WO2011043243A1 - Sodium secondary battery - Google Patents

Sodium secondary battery Download PDF

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Publication number
WO2011043243A1
WO2011043243A1 PCT/JP2010/067093 JP2010067093W WO2011043243A1 WO 2011043243 A1 WO2011043243 A1 WO 2011043243A1 JP 2010067093 W JP2010067093 W JP 2010067093W WO 2011043243 A1 WO2011043243 A1 WO 2011043243A1
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secondary battery
positive electrode
sodium
sodium secondary
negative electrode
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PCT/JP2010/067093
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French (fr)
Japanese (ja)
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哲理 中山
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住友化学株式会社
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Publication of WO2011043243A1 publication Critical patent/WO2011043243A1/en

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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
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/483—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides for non-aqueous cells
    • 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
    • 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
    • H01M4/581—Chalcogenides or intercalation compounds thereof
    • H01M4/5815—Sulfides
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a sodium secondary battery.
  • a typical example of a secondary battery is a lithium secondary battery.
  • Lithium secondary batteries have already been put into practical use as small power sources for mobile phones and laptop computers, and can be used as large power sources for power sources for automobiles such as electric vehicles and hybrid vehicles, and power sources for distributed power storage. Therefore, the demand for lithium secondary batteries is increasing.
  • the composite metal oxide constituting the positive electrode of the lithium secondary battery contains a large amount of rare metal elements such as lithium, there is a concern about the supply of raw materials for these elements in order to meet the increasing demand for large-scale power supplies. Yes.
  • sodium secondary batteries are being studied as secondary batteries that can solve the above supply concerns.
  • a sodium secondary battery can be composed of a resource-rich and inexpensive material. It is expected that a large-scale power supply can be supplied in large quantities by putting sodium secondary batteries into practical use.
  • Patent Document 1 Na 0.7 Ni 0.3 Co 0.7 O 2 is used as a positive electrode, a sodium-lead alloy is used as a negative electrode, and a polypropylene microporous film is used as a separator. A sodium secondary battery disposed between the two is disclosed.
  • a separator in a conventional sodium secondary battery is disposed between a positive electrode and a negative electrode so as to be in contact with both the positive electrode and the negative electrode.
  • This secondary battery has room for improvement in stability of charge / discharge characteristics such as reproducibility of discharge capacity in each cycle.
  • the objective of this invention is providing the sodium secondary battery which is excellent in stability of a charging / discharging characteristic compared with the former.
  • the present invention provides the following means.
  • An insulating inorganic porous layer is formed on the surface of at least one electrode selected from the positive electrode and the negative electrode, Sodium secondary battery.
  • the insulating inorganic porous layer includes an inorganic filler and a binder.
  • the inorganic filler is composed of inorganic particles having an average particle diameter of 0.01 to 2 ⁇ m.
  • ⁇ 4> The sodium secondary battery according to ⁇ 2> or ⁇ 3>, wherein a weight ratio of the inorganic filler to a total weight of the inorganic filler and the binder is 80 to 99% by weight.
  • ⁇ 5> The sodium secondary battery according to any one of ⁇ 2> to ⁇ 4>, wherein the inorganic filler includes alumina.
  • ⁇ 6> The sodium secondary battery according to ⁇ 5>, wherein the inorganic filler has an alumina content of 99.9% by weight or more.
  • ⁇ 7> The sodium secondary battery according to any one of ⁇ 1> to ⁇ 6>, wherein the porosity of the insulating inorganic porous layer is 20 to 80% by volume.
  • ⁇ 8> The sodium secondary battery according to any one of ⁇ 1> to ⁇ 7>, wherein the insulating inorganic porous layer has a thickness of 1 to 10 ⁇ m.
  • the positive electrode includes a composite oxide of sodium and a transition metal or a transition metal chalcogenide as a positive electrode active material.
  • ⁇ 10> The sodium secondary battery according to any one of ⁇ 1> to ⁇ 9>, further comprising a separator.
  • the present invention can provide a sodium secondary battery that is superior in stability of charge and discharge characteristics as compared with a conventional sodium secondary battery.
  • the sodium secondary battery of the present invention is composed of a resource-rich and inexpensive material, and the present invention is extremely practical.
  • a sodium secondary battery of the present invention includes a positive electrode that can be doped with sodium ions and can be dedoped, a negative electrode that can be doped with sodium ions and can be dedoped, and an electrolyte.
  • the positive electrode can be doped with sodium ions and can be undoped.
  • Examples of the positive electrode include an electrode in which a positive electrode mixture containing a positive electrode active material, a binder, a conductive agent, and the like is supported on a positive electrode current collector.
  • a positive electrode mixture paste in which a solvent is added to a positive electrode active material, a binder, a conductive agent, and the like is applied to a positive electrode current collector by a doctor blade method or the like.
  • the thickness of the positive electrode is usually about 5 to 500 ⁇ m.
  • the positive electrode active material can be doped with sodium ions and dedoped.
  • the positive electrode active material is preferably a sodium inorganic compound, for example, a composite oxide of sodium and a transition metal.
  • inorganic sodium compound NaFeO 2, NaMnO 2, NaNiO 2 and NaCoO oxide represented by NaM 1 O 2, such as 2, represented by Na 0.44 Mn 1-a M 1 a O 2 oxide Oxide represented by Na 0.7 Mn 1-a M 1 a O 2.05
  • M 1 is one or more transition metal elements, 0 ⁇ a ⁇ 1)
  • M 2 is one or more transition metal elements, 2 ⁇ b ⁇ 6,2 ⁇ c ⁇ 5)
  • Oxides represented by Na d M 3 e Si 6 O 18 such as Na 2 Fe 2 Si 6 O 18 and Na 2 MnFeSi 6 O 18 (M
  • sodium inorganic compounds containing Fe are preferable.
  • the insulating inorganic porous layer is formed on the surface of the positive electrode, even if the electrolyte present on the positive electrode side, particularly a non-aqueous electrolyte described later, is heated, ions of transition metal elements such as Fe ions are eluted. Since it is suppressed, complexation of ions of the transition metal element is suppressed.
  • the insulating inorganic porous material is formed on the surface of the negative electrode, even if ions of transition metal elements such as Fe ions are eluted from the positive electrode active material or the battery case, the transition metal element on the surface of the negative electrode active material Therefore, the negative electrode is hardly electrochemically deteriorated. As a result, the cycle performance of the sodium secondary battery, that is, the discharge capacity retention rate when charging and discharging are repeated can be further increased.
  • the use of a sodium inorganic compound containing Fe as the positive electrode active material is also preferable from the viewpoint of constituting a secondary battery with a resource-rich and inexpensive material.
  • a sulfide that can be doped with sodium ions and dedoped at a higher potential than the negative electrode as the positive electrode active material It is also possible to use chalcogen compounds such as transition metal chalcogenides.
  • chalcogen compounds such as transition metal chalcogenides.
  • examples of sulfides include compounds represented by M 6 S 2 such as TiS 2 , ZrS 2 , VS 2 , V 2 S 5 , TaS 2 , FeS 2, and NiS 2 (M 6 is one or more transition metal elements). Is mentioned.
  • Examples of the conductive agent used for the positive electrode include carbon materials such as natural graphite, artificial graphite, cokes, and carbon black.
  • binder used for the positive electrode examples include a polymer of a fluorine compound.
  • fluorine compound examples include fluorinated alkyl (having 1 to 18 carbon atoms) (meth) acrylate, perfluoroalkyl (meth) acrylate [for example, perfluorododecyl (meth) acrylate, perfluoro n-octyl (meth) acrylate, Perfluoro n-butyl (meth) acrylate]; perfluoroalkyl-substituted alkyl (meth) acrylate [eg, perfluorohexylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate]; perfluorooxyalkyl (meth) acrylate [ For example, perfluorododecyloxyethyl (meth) acrylate and perfluorodecyloxyethyl (meth)
  • binder examples include monomer addition polymers containing an ethylenic double bond that does not contain a fluorine atom.
  • monomers include (cyclo) alkyl (C1-22) (meth) acrylate [eg, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl] (Meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, octadecyl (meth) acrylate, etc.]; aromatic ring-containing (meth) acrylate [for example, benzyl (Meth) acrylate, phenylethyl (meth) acrylate, etc.]; mono (meth) acrylate of alkylene glycol or
  • Examples thereof include a conjugated double bond-containing monomer.
  • a copolymer such as an ethylene / vinyl acetate copolymer, a styrene / butadiene copolymer, or an ethylene / propylene copolymer may be used.
  • the carboxylic acid vinyl ester polymer may be partially or completely saponified, such as polyvinyl alcohol.
  • the binder may be a copolymer of a fluorine compound and a monomer containing an ethylenic double bond not containing a fluorine atom.
  • binder examples include, for example, polysaccharides such as starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylhydroxyethylcellulose, nitrocellulose and derivatives thereof; phenol resin; melamine resin; Polyurethane resin; urea resin; polyamide resin; polyimide resin; polyamideimide resin; petroleum pitch;
  • Two or more binders may be used.
  • a plasticizer may be used in order to facilitate coating on the positive electrode current collector.
  • Examples of the solvent used for the positive electrode include aprotic polar solvents such as N-methyl-2-pyrrolidone, alcohols such as isopropyl alcohol, ethyl alcohol or methyl alcohol, ethers such as propylene glycol dimethyl ether, acetone, Examples thereof include ketones such as methyl ethyl ketone and methyl isobutyl ketone.
  • aprotic polar solvents such as N-methyl-2-pyrrolidone
  • alcohols such as isopropyl alcohol, ethyl alcohol or methyl alcohol
  • ethers such as propylene glycol dimethyl ether
  • acetone examples thereof include ketones such as methyl ethyl ketone and methyl isobutyl ketone.
  • the conductive adhesive is, for example, a mixture of a conductive agent and a binder.
  • the conductive adhesive is preferably a mixture of carbon black and polyvinyl alcohol because it does not require the use of a solvent, is easy to prepare, and is excellent in storage stability.
  • the blending amount of the binder is usually about 0.5 to 30 parts by weight, preferably about 2 to 30 parts by weight with respect to 100 parts by weight of the positive electrode active material.
  • the compounding amount of the conductive agent is usually about 1 to 50 parts by weight, preferably about 1 to 30 parts by weight with respect to 100 parts by weight of the positive electrode active material.
  • the amount of the solvent is usually about 50 to 500 parts by weight, preferably about 100 to 200 parts by weight, per 100 parts by weight of the positive electrode active material.
  • Examples of the positive electrode current collector used for the positive electrode include metals such as nickel, aluminum, titanium, copper, gold, silver, platinum, aluminum alloys, and stainless steel, such as carbon materials, activated carbon fibers, nickel, aluminum, and zinc. Copper, tin, lead, or alloys thereof formed by plasma spraying or arc spraying, for example, rubber or resin such as styrene-ethylene-butylene-styrene copolymer (SEBS) dispersed in a conductive agent Examples include conductive films. In particular, aluminum, nickel, stainless steel, and the like are preferable. In particular, aluminum is preferable because it can be easily processed into a thin film and is inexpensive.
  • metals such as nickel, aluminum, titanium, copper, gold, silver, platinum, aluminum alloys, and stainless steel, such as carbon materials, activated carbon fibers, nickel, aluminum, and zinc. Copper, tin, lead, or alloys thereof formed by plasma spraying or arc spraying, for example, rubber or resin such as styrene-ethylene-
  • Examples of the shape of the positive electrode current collector include a foil shape, a flat plate shape, a mesh shape, a net shape, a lath shape, a punching metal shape, an embossed shape, or a combination thereof (for example, a mesh-like flat plate). .
  • irregularities may be formed on the surface.
  • the negative electrode can be doped with sodium ions and dedoped.
  • the negative electrode can be doped with sodium ions and dedope at a lower potential than the positive electrode.
  • the negative electrode include an electrode in which a negative electrode active material, a binder, and a negative electrode mixture containing a conductive agent as necessary are supported on a negative electrode current collector.
  • a negative electrode mixture paste in which a solvent is added to a negative electrode active material and a binder is applied to a negative electrode current collector by a doctor blade method or the like.
  • Sodium metal or sodium alloy itself can also be used as the negative electrode.
  • the thickness of the negative electrode is usually about 5 to 500 ⁇ m.
  • the binder and the solvent in the negative electrode include the same as the binder and the solvent in the positive electrode. Water can also be used as the solvent.
  • the negative electrode active material can be doped with sodium ions and dedoped.
  • the negative electrode active material include carbon materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, organic polymer compound fired bodies, non-graphitizable carbon materials, and sodium ions. Materials that can be doped with and dedoped can be used.
  • the negative electrode active material is preferably a non-graphitizable carbon material.
  • the combination of the negative electrode using the non-graphitizable carbon material as the negative electrode active material and the insulating inorganic porous layer is a particularly excellent combination from the viewpoint of enhancing the rate characteristics of the sodium secondary battery.
  • Examples of the shape of the carbon material include flakes such as natural graphite, spheres such as mesocarbon microbeads, fibers such as graphitized carbon fibers, and fine powder aggregates.
  • Examples of the conductive agent in the negative electrode include the same conductive agents as those in the positive electrode. The carbon material in the negative electrode sometimes plays a role as a conductive agent.
  • the negative electrode active material in the positive electrode is the above-mentioned sodium inorganic compound
  • the negative electrode active material can be doped with sodium ions at a potential lower than that of the positive electrode, and can be undope such as sulfide.
  • Chalcogen compounds can also be used.
  • Examples of the negative electrode current collector include Cu, Ni, and stainless steel. Cu is preferable because it is difficult to form an alloy with sodium and it is easy to process into a thin film.
  • Examples of the shape of the negative electrode current collector include a foil shape, a flat plate shape, a mesh shape, a net shape, a lath shape, a punching metal shape, an embossed shape, and a combination thereof (for example, a mesh-like flat plate). . By etching the surface of the negative electrode current collector, irregularities may be formed on the surface.
  • the insulating inorganic porous layer is formed on the surface of at least one electrode selected from a positive electrode and a negative electrode.
  • the insulating inorganic porous layer is integrated with the electrode.
  • the insulating inorganic porous layer is disposed between the positive electrode and the negative electrode, and plays a role of insulating between the positive electrode and the negative electrode.
  • the insulating inorganic porous layer may be formed on both surfaces of the positive electrode and the negative electrode.
  • the insulating inorganic porous layer may be formed on both surfaces of each electrode.
  • Such an insulating inorganic porous layer can further improve the cycle performance of the sodium secondary battery, that is, the discharge capacity maintenance rate when charging and discharging are repeated.
  • the insulating inorganic porous material is formed on the surface of the positive electrode, transition metal elements such as Fe ions from the positive electrode active material even when the electrolyte present on the positive electrode side, particularly the nonaqueous electrolyte described later, is heated. Since the elution of the ions is suppressed, the complexation of transition metal ions is suppressed.
  • the insulating inorganic porous material is formed on the surface of the negative electrode, even if ions of transition metal elements such as Fe ions are eluted from the positive electrode active material or the battery case, the transition metal element on the surface of the negative electrode active material Therefore, the negative electrode is hardly electrochemically deteriorated. By these, the cycle property of a sodium secondary battery can be improved more.
  • the insulating inorganic porous material is preferably formed on the surface of the negative electrode.
  • inorganic substances constituting the insulating inorganic porous layer include inorganic substances having insulating properties among inorganic substances such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates and sulfates. . More specific examples include inorganic substances such as alumina, silica, titanium dioxide, calcium carbonate and the like. 1 type may be sufficient as an inorganic substance, and 2 or more types may be sufficient as it.
  • the insulating inorganic porous layer can be formed on the surface of the electrode by using a sputtering method, a vapor deposition method, a chemical vapor deposition (CVD) method or the like, or a mixture containing an inorganic filler and a binder. It can also form by the method of coating on the surface of an electrode. Since the insulating inorganic porous layer can be formed by a simple operation, a method of applying a mixture containing an inorganic filler and a binder to the surface of the electrode is preferable. In this case, the obtained insulating inorganic porous layer contains an inorganic filler and a binder.
  • the mixture containing the inorganic filler and the binder may be dispersed or dissolved in a solvent before being applied to the surface of the electrode.
  • a mixture paste is obtained.
  • the mixture paste is applied to the surface of the electrode, and the solvent is removed from the obtained coated electrode by drying or the like, whereby an insulating inorganic porous layer is formed.
  • the insulating inorganic porous layer is preferably a layer containing an inorganic filler and a binder.
  • the insulating inorganic porous layer contains an inorganic filler binder, the binding property between the insulating inorganic porous layer and the electrode is improved, and the insulating inorganic porous layer is difficult to fall off from the electrode.
  • the insulating inorganic porous layer is composed of an inorganic filler and a binder, the binding property is further improved.
  • the insulating inorganic porous layer is a component such as a residual solvent used in coating or an additive component contained in the binder. May be included.
  • the inorganic filler among inorganic substances such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates, sulfates, etc., powder containing an inorganic substance having insulating properties, for example, 80 wt.% Of such inorganic substances % Or more, 90% by weight or more, 95% by weight or more, or 99% by weight or more of the powder.
  • powders containing inorganic substances such as alumina, silica, titanium dioxide, and calcium carbonate. 1 type may be sufficient as an inorganic filler, and 2 or more types may be sufficient as it.
  • binder and solvent in the insulating inorganic porous layer examples include the same binder and solvent as in the positive electrode and the negative electrode.
  • the average particle diameter of the inorganic particles constituting the inorganic filler is appropriately selected in consideration of the ease of forming the insulating inorganic porous layer and the ease of controlling the layer thickness.
  • the average particle diameter of the inorganic particles constituting the inorganic filler is preferably 0.01 ⁇ m or more, 0.1 ⁇ m or more, or 0.3 ⁇ m or more, and is 2 ⁇ m or less, 1.5 ⁇ m or less, or 1.0 ⁇ m or less.
  • the average particle diameter of the inorganic particles constituting the inorganic filler is a value of D 50 based on volume as determined by laser diffraction particle size distribution measurement.
  • the weight ratio of the inorganic filler to the total weight of the inorganic filler and the binder may be appropriately set in consideration of the average particle size of the inorganic filler. Care must be taken not to completely block the pores of the insulating inorganic porous layer with the binder.
  • the weight ratio of the inorganic filler to the total weight of the inorganic filler and the binder is preferably 80% by weight, 85% by weight, 90% by weight, and 99% by weight or less.
  • the inorganic filler preferably contains alumina. More preferably, the inorganic filler has an alumina content of 99.9% by weight or more. When the alumina content is 99.9% by weight or more, the chemical stability of the insulating inorganic porous layer is further improved. Part or all of the inorganic filler is preferably composed of substantially spherical alumina particles.
  • the shape of the filler includes a substantially spherical shape, a plate shape, a column shape, a needle shape, a whisker shape, a fiber shape, and the like.
  • the pores of the insulating inorganic porous layer become more uniform.
  • the substantially spherical particles include particles having a particle aspect ratio (particle major axis / particle minor axis) in the range of 1 to 1.5. The aspect ratio of the particles can be determined by an electron micrograph.
  • the porosity of the insulating inorganic porous layer can be appropriately set in consideration of the heat resistance, mechanical strength, sodium ion conductivity, etc. of the insulating inorganic porous layer.
  • the porosity of the insulating inorganic porous layer is preferably 20% by volume or more, or 30% by volume or more, and is 80% by volume or less, 70% by volume or less, or 60% by volume or less.
  • Va is determined by the vertical, horizontal, and thickness values of the insulating inorganic porous layer
  • Vt is determined by the weight of the insulating inorganic porous layer, the weight ratio of the constituent material, and the true specific gravity of each constituent material.
  • the thickness of the insulating inorganic porous layer may be 0.1 ⁇ m or more, 1 ⁇ m or more, or 3 ⁇ m or more, and may be 10 ⁇ m or less, or 7 ⁇ m or less.
  • the thickness is preferably 1 to 10 ⁇ m. is there.
  • the electrolyte is usually used after being dissolved in an organic solvent.
  • the organic solvent in which the electrolyte is dissolved is a nonaqueous electrolytic solution.
  • electrolyte examples include NaClO 4 , NaPF 6 , NaAsF 6 , NaSbF 6 , NaBF 4 , NaCF 3 SO 3 , NaN (SO 2 CF 3 ) 2 , lower aliphatic carboxylic acid sodium salt, NaAlCl 4, and the like.
  • the above electrolyte may be used.
  • the electrolyte is preferably at least one fluorine-containing lithium salt selected from the group consisting of NaPF 6 , NaAsF 6 , NaSbF 6 , NaBF 4 , NaCF 3 SO 3 and NaN (SO 2 CF 3 ) 2 .
  • organic solvent in the non-aqueous electrolyte examples include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, isopropyl methyl carbonate, vinylene carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, Carbonates such as 1,2-di (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether , Ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate and ⁇ -butyrolactone; nitriles such as acetonitrile and butyronitrile; Amides such as N, N-dimethylformamide and N, N-dimethyl
  • the concentration of the electrolyte in the nonaqueous electrolytic solution may be appropriately set in consideration of the solubility of the electrolyte in the organic solvent.
  • the concentration of the electrolyte is usually about 0.1 mol (electrolyte) / L (non-aqueous electrolyte) to 2 mol (electrolyte) / L (non-aqueous electrolyte), preferably 0.3 mol (electrolyte) / L. (Nonaqueous electrolyte) to about 1.5 mol (electrolyte) / L (nonaqueous electrolyte).
  • the separator includes a porous film made of resin.
  • the sodium secondary battery of the present invention functions sufficiently as a secondary battery even without a separator.
  • the separator is usually disposed between the positive electrode and the negative electrode.
  • the sodium secondary battery of the present invention further includes a separator to cut off the current and prevent an excessive current from flowing when an abnormal current flows in the battery due to a short circuit between the positive electrode and the negative electrode. Can have a shutdown function.
  • the resin constituting the porous film a resin that does not dissolve in the organic solvent may be selected.
  • the resin include polyolefin resins such as polyethylene and polypropylene, and thermoplastic polyurethane resins. These two or more kinds of resins may be mixed.
  • the porous film preferably contains a polyolefin resin, and more preferably contains polyethylene.
  • polyethylene include low density polyethylene, high density polyethylene, linear polyethylene, and the like, and ultrahigh molecular weight polyethylene is also included. From the viewpoint of further increasing the puncture strength of the porous film, the porous film preferably contains ultrahigh molecular weight polyethylene.
  • the porous film preferably contains a wax made of polyolefin having a low molecular weight (weight average molecular weight of 10,000 or less).
  • the thickness of the porous film is usually 3 to 30 ⁇ m, preferably 3 to 20 ⁇ m.
  • the separator may be a laminated film in which a heat-resistant porous layer is laminated on one side or both sides of a porous film.
  • the thickness of the laminated film is usually 40 ⁇ m or less, preferably 20 ⁇ m or less.
  • the value of A / B is preferably 0 or more and 1 or less.
  • the heat resistant porous layer may contain a heat resistant resin. Examples of the heat resistant resin include polyamide, polyimide, polyamideimide, polycarbonate, polyacetal, polysulfone, polyphenylene sulfide, polyetherketone, aromatic polyester, polyethersulfone, polyetherimide, and the like.
  • the heat resistant resin is preferably polyamide, polyimide, polyamideimide, polyethersulfone, polyetherimide, more preferably polyamide, polyimide, polyamideimide, and even more preferably aromatic.
  • Nitrogen-containing aromatic polymers such as polyamide (para-oriented aromatic polyamide, meta-oriented aromatic polyamide), aromatic polyimide, aromatic polyamideimide and the like.
  • the heat resistant resin include poly-4-methylpentene-1 and cyclic olefin polymers.
  • the heat resistant porous layer can also contain a filler.
  • the filler may be an organic powder, an inorganic powder, or a mixture thereof.
  • the average particle diameter of the particles constituting the filler is preferably 0.01 ⁇ m or more and 1 ⁇ m or less.
  • the insulating inorganic porous layer is disposed between the positive electrode and the negative electrode.
  • the sodium secondary battery of the present invention is obtained by laminating or laminating and winding a positive electrode, an insulating inorganic porous layer, and a negative electrode in this order, and this electrode group is obtained as a battery case such as a battery can. It can be manufactured by storing it in and injecting a non-aqueous electrolyte into the case.
  • the sodium secondary battery of the present invention has a separator, the separator is formed between the insulating inorganic porous layer formed on the positive electrode and the negative electrode, the insulating inorganic porous layer formed on the positive electrode and the negative electrode, or the positive electrode.
  • the insulating inorganic porous layer is disposed between the insulating inorganic porous layer formed on the negative electrode.
  • Examples of the shape of the electrode group include a shape in which a cross section when the electrode group is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, a rectangle with rounded corners, or the like.
  • Examples of the shape of the secondary battery include a paper shape, a coin shape, a cylindrical shape, and a square shape.
  • Comparative Example 1 (1) Preparation of positive electrode Sodium carbonate (Na 2 CO 3 : Wako Pure Chemical Industries, Ltd .: purity 99.8%), manganese oxide (IV) (MnO 2 : manufactured by Kojundo Chemical Laboratory Co., Ltd .: purity 99. 9%), iron oxide (II, III) (Fe 3 O 4 : manufactured by Kojundo Chemical Laboratory Co., Ltd .: purity 99%), and nickel oxide (IIO) (NiO: manufactured by Kojundo Chemical Laboratory Co., Ltd .: purity) 99%) to a molar ratio of Na: Mn: Fe: Ni of 0.8: 0.333: 0.333: 0.333 and mixed for 4 hours in a dry ball mill to obtain a mixture. It was.
  • Sodium carbonate Na 2 CO 3 : Wako Pure Chemical Industries, Ltd .: purity 99.8%
  • manganese oxide (IV) MnO 2 : manufactured by Kojundo Chemical Laboratory Co., Ltd .: purity 99. 9%
  • the obtained mixture was filled in an alumina boat and baked at 800 ° C. for 2 hours in an air atmosphere using an electric furnace to obtain a sodium inorganic compound C1.
  • Acetylene black manufactured by Denki Kagaku Kogyo Co., Ltd.
  • PVdF manufactured by Kureha Co., Ltd., PolyVinylideneDiFluoride
  • the weighed sodium inorganic compound C1 and the weighed conductive agent were sufficiently mixed in an agate mortar.
  • An appropriate amount of N-methyl-2-pyrrolidone (NMP: manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added to the obtained mixture, and PVdF was further added and mixed uniformly to obtain a paste.
  • the obtained paste was applied to an aluminum foil with a thickness of 40 ⁇ m, which is a current collector, with a thickness of 100 ⁇ m using an applicator, and the obtained current collector was put into a drier to remove NMP. While removing, a positive electrode sheet was obtained by sufficiently drying. This positive electrode sheet was punched to a diameter of 1.5 cm using an electrode punching machine, and then sufficiently pressed by a hand press to obtain a circular positive electrode C1 having a diameter of 1.5 cm.
  • the constant current charge / discharge test of the sodium secondary battery was performed under the following conditions.
  • Charging / discharging conditions Charging was performed by CC (Constant Current: constant current) at a rate of 0.1 C up to 4.0 V (speed of complete charging in 10 hours). For discharging, CC discharging was performed at the same speed as the charging speed, and cut off at a voltage of 1.5V. Charging and discharging after the next cycle were performed at the same rate as the charging rate, and cut off at a charging voltage of 4.0 V and a discharging voltage of 1.5 V as in the first cycle. The charge / discharge test was performed for 10 cycles in total.
  • Example 1 Production of positive electrode A positive electrode C1 was produced in the same manner as in Comparative Example 1. Next, alumina as an inorganic filler (average particle size 0.5 ⁇ m, manufactured by Sumitomo Chemical Co., Ltd., product name AKP-3000, alumina content of 99.99% by weight or more) and PVdF are combined, and the inorganic filler: PVdF weight ratio. was weighed to 99: 1 and mixed to obtain a mixture. NMP is added to the mixture to prepare a mixture paste, and this paste is applied to the surface of the positive electrode C1 to obtain a coated electrode, which is dried at 60 ° C. for 2 hours, and an insulating inorganic porous material is formed on the surface of the positive electrode C1. A layer was formed to obtain a positive electrode E1. The thickness of the insulating inorganic porous layer was 5 ⁇ m, and the porosity of the insulating inorganic porous layer was 48% by volume.
  • alumina as an inorganic filler average particle size
  • Example 2 Production of positive electrode A positive electrode E1 was produced in the same manner as in Example 1.
  • the PCRA was placed in a rotary kiln and heated at 300 ° C. for 1 hour under an air atmosphere. Then, the atmosphere of the rotary kiln was replaced with argon and baked at 1000 ° C. for 4 hours. Subsequently, the carbon material E2 which is a baking body of an organic polymer compound was obtained by grind
  • pulverizing with a ball mill (Agate ball, 28 rpm, 5 minutes). Carbon material E2 and PVdF as a binder were weighed so as to have a weight ratio of carbon material E2: binder 95: 5. After the binder was dissolved in NMP, carbon material E2 was added to obtain a paste.
  • the obtained paste is applied to a copper foil having a thickness of 10 ⁇ m, which is a current collector, with a thickness of 100 ⁇ m using an applicator, and the obtained current collector is put into a dryer, and NMP is added.
  • the negative electrode sheet was obtained by fully drying while removing. This negative electrode sheet was punched to a diameter of 1.5 cm using an electrode punching machine, and then sufficiently pressed by a hand press to obtain a circular negative electrode E2 having a diameter of 1.5 cm.
  • Example 3 Production of positive electrode A positive electrode C1 was produced in the same manner as in Comparative Example 1.
  • a negative electrode E2 was produced in the same manner as in Example 2. Next, alumina as an inorganic filler (average particle size 0.5 ⁇ m, manufactured by Sumitomo Chemical Co., Ltd., product name AKP-3000, alumina content of 99.99% by weight or more) and PVdF are combined, and the inorganic filler: PVdF weight ratio. was weighed to 99: 1 and mixed to obtain a mixture. NMP is added to the mixture to prepare a mixture paste, and this paste is applied to the surface of the negative electrode E2 to obtain a coated electrode, which is dried at 60 ° C. for 2 hours, and an insulating inorganic porous material is formed on the surface of the negative electrode E2. A layer was formed to obtain a negative electrode E3. The thickness of the insulating inorganic porous layer was 5 ⁇ m, and the porosity of the insulating inorganic porous layer was 48% by volume.
  • a sodium secondary battery E3 was prepared by combining the polypropylene porous film (thickness 20 ⁇ m), the negative electrode E3 with the copper foil facing upward, and the upper part of the coin cell.
  • the test battery was assembled in a glove box in an argon atmosphere.

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Abstract

Disclosed is a sodium secondary battery with superior stability in the charge-discharge behavior thereof. The sodium secondary battery is equipped with a positive electrode that can be sodium ion-doped and undoped, a negative electrode that can be sodium ion-doped and undoped, and an electrolyte; and an insulating inorganic porous layer is formed on the surface of at least one electrode selected from either the positive electrode or the negative electrode.

Description

ナトリウム二次電池Sodium secondary battery
　本発明は、ナトリウム二次電池に関する。 The present invention relates to a sodium secondary battery.
　二次電池としては、リチウム二次電池が代表的である。リチウム二次電池は、携帯電話やノートパソコンなどの小型電源として既に実用化され、さらに、電気自動車、ハイブリッド自動車等の自動車用電源や分散型電力貯蔵用電源等の大型電源として使用可能であることから、リチウム二次電池の需要は増大しつつある。しかしながら、リチウム二次電池の正極を構成する複合金属酸化物は、リチウム等の稀少金属元素を多く含有するため、大型電源の需要の増大に対応するためのこれら元素の原料の供給が懸念されている。 A typical example of a secondary battery is a lithium secondary battery. Lithium secondary batteries have already been put into practical use as small power sources for mobile phones and laptop computers, and can be used as large power sources for power sources for automobiles such as electric vehicles and hybrid vehicles, and power sources for distributed power storage. Therefore, the demand for lithium secondary batteries is increasing. However, since the composite metal oxide constituting the positive electrode of the lithium secondary battery contains a large amount of rare metal elements such as lithium, there is a concern about the supply of raw materials for these elements in order to meet the increasing demand for large-scale power supplies. Yes.
　これに対し、上記の供給懸念を解決することができる二次電池として、ナトリウム二次電池が検討されている。ナトリウム二次電池は、資源量が豊富でかつ安価な材料により構成することができる。ナトリウム二次電池を実用化することにより、大型電源を大量に供給可能になることが期待される。 In contrast, sodium secondary batteries are being studied as secondary batteries that can solve the above supply concerns. A sodium secondary battery can be composed of a resource-rich and inexpensive material. It is expected that a large-scale power supply can be supplied in large quantities by putting sodium secondary batteries into practical use.
　特許文献１には、正極としてＮａ０．７Ｎｉ０．３Ｃｏ０．７Ｏ２を用い、負極としてナトリウム－鉛合金を用い、セパレータとしてポリプロピレン製マイクロポーラスフィルムを用いて、セパレータを正極と負極の間に配置させたナトリウム二次電池が開示されている。 In Patent Document 1, Na 0.7 Ni 0.3 Co 0.7 O 2 is used as a positive electrode, a sodium-lead alloy is used as a negative electrode, and a polypropylene microporous film is used as a separator. A sodium secondary battery disposed between the two is disclosed.
特開平３－２９１８６３号公報（実施例１）JP-A-3-291863 (Example 1)
　従来のナトリウム二次電池におけるセパレータは、正極と負極の間に、該正極および該負極の双方に接するように配置される。この二次電池は、各サイクルにおける放電容量の再現性など、充放電特性の安定性に改善の余地がある。本発明の目的は、従来に比し、充放電特性の安定性に優れるナトリウム二次電池を提供することにある。 A separator in a conventional sodium secondary battery is disposed between a positive electrode and a negative electrode so as to be in contact with both the positive electrode and the negative electrode. This secondary battery has room for improvement in stability of charge / discharge characteristics such as reproducibility of discharge capacity in each cycle. The objective of this invention is providing the sodium secondary battery which is excellent in stability of a charging / discharging characteristic compared with the former.
　本発明は、次の手段を提供する。
＜１＞　ナトリウムイオンでドープされることができかつ脱ドープされることができる正極と、ナトリウムイオンでドープされることができかつ脱ドープされることができる負極と、電解質とを備え、かつ
　前記正極および前記負極から選ばれる少なくとも一つの電極の表面に、絶縁性無機多孔層が形成されている、
ナトリウム二次電池。
＜２＞　前記絶縁性無機多孔層が、無機フィラーおよび結着剤を含む＜１＞のナトリウム二次電池。
＜３＞　前記無機フィラーは、平均粒径が０．０１～２μｍの無機粒子から構成される＜２＞のナトリウム二次電池。
＜４＞　前記無機フィラーおよび前記結着剤の合計重量に対する前記無機フィラーの重量割合が、８０～９９重量％である＜２＞または＜３＞のナトリウム二次電池。
＜５＞　前記無機フィラーが、アルミナを含む＜２＞～＜４＞のいずれかのナトリウム二次電池。
＜６＞　前記無機フィラーのアルミナ含有量が、９９．９重量％以上である＜５＞のナトリウム二次電池。
＜７＞　前記絶縁性無機多孔層の空隙率が、２０～８０体積％である＜１＞～＜６＞のいずれかのナトリウム二次電池。
＜８＞　前記絶縁性無機多孔層の厚みが、１～１０μｍである＜１＞～＜７＞のいずれかのナトリウム二次電池。
＜９＞　前記正極が、正極活物質として、ナトリウムと遷移金属との複合酸化物、又は遷移金属カルコゲン化物を含む、請求項１～８のいずれかに記載のナトリウム二次電池。
＜１０＞　セパレータをさらに備える＜１＞～＜９＞のいずれかのナトリウム二次電池。 The present invention provides the following means.
<1> A positive electrode that can be doped with sodium ions and can be dedope, a negative electrode that can be doped with sodium ions and can be dedope, and an electrolyte, and An insulating inorganic porous layer is formed on the surface of at least one electrode selected from the positive electrode and the negative electrode,
Sodium secondary battery.
<2> The sodium secondary battery according to <1>, wherein the insulating inorganic porous layer includes an inorganic filler and a binder.
<3> The sodium secondary battery according to <2>, wherein the inorganic filler is composed of inorganic particles having an average particle diameter of 0.01 to 2 μm.
<4> The sodium secondary battery according to <2> or <3>, wherein a weight ratio of the inorganic filler to a total weight of the inorganic filler and the binder is 80 to 99% by weight.
<5> The sodium secondary battery according to any one of <2> to <4>, wherein the inorganic filler includes alumina.
<6> The sodium secondary battery according to <5>, wherein the inorganic filler has an alumina content of 99.9% by weight or more.
<7> The sodium secondary battery according to any one of <1> to <6>, wherein the porosity of the insulating inorganic porous layer is 20 to 80% by volume.
<8> The sodium secondary battery according to any one of <1> to <7>, wherein the insulating inorganic porous layer has a thickness of 1 to 10 μm.
<9> The sodium secondary battery according to any one of claims 1 to 8, wherein the positive electrode includes a composite oxide of sodium and a transition metal or a transition metal chalcogenide as a positive electrode active material.
<10> The sodium secondary battery according to any one of <1> to <9>, further comprising a separator.
　本発明は、従来のナトリウム二次電池に比して、充放電特性の安定性に優れるナトリウム二次電池を与えることができる。本発明のナトリウム二次電池は、資源量が豊富でかつ安価な材料により構成され、本発明は、極めて実用性に富む。 The present invention can provide a sodium secondary battery that is superior in stability of charge and discharge characteristics as compared with a conventional sodium secondary battery. The sodium secondary battery of the present invention is composed of a resource-rich and inexpensive material, and the present invention is extremely practical.
　本発明のナトリウム二次電池は、ナトリウムイオンでドープされることができかつ脱ドープされることができる正極と、ナトリウムイオンでドープされることができかつ脱ドープされることができる負極と、電解質とを備え、前記正極および前記負極から選ばれる少なくとも一つの電極の表面に、絶縁性無機多孔層が形成されたナトリウム二次電池である。この構成により、ナトリウム二次電池の充放電特性の安定性を向上させることができる。本発明によれば、充放電を繰り返した際のサイクル特性に優れるナトリウム二次電池を得ることが可能である。さらに、高い電流レートで高出力であるナトリウム二次電池、すなわちレート特性に優れるナトリウム二次電池を得ることも可能であることから、急速充放電可能な大型電源を与えることができる。 A sodium secondary battery of the present invention includes a positive electrode that can be doped with sodium ions and can be dedoped, a negative electrode that can be doped with sodium ions and can be dedoped, and an electrolyte. A secondary battery in which an insulating inorganic porous layer is formed on the surface of at least one electrode selected from the positive electrode and the negative electrode. With this configuration, the stability of the charge / discharge characteristics of the sodium secondary battery can be improved. ADVANTAGE OF THE INVENTION According to this invention, it is possible to obtain the sodium secondary battery excellent in the cycling characteristics at the time of repeating charging / discharging. Furthermore, since it is possible to obtain a sodium secondary battery having a high output at a high current rate, that is, a sodium secondary battery having excellent rate characteristics, a large-scale power source capable of rapid charge / discharge can be provided.
＜正極＞
　正極は、ナトリウムイオンでドープされることができかつ脱ドープされることができる。正極としては、正極活物質、結着剤及び導電剤等を含む正極合剤が、正極集電体に担持された電極が挙げられる。具体的な正極の製造方法としては、正極活物質、結着剤及び導電剤等に溶剤が添加された正極合剤ペーストを、正極集電体に、ドクターブレード法などで塗工し、得られたシートを乾燥する方法；該集電体を該ペーストに浸漬し、得られたシートを乾燥する方法；正極活物質、結着剤及び導電剤等に溶剤が添加された混合物を、混練し、成形し、乾燥して得られたシートを、正極集電体に、導電性接着剤等を介して接着して得られた接着シートをプレスし、熱処理乾燥する方法；正極活物質、結着剤、導電剤及び液状潤滑剤等からなる混合物を正極集電体上に成形し、得られた成形物から液状潤滑剤を除去し、これを一軸又は多軸方向に延伸する方法などが挙げられる。正極がシート状である場合、正極の厚みは、通常、５～５００μｍ程度である。 <Positive electrode>
The positive electrode can be doped with sodium ions and can be undoped. Examples of the positive electrode include an electrode in which a positive electrode mixture containing a positive electrode active material, a binder, a conductive agent, and the like is supported on a positive electrode current collector. As a specific method for producing a positive electrode, a positive electrode mixture paste in which a solvent is added to a positive electrode active material, a binder, a conductive agent, and the like is applied to a positive electrode current collector by a doctor blade method or the like. A method of drying the obtained sheet; a method of immersing the current collector in the paste; and a method of drying the obtained sheet; a mixture in which a solvent is added to a positive electrode active material, a binder, a conductive agent, and the like; A method of pressing an adhesive sheet obtained by bonding a sheet obtained by molding and drying to a positive electrode current collector through a conductive adhesive or the like, and drying by heat treatment; positive electrode active material, binder And a method of forming a mixture of a conductive agent and a liquid lubricant on a positive electrode current collector, removing the liquid lubricant from the obtained molded product, and stretching the mixture in a uniaxial or multiaxial direction. When the positive electrode is in sheet form, the thickness of the positive electrode is usually about 5 to 500 μm.
　正極活物質は、ナトリウムイオンでドープされることができかつ脱ドープされることができる。得られるナトリウム二次電池のサイクル性の観点では、正極活物質は、好ましくはナトリウム無機化合物、例えばナトリウムと遷移金属との複合酸化物である。ナトリウム無機化合物の例としては、ＮａＦｅＯ２、ＮａＭｎＯ２、ＮａＮｉＯ２およびＮａＣｏＯ２等のＮａＭ１Ｏ２で表される酸化物、Ｎａ０．４４Ｍｎ１－ａＭ１ ａＯ２で表される酸化物、Ｎａ０．７Ｍｎ１－ａＭ１ ａＯ２．０５で表される酸化物（Ｍ１は１種以上の遷移金属元素、０≦ａ＜１）；Ｎａ６Ｆｅ２Ｓｉ１２Ｏ３０およびＮａ２Ｆｅ５Ｓｉ１２Ｏ３０等のＮａｂＭ２ ｃＳｉ１２Ｏ３０で表される酸化物（Ｍ２は１種以上の遷移金属元素、２≦ｂ≦６、２≦ｃ≦５）；Ｎａ２Ｆｅ２Ｓｉ６Ｏ１８およびＮａ２ＭｎＦｅＳｉ６Ｏ１８等のＮａｄＭ３ ｅＳｉ６Ｏ１８で表される酸化物（Ｍ３は１種以上の遷移金属元素、３≦ｄ≦６、１≦ｅ≦２）；Ｎａ２ＦｅＳｉＯ６等のＮａｆＭ４ ｇＳｉ２Ｏ６で表される酸化物（Ｍ４は遷移金属元素、ＭｇおよびＡｌからなる群より選ばれる１種以上の元素、１≦ｆ≦２、１≦ｇ≦２）；ＮａＦｅＰＯ４、Ｎａ３Ｆｅ２（ＰＯ４）３等のリン酸塩；ＮａＦｅＢＯ４、Ｎａ３Ｆｅ２（ＢＯ４）３等のホウ酸塩；Ｎａ３ＦｅＦ６およびＮａ２ＭｎＦ６等のＮａｈＭ５Ｆ６で表されるフッ化物（Ｍ５は１種以上の遷移金属元素、２≦ｈ≦３）；等が挙げられる。 The positive electrode active material can be doped with sodium ions and dedoped. In view of the cycleability of the obtained sodium secondary battery, the positive electrode active material is preferably a sodium inorganic compound, for example, a composite oxide of sodium and a transition metal. Examples of inorganic sodium compound, NaFeO 2, NaMnO 2, NaNiO 2 and NaCoO oxide represented by NaM 1 O 2, such as 2, represented by Na 0.44 Mn 1-a M 1 a O 2 oxide Oxide represented by Na 0.7 Mn 1-a M 1 a O 2.05 (M 1 is one or more transition metal elements, 0 ≦ a <1); Na 6 Fe 2 Si 12 O 30 and Na 2 Fe 5 Si 12 O Na b M 2 c Si 12 O 30 with oxide represented such 30 (M 2 is one or more transition metal elements, 2 ≦ b ≦ 6,2 ≦ c ≦ 5) Oxides represented by Na d M 3 e Si 6 O 18 such as Na 2 Fe 2 Si 6 O 18 and Na 2 MnFeSi 6 O 18 (M 3 is one or more transition metal elements, 3 ≦ d ≦ 6; 1 ≦ e ≦ 2); N such as Na 2 FeSiO 6 oxide represented by a f M 4 g Si 2 O 6 (M 4 is one or more elements selected from the group consisting of transition metal elements, Mg and Al, 1 ≦ f ≦ 2, 1 ≦ g ≦ 2) Phosphates such as NaFePO 4 and Na 3 Fe 2 (PO 4 ) 3 ; borate salts such as NaFeBO 4 and Na 3 Fe 2 (BO 4 ) 3 ; Na h such as Na 3 FeF 6 and Na 2 MnF 6 ; A fluoride represented by M 5 F 6 (M 5 is one or more transition metal elements, 2 ≦ h ≦ 3); and the like.
　上記のナトリウム無機化合物の中では、Ｆｅを含有するナトリウム無機化合物が好ましい。絶縁性無機多孔層が正極の表面に形成されている場合には、正極側に存在する電解質、特に後述の非水電解液が加熱されても、Ｆｅイオン等の遷移金属元素のイオンの溶出が抑制されることから、遷移金属元素のイオンの錯体化が抑制される。絶縁性無機多孔質が負極の表面に形成されている場合には、正極活物質または電池ケースから、Ｆｅイオン等の遷移金属元素のイオンが溶出したとしても、負極活物質表面への遷移金属元素のイオンの析出が抑制されることから、負極が電気化学的に劣化し難い。これらの結果、ナトリウム二次電池のサイクル性、すなわち、充放電を繰り返した際の放電容量維持率をより高めることができる。正極活物質としてＦｅを含有するナトリウム無機化合物を使用することは、資源量が豊富で安価な材料により、二次電池を構成する観点でも、好ましい。 Among the above-mentioned sodium inorganic compounds, sodium inorganic compounds containing Fe are preferable. When the insulating inorganic porous layer is formed on the surface of the positive electrode, even if the electrolyte present on the positive electrode side, particularly a non-aqueous electrolyte described later, is heated, ions of transition metal elements such as Fe ions are eluted. Since it is suppressed, complexation of ions of the transition metal element is suppressed. When the insulating inorganic porous material is formed on the surface of the negative electrode, even if ions of transition metal elements such as Fe ions are eluted from the positive electrode active material or the battery case, the transition metal element on the surface of the negative electrode active material Therefore, the negative electrode is hardly electrochemically deteriorated. As a result, the cycle performance of the sodium secondary battery, that is, the discharge capacity retention rate when charging and discharging are repeated can be further increased. The use of a sodium inorganic compound containing Fe as the positive electrode active material is also preferable from the viewpoint of constituting a secondary battery with a resource-rich and inexpensive material.
　負極が後述のナトリウム金属またはナトリウム合金から主に構成される場合には、正極活物質として、負極よりも高い電位で、ナトリウムイオンでドープされることができかつ脱ドープされることができる硫化物等のカルコゲン化合物、特に遷移金属カルコゲン化物を用いることもできる。硫化物としてはＴｉＳ２、ＺｒＳ２、ＶＳ２、Ｖ２Ｓ５、ＴａＳ２、ＦｅＳ２およびＮｉＳ２等のＭ６Ｓ２で表される化合物（Ｍ６は１種以上の遷移金属元素）等が挙げられる。 When the negative electrode is mainly composed of sodium metal or a sodium alloy described later, a sulfide that can be doped with sodium ions and dedoped at a higher potential than the negative electrode as the positive electrode active material It is also possible to use chalcogen compounds such as transition metal chalcogenides. Examples of sulfides include compounds represented by M 6 S 2 such as TiS 2 , ZrS 2 , VS 2 , V 2 S 5 , TaS 2 , FeS 2, and NiS 2 (M 6 is one or more transition metal elements). Is mentioned.
　前記の正極に用いられる導電剤としては、天然黒鉛、人造黒鉛、コークス類、カーボンブラックなどの炭素材料などが挙げられる。 Examples of the conductive agent used for the positive electrode include carbon materials such as natural graphite, artificial graphite, cokes, and carbon black.
　前記の正極に用いられる結着剤としては、フッ素化合物の重合体が挙げられる。フッ素化合物としては、例えば、フッ素化アルキル（炭素数１～１８）（メタ）アクリレート、パーフルオロアルキル（メタ）アクリレート［例えば、パーフルオロドデシル（メタ）アクリレート、パーフルオロｎ－オクチル（メタ）アクリレート、パーフルオロｎ－ブチル（メタ）アクリレート］；パーフルオロアルキル置換アルキル（メタ）アクリレート［例えばパーフルオロヘキシルエチル（メタ）アクリレート、パーフルオロオクチルエチル（メタ）アクリレート］；パーフルオロオキシアルキル（メタ）アクリレート［例えば、パーフルオロドデシルオキシエチル（メタ）アクリレート及びパーフルオロデシルオキシエチル（メタ）アクリレートなど］；フッ素化アルキル（炭素数１～１８）クロトネート；フッ素化アルキル（炭素数１～１８）マレート及びフマレート；フッ素化アルキル（炭素数１～１８）イタコネート；フッ素化アルキル置換オレフィン（炭素数２～１０程度、フッ素原子数１～１７程度）；例えばパーフロオロヘキシルエチレン、炭素数２～１０程度及びフッ素原子数１～２０程度の二重結合炭素にフッ素原子が結合したフッ素化オレフィン；テトラフルオロエチレン；トリフルオロエチレン；フッ化ビニリデン；ヘキサフルオロプロピレンなどが挙げられる。 Examples of the binder used for the positive electrode include a polymer of a fluorine compound. Examples of the fluorine compound include fluorinated alkyl (having 1 to 18 carbon atoms) (meth) acrylate, perfluoroalkyl (meth) acrylate [for example, perfluorododecyl (meth) acrylate, perfluoro n-octyl (meth) acrylate, Perfluoro n-butyl (meth) acrylate]; perfluoroalkyl-substituted alkyl (meth) acrylate [eg, perfluorohexylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate]; perfluorooxyalkyl (meth) acrylate [ For example, perfluorododecyloxyethyl (meth) acrylate and perfluorodecyloxyethyl (meth) acrylate, etc.]; fluorinated alkyl (having 1 to 18 carbon atoms) crotonate; fluorinated alkyl (carbon Number 1 to 18) Malate and fumarate; fluorinated alkyl (1 to 18 carbon atoms) itaconate; fluorinated alkyl-substituted olefin (about 2 to 10 carbon atoms, about 1 to 17 fluorine atoms); for example, perfluorohexylethylene, carbon Fluorinated olefins in which fluorine atoms are bonded to double-bonded carbon having about 2 to 10 and about 1 to 20 fluorine atoms; tetrafluoroethylene; trifluoroethylene; vinylidene fluoride; hexafluoropropylene and the like.
　結着剤のその他の例示としては、フッ素原子を含まないエチレン性二重結合を含む単量体の付加重合体が挙げられる。かかる単量体としては、例えば、（シクロ）アルキル（炭素数１～２２）（メタ）アクリレート［例えば、メチル（メタ）アクリレート、エチル（メタ）アクリレート、ｎ－ブチル（メタ）アクリレート、ｉｓｏ－ブチル（メタ）アクリレート、シクロヘキシル（メタ）アクリレート、２－エチルヘキシル（メタ）アクリレート、イソデシル（メタ）アクリレート、ラウリル（メタ）アクリレート、オクタデシル（メタ）アクリレート等］；芳香環含有（メタ）アクリレート［例えば、ベンジル（メタ）アクリレート、フェニルエチル（メタ）アクリレート等］；アルキレングリコールもしくはジアルキレングリコール（アルキレン基の炭素数２～４）のモノ（メタ）アクリレート［例えば、２－ヒドロキシエチル（メタ）アクリレート、２－ヒドロキシプロピル（メタ）アクリレート、ジエチレングリコールモノ（メタ）アクリレート］；（ポリ）グリセリン（重合度１～４）モノ（メタ）アクリレート；多官能（メタ）アクリレート［例えば、（ポリ）エチレングリコール（重合度１～１００）ジ（メタ）アクリレート、（ポリ）プロピレングリコール（重合度１～１００）ジ（メタ）アクリレート、２，２－ビス（４－ヒドロキシエチルフェニル）プロパンジ（メタ）アクリレート、トリメチロールプロパントリ（メタ）アクリレート等］などの（メタ）アクリル酸エステル系単量体；（メタ）アクリルアミド、（メタ）アクリルアミド系誘導体［例えば、Ｎ－メチロール（メタ）アクリルアミド、ダイアセトンアクリルアミド等］などの（メタ）アクリルアミド系単量体；（メタ）アクリロニトリル、２－シアノエチル（メタ）アクリレート、２－シアノエチルアクリルアミド等のシアノ基含有単量体；スチレン及び炭素数７～１８のスチレン誘導体［例えば、α－メチルスチレン、ビニルトルエン、ｐ－ヒドロキシスチレン及びジビニルベンゼン等］などのスチレン系単量体；炭素数４～１２のアルカジエン［例えば、ブタジエン、イソプレン、クロロプレン等］などのジエン系単量体；カルボン酸（炭素数２～１２）ビニルエステル［例えば、酢酸ビニル、プロピオン酸ビニル、酪酸ビニル及びオクタン酸ビニル等］、カルボン酸（炭素数２～１２）（メタ）アリルエステル［例えば、酢酸（メタ）アリル、プロピオン酸（メタ）アリル及びオクタン酸（メタ）アリル等］などのアルケニルエステル系単量体；グリシジル（メタ）アクリレート、（メタ）アリルグリシジルエーテル等のエポキシ基含有単量体；炭素数２～１２のモノオレフィン［例えば、エチレン、プロピレン、１－ブテン、１－オクテン及び１－ドデセン等］のモノオレフィン類；塩素、臭素又はヨウ素原子含有単量体、塩化ビニル及び塩化ビニリデンなどのフッ素以外のハロゲン原子含有単量体；アクリル酸、メタクリル酸などの（メタ）アクリル酸；ブタジエン、イソプレンなどの共役二重結合含有単量体などが挙げられる。
　付加重合体として、例えば、エチレン・酢酸ビニル共重合体、スチレン・ブタジエン共重合体又はエチレン・プロピレン共重合体などの共重合体でもよい。また、カルボン酸ビニルエステル重合体は、ポリビニルアルコールなどのように、部分的又は完全にケン化されていてもよい。結着剤はフッ素化合物とフッ素原子を含まないエチレン性二重結合を含む単量体との共重合体であってもよい。 Other examples of the binder include monomer addition polymers containing an ethylenic double bond that does not contain a fluorine atom. Examples of such monomers include (cyclo) alkyl (C1-22) (meth) acrylate [eg, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl] (Meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, octadecyl (meth) acrylate, etc.]; aromatic ring-containing (meth) acrylate [for example, benzyl (Meth) acrylate, phenylethyl (meth) acrylate, etc.]; mono (meth) acrylate of alkylene glycol or dialkylene glycol (alkylene group having 2 to 4 carbon atoms) [for example, 2-hydroxyethyl (meth) acrylate, 2 Hydroxypropyl (meth) acrylate, diethylene glycol mono (meth) acrylate]; (poly) glycerin (degree of polymerization 1 to 4) mono (meth) acrylate; polyfunctional (meth) acrylate [for example, (poly) ethylene glycol (degree of polymerization 1) To 100) di (meth) acrylate, (poly) propylene glycol (degree of polymerization 1 to 100) di (meth) acrylate, 2,2-bis (4-hydroxyethylphenyl) propane di (meth) acrylate, trimethylolpropane tri ( (Meth) acrylate monomers such as (meth) acrylate]; (meth) acrylamides such as (meth) acrylamide, (meth) acrylamide derivatives [eg, N-methylol (meth) acrylamide, diacetone acrylamide, etc.] Acrylamide monomer; Cyano group-containing monomers such as (meth) acrylonitrile, 2-cyanoethyl (meth) acrylate, 2-cyanoethylacrylamide; styrene and styrene derivatives having 7 to 18 carbon atoms [for example, α-methylstyrene, vinyltoluene, p-hydroxystyrene Styrene monomers such as divinylbenzene and the like; diene monomers such as alkadienes having 4 to 12 carbon atoms [for example, butadiene, isoprene, chloroprene and the like]; carboxylic acid (carbon atoms 2 to 12) vinyl esters [ For example, vinyl acetate, vinyl propionate, vinyl butyrate and vinyl octoate, etc.], carboxylic acid (2 to 12 carbon atoms) (meth) allyl ester [for example, (meth) allyl acetate, (meth) allyl propionate and octanoate Alkenyl ester monomers such as (meth) allyl etc.]; Epoxy group-containing monomers such as ricidyl (meth) acrylate and (meth) allyl glycidyl ether; monoolefins having 2 to 12 carbon atoms [for example, ethylene, propylene, 1-butene, 1-octene and 1-dodecene, etc.] Monoolefins; chlorine, bromine or iodine atom-containing monomers, halogen atom-containing monomers other than fluorine such as vinyl chloride and vinylidene chloride; (meth) acrylic acid such as acrylic acid and methacrylic acid; butadiene, isoprene, etc. Examples thereof include a conjugated double bond-containing monomer.
As the addition polymer, for example, a copolymer such as an ethylene / vinyl acetate copolymer, a styrene / butadiene copolymer, or an ethylene / propylene copolymer may be used. Moreover, the carboxylic acid vinyl ester polymer may be partially or completely saponified, such as polyvinyl alcohol. The binder may be a copolymer of a fluorine compound and a monomer containing an ethylenic double bond not containing a fluorine atom.
　結着剤のその他の例示としては、例えば、デンプン、メチルセルロース、カルボキシメチルセルロース、ヒドロキシメチルセルロース、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース、カルボキシメチルヒドロキシエチルセルロース、ニトロセルロースなどの多糖類及びその誘導体；フェノール樹脂；メラミン樹脂；ポリウレタン樹脂；尿素樹脂；ポリアミド樹脂；ポリイミド樹脂；ポリアミドイミド樹脂；石油ピッチ；石炭ピッチなどが挙げられる。 Other examples of the binder include, for example, polysaccharides such as starch, methylcellulose, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, carboxymethylhydroxyethylcellulose, nitrocellulose and derivatives thereof; phenol resin; melamine resin; Polyurethane resin; urea resin; polyamide resin; polyimide resin; polyamideimide resin; petroleum pitch;
　２種以上の結着剤が使用されてもよい。結着剤が増粘する場合には、正極集電体への塗工を容易にするために、可塑剤を使用してもよい。 Two or more binders may be used. When the binder is thickened, a plasticizer may be used in order to facilitate coating on the positive electrode current collector.
　前記の正極に用いられる溶剤としては、例えば、Ｎ－メチル－２－ピロリドンなどの非プロトン性極性溶媒、イソプロピルアルコール、エチルアルコール若しくはメチルアルコールなどのアルコール類、プロピレングリコールジメチルエーテルなどのエーテル類、アセトン、メチルエチルケトン又はメチルイソブチルケトンなどのケトン類などが挙げられる。 Examples of the solvent used for the positive electrode include aprotic polar solvents such as N-methyl-2-pyrrolidone, alcohols such as isopropyl alcohol, ethyl alcohol or methyl alcohol, ethers such as propylene glycol dimethyl ether, acetone, Examples thereof include ketones such as methyl ethyl ketone and methyl isobutyl ketone.
　導電性接着剤とは、例えば導電剤と結着剤との混合物である。溶剤を用いる必要もなく、調製が容易であり、さらに保存性にも優れることから、導電性接着剤は、好ましくはカーボンブラックとポリビニルアルコールとの混合物である。 The conductive adhesive is, for example, a mixture of a conductive agent and a binder. The conductive adhesive is preferably a mixture of carbon black and polyvinyl alcohol because it does not require the use of a solvent, is easy to prepare, and is excellent in storage stability.
　正極合剤の構成材料の配合量は、適宜設定すればよい。結着剤の配合量は、正極活物質１００重量部に対し、通常０．５～３０重量部程度、好ましくは２～３０重量部程度である。導電剤の配合量は、正極活物質１００重量部に対し、通常１～５０重量部程度、好ましくは１～３０重量部程度である。溶剤の配合量は、正極活物質１００重量部に対し、通常５０～５００重量部程度、好ましくは１００～２００重量部程度である。 What is necessary is just to set suitably the compounding quantity of the constituent material of a positive mix. The blending amount of the binder is usually about 0.5 to 30 parts by weight, preferably about 2 to 30 parts by weight with respect to 100 parts by weight of the positive electrode active material. The compounding amount of the conductive agent is usually about 1 to 50 parts by weight, preferably about 1 to 30 parts by weight with respect to 100 parts by weight of the positive electrode active material. The amount of the solvent is usually about 50 to 500 parts by weight, preferably about 100 to 200 parts by weight, per 100 parts by weight of the positive electrode active material.
　前記の正極に用いられる正極集電体としては、例えば、ニッケル、アルミニウム、チタン、銅、金、銀、白金、アルミニウム合金又はステンレス等の金属、例えば、炭素材料、活性炭繊維、ニッケル、アルミニウム、亜鉛、銅、スズ、鉛又はこれらの合金をプラズマ溶射、アーク溶射することによって形成されたもの、例えば、ゴム又はスチレン－エチレン－ブチレン－スチレン共重合体（ＳＥＢＳ）など樹脂に導電剤を分散させた導電性フィルムなどが挙げられる。特に、アルミニウム、ニッケル又はステンレスなどが好ましく、とりわけ、薄膜に加工しやすく、安価であるという点でアルミニウムが好ましい。正極集電体の形状としては、例えば、箔状、平板状、メッシュ状、ネット状、ラス状、パンチングメタル状若しくはエンボス状又はこれらを組み合わせた形状（例えば、メッシュ状平板など）等が挙げられる。正極集電体表面をエッチング処理することにより、該表面に凹凸が形成されてもよい。 Examples of the positive electrode current collector used for the positive electrode include metals such as nickel, aluminum, titanium, copper, gold, silver, platinum, aluminum alloys, and stainless steel, such as carbon materials, activated carbon fibers, nickel, aluminum, and zinc. Copper, tin, lead, or alloys thereof formed by plasma spraying or arc spraying, for example, rubber or resin such as styrene-ethylene-butylene-styrene copolymer (SEBS) dispersed in a conductive agent Examples include conductive films. In particular, aluminum, nickel, stainless steel, and the like are preferable. In particular, aluminum is preferable because it can be easily processed into a thin film and is inexpensive. Examples of the shape of the positive electrode current collector include a foil shape, a flat plate shape, a mesh shape, a net shape, a lath shape, a punching metal shape, an embossed shape, or a combination thereof (for example, a mesh-like flat plate). . By etching the surface of the positive electrode current collector, irregularities may be formed on the surface.
＜負極＞
　本発明において、負極は、ナトリウムイオンでドープされることができかつ脱ドープされることができる。負極は、正極よりも低い電位で、ナトリウムイオンでドープされることができかつ脱ドープされることができる。負極としては、負極活物質、結着剤及び必要に応じて導電剤等を含む負極合剤が、負極集電体に担持された電極が挙げられる。具体的な負極の製造方法としては、負極活物質及び結着剤等に溶剤が添加された負極合剤ペーストを、負極集電体に、ドクターブレード法などで塗工し、得られたシートを乾燥する方法；該集電体を該ペーストに浸漬し、得られたシートを乾燥する方法；負極活物質及び結着剤等に溶剤が添加された混合物を、混練し、成形し、乾燥して得られたシートを、負極集電体に、導電性接着剤等を介して接着して得られた接着シートをプレスし、熱処理乾燥する方法；負極活物質、結着剤及び液状潤滑剤等からなる混合物を負極集電体上に成形し、得られた成形物から液状潤滑剤を除去し、これを一軸又は多軸方向に延伸する方法などが挙げられる。ナトリウム金属またはナトリウム合金それ自体を負極として用いることもできる。負極がシート状である場合、負極の厚みは、通常、５～５００μｍ程度である。負極における結着剤および溶剤としては、正極における前記結着剤および前記溶剤と同じものが挙げられる。溶剤として、水を用いることも可能である。 <Negative electrode>
In the present invention, the negative electrode can be doped with sodium ions and dedoped. The negative electrode can be doped with sodium ions and dedope at a lower potential than the positive electrode. Examples of the negative electrode include an electrode in which a negative electrode active material, a binder, and a negative electrode mixture containing a conductive agent as necessary are supported on a negative electrode current collector. As a specific method for producing a negative electrode, a negative electrode mixture paste in which a solvent is added to a negative electrode active material and a binder is applied to a negative electrode current collector by a doctor blade method or the like. A method of drying; a method of immersing the current collector in the paste; and a method of drying the obtained sheet; a mixture in which a solvent is added to the negative electrode active material and the binder, and the like; A method of pressing an adhesive sheet obtained by adhering the obtained sheet to a negative electrode current collector via a conductive adhesive and drying by heat treatment; from a negative electrode active material, a binder, a liquid lubricant, and the like And a method of removing the liquid lubricant from the obtained molded product and stretching it in a uniaxial or multiaxial direction. Sodium metal or sodium alloy itself can also be used as the negative electrode. When the negative electrode is in sheet form, the thickness of the negative electrode is usually about 5 to 500 μm. Examples of the binder and the solvent in the negative electrode include the same as the binder and the solvent in the positive electrode. Water can also be used as the solvent.
　負極活物質は、ナトリウムイオンでドープされることができかつ脱ドープされることができる。負極活物質の例としては、天然黒鉛、人造黒鉛、コークス類、カーボンブラック、熱分解炭素類、炭素繊維、有機高分子化合物焼成体、難黒鉛化炭素材料などの炭素材料であって、ナトリウムイオンでドープされることができかつ脱ドープされることができる材料を用いることができる。ナトリウム二次電池のレート特性を高める観点では、負極活物質は、好ましくは難黒鉛化炭素材料である。負極活物質として難黒鉛化炭素材料を用いた負極と絶縁性無機多孔層との組み合わせは、ナトリウム二次電池のレート特性を高める観点で、特に優れた組み合わせである。炭素材料の形状としては、例えば、天然黒鉛のような薄片状、メソカーボンマイクロビーズのような球状、黒鉛化炭素繊維のような繊維状、微粉末の凝集体などが挙げられる。負極における導電剤としては、正極における前記導電剤と同じものが挙げられる。負極における炭素材料は、導電剤としての役割を果たす場合もある。 The negative electrode active material can be doped with sodium ions and dedoped. Examples of the negative electrode active material include carbon materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, organic polymer compound fired bodies, non-graphitizable carbon materials, and sodium ions. Materials that can be doped with and dedoped can be used. From the viewpoint of enhancing the rate characteristics of the sodium secondary battery, the negative electrode active material is preferably a non-graphitizable carbon material. The combination of the negative electrode using the non-graphitizable carbon material as the negative electrode active material and the insulating inorganic porous layer is a particularly excellent combination from the viewpoint of enhancing the rate characteristics of the sodium secondary battery. Examples of the shape of the carbon material include flakes such as natural graphite, spheres such as mesocarbon microbeads, fibers such as graphitized carbon fibers, and fine powder aggregates. Examples of the conductive agent in the negative electrode include the same conductive agents as those in the positive electrode. The carbon material in the negative electrode sometimes plays a role as a conductive agent.
　正極における正極活物質が上述のナトリウム無機化合物である場合には、負極活物質として、正極よりも低い電位で、ナトリウムイオンでドープされることができかつ脱ドープされることができる硫化物等のカルコゲン化合物を用いることもできる。硫化物としてはＴｉＳ２、ＺｒＳ２、ＶＳ２、Ｖ２Ｓ５、ＴａＳ２、ＦｅＳ２、ＮｉＳ２、およびＭ６Ｓ２（ただし、Ｍ６は１種以上の遷移金属元素である。）で示される化合物等が挙げられる。 When the positive electrode active material in the positive electrode is the above-mentioned sodium inorganic compound, the negative electrode active material can be doped with sodium ions at a potential lower than that of the positive electrode, and can be undope such as sulfide. Chalcogen compounds can also be used. The sulfide TiS 2, ZrS 2, VS 2 , V 2 S 5, TaS 2, FeS 2, NiS 2, and M 6 S 2 (however, M 6 is at least one transition metal element.) In And the like.
　負極集電体としては、Ｃｕ、Ｎｉ、ステンレスなどを挙げることができ、ナトリウムと合金を作り難い点、薄膜に加工しやすいという点で、Ｃｕが好ましい。負極集電体の形状としては、例えば、箔状、平板状、メッシュ状、ネット状、ラス状、パンチングメタル状若しくはエンボス状又はこれらを組み合わせた形状（例えば、メッシュ状平板など）等が挙げられる。負極集電体表面をエッチング処理することにより、該表面に凹凸が形成されてもよい。 Examples of the negative electrode current collector include Cu, Ni, and stainless steel. Cu is preferable because it is difficult to form an alloy with sodium and it is easy to process into a thin film. Examples of the shape of the negative electrode current collector include a foil shape, a flat plate shape, a mesh shape, a net shape, a lath shape, a punching metal shape, an embossed shape, and a combination thereof (for example, a mesh-like flat plate). . By etching the surface of the negative electrode current collector, irregularities may be formed on the surface.
＜絶縁性無機多孔層＞
　絶縁性無機多孔層は、正極および負極から選ばれる少なくとも一つの電極の表面に形成される。絶縁性無機多孔層は、電極と一体化している。ナトリウム二次電池において、絶縁性無機多孔層は、正極および負極の間に配置され、正極－負極間を絶縁する役割を果たす。絶縁性無機多孔層は、正極および負極の双方の表面に形成されてもよい。絶縁性無機多孔層は、各電極の両面に形成されていてもよい。 <Insulating inorganic porous layer>
The insulating inorganic porous layer is formed on the surface of at least one electrode selected from a positive electrode and a negative electrode. The insulating inorganic porous layer is integrated with the electrode. In the sodium secondary battery, the insulating inorganic porous layer is disposed between the positive electrode and the negative electrode, and plays a role of insulating between the positive electrode and the negative electrode. The insulating inorganic porous layer may be formed on both surfaces of the positive electrode and the negative electrode. The insulating inorganic porous layer may be formed on both surfaces of each electrode.
　このような絶縁性無機多孔層は、ナトリウム二次電池のサイクル性、すなわち、充放電を繰り返した際の放電容量維持率をより高めることができる。絶縁性無機多孔質が正極の表面に形成されている場合には、正極側に存在する電解質、特に後述の非水電解液が加熱されても、正極活物質からのＦｅイオン等の遷移金属元素のイオンの溶出が抑制されることから、遷移金属イオンの錯体化が抑制される。絶縁性無機多孔質が負極の表面に形成されている場合には、正極活物質または電池ケースから、Ｆｅイオン等の遷移金属元素のイオンが溶出したとしても、負極活物質表面への遷移金属元素のイオンの析出が抑制されることから、負極が電気化学的に劣化し難い。これらによって、ナトリウム二次電池のサイクル性をより高めることができる。絶縁性無機多孔質は、好ましくは負極の表面に形成されている。 Such an insulating inorganic porous layer can further improve the cycle performance of the sodium secondary battery, that is, the discharge capacity maintenance rate when charging and discharging are repeated. When the insulating inorganic porous material is formed on the surface of the positive electrode, transition metal elements such as Fe ions from the positive electrode active material even when the electrolyte present on the positive electrode side, particularly the nonaqueous electrolyte described later, is heated. Since the elution of the ions is suppressed, the complexation of transition metal ions is suppressed. When the insulating inorganic porous material is formed on the surface of the negative electrode, even if ions of transition metal elements such as Fe ions are eluted from the positive electrode active material or the battery case, the transition metal element on the surface of the negative electrode active material Therefore, the negative electrode is hardly electrochemically deteriorated. By these, the cycle property of a sodium secondary battery can be improved more. The insulating inorganic porous material is preferably formed on the surface of the negative electrode.
　絶縁性無機多孔層を構成する無機物の例としては、金属酸化物、金属窒化物、金属炭化物、金属水酸化物、炭酸塩、硫酸塩等の無機物の中で、絶縁性を有する無機物が挙げられる。より具体的な例としては、アルミナ、シリカ、二酸化チタン、炭酸カルシウム等などの無機物が挙げられる。無機物は、１種でもよいし、２種以上でもよい。 Examples of inorganic substances constituting the insulating inorganic porous layer include inorganic substances having insulating properties among inorganic substances such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates and sulfates. . More specific examples include inorganic substances such as alumina, silica, titanium dioxide, calcium carbonate and the like. 1 type may be sufficient as an inorganic substance, and 2 or more types may be sufficient as it.
　絶縁性無機多孔層は、スパッタリング法、蒸着法、化学的気相成長（ＣＶＤ）法などの方法を用いて電極の表面に形成することもできるし、無機フィラーおよび結着剤を含有する混合物を電極の表面に塗工する方法により形成することもできる。簡易的な操作で絶縁性無機多孔層を形成することができるので、無機フィラーおよび結着剤を含有する混合物を電極の表面に塗工する方法が好ましい。この場合、得られる絶縁性無機多孔層は、無機フィラーおよび結着剤を含む。無機フィラーおよび結着剤を含有する混合物は、電極の表面に塗工する前に、溶剤に分散または溶解されてもよい。この場合、混合物ペーストが得られる。混合物ペーストを電極の表面に塗工して、得られた塗工電極から、乾燥などにより溶剤を除去して、絶縁性無機多孔層が形成される。 The insulating inorganic porous layer can be formed on the surface of the electrode by using a sputtering method, a vapor deposition method, a chemical vapor deposition (CVD) method or the like, or a mixture containing an inorganic filler and a binder. It can also form by the method of coating on the surface of an electrode. Since the insulating inorganic porous layer can be formed by a simple operation, a method of applying a mixture containing an inorganic filler and a binder to the surface of the electrode is preferable. In this case, the obtained insulating inorganic porous layer contains an inorganic filler and a binder. The mixture containing the inorganic filler and the binder may be dispersed or dissolved in a solvent before being applied to the surface of the electrode. In this case, a mixture paste is obtained. The mixture paste is applied to the surface of the electrode, and the solvent is removed from the obtained coated electrode by drying or the like, whereby an insulating inorganic porous layer is formed.
　絶縁性無機多孔層は、好ましくは無機フィラーおよび結着剤を含む層である。絶縁性無機多孔層が、無機フィラー結着剤を含む場合、絶縁性無機多孔層と電極との結着性が向上し、絶縁性無機多孔層が電極から脱落し難い。特に、絶縁性無機多孔層が無機フィラーおよび結着剤からなる場合には、結着性がより向上する。絶縁性無機多孔層が無機フィラーおよび結着剤からなる場合にも、絶縁性無機多孔層は、塗工の際に用いた溶剤の残存分や結着剤に含まれていた添加成分等の成分を含んでもよい。無機フィラーとしては、金属酸化物、金属窒化物、金属炭化物、金属水酸化物、炭酸塩、硫酸塩等の無機物の中で、絶縁性を有する無機物を含む粉末、例えばこのような無機物を８０重量％以上、９０重量％以上、９５重量％以上、又は９９重量％以上の割合で含む粉末が挙げられる。具体的に例示すると、アルミナ、シリカ、二酸化チタン、炭酸カルシウム等の無機物を含む粉末が挙げられる。無機フィラーは、１種でもよいし、２種以上でもよい。 The insulating inorganic porous layer is preferably a layer containing an inorganic filler and a binder. When the insulating inorganic porous layer contains an inorganic filler binder, the binding property between the insulating inorganic porous layer and the electrode is improved, and the insulating inorganic porous layer is difficult to fall off from the electrode. In particular, when the insulating inorganic porous layer is composed of an inorganic filler and a binder, the binding property is further improved. Even when the insulating inorganic porous layer is composed of an inorganic filler and a binder, the insulating inorganic porous layer is a component such as a residual solvent used in coating or an additive component contained in the binder. May be included. As the inorganic filler, among inorganic substances such as metal oxides, metal nitrides, metal carbides, metal hydroxides, carbonates, sulfates, etc., powder containing an inorganic substance having insulating properties, for example, 80 wt.% Of such inorganic substances % Or more, 90% by weight or more, 95% by weight or more, or 99% by weight or more of the powder. Specific examples include powders containing inorganic substances such as alumina, silica, titanium dioxide, and calcium carbonate. 1 type may be sufficient as an inorganic filler, and 2 or more types may be sufficient as it.
　絶縁性無機多孔層における結着剤および溶剤としては、正極および負極における結着剤および溶剤と同じものが挙げられる。 Examples of the binder and solvent in the insulating inorganic porous layer include the same binder and solvent as in the positive electrode and the negative electrode.
　無機フィラーを構成する無機粒子の平均粒径は、絶縁性無機多孔層の形成のしやすさ、層厚みの制御のしやすさなどを考慮して適宜選択される。無機フィラーを構成する無機粒子の平均粒径は好ましくは０．０１μｍ以上、０．１μｍ以上、又は０．３μｍ以上であって、２μｍ以下、１．５μｍ以下、又は１．０μｍ以下である。無機フィラーを構成する無機粒子の平均粒径が前記範囲であることにより、より均一な層厚みを有する絶縁性無機多孔層が、効率的に形成される。無機フィラーを構成する無機粒子の平均粒径は、レーザー回折式粒度分布測定により決定された体積基準のＤ５０の値である。 The average particle diameter of the inorganic particles constituting the inorganic filler is appropriately selected in consideration of the ease of forming the insulating inorganic porous layer and the ease of controlling the layer thickness. The average particle diameter of the inorganic particles constituting the inorganic filler is preferably 0.01 μm or more, 0.1 μm or more, or 0.3 μm or more, and is 2 μm or less, 1.5 μm or less, or 1.0 μm or less. When the average particle diameter of the inorganic particles constituting the inorganic filler is within the above range, an insulating inorganic porous layer having a more uniform layer thickness is efficiently formed. The average particle diameter of the inorganic particles constituting the inorganic filler is a value of D 50 based on volume as determined by laser diffraction particle size distribution measurement.
　無機フィラーおよび結着剤の合計重量に対する無機フィラーの重量割合は、無機フィラーの平均粒径を考慮して適宜設定すればよい。絶縁性無機多孔層の孔が結着剤で完全に塞がれてしまわないよう留意する必要がある。無機フィラーおよび結着剤の合計重量に対する無機フィラーの重量割合は、好ましくは８０重量％以上、８５重量％以上、９０重量％以上であって、９９重量％以下の範囲である。 The weight ratio of the inorganic filler to the total weight of the inorganic filler and the binder may be appropriately set in consideration of the average particle size of the inorganic filler. Care must be taken not to completely block the pores of the insulating inorganic porous layer with the binder. The weight ratio of the inorganic filler to the total weight of the inorganic filler and the binder is preferably 80% by weight, 85% by weight, 90% by weight, and 99% by weight or less.
　無機フィラーは、好ましくはアルミナを含む。より好ましくは、無機フィラーのアルミナ含有量が、９９．９重量％以上である。アルミナ含有量が、９９．９重量％以上であると、絶縁性無機多孔層の化学的安定性がより一層向上する。無機フィラーは、その一部または全部が、略球状のアルミナ粒子から構成されることが好ましい。 The inorganic filler preferably contains alumina. More preferably, the inorganic filler has an alumina content of 99.9% by weight or more. When the alumina content is 99.9% by weight or more, the chemical stability of the insulating inorganic porous layer is further improved. Part or all of the inorganic filler is preferably composed of substantially spherical alumina particles.
　フィラーの形状としては、略球状、板状、柱状、針状、ウィスカー状、繊維状等が挙げられる。フィラーの形状が、略球状であることにより、絶縁性無機多孔層の孔が、より均一になる。略球状粒子としては、粒子のアスペクト比（粒子の長径／粒子の短径）が１以上１．５以下の範囲の値である粒子が挙げられる。粒子のアスペクト比は、電子顕微鏡写真により決定することができる。 The shape of the filler includes a substantially spherical shape, a plate shape, a column shape, a needle shape, a whisker shape, a fiber shape, and the like. When the shape of the filler is substantially spherical, the pores of the insulating inorganic porous layer become more uniform. Examples of the substantially spherical particles include particles having a particle aspect ratio (particle major axis / particle minor axis) in the range of 1 to 1.5. The aspect ratio of the particles can be determined by an electron micrograph.
　絶縁性無機多孔層の空隙率は、絶縁性無機多孔層の耐熱性、機械的強度、ナトリウムイオン伝導性などを考慮して適宜設定することができる。絶縁性無機多孔層の空隙率は、好ましくは２０体積％以上、又は３０体積％以上であって、８０体積％以下、７０体積％以下、又は６０体積％以下である。絶縁性無機多孔層の空隙率は、以下の式（１）により決定される：
Ｐｖ（％）＝｛（Ｖａ－Ｖｔ）／Ｖａ｝×１００　　　（１）
Ｐｖ（％）は絶縁性無機多孔層の空隙率（体積％）であり、
Ｖａは絶縁性無機多孔層の見かけ体積であり、
Ｖｔは絶縁性無機多孔層の理論体積である。 The porosity of the insulating inorganic porous layer can be appropriately set in consideration of the heat resistance, mechanical strength, sodium ion conductivity, etc. of the insulating inorganic porous layer. The porosity of the insulating inorganic porous layer is preferably 20% by volume or more, or 30% by volume or more, and is 80% by volume or less, 70% by volume or less, or 60% by volume or less. The porosity of the insulating inorganic porous layer is determined by the following formula (1):
Pv (%) = {(Va−Vt) / Va} × 100 (1)
Pv (%) is the porosity (volume%) of the insulating inorganic porous layer,
Va is the apparent volume of the insulating inorganic porous layer,
Vt is the theoretical volume of the insulating inorganic porous layer.
　Ｖａは絶縁性無機多孔層の縦、横、および厚みの値により決定され、Ｖｔは絶縁性無機多孔層の重量、構成材料の重量割合および構成材料それぞれの真比重の値により決定される。 Va is determined by the vertical, horizontal, and thickness values of the insulating inorganic porous layer, and Vt is determined by the weight of the insulating inorganic porous layer, the weight ratio of the constituent material, and the true specific gravity of each constituent material.
　絶縁性無機多孔層の厚みは、０．１μｍ以上、１μｍ以上、又は３μｍ以上であって、１０μｍ以下、又は７μｍ以下であってよく、例えば層の割れ抑制の観点で、好ましくは１～１０μｍである。 The thickness of the insulating inorganic porous layer may be 0.1 μm or more, 1 μm or more, or 3 μm or more, and may be 10 μm or less, or 7 μm or less. For example, from the viewpoint of suppressing cracking of the layer, the thickness is preferably 1 to 10 μm. is there.
＜電解質＞
　電解質は、通常、有機溶媒に溶解されて用いられる。電解質が溶解した有機溶媒は、非水電解液である。 <Electrolyte>
The electrolyte is usually used after being dissolved in an organic solvent. The organic solvent in which the electrolyte is dissolved is a nonaqueous electrolytic solution.
　電解質としては、ＮａＣｌＯ４、ＮａＰＦ６、ＮａＡｓＦ６、ＮａＳｂＦ６、ＮａＢＦ４、ＮａＣＦ３ＳＯ３、ＮａＮ（ＳＯ２ＣＦ３）２、低級脂肪族カルボン酸ナトリウム塩、ＮａＡｌＣｌ４などが挙げられ、２種以上の電解質でもよい。電解質は好ましくはＮａＰＦ６、ＮａＡｓＦ６、ＮａＳｂＦ６、ＮａＢＦ４、ＮａＣＦ３ＳＯ３およびＮａＮ（ＳＯ２ＣＦ３）２からなる群より選ばれる１種以上のフッ素含有リチウム塩である。 Examples of the electrolyte include NaClO 4 , NaPF 6 , NaAsF 6 , NaSbF 6 , NaBF 4 , NaCF 3 SO 3 , NaN (SO 2 CF 3 ) 2 , lower aliphatic carboxylic acid sodium salt, NaAlCl 4, and the like. The above electrolyte may be used. The electrolyte is preferably at least one fluorine-containing lithium salt selected from the group consisting of NaPF 6 , NaAsF 6 , NaSbF 6 , NaBF 4 , NaCF 3 SO 3 and NaN (SO 2 CF 3 ) 2 .
　非水電解液における有機溶媒としては、例えばプロピレンカーボネート、エチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート、イソプロピルメチルカーボネート、ビニレンカーボネート、４－トリフルオロメチル－１，３－ジオキソラン－２－オン、１，２－ジ（メトキシカルボニルオキシ）エタンなどのカーボネート類；１，２－ジメトキシエタン、１，３－ジメトキシプロパン、ペンタフルオロプロピルメチルエーテル、２，２，３，３－テトラフルオロプロピルジフルオロメチルエーテル、テトラヒドロフラン、２－メチルテトラヒドロフランなどのエーテル類；ギ酸メチル、酢酸メチル、γ－ブチロラクトンなどのエステル類；アセトニトリル、ブチロニトリルなどのニトリル類；Ｎ，Ｎ－ジメチルホルムアミド、Ｎ，Ｎ－ジメチルアセトアミドなどのアミド類；３－メチル－２－オキサゾリドンなどのカーバメート類；スルホラン、ジメチルスルホキシド、１，３－プロパンサルトンなどの含硫黄化合物；上記の有機溶媒にさらにフッ素置換基を導入したものが挙げられる。これらのうちの二種以上の有機溶媒を混合して用いてもよい。 Examples of the organic solvent in the non-aqueous electrolyte include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, isopropyl methyl carbonate, vinylene carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, Carbonates such as 1,2-di (methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether , Ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; Amides such as N, N-dimethylformamide and N, N-dimethylacetamide; Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propane sultone; The thing which introduce | transduced the fluorine substituent further into the solvent is mentioned. Two or more of these organic solvents may be mixed and used.
　非水電解液における電解質の濃度は、有機溶媒に対する電解質の溶解度を考慮して、適宜設定すればよい。電解質の濃度は、通常０．１モル（電解質）／Ｌ（非水電解液）～２モル（電解質）／Ｌ（非水電解液）程度であり、好ましくは０．３モル（電解質）／Ｌ（非水電解液）～１．５モル（電解質）／Ｌ（非水電解液）程度である。 The concentration of the electrolyte in the nonaqueous electrolytic solution may be appropriately set in consideration of the solubility of the electrolyte in the organic solvent. The concentration of the electrolyte is usually about 0.1 mol (electrolyte) / L (non-aqueous electrolyte) to 2 mol (electrolyte) / L (non-aqueous electrolyte), preferably 0.3 mol (electrolyte) / L. (Nonaqueous electrolyte) to about 1.5 mol (electrolyte) / L (nonaqueous electrolyte).
＜セパレータ＞
　セパレータは、樹脂から構成される多孔質フィルムを含む。本発明のナトリウム二次電池は、セパレータを備えなくとも、二次電池として十分に機能する。セパレータは、通常、正極と負極の間に配置される。本発明のナトリウム二次電池は、セパレータをさらに備えることにより、正極－負極間の短絡等が原因で電池内に異常電流が流れた際に、電流を遮断して、過大電流が流れることを阻止するシャットダウン機能を持つことができる。 <Separator>
The separator includes a porous film made of resin. The sodium secondary battery of the present invention functions sufficiently as a secondary battery even without a separator. The separator is usually disposed between the positive electrode and the negative electrode. The sodium secondary battery of the present invention further includes a separator to cut off the current and prevent an excessive current from flowing when an abnormal current flows in the battery due to a short circuit between the positive electrode and the negative electrode. Can have a shutdown function.
　多孔質フィルムを構成する樹脂は、前記有機溶媒に溶解しないものを選択すればよい。樹脂の例として、具体的には、ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂、熱可塑性ポリウレタン樹脂が挙げられる。これらの２種以上の樹脂が混合されてもよい。多孔質フィルムがより低温で軟化してシャットダウンする観点で、多孔質フィルムは、好ましくはポリオレフィン樹脂を含有し、より好ましくはポリエチレンを含有する。ポリエチレンの例として、具体的には、低密度ポリエチレン、高密度ポリエチレン、線状ポリエチレン等が挙げられ、超高分子量ポリエチレンも挙げられる。多孔質フィルムの突刺し強度をより高める観点では、多孔質フィルムは、好ましくは超高分子量ポリエチレンを含有する。多孔質フィルムを容易に製造する観点では、多孔質フィルムは、好ましくは低分子量（重量平均分子量１万以下）のポリオレフィンからなるワックスを含有する。多孔質フィルムの厚みは、通常３～３０μｍであり、好ましくは３～２０μｍである。 As the resin constituting the porous film, a resin that does not dissolve in the organic solvent may be selected. Specific examples of the resin include polyolefin resins such as polyethylene and polypropylene, and thermoplastic polyurethane resins. These two or more kinds of resins may be mixed. From the viewpoint of the porous film softening and shutting down at a lower temperature, the porous film preferably contains a polyolefin resin, and more preferably contains polyethylene. Specific examples of polyethylene include low density polyethylene, high density polyethylene, linear polyethylene, and the like, and ultrahigh molecular weight polyethylene is also included. From the viewpoint of further increasing the puncture strength of the porous film, the porous film preferably contains ultrahigh molecular weight polyethylene. From the viewpoint of easily producing the porous film, the porous film preferably contains a wax made of polyolefin having a low molecular weight (weight average molecular weight of 10,000 or less). The thickness of the porous film is usually 3 to 30 μm, preferably 3 to 20 μm.
　セパレータは、多孔質フィルムの片面または両面に耐熱多孔層が積層された積層フィルムでもよい。積層フィルムの厚みとしては、通常４０μｍ以下、好ましくは、２０μｍ以下である。耐熱多孔層の合計厚みをＡ（μｍ）、多孔質フィルムの厚みをＢ（μｍ）としたとき、Ａ／Ｂの値が、０以上１以下であることが好ましい。耐熱多孔層は、耐熱樹脂を含有してもよい。耐熱樹脂の例としては、ポリアミド、ポリイミド、ポリアミドイミド、ポリカーボネート、ポリアセタール、ポリサルホン、ポリフェニレンサルファイド、ポリエーテルケトン、芳香族ポリエステル、ポリエーテルサルホン、ポリエーテルイミドなどが挙げられる。耐熱性をより高める観点で、耐熱樹脂は、好ましくはポリアミド、ポリイミド、ポリアミドイミド、ポリエーテルサルホン、ポリエーテルイミドであり、より好ましくはポリアミド、ポリイミド、ポリアミドイミドであり、さらにより好ましくは芳香族ポリアミド（パラ配向芳香族ポリアミド、メタ配向芳香族ポリアミド）、芳香族ポリイミド、芳香族ポリアミドイミド等の含窒素芳香族重合体である。耐熱樹脂として、ポリ－４－メチルペンテン－１、環状オレフィン系重合体を挙げることもできる。耐熱多孔層は、フィラーを含有することもできる。フィラーは、有機粉末、無機粉末またはこれらの混合物であってもよい。フィラーを構成する粒子の平均粒径は、好ましくは０．０１μｍ以上１μｍ以下である。 The separator may be a laminated film in which a heat-resistant porous layer is laminated on one side or both sides of a porous film. The thickness of the laminated film is usually 40 μm or less, preferably 20 μm or less. When the total thickness of the heat resistant porous layer is A (μm) and the thickness of the porous film is B (μm), the value of A / B is preferably 0 or more and 1 or less. The heat resistant porous layer may contain a heat resistant resin. Examples of the heat resistant resin include polyamide, polyimide, polyamideimide, polycarbonate, polyacetal, polysulfone, polyphenylene sulfide, polyetherketone, aromatic polyester, polyethersulfone, polyetherimide, and the like. From the viewpoint of further improving heat resistance, the heat resistant resin is preferably polyamide, polyimide, polyamideimide, polyethersulfone, polyetherimide, more preferably polyamide, polyimide, polyamideimide, and even more preferably aromatic. Nitrogen-containing aromatic polymers such as polyamide (para-oriented aromatic polyamide, meta-oriented aromatic polyamide), aromatic polyimide, aromatic polyamideimide and the like. Examples of the heat resistant resin include poly-4-methylpentene-1 and cyclic olefin polymers. The heat resistant porous layer can also contain a filler. The filler may be an organic powder, an inorganic powder, or a mixture thereof. The average particle diameter of the particles constituting the filler is preferably 0.01 μm or more and 1 μm or less.
　本発明のナトリウム二次電池において、絶縁性無機多孔層は、正極および負極の間に配置される。本発明のナトリウム二次電池は、正極、絶縁性無機多孔層、負極の順となるように積層、または積層かつ巻回することによって電極群を得て、この電極群を電池缶などの電池ケース内に収納し、該ケース内に非水電解液を注入することによって、製造することができる。本発明のナトリウム二次電池がセパレータを有する場合には、セパレータは、正極に形成された絶縁性無機多孔層－負極間、正極－負極に形成された絶縁性無機多孔層間、または正極に形成された絶縁性無機多孔層－負極に形成された絶縁性無機多孔層間に配置される。 In the sodium secondary battery of the present invention, the insulating inorganic porous layer is disposed between the positive electrode and the negative electrode. The sodium secondary battery of the present invention is obtained by laminating or laminating and winding a positive electrode, an insulating inorganic porous layer, and a negative electrode in this order, and this electrode group is obtained as a battery case such as a battery can. It can be manufactured by storing it in and injecting a non-aqueous electrolyte into the case. When the sodium secondary battery of the present invention has a separator, the separator is formed between the insulating inorganic porous layer formed on the positive electrode and the negative electrode, the insulating inorganic porous layer formed on the positive electrode and the negative electrode, or the positive electrode. The insulating inorganic porous layer is disposed between the insulating inorganic porous layer formed on the negative electrode.
　電極群の形状としては例えば、この電極群を巻回の軸と垂直方向に切断したときの断面が、円、楕円、長方形、角がとれたような長方形等となるような形状が挙げられる。二次電池の形状としては、例えば、ペーパー型、コイン型、円筒型、角型などの形状が挙げられる。 Examples of the shape of the electrode group include a shape in which a cross section when the electrode group is cut in a direction perpendicular to the winding axis is a circle, an ellipse, a rectangle, a rectangle with rounded corners, or the like. Examples of the shape of the secondary battery include a paper shape, a coin shape, a cylindrical shape, and a square shape.
　以下、本発明を実施例により、さらに詳細に説明する。 Hereinafter, the present invention will be described in more detail with reference to examples.
比較例１
（１）正極の作製
　炭酸ナトリウム（Ｎａ２ＣＯ３：和光純薬工業株式会社製：純度９９．８％）、酸化マンガン（ＩＶ）（ＭｎＯ２：株式会社高純度化学研究所製：純度９９．９％）、酸化鉄（ＩＩ、ＩＩＩ）（Ｆｅ３Ｏ４：株式会社高純度化学研究所製：純度９９％）、および酸化ニッケル（ＩＩ）（ＮｉＯ：株式会社高純度化学研究所製：純度９９％）を、Ｎａ：Ｍｎ：Ｆｅ：Ｎｉのモル比が０．８：０．３３３：０．３３３：０．３３３となるように秤量し、乾式ボールミルで４時間にわたって混合して混合物を得た。得られた混合物を、アルミナボートに充填し、電気炉を用いて空気雰囲気下で８００℃で２時間にわたって焼成して、ナトリウム無機化合物Ｃ１を得た。導電剤としてアセチレンブラック（電気化学工業株式会社製）を用い、結着剤としてＰＶｄＦ（株式会社クレハ製、ＰｏｌｙＶｉｎｙｌｉｄｅｎｅＤｉＦｌｕｏｒｉｄｅ）を用いた。ナトリウム無機化合物Ｃ１、導電剤、および結着剤を、ナトリウム無機化合物Ｃ１：導電剤：結着剤＝８５：１０：５の重量比となるように秤量した。秤量されたナトリウム無機化合物Ｃ１と秤量された導電剤をメノウ乳鉢で十分に混合した。得られた混合物に、Ｎ－メチル－２－ピロリドン（ＮＭＰ：東京化成工業株式会社製）を適量加え、さらにＰＶｄＦを加えて引き続き均一になるように混合して、ペーストを得た。得られたペーストを、集電体である厚さ４０μｍのアルミ箔上に、アプリケータを用いて１００μｍの厚さで塗工し、得られた塗工集電体を乾燥機に入れ、ＮＭＰを除去させながら、十分に乾燥することによって正極シートを得た。この正極シートを電極打ち抜き機で直径１．５ｃｍに打ち抜いた後、ハンドプレスにて十分に圧着し、直径１．５ｃｍの円状の正極Ｃ１を得た。 Comparative Example 1
(1) Preparation of positive electrode Sodium carbonate (Na 2 CO 3 : Wako Pure Chemical Industries, Ltd .: purity 99.8%), manganese oxide (IV) (MnO 2 : manufactured by Kojundo Chemical Laboratory Co., Ltd .: purity 99. 9%), iron oxide (II, III) (Fe 3 O 4 : manufactured by Kojundo Chemical Laboratory Co., Ltd .: purity 99%), and nickel oxide (IIO) (NiO: manufactured by Kojundo Chemical Laboratory Co., Ltd .: purity) 99%) to a molar ratio of Na: Mn: Fe: Ni of 0.8: 0.333: 0.333: 0.333 and mixed for 4 hours in a dry ball mill to obtain a mixture. It was. The obtained mixture was filled in an alumina boat and baked at 800 ° C. for 2 hours in an air atmosphere using an electric furnace to obtain a sodium inorganic compound C1. Acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) was used as the conductive agent, and PVdF (manufactured by Kureha Co., Ltd., PolyVinylideneDiFluoride) was used as the binder. The sodium inorganic compound C1, the conductive agent, and the binder were weighed so as to have a weight ratio of sodium inorganic compound C1: conductive agent: binder = 85: 10: 5. The weighed sodium inorganic compound C1 and the weighed conductive agent were sufficiently mixed in an agate mortar. An appropriate amount of N-methyl-2-pyrrolidone (NMP: manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added to the obtained mixture, and PVdF was further added and mixed uniformly to obtain a paste. The obtained paste was applied to an aluminum foil with a thickness of 40 μm, which is a current collector, with a thickness of 100 μm using an applicator, and the obtained current collector was put into a drier to remove NMP. While removing, a positive electrode sheet was obtained by sufficiently drying. This positive electrode sheet was punched to a diameter of 1.5 cm using an electrode punching machine, and then sufficiently pressed by a hand press to obtain a circular positive electrode C1 having a diameter of 1.5 cm.
（２）電池の作製
　コインセル（宝泉株式会社製）の下側パーツの窪みに、アルミ箔を下に向けて正極Ｃ１を置き、非水電解液としての１ＭのＮａＣｌＯ４／プロピレンカーボネート、セパレータとしてのポリプロピレン多孔質膜（厚み２０μｍ）、負極としての金属ナトリウム（アルドリッチ社製）、およびコインセルの上側パーツを組み合わせて、ナトリウム二次電池Ｃ１を作製した。試験電池の組み立てはアルゴン雰囲気のグローブボックス内で行った。 (2) Production of battery In the depression of the lower part of the coin cell (manufactured by Hosen Co., Ltd.), the positive electrode C1 is placed with the aluminum foil facing downward, and 1M NaClO 4 / propylene carbonate as a non-aqueous electrolyte, as a separator A sodium secondary battery C1 was fabricated by combining the polypropylene porous membrane (thickness 20 μm), metallic sodium (manufactured by Aldrich) as the negative electrode, and the upper part of the coin cell. The test battery was assembled in a glove box in an argon atmosphere.
　以下の条件で、ナトリウム二次電池の定電流充放電試験を実施した。 The constant current charge / discharge test of the sodium secondary battery was performed under the following conditions.
　充放電条件：
　充電は、４．０Ｖまで０．１Ｃレート（１０時間で完全充電する速度）でＣＣ（コンスタントカレント：定電流）充電を行った。放電は、該充電速度と同じ速度で、ＣＣ放電を行い、電圧１．５Ｖでカットオフした。次サイクル以降の充電、放電は、該充電速度と同じ速度で行い、１サイクル目と同様に、充電電圧４．０Ｖ、放電電圧１．５Ｖでカットオフした。充放電試験は、計１０サイクル行った。 Charging / discharging conditions:
Charging was performed by CC (Constant Current: constant current) at a rate of 0.1 C up to 4.0 V (speed of complete charging in 10 hours). For discharging, CC discharging was performed at the same speed as the charging speed, and cut off at a voltage of 1.5V. Charging and discharging after the next cycle were performed at the same rate as the charging rate, and cut off at a charging voltage of 4.0 V and a discharging voltage of 1.5 V as in the first cycle. The charge / discharge test was performed for 10 cycles in total.
　上記充放電条件で、ナトリウム二次電池Ｃ１の定電流充放電試験を行ったところ、各サイクル間において、放電容量のバラツキ、すなわち、サイクルが増えるにつれて放電容量が単調減少せずに、放電容量が一時的に増大し、その後のサイクルで減少する現象が認められた。 When the constant current charge / discharge test of the sodium secondary battery C1 was performed under the above charge / discharge conditions, the discharge capacity varied between cycles, that is, the discharge capacity did not monotonously decrease as the number of cycles increased, A phenomenon was observed that increased temporarily and decreased in subsequent cycles.
実施例１
（１）正極の作製
　比較例１と同様にして、正極Ｃ１を作製した。次いで、無機フィラーとしてのアルミナ（平均粒径０．５μｍ、住友化学株式会社製、製品名ＡＫＰ－３０００、アルミナ含有量９９．９９重量％以上）と、ＰＶｄＦとを、無機フィラー：ＰＶｄＦの重量比が９９：１になるように秤量し、混合し、混合物を得た。混合物にＮＭＰを添加して混合物ペーストを作製し、このペーストを正極Ｃ１の表面に塗工し、塗工電極を得て、６０℃で２時間乾燥して、正極Ｃ１の表面に絶縁性無機多孔層を形成し、正極Ｅ１を得た。絶縁性無機多孔層の厚みは５μｍであり、絶縁性無機多孔層の空隙率は４８体積％であった。 Example 1
(1) Production of positive electrode A positive electrode C1 was produced in the same manner as in Comparative Example 1. Next, alumina as an inorganic filler (average particle size 0.5 μm, manufactured by Sumitomo Chemical Co., Ltd., product name AKP-3000, alumina content of 99.99% by weight or more) and PVdF are combined, and the inorganic filler: PVdF weight ratio. Was weighed to 99: 1 and mixed to obtain a mixture. NMP is added to the mixture to prepare a mixture paste, and this paste is applied to the surface of the positive electrode C1 to obtain a coated electrode, which is dried at 60 ° C. for 2 hours, and an insulating inorganic porous material is formed on the surface of the positive electrode C1. A layer was formed to obtain a positive electrode E1. The thickness of the insulating inorganic porous layer was 5 μm, and the porosity of the insulating inorganic porous layer was 48% by volume.
（２）電池の作製
　コインセル（宝泉株式会社製）の下側パーツの窪みに、アルミ箔を下に向けて正極Ｅ１を置き、非水電解液としての１ＭのＮａＣｌＯ４／プロピレンカーボネート、セパレータとしてのポリプロピレン多孔質膜（厚み２０μｍ）、負極としての金属ナトリウム（アルドリッチ社製）、およびコインセルの上側パーツを組み合わせて、ナトリウム二次電池Ｅ１を作製した。試験電池の組み立てはアルゴン雰囲気のグローブボックス内で行った。 (2) Production of battery In the depression of the lower part of the coin cell (made by Hosen Co., Ltd.), the positive electrode E1 is placed with the aluminum foil facing downward, and 1M NaClO 4 / propylene carbonate as a non-aqueous electrolyte, as a separator A polypropylene secondary membrane (thickness 20 μm), metallic sodium (manufactured by Aldrich) as a negative electrode, and the upper part of a coin cell were combined to produce a sodium secondary battery E1. The test battery was assembled in a glove box in an argon atmosphere.
　上記充放電条件で、ナトリウム二次電池Ｅ１の定電流充放電試験を行ったところ、各サイクル間において、放電容量のバラツキが認められず、ナトリウム二次電池Ｅ１は、充放電挙動の安定性に優れていることを確認した。 When the constant current charge / discharge test of the sodium secondary battery E1 was performed under the above charge / discharge conditions, no variation in discharge capacity was observed between cycles, and the sodium secondary battery E1 was stable in charge / discharge behavior. It was confirmed that it was excellent.
実施例２
（１）正極の作製
　実施例１と同様にして、正極Ｅ１を作製した。 Example 2
(1) Production of positive electrode A positive electrode E1 was produced in the same manner as in Example 1.
（２）負極の作製
　レゾルシノール２００ｇ、メチルアルコール１．５Ｌ、ベンズアルデヒド１９４ｇを、窒素気流下で四つ口フラスコに入れ氷冷し、攪拌しながら、３６％塩酸３６．８ｇを滴下した。滴下終了後、これらを６５℃に昇温し、その後同温度で５時間保温した。得られた重合反応混合物に水１Ｌを加え、沈殿を濾取し、濾液が中性になるまで水で洗浄し、乾燥して、有機高分子化合物であるテトラフェニルカリックス［４］レゾルシナレーン（ＰＣＲＡ）２９４ｇを得た。ＰＣＲＡを、ロータリーキルン内に入れ、雰囲気を空気雰囲気として、３００℃で１時間加熱し、次いでロータリーキルンの雰囲気をアルゴンに置換して、１０００℃で４時間焼成した。次いで、ボールミル（メノウ製ボール、２８ｒｐｍ、５分間）で粉砕することによって有機高分子化合物焼成体である炭素材料Ｅ２を得た。炭素材料Ｅ２と結着剤としてのＰＶｄＦとを、炭素材料Ｅ２：結着剤＝９５：５の重量比となるように秤量した。結着剤をＮＭＰに溶解した後、炭素材料Ｅ２を加えて、ペーストを得た。得られたペーストを、集電体である厚さ１０μｍの銅箔上に、アプリケータを用いて１００μｍの厚さで塗工し、得られた塗工集電体を乾燥機に入れ、ＮＭＰを除去させながら、十分に乾燥することによって負極シートを得た。この負極シートを電極打ち抜き機で直径１．５ｃｍに打ち抜いた後、ハンドプレスにて十分に圧着し、直径１．５ｃｍの円状の負極Ｅ２を得た。 (2) Production of negative electrode 200 g of resorcinol, 1.5 L of methyl alcohol and 194 g of benzaldehyde were placed in a four-necked flask under a nitrogen stream and cooled with ice, and 36.8 g of 36% hydrochloric acid was added dropwise with stirring. After completion of dropping, these were heated to 65 ° C. and then kept at the same temperature for 5 hours. 1 L of water was added to the resulting polymerization reaction mixture, the precipitate was collected by filtration, washed with water until the filtrate became neutral, dried, and then the organic polymer compound tetraphenylcalix [4] resorcinarene (PCRA). 294 g was obtained. The PCRA was placed in a rotary kiln and heated at 300 ° C. for 1 hour under an air atmosphere. Then, the atmosphere of the rotary kiln was replaced with argon and baked at 1000 ° C. for 4 hours. Subsequently, the carbon material E2 which is a baking body of an organic polymer compound was obtained by grind | pulverizing with a ball mill (Agate ball, 28 rpm, 5 minutes). Carbon material E2 and PVdF as a binder were weighed so as to have a weight ratio of carbon material E2: binder = 95: 5. After the binder was dissolved in NMP, carbon material E2 was added to obtain a paste. The obtained paste is applied to a copper foil having a thickness of 10 μm, which is a current collector, with a thickness of 100 μm using an applicator, and the obtained current collector is put into a dryer, and NMP is added. The negative electrode sheet was obtained by fully drying while removing. This negative electrode sheet was punched to a diameter of 1.5 cm using an electrode punching machine, and then sufficiently pressed by a hand press to obtain a circular negative electrode E2 having a diameter of 1.5 cm.
（３）電池の作製
　コインセル（宝泉株式会社製）の下側パーツの窪みに、アルミ箔を下に向けて正極Ｅ１を置き、非水電解液としての１ＭのＮａＣｌＯ４／プロピレンカーボネート、セパレータとしてのポリプロピレン多孔質膜（厚み２０μｍ）、銅箔を上に向けた負極Ｅ２、およびコインセルの上側パーツを組み合わせて、ナトリウム二次電池Ｅ２を作製した。試験電池の組み立てはアルゴン雰囲気のグローブボックス内で行った。 (3) Production of battery In the recess of the lower part of the coin cell (made by Hosen Co., Ltd.), the positive electrode E1 is placed with the aluminum foil facing down, and 1M NaClO 4 / propylene carbonate as a non-aqueous electrolyte, as a separator A sodium secondary battery E2 was produced by combining the polypropylene porous membrane (thickness 20 μm), the negative electrode E2 with the copper foil facing upward, and the upper part of the coin cell. The test battery was assembled in a glove box in an argon atmosphere.
　上記充放電条件で、ナトリウム二次電池Ｅ２の定電流充放電試験を行ったところ、各サイクル間において、放電容量のバラツキが認められず、ナトリウム二次電池Ｅ２は、充放電挙動の安定性に優れていることを確認した。 When the constant current charge / discharge test of the sodium secondary battery E2 was performed under the above charge / discharge conditions, no variation in discharge capacity was observed between the cycles, and the sodium secondary battery E2 was stable in charge / discharge behavior. It was confirmed that it was excellent.
実施例３
（１）正極の作製
　比較例１と同様にして、正極Ｃ１を作製した。 Example 3
(1) Production of positive electrode A positive electrode C1 was produced in the same manner as in Comparative Example 1.
（２）負極の作製
　実施例２と同様にして、負極Ｅ２を作製した。次いで、無機フィラーとしてのアルミナ（平均粒径０．５μｍ、住友化学株式会社製、製品名ＡＫＰ－３０００、アルミナ含有量９９．９９重量％以上）と、ＰＶｄＦとを、無機フィラー：ＰＶｄＦの重量比が９９：１になるように秤量し、混合し、混合物を得た。混合物にＮＭＰを添加して混合物ペーストを作製し、このペーストを負極Ｅ２の表面に塗工し、塗工電極を得て、６０℃で２時間乾燥して、負極Ｅ２の表面に絶縁性無機多孔層を形成し、負極Ｅ３を得た。絶縁性無機多孔層の厚みは５μｍであり、絶縁性無機多孔層の空隙率は４８体積％であった。 (2) Production of negative electrode A negative electrode E2 was produced in the same manner as in Example 2. Next, alumina as an inorganic filler (average particle size 0.5 μm, manufactured by Sumitomo Chemical Co., Ltd., product name AKP-3000, alumina content of 99.99% by weight or more) and PVdF are combined, and the inorganic filler: PVdF weight ratio. Was weighed to 99: 1 and mixed to obtain a mixture. NMP is added to the mixture to prepare a mixture paste, and this paste is applied to the surface of the negative electrode E2 to obtain a coated electrode, which is dried at 60 ° C. for 2 hours, and an insulating inorganic porous material is formed on the surface of the negative electrode E2. A layer was formed to obtain a negative electrode E3. The thickness of the insulating inorganic porous layer was 5 μm, and the porosity of the insulating inorganic porous layer was 48% by volume.
（３）電池の作製
　コインセル（宝泉株式会社製）の下側パーツの窪みに、アルミ箔を下に向けて正極Ｃ１を置き、非水電解液としての１ＭのＮａＣｌＯ４／プロピレンカーボネート、セパレータとしてのポリプロピレン多孔質膜（厚み２０μｍ）、銅箔を上に向けた負極Ｅ３、およびコインセルの上側パーツを組み合わせて、ナトリウム二次電池Ｅ３を作製した。試験電池の組み立てはアルゴン雰囲気のグローブボックス内で行った。 (3) Production of battery In the recess of the lower part of the coin cell (made by Hosen Co., Ltd.), the positive electrode C1 is placed with the aluminum foil facing downward, and 1M NaClO 4 / propylene carbonate as a non-aqueous electrolyte, as a separator A sodium secondary battery E3 was prepared by combining the polypropylene porous film (thickness 20 μm), the negative electrode E3 with the copper foil facing upward, and the upper part of the coin cell. The test battery was assembled in a glove box in an argon atmosphere.
　上記充放電条件で、ナトリウム二次電池Ｅ３の定電流充放電試験を行ったところ、各サイクル間において、放電容量のバラツキが認められず、ナトリウム二次電池Ｅ３は、充放電挙動の安定性に優れていることを確認した。 When the constant current charge / discharge test of the sodium secondary battery E3 was performed under the above charge / discharge conditions, no variation in discharge capacity was observed between the cycles, and the sodium secondary battery E3 was stable in charge / discharge behavior. It was confirmed that it was excellent.

Claims (10)

  1. 　ナトリウムイオンでドープされることができかつ脱ドープされることができる正極と、ナトリウムイオンでドープされることができかつ脱ドープされることができる負極と、電解質とを備え、かつ
    　前記正極および前記負極から選ばれる少なくとも一つの電極の表面に、絶縁性無機多孔層が形成されている、
    ナトリウム二次電池。     A positive electrode that can be doped with sodium ions and can be undope; a negative electrode that can be doped with sodium ions and that can be undope; and an electrolyte; and An insulating inorganic porous layer is formed on the surface of at least one electrode selected from the negative electrode,
    Sodium secondary battery.
  2. 　前記絶縁性無機多孔層が、無機フィラーおよび結着剤を含む請求項１記載のナトリウム二次電池。 The sodium secondary battery according to claim 1, wherein the insulating inorganic porous layer includes an inorganic filler and a binder.
  3. 　前記無機フィラーは、平均粒径が０．０１～２μｍの無機粒子から構成される請求項２記載のナトリウム二次電池。 The sodium secondary battery according to claim 2, wherein the inorganic filler is composed of inorganic particles having an average particle diameter of 0.01 to 2 µm.
  4. 　前記無機フィラーおよび前記結着剤の合計重量に対する前記無機フィラーの重量割合が、８０～９９重量％である請求項２または３記載のナトリウム二次電池。 The sodium secondary battery according to claim 2 or 3, wherein a weight ratio of the inorganic filler to a total weight of the inorganic filler and the binder is 80 to 99% by weight.
  5. 　前記無機フィラーが、アルミナを含む請求項２～４のいずれかに記載のナトリウム二次電池。 The sodium secondary battery according to any one of claims 2 to 4, wherein the inorganic filler contains alumina.
  6. 　前記無機フィラーのアルミナ含有量が、９９．９重量％以上である請求項５記載のナトリウム二次電池。 The sodium secondary battery according to claim 5, wherein the inorganic filler has an alumina content of 99.9% by weight or more.
  7. 　前記絶縁性無機多孔層の空隙率が、２０～８０体積％である請求項１～６のいずれかに記載のナトリウム二次電池。 The sodium secondary battery according to any one of claims 1 to 6, wherein the porosity of the insulating inorganic porous layer is 20 to 80% by volume.
  8. 　前記絶縁性無機多孔層の厚みが、１～１０μｍである請求項１～７のいずれかに記載のナトリウム二次電池。 The sodium secondary battery according to any one of claims 1 to 7, wherein the insulating inorganic porous layer has a thickness of 1 to 10 袖 m.
  9. 　前記正極が、正極活物質として、ナトリウムと遷移金属との複合酸化物、又は遷移金属カルコゲン化物を含む、請求項１～８のいずれかに記載のナトリウム二次電池。 The sodium secondary battery according to any one of claims 1 to 8, wherein the positive electrode contains, as a positive electrode active material, a composite oxide of sodium and transition metal or a transition metal chalcogenide.
  10. 　セパレータをさらに備える請求項１～９のいずれかに記載のナトリウム二次電池。 The sodium secondary battery according to any one of claims 1 to 9, further comprising a separator.
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JP2015076120A (en) * 2013-10-04 2015-04-20 トヨタ自動車株式会社 Nonaqueous electrolyte secondary battery
WO2023115431A1 (en) * 2021-12-23 2023-06-29 宁德时代新能源科技股份有限公司 Secondary battery

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JP6587157B2 (en) * 2017-02-07 2019-10-09 エルジー ケム． エルティーディ． Electrode assembly and electrochemical device including the same
WO2018180145A1 (en) * 2017-03-28 2018-10-04 日本電気株式会社 Secondary battery and manufacturing method thereof

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JP2009209037A (en) * 2008-02-06 2009-09-17 Sumitomo Chemical Co Ltd Composite metal oxide and sodium secondary battery
JP2009209038A (en) * 2008-02-06 2009-09-17 Sumitomo Chemical Co Ltd Composite metal oxide and sodium secondary battery
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JP2009209037A (en) * 2008-02-06 2009-09-17 Sumitomo Chemical Co Ltd Composite metal oxide and sodium secondary battery
JP2009209038A (en) * 2008-02-06 2009-09-17 Sumitomo Chemical Co Ltd Composite metal oxide and sodium secondary battery
JP2009224320A (en) * 2008-02-18 2009-10-01 Sumitomo Chemical Co Ltd Sodium secondary battery

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2015076120A (en) * 2013-10-04 2015-04-20 トヨタ自動車株式会社 Nonaqueous electrolyte secondary battery
WO2023115431A1 (en) * 2021-12-23 2023-06-29 宁德时代新能源科技股份有限公司 Secondary battery

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