WO2019187943A1 - Negative electrode active material for fluoride ion secondary batteries, negative electrode using said active material, fluoride ion secondary battery, and method for producing said active material - Google Patents

Negative electrode active material for fluoride ion secondary batteries, negative electrode using said active material, fluoride ion secondary battery, and method for producing said active material Download PDF

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WO2019187943A1
WO2019187943A1 PCT/JP2019/007699 JP2019007699W WO2019187943A1 WO 2019187943 A1 WO2019187943 A1 WO 2019187943A1 JP 2019007699 W JP2019007699 W JP 2019007699W WO 2019187943 A1 WO2019187943 A1 WO 2019187943A1
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fluoride
ion secondary
negative electrode
active material
secondary battery
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PCT/JP2019/007699
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French (fr)
Japanese (ja)
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森田　善幸
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本田技研工業株式会社
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Priority to JP2020510484A priority Critical patent/JP7178404B2/en
Priority to CN201980022002.1A priority patent/CN112042018B/en
Priority to DE112019001579.6T priority patent/DE112019001579T5/en
Publication of WO2019187943A1 publication Critical patent/WO2019187943A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/48—Halides, with or without other cations besides aluminium
    • C01F7/50—Fluorides
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/48—Halides, with or without other cations besides aluminium
    • C01F7/50—Fluorides
    • C01F7/54—Double compounds containing both aluminium and alkali metals or alkaline-earth metals
    • 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
    • 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
    • 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
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/381—Alkaline or alkaline earth metals elements
    • H01M4/382—Lithium
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/582—Halogenides
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/85—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by XPS, EDX or EDAX data
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0068—Solid electrolytes inorganic
    • H01M2300/008—Halides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • 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 negative electrode active material for a fluoride ion secondary battery, a negative electrode using the active material, a fluoride ion secondary battery, and a method for producing the active material.
  • lithium ion secondary batteries are widely used as secondary batteries having high energy density.
  • a lithium ion secondary battery has a structure in which a separator is present between a positive electrode and a negative electrode and a liquid electrolyte (electrolytic solution) is filled.
  • the fluoride ion secondary battery is a secondary battery using fluoride ions (F ⁇ ) as carriers, and is known to have high theoretical energy. And about the battery characteristic, there exists an expectation exceeding a lithium ion secondary battery.
  • Non-Patent Documents 1 and 2 As the negative electrode active material of the fluoride ion secondary battery, MgF 2, CaF 2, CeF 3 and the like have been reported (see Non-Patent Documents 1 and 2).
  • the currently reported fluoride ion secondary batteries using these negative electrode active materials have a problem that their charge / discharge efficiency is 10 to 20%, and energy efficiency as a secondary battery is low.
  • the charge / discharge capacity is only about 10 to 20% of the theoretical capacity, and the capacity has not been increased as compared with the current Li ion secondary battery or Ni-MH battery.
  • the reduction-side potential window of LBF is ⁇ 2.41 V vs.
  • La / LaF 3 potential calculated from Gibbs energy. Subject to constraints in the Pb / PbF 2.
  • the potential of the negative electrode active material of the fluoride ion secondary battery currently reported is that MgF 2 is ⁇ 2.35 to ⁇ 2.87 V vs. Pb / PbF 2 and CaF 2 are in a range of ⁇ 2.85 to ⁇ 2.89 V vs. Pb / PbF 2 and CeF 3 are in the range of ⁇ 2.18 to ⁇ 2.37 V vs. It is a Pb / PbF 2. Therefore, there has been a problem that the defluorination / refluorination reaction of the negative electrode active material under the restriction of -2.41 V, which is the reduction potential window of LBF, cannot be provided in consideration of the overvoltage.
  • the present invention has been made in view of the above-described background art, and an object of the present invention is for a fluoride ion secondary battery capable of expressing a reversible negative electrode reaction at a high utilization rate in a fluoride ion secondary battery.
  • the object is to provide a negative electrode active material, a negative electrode using the active material, a fluoride ion secondary battery, and a method for producing the active material.
  • AlF 3 -1.V
  • Aluminum fluoride (AlF 3 ) has a charge / discharge reaction (defluorination / refluorination reaction) within the constraint of the potential window of 2.41 V of LBF, which is a fluoride ion solid electrolyte. 78V vs. Pb / PbF2).
  • Aluminum fluoride (AlF 3 ) has a sufficient redox potential within the LBF reduction-side potential window ( ⁇ 2.41 V vs. Pb / PbF 2) even if the overvoltage of the negative electrode reaction is assumed to be about 0.5 V. .
  • AlF 3 aluminum fluoride
  • AlF 3 aluminum fluoride
  • F ⁇ fluoride ions
  • Negative electrode reaction does not occur.
  • AlF 3 aluminum fluoride
  • AlF 3 has a six-coordinate octahedral perfect crystal structure. The inventor considered that this crystal structure hinders the defluorination / refluorination reaction.
  • fluoride ions (F ⁇ ) are partially desorbed from aluminum fluoride (AlF 3 ) in advance, and aluminum fluoride (AlF 3 ) is modified so as to provide holes at positions where fluorine atoms existed.
  • the vacancies serve as a starting point for the defluorination / refluorination reaction, and it was found that a desired negative electrode reaction can be expressed with high utilization and reversibility, and the present invention has been completed.
  • the present invention is a negative electrode active material for a fluoride ion secondary battery, which is a modified aluminum fluoride having pores due to desorption of fluoride ions.
  • the vacancies may be the starting point for the defluorination reaction and the refluorination reaction.
  • the holes may be regions where fluorine atoms existed in the aluminum fluoride before modification.
  • the desorption of fluoride ions may be performed by contacting aluminum fluoride with an alkali metal or an alkaline earth metal.
  • Another embodiment of the present invention is a negative electrode for a fluoride ion secondary battery comprising the negative electrode active material for a fluoride ion secondary battery.
  • Another embodiment of the present invention is a fluoride ion secondary battery comprising the above-described negative electrode for a fluoride ion secondary battery, a solid electrolyte, and a positive electrode.
  • Another aspect of the present invention is a method for producing a modified aluminum fluoride to be a negative electrode active material for a fluoride ion secondary battery, wherein the aluminum fluoride is brought into contact with an alkali metal or an alkaline earth metal,
  • the alkali metal or alkaline earth metal may be a fluoride
  • the aluminum fluoride may be one in which some fluorine atoms are extracted and not an aluminum metal.
  • the ratio of the alkali metal or the alkaline earth metal may be 5 to 20 mol% with respect to the total with the aluminum fluoride.
  • the aluminum fluoride may be ⁇ -AlF 3 .
  • the alkali metal may be Li metal.
  • a reversible negative electrode reaction in a fluoride ion secondary battery can be expressed with high utilization and high reversibility.
  • the charge / discharge capacity of the fluoride ion secondary battery can be significantly increased.
  • ⁇ Negative electrode active material for fluoride ion secondary battery The negative electrode of the fluoride ion secondary battery, fluoride ions during discharge (F -) accommodates, fluoride ions during charging - should those capable of releasing (F).
  • the negative electrode active material for a fluoride ion secondary battery of the present invention is a modified aluminum fluoride having pores due to desorption of fluoride ions.
  • AlF 3 aluminum fluoride
  • AlF 3 aluminum fluoride
  • the negative electrode reaction due to (F ⁇ ) desorption and reinsertion (defluorination / refluorination reaction) does not proceed.
  • a prior example using aluminum fluoride (AlF 3 ) alone as an active material has been reported as a positive electrode active material for lithium ion batteries (see Reference 6), but fluoride ions (F ⁇ ) Has not been reported for fluoride ion secondary batteries.
  • Reference 6 J.A. Appl Electrochem (2017) 47 417-431
  • the modified aluminum fluoride serving as the negative electrode active material for the fluoride ion secondary battery of the present invention has pores in the aluminum fluoride (AlF 3 ) due to the elimination of fluoride ions (F ⁇ ).
  • the pores of the modified aluminum fluoride serve as starting points for the defluorination reaction and the refluorination reaction. That is, the presence of vacancies modifies aluminum fluoride (AlF 3 ), which is an ionic and electronically non-conductive insulator, and has high utilization and high reversibility. The reaction proceeds.
  • AlF 3 aluminum fluoride
  • FIG. 3 is a diagram showing the structure of ⁇ -AlF 3 which is one of the crystal structures of aluminum fluoride (AlF 3 ).
  • the structure of aluminum fluoride (AlF 3 ) serving as a structural unit of the crystal structure is a six-coordinate eight structure in which an Al atom 1 is arranged at the center and a vertex is composed of six fluorine atoms 2. It is a face.
  • the vacancies are formed in a region where fluorine atoms existed in the unmodified aluminum fluoride (AlF 3 ) used as a raw material. That is, as shown in FIG. 3, Al atom 1 is arranged at the center, and among the six fluorine atoms 2 existing at the apex, some fluorine atoms 2 are extracted, and there are fluorine atoms 2 that are extracted and desorbed. The position where it has become a hole.
  • the negative electrode for a fluoride ion secondary battery of the present invention includes the negative electrode active material for a fluoride ion secondary battery of the present invention. If the negative electrode active material for fluoride ion secondary batteries of this invention is included, another structure will not be specifically limited.
  • the negative electrode for a fluoride ion secondary battery of the present invention preferably has a structure that increases the contact area with the solid electrolyte as a structure having a high surface area such as a porous structure.
  • the negative electrode for fluoride ion secondary batteries of the present invention may contain other components in addition to the negative electrode active material for fluoride ion secondary batteries of the present invention.
  • other components include a conductive aid and a binder.
  • the negative electrode for a fluoride ion secondary battery of the present invention is obtained, for example, by applying a mixture containing the negative electrode active material for a fluoride ion secondary battery of the present invention, a conductive additive, and a binder onto a current collector. It can be obtained by drying.
  • the fluoride ion secondary battery of the present invention includes a negative electrode for a fluoride ion secondary battery containing the negative electrode active material for a fluoride ion secondary battery of the present invention, a solid electrolyte, and a positive electrode. If the negative electrode containing the negative electrode active material for fluoride ion secondary batteries of this invention is used for the fluoride ion secondary battery of this invention, another structure will not be specifically limited.
  • a positive electrode material that provides a sufficiently high standard electrode potential with respect to the standard electrode potential of the negative electrode for a fluoride ion secondary battery including the negative electrode active material for a fluoride ion secondary battery of the present invention is selected.
  • the characteristics as a fluoride ion secondary battery are high, and a desired battery voltage can be realized.
  • the method for producing a modified aluminum fluoride serving as a negative electrode active material for a fluoride ion secondary battery comprises contacting aluminum fluoride with an alkali metal or alkaline earth metal, and then converting the aluminum fluoride into a fluoride. By desorbing the ions, the aluminum fluoride is modified using the positions of the fluorine atoms desorbed as fluoride ions as vacancies.
  • Aluminum fluoride (AlF 3 ) has various crystal structures. Examples of the crystal structure include ⁇ -AlF 3 , ⁇ -AlF 3 , ⁇ -AlF 3 , and the like. However, in any crystal structure, the structural unit is the same structure.
  • FIG. 3 showing the structure of a is alpha-AlF 3 single crystal structure of aluminum fluoride (AlF 3), aluminum fluoride as the constituent unit of the crystal structure (AlF 3)
  • AlF 3 aluminum fluoride as the constituent unit of the crystal structure
  • the structure is a six-coordinate octahedron in which an Al atom is arranged at the center and a vertex is composed of six fluorine atoms.
  • the structure of the aluminum fluoride used as a starting material is not limited particularly, aluminum fluoride of any crystal structure (AlF 3) may also be used.
  • AlF 3 aluminum fluoride of any crystal structure
  • ⁇ -AlF 3 is preferably used from the viewpoint of availability and the lowest cost. Examples of commercially available alpha-AlF 3, for example, can be cited and Sigma-Aldrich AlF 3 (purity 99.9%), Alfa Aesar Co. AlF 3 (purity 99.9%), and the like.
  • Aluminum fluoride (AlF 3 ) absorbs moisture in the air and forms a more stable 0.5 hydrate or trihydrate. For this reason, it is more preferable to use aluminum fluoride (AlF 3 ) that has been subjected to dehydration treatment.
  • the dehydration method include a vacuum baking method at a temperature of about 250 to 300 ° C.
  • alkali metal or alkaline earth metal used for producing the negative electrode active material for fluoride ion secondary batteries of the present invention is not particularly limited.
  • alkali metal include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).
  • alkaline earth metal include magnesium ( Mg), calcium (Ca), strontium (Sr), barium (Ba), and the like.
  • lithium (Li) metal among alkali metals or alkaline earth metals. Since lithium (Li) metal is the lightest of all the metal elements, the capacity per active material weight (mAh / g) after mixing with aluminum fluoride can be kept high.
  • the shape of the lithium (Li) metal is not particularly limited, but is preferably a chip shape or a bead shape from the viewpoint of easy mixing with aluminum fluoride (AlF 3 ).
  • AlF 3 aluminum fluoride
  • reaction mechanism By contacting an alkali metal or alkaline earth metal having a lower potential with the defluorination / refluorination reaction potential of aluminum fluoride (AlF 3 ), the alkali metal or alkaline earth metal is converted to fluoride. And a reaction in which some fluorine atoms are extracted from aluminum fluoride (AlF 3 ) occurs. Such partial extraction of fluorine atoms from fluoride due to contact with a base metal has not been confirmed as a prior example.
  • the manufacturing method of the negative electrode active material for fluoride ion secondary battery of the present invention does not desorb all six fluorine atoms. That is, only some of the fluorine atoms are extracted, and the reaction is not performed until aluminum fluoride (AlF 3 ) becomes an aluminum metal.
  • AlF 3 aluminum fluoride
  • the reaction does not proceed to the stage of formula (2) and formula (3) in which aluminum fluoride (AlF 3 ) becomes an aluminum metal, and only a part of fluorine atoms is extracted. Stop the reaction in stages.
  • the method for contacting aluminum fluoride (AlF 3 ) with an alkali metal or alkaline earth metal is not particularly limited as long as the reaction is not allowed to proceed until the aluminum fluoride (AlF 3 ) becomes an aluminum metal. Absent.
  • AlF 3 aluminum fluoride
  • AlF 3 aluminum fluoride
  • Aluminum fluoride (AlF 3 ) and alkali metal or alkaline earth metal are both highly reactive with moisture, so contact in an environment that can avoid contact with moisture in the atmosphere, such as a glove box. It is preferable to implement.
  • the ratio of the alkali metal or alkaline earth metal to be used should be 5 to 20 mol% with respect to the total with aluminum fluoride. preferable. By setting the content to 5 to 20 mol%, a large charge / discharge capacity can be obtained, and at the same time, a fluoride ion secondary battery with reduced reaction overvoltage and increased charge / discharge efficiency can be formed.
  • the ratio of alkali metal or alkaline earth metal is more preferably from 5 to 15 mol%, most preferably from 10 to 15 mol%, based on the total amount with aluminum fluoride.
  • Examples 1 to 6 In Examples 1 to 6, aluminum fluoride (AlF 3 ) was used as modified aluminum fluoride using lithium (Li) metal.
  • the obtained raw material mixed powder was charged into a silicon nitride ball mill container (manufactured by Fritsch, Germany, internal volume: 80 cc, PL-7 exclusive container), and 40 g of silicon nitride balls having a diameter of 2 mm were charged and sealed.
  • the sealed container was rotated at 600 rpm for 15 hours, and a ball mill treatment was performed. After the ball mill treatment, the treated powder was recovered.
  • X-ray photoelectron spectroscopy spectrum The crystal structure of the modified aluminum fluoride obtained in Examples and Comparative Examples was analyzed using XPS (manufactured by ULVAC-PHI, PHI5000 Versa Probe II, Al-K ⁇ radiation source).
  • FIG. 5A shows a Li 1s spectrum
  • FIG. 5B shows an Al 2p spectrum.
  • the amount of lithium (Li) metal is preferably 20 mol% or less.
  • a fluoride ion secondary battery was produced by the following method using the following materials.
  • LBF Solid electrolyte
  • La 0.95 Ba 0.05 F 2.95 (LBF) which is a Tysonite solid electrolyte, was used.
  • LBF is a known compound (see References 7 to 9), and was prepared by the method described in Reference 7.
  • Reference 7 ACS Appl. Mater. Interfaces 2014, 6, 2103-2110
  • Reference 8 J.A. Phys. Chem. C 2013, 117, 4943-4950
  • Reference 9 J.M. Phys. Chem. C 2014, 118, 7117-7129
  • the aluminum fluoride (AlF 3 ) of the modified or comparative example 1 produced in the examples, the solid electrolyte (LBF) for imparting an ion conduction path, and acetylene black (manufactured by Electrochemical Industry) for imparting an electron conduction path ) was weighed at a mass ratio of 10:80:10, and thoroughly mixed using an agate mortar and pestle to obtain a negative electrode mixture powder.
  • a lead foil manufactured by Nilaco Corporation, purity: 99.99%, thickness: 200 um was processed into a diameter of 10 mm and used as a positive electrode.
  • a negative electrode mixture powder (20 mg), a solid electrolyte (400 mg), and a positive electrode prepared as described above are integrally molded at a pressure of 4 ton / cm 2 in a mold having a diameter of 10 mm ⁇ to form a fluoride ion secondary battery.
  • Got the body A gold wire for use as a terminal used for charge / discharge measurement was bonded to the positive / negative electrode surface of the obtained molded body with a carbon paste.
  • the fluoride ion secondary battery using the negative electrode active material of Comparative Example 1 that was not subjected to the modification treatment had a charge / discharge capacity of only several tens mAh / g, whereas the modification was It can be confirmed that the charge / discharge capacity of the fluoride ion secondary battery using the negative electrode active material of the example using aluminum fluoride is greatly increased. Moreover, compared with the fluoride ion secondary battery using the negative electrode active material of Comparative Example 1, the fluoride ion secondary battery using the negative electrode active material of Example has an increase in charge / discharge capacity, reaction All of the fact that the overvoltage is decreasing and the charging / discharging efficiency is increasing can be confirmed.
  • FIG. 7 shows the relationship between the charge / discharge capacity and the lithium (Li) metal blending amount in the AlF 3 reforming process for Examples 1 to 6 and Comparative Example 1. From FIG. 7, it can be confirmed that in the modification treatment of aluminum fluoride (AlF 3 ) according to the present invention, the particularly preferable blending amount of the lithium (Li) metal is 5 to 20 mol%.

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Abstract

Provided are: a negative electrode active material for fluoride ion secondary batteries, which is capable of causing a reversible negative electrode reaction with a high utilization rate in a fluoride ion secondary battery; a negative electrode which uses this active material; a fluoride ion secondary battery; and a method for producing this active material. This negative electrode active material for fluoride ion secondary batteries is composed of a modified aluminum fluoride (AlF3) which is obtained by partially deintercalating a fluoride ion (F-) from aluminum fluoride (AlF3) in advance, thereby modifying such that a vacancy is present in a position where a fluorine atom used to be present.

Description

フッ化物イオン二次電池用負極活物質、当該活物質を用いた負極、およびフッ化物イオン二次電池、並びに当該活物質の製造方法Negative electrode active material for fluoride ion secondary battery, negative electrode using the active material, fluoride ion secondary battery, and method for producing the active material
　本発明は、フッ化物イオン二次電池用負極活物質、当該活物質を用いた負極、およびフッ化物イオン二次電池、並びに当該活物質の製造方法に関する。 The present invention relates to a negative electrode active material for a fluoride ion secondary battery, a negative electrode using the active material, a fluoride ion secondary battery, and a method for producing the active material.
　従来、高エネルギー密度を有する二次電池として、リチウムイオン二次電池が幅広く普及している。リチウムイオン二次電池は、正極と負極との間にセパレータを存在させ、液体の電解質（電解液）が充填された構造を有する。 Conventionally, lithium ion secondary batteries are widely used as secondary batteries having high energy density. A lithium ion secondary battery has a structure in which a separator is present between a positive electrode and a negative electrode and a liquid electrolyte (electrolytic solution) is filled.
　リチウムイオン二次電池の電解液は、通常、可燃性の有機溶媒であるため、特に、熱に対する安全性が問題となる場合があった。そこで、有機系の液体の電解質に代えて、無機系の固体の電解質を用いた固体電池が提案されている（特許文献１参照）。固体電解質による固体電池は、電解液を用いる電池と比較して、熱の問題を解消するとともに、積層により電圧を上昇させることができ、さらに、コンパクト化の要請にも対応することができる。 Since the electrolyte solution of a lithium ion secondary battery is usually a flammable organic solvent, there are cases where safety against heat is particularly problematic. Therefore, a solid battery using an inorganic solid electrolyte instead of an organic liquid electrolyte has been proposed (see Patent Document 1). Compared with a battery using an electrolytic solution, a solid battery using a solid electrolyte can solve the problem of heat, increase the voltage by stacking, and can meet the demand for compactness.
　このような固体電解質による電池として、フッ化物イオン二次電池が検討されている。フッ化物イオン二次電池は、フッ化物イオン（Ｆ－）をキャリアとした二次電池であり、高い理論エネルギーを有することが知られている。そして、その電池特性については、リチウムイオン二次電池を上回る期待がある。 As a battery using such a solid electrolyte, a fluoride ion secondary battery has been studied. The fluoride ion secondary battery is a secondary battery using fluoride ions (F − ) as carriers, and is known to have high theoretical energy. And about the battery characteristic, there exists an expectation exceeding a lithium ion secondary battery.
　ここで、フッ化物イオン二次電池の負極活物質としては、ＭｇＦ２、ＣａＦ２、ＣｅＦ３等が報告されている（非特許文献１および２参照）。しかしながら、現在報告されているこれら負極活物質を用いたフッ化物イオン二次電池は、その充放電効率が１０～２０％であり、２次電池としてのエネルギー効率が低いという問題があった。また、充放電容量についても、理論容量の１０～２０％程度しかなく、現行のＬｉイオン２次電池やＮｉ－ＭＨ電池と比べて高容化が図られていない状況であった。 Here, as the negative electrode active material of the fluoride ion secondary battery, MgF 2, CaF 2, CeF 3 and the like have been reported (see Non-Patent Documents 1 and 2). However, the currently reported fluoride ion secondary batteries using these negative electrode active materials have a problem that their charge / discharge efficiency is 10 to 20%, and energy efficiency as a secondary battery is low. Also, the charge / discharge capacity is only about 10 to 20% of the theoretical capacity, and the capacity has not been increased as compared with the current Li ion secondary battery or Ni-MH battery.
　フッ化物イオン二次電池で使用されている、固体電解質としては、例えば、Ｌａ１－ｘＢａｘＦ３－ｘ、ｘ＝０．０１～０．２（以下ＬＢＦと呼ぶ）が存在している（非特許文献１～４参照）。ＬＢＦの還元側電位窓は、図１に示されるように、ギブスエネルギーから算出されるＬａ／ＬａＦ３の電位である－２．４１Ｖ　ｖｓ．Ｐｂ／ＰｂＦ２で制約を受ける。 Examples of solid electrolytes used in fluoride ion secondary batteries include La 1-x Ba x F 3-x , x = 0.01 to 0.2 (hereinafter referred to as LBF). (See Non-Patent Documents 1 to 4.) As shown in FIG. 1, the reduction-side potential window of LBF is −2.41 V vs. La / LaF 3 potential calculated from Gibbs energy. Subject to constraints in the Pb / PbF 2.
　これに対して、図１に示されるように、現在報告されているフッ化物イオン二次電池の負極活物質の電位は、ＭｇＦ２が、－２．３５～－２．８７Ｖ　ｖｓ．Ｐｂ／ＰｂＦ２、ＣａＦ２が、－２．８５～－２．８９Ｖ　ｖｓ．Ｐｂ／ＰｂＦ２、ＣｅＦ３が、－２．１８～－２．３７Ｖ　ｖｓ．Ｐｂ／ＰｂＦ２である。したがって、ＬＢＦの還元電位窓である－２．４１Ｖの制約下における上記の負極活物質の脱フッ化／再フッ化反応は、その過電圧を考慮すると、提供できないという課題があった。 On the other hand, as shown in FIG. 1, the potential of the negative electrode active material of the fluoride ion secondary battery currently reported is that MgF 2 is −2.35 to −2.87 V vs. Pb / PbF 2 and CaF 2 are in a range of −2.85 to −2.89 V vs. Pb / PbF 2 and CeF 3 are in the range of −2.18 to −2.37 V vs. It is a Pb / PbF 2. Therefore, there has been a problem that the defluorination / refluorination reaction of the negative electrode active material under the restriction of -2.41 V, which is the reduction potential window of LBF, cannot be provided in consideration of the overvoltage.
　一方で、正極反応についてみると、たとえばＣｕ／ＣｕＦ２、Ｂｉ／ＢｉＦ３等の正極活物質は、高い利用率や可逆反応を示す充放電試験の結果が報告されている（非特許文献１～３、および特許文献２参照）。 On the other hand, with regard to the positive electrode reaction, for example, positive electrode active materials such as Cu / CuF 2 and Bi / BiF 3 have been reported to have high utilization rates and charge / discharge test results showing a reversible reaction (Non-Patent Documents 1 to 4). 3 and Patent Document 2).
　したがって、フッ化物イオン二次電池において、正／負極反応を組み合わせた実用的な全電池反応を成立させるためには、可逆的な負極反応を高い利用率で発現する負極活物質材料が必要とされていた。 Therefore, in order to establish a practical all-battery reaction combining positive / negative electrode reactions in a fluoride ion secondary battery, a negative electrode active material that expresses a reversible negative electrode reaction at a high utilization rate is required. It was.
特開２０００－１０６１５４号公報JP 2000-106154 A 特開２０１７－０８８４２７号公報JP 2017-088427 A
　本発明は上記の背景技術に鑑みてなされたものであり、その目的は、フッ化物イオン二次電池において、可逆的な負極反応を高い利用率で発現することのできるフッ化物イオン二次電池用負極活物質、当該活物質を用いた負極、およびフッ化物イオン二次電池、並びに当該活物質の製造方法を提供することにある。 The present invention has been made in view of the above-described background art, and an object of the present invention is for a fluoride ion secondary battery capable of expressing a reversible negative electrode reaction at a high utilization rate in a fluoride ion secondary battery. The object is to provide a negative electrode active material, a negative electrode using the active material, a fluoride ion secondary battery, and a method for producing the active material.
　本発明者は、フッ化物イオン固体電解質であるＬＢＦの電位窓－２．４１Ｖの制約内に充放電反応（脱フッ化／再フッ化反応）が存在するフッ化アルミニウム（ＡｌＦ３：－１．７８Ｖ　ｖｓ．Ｐｂ／ＰｂＦ２）に着目した。フッ化アルミニウム（ＡｌＦ３）は、負極反応の過電圧を０．５Ｖ程度と想定しても、ＬＢＦの還元側電位窓内（－２．４１Ｖ　ｖｓ．Ｐｂ／ＰｂＦ２）に十分な酸化還元電位を有する。 The inventor of the present invention has found that aluminum fluoride (AlF 3 : -1.V) has a charge / discharge reaction (defluorination / refluorination reaction) within the constraint of the potential window of 2.41 V of LBF, which is a fluoride ion solid electrolyte. 78V vs. Pb / PbF2). Aluminum fluoride (AlF 3 ) has a sufficient redox potential within the LBF reduction-side potential window (−2.41 V vs. Pb / PbF 2) even if the overvoltage of the negative electrode reaction is assumed to be about 0.5 V. .
　しかし、フッ化アルミニウム（ＡｌＦ３）は、図２に示すように、イオン的、電子的にほぼ伝導率がゼロの絶縁体であることが知られている（文献５参照）。このため、フッ化アルミニウム（ＡｌＦ３）からのフッ化物イオン（Ｆ－）の脱離および再挿入（本明細書においては、これを脱フッ化／再フッ化反応と称する）を原理とする、負極反応は発現しない。
　　文献５：Ｐｈｙｓ．Ｒｅｖ．Ｂ．６９，０５４１０９（２００４） However, as shown in FIG. 2, aluminum fluoride (AlF 3 ) is known to be an insulator having an ionic and electronic conductivity that is substantially zero (see Document 5). Therefore, the principle is the desorption and reinsertion of fluoride ions (F − ) from aluminum fluoride (AlF 3 ) (in this specification, this is referred to as defluorination / refluorination reaction). Negative electrode reaction does not occur.
Reference 5: Phys. Rev. B. 69,054109 (2004)
　そこで、本発明者は、フッ化アルミニウム（ＡｌＦ３）の結晶構造に着目した。図３に示すように、フッ化アルミニウム（ＡｌＦ３）は、６配位八面体の完全結晶の構造を有する。本発明者は、この結晶構造が、脱フッ化／再フッ化反応を妨げていると考えた。 Therefore, the present inventor has focused on the crystal structure of aluminum fluoride (AlF 3 ). As shown in FIG. 3, aluminum fluoride (AlF 3 ) has a six-coordinate octahedral perfect crystal structure. The inventor considered that this crystal structure hinders the defluorination / refluorination reaction.
　そして、フッ化アルミニウム（ＡｌＦ３）から部分的にフッ化物イオン（Ｆ―）をあらかじめ脱離させ、フッ素原子が存在していた位置に空孔を設けるようフッ化アルミニウム（ＡｌＦ３）を改質すれば、当該空孔が脱フッ化／再フッ化反応の起点となり、所望の負極反応を、高い利用率および可逆性で発現させることができることを見出し、本発明を完成させるに至った。 Then, fluoride ions (F − ) are partially desorbed from aluminum fluoride (AlF 3 ) in advance, and aluminum fluoride (AlF 3 ) is modified so as to provide holes at positions where fluorine atoms existed. Then, the vacancies serve as a starting point for the defluorination / refluorination reaction, and it was found that a desired negative electrode reaction can be expressed with high utilization and reversibility, and the present invention has been completed.
　すなわち本発明は、フッ化物イオンの脱離による空孔を有する改質フッ化アルミニウムである、フッ化物イオン二次電池用負極活物質である。 That is, the present invention is a negative electrode active material for a fluoride ion secondary battery, which is a modified aluminum fluoride having pores due to desorption of fluoride ions.
　前記空孔は、脱フッ化反応および再フッ化反応の起点となっていてもよい。 The vacancies may be the starting point for the defluorination reaction and the refluorination reaction.
　前記空孔は、改質前のフッ化アルミニウムにおいて、フッ素原子が存在していた領域であってもよい。 The holes may be regions where fluorine atoms existed in the aluminum fluoride before modification.
　前記フッ化物イオンの脱離は、フッ化アルミニウムに、アルカリ金属またはアルカリ土類金属を接触させたものであってもよい。 The desorption of fluoride ions may be performed by contacting aluminum fluoride with an alkali metal or an alkaline earth metal.
　また別の本発明は、上記のフッ化物イオン二次電池用負極活物質を含む、フッ化物イオン二次電池用負極である。 Another embodiment of the present invention is a negative electrode for a fluoride ion secondary battery comprising the negative electrode active material for a fluoride ion secondary battery.
　また別の本発明は、上記の記載のフッ化物イオン二次電池用負極と、固体電解質と、正極と、を備えるフッ化物イオン二次電池である。 Another embodiment of the present invention is a fluoride ion secondary battery comprising the above-described negative electrode for a fluoride ion secondary battery, a solid electrolyte, and a positive electrode.
　また別の本発明は、フッ化物イオン二次電池用負極活物質となる改質フッ化アルミニウムを製造する方法であって、フッ化アルミニウムと、アルカリ金属またはアルカリ土類金属とを接触させて、前記フッ化アルミニウムからフッ化物イオンを脱離させることにより、前記フッ化物イオンとして脱離したフッ素原子の存在位置を空孔として改質フッ化アルミニウムとする、フッ化物イオン二次電池用負極活物質の製造方法である。 Another aspect of the present invention is a method for producing a modified aluminum fluoride to be a negative electrode active material for a fluoride ion secondary battery, wherein the aluminum fluoride is brought into contact with an alkali metal or an alkaline earth metal, A negative electrode active material for a fluoride ion secondary battery, in which fluoride ions are desorbed from the aluminum fluoride to form modified aluminum fluoride with the presence of fluorine atoms desorbed as fluoride ions as vacancies It is a manufacturing method.
　上記の製造方法においては、前記アルカリ金属またはアルカリ土類金属はフッ化物となり、前記フッ化アルミニウムは一部のフッ素原子が引き抜かれ、アルミニウム金属にはならないものであってもよい。 In the above manufacturing method, the alkali metal or alkaline earth metal may be a fluoride, and the aluminum fluoride may be one in which some fluorine atoms are extracted and not an aluminum metal.
　前記アルカリ金属または前記アルカリ土類金属の比率は、前記フッ化アルミニウムとの合計に対して５～２０ｍｏｌ％であってもよい。 The ratio of the alkali metal or the alkaline earth metal may be 5 to 20 mol% with respect to the total with the aluminum fluoride.
　前記フッ化アルミニウムは、α－ＡｌＦ３であってもよい。 The aluminum fluoride may be α-AlF 3 .
　前記アルカリ金属は、Ｌｉ金属であってもよい。 The alkali metal may be Li metal.
　本発明のフッ化物イオン二次電池用負極活物質によれば、フッ化物イオン二次電池における可逆的な負極反応を、高い利用率および高い可逆性で発現することができる。また、本発明のフッ化物イオン二次電池用負極活物質によれば、フッ化物イオン二次電池の充放電容量を、大幅に増加することができる。 According to the negative electrode active material for a fluoride ion secondary battery of the present invention, a reversible negative electrode reaction in a fluoride ion secondary battery can be expressed with high utilization and high reversibility. Moreover, according to the negative electrode active material for fluoride ion secondary batteries of the present invention, the charge / discharge capacity of the fluoride ion secondary battery can be significantly increased.
ギブスエネルギーから算出された電位を示す図である。It is a figure which shows the electric potential calculated from the Gibbs energy. フッ化アルミニウムのイオン伝導率および電子状態を示すグラフである。It is a graph which shows the ionic conductivity and electronic state of aluminum fluoride. フッ化アルミニウムの結晶構造を示す図である。It is a figure which shows the crystal structure of aluminum fluoride. 実施例および比較例の改質フッ化アルミニウムのＸＲＤチャートである。It is an XRD chart of the modified aluminum fluoride of an Example and a comparative example. 改質フッ化アルミニウムのＸＰＳスペクトルである。It is an XPS spectrum of modified aluminum fluoride. 実施例および比較例の充放電曲線である。It is a charging / discharging curve of an Example and a comparative example. 実施例および比較例の充放電容量とリチウム（Ｌｉ）金属配合量との関係を示すグラフである。It is a graph which shows the relationship between the charging / discharging capacity | capacitance of an Example and a comparative example, and a lithium (Li) metal compounding quantity.
　以下、本発明の実施形態について説明する。 Hereinafter, embodiments of the present invention will be described.
　＜フッ化物イオン二次電池用負極活物質＞
　フッ化物イオン二次電池の負極は、放電時にフッ化物イオン（Ｆ－）を収容し、充電時にフッ化物イオン（Ｆ－）を放出可能なものである必要がある。 <Negative electrode active material for fluoride ion secondary battery>
The negative electrode of the fluoride ion secondary battery, fluoride ions during discharge (F -) accommodates, fluoride ions during charging - should those capable of releasing (F).
　本発明のフッ化物イオン二次電池用負極活物質は、フッ化物イオンの脱離による空孔を有する改質フッ化アルミニウムである。 The negative electrode active material for a fluoride ion secondary battery of the present invention is a modified aluminum fluoride having pores due to desorption of fluoride ions.
　上記した通り、フッ化アルミニウム（ＡｌＦ３）は、図２に示すように、イオン的、電子的にほぼ伝導率がゼロの絶縁体であるため、フッ化アルミニウム（ＡｌＦ３）からのフッ化物イオン（Ｆ－）の脱離および再挿入（脱フッ化／再フッ化反応）による負極反応は進行しない。このため、従来、フッ化アルミニウム（ＡｌＦ３）の単体を活物質として用いた先行例は、リチウムイオン電池用正極活物質としては報告されているが（文献６参照）、フッ化物イオン（Ｆ－）をキャリアとしたフッ化物イオン二次電池では報告されていない。
　　文献６：Ｊ．Ａｐｐｌ　Ｅｌｅｃｔｒｏｃｈｅｍ（２０１７）４７　４１７－４３１ As described above, since aluminum fluoride (AlF 3 ) is an insulator having substantially zero conductivity in terms of ions and electrons as shown in FIG. 2, fluoride ions from aluminum fluoride (AlF 3 ). The negative electrode reaction due to (F − ) desorption and reinsertion (defluorination / refluorination reaction) does not proceed. For this reason, a prior example using aluminum fluoride (AlF 3 ) alone as an active material has been reported as a positive electrode active material for lithium ion batteries (see Reference 6), but fluoride ions (F− ) Has not been reported for fluoride ion secondary batteries.
Reference 6: J.A. Appl Electrochem (2017) 47 417-431
　［空孔］
　本発明のフッ化物イオン二次電池用負極活物質となる改質フッ化アルミニウムは、フッ化物イオン（Ｆ－）の脱離により、フッ化アルミニウム（ＡｌＦ３）に空孔を有する。 [Vacancy]
The modified aluminum fluoride serving as the negative electrode active material for the fluoride ion secondary battery of the present invention has pores in the aluminum fluoride (AlF 3 ) due to the elimination of fluoride ions (F−).
　改質フッ化アルミニウムが有する空孔は、脱フッ化反応および再フッ化反応の起点となる。すなわち、空孔が存在することにより、イオン的、電子的にほぼ伝導率がゼロの絶縁体であったフッ化アルミニウム（ＡｌＦ３）が改質され、高い利用率、および高い可逆性で、負極反応が進行するようになる。 The pores of the modified aluminum fluoride serve as starting points for the defluorination reaction and the refluorination reaction. That is, the presence of vacancies modifies aluminum fluoride (AlF 3 ), which is an ionic and electronically non-conductive insulator, and has high utilization and high reversibility. The reaction proceeds.
　図３は、フッ化アルミニウム（ＡｌＦ３）の結晶構造のひとつであるα－ＡｌＦ３の構造を示す図である。図３に示されるように、結晶構造の構成単位となるフッ化アルミニウム（ＡｌＦ３）の構造は、Ａｌ原子１が中心に配置され、頂点が６つのフッ素原子２で構成される６配位八面体である。 FIG. 3 is a diagram showing the structure of α-AlF 3 which is one of the crystal structures of aluminum fluoride (AlF 3 ). As shown in FIG. 3, the structure of aluminum fluoride (AlF 3 ) serving as a structural unit of the crystal structure is a six-coordinate eight structure in which an Al atom 1 is arranged at the center and a vertex is composed of six fluorine atoms 2. It is a face.
　空孔は、原料となる改質前のフッ化アルミニウム（ＡｌＦ３）において、フッ素原子が存在していた領域に形成される。すなわち、図３に示される、Ａｌ原子１が中心に配置され、頂点に存在する６つのフッ素原子２のうち、一部のフッ素原子２が引き抜かれ、引き抜かれて脱離したフッ素原子２が存在していた位置が、空孔となる。 The vacancies are formed in a region where fluorine atoms existed in the unmodified aluminum fluoride (AlF 3 ) used as a raw material. That is, as shown in FIG. 3, Al atom 1 is arranged at the center, and among the six fluorine atoms 2 existing at the apex, some fluorine atoms 2 are extracted, and there are fluorine atoms 2 that are extracted and desorbed. The position where it has become a hole.
　なお、本発明の改質フッ化アルミニウムは、フッ化アルミニウム（ＡｌＦ３）において、６つのフッ素原子の全てが脱離するのではなく、すなわち、フッ化アルミニウム（ＡｌＦ３）はアルミニウム金属にはならず、一部のフッ素原子のみが引き抜かれたものである。 Incidentally, it modified aluminum fluoride of the present invention, in the aluminum fluoride (AlF 3), instead of all six fluorine atoms are eliminated, i.e., aluminum fluoride (AlF 3) is not in the aluminum metal In other words, only some of the fluorine atoms are extracted.
　＜フッ化物イオン二次電池用負極＞
　本発明のフッ化物イオン二次電池用負極は、本発明のフッ化物イオン二次電池用負極活物質を含むことを特徴とする。本発明のフッ化物イオン二次電池用負極活物質を含んでいれば、その他の構成は特に限定されるものではない。 <Negative electrode for fluoride ion secondary battery>
The negative electrode for a fluoride ion secondary battery of the present invention includes the negative electrode active material for a fluoride ion secondary battery of the present invention. If the negative electrode active material for fluoride ion secondary batteries of this invention is included, another structure will not be specifically limited.
　フッ化物イオン二次電池の電気化学反応効率を高めるためには、負極を構成する材料の表面積を拡大することが有効である。そこで、本発明のフッ化物イオン二次電池用負極は、多孔質構造等、その表面積が高い構造として、固体電解質との接触面積を増加させる構造を有することが好ましい。 In order to increase the electrochemical reaction efficiency of the fluoride ion secondary battery, it is effective to increase the surface area of the material constituting the negative electrode. Therefore, the negative electrode for a fluoride ion secondary battery of the present invention preferably has a structure that increases the contact area with the solid electrolyte as a structure having a high surface area such as a porous structure.
　また、本発明のフッ化物イオン二次電池用負極は、本発明のフッ化物イオン二次電池用負極活物質以外に、他の成分を含んでいてもよい。他の成分としては、例えば、導電助剤やバインダー等が挙げられる。 Moreover, the negative electrode for fluoride ion secondary batteries of the present invention may contain other components in addition to the negative electrode active material for fluoride ion secondary batteries of the present invention. Examples of other components include a conductive aid and a binder.
　本発明のフッ化物イオン二次電池用負極は、例えば、本発明のフッ化物イオン二次電池用負極活物質と、導電助剤と、バインダーとを含む混合物を、集電体上に塗布して乾燥することにより得ることができる。 The negative electrode for a fluoride ion secondary battery of the present invention is obtained, for example, by applying a mixture containing the negative electrode active material for a fluoride ion secondary battery of the present invention, a conductive additive, and a binder onto a current collector. It can be obtained by drying.
　＜フッ化物イオン二次電池＞
　本発明のフッ化物イオン二次電池は、本発明のフッ化物イオン二次電池用負極活物質を含むフッ化物イオン二次電池用負極と、固体電解質と、正極と、を備える。本発明のフッ化物イオン二次電池は、本発明のフッ化物イオン二次電池用負極活物質を含む負極を用いていれば、その他の構成は特に限定されるものではない。 <Fluoride ion secondary battery>
The fluoride ion secondary battery of the present invention includes a negative electrode for a fluoride ion secondary battery containing the negative electrode active material for a fluoride ion secondary battery of the present invention, a solid electrolyte, and a positive electrode. If the negative electrode containing the negative electrode active material for fluoride ion secondary batteries of this invention is used for the fluoride ion secondary battery of this invention, another structure will not be specifically limited.
　本発明においては、本発明のフッ化物イオン二次電池用負極活物質を含むフッ化物イオン二次電池用負極の標準電極電位に対して、十分に高い標準電極電位を提供する正極材料を選択することにより、フッ化物イオン二次電池としての特性が高く、また、所望の電池電圧を実現することが可能となる。 In the present invention, a positive electrode material that provides a sufficiently high standard electrode potential with respect to the standard electrode potential of the negative electrode for a fluoride ion secondary battery including the negative electrode active material for a fluoride ion secondary battery of the present invention is selected. Thus, the characteristics as a fluoride ion secondary battery are high, and a desired battery voltage can be realized.
　＜フッ化物イオン二次電池用負極活物質の製造方法＞
　本発明のフッ化物イオン二次電池用負極活物質となる改質フッ化アルミニウムの製造方法は、フッ化アルミニウムと、アルカリ金属またはアルカリ土類金属とを接触させて、前記フッ化アルミニウムからフッ化物イオンを脱離させることにより、前記フッ化物イオンとして脱離したフッ素原子の存在位置を空孔として、フッ化アルミニウムを改質する。 <Method for producing negative electrode active material for fluoride ion secondary battery>
The method for producing a modified aluminum fluoride serving as a negative electrode active material for a fluoride ion secondary battery according to the present invention comprises contacting aluminum fluoride with an alkali metal or alkaline earth metal, and then converting the aluminum fluoride into a fluoride. By desorbing the ions, the aluminum fluoride is modified using the positions of the fluorine atoms desorbed as fluoride ions as vacancies.
　［改質前のフッ化アルミニウム（ＡｌＦ３）］
　フッ化アルミニウム（ＡｌＦ３）には、様々な結晶構造が存在する。結晶構造としては、例えば、α－ＡｌＦ３、β－ＡｌＦ３、θ－ＡｌＦ３、等が挙げられる。しかしながら、いずれの結晶構造においても、その構成単位は同一の構造である。 [Aluminum fluoride before modification (AlF 3 )]
Aluminum fluoride (AlF 3 ) has various crystal structures. Examples of the crystal structure include α-AlF 3 , β-AlF 3 , θ-AlF 3 , and the like. However, in any crystal structure, the structural unit is the same structure.
　具体的には、フッ化アルミニウム（ＡｌＦ３）の結晶構造のひとつであるα－ＡｌＦ３の構造を示す図３に示されるように、結晶構造の構成単位となるフッ化アルミニウム（ＡｌＦ３）の構造は、Ａｌ原子が中心に配置され、頂点が６つのフッ素原子で構成される６配位八面体である。 Specifically, as shown in FIG. 3 showing the structure of a is alpha-AlF 3 single crystal structure of aluminum fluoride (AlF 3), aluminum fluoride as the constituent unit of the crystal structure (AlF 3) The structure is a six-coordinate octahedron in which an Al atom is arranged at the center and a vertex is composed of six fluorine atoms.
　本発明においては、原料として用いるフッ化アルミニウム（ＡｌＦ３）の構造は、特に限定されるものではなく、いずれの結晶構造のフッ化アルミニウム（ＡｌＦ３）も用いることができる。フッ化アルミニウム（ＡｌＦ３）の中では、入手が容易で最も安価な観点から、α－ＡｌＦ３を用いることが好ましい。α－ＡｌＦ３の市販品としては、例えば、シグマアルドリッチ社製ＡｌＦ３（純度９９．９％）や、Ａｌｆａ　Ａｅｓａｒ社製ＡｌＦ３（純度９９．９％）等を挙げることができる。 In the present invention, the structure of the aluminum fluoride used as a starting material (AlF 3) is not limited particularly, aluminum fluoride of any crystal structure (AlF 3) may also be used. Of the aluminum fluorides (AlF 3 ), α-AlF 3 is preferably used from the viewpoint of availability and the lowest cost. Examples of commercially available alpha-AlF 3, for example, can be cited and Sigma-Aldrich AlF 3 (purity 99.9%), Alfa Aesar Co. AlF 3 (purity 99.9%), and the like.
　なお、フッ化アルミニウム（ＡｌＦ３）は、大気中の水分を吸湿し、より安定な０．５水和物もしくは３水和物を形成する。このため、脱水処理をおこなったフッ化アルミニウム（ＡｌＦ３）を用いることが、さらに好ましい。脱水処理の方法としては、例えば、２５０～３００℃程度の温度で、真空焼成する方法等が挙げられる。 Aluminum fluoride (AlF 3 ) absorbs moisture in the air and forms a more stable 0.5 hydrate or trihydrate. For this reason, it is more preferable to use aluminum fluoride (AlF 3 ) that has been subjected to dehydration treatment. Examples of the dehydration method include a vacuum baking method at a temperature of about 250 to 300 ° C.
　［アルカリ金属またはアルカリ土類金属］
　本発明のフッ化物イオン二次電池用負極活物質を製造するために用いるアルカリ金属またはアルカリ土類金属は、特に限定されるものではない。アルカリ金属としては、例えば、リチウム（Ｌｉ）、ナトリウム（Ｎａ）、カリウム（Ｋ）、ルビジウム（Ｒｂ）、セシウム（Ｃｓ）、等を挙げることができ、アルカリ土類金属としては、例えば、マグネシウム（Ｍｇ）、カルシウム（Ｃａ）、ストロンチウム（Ｓｒ）、バリウム（Ｂａ）、等を挙げることができる。 [Alkali metal or alkaline earth metal]
The alkali metal or alkaline earth metal used for producing the negative electrode active material for fluoride ion secondary batteries of the present invention is not particularly limited. Examples of the alkali metal include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). Examples of the alkaline earth metal include magnesium ( Mg), calcium (Ca), strontium (Sr), barium (Ba), and the like.
　本発明のフッ化物イオン二次電池用負極活物質の製造方法においては、アルカリ金属またはアルカリ土類金属の中でも、リチウム（Ｌｉ）金属を用いることが好ましい。リチウム（Ｌｉ）金属は、全ての金属元素の中で最も軽いため、フッ化アルミニウムと混合した後の活物質重量あたりの容量（ｍＡｈ／ｇ）を高く維持することができる。 In the method for producing a negative electrode active material for a fluoride ion secondary battery of the present invention, it is preferable to use lithium (Li) metal among alkali metals or alkaline earth metals. Since lithium (Li) metal is the lightest of all the metal elements, the capacity per active material weight (mAh / g) after mixing with aluminum fluoride can be kept high.
　市販のリチウム（Ｌｉ）金属としては、例えば、本城金属社製Ｌｉ箔（純度９９．８％）等が挙げられる。リチウム（Ｌｉ）金属の形状は、特に制限されるものではないが、フッ化アルミニウム（ＡｌＦ３）との混合が容易となる観点から、チップ状、またはビーズ状であることが好ましい。 As a commercially available lithium (Li) metal, for example, Honjo Metal Co., Ltd. Li foil (purity 99.8%) etc. are mentioned. The shape of the lithium (Li) metal is not particularly limited, but is preferably a chip shape or a bead shape from the viewpoint of easy mixing with aluminum fluoride (AlF 3 ).
　［フッ化アルミニウム（ＡｌＦ３）と、アルカリ金属またはアルカリ土類金属との接触］
　本発明のフッ化物イオン二次電池用負極活物質の製造方法は、上記のフッ化アルミニウム（ＡｌＦ３）と、上記のアルカリ金属またはアルカリ土類金属とを接触させて、改質フッ化アルミニウムを得るものである。 [Contact between aluminum fluoride (AlF 3 ) and alkali metal or alkaline earth metal]
In the method for producing a negative electrode active material for a fluoride ion secondary battery according to the present invention, the above aluminum fluoride (AlF 3 ) and the above alkali metal or alkaline earth metal are brought into contact with each other, and the modified aluminum fluoride is obtained. To get.
　フッ化アルミニウム（ＡｌＦ３）と、アルカリ金属またはアルカリ土類金属とを接触させることにより、フッ化アルミニウムからフッ化物イオンを脱離させ、フッ化物イオンとして脱離したフッ素原子の存在位置を空孔として、改質フッ化アルミニウムを得る。 By bringing aluminum fluoride (AlF 3 ) into contact with an alkali metal or alkaline earth metal, fluoride ions are desorbed from the aluminum fluoride, and the positions of fluorine atoms desorbed as fluoride ions are vacant. As a result, modified aluminum fluoride is obtained.
　（反応機構）
　フッ化アルミニウム（ＡｌＦ３）の脱フッ化／再フッ化反応電位に対して、より卑な電位を示すアルカリ金属またはアルカリ土類金属を接触させることにより、アルカリ金属またはアルカリ土類金属はフッ化物を形成し、フッ化アルミニウム（ＡｌＦ３）からは一部のフッ素原子が引き抜かれる反応が起こる。このような卑金属との接触によるフッ化物からの部分的なフッ素原子の引き抜きは、先行例として確認されていない。 (Reaction mechanism)
By contacting an alkali metal or alkaline earth metal having a lower potential with the defluorination / refluorination reaction potential of aluminum fluoride (AlF 3 ), the alkali metal or alkaline earth metal is converted to fluoride. And a reaction in which some fluorine atoms are extracted from aluminum fluoride (AlF 3 ) occurs. Such partial extraction of fluorine atoms from fluoride due to contact with a base metal has not been confirmed as a prior example.
　なお、本発明のフッ化物イオン二次電池用負極活物質の製造方法は、フッ化アルミニウム（ＡｌＦ３）における、６つのフッ素原子の全てを脱離させるものではない。すなわち、一部のフッ素原子のみを引き抜き、フッ化アルミニウム（ＡｌＦ３）がアルミニウム金属となるまで反応はさせない。 The manufacturing method of the negative electrode active material for fluoride ion secondary battery of the present invention, the aluminum fluoride (AlF 3), does not desorb all six fluorine atoms. That is, only some of the fluorine atoms are extracted, and the reaction is not performed until aluminum fluoride (AlF 3 ) becomes an aluminum metal.
　フッ化アルミニウム（ＡｌＦ３）と、アルカリ金属またはアルカリ土類金属とを接触させたときの反応の例を、以下に示す。以下は、アルカリ金属であるリチウム（Ｌｉ）金属とフッ化アルミニウム（ＡｌＦ３）との反応である。 An example of a reaction when aluminum fluoride (AlF 3 ) is brought into contact with an alkali metal or an alkaline earth metal is shown below. The following is a reaction between lithium (Li) metal, which is an alkali metal, and aluminum fluoride (AlF 3 ).
　　ｘＬｉ　＋　（１－ｘ）ＡｌＦ３
　　（１）　→　ｘＬｉＦ　＋　（１－ｘ）ＡｌＦ３－４Ｘ／（１－Ｘ）
　　（２）　→　ｘＬｉＦ　＋　（１－４ｘ/３）ＡｌＦ３　＋　（ｘ/３）Ａｌ
　　（３）　→　（ｘ/３）Ｌｉ３ＡｌＦ６　＋　（１－５ｘ/３）ＡｌＦ３　＋　（ｘ/３）Ａｌ xLi + (1-x) AlF 3
(1) → xLiF + (1-x) AlF 3-4X / (1-X)
(2) → xLiF + (1-4x / 3) AlF 3 + (x / 3) Al
(3) → (x / 3) Li 3 AlF 6 + (1-5x / 3) AlF 3 + (x / 3) Al
　本発明においては、フッ化アルミニウム（ＡｌＦ３）がアルミニウム金属となる式（２）および式（３）の段階までは反応を進めず、一部のフッ素原子のみが引き抜かれた式（１）の段階で、反応をとどめる。 In the present invention, the reaction does not proceed to the stage of formula (2) and formula (3) in which aluminum fluoride (AlF 3 ) becomes an aluminum metal, and only a part of fluorine atoms is extracted. Stop the reaction in stages.
　（接触方法）
　フッ化アルミニウム（ＡｌＦ３）と、アルカリ金属またはアルカリ土類金属との接触方法は、フッ化アルミニウム（ＡｌＦ３）がアルミニウム金属となるまで反応を進めさせない方法であれば、特に限定されるものではない。 (Contact method)
The method for contacting aluminum fluoride (AlF 3 ) with an alkali metal or alkaline earth metal is not particularly limited as long as the reaction is not allowed to proceed until the aluminum fluoride (AlF 3 ) becomes an aluminum metal. Absent.
　例えば、必要量のフッ化アルミニウム（ＡｌＦ３）と、アルカリ金属またはアルカリ土類金属とをそれぞれ秤量し、必要に応じて予備混合を実施し、ボールミル等によって混合処理する方法が挙げられる。 For example, there is a method in which a necessary amount of aluminum fluoride (AlF 3 ) and an alkali metal or an alkaline earth metal are weighed, premixed as necessary, and mixed by a ball mill or the like.
　なお、フッ化アルミニウム（ＡｌＦ３）と、アルカリ金属またはアルカリ土類金属は、いずれも水分との反応が極めて高いため、グローブボックス等、大気中の水分との接触を回避できる環境にて、接触を実施することが好ましい。 Aluminum fluoride (AlF 3 ) and alkali metal or alkaline earth metal are both highly reactive with moisture, so contact in an environment that can avoid contact with moisture in the atmosphere, such as a glove box. It is preferable to implement.
　（反応組成）
　また、本発明のフッ化物イオン二次電池用負極活物質の製造方法においては、用いるアルカリ金属またはアルカリ土類金属の比率は、フッ化アルミニウムとの合計に対して５～２０ｍｏｌ％とすることが好ましい。５～２０ｍｏｌ％とすることにより、大きな充放電容量が得られ、同時に、反応過電圧が減少し、充放電効率が増加したフッ化物イオン二次電池を形成することができる。アルカリ金属またはアルカリ土類金属の比率は、フッ化アルミニウムとの合計に対して５～１５ｍｏｌ％とすることがさらに好ましく、１０～１５ｍｏｌ％とすることが最も好ましい。 (Reaction composition)
In the method for producing a negative electrode active material for a fluoride ion secondary battery of the present invention, the ratio of the alkali metal or alkaline earth metal to be used should be 5 to 20 mol% with respect to the total with aluminum fluoride. preferable. By setting the content to 5 to 20 mol%, a large charge / discharge capacity can be obtained, and at the same time, a fluoride ion secondary battery with reduced reaction overvoltage and increased charge / discharge efficiency can be formed. The ratio of alkali metal or alkaline earth metal is more preferably from 5 to 15 mol%, most preferably from 10 to 15 mol%, based on the total amount with aluminum fluoride.
　次に、本発明の実施例について説明するが、本発明はこれら実施例に限定されるものではない。 Next, examples of the present invention will be described, but the present invention is not limited to these examples.
　＜実施例１～６＞
　実施例１～６においては、リチウム（Ｌｉ）金属を用いて、フッ化アルミニウム（ＡｌＦ３）を改質フッ化アルミニウムとした。 <Examples 1 to 6>
In Examples 1 to 6, aluminum fluoride (AlF 3 ) was used as modified aluminum fluoride using lithium (Li) metal.
　［改質フッ化アルミニウムの製造］
　（原料の秤量・予備混合）
　フッ化アルミニウム（ＡｌＦ３）、およびリチウム（Ｌｉ）金属を、表１に示すモル比率で、全量が６．０グラムになるよう秤量し、メノウ製の乳鉢と乳棒を用いて、約１時間、予備混合して、原料混合粉末を得た。 [Production of modified aluminum fluoride]
(Weighing raw materials / preliminary mixing)
Aluminum fluoride (AlF 3 ) and lithium (Li) metal were weighed in a molar ratio shown in Table 1 so that the total amount was 6.0 grams, and using an agate mortar and pestle for about 1 hour, Premixing was performed to obtain a raw material mixed powder.
　なお、フッ化アルミニウム（ＡｌＦ３）、およびリチウム（Ｌｉ）金属はいずれも、水分との反応性が極めて高いため、原料の秤量および予備混合は、グローブボックス（（株）美和製作所製、型式ＤＢＯ－１．５ＢＮＫ－ＳＱ１）内にて実施した。 In addition, since aluminum fluoride (AlF 3 ) and lithium (Li) metal are both extremely reactive with moisture, the raw material is weighed and pre-mixed by glove box (Miwa Seisakusho, Model DBO). -1.5BNK-SQ1).
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　（接触処理）
　得られた原料混合粉末を、窒化ケイ素製ボールミル容器（独フリッチュ社製、内容積：８０ｃｃ、ＰＬ－７専用容器）に投入し、直径２ｍｍの窒化ケイ素製ボールを４０グラム投入し、密封した。 (Contact processing)
The obtained raw material mixed powder was charged into a silicon nitride ball mill container (manufactured by Fritsch, Germany, internal volume: 80 cc, PL-7 exclusive container), and 40 g of silicon nitride balls having a diameter of 2 mm were charged and sealed.
　引き続き、密封した容器を、回転数６００ｒｐｍで１５時間回転させ、ボールミル処理を実施した。ボールミル処理の後、処理された粉末を回収した。 Subsequently, the sealed container was rotated at 600 rpm for 15 hours, and a ball mill treatment was performed. After the ball mill treatment, the treated powder was recovered.
　＜比較例１＞
　リチウム（Ｌｉ）金属を用いず、フッ化アルミニウム（ＡｌＦ３）のみを用いて、実施例と同様の操作を実施し、ボールミル処理された粉末を得た。 <Comparative Example 1>
The same operation as in the example was performed using only aluminum fluoride (AlF 3 ) without using lithium (Li) metal to obtain a ball milled powder.
　＜改質フッ化アルミニウムの評価＞
　［Ｘ線回折パターン］
　ＸＲＤ（リガク社製、ＳｍａｒｔＬａＢ、Ｃｕ－Ｋα線源、λ＝１．５４１８Å）を用いて、実施例および比較例で得られた改質フッ化アルミニウムの結晶構造を解析した。ＸＲＤチャートを、図４に示す。 <Evaluation of modified aluminum fluoride>
[X-ray diffraction pattern]
Using XRD (manufactured by Rigaku Corporation, SmartLaB, Cu—Kα radiation source, λ = 1.5418 mm), the crystal structures of the modified aluminum fluoride obtained in the examples and comparative examples were analyzed. An XRD chart is shown in FIG.
　［Ｘ線光電子分光スペクトル］
　Ｘ線光電子分光：ＸＰＳ（アルバックファイ社製、ＰＨＩ５０００　Ｖｅｒｓａ　ＰｒｏｂｅII、Ａｌ－Ｋα線源）を用いて、実施例および比較例で得られた改質フッ化アルミニウムの結晶構造を解析した。図５（ａ）に、Ｌｉ　１ｓスペクトルを、図５（ｂ）に、Ａｌ　２ｐスペクトルを示す。 [X-ray photoelectron spectroscopy spectrum]
X-ray photoelectron spectroscopy: The crystal structure of the modified aluminum fluoride obtained in Examples and Comparative Examples was analyzed using XPS (manufactured by ULVAC-PHI, PHI5000 Versa Probe II, Al-Kα radiation source). FIG. 5A shows a Li 1s spectrum, and FIG. 5B shows an Al 2p spectrum.
　［評価］
　図４のＸＲＤチャートより、リチウム（Ｌｉ）金属が５．０ｍｏｌ％～２０ｍｏｌ％である実施例１～４の回折ピーク位置は、リチウム（Ｌｉ）金属を用いなかった比較例１（ＡｌＦ３のみ）の回折ピーク位置と同一であり、結晶構造の変化は認められなかった。 [Evaluation]
From the XRD chart of FIG. 4, the diffraction peak positions of Examples 1 to 4 in which the lithium (Li) metal is 5.0 mol% to 20 mol% are Comparative Example 1 in which no lithium (Li) metal was used (only AlF 3 ). No change in crystal structure was observed.
　一方で、リチウム（Ｌｉ）金属が３０ｍｏｌ％以上の実施例５および６では、アルミニウム（Ａｌ）金属、ＬｉＦ、Ｌｉ３ＡｌＦ６に帰属するピークが確認された。すなわち、リチウム（Ｌｉ）金属を３０ｍｏｌ％以上とした範囲では、Ｌｉ３ＡｌＦ６が存在していることから、上記した式（３）まで、反応が進んでいることとなる。 On the other hand, in Examples 5 and 6 in which the lithium (Li) metal was 30 mol% or more, peaks attributable to aluminum (Al) metal, LiF, and Li 3 AlF 6 were confirmed. That is, in the range where the lithium (Li) metal is 30 mol% or more, Li 3 AlF 6 exists, and thus the reaction proceeds to the above-described formula (3).
　また、図５（ａ）に示されるＬｉ　１ｓスペクトルより、全ての実施例において、ＬｉＦの生成が確認され、図５（ｂ）に示されるＡｌ　２ｐスペクトルより、リチウム（Ｌｉ）金属が３０ｍｏｌ％以上の実施例５および６では、Ａｌ金属の生成が認められた。すなわち、上記した式（２）まで、反応が進んでいることとなる。 Moreover, in all Examples, the production | generation of LiF was confirmed from the Li1s spectrum shown by Fig.5 (a), and lithium (Li) metal is 30 mol% or more from the Al2p spectrum shown by FIG.5 (b). In Examples 5 and 6, production of Al metal was observed. That is, the reaction has progressed to the above formula (2).
　Ｘ線回折パターンおよびＸ線光電子分光スペクトルより、上記した式（１）までで反応をとどめるためには、リチウム（Ｌｉ）金属の配合量は、２０ｍｏｌ％以下とすることが好ましい。 From the X-ray diffraction pattern and the X-ray photoelectron spectrum, in order to stop the reaction up to the above formula (1), the amount of lithium (Li) metal is preferably 20 mol% or less.
　＜フッ化物イオン二次電池の作製＞
　以下の材料を用いて、以下の方法で、フッ化物イオン二次電池を作製した。 <Production of fluoride ion secondary battery>
A fluoride ion secondary battery was produced by the following method using the following materials.
　（固体電解質）
　タイソナイト系の固体電解質であるＬａ０．９５Ｂａ０．０５Ｆ２．９５（ＬＢＦ）を用いた。ＬＢＦは公知の化合物（文献７～９参照）であり、文献７に記載された方法にて作製した。
　　文献７：ＡＣＳ　Ａｐｐｌ．Ｍａｔｅｒ．Ｉｎｔｅｒｆａｃｅｓ　２０１４，６，２１０３－２１１０
　　文献８：Ｊ．Ｐｈｙｓ．Ｃｈｅｍ．Ｃ　２０１３，１１７，４９４３－４９５０
　　文献９：Ｊ．Ｐｈｙｓ．Ｃｈｅｍ．Ｃ　２０１４，１１８，７１１７－７１２９ (Solid electrolyte)
La 0.95 Ba 0.05 F 2.95 (LBF), which is a Tysonite solid electrolyte, was used. LBF is a known compound (see References 7 to 9), and was prepared by the method described in Reference 7.
Reference 7: ACS Appl. Mater. Interfaces 2014, 6, 2103-2110
Reference 8: J.A. Phys. Chem. C 2013, 117, 4943-4950
Reference 9: J.M. Phys. Chem. C 2014, 118, 7117-7129
　（負極合剤粉末）
　実施例で作製した改質または比較例１のフッ化アルミニウム（ＡｌＦ３）、イオン伝導経路を付与するための固体電解質（ＬＢＦ）、および電子伝導経路を付与するためのアセチレンブラック（電気化学工業製）を、１０：８０：１０の質量比で秤量し、メノウ製の乳鉢と乳棒を用いて十分に混合し、負極合剤粉末とした。 (Negative electrode mixture powder)
The aluminum fluoride (AlF 3 ) of the modified or comparative example 1 produced in the examples, the solid electrolyte (LBF) for imparting an ion conduction path, and acetylene black (manufactured by Electrochemical Industry) for imparting an electron conduction path ) Was weighed at a mass ratio of 10:80:10, and thoroughly mixed using an agate mortar and pestle to obtain a negative electrode mixture powder.
　（正極）
　鉛箔（（株）ニラコ製、純度：９９．９９％、厚さ：２００ｕｍ）を、直径１０ｍｍに加工し、正極として用いた。 (Positive electrode)
A lead foil (manufactured by Nilaco Corporation, purity: 99.99%, thickness: 200 um) was processed into a diameter of 10 mm and used as a positive electrode.
　（フッ化物イオン二次電池）
　上記のように準備した負極合剤粉末（２０ｍｇ）、固体電解質（４００ｍｇ）、正極を、直径１０ｍｍΦの金型中で４ｔｏｎ／ｃｍ２の圧力で一体成形し、フッ化物イオン二次電池となる成型体を得た。得られた成型体の正／負極面に、カーボンペーストにより、充放電測定に使用する端子として用いるための金線を接着した。 (Fluoride ion secondary battery)
A negative electrode mixture powder (20 mg), a solid electrolyte (400 mg), and a positive electrode prepared as described above are integrally molded at a pressure of 4 ton / cm 2 in a mold having a diameter of 10 mmΦ to form a fluoride ion secondary battery. Got the body. A gold wire for use as a terminal used for charge / discharge measurement was bonded to the positive / negative electrode surface of the obtained molded body with a carbon paste.
　＜フッ化物イオン二次電池の評価＞
　（定電流充放電試験）
　ポテンショガルバノスタット装置（ソーラトロン社、ＳＩ１２８７／１２５５Ｂ）を用いて、充電０．０２ｍＡ、放電０．０１ｍＡの電流にて、下限電圧－２．３５Ｖ、上限電圧－０．１Ｖ、にて、定電流充放電試験を実施した。充放電曲線を、図６に示す。 <Evaluation of fluoride ion secondary battery>
(Constant current charge / discharge test)
Using a potentiogalvanostat (Solartron, SI1287 / 12255B), charging at constant current at a lower limit voltage of -2.35 V and an upper limit voltage of -0.1 V at a current of 0.02 mA charge and 0.01 mA discharge. A discharge test was performed. A charge / discharge curve is shown in FIG.
　図６より、改質処理を行っていない比較例１の負極活物質を用いたフッ化物イオン二次電池は、充放電容量が数十ｍＡｈ／ｇしか得られなかったのに対して、改質フッ化アルミニウムを用いた実施例の負極活物質を用いたフッ化物イオン二次電池は、充放電容量が大幅に増加していることが確認できる。また、比較例１の負極活物質を用いたフッ化物イオン二次電池と比べて、実施例の負極活物質を用いたフッ化物イオン二次電池は、充放電容量が増加していること、反応過電圧が減少していること、充放電効率が増加していること、の全てについて確認できる。 From FIG. 6, the fluoride ion secondary battery using the negative electrode active material of Comparative Example 1 that was not subjected to the modification treatment had a charge / discharge capacity of only several tens mAh / g, whereas the modification was It can be confirmed that the charge / discharge capacity of the fluoride ion secondary battery using the negative electrode active material of the example using aluminum fluoride is greatly increased. Moreover, compared with the fluoride ion secondary battery using the negative electrode active material of Comparative Example 1, the fluoride ion secondary battery using the negative electrode active material of Example has an increase in charge / discharge capacity, reaction All of the fact that the overvoltage is decreasing and the charging / discharging efficiency is increasing can be confirmed.
　（充放電容量とリチウム（Ｌｉ）金属配合量との関係）
　実施例１～６、および比較例１について、充放電容量とＡｌＦ３改質処理におけるリチウム（Ｌｉ）金属配合量との関係を、図７に示す。図７より、本発明のフッ化アルミニウム（ＡｌＦ３）の改質処理において、特に良好なチウム（Ｌｉ）金属の配合量は、５～２０ｍｏｌ％であることが確認できる。 (Relationship between charge / discharge capacity and lithium (Li) metal content)
FIG. 7 shows the relationship between the charge / discharge capacity and the lithium (Li) metal blending amount in the AlF 3 reforming process for Examples 1 to 6 and Comparative Example 1. From FIG. 7, it can be confirmed that in the modification treatment of aluminum fluoride (AlF 3 ) according to the present invention, the particularly preferable blending amount of the lithium (Li) metal is 5 to 20 mol%.
　　１　　Ａｌ原子
　　２　　フッ素原子 1 Al atom 2 Fluorine atom

Claims (11)

  1. 　フッ化物イオンの脱離による空孔を有する改質フッ化アルミニウムである、フッ化物イオン二次電池用負極活物質。 A negative electrode active material for a fluoride ion secondary battery, which is a modified aluminum fluoride having pores due to desorption of fluoride ions.
  2. 　前記空孔は、脱フッ化反応および再フッ化反応の起点となる、請求項１に記載のフッ化物イオン二次電池用負極活物質。 2. The negative electrode active material for a fluoride ion secondary battery according to claim 1, wherein the holes serve as starting points for a defluorination reaction and a refluorination reaction.
  3. 　前記空孔は、改質前のフッ化アルミニウムにおいて、フッ素原子が存在していた領域である、請求項１または２に記載のフッ化物イオン二次電池用負極活物質。 The negative electrode active material for a fluoride ion secondary battery according to claim 1 or 2, wherein the vacancies are regions where fluorine atoms existed in the aluminum fluoride before modification.
  4. 　前記フッ化物イオンの脱離は、フッ化アルミニウムに、アルカリ金属またはアルカリ土類金属を接触させてなる、請求項１～３いずれか記載のフッ化物イオン二次電池用負極活物質。 The negative electrode active material for a fluoride ion secondary battery according to any one of claims 1 to 3, wherein the desorption of the fluoride ions is made by bringing an alkali metal or an alkaline earth metal into contact with aluminum fluoride.
  5. 　請求項１～４いずれか記載のフッ化物イオン二次電池用負極活物質を含む、フッ化物イオン二次電池用負極。 A negative electrode for a fluoride ion secondary battery comprising the negative electrode active material for a fluoride ion secondary battery according to any one of claims 1 to 4.
  6. 　請求項５に記載のフッ化物イオン二次電池用負極と、固体電解質と、正極と、を備えるフッ化物イオン二次電池。 A fluoride ion secondary battery comprising the negative electrode for a fluoride ion secondary battery according to claim 5, a solid electrolyte, and a positive electrode.
  7. 　フッ化物イオン二次電池用負極活物質となる改質フッ化アルミニウムを製造する方法であって、
    　フッ化アルミニウムと、アルカリ金属またはアルカリ土類金属とを接触させて、前記フッ化アルミニウムからフッ化物イオンを脱離させることにより、前記フッ化物イオンとして脱離したフッ素原子の存在位置を空孔として改質フッ化アルミニウムとする、フッ化物イオン二次電池用負極活物質の製造方法。     A method for producing a modified aluminum fluoride to be a negative electrode active material for a fluoride ion secondary battery,
    By bringing aluminum fluoride into contact with an alkali metal or alkaline earth metal and desorbing fluoride ions from the aluminum fluoride, the position of the fluorine atom desorbed as the fluoride ions is defined as a vacancy. A method for producing a negative electrode active material for a fluoride ion secondary battery, which is modified aluminum fluoride.
  8. 　前記アルカリ金属または前記アルカリ土類金属はフッ化物となり、前記フッ化アルミニウムは一部のフッ素原子が引き抜かれ、アルミニウム金属にはならない、請求項７記載のフッ化物イオン二次電池用負極活物質の製造方法。 The negative electrode active material for a fluoride ion secondary battery according to claim 7, wherein the alkali metal or the alkaline earth metal becomes a fluoride, and a part of fluorine atoms is extracted from the aluminum fluoride and does not become an aluminum metal. Production method.
  9. 　前記アルカリ金属または前記アルカリ土類金属の比率は、前記フッ化アルミニウムとの合計に対して５～２０ｍｏｌ％である、請求項７または８に記載のフッ化物イオン二次電池用負極活物質の製造方法。 The production of a negative electrode active material for a fluoride ion secondary battery according to claim 7 or 8, wherein the ratio of the alkali metal or the alkaline earth metal is 5 to 20 mol% with respect to the total with the aluminum fluoride. Method.
  10. 　前記フッ化アルミニウムは、α－ＡｌＦ３である、請求項７～９いずれかに記載のフッ化物イオン二次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a fluoride ion secondary battery according to any one of claims 7 to 9, wherein the aluminum fluoride is α-AlF 3 .
  11. 　前記アルカリ金属は、Ｌｉ金属である、請求項７～１０いずれかに記載のフッ化物イオン二次電池用負極活物質の製造方法。 The method for producing a negative electrode active material for a fluoride ion secondary battery according to any one of claims 7 to 10, wherein the alkali metal is Li metal.
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