WO2016204255A1 - 固体電解質の製造方法 - Google Patents
固体電解質の製造方法 Download PDFInfo
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- WO2016204255A1 WO2016204255A1 PCT/JP2016/068011 JP2016068011W WO2016204255A1 WO 2016204255 A1 WO2016204255 A1 WO 2016204255A1 JP 2016068011 W JP2016068011 W JP 2016068011W WO 2016204255 A1 WO2016204255 A1 WO 2016204255A1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/14—Sulfur, selenium, or tellurium compounds of phosphorus
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B17/00—Sulfur; Compounds thereof
- C01B17/22—Alkali metal sulfides or polysulfides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D15/00—Lithium compounds
- C01D15/04—Halides
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
- H01M10/0562—Solid materials
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M6/00—Primary cells; Manufacture thereof
- H01M6/14—Cells with non-aqueous electrolyte
- H01M6/18—Cells with non-aqueous electrolyte with solid electrolyte
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a method for producing a solid electrolyte.
- an amorphous solid electrolyte or a crystalline solid electrolyte is known, and is appropriately selected according to the use and desired performance.
- a raw material is reacted by a mechanical milling method, a slurry method, a melt quenching method or the like to obtain an amorphous solid electrolyte, followed by a heat treatment to produce the raw material.
- a method of manufacturing by reacting at a high temperature around 200 ° C. by a mechanical milling method has been adopted (for example, Patent Document 1).
- a raw material is mechanically milled at 60 ° C.
- Comparative Examples 2 and 3 of Patent Document 1 disclose that a crystalline solid electrolyte can be obtained by subjecting a raw material to mechanical milling at a high temperature of 170 ° C. and 200 ° C.
- FIG. 2 is an X-ray analysis spectrum of the crystalline solid electrolyte obtained in Example 1.
- FIG. 3 is an X-ray analysis spectrum of a crystalline solid electrolyte obtained in Example 2.
- the present invention has been made in view of such a situation, and an object thereof is to provide a method for producing a crystalline solid electrolyte excellent in productivity and a multi-axis kneader.
- a method for producing a solid electrolyte comprising using a multi-axis kneader to react two or more kinds of solid raw materials to obtain a crystalline solid electrolyte.
- a crystalline solid electrolyte containing lithium element, phosphorus element, and sulfur element is obtained by reacting two or more solid raw materials containing lithium sulfide and diphosphorus pentasulfide using a multi-axis kneader.
- a method for producing a solid electrolyte is obtained by reacting two or more solid raw materials containing lithium sulfide and diphosphorus pentasulfide using a multi-axis kneader.
- a method for producing a solid electrolyte comprising obtaining a crystalline solid electrolyte containing an element and at least one of a bromine element and an iodine element.
- a crystalline solid electrolyte can be provided with excellent productivity.
- the method for producing a solid electrolyte of the present invention is characterized in that a crystalline solid electrolyte is obtained by reacting two or more kinds of solid raw materials using a multi-axis kneader.
- the crystalline solid electrolyte is a solid electrolyte in which a peak derived from the solid electrolyte is observed in the X-ray diffraction pattern in the X-ray diffraction measurement, and it does not matter whether there is a peak derived from the solid electrolyte raw material. Material.
- the crystalline solid electrolyte includes a crystal structure derived from the solid electrolyte, and even if a part thereof is a crystal structure derived from the solid electrolyte, the whole is a crystal structure derived from the solid electrolyte. It is also good. As long as the crystalline solid electrolyte has the X-ray diffraction pattern as described above, an amorphous solid electrolyte may be included in a part thereof.
- the above-mentioned amorphous solid electrolyte is a halo pattern in which the X-ray diffraction pattern is a halo pattern in which no peaks other than the material-derived peak are substantially observed in the X-ray diffraction measurement. The presence or absence is not questioned.
- the solid raw material used in the production method of the present invention can be used without particular limitation as long as it generally contains an element constituting a crystalline solid electrolyte.
- the conductive species exhibiting ionic conductivity is at least selected from alkali metals such as lithium, sodium, potassium, rubidium, cesium and francium, and alkaline earth metals such as beryllium, magnesium, calcium, strontium, barium and radium.
- alkali metals such as lithium, sodium, potassium, rubidium, cesium, and francium, and beryllium are more preferable, and lithium is particularly preferable.
- a solid material containing at least one element selected from alkali metals such as lithium, sodium, potassium, rubidium, cesium, and francium, and alkaline earth metals such as beryllium, magnesium, calcium, strontium, barium, and radium is preferable.
- a solid raw material containing at least one element selected from alkali metals such as lithium, sodium, potassium, rubidium, cesium, and francium and beryllium is more preferable, and a solid raw material containing lithium element is particularly preferable.
- the elements contained in the solid raw material other than the elements of the above-described conductive species may be appropriately selected according to the type of elements constituting the desired solid electrolyte.
- the crystalline solid electrolyte include an oxide solid electrolyte, a sulfide solid electrolyte, and the like, as will be described later, and a sulfide solid electrolyte is preferable in view of increasing the output of the battery.
- the solid material contains lithium element, phosphorus element, and sulfur element. By using such a solid material, a solid electrolyte containing a lithium element, a phosphorus element, and a sulfur element corresponding to the elements contained in the solid material can be obtained.
- the solid material containing lithium element is at least one of lithium compounds such as lithium sulfide (Li 2 S), lithium oxide (Li 2 O), lithium carbonate (Li 2 CO 3 ), and lithium metal alone.
- lithium sulfide (Li 2 S) is particularly preferable as the lithium compound.
- Lithium sulfide can be used without particular limitation, but high purity is preferred. Lithium sulfide can be produced, for example, by the methods described in JP-A-7-330312, JP-A-9-283156, JP-A-2010-163356, and JP-A-2011-84438. Specifically, lithium hydroxide and hydrogen sulfide are reacted at 70 to 300 ° C. in a hydrocarbon-based organic solvent to produce lithium hydrosulfide, and then the reaction solution is dehydrosulfurized to form lithium sulfide. Can be synthesized (Japanese Patent Laid-Open No. 2010-163356).
- lithium sulfide can be synthesized by reacting lithium hydroxide and hydrogen sulfide in an aqueous solvent at 10 to 100 ° C. to produce lithium hydrosulfide, and then dehydrosulfurizing the reaction solution (Japanese Patent Laid-Open No. 2005-133867). 2011-84438).
- lithium sulfide can be synthesized by reacting lithium hydroxide and hydrogen sulfide in the absence of a solvent.
- the reaction temperature is, for example, 20 to 300 ° C., 100 to 250 ° C., 120 to 240 ° C.
- Examples of the solid material containing phosphorus element include phosphorus sulfide such as diphosphorus trisulfide (P 2 S 3 ) and diphosphorus pentasulfide (P 2 S 5 ), silicon sulfide (SiS 2 ), and germanium sulfide (GeS 2 ).
- phosphorus sulfide such as diphosphorus trisulfide (P 2 S 3 ) and diphosphorus pentasulfide (P 2 S 5 ), silicon sulfide (SiS 2 ), and germanium sulfide (GeS 2 ).
- phosphorus compound phosphorus sulfide is preferable, and phosphorus pentasulfide (P 2 S 5 ) is more preferable.
- Phosphorus compounds such as diphosphorus pentasulfide (P 2 S 5 ) and simple phosphorus can be used without particular limitation as long as they are industrially produced and sold.
- the solid material containing lithium element, phosphorus element, and sulfur element preferably contains at least one of a lithium compound and a lithium metal simple substance and at least one of a phosphorus compound and a phosphorus simple substance.
- a combination of a lithium compound and a phosphorus compound is preferable, a combination of a lithium compound and phosphorus sulfide is more preferable, a combination of lithium sulfide and phosphorus sulfide is more preferable, and a combination of lithium sulfide and phosphorus pentasulfide is particularly preferable.
- the amount of the solid raw material containing lithium element and the solid raw material containing phosphorus element is not particularly limited, and may be appropriately determined based on a desired crystalline solid electrolyte.
- Li 2 S lithium sulfide
- P 2 S 5 diphosphorus pentasulfide
- the proportion of Li 2 S with respect to the total is preferably in the range of 68 to 82 mol% from the viewpoint of obtaining a crystalline solid electrolyte with high chemical stability by adopting a composition near the ortho composition described later, and is 70 to 80 mol. % Is more preferable, within the range of 72 to 78 mol% is further preferable, and within the range of 74 to 76 mol% is particularly preferable.
- the solid raw material preferably further contains at least one halogen element such as fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Chlorine (Cl), bromine (Br) And at least one of iodine (I) is preferable, and at least one of bromine (Br) and iodine (I) is more preferable.
- halogen element such as fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).
- Chlorine (Cl), bromine (Br) And at least one of iodine (I) is preferable, and at least one of bromine (Br) and iodine (I) is more preferable.
- a halogen-containing compound represented by the following general formula (1).
- M is sodium (Na), lithium (Li), boron (B), aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), germanium (Ge), Arsenic (As), Selenium (Se), Tin (Sn), Antimony (Sb), Tellurium (Te), Lead (Pb), Bismuth (Bi), or a combination of these elements with oxygen and sulfur elements Lithium (Li) or phosphorus (P) is preferable, and lithium (Li) is particularly preferable.
- X is a halogen element selected from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I).
- L is an integer of 1 or 2
- m is an integer of 1 to 10.
- Xs may be the same or different.
- m is 4, and X is composed of different elements such as Br and Cl.
- halogen-containing compound represented by the general formula (1) include sodium halides such as NaI, NaF, NaCl, and NaBr, lithium halides such as LiF, LiCl, LiBr, and LiI, BCl 3 , Boron halides such as BBr 3 and BI 3 , aluminum halides such as AlF 3 , AlBr 3 , AlI 3 and AlCl 3 , SiF 4 , SiCl 4 , SiCl 3 , Si 2 Cl 6 , SiBr 4 , SiBrCl 3 , SiBr 2 Cl 2, SiI 4 and halogenated silicon, PF 3, PF 5, PCl 3, PCl 5, POCl 3, PBr 3, POBr 3, PI 3, P 2 Cl 4, phosphorus halides such as P 2 I 4, SF 2 , SF 4 , SF 6 , S 2 F 10 , SCl 2 , S 2 Cl 2 , S 2 Br 2, etc.
- sodium halides such as NaI, NaF, NaC
- halogen-containing compounds examples include lithium halides such as lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), phosphorus pentachloride (PCl 5 ), phosphorus trichloride (PCl 3 ), five Phosphorus halides such as phosphorus bromide (PBr 5 ) and phosphorus tribromide (PBr 3 ) are preferred.
- lithium halides such as lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI)
- phosphorus pentachloride PCl 5
- phosphorus trichloride PCl 3
- five Phosphorus halides such as phosphorus bromide (PBr 5 ) and phosphorus tribromide (PBr 3 ) are preferred.
- lithium halides such as lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI), and phosphorus tribromide (PBr 3 ) are preferable, and lithium chloride (LiCl) and lithium bromide (LiBr) are preferable.
- lithium iodide (LiI) are more preferable, and lithium bromide (LiBr) and lithium iodide (LiI) are particularly preferable.
- the halogen-containing compound one of the above compounds may be used alone, or two or more thereof may be used in combination, that is, at least one of the above compounds can be used.
- lithium bromide (LiBr) and lithium iodide (LiI) are used as the halogen-containing compound
- lithium bromide (LiBr) and lithium iodide (LiI) in a solid raw material used for producing a crystalline solid electrolyte are used.
- the total use ratio is not particularly limited as long as the desired crystalline solid electrolyte can be obtained.
- the total use ratio is preferably in the range of 3 to 40 mol%, and preferably 3 to 35 mol%. It is more preferably within the range, and further preferably within the range of 3 to 30 mol%.
- the ratio (LiBr / (LiI + LiBr)) of lithium bromide (LiBr) to the total of lithium bromide (LiBr) and lithium iodide (LiI) is not particularly limited, and any ratio is adopted.
- a crystalline solid electrolyte crystalline solid electrolyte as a comparison target
- lithium bromide (LiBr) is replaced with lithium iodide (LiI).
- the ratio is such that a Li ion conductivity equal to or higher than that can be obtained, and more preferable that the Li ion conductivity be higher than that of a crystalline solid electrolyte as a comparison target.
- the proportion of lithium bromide (LiBr) is, for example, in the range of 1 to 99 mol%, and preferably in the range of 5 to 75 mol%.
- the range of 20 mol% or more and 75 mol% or less, 40 mol% or more and 72 mol% or less, and 50 mol% or more and 70 mol% or less is mentioned.
- the proportion of lithium iodide (LiI) in the total material used for the production of the crystalline solid electrolyte is more than 3 mol% and less than 20 mol%, and the proportion of lithium bromide (LiBr) in the total material is 3 to 20 mol%. % Or less is preferable.
- the crystalline solid electrolyte has a composition of a ((1-b) LiI ⁇ bLiBr) ⁇ (1-a) (cLi 2 S ⁇ (1-c) P 2 S 5 ), This corresponds to the total ratio of LiI and LiBr, b corresponds to the ratio of LiBr, and c corresponds to the ratio of Li 2 S.
- the particle size of the solid raw material is not particularly limited as long as it is a particle size normally possessed by each of the above raw materials.
- the particle size of lithium sulfide is 0.01 to 3 mm
- the particle size of diphosphorus pentasulfide is 0.01 to 3 mm.
- the particle size of lithium bromide is 0.01 to 3 mm
- the particle size of lithium iodide is 0.01 to 3 mm.
- the particle diameter of the solid raw material that can be used in the present invention is wide, and a multi-axis kneader can produce a solid electrolyte regardless of the particle diameter of the solid raw material.
- the average particle diameter is a value measured using a laser diffraction particle size distribution measuring apparatus (for example, Mastersizer 2000 manufactured by Malvern Instruments Ltd.).
- the above-mentioned solid raw material may be used as it is, or may be used in the form of a slurry with an organic solvent.
- organic solvent examples include organic solvents having a boiling point of 200 ° C. or higher.
- organic solvents examples include 1,2-butanediol, 1,3-butanediol, 1,2-pentanediol, 1,3-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,3-pentanediol, 2,4-pentanediol, 1,2-hexanediol, 1,3-hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, or Examples thereof include dihydric alcohols such as derivatives thereof. In the present invention, these organic solvents may be used alone or in combination of two or more.
- the amount used is preferably such that the total amount of solid raw material added to 1 liter of the organic solvent is 0.001 to 1 kg, more preferably 0.005 to 0.5 kg, 0.01 to 0.3 kg is more preferable.
- the amount of organic solvent used is preferably as small as possible.
- Multi-axis kneader As the multi-axis kneader used in the production method of the present invention, for example, two or more casings, which are arranged so as to penetrate the casing in the longitudinal direction, and are provided with paddles (screw blades) along the axial direction.
- the other configuration is not particularly limited as long as it has a solid material supply port at one end in the longitudinal direction of the casing and a discharge port at the other end.
- FIG. 1 is a plan view broken at the center of the rotating shaft of the kneader
- FIG. 2 is a plan view broken perpendicular to the rotating shaft of a portion where the paddle of the rotating shaft is provided.
- the multi-axis kneader shown in FIG. 1 includes a casing 1 having a supply port 2 at one end and a discharge port 3 at the other end, and two rotating shafts 4 a and 4 b so as to penetrate in the longitudinal direction of the casing 1. It is a shaft kneader.
- Paddles 5a and 5b are provided on the rotary shafts 4a and 4b, respectively.
- the solid raw material enters the casing 1 from the supply port 2 and is reacted by applying shear stress in the paddles 5 a and 5 b, and the crystallized reactant, that is, the crystalline solid electrolyte is discharged from the discharge port 3.
- the rotation shafts 4 may be parallel axes that are parallel to each other, may be of an oblique type, and the rotation directions of the rotation shafts may be the same or different directions.
- the rotational direction may be selected in order to obtain a more kneading effect, and the self-cleaning effect that sweeps solid raw materials and reactants in the casing and suppresses staying in these casings is emphasized. When doing so, the same direction may be selected.
- Paddle 5 (5a, 5b) is provided on the rotating shaft to knead the solid raw material, and is also referred to as a screw blade.
- a screw blade There are no particular restrictions on the cross-sectional shape, and as shown in FIG. 2, in addition to the substantially triangular shape in which each side of the regular triangle is a convex arc, the circular shape, the elliptical shape, the substantially rectangular shape, etc. Based on the shape, a shape having a notch in part may be used.
- each paddle may be provided on the rotation shaft at a different angle.
- the paddle may be a meshing type or a non-meshing type, and the meshing type may be selected in order to obtain a more kneading effect.
- the multi-screw kneader may be provided with a screw 6 (6a, 6b) on the supply port 2 side as shown in FIG.
- a reverse screw 7 (7a, 7b) may be provided on the outlet 3 side as shown in FIG.
- a commercially available kneader can also be used as the multiaxial kneader.
- Examples of commercially available multi-screw kneaders include KRC kneader, KRC Junior (manufactured by Kurimoto Steel Works), and the like, and can be appropriately selected according to the type of solid raw material and the desired scale.
- KRC kneader KRC Junior (manufactured by Kurimoto Steel Works), and the like
- a heat treatment is generally performed. I came. These methods cannot be said to be excellent in productivity because they require special equipment or use a hydrocarbon-based organic solvent.
- a general-purpose machine such as a multi-screw kneader, productivity superior to these production methods can be obtained.
- the temperature at the time of reaction of a solid raw material is more than the crystallization temperature of the crystal structure which the crystalline solid electrolyte obtained by reaction of a solid raw material has.
- the crystallization temperature in the present invention is the crystallization temperature of the crystalline structure of the crystalline solid electrolyte, that is, the amorphous solid electrolyte obtained using the solid raw material necessary for obtaining the crystalline solid electrolyte.
- DTA differential thermal analysis
- the crystallization temperature varies depending on the type, composition ratio, difference in structure, etc. of the elements constituting the obtained crystalline solid electrolyte.
- the crystal structure of the Li 2 SP—S 2 S 5 crystalline solid electrolyte the crystallization temperature is, for example, 210 ⁇ 340 ° C.
- Li 2 S-P 2 S 5 crystallization temperature of the crystalline structure crystalline solid electrolyte has a -LiBr system, for example 170 ⁇ 290 °C, Li 2 S -P 2 S
- the crystallization temperature of the crystal structure of the 5- LiI-based crystalline solid electrolyte is, for example, 140 to 260 ° C., and the crystal structure of the crystal structure of the Li 2 SP—S 2 S 5 —LiI-LiBr-based crystalline solid electrolyte
- the conversion temperature is, for example, in the range of 140 to 260 ° C.
- the temperature at the time of reaction when trying to obtain these crystalline solid electrolytes may be equal to or higher than the crystallization temperature of the crystal structure of each solid electrolyte.
- the temperature during the reaction is preferably equal to or higher than the crystallization temperature from the viewpoint of obtaining a crystalline solid electrolyte, and the specific temperature is the kind of element, the composition of the crystallization temperature as described above.
- the specific temperature is the kind of element, the composition of the crystallization temperature as described above.
- it is preferably 120 to 350 ° C., more preferably 130 to 320 ° C., further preferably 140 to 280 ° C., and particularly preferably 150 to 250 ° C. preferable.
- a method for adjusting the temperature during the reaction of the solid raw material a method usually used in a multi-screw kneader can be employed.
- a method of adjusting the supply amount of the solid raw material a method of adjusting power, a method of adjusting the rotational speed, a method of cooling, and the like can be mentioned.
- the temperature tends to increase.
- the temperature tends to increase.
- the rotational speed generally, when the rotational speed is increased, the temperature tends to increase.
- the number of rotations of the rotating shaft of the multi-axis kneader cannot be generally specified because it varies depending on the type, composition ratio, structural difference, etc. of the element constituting the obtained crystalline solid electrolyte, but is preferably 40 to 300 rpm, 40 to 250 rpm is more preferable, and 40 to 200 rpm is more preferable.
- a container for reacting raw materials such as a casing of a multi-axis kneader may be heated using a jacket heater (hot water type, electric type) or the like as necessary.
- the supply of the solid raw material, the reaction, and the discharge of the reactant are preferably performed in an inert gas atmosphere.
- the inert gas include nitrogen and argon.
- the reaction of the solid raw material is preferably performed in a dry atmosphere.
- the reaction is preferably performed in an atmosphere with a dew point of ⁇ 90 ° C. or higher and ⁇ 40 ° C. or lower, and is performed in an atmosphere with a dew point of ⁇ 90 ° C. or higher and ⁇ 45 ° C. or lower.
- the reaction time of the solid raw material varies depending on the kind of element constituting the crystalline solid electrolyte to be obtained, the composition ratio, the difference in structure, and the temperature at the time of reaction, and may be appropriately adjusted, and preferably 5 minutes to 50 minutes
- the time is more preferably 10 minutes to 15 hours, still more preferably 1 to 12 hours.
- the reaction product coming out from the discharge port may be supplied again from the supply port according to the degree of progress of the reaction, and the reaction may be further advanced.
- the degree of progress of the reaction can be grasped by the increase or decrease of the peak derived from the solid electrolyte raw material, and it can be considered that the reaction has sufficiently progressed when the peak becomes difficult to detect.
- heat treatment may be performed from the viewpoint of further improving the crystallinity of the crystalline solid electrolyte obtained as described above. That is, the production method of the present invention may further include heat-treating the crystalline solid electrolyte.
- the heat treatment temperature is increased by 10 ° C./min using a differential thermal analyzer (DTA apparatus) for an amorphous solid electrolyte obtained using a solid raw material necessary for obtaining a desired crystalline solid electrolyte.
- DTA apparatus differential thermal analyzer
- DTA differential thermal analysis
- the heat treatment time is not particularly limited as long as the desired crystallinity can be obtained.
- the heat treatment time is preferably in the range of 1 minute to 24 hours, and more preferably in the range of 1 minute to 10 hours.
- the heat treatment is preferably performed in an inert gas atmosphere (for example, a nitrogen atmosphere or an argon atmosphere) or a reduced pressure atmosphere (particularly in a vacuum). This is because deterioration (for example, oxidation) of the crystalline solid electrolyte can be prevented.
- the method for the heat treatment is not particularly limited, and examples thereof include a method using a vacuum heating device, an argon gas atmosphere furnace, and a firing furnace.
- the crystalline solid electrolyte obtained by the production method of the present invention includes, for example, alkali metals such as lithium, sodium, potassium, rubidium, cesium, and francium, and alkaline earth metals such as beryllium, magnesium, calcium, strontium, barium, and radium.
- alkali metals such as lithium, sodium, potassium, rubidium, cesium, and francium
- alkaline earth metals such as beryllium, magnesium, calcium, strontium, barium, and radium.
- a crystalline solid electrolyte containing at least one element selected from the group consisting of conductive species are preferable, and lithium is especially preferable.
- Examples of crystalline solid electrolytes include crystalline oxide solid electrolytes, crystalline sulfide solid electrolytes, etc., but they have high ionic conductivity and crystalline sulfide solid electrolytes in consideration of higher battery output. Is preferred.
- Examples of the crystalline sulfide solid electrolyte include a crystalline sulfide solid electrolyte containing lithium element, phosphorus element, and sulfur element, and a crystalline sulfide containing lithium element, phosphorus element, sulfur element, and halogen element.
- crystalline sulfide solid electrolyte examples include Li 2 S—P 2 S 5 , 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 —LiI—LiBr, Li 2 S—P 2 S 5 —Li 2 O, Li 2 S—P 2 S 5 —Li 2 O—LiI, Li 2 S—SiS 2 , Li 2 S—SiS 2 —LiI, Li 2 S—SiS 2 —LiBr, Li 2 S—SiS 2 —LiCl, Li 2 S—SiS 2 —B 2 S 3 —LiI, Li 2 S— SiS 2 -P 2 S 5 -LiI, Li 2 S-B 2 S 3, Li 2 S-P 2 S 5 -Z m S n (m, n is the number of positive .Z
- Examples of the crystalline oxide solid electrolyte include Li 2 O—B 2 O 3 —P 2 O 5 , Li 2 O—SiO 2 , LiLaTaO (for example, Li 5 La 3 Ta 2 O 12 ), LiLaZrO (for example, Li 7 La 3 Zr 2 O 12 ), LiBaLaTaO (eg, Li 6 BaLa 2 Ta 2 O 12 ), Li 1 + x Si x P 1-x O 4 (0 ⁇ x ⁇ 1, eg, Li 3.6 Si 0.6 P 0.4 O 4 ), Li 1 + x Al x Ge 2-x (PO 4 ) 3 (0 ⁇ x ⁇ 2), Li 1 + x Al x Ti 2-x (PO 4 ) 3 (0 ⁇ x ⁇ 2), Examples include Li 3 PO (4-3 / 2x) N x (0 ⁇ x ⁇ 1).
- the kind of element constituting the crystalline solid electrolyte obtained by the production method of the present invention can be confirmed by, for example, an ICP emission spectrometer.
- the crystalline structure of the crystalline sulfide solid electrolyte includes a Li 3 PS 4 crystal structure, a Li 4 P 2 S 6 crystal structure, a Li 7 PS 6 crystal structure, a Li 7 P 3 S 11 crystal structure, and a Li 4-x.
- Ge 1-x P x S 4 based Chiori axicon Region II (thio-LISICON Region II) type crystal structure (Kanno et al., Journal of The Electrochemical Society, 148 (7) A742-746 (2001) refer)
- Li 4-x Examples thereof include a crystal structure similar to that of Ge 1-x P x S 4 system thio-LISICON Region II type (see Solid State Ionics, 177 (2006), 2721-2725).
- an aldilodite-type crystal structure is also exemplified.
- the aldilodite type crystal structure for example, a composition formula Li 7-x P 1-y Si y having a Li 7 PS 6 crystal structure; Li 7 PS 6 structural skeleton, and substituting part of P with Si Crystal structure represented by S 6 and Li 7 + x P 1-y Si y S 6 (x is ⁇ 0.6 to 0.6, y is 0.1 to 0.6); Li 7-x-2y PS 6 ⁇ x-y Cl x (0.8 ⁇ x ⁇ 1.7,0 ⁇ y ⁇ -0.25x + 0.5) crystal structure represented by; Li 7-x PS 6- x Ha x (Ha is Cl or Br, and a crystal structure in which x is preferably 0.2 to 1.8).
- compositional formulas Li 7-x P 1-y Si y S 6 and Li 7 + x P 1-y Si y S 6 (which have the above Li 7 PS 6 structural skeleton and in which a part of P is substituted with Si (
- the crystal structure represented by the above composition formula Li 7-x PS 6-x Ha x (Ha is Cl or Br, x is preferably 0.2 to 1.8) is preferably cubic and CuK ⁇ ray.
- the crystalline structure of the crystalline solid electrolyte the composition formula Li x Si y P z S a Ha w (Ha , including Br, Cl, or more or one or two of the I and F ⁇ (Xy) / (y + z) ⁇ 3.3), the S content is 55 to 73% by mass, the Si content is 2 to 11% by mass, and the Ha element content is 0.02%.
- Li—Si—PS—appears at 2 ⁇ 20.2 °, 24.0 °, and 29.7 ° in X-ray diffraction measurement using CuK ⁇ rays.
- a crystal structure having a peak derived from the type crystal structure and a peak appearing at a position of 2 ⁇ 24.8 ° to 26.1 °. Note that these peak positions may move back and forth within a range of ⁇ 0.5 °.
- the crystalline solid electrolyte obtained by the present invention preferably has a configuration including an ionic conductor having lithium element (Li), phosphorus element (P), and sulfur element (S), and further, the ionic conductor. And lithium iodide (LiI) and lithium bromide (LiBr).
- the said ion conductor will not be specifically limited if it has a thium element (Li), a phosphorus element (P), and a sulfur element (S), it is preferable to have an ortho composition especially. This is because a sulfide solid electrolyte having high chemical stability can be obtained.
- ortho generally refers to one having the highest degree of hydration among oxo acids obtained by hydrating the same oxide.
- the crystal composition in which lithium sulfide (Li 2 S) is added most in the sulfide is referred to as an ortho composition.
- Li 3 PS 4 corresponds to the ortho composition.
- “having an ortho composition” includes not only a strict ortho composition but also a composition in the vicinity thereof. Specifically, it means that the main component is an ortho - structure anion structure (PS 4 3- structure).
- the ratio of the anion structure of the ortho composition is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, based on the total anion structure in the ion conductor, 90 mol % Or more is particularly preferable.
- the ratio of the anion structure of the ortho composition can be determined by Raman spectroscopy, nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), or the like.
- crystalline solid electrolyte obtained by the present invention is a crystalline sulfide solid electrolyte
- “Bridged sulfur” refers to bridged sulfur in a compound formed by reaction of lithium sulfide (Li 2 S) and diphosphorus pentasulfide (P 2 S 5 ).
- it corresponds to a sulfur bridge having an S 3 P—S—PS 3 structure obtained by reacting lithium sulfide (Li 2 S) and diphosphorus pentasulfide (P 2 S 5 ).
- Such bridging sulfur easily reacts with water and easily generates hydrogen sulfide.
- bridging sulfur is likely to occur.
- “Substantially free of bridging sulfur” can be confirmed by measurement of Raman spectroscopy.
- Raman spectroscopy For example, in the case of a Li 2 S—P 2 S 5 based sulfide solid electrolyte, the peak of the S 3 P—S—PS 3 structure usually appears at 402 cm ⁇ 1 . Therefore, it is preferable that this peak is not detected.
- the peak of the PS 4 3 ⁇ structure usually appears at 417 cm ⁇ 1 .
- the intensity I 402 at 402 cm -1 is preferably smaller than the intensity I 417 at 417 cm -1. More specifically, with respect to the intensity I 417 , the intensity I 402 is, for example, preferably 70% or less, more preferably 50% or less, and even more preferably 35% or less.
- the shape of the crystalline solid electrolyte is not particularly limited, and examples thereof include particles.
- the average particle diameter (D 50 ) of the particulate crystalline solid electrolyte is preferably in the range of 0.1 ⁇ m to 50 ⁇ m, for example.
- the average particle size (D 50 ) is a particle size at which 50% of the total particle size is accumulated from the smallest particle size when drawing a particle size distribution integration curve, and the volume distribution is, for example, laser diffraction / It can be measured using a scattering type particle size distribution measuring device.
- the crystalline solid electrolyte obtained by the production method of the present invention has high ionic conductivity, excellent battery performance, and is suitably used for batteries.
- the use of lithium element as the conductive species is particularly suitable.
- the solid electrolyte obtained by the production method of the present invention 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.
- the said battery uses a collector other than a positive electrode layer, an electrolyte layer, and a negative electrode layer, and a well-known thing can be used for a collector.
- a layer coated with Au or the like that reacts with the solid electrolyte such as Au, Pt, Al, Ti, or Cu, can be used.
- the method for producing an inorganic material according to the present invention is characterized in that a crystalline inorganic material is obtained by reacting two or more kinds of solid raw materials using a multi-axis kneader.
- the solid raw material is not particularly limited as long as it can react with each other and obtain a crystalline inorganic material.
- zinc sulfide-based light emitting material, molybdenum sulfide-based and vanadium alloy-based thermoelectric conversion materials, etc. Is mentioned.
- the multiaxial kneader may be the same as that used in the method for producing a solid electrolyte of the present invention.
- the temperature during the reaction of the solid raw material is preferably equal to or higher than the crystallization temperature of the crystal structure of the crystalline solid electrolyte obtained by the reaction of the solid raw material, and the other reaction conditions are the above-described method for producing a solid electrolyte.
- the crystallinity can be further improved by heat-treating the obtained crystalline inorganic material, which is the same as the above-described method for producing a solid electrolyte.
- an inorganic material of the present invention two or more kinds of solid raw materials are reacted using a general-purpose machine such as a multi-screw kneader, and a wide variety can be easily obtained with excellent productivity and mass productivity. Inorganic materials can be manufactured.
- the multi-axis kneader of the present invention is used for the production of a crystalline solid electrolyte including reacting two or more solid raw materials, which is the method for producing a solid electrolyte of the present invention.
- the configuration, use conditions, and the like of the multi-axis kneader of the present invention are the same as those described as being used in the method for producing a solid electrolyte of the present invention.
- the real part Z ′ ( ⁇ ) at the point where ⁇ Z ′′ ( ⁇ ) is the minimum is the bulk resistance R ( ⁇ ) of the electrolyte.
- the conductivity ⁇ (S / cm) was calculated.
- the distance between the leads was measured at about 60 cm.
- the purity of lithium sulfide was analyzed and measured by hydrochloric acid titration and silver nitrate titration. Specifically, the lithium sulfide powder obtained in the production example was weighed in a glove box (dew point: about ⁇ 100 ° C., nitrogen atmosphere), dissolved in water, and potentiometric titrator (“COM-980 (model number)) ”, Measured by Hiranuma Sangyo Co., Ltd.).
- Example 1 In a glove box filled with nitrogen, a feeder (“Micron Feeder (product name)”, manufactured by Aisin Nano Technologies), and a twin-screw kneader (“KRC Junior (product name)”, paddle diameter: ⁇ 8 mm, (Manufactured by Kurimoto Steel Works).
- a feeder Micron Feeder (product name)”, manufactured by Aisin Nano Technologies
- KRC Junior twin-screw kneader
- XRD powder X-ray analysis
- the Li 4-x Ge 1-x P x S 4 system thiolysicon region II A crystallization peak attributed to the crystal structure was detected.
- the obtained reaction product was heat-treated at 200 ° C. for 3 hours.
- the ionic conductivity measured by the above method was 3.0 ⁇ 10 ⁇ 3 S / cm, and it was a crystalline solid electrolyte. It was confirmed.
- the temperature of the outer surface of the casing of the kneader during kneading was a maximum of 80 ° C.
- a crystalline solid electrolyte can be obtained with excellent productivity.
- This crystalline solid electrolyte has high ionic conductivity, has excellent battery performance, and is suitably used for batteries.
- the use of lithium element as the conductive species is particularly suitable.
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Abstract
Description
[2]前記反応が、固体状態で行われる上記[1]に記載の固体電解質の製造方法。
[3]前記固体原料が、リチウム元素、リン元素、及び硫黄元素を含む、上記[1]又は[2]に記載の固体電解質の製造方法。
[4]前記固体原料が、リチウム化合物及びリチウム金属単体の少なくとも1つと、リン化合物及びリン単体の少なくとも1つとを含む、上記[3]に記載の固体電解質の製造方法。
[5]前記固体原料が、硫化リチウムと硫化リンとを含む、上記[3]又は[4]に記載の固体電解質の製造方法。
[6]前記固体原料が、さらにハロゲン元素を含む、上記[3]~[5]のいずれか1項に記載の固体電解質の製造方法。
[7]前記ハロゲン元素が、臭素及びヨウ素の少なくとも1種である、上記[6]に記載の固体電解質の製造方法。
[8]前記固体原料が、臭化リチウム及びヨウ化リチウムの少なくとも1つを含む、上記[6]又は[7]に記載の固体電解質の製造方法。
[9]多軸混練機を用いて、2種以上の固体原料を反応させ、結晶性の無機材料を得ることを含む、無機材料の製造方法。
[10]2種以上の固体原料を反応させることを含む結晶性の固体電解質の製造に用いられる多軸混練機。
[12]多軸混練機を用いて、硫化リチウム、硫化リン、並びに臭化リチウム及びヨウ化リチウムの少なくとも1つを含む2種以上の固体原料を反応させ、リチウム元素、リン元素、硫黄元素、並びに臭素元素及びヨウ素元素の少なくとも1つを含む結晶性の固体電解質を得ることを含む、固体電解質の製造方法。
[13]多軸混練機を用いて、硫化リチウム、硫化リンを含む2種以上の固体原料を反応させ、リチウム元素、リン元素、及び硫黄元素を含む結晶性の固体電解質を得ることを含み、該反応時の温度が、該結晶性固体電解質が有する結晶構造の結晶化温度以上である、固体電解質の製造方法。
[14]多軸混練機を用いて、硫化リチウム、硫化リン、並びに臭化リチウム及びヨウ化リチウムの少なくとも1つを含む2種以上の固体原料を反応させ、リチウム元素、リン元素、硫黄元素、並びに臭素元素及びヨウ素元素の少なくとも1つを含む結晶性の固体電解質を得ることを含み、該反応時の温度が、該結晶性固体電解質が有する結晶構造の結晶化温度以上である、固体電解質の製造方法。
[15]多軸混練機を用いて、硫化リチウム、五硫化二リンを含む2種以上の固体原料を反応させ、リチウム元素、リン元素、及び硫黄元素を含む結晶性の固体電解質を得ることを含む、固体電解質の製造方法。
[16]多軸混練機を用いて、硫化リチウム、五硫化二リン、並びに臭化リチウム及びヨウ化リチウムの少なくとも1つを含む2種以上の固体原料を反応させ、リチウム元素、リン元素、硫黄元素、並びに臭素元素及びヨウ素元素の少なくとも1つを含む結晶性の固体電解質を得ることを含む、固体電解質の製造方法。
[17]多軸混練機を用いて、硫化リチウム、五硫化二リンを含む2種以上の固体原料を反応させ、リチウム元素、リン元素、及び硫黄元素を含む結晶性の固体電解質を得ることを含み、該反応時の温度が、該結晶性固体電解質が有する結晶構造の結晶化温度以上である、固体電解質の製造方法。
[18]多軸混練機を用いて、硫化リチウム、五硫化二リン、並びに臭化リチウム及びヨウ化リチウムの少なくとも1つを含む2種以上の固体原料を反応させ、リチウム元素、リン元素、硫黄元素、並びに臭素元素及びヨウ素元素の少なくとも1つを含む結晶性の固体電解質を得ることを含み、該反応時の温度が、該結晶性固体電解質が有する結晶構造の結晶化温度以上である、固体電解質の製造方法。
本発明の固体電解質の製造方法は、多軸混練機を用いて、2種以上の固体原料を反応させ、結晶性の固体電解質を得ることを含むことを特徴とするものである。
本発明において、結晶性の固体電解質は、X線回折測定においてX線回折パターンに、固体電解質由来のピークが観測される固体電解質であって、これらにおいて固体電解質原料由来のピークの有無は問わない材料である。すなわち、結晶性の固体電解質は、固体電解質に由来する結晶構造を含み、その一部が該固体電解質に由来する結晶構造であっても、その全部が該固体電解質に由来する結晶構造であってもよい、ものである。そして、結晶性の固体電解質は、上記のようなX線回折パターンを有していれば、その一部に非晶質の固体電解質が含まれていてもよいものである。
なお、上記の非晶質の固体電解質は、X線回折測定においてX線回折パターンが実質的に材料由来のピーク以外のピークが観測されないハローパターンであるもののことであり、固体電解質原料由来のピークの有無は問わないものである。
本発明の製造方法で用いられる固体原料は、一般に結晶性の固体電解質を構成する元素を含むものであれば、特に制限なく用いることができる。例えば、イオン伝導性を発現する伝導種としては、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、フランシウム等のアルカリ金属、ベリリウム、マグネシウム、カルシウム、ストロンチウム、バリウム、ラジウム等のアルカリ土類金属から選ばれる少なくとも1種の元素が好ましく、イオン伝導度が高く、電池の高出力化を考慮すると、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、フランシウム等のアルカリ金属、及びベリリウムがより好ましく、特にリチウムが好ましい。すなわち、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、フランシウム等のアルカリ金属、ベリリウム、マグネシウム、カルシウム、ストロンチウム、バリウム、ラジウム等のアルカリ土類金属から選ばれる少なくとも1種の元素を含む固体原料が好ましく、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、フランシウム等のアルカリ金属、及びベリリウムから選ばれる少なくとも1種の元素を含む固体原料がより好ましく、特にリチウム元素を含む固体原料が好ましい。
具体的には、炭化水素系有機溶媒中で水酸化リチウムと硫化水素とを70~300℃で反応させて、水硫化リチウムを生成し、次いでこの反応液を脱硫化水素化することにより硫化リチウムを合成できる(特開2010-163356号公報)。また、水溶媒中で水酸化リチウムと硫化水素とを10~100℃で反応させて、水硫化リチウムを生成し、次いでこの反応液を脱硫化水素化することにより硫化リチウムを合成できる(特開2011-84438号公報)。
また、溶媒不存在下で、水酸化リチウムと硫化水素とを反応させることによっても硫化リチウムを合成できる。この場合の反応温度は、例えば20~300℃、100~250℃、120~240℃である。
Xは、フッ素(F)、塩素(Cl)、臭素(Br)、及びヨウ素(I)から選択されるハロゲン元素である。
また、lは1又は2の整数であり、mは1~10の整数である。mが2~10の整数の場合、すなわち、Xが複数存在する場合は、Xは同じであってもよいし、異なっていてもよい。例えば、後述するSiBrCl3は、mが4であって、XはBrとClという異なる元素からなるものである。
なお、結晶性の固体電解質が、a((1-b)LiI・bLiBr)・(1-a)(cLi2S・(1-c)P2S5)の組成を有する場合、aが上記LiI及びLiBrの合計の割合に該当し、bが上記LiBrの割合に該当し、cが上記Li2Sの割合に該当する。
本発明の製造方法で用いられる多軸混練機としては、例えば、ケーシングと、該ケーシングを長手方向に貫通するように配され、軸方向に沿ってパドル(スクリュー羽根)が設けられた2本以上の回転軸と備え、該ケーシングの長手方向の一端に固体原料の供給口、他端に排出口を備えたものであれば、他の構成は特に制限はない。このような多軸混練機のパドルが設けられた2本以上の回転軸を回転させることにより、2以上の回転運動が相互に作用してせん断応力が生じ、このせん断応力が該回転軸に沿って供給口から排出口の方向に向かって移動する固体原料に加えられることで、該固体原料を反応させつつ結晶化することが可能になると考えられる。
図1に示される多軸混練機は、一端に供給口2、他端に排出口3を備えるケーシング1、該ケーシング1の長手方向に貫通するように2つの回転軸4a、及び4bを備える2軸混練機である。該回転軸4a及び4bには、各々パドル5a及び5bが設けられている。固体原料は、供給口2からケーシング1内に入り、パドル5a及び5bにおいてせん断応力が加えられて反応させ、結晶化した反応物、すなわち結晶性の固体電解質は排出口3から排出される。
回転軸4は互いに平行である平行軸であってもよいし、斜交型であってもよく、また回転軸の回転方向は同方向であってもよいし、異方向であってもよい。回転方向は、より混練の効果を得ようとする場合は異方向を選択すればよく、またケーシング内の固体原料、及び反応物を掃き取り、これらのケーシング内における滞留を抑える自己清掃効果を重視する場合は同方向を選択すればよい。
結晶性の固体電解質の製造方法としては、上記のように、メカニカルミリング法、スラリー法、溶融急冷法等により非晶質の固体電解質を得た後、さらに熱処理を施すことが一般的に行われてきた。これらの方法では、特殊な設備を必要とする、あるいは炭化水素系有機溶媒を使用する必要があるため、生産性に優れているとはいえない。しかし、本発明のように、多軸混練機のような汎用機械を用いて固体原料を反応させることにより、これらの製造方法に比べて優れた生産性が得られることとなった。
本発明において、固体原料の反応時の温度は、固体原料の反応により得られる結晶性の固体電解質が有する結晶構造の結晶化温度以上であることが好ましい。このような温度で反応させることにより、固体原料は反応しつつ結晶化して、結晶性の固体電解質となるため、優れた生産性で目的とする固体電解質が得られる。
ここで、本発明における結晶化温度は、結晶性の固体電解質が有する結晶構造の結晶化温度、すなわち結晶性の固体電解質を得るために必要な固体原料を用いて得られる非晶質の固体電解質の結晶化温度であり、示差熱分析(DTA)により確認、測定することができる。例えば、示差熱分析装置(DTA装置)を用いて、10℃/分の昇温条件で示差熱分析(DTA)を行い測定される、最も低温側で観測される発熱ピークを示す温度が結晶化温度である。
また、固体原料の反応は乾燥雰囲気下で行われることが好ましく、例えば、露点-90℃以上-40℃以下の雰囲気で行うことが好ましく、露点-90℃以上-45℃以下の雰囲気で行うことがより好ましく、露点-90℃以上-50℃以下の雰囲気で行うことがさらに好ましい。これを実現するためには、例えば多軸混練機をグローブボックス内に設置する方法、多軸混練機をドライルームに設置する方法が挙げられる。また、例えば、多軸混練機のケーシング内に上記不活性ガスを連続的に供給する方法によっても実現できる。この場合、多軸混練機のケーシングには、不活性ガスを供給する供給口、排出口を設けておけばよい。
本発明において、上記のようにして得られた結晶性の固体電解質の結晶性をさらに向上させる観点から、熱処理を施してもよい。すなわち、本発明の製造方法は、さらに結晶性の固体電解質を熱処理することを含んでいてもよい。
熱処理温度は、所望の結晶性の固体電解質を得るために必要な固体原料を用いて得られる非晶質の固体電解質について、示差熱分析装置(DTA装置)を用いて、10℃/分の昇温条件で示差熱分析(DTA)を行い、最も低温側で観測される発熱ピークのピークトップを起点に好ましくは±40℃、より好ましくは±30℃、さらに好ましくは±20℃の範囲とすればよい。
また、熱処理は、不活性ガス雰囲気(例えば、窒素雰囲気、アルゴン雰囲気)、または減圧雰囲気(特に真空中)で行なうことが好ましい。結晶性の固体電解質の劣化(例えば、酸化)を防止できるからである。熱処理の方法は、特に限定されるものではないが、例えば、真空加熱装置、アルゴンガス雰囲気炉、焼成炉を用いる方法等を挙げることができる。
本発明の製造方法によって得られる結晶性の固体電解質は、例えば、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、フランシウム等のアルカリ金属、ベリリウム、マグネシウム、カルシウム、ストロンチウム、バリウム、ラジウム等のアルカリ土類金属から選ばれる少なくとも1種の元素を伝導種として含む、結晶性の固体電解質が挙げられる。これらの中でも、元素としては、イオン伝導度が高く、電池の高出力化を考慮すると、リチウム、ナトリウム、カリウム、ルビジウム、セシウム、フランシウム等のアルカリ金属、及びベリリウムが好ましく、特にリチウムが好ましい。
結晶性の硫化物固体電解質としては、例えば、リチウム元素、リン元素、及び硫黄元素を含む結晶性の硫化物固体電解質、リチウム元素、リン元素、硫黄元素、及びハロゲン元素を含む結晶性の硫化物固体電解質、リチウム元素、リン元素、硫黄元素、及び臭素元素を含む結晶性の硫化物固体電解質、リチウム元素、リン元素、硫黄元素、及びヨウ素元素を含む結晶性の硫化物固体電解質、リチウム元素、リン元素、硫黄元素、臭素元素、及びヨウ素元素を含む結晶性の硫化物固体電解質が挙げられる。結晶性硫化物固体電解質としては、より具体的には、Li2S-P2S5、Li2S-P2S5-LiI、Li2S-P2S5-LiCl、Li2S-P2S5-LiBr、Li2S-P2S5-LiI-LiBr、Li2S-P2S5-Li2O、Li2S-P2S5-Li2O-LiI、Li2S-SiS2、Li2S-SiS2-LiI、Li2S-SiS2-LiBr、Li2S-SiS2-LiCl、Li2S-SiS2-B2S3-LiI、Li2S-SiS2-P2S5-LiI、Li2S-B2S3、Li2S-P2S5-ZmSn(m、nは正の数。Zは、Si、Ge、Zn、Ga、Sn、Alのいずれか。)、Li2S-GeS2、Li2S-SiS2-Li3PO4、Li2S-SiS2-LixMOy(x、yは正の数。Mは、P、Si、Ge、B、Al、Ga、Inのいずれか。)、Li10GeP2S12等が挙げられる。
例えば、結晶性硫化物固体電解質の結晶構造としては、Li3PS4結晶構造、Li4P2S6結晶構造、Li7PS6結晶構造、Li7P3S11結晶構造、Li4-xGe1-xPxS4系チオリシコンリージョンII(thio-LISICON Region II)型結晶構造(Kannoら、Journal of The Electrochemical Society,148(7)A742-746(2001)参照)、Li4-xGe1-xPxS4系チオリシコンリージョンII(thio-LISICON Region II)型と類似の結晶構造(Solid State Ionics,177(2006),2721-2725参照)等が挙げられる。
なお、これらのピーク位置については、±0.5°の範囲内で前後していてもよい。
上記イオン伝導体は、チウム元素(Li)、リン元素(P)、及び硫黄元素(S)を有するものであれば特に限定されるものではないが、中でも、オルト組成を有することが好ましい。化学的安定性の高い硫化物固体電解質とすることができるからである。ここで、オルトとは、一般的に、同じ酸化物を水和して得られるオキソ酸の中で、最も水和度の高いものをいう。本発明においては、硫化物で最も硫化リチウム(Li2S)が付加している結晶組成をオルト組成という。例えば、Li2S-P2S5系ではLi3PS4がオルト組成に該当する。結晶性硫化物固体電解質がLi2S-P2S5である場合、オルト組成を得る硫化リチウム(Li2S)と五硫化二リン(P2S5)と割合は、モル基準で、Li2S:P2S5=75:25である。
このような架橋硫黄は、水と反応しやすく、硫化水素が発生しやすい。例えば、全材料における硫化リチウム(Li2S)の割合が少ないと、架橋硫黄が生じやすい。「架橋硫黄を実質的に含有しない」ことは、ラマン分光スペクトルの測定により、確認することができる。例えば、Li2S-P2S5系の硫化物固体電解質の場合、S3P-S-PS3構造のピークが、通常402cm-1に現れる。そのため、このピークが検出されないことが好ましい。また、PS4 3-構造のピークは、通常417cm-1に現れる。本発明においては、402cm-1における強度I402が、417cm-1における強度I417よりも小さいことが好ましい。より具体的には、強度I417に対して、強度I402は、例えば、70%以下であることが好ましく、50%以下であることがより好ましく、35%以下であることがさらに好ましい。
また、上記電池は、正極層、電解質層及び負極層の他に集電体を使用することが好ましく、集電体は公知のものを用いることができる。例えば、Au、Pt、Al、Ti、又は、Cu等のように、上記の固体電解質と反応するものをAu等で被覆した層が使用できる。
本発明の無機材料の製造方法は、多軸混練機を用いて、2種以上の固体原料を反応させ、結晶性の無機材料を得ることを含む、ことを特徴とするものである。固体原料としては、固体原料同士で反応し、結晶性の無機材料が得られるようなものであれば特に制限はなく、例えば硫化亜鉛系発光材料、硫化モリブデン系及びバナジウム合金系の熱電変換材料等が挙げられる。
固体原料の反応時の温度は、固体原料の反応により得られる結晶性の固体電解質が有する結晶構造の結晶化温度以上であることが好ましいこと、その他の反応条件は、上記の固体電解質の製造方法と同じであり、また得られた結晶性の無機材料を熱処理することで結晶性をさらに向上させることができることも、上記の固体電解質の製造方法と同じである。
本発明の無機材料の製造方法によれば、多軸混練機のような汎用機械を用いて2種以上の固体原料を反応させて、簡便に、優れた生産性及び量産性で、多種多様な無機材料を製造することが可能となる。
本発明の多軸混練機は、本発明の固体電解質の製造方法である、2種以上の固体原料を反応させることを含む結晶性の固体電解質の製造に用いられるものである。本発明の多軸混練機の構成、及び使用条件等は、上記の本発明の固体電解質の製造方法で用いられるものとして説明したものと同じである。
実施例及び比較例で得られた固体電解質を、それぞれ断面10mmφ(断面積S=0.785cm2)、高さ(L)0.1~0.3cmの形状に成形し、試料片を作成した。当該試料片の上下から電極端子を取り、交流インピーダンス法により測定し(周波数範囲:5MHz~0.5Hz、振幅:10mV)、Cole-Coleプロットを得た。高周波側領域に観測される円弧の右端付近で、-Z’’(Ω)が最小となる点での実数部Z’(Ω)を電解質のバルク抵抗R(Ω)とし、下記式に従い、イオン伝導度σ(S/cm)を計算した。
R=ρ(L/S)
σ=1/ρ
本実施例ではリードの距離を約60cmとして測定した。
硫化リチウムの純度は、塩酸滴定、及び硝酸銀滴定により分析し、測定した。具体的には、製造例で得られた硫化リチウム粉末を、グローブボックス(露点:-100℃程度、窒素雰囲気)内で秤量後、水に溶解し、電位差滴定装置(「COM-980(型番)」、平沼産業(株)製)を用いて測定し、算出した。
撹拌機付きのセパラブルフラスコ(500mL)に、窒素気流下で乾燥した水酸化リチウム(LiOH)無水物(本荘ケミカル(株)製)200gを投入した。窒素気流下で昇温し、内部温度を200℃に保持し、窒素を硫化水素(住友精化(株)製)に切り替えて、500mL/分の流量で供給し、水酸化リチウムと硫化水素との反応を進行させた。反応の進行に伴い発生する水分は、コンデンサで凝縮して回収した。反応を6時間(硫化水素導入後6時間)行った時点で水は144mL回収された。さらに3時間反応を継続したが、水の発生は見られなかった。粉末状の生成物を回収し、上記の方法で純度の測定を行ったところ、純度は98.5%であった。また、粉末X線回折(XRD)測定を行ったところ、硫化リチウム(Li2S)特有のピークパターンを示していた。
窒素を充填したグローブボックス内に、フィーダー(「マイクロンフィーダー(製品名)」、(株)アイシンナノテクノロジーズ社製)、及び二軸混練機(「KRCジュニア(製品名)」、パドル径:φ8mm、(株)栗本鐡工所製)を設置した。製造例で得られた硫化リチウム(Li2S)3.828gと、五硫化二リン(P2S5)6.172gの混合物(Li2S:P2S5=75:25(モル比))を固体原料とし、フィーダーから混練機の供給口に一定速度で供給し、平均モータートルク0.8Nm(負荷率:60%)、スクリュー回転数:150rpmで混練を開始した。供給口から固体原料を供給し、約30分後に排出口から反応物が排出された。排出された反応物を、再びフィーダーに戻して混練する操作を繰り返した。
得られた反応物の粉末X線解析(XRD)測定を行ったところ、図3のX線解析スペクトルに示されるように、βLi3PS4の結晶構造に帰属する結晶化ピークが検出され、該反応物を上記の方法で測定したイオン伝導度は2.0×10-4S/cmであることから、結晶構造を有する結晶性の固体電解質が得られたことが確認された。混練時の混練機のケーシングの外面の温度は最大90℃であった。
実施例1において、固体原料を、硫化リチウム(Li2S)2.78g、五硫化二リン(P2S5)4.435g、ヨウ化リチウム(LiI)1.425g、及び臭化リチウム(LiBr)1.385gの混合物(Li2S:P2S5:LiI:LiBr=56.25:18.75:10:15(モル比))とした以外は実施例1と同様にして、反応物を得た。
得られた反応物の粉末X線解析(XRD)測定を行ったところ、図4のX線解析スペクトルに示されるように、Li4-xGe1-xPxS4系チオリシコンリージョンIIの結晶構造に帰属する結晶化ピークが検出された。得られた反応物を、200℃で3時間の熱処理を施したものについて、上記の方法で測定したイオン伝導度は3.0×10-3S/cmであり、結晶性の固体電解質であることが確認された。混練時の混練機のケーシング外面の温度は最大80℃であった。
2.供給口
3.排出口
4a、4b.回転軸
5a、5b.パドル
6a、6b.スクリュー
7a、7b.リバーススクリュー
Claims (10)
- 多軸混練機を用いて、2種以上の固体原料を反応させ、結晶性の固体電解質を得ることを含む、固体電解質の製造方法。
- 前記反応が、固体状態で行われる請求項1に記載の固体電解質の製造方法。
- 前記固体原料が、リチウム元素、リン元素、及び硫黄元素を含む、請求項1又は2に記載の固体電解質の製造方法。
- 前記固体原料が、リチウム化合物及びリチウム金属単体の少なくとも1つと、リン化合物及びリン単体の少なくとも1つとを含む、請求項3に記載の固体電解質の製造方法。
- 前記固体原料が、硫化リチウムと硫化リンとを含む、請求項3又は4に記載の固体電解質の製造方法。
- 前記固体原料が、さらにハロゲン元素を含む、請求項3~5のいずれか1項に記載の固体電解質の製造方法。
- 前記ハロゲン元素が、臭素及びヨウ素の少なくとも1種である、請求項6に記載の固体電解質の製造方法。
- 前記固体原料が、臭化リチウム及びヨウ化リチウムの少なくとも1つを含む、請求項6又は7に記載の固体電解質の製造方法。
- 多軸混練機を用いて、2種以上の固体原料を反応させ、結晶性の無機材料を得ることを含む、無機材料の製造方法。
- 2種以上の固体原料を反応させることを含む結晶性の固体電解質の製造に用いられる多軸混練機。
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US20180170756A1 (en) | 2018-06-21 |
EP3312847A4 (en) | 2018-12-26 |
US10781101B2 (en) | 2020-09-22 |
JPWO2016204255A1 (ja) | 2018-04-05 |
EP3312847A1 (en) | 2018-04-25 |
CN107710346A (zh) | 2018-02-16 |
EP3312847A8 (en) | 2018-06-20 |
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