamine, tetraethylethylenediamine, tetramethyldiaminopropane, and tetraethyldiaminopropane are preferable, and considering the ease of availability, etc., tetramethylethylenediamine (also referred to as "TMEDA") and tetramethyldiaminopropane (also referred to as "TMPDA") are preferable.

[0060] In addition, although not particularly exemplified, compounds having a group other than an amino group, such as an amide group, a nitro group, a nitrile group, etc., which contain a nitrogen atom as a hetero atom, also exhibit the same effects as the compounds containing an amino group.

[0061] Next, examples of the complexing agent having the above ether group include ether compounds such as aliphatic ethers, alicyclic ethers, heterocyclic ethers, aromatic ethers, etc., and they can be used alone or in combination of multiple types.

[0062] Examples of aliphatic ethers include monoethers such as dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, tert-butyl methyl ether, etc.; diethers such as dimethoxymethane, dimethoxyethane, diethoxymethane, diethoxyethane, etc.; polyethers having three or more ether groups such as diethylene glycol dimethyl ether (diglyme), triethylene oxide glycol dimethyl ether (triglyme), etc.; and ethers containing a hydroxyl group such as diethylene glycol, triethylene glycol, etc. The number of carbon atoms of the aliphatic ether is preferably 2 or more, more preferably 3 or more, still more preferably 4 or more, and the upper limit is preferably 10 or less, more preferably 8 or less, still more preferably 6 or less. In addition, the number of carbon atoms 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, still more preferably 3 or less.

[0063] Examples of alicyclic ethers include ethylene oxide, propylene oxide, tetrahydrofuran, tetrahydropyran, dimethoxytetrahydrofuran, cyclopentyl methyl ether, dioxane, dioxolane, etc., and examples of heterocyclic ethers include furan, benzofuran, benzopyran, dioxene, dioxine, morpholine, methoxyindole, hydroxymethyldimethoxypyridine, etc. The carbon number of the alicyclic ether and the heterocyclic ether is preferably 3 or more, more preferably 4 or more, and preferably 16 or less, more preferably 14 or less as the upper limit.

[0064] Examples of the aromatic ether include methyl phenyl ether (anisole), ethyl phenyl ether, dibenzyl ether, diphenyl ether, benzyl phenyl ether, naphthyl ether, and the like. The carbon number of the aromatic ether is preferably 7 or more, more preferably 8 or more, and preferably 16 or less, more preferably 14 or less, still more preferably 12 or less as the upper limit.

[0065] The ether compound used in this embodiment may be substituted with substituents such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, a cyano group, or a halogen atom.

[0066] The ether compound used in this embodiment is preferably an aliphatic ether, and more preferably dimethoxyethane or tetrahydrofuran.

[0067] Examples of the complexing agent having the ester group 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.

[0068] Examples of the aliphatic ester include formic acid esters such as methyl formate, ethyl formate, and triethyl formate; acetic acid esters 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. The number of carbon atoms in the aliphatic ester is preferably 2 or more, more preferably 3 or more, still more preferably 4 or more, and the upper limit is preferably 10 or less, more preferably 8 or less, still more preferably 7 or less. Also, 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, still more preferably 3 or less.

[0069] Examples of the alicyclic ester include methyl cyclohexanecarboxylate, ethyl cyclohexanecarboxylate, dimethyl cyclohexanedicarboxylate, dibutyl cyclohexanedicarboxylate, dibutyl cyclohexenedicarboxylate, etc. Examples of the heterocyclic ester include methyl pyridinecarboxylate, ethyl pyridinecarboxylate, propyl pyridinecarboxylate, methyl pyrimidinecarboxylate, ethyl pyrimidinecarboxylate, and lactones such as acetolactone, propiolactone, butyrolactone, valerolactone, etc. The number of carbon atoms in the alicyclic ester and the 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.

[0070] Examples of the aromatic ester include benzoic acid esters such as methyl benzoate, ethyl benzoate, propyl benzoate, butyl benzoate, etc.; phthalic acid esters such as dimethyl phthalate, diethyl phthalate, dibutyl phthalate, butyl benzyl phthalate, dicyclohexyl phthalate, etc.; trimellitic acid esters such as trimethyl trimellitate, triethyl trimellitate, tripropyl trimellitate, tributyl trimellitate, trioctyl trimellitate, etc. 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, still more preferably 12 or less.

[0071] The ester compound used in this embodiment may be substituted with substituents such as an alkyl group, an alkenyl group, an alkoxyl group, a hydroxyl group, a cyano group, etc., or a halogen element.

[0072] As the ester compound used in this embodiment, an aliphatic ester is preferable, an acetate ester is more preferable, and ethyl acetate is particularly preferable.

[0073] In the production method of this embodiment, the amount of the complexing agent used is preferably 100 mL or more, more preferably 200 mL or more, still more preferably 250 mL or more, even more preferably 300 mL or more, with respect to 1 kg of the total amount of lithium sulfide and lithium halide, and preferably 30000 mL or less, more preferably 25000 mL or less, still more preferably 20000 mL or less, even more preferably 10000 mL or less as the upper limit.

[0074] When a complexing agent is used in producing the sulfide solid electrolyte, it is preferably to include removing the complexing agent from the obtained complex (electrolyte precursor). By removing the complexing agent from the complex (electrolyte precursor), an amorphous sulfide solid electrolyte can be obtained. The removal of the complexing agent from the complex (electrolyte precursor) can be performed, for example, by heating.

[0075] The sulfide solid electrolyte obtained by the production method of this embodiment contains lithium element, sulfur element, phosphorus element and halogen element, and is basically an amorphous sulfide solid electrolyte. In this specification, the amorphous sulfide solid electrolyte means a halo pattern in which peaks other than the peaks derived from the material are not substantially observed in the X-ray diffraction pattern in X-ray diffraction measurement, regardless of the presence or absence of the peaks derived from the raw materials of the solid electrolyte. Typical examples of the amorphous sulfide solid electrolyte obtained using the lithium halide compound obtained by the production method of this embodiment include, for example, Li 2 S-P 2 S 5 -LiI, Li 2 S-P 2 S 5 -LiCl, Li 2 S-P 2 S 5 -LiBr, Li 2 S-P2 S 5 - Solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as LiI and LiBr; further containing other elements such as oxygen and silicon, for example, Li 2 S - P 2 S 5 - Li 2 O - LiI, Li 2 S - SiS 2 - P 2 S 5 - Solid electrolytes such as LiI are preferred. From the perspective of obtaining higher ionic conductivity, Li 2 S - P 2 S 5 - LiI, Li 2 S - P 2 S 5 - LiCl, Li 2 S - P 2 S 5 - LiBr, Li 2 S - P 2 S 5 - Solid electrolytes composed of lithium sulfide, phosphorus sulfide, and lithium halide, such as LiI - LiBr, are preferred. The types of elements constituting the amorphous solid electrolyte can be confirmed, for example, by an ICP emission spectroscopic analyzer.

[0076] In the amorphous sulfide solid electrolyte obtained by the production method of the present embodiment, the mixing ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms is preferably 1.0 to 1.8:1.0 to 2.0:0.1 to 0.8:0.01 to 0.6, more preferably 1.1 to 1.7:1.2 to 1.8:0.2 to 0.6:0.05 to 0.5, and even more preferably 1.2 to 1.6:1.3 to 1.7:0.25 to 0.5:0.08 to 0.4. Further, when bromine and iodine are used in combination as halogen atoms, the mixing ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, bromine, and iodine is preferably 1.0 to 1.8:1.0 to 2.0:0.1 to 0.8:0.01 to 0.3:0.01 to 0.3, more preferably 1.1 to 1.7:1.2 to 1.8:0.2 to 0.6:0.02 to 0.25:0.02 to 0.25, even more preferably 1.2 to 1.6:1.3 to 1.7:0.25 to 0.5:0.03 to 0.2:0.03 to 0.2, and even more preferably 1.35 to 1.45:1.4 to 1.7:0.3 to 0.45:0.04 to 0.18:0.04 to 0.18. By setting the mixing ratio (molar ratio) of lithium atoms, sulfur atoms, phosphorus atoms, and halogen atoms within the above ranges, it becomes easier to obtain a solid electrolyte having a higher ionic conductivity, such as a thiolysicon region II-type crystal structure and an argyrodite-type crystal structure, which will be described later.

[0077] Further, the above amorphous sulfide solid electrolyte can be converted into a crystalline sulfide solid electrolyte by further heating. In this specification, a crystalline solid electrolyte is a solid electrolyte in which peaks derived from the solid electrolyte are observed in the X-ray diffraction pattern in X-ray diffraction measurement, regardless of the presence or absence of peaks derived from the raw materials of the solid electrolyte in these. That is, the crystalline solid electrolyte may include a crystal structure derived from the solid electrolyte, and even if a part of it is a crystal structure derived from the solid electrolyte, or all of it is a crystal structure derived from the solid electrolyte. And as long as the crystalline solid electrolyte has the above X-ray diffraction pattern, it may contain an amorphous solid electrolyte in a part thereof. Therefore, the crystalline solid electrolyte includes so-called glass ceramics obtained by heating an amorphous solid electrolyte above the crystallization temperature.

[0078] The heating temperature cannot be generally stated as it can be appropriately selected according to the structure of the amorphous sulfide solid electrolyte. For example, using a differential thermal analyzer (DTA apparatus), differential thermal analysis (DTA) is performed under a temperature rising condition of 10 °C / min. Starting from the temperature at the peak top of the exothermic peak observed at the lowest temperature side, it is preferably in the range of 5 °C or more, more preferably 10 °C or more, still more preferably 20 °C or more. There is no particular limitation on the upper limit, but it may be about 40 °C or less. Specifically, usually, 130 °C or more is preferable, 135 °C or more is more preferable, 140 °C or more is still more preferable. There is no particular limitation on the upper limit, but it is preferably 300 °C or less, more preferably 280 °C or less, still more preferably 250 °C or less.

[0079] The heating time is not particularly limited as long as it is a time sufficient to obtain the desired crystalline sulfide solid electrolyte. However, 1 minute or more is preferable, 10 minutes or more is more preferable, 30 minutes or more is still more preferable, and 1 hour or more is even more preferable. Also, the upper limit of the heating time is not particularly limited, but 24 hours or less is preferable, 10 hours or less is more preferable, 5 hours or less is still more preferable, and 3 hours or less is even more preferable.

[0080] Also, the heating is preferably carried out in an inert gas atmosphere (for example, nitrogen atmosphere, argon atmosphere) or a reduced pressure atmosphere (especially in a vacuum) because it can prevent the deterioration (for example, oxidation) of the crystalline solid electrolyte. The heating method is not particularly limited, and examples include methods using a hot plate, a vacuum heating device, an argon gas atmosphere furnace, a firing furnace, etc. Industrially, a horizontal dryer having a heating means and a feeding mechanism, a horizontal vibration fluidized dryer, etc. can also be used, and it can be selected according to the processing amount to be heated.

[0081] As the crystalline sulfide solid electrolyte obtained using the lithium halide compound obtained by the production method of this embodiment, Li 3 PS 4 crystal structure, Li 4 P 2 S 6 crystal structure, Li 7PS 6 Crystal structure, Li 7 P 3 S 11 Examples of the crystal structure include a sulfide solid electrolyte having a crystal structure having peaks in the vicinity of 2θ = 20.2° and 23.6° (for example, the crystal structure described in JP-A-2013-16423).

[0082] Also, Li 4-x Ge 1-x P x S 4 A thio-LISICON Region II type crystal structure (see Kanno et al., Journal of The Electrochemical Society, 148(7) A742-746(2001)), a crystal structure similar to the thio-LISICON Region II type (see Solid State Ionics, 177(2006), 2721-2725), etc. From the viewpoint of ionic conductivity, a thio-LISICON Region II type crystal structure is preferable. Here, the "thio-LISICON Region II type crystal structure" means any of a thio-LISICON Region II type crystal structure of the Li 4-x Ge 1-x P x S 4 system and a crystal structure similar to the thio-LISICON Region II type. 4-x Ge 1-x P x S 4 system thio-LISICON Region II (thio-LISICON Region II) type crystal structure, Li 4-x Ge 1-x P x S 4 It means that it is either a thio-LISICON Region II type crystal structure or a crystal structure similar to the thio-LISICON Region II type of the Li Here, the above "Li 4-x Ge 1-x P x S 4The notation of the crystal structure as "thio-LISICON Region II type" means that, at the time it was found in the above-mentioned literature, it was a crystal structure composed of the atoms Li, Ge, P, and S atoms. That the sulfide solid electrolyte obtained by the manufacturing method of the present embodiment has a thio-LISICON Region II type crystal structure means that a crystal structure that exhibits the same diffraction peaks as those of the "Li 4-x Ge 1-x P x S 4 system thio-LISICON Region II type" crystal structure (including the above similar crystal structures) is formed by each atom (Li, P, S, and halogen atom) contained in the raw material inclusion. The same applies to the all-dyedite type crystal structure described later.

[0083] Also, as the composition ratio of the atoms contained in the crystalline sulfide solid electrolyte, it is preferably a composition ratio according to the composition formula corresponding to the above various crystal structures and within the range of the composition ratio of each atom of the above amorphous sulfide solid electrolyte. When it is within the range of the composition ratio of each atom, among the above crystal structures, it becomes easier to form a thiosilicon Region II type crystal structure or an all-dyedite type crystal structure.

[0084] The sulfide solid electrolyte thus obtained is obtained using a lithium halide compound that contains almost no moisture or hydrate as a raw material, so it has high ionic conductivity and excellent battery performance. Therefore, the sulfide solid electrolyte obtained using the lithium halide compound obtained by the manufacturing method of the present embodiment can be used for any application that requires Li ion conductivity, and is particularly preferably used for a battery. The sulfide solid electrolyte may be used for the positive electrode layer, the negative electrode layer, or the electrolyte layer. Each layer can be manufactured by a known method. In addition to the positive electrode layer, the electrolyte layer, and the negative electrode layer, it is preferable to use a current collector for the battery, and a known current collector can be used. For example, a layer coated with Au or the like that reacts with the sulfide solid electrolyte, such as Au, Pt, Al, Ti, or Cu, can be used.

Example

[0085] Next, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples.

[0086] (Example 1) In a mortar, 0.274 g (3.7 mmol) of lithium carbonate (Li 2 CO 3 ) and 0.726 g (7.4 mmol) of ammonium bromide (NH 4 Br) were weighed and mixed, and it was visually confirmed that they were not deliquescent. Next, the obtained mixture was placed in a Schlenk flask (volume: 100 mL) with a stir bar, and while heating at 250 °C under vacuum, mixing with the stir bar was continued for 2 hours to obtain a white powder. For the obtained powder, powder X-ray diffraction (XRD) measurement was performed by the following method. The results are shown in FIG. 1. Also, by the same method, XRD measurements were performed on lithium carbonate and ammonium bromide used as raw materials. As a result, strong peaks due to lithium carbonate appeared near 2θ = 21.4°, 30.7°, and 31.8°, strong peaks due to ammonium bromide appeared near 2θ = 21.9° and 31.2°, and strong peaks due to lithium bromide appeared near 2θ = 28.3°, 32.7°, 46.9°, and 55.6°. As shown in FIG. 1, it was confirmed that for the powder obtained in Example 1, the peak due to lithium bromide was the strongest, and although the peaks due to the raw materials lithium carbonate and ammonium bromide remained somewhat, most of them had disappeared.

[0087] In this specification, powder X-ray diffraction (XRD) measurement was performed as follows. The sample powder was filled into a groove with a diameter of 20 mm and a depth of 0.2 mm, and leveled with glass to obtain a sample. This sample was sealed with a Kapton film for XRD and measured under the following conditions without exposure to air. Measuring device: D2 PHASER, manufactured by Bruker Corporation Tube voltage: 30 kV Tube current: 10 mA X-ray wavelength: Cu-Kα ray (1.5418 Å) Optical system: focusing method Slit configuration: solar slit 4°, divergence slit 1 mm, using a Kβ filter (Ni plate) Detector: semiconductor detector Measurement range: 2θ = 10 - 60 deg Step width, scan speed: 0.05 deg, 0.05 deg / second

[0088] (Comparative Example 1) When 0.300 g (7.1 mmol) of lithium hydroxide monohydrate (LiOH·H 2 O) and 0.700 g (7.1 mmol) of ammonium bromide (NH 4 Br) were weighed and mixed, it was visually in a state of deliquescence. Even if this was recovered and vacuum dried, it adhered to the wall surface of the container, and it was clear that powdery lithium halide could not be obtained.

Industrial Applicability

[0089] According to the production method of the present invention, it does not involve a step of directly removing moisture, does not use elemental halogens that are troublesome to handle, and further does not cause excessive energy required for production. The obtained lithium halide compound can be suitably used as a raw material for sulfide solid electrolytes because of its low moisture content.

Claims

1. A method for producing lithium halide, comprising mixing lithium carbonate and ammonium halide.

2. The method for producing lithium halide according to Claim 1, wherein the mixing ratio of the lithium carbonate and the ammonium halide is in the range of 1.50 to 2.50 moles of ammonium halide per 1 mole of lithium carbonate.

3. The method for producing lithium halide according to Claim 1 or 2, wherein the lithium carbonate and the ammonium halide are preliminarily mixed and then further mixed by heating.

4. The method for producing lithium halide according to Claim 3, wherein the temperature condition for the heating and mixing is 90 to 400 °C.

5. The method for producing lithium halide according to Claim 3 or 4, wherein the heating and mixing is carried out under reduced pressure or in an inert gas atmosphere.

6. A method for producing a sulfide solid electrolyte, comprising reacting lithium halide obtained by the production method according to any one of Claims 1 to 5 with a phosphorus compound.

7. The method for producing a sulfide solid electrolyte according to Claim 6, further reacting a lithium compound other than lithium halide.

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