WO2015072577A1 - Sodium-ion battery - Google Patents

Sodium-ion battery Download PDF

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Publication number
WO2015072577A1
WO2015072577A1 PCT/JP2014/080564 JP2014080564W WO2015072577A1 WO 2015072577 A1 WO2015072577 A1 WO 2015072577A1 JP 2014080564 W JP2014080564 W JP 2014080564W WO 2015072577 A1 WO2015072577 A1 WO 2015072577A1
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WIPO (PCT)
Prior art keywords
sodium
aqueous electrolyte
secondary battery
positive electrode
aqueous
Prior art date
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PCT/JP2014/080564
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French (fr)
Japanese (ja)
Inventor
淳一 影浦
山口　滝太郎
Original Assignee
住友化学株式会社
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Application filed by 住友化学株式会社 filed Critical 住友化学株式会社
Priority to JP2015547819A priority Critical patent/JP6420252B2/en
Publication of WO2015072577A1 publication Critical patent/WO2015072577A1/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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a sodium secondary battery.
  • a sodium secondary battery using a non-aqueous electrolyte is suitable as a battery having a high energy density because it can generate a higher voltage than a battery of an aqueous electrolyte. Moreover, since sodium is an abundant and inexpensive material, it is expected that large-scale power can be supplied in large quantities by putting it into practical use.
  • a sodium secondary battery usually includes at least a pair of electrodes, a positive electrode including a positive electrode active material capable of doping and dedoping sodium ions, and a negative electrode including a negative electrode active material capable of doping and dedoping sodium ions. And an electrolyte.
  • Non-aqueous electrolyte is mentioned as an electrolyte used for a sodium secondary battery.
  • a non-aqueous electrolyte a sodium secondary battery using a non-aqueous electrolyte in which an electrolyte salt composed of sodium hexafluorophosphate is dissolved in a non-aqueous solvent composed of a saturated cyclic carbonate such as propylene carbonate is known. (JP 2007-35283 A).
  • an object of the present invention is to provide a sodium secondary battery excellent in charge / discharge cycle characteristics when charged at a relatively high speed.
  • a positive electrode having a positive electrode active material that can be doped and dedoped with sodium ions, a negative electrode having a negative electrode active material that can be doped and dedoped with sodium ions, a nonaqueous solvent, and saturation to the nonaqueous solvent A sodium secondary battery having a non-aqueous electrolyte containing a sodium salt in an amount exceeding the solubility is provided.
  • a sodium secondary battery excellent in charge / discharge cycle characteristics when charged at a relatively high speed that is, at a relatively large current value.
  • a sodium secondary battery excellent in output characteristics can be provided.
  • the sodium secondary battery of the present invention has a positive electrode having a positive electrode active material that can be doped and dedoped with sodium ions, a negative electrode having a negative electrode active material that can be doped and dedoped with sodium ions, and a non-aqueous electrolyte. Usually, it further has a separator.
  • a sodium secondary battery usually contains a laminate in which a negative electrode, a separator and a positive electrode are stacked, and an electrode group obtained by winding or folding the laminate in a battery can or an aluminum laminate pack, and a non-aqueous electrolyte. Can be manufactured by impregnating the electrode group.
  • 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.
  • the shape can be raised.
  • examples of the shape of the battery include a paper shape, a coin shape, a cylindrical shape, and a square shape.
  • the non-aqueous electrolyte used in the sodium secondary battery of the present invention is a non-aqueous electrolyte containing a non-aqueous solvent and a sodium salt, and the amount of sodium salt exceeds the saturation solubility at 25 ° C. in the non-aqueous solvent. It is included.
  • Sodium salts used in the non-aqueous electrolyte include NaPF 6 , NaBF 4 , NaClO 4 , NaN (SO 2 CF 3 ) 2 , NaN (SO 2 C 2 F 5 ) 2 , NaCF 3 SO 3 , NaAsF 6 , NaSbF 6 , NaBC 4 O 8 , lower aliphatic carboxylic acid sodium salt, NaAlCl 4 NaPO 2 F 2 , Na 2 PO 3 F and the like, and two or more of these may be used in combination.
  • the sodium salt in the non-aqueous electrolyte is present in the non-aqueous solvent beyond the saturation solubility of 25 ° C. in the non-aqueous solvent, and the sodium salt dissolves to the saturation solubility of 25 ° C. Salt is insoluble.
  • the sodium salt is preferably in a proportion of 1.0 mol or more, more preferably 1.1 mol or more, and even more preferably 1.2 mol or more with respect to 1 L of the non-aqueous electrolyte. A ratio of 1.3 mol or more is particularly preferable.
  • the sodium salt has a ratio of 3.0 mol or less with respect to 1 L of the non-aqueous electrolyte.
  • the ratio is preferably 2.5 mol or less, more preferably 2.3 mol or less, and particularly preferably 2.1 mol or less.
  • the sodium salt in the non-aqueous electrolyte is present in excess of the saturation solubility of 25 ° C. in the non-aqueous solvent.
  • a screw tube model No. 7, capacity 50 mL, bottom diameter 35 mm, height 78 mm
  • heat at 50 ° C. or higher using a polytetrafluoroethylene rotator with a total length of 20 mm.
  • the region was in the range of 10 nm to 200 nm. If the particles are counted, it can be determined that the sodium salt in the non-aqueous electrolyte exceeds the saturation solubility at 25 ° C. in the non-aqueous solvent.
  • the particle size distribution of the non-aqueous electrolyte can be measured by measuring the particle size using a dynamic scattering method, and can be measured using a Zetasizer Nano particle measuring device (manufactured by Sysmex Corporation). When the amount of the non-aqueous solvent and the sodium salt is less than 25 mL in total, it can be confirmed that the saturated solubility is exceeded by the same operation as above except that the screw tube size and the rotor size are changed. .
  • the sodium salt insoluble portion in the non-aqueous electrolyte is dispersed in the non-aqueous electrolyte and deposited and deposited on other members of the sodium secondary battery such as electrodes and separators. However, it is preferably dispersed in the non-aqueous electrolyte.
  • the non-aqueous electrolyte used in the present invention can be obtained by adding and stirring a sodium salt to a non-aqueous solvent and dissolving the sodium salt to saturation solubility. Alternatively, it can also be obtained by adding and stirring an additional sodium salt to a nonaqueous electrolytic solution in which the sodium salt is dissolved at a saturation solubility or lower. Alternatively, it can also be obtained by adding a nonaqueous solvent to a nonaqueous electrolytic solution containing a sodium salt in excess of the saturation solubility and diluting it. It is preferable to perform the said process in inert gas atmosphere, such as argon and nitrogen.
  • examples of the nonaqueous solvent used in the nonaqueous electrolytic solution include cyclic carbonates such as propylene carbonate and ethylene carbonate; Chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; Ethers such as 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran; Esters such as methyl formate and methyl acetate; Lactones such as ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -valerolactone, ⁇ -caprolactone; Nitriles such as acetonitrile and butyronitrile; Amides such as N, N-dimethylformamide, N, N-dimethylace
  • the non-aqueous solvent used for the non-aqueous electrolyte is preferably at least one solvent selected from solvents having a flash point of 70 ° C. or higher, and a solvent having a flash point of 70 ° C. or higher with respect to the non-aqueous electrolyte. It is preferable that 25 volume% or more is included. From the viewpoint of improving the heat resistance of the battery, the solvent having a flash point of 70 ° C. or higher is more preferably contained in an amount of 35% by volume or more, more preferably 45% by volume or more, and more preferably 60% by volume or more. It is particularly preferred.
  • the flash point of non-aqueous solvent you can refer to the published information. It can also be measured by a general flash point measurement test. Examples of the flash point measurement test method include a seta sealing type (JIS K2265-2, ISO 3679, ASTM D3278, D3828).
  • Examples of the solvent having a flash point of 70 ° C. or higher include propylene carbonate, ethylene carbonate, ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -valerolactone, ⁇ -caprolactone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfate, Dipropyl sulfite, ethylene sulfite, dimethyl sulfone, ethyl methyl sulfone, diphenyl sulfone, sulfolane, methyl methane sulfonate, dimethyl sulfoxide, 1,3-propane sultone, etc. are included, and two or more of these are mixed May be used.
  • surfactants such as trioctyl phosphate, diphenyl ether, polyoxyethylene ethers having a perfluoroalkyl group, and perfluorooctane sulfonate esters are included in the non-aqueous electrolyte. One or more of these may be added.
  • the addition amount of the surfactant is preferably 3% by weight or less, more preferably 0.01 to 1% by weight with respect to the weight of the electrolytic solution.
  • the positive electrode has a positive electrode active material that can be doped and dedoped with sodium ions.
  • a positive electrode may be comprised from a collector and the positive mix containing the said positive electrode active material carry
  • the positive electrode mixture contains a conductive material and a binder as necessary in addition to the positive electrode active material.
  • the positive electrode active material comprises a sodium-containing transition metal compound, and the sodium-containing transition metal compound can be doped and dedoped with sodium ions.
  • sodium-containing transition metal compound examples include the following compounds. That, NaFeO 2, NaMnO 2, NaNiO 2 and NaCoO oxide represented by NaM 3 a1 O 2, such as 2, oxide represented by Na 0.44 Mn 1-a2 M 3 a2 O 2, Na 0.
  • Oxide represented by Mn 1-a2 M 3 a2 O 2.05 (M 3 is one or more transition metal elements, 0 ⁇ a1 ⁇ 1, 0 ⁇ a2 ⁇ 1); Oxides represented by Na b1 M 4 c Si 12 O 30 such as Na 6 Fe 2 Si 12 O 30 and Na 2 Fe 5 Si 12 O 30 (M 4 is one or more transition metal elements, 2 ⁇ b1 ⁇ 6, 2 ⁇ c ⁇ 5); Na 2 Fe 2 Si 6 O 18 and Na 2 MnFeSi 6 O 18 Na d M 5 e Si 6 O 18 oxide represented by such (M 5 is one or more transition metal elements, 2 ⁇ d ⁇ 6, 1 ⁇ e ⁇ 2); Na 2 FeSiO Na f M 6 g Si oxide represented by 2 O 6, such as 6 (M 6 is at least one element selected from the group consisting of transition metal elements, Mg and Al, 1 ⁇ f ⁇ 2, 1 ⁇ g ⁇ 2) NaFePO 4 , NaMnPO 4 , Na 3
  • a composite metal oxide represented by the following formula (A) can be preferably used as the positive electrode active material.
  • the charge / discharge capacity of the battery can be improved.
  • Na a M 1 b M 2 O 2 (A) (Here, M 1 represents one or more elements selected from the group consisting of Mg, Ca, Sr and Ba, and M 2 represents a group consisting of Mn, Fe, Co, Cr, V, Ti and Ni. Represents one or more selected elements, a is 0.5 or more and 1 or less, b is 0 or more and 0.5 or less, and a + b is 0.5 or more and 1 or less.
  • a carbon material can be used as the conductive material.
  • the carbon material include carbon black (for example, acetylene black, ketjen black, furnace black), fibrous carbon material (carbon nanotube, carbon nanofiber, vapor grown carbon fiber, etc.) and the like.
  • the carbon material has a large surface area, and when added in a small amount in the electrode mixture, it is possible to improve the conductivity inside the resulting electrode and improve the charge / discharge efficiency and large current discharge characteristics.
  • the proportion of the conductive material in the positive electrode mixture is 4 to 20 parts by weight with respect to 100 parts by weight of the positive electrode active material, and two or more kinds may be contained.
  • binder used for the electrode examples include a polymer of a fluorine compound and an addition polymer of a monomer containing an ethylenic double bond not containing a fluorine atom.
  • the glass transition temperature of the binder is preferably -50 to 25 ° C. By setting the glass transition temperature within the above range, the flexibility of the obtained electrode can be improved, and a sodium secondary battery that can be sufficiently used even in a low temperature environment can be obtained.
  • binder examples include Polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer Fluororesins such as polymers; Vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-pentafluoropropylene copolymer, fluoride Fluoro rubbers such as vinylidene-pentafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoro fluor
  • Methacrylic polymers such as polymethacrylic acid, polyalkylmethacrylate (the alkyl group has 1 to 20 carbon atoms in the alkyl moiety), methacrylic acid-alkylmethacrylate copolymer; Polyvinyl alcohol (partially or completely saponified), ethylene-vinyl alcohol copolymer, polyvinylpyrrolidone, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-alkyl acrylate (the alkyl group has 1 carbon atom in the alkyl moiety) 20) Olefin such as copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid copolymer, ethylene-alkyl methacrylate copolymer, ethylene-alkyl acrylate copolymer, ethylene-acrylonitrile copolymer Based polymers; Examples thereof include styrene-containing polymers such as acrylonitrile-
  • the positive electrode is manufactured, for example, by supporting a positive electrode mixture containing a positive electrode active material that can be doped and dedoped with sodium ions on a positive electrode current collector.
  • a positive electrode active material, a conductive material, a binder and a solvent are kneaded to prepare a positive electrode mixture paste, and the obtained positive electrode mixture paste is collected into a current collector.
  • a method of applying to the body and drying is mentioned.
  • the method for applying the positive electrode mixture paste to the current collector is not particularly limited.
  • drying performed after application may be performed by heat treatment, or may be performed by air drying, vacuum drying, or the like.
  • the temperature is usually about 50 to 150 ° C.
  • the pressing method include a mold press and a roll press.
  • An electrode can be manufactured by the method mentioned above. The thickness of the electrode mixture is usually about 5 to 500 ⁇ m.
  • the ratio of the positive electrode mixture component in the positive electrode mixture paste that is, the total ratio of the positive electrode active material, the conductive material, and the binder in the positive electrode mixture paste is usually 40 to 40 from the viewpoint of the thickness of the obtained electrode and applicability. 70% by weight.
  • examples of the current collector include Al, Ni, stainless steel and the like, and Al is preferable in that it is easy to process into a thin film and is inexpensive.
  • the shape of the current collector is, for example, 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 flat plate). Can be given. Concavities and convexities may be formed on the surface of the current collector by etching.
  • the sodium-containing transition metal oxide which is an example of the positive electrode active material, can be produced by firing a mixture of metal-containing compounds having a composition that can be used for the sodium-containing transition metal oxide used in the present invention by firing.
  • the metal-containing compound containing the corresponding metal element can be produced by weighing and mixing so as to have a predetermined composition, and then firing the resulting mixture.
  • a sodium-containing transition metal oxide having a metal element ratio represented by Na: Mn: Fe: Ni 1: 0.3: 0.4: 0.3, which is one of the preferred metal element ratios, is Na 2 CO 3 , MnO 2 , Fe 3 O 4 , and Ni 2 O 3 are weighed so that the molar ratio of Na: Mn: Fe: Ni is 1: 0.3: 0.4: 0.3 And mixing them and firing the resulting mixture.
  • M 1 is one or more elements selected from the group consisting of Mg, Ca, Sr and Ba
  • a raw material containing M 1 is added during mixing. do it.
  • Examples of the metal-containing compound that can be used to produce the sodium-containing transition metal compound used in the present invention include oxides and compounds that can be converted to oxides when decomposed and / or oxidized at high temperatures, such as hydroxides. , Carbonates, nitrates, halides or oxalates can be used.
  • Examples of the sodium compound include one or more compounds selected from the group consisting of sodium hydroxide, sodium chloride, sodium nitrate, sodium peroxide, sodium sulfate, sodium bicarbonate, sodium oxalate, and sodium carbonate. Hydrates can also be given. From the viewpoint of handleability, sodium carbonate is more preferable.
  • the manganese compound is preferably MnO 2
  • the iron compound is preferably Fe 3 O 4
  • the nickel compound is preferably Ni 2 O 3 .
  • the mixture of metal-containing compounds can be obtained, for example, by obtaining a precursor of a metal-containing compound by the following precipitation method, and mixing the obtained precursor of the metal-containing compound and the sodium compound.
  • compounds such as chloride, nitrate, acetate, formate, and oxalate are used as raw materials for M 2 (where M 2 is as defined above), and these are dissolved in water and precipitated.
  • a precipitate containing a precursor of a metal-containing compound can be obtained by contacting with an agent. Of these raw materials, chloride is preferred.
  • these raw materials are added to acids such as hydrochloric acid, sulfuric acid, nitric acid, or aqueous solutions thereof. dissolved, it is also possible to obtain an aqueous solution containing M 2.
  • LiOH lithium hydroxide
  • NaOH sodium hydroxide
  • KOH potassium hydroxide
  • Li 2 CO 3 lithium carbonate
  • Na 2 CO 3 sodium carbonate
  • K 2 CO Li 2 CO 3
  • hydrates of the compounds can be used. 1 or more types may be used and a compound and a hydrate may be used together.
  • the concentration of the precipitating agent in the aqueous solution is about 0.5 to 10 mol / L, preferably about 1 to 8 mol / L.
  • KOH is the KOH aqueous solution which melt
  • ammonia water can be mention
  • the method of adding an aqueous solution containing M 2 to the aqueous precipitation agent is preferable in terms of easy maintenance of pH and easy control of the particle size.
  • the pH tends to decrease, but the pH is adjusted to 9 or more, preferably 10 or more. while, preferably added an aqueous solution containing M 2.
  • This adjustment can also be performed by adding an aqueous solution of a precipitant.
  • a precipitate can be obtained by the above contact.
  • This precipitate contains a precursor of a metal-containing compound.
  • Solid-liquid separation may be performed by any method, but from the viewpoint of operability, a method by solid-liquid separation such as filtration is preferably used, and a method of volatilizing the liquid by heating such as spray drying may be used. Moreover, you may perform washing
  • the precipitate obtained after the solid-liquid separation may have an excessive component of the precipitant attached thereto, and the component can be reduced by washing.
  • the cleaning liquid used for cleaning is preferably water, and a water-soluble organic solvent such as alcohol or acetone may be used.
  • the drying may be performed by heat drying, and may be performed by air drying, vacuum drying, or the like.
  • heat drying it is usually carried out at 50 to 300 ° C. and preferably at about 100 to 200 ° C.
  • the mixing apparatus include stirring and mixing, a V-type mixer, a W-type mixer, a ribbon mixer, a drum mixer, and a ball mill.
  • the firing may be carried out usually at a temperature of about 400 to 1200 ° C., preferably about 500 to 1000 ° C., although it depends on the type of sodium compound used.
  • the time for holding at the holding temperature is usually 0.1 to 20 hours, preferably 0.5 to 10 hours.
  • the rate of temperature rise to the holding temperature is usually 50 to 400 ° C./hour, and the rate of temperature drop from the holding temperature to room temperature is usually 10 to 400 ° C./hour.
  • baking can be performed in the atmosphere of air
  • the halide may play a role as a reaction accelerator (flux).
  • the flux include NaF, MnF 3 , FeF 2 , NiF 2 , CoF 2 , NaCl, MnCl 2 , FeCl 2 , FeCl 3 , NiCl 2 , CoCl 2 , NH 4 Cl and NH 4 I.
  • These fluxes may be hydrates.
  • other metal-containing compounds that are reaction accelerators include Na 2 CO 3 , NaHCO 3 B 2 O 3, and H 3 BO 3 .
  • the sodium-containing transition metal compound used in the present invention is used as a positive electrode active material for a sodium secondary battery
  • the sodium-containing transition metal compound obtained as described above is usually industrially used, such as a ball mill, a jet mill, and a vibration mill. It is preferable to adjust the particle size by performing pulverization using an apparatus to be used, washing, classification, and the like. Moreover, you may perform baking twice or more. Further, a surface treatment such as coating the particle surface of the sodium-containing transition metal compound with an inorganic substance containing Si, Al, Ti, Y or the like may be performed.
  • a negative electrode that can be used in the sodium secondary battery of the present invention an electrode in which a negative electrode mixture containing a negative electrode active material is carried on a negative electrode current collector, a sodium metal or sodium alloy electrode that can be doped and dedoped with sodium ions, Can be used.
  • a sodium metal or sodium alloy electrode that can be doped and dedoped with sodium ions
  • the negative electrode active material in addition to the above-mentioned sodium metal or sodium alloy, carbon such as coke, carbon black, pyrolytic carbons, carbon fiber, and organic polymer compound fired body that can be doped and dedoped with sodium ions Materials and metals.
  • the shape of the carbon material may be any of a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder.
  • the carbon material may play a role as a conductive material.
  • the carbon material examples include non-graphitized carbon materials (hereinafter sometimes referred to as hard carbon) such as carbon black, pyrolytic carbons, carbon fibers, and fired organic materials.
  • the hard carbon is preferably one having an interlayer distance d (002) by an X-ray diffraction method of 0.360 nm or more and 0.395 nm or less and a crystallite size Lc in the c-axis direction of 1.30 nm or less.
  • the R value (ID / IG) obtained by Raman spectroscopy is preferably 1.07 or more and 3 or less.
  • a Raman spectrum obtained by irradiating a laser having a wavelength of 532 nm and performing Raman spectroscopic measurement (the vertical axis is the scattered light intensity in an arbitrary unit, and the horizontal axis is the Raman shift wave number (cm ⁇ 1 ).
  • the hard carbon for example, carbon micro beads made of non-graphitized carbon material can be mentioned, and specifically, ICB (trade name: Nika beads) manufactured by Nippon Carbon Co., Ltd. can be mentioned.
  • the shape of the particles constituting the carbon material include a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, and an aggregate shape of fine particles.
  • the average particle diameter is preferably 0.01 ⁇ m or more and 30 ⁇ m or less, more preferably 0.1 ⁇ m or more and 20 ⁇ m or less.
  • Examples of the metal used for the negative electrode active material include tin, lead, silicon, germanium, phosphorus, bismuth, and antimony.
  • Examples of the alloy include an alloy composed of two or more metals selected from the group consisting of the above metals, an alloy composed of two or more metals selected from the group consisting of the above metals and transition metals, and Si— Examples of the alloy include Zn, Cu 2 Sb, and La 3 Ni 2 Sn 7 . These metals and alloys are used as an electrode active material by being carried on a current collector in combination with a carbon material.
  • Examples of the oxide used for the negative electrode active material include Li 4 Ti 5 O 12 and the like.
  • Examples of sulfides include TiS 2 , NiS 2 , FeS 2 , Fe 3 S 4 and the like.
  • Examples of nitrides, Na 3 N, Na 2.6 Co 0.4 Na such as N 3-x M x N (where, M is a transition metal element, 0 ⁇ x ⁇ 3), and the like.
  • These carbon materials, metals, oxides, sulfides, and nitrides that are negative electrode active materials may be used in combination, and may be crystalline or amorphous. From the viewpoint of cycle characteristics, it is preferable to use a carbon material as the negative electrode active material, and it is more preferable to use hard carbon.
  • These carbon materials, metals, oxides, sulfides, and nitrides are mainly supported on current collectors and used as electrodes.
  • the negative electrode mixture may contain a binder and a conductive material as necessary.
  • the binder and conductive material include the same binders and conductive materials used for the positive electrode.
  • the binder contained in the negative electrode mixture is preferably polyacrylic acid, sodium polyacrylate, lithium polyacrylate, potassium polyacrylate, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, ethylene-vinyl acetate.
  • the binder contained in the negative electrode mixture includes polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoro. It is preferable to use one or more selected from the group consisting of ethylene copolymers.
  • the ratio of the binder in the negative electrode mixture is usually about 0.5 to 30 parts by weight, preferably about 2 to 20 parts by weight with respect to 100 parts by weight of the carbon material.
  • Examples of the negative electrode current collector include Al, Cu, Ni, and stainless steel, and Al is preferable because it can be easily processed into a thin film and is inexpensive.
  • the shape of the current collector is, for example, 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 flat plate). Can be given. Concavities and convexities may be formed by etching on the current collector surface.
  • the thickness of the separator is preferably as thin as possible as long as the mechanical strength is maintained in that the volume energy density of the battery is increased and the internal resistance is reduced. In general, the thickness of the separator is preferably about 5 to 200 ⁇ m, more preferably about 5 to 40 ⁇ m.
  • the separator preferably has a porous film containing a thermoplastic resin.
  • a secondary battery normally, when an abnormal current flows in the battery due to a short circuit between the positive electrode and the negative electrode, the current is interrupted to prevent an excessive current from flowing (shut down). is important. Therefore, the separator shuts down at the lowest possible temperature when the normal use temperature is exceeded (when the separator has a porous film containing a thermoplastic resin, the micropores of the porous film are blocked). Even after the shutdown, even if the temperature in the battery rises to a certain high temperature, it is required to maintain the shutdown state without breaking the film due to the temperature, in other words, to have high heat resistance.
  • the thermal breakage of the secondary battery of the present invention It becomes possible to prevent more.
  • the heat-resistant porous layer may be laminated on both surfaces of the porous film.
  • Particle size distribution measurement of non-aqueous electrolyte The particle size distribution measurement of the non-aqueous electrolyte was performed using Zetasizer Nano (Nano ZS (ZEN3600), manufactured by Sysmex Corporation). The measurement was performed at 25 ° C. using a glass cuvette.
  • the mixture was placed in an alumina calcination vessel, then calcined by holding for six hours at 850 ° C. in an air atmosphere using an electric furnace and then cooled to room temperature to obtain a composite metal oxide A 1.
  • a powder X-ray diffraction analysis of the composite metal oxide A 1 was performed, it was found that the composite metal oxide A 1 was assigned to the ⁇ -NaFeO 2 type crystal structure.
  • the composition of the composite metal oxide A 1 is analyzed by ICP-AES, the molar ratio of Na: Ca: Fe: Ni: Mn is 0.99: 0.01: 0.4: 0.3: 0. 3.
  • a positive electrode mixture paste was prepared using Kida Chemical Co., Ltd.).
  • Composite metal oxide A 1 : Conductive material: Binder: Weighed to have a composition of NMP 90: 5: 5: 100 (weight ratio), and 4,000 rpm, 5 using a disperse mat (made by VMA-GETZMANN)
  • a positive electrode mixture paste was obtained by stirring and mixing for a minute.
  • the obtained positive electrode mixture paste was applied to a 20 ⁇ m thick aluminum foil using a doctor blade, dried at 60 ° C. for 2 hours, and then using a roll press (SA-602, manufactured by Tester Sangyo Co., Ltd.)
  • a positive electrode AE 1 was obtained by rolling at a pressure of 200 kN / m.
  • Carbon material C 1 : PVdF: NMP 90: 10: 100 (weight ratio) is weighed so as to have a composition, and is stirred and mixed using a disperse mat (VMA-GETZMANN Co., Ltd.). Obtained. The rotation conditions of the rotating blades were 2,000 rpm for 10 minutes. The obtained electrode mixture paste was applied to a copper foil using a doctor blade, dried at 60 ° C. for 2 hours, and then rolled at 100 kN / m using a roll press to obtain carbon electrode CE 1 . .
  • Example 1> (Production of Sodium Secondary Battery B 1) A propylene carbonate (PC) solution (NaPF 6 PC) containing 1.3 mol of NaPF 6 in 1 L (manufactured by Kishida Chemical Co., Ltd.) and fluoroethylene carbonate (FEC) (manufactured by Kishida Chemical Co., Ltd.) 98: 2 Take the screw tube (manufactured by ASONE, model No. 7) to a total volume ratio of 25 mL and heat at 80 ° C. using a polytetrafluoroethylene rotor with a total length of 20 mm at 250 rpm.
  • PC propylene carbonate
  • FEC fluoroethylene carbonate
  • non-aqueous electrolyte EL 1 (PC / FEC containing 1.3 mol of NaPF 6 in 1 L).
  • the flash points of PC and FEC are disclosed as 135 ° C. and 122 ° C., respectively, in the product safety data seed issued by Kishida Chemical Co., Ltd.
  • the ratio of PC and FEC to non-aqueous electrolyte EL 1 is 91 vol. %.
  • the electrolyte EL 1 As a result of measuring the particle size distribution of the non-aqueous electrolyte EL 1 , it was confirmed that particles were counted in a region of 10 nm or more and 200 nm or less, and that the sodium salt exceeded the saturation solubility at 25 ° C.
  • a positive electrode AE 1 punched to a diameter of 14.5 mm is placed in a recess in the lower part of a coin cell (manufactured by Hosen Co., Ltd.), and a carbon electrode CE 1 punched to a diameter of 15.0 mm is used as the negative electrode in the electrolyte.
  • the electrolyte EL 1 to produce a sodium secondary battery B 1 with polyethylene porous film (thickness 20 [mu] m) as a separator.
  • the battery was assembled in a glove box in an argon atmosphere.
  • Example 2> (Production of Sodium Secondary Battery B 2) The same as Example 1 except that PC containing 2.0 mol of NaPF 6 in 1 L, PC (manufactured by Kishida Chemical Co., Ltd.), and FEC were in a ratio of 74: 24: 2 (volume ratio).
  • the non-aqueous electrolyte EL 2 (PC / FEC containing 1.5 mol of NaPF 6 in 1 L) was prepared by the operation.
  • the ratio of PC and FEC to the non-aqueous electrolyte EL 2 is 90% by volume.
  • Example 3 (Production of Sodium Secondary Battery B 3) A non-aqueous electrolyte EL 3 (in 1 L) was prepared in the same manner as in Example 1 except that PC containing 2.0 mol of NaPF 6 in 1 L and FEC were in a ratio of 98: 2 (volume ratio). the PC / FEC solution) containing 2.0 mol of NaPF 6 in the adjustment. The ratio of PC and FEC to the non-aqueous electrolyte EL 3 is 86% by volume.
  • Example 4> (Preparation of Sodium Secondary Battery B 4)
  • PC containing 2.0 mol of NaPF 6 in 1 L as non-aqueous electrolyte EL 4 is taken into a screw tube (manufactured by ASONE, model No. 7) so as to be 25 mL, and heated to 80 ° C., with a total length of 20 mm.
  • a polytetrafluoroethylene rotator prepared by stirring at 250 rpm in an argon gas atmosphere for 6 hours. Percentage of PC relative to the non-aqueous electrolyte EL 4 is a 86% by volume.
  • a sodium secondary battery B 4 was produced in the same manner as in Example 1 except that PC (nonaqueous electrolyte EL 4 ) containing 2.0 mol of NaPF 6 in 1 L was used.
  • Example 5 (Production of Sodium Secondary Battery B 5) Example 1 except that NaPF 6 (manufactured by Johnson Matthey) was added to a PC containing 2.0 mol of NaPF 6 in 1 L so as to be a PC containing 2.5 mol of NaPF 6 in 1 L.
  • the non-aqueous electrolyte EL 5 (PC containing 2.5 mol of NaPF 6 in 1 L) was prepared in the same manner as in Example 1. Percentage of PC relative to the non-aqueous electrolyte EL 5 is 82% by volume.
  • Example 6 (Production of Sodium Secondary Battery B 6) A PC containing 1.0 mol of NaN (SO 2 CF 3 ) 2 in 1 L (manufactured by Kishida Chemical Co., Ltd.) becomes a PC containing 2.0 mol of NaN (SO 2 CF 3 ) 2 in 1 L.
  • the non-aqueous electrolyte EL 6 (2.0 mol of NaN in 1 L) was prepared in the same manner as in Example 1 except that NaN (SO 2 CF 3 ) 2 (NaTFSI) (manufactured by Kishida Chemical Co., Ltd.) was added.
  • PC containing (SO 2 CF 3 ) 2 was adjusted.
  • the ratio of PC to non-aqueous electrolyte EL 6 is 68% by volume.
  • a sodium secondary battery B 6 was produced in the same manner as in Example 1 except that the non-aqueous electrolyte EL 6 was used as the electrolyte.
  • Example 7> (Production of Sodium Secondary Battery B 7)
  • PC made by Kishida Chemical Co., Ltd.
  • the non-aqueous electrolyte EL 7 (1.0 mol of NaPF 6 and 0.3 mol in 1 L) was prepared in the same manner as in Example 1 except that NaTFSI (manufactured by Kishida Chemical Co., Ltd.) was added so as to be PC.
  • PC / FEC containing NaTFSI The ratio of PC and FEC to non-aqueous electrolyte EL 7 is 89% by volume.
  • Example 8> (Production of Sodium Secondary Battery B 8) Example 1 except that NaTFSI was added to a PC containing 1.0 mol of NaPF 6 in 1 L so as to be a PC containing 1.0 mol of NaTFSI in 1 L.
  • the non-aqueous electrolyte EL 8 (PC containing 1.0 mol of NaPF 6 and 1.0 mol of NaTFSI in 1 L) was prepared by the above procedure. Percentage of PC relative to the non-aqueous electrolyte EL 8 is 80% by volume.
  • a sodium secondary battery BH 1 was produced in the same manner as in Example 1 except that the non-aqueous electrolyte EH 1 was used as the electrolyte.
  • ⁇ Charge / discharge test> Prior to the charge / discharge test, the sodium secondary batteries B 1 to B 8 and BH 1 to BH 3 were stabilized (stabilized), and then the output test and the charge / discharge cycle test were performed. .
  • CC Constant Current
  • CC charging was performed at a 0.05 C rate until reaching 3.8 V, and then a current-carrying treatment for performing CC discharging until reaching 2.0 V at a 0.1 C rate was performed for one cycle.
  • CC-CV constant voltage
  • CC-CV constant voltage
  • CC-CV constant voltage
  • ⁇ Output test> After the stabilization treatment, an output test was performed under the following conditions. After performing CC-CV charge at a 0.2C rate until reaching 4.0V (charging is completed when the current value reaches 0.02C), a charge / discharge test is performed to perform CC discharge until reaching 2.0V at a 0.2C rate. It was. Thereafter, an output test was performed under the same charging conditions as those described above, with discharge currents of 0.5, 1, 2, 5, 10C. Table 1 shows a ratio of 5C discharge capacity to 0.2C discharge capacity (5C discharge capacity / 0.2C discharge capacity ⁇ 100 (%)). ⁇ Charge / discharge cycle test> After the output test, a charge / discharge cycle test was performed under the following conditions.
  • a sodium secondary battery excellent in charge / discharge cycle characteristics when charged at a relatively high speed that is, at a relatively large current value (1C rate).
  • a sodium secondary battery excellent in output characteristics can be provided.

Abstract

This sodium-ion battery has a positive electrode that has a positive electrode active substance in which sodium ions can be doped and dedoped, a negative electrode that has a positive electrode active substance in which sodium ions can be doped and dedoped, a non-aqueous solvent, and a non-aqueous electrolyte comprising a sodium salt that exceeds the saturation solubility in the non-aqueous electrolyte. Thereby, it is possible to provide a sodium-ion battery that has excellent charge/discharge cycle characteristics when charging at relatively high speed, that is to say, with a relatively large current. Moreover, it is possible to provide a sodium-ion battery which excellent output characteristics.

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ものである。 The present invention relates to a sodium secondary battery.
　非水電解液を用いるナトリウム二次電池は、水系電解液の電池と比較して高い電圧を発生できるため、高エネルギー密度を有する電池として好適である。しかも、ナトリウムは資源量が豊富でしかも安価な材料であることから、これを実用化することにより、大型電源を大量に供給できることが期待されている。 A sodium secondary battery using a non-aqueous electrolyte is suitable as a battery having a high energy density because it can generate a higher voltage than a battery of an aqueous electrolyte. Moreover, since sodium is an abundant and inexpensive material, it is expected that large-scale power can be supplied in large quantities by putting it into practical use.
　ナトリウム二次電池は、通常、ナトリウムイオンをドープかつ脱ドープすることができる正極活物質を含む正極と、ナトリウムイオンをドープかつ脱ドープすることができる負極活物質を含む負極との少なくとも一対の電極と、電解質とを有する。 A sodium secondary battery usually includes at least a pair of electrodes, a positive electrode including a positive electrode active material capable of doping and dedoping sodium ions, and a negative electrode including a negative electrode active material capable of doping and dedoping sodium ions. And an electrolyte.
　ナトリウム二次電池に用いられる電解質として、非水電解液が挙げられる。非水電解液として、プロピレンカーボネートなどの飽和型環状炭酸エステルからなる非水溶媒に、六フッ化リン酸ナトリウムからなる電解質塩が溶解した非水電解液を用いたナトリウム二次電池が知られている（特開２００７−３５２８３号公報）。 Non-aqueous electrolyte is mentioned as an electrolyte used for a sodium secondary battery. As a non-aqueous electrolyte, a sodium secondary battery using a non-aqueous electrolyte in which an electrolyte salt composed of sodium hexafluorophosphate is dissolved in a non-aqueous solvent composed of a saturated cyclic carbonate such as propylene carbonate is known. (JP 2007-35283 A).
　しかしながら、上記のような電解液を用いたナトリウム二次電池は、比較的早い速度、すなわち、比較的大きな電流値で充電した際の充放電サイクル特性が充分ではなかった。そこで、本発明の目的は、比較的早い速度で充電した際の充放電サイクル特性に優れたナトリウム二次電池を提供することにある。 However, the sodium secondary battery using the above-described electrolytic solution has insufficient charge / discharge cycle characteristics when charged at a relatively high speed, that is, at a relatively large current value. Therefore, an object of the present invention is to provide a sodium secondary battery excellent in charge / discharge cycle characteristics when charged at a relatively high speed.
　前記目的を達成するため、ナトリウムイオンをドープかつ脱ドープできる正極活物質を有する正極と、ナトリウムイオンをドープかつ脱ドープできる負極活物質を有する負極と、非水溶媒と、該非水溶媒への飽和溶解度を超える量のナトリウム塩とを含む非水電解液とを有するナトリウム二次電池を提供する。 To achieve the above object, a positive electrode having a positive electrode active material that can be doped and dedoped with sodium ions, a negative electrode having a negative electrode active material that can be doped and dedoped with sodium ions, a nonaqueous solvent, and saturation to the nonaqueous solvent A sodium secondary battery having a non-aqueous electrolyte containing a sodium salt in an amount exceeding the solubility is provided.
　本発明によれば、比較的速い速度、すなわち、比較的大きな電流値で充電した際の充放電サイクル特性に優れたナトリウム二次電池を提供することができる。しかも、出力特性にも優れたナトリウム二次電池を提供することができる。 According to the present invention, it is possible to provide a sodium secondary battery excellent in charge / discharge cycle characteristics when charged at a relatively high speed, that is, at a relatively large current value. In addition, a sodium secondary battery excellent in output characteristics can be provided.
＜ナトリウム二次電池＞
　本発明のナトリウム二次電池は、ナトリウムイオンをドープかつ脱ドープできる正極活物質を有する正極と、ナトリウムイオンをドープかつ脱ドープできる負極活物質を有する負極と、非水電解液とを有し、通常、さらにセパレータを有する。 <Sodium secondary battery>
The sodium secondary battery of the present invention has a positive electrode having a positive electrode active material that can be doped and dedoped with sodium ions, a negative electrode having a negative electrode active material that can be doped and dedoped with sodium ions, and a non-aqueous electrolyte. Usually, it further has a separator.
　ナトリウム二次電池は、通常、負極、セパレータ及び正極を積み重ねた積層体や、積層体を巻回または折りたたむことによって得られる電極群を、電池缶やアルミラミネートパック内に収納し、非水電解液を電極群に含浸させることによって、製造することができる。 A sodium secondary battery usually contains a laminate in which a negative electrode, a separator and a positive electrode are stacked, and an electrode group obtained by winding or folding the laminate in a battery can or an aluminum laminate pack, and a non-aqueous electrolyte. Can be manufactured by impregnating the electrode group.
　ここでこの電極群の形状としては例えば、この電極群を巻回の軸に対して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をあげることができる。また、電池の形状としては、例えば、ペーパー型、コイン型、円筒型、角型などの形状をあげることができる。 Here, as the shape of the electrode group, for example, 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. The shape can be raised. In addition, examples of the shape of the battery include a paper shape, a coin shape, a cylindrical shape, and a square shape.
＜非水電解液＞
　本発明のナトリウム二次電池に用いられる非水電解液は、非水溶媒とナトリウム塩とを含む非水電解液であって、該非水溶媒への２５℃での飽和溶解度を超える量のナトリウム塩が含まれている。 <Non-aqueous electrolyte>
The non-aqueous electrolyte used in the sodium secondary battery of the present invention is a non-aqueous electrolyte containing a non-aqueous solvent and a sodium salt, and the amount of sodium salt exceeds the saturation solubility at 25 ° C. in the non-aqueous solvent. It is included.
＜ナトリウム塩＞
　非水電解液に用いられるナトリウム塩としては、ＮａＰＦ６、ＮａＢＦ４、ＮａＣｌＯ４、ＮａＮ（ＳＯ２ＣＦ３）２、ＮａＮ（ＳＯ２Ｃ２Ｆ５）２、ＮａＣＦ３ＳＯ３、ＮａＡｓＦ６、ＮａＳｂＦ６、ＮａＢＣ４Ｏ８、低級脂肪族カルボン酸ナトリウム塩、ＮａＡｌＣｌ４ＮａＰＯ２Ｆ２、Ｎａ２ＰＯ３Ｆなどがあげられ、これらのうちの２種以上を混合して使用してもよい。これらの中でも、ＮａＰＦ６、ＮａＢＦ４、ＮａＳｂＦ６、ＮａＮ（ＳＯ２ＣＦ３）２、ＮａＮ（ＳＯ２Ｃ２Ｆ５）２、ＮａＣＦ３ＳＯ３およびＮａ２ＰＯ３Ｆからなる群から選ばれる少なくとも１種を用いることが好ましく、ＮａＰＦ６、ＮａＢＦ４、ＮａＮ（ＳＯ２ＣＦ３）２からなる群から選ばれる少なくとも１種を用いることがより好ましい。 <Sodium salt>
Sodium salts used in the non-aqueous electrolyte include NaPF 6 , NaBF 4 , NaClO 4 , NaN (SO 2 CF 3 ) 2 , NaN (SO 2 C 2 F 5 ) 2 , NaCF 3 SO 3 , NaAsF 6 , NaSbF 6 , NaBC 4 O 8 , lower aliphatic carboxylic acid sodium salt, NaAlCl 4 NaPO 2 F 2 , Na 2 PO 3 F and the like, and two or more of these may be used in combination. Among these, at least selected from the group consisting of NaPF 6 , NaBF 4 , NaSbF 6 , NaN (SO 2 CF 3 ) 2 , NaN (SO 2 C 2 F 5 ) 2 , NaCF 3 SO 3 and Na 2 PO 3 F. It is preferable to use one, and it is more preferable to use at least one selected from the group consisting of NaPF 6 , NaBF 4 , and NaN (SO 2 CF 3 ) 2 .
　非水電解液中のナトリウム塩は、非水溶媒への２５℃の飽和溶解度を超えて非水溶媒中に存在しており、ナトリム塩は２５℃の飽和溶解度まで溶解し、飽和溶解度以上のナトリウム塩は不溶状態である。２５℃で、外部からの刺激により溶解平衡に移行してナトリウム塩の一部の不溶化が生じる準安定状態であってもよい。導電性の観点から、前記非水電解液１Ｌに対して、ナトリウム塩は１．０モル以上の割合が好ましく、１．１モル以上の割合がより好ましく、１．２モル以上の割合が更に好ましく、１．３モル以上の割合が特に好ましい。また、非水電解液中のナトリウム塩の不溶部が多すぎると、セパレータの目詰まりの原因となりうるため、前記非水電解液１Ｌに対して、ナトリウム塩は、３．０モル以下の割合が好ましく、２．５モル以下の割合がより好ましく、２．３モル以下の割合がさらに好ましく、２．１モル以下の割合が特に好ましい。 The sodium salt in the non-aqueous electrolyte is present in the non-aqueous solvent beyond the saturation solubility of 25 ° C. in the non-aqueous solvent, and the sodium salt dissolves to the saturation solubility of 25 ° C. Salt is insoluble. A metastable state in which a part of the sodium salt is insolubilized at 25 ° C. due to a transition to a dissolution equilibrium by an external stimulus. From the viewpoint of conductivity, the sodium salt is preferably in a proportion of 1.0 mol or more, more preferably 1.1 mol or more, and even more preferably 1.2 mol or more with respect to 1 L of the non-aqueous electrolyte. A ratio of 1.3 mol or more is particularly preferable. In addition, if there are too many insoluble parts of sodium salt in the non-aqueous electrolyte, it may cause clogging of the separator. Therefore, the sodium salt has a ratio of 3.0 mol or less with respect to 1 L of the non-aqueous electrolyte. The ratio is preferably 2.5 mol or less, more preferably 2.3 mol or less, and particularly preferably 2.1 mol or less.
　非水電解液中のナトリウム塩が非水溶媒への２５℃の飽和溶解度を超えて存在していることは、以下のようにして確認することができる。非水電解液２５ｍＬをスクリュー管（型番Ｎｏ．７、容量５０ｍＬ、底径３５ｍｍ、高さ７８ｍｍ）にとり、５０℃以上で過熱しながら、全長２０ｍｍのポリテトラフルオロエチレン回転子を用い１００ｒｐｍ以上で３時間以上、アルゴンや窒素などの不活性ガス雰囲気下で攪拌し、２５℃まで降温することで調製した非水電解液の粒度分布測定を２５℃で行った際に、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされれば、該非水電解液中のナトリウム塩が、非水溶媒への２５℃での飽和溶解度を超えていると判断できる。非水電解液の粒度分布は、動的散乱法による粒子径測定により測定でき、Ｚｅｔａｓｉｚｅｒ　Ｎａｎｏ粒子測定装置（シスメックス株式会社製）を用いて測定できる。非水溶媒とナトリウム塩が、あわせて２５ｍＬに満たない量である場合、スクリュー管のサイズ、回転子のサイズを変更する以外は、上記と同じ操作で、飽和溶解度を超えていることを確認できる。 It can be confirmed as follows that the sodium salt in the non-aqueous electrolyte is present in excess of the saturation solubility of 25 ° C. in the non-aqueous solvent. Take 25 mL of non-aqueous electrolyte in a screw tube (model No. 7, capacity 50 mL, bottom diameter 35 mm, height 78 mm) and heat at 50 ° C. or higher, using a polytetrafluoroethylene rotator with a total length of 20 mm. When the particle size distribution measurement of a non-aqueous electrolyte prepared by stirring in an inert gas atmosphere such as argon or nitrogen for more than an hour and lowering the temperature to 25 ° C. was performed at 25 ° C., the region was in the range of 10 nm to 200 nm. If the particles are counted, it can be determined that the sodium salt in the non-aqueous electrolyte exceeds the saturation solubility at 25 ° C. in the non-aqueous solvent. The particle size distribution of the non-aqueous electrolyte can be measured by measuring the particle size using a dynamic scattering method, and can be measured using a Zetasizer Nano particle measuring device (manufactured by Sysmex Corporation). When the amount of the non-aqueous solvent and the sodium salt is less than 25 mL in total, it can be confirmed that the saturated solubility is exceeded by the same operation as above except that the screw tube size and the rotor size are changed. .
　本発明のナトリウム二次電池において、非水電解液中のナトリウム塩不溶部は、非水電解液中に分散している状態と、電極やセパレータなどのナトリウム二次電池の他部材に析出・堆積した状態があげられるが、非水電解液中に分散している状態が好ましい。 In the sodium secondary battery of the present invention, the sodium salt insoluble portion in the non-aqueous electrolyte is dispersed in the non-aqueous electrolyte and deposited and deposited on other members of the sodium secondary battery such as electrodes and separators. However, it is preferably dispersed in the non-aqueous electrolyte.
＜非水電解液の調整方法＞
　本発明に用いられる非水電解液は、非水溶媒にナトリウム塩を添加・攪拌し飽和溶解度までナトリウム塩を溶解することで得られる。または、ナトリウム塩が飽和溶解度以下で溶解している非水電解液に、追加でナトリウム塩を添加・攪拌することでも得られる。あるいは、ナトリウム塩が飽和溶解度を超えて含まれている非水電解液に、非水溶媒を添加し、希釈することでも得られる。上記工程は、アルゴンや窒素などの不活性ガス雰囲気下で行うことが好ましい。 <Method for adjusting non-aqueous electrolyte>
The non-aqueous electrolyte used in the present invention can be obtained by adding and stirring a sodium salt to a non-aqueous solvent and dissolving the sodium salt to saturation solubility. Alternatively, it can also be obtained by adding and stirring an additional sodium salt to a nonaqueous electrolytic solution in which the sodium salt is dissolved at a saturation solubility or lower. Alternatively, it can also be obtained by adding a nonaqueous solvent to a nonaqueous electrolytic solution containing a sodium salt in excess of the saturation solubility and diluting it. It is preferable to perform the said process in inert gas atmosphere, such as argon and nitrogen.
＜非水溶媒＞
　本発明において、非水電解液に用いられる非水溶媒として、例えば
プロピレンカーボネート、エチレンカーボネートなどの環状炭酸エステル類；
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などの鎖状炭酸エステル類；
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、酢酸メチルなどのエステル類；
γ−ブチロラクトン、γ−バレロラクトン、δ−バレロラクトン、ε−カプロラクトンなどのラクトン類；
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、１，３−ジメチル−２−イミダゾリジノンなどのアミド類；
３−メチル−２−オキサゾリドンなどのカーバメート類；
ジメチルサルフェート、ジメチルサルファイト、ジプロピルサルファイト、エチレンサルファイト、ジメチルスルホン、エチルメチルスルホン、ジフェニルスルホン、スルホラン、メタンスルホン酸メチル、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；
を用いることができる。非水溶媒として、これらのうちの２種以上を混合して用いてもよい。 <Nonaqueous solvent>
In the present invention, examples of the nonaqueous solvent used in the nonaqueous electrolytic solution include cyclic carbonates such as propylene carbonate and ethylene carbonate;
Chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate;
Ethers such as 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran;
Esters such as methyl formate and methyl acetate;
Lactones such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, ε-caprolactone;
Nitriles such as acetonitrile and butyronitrile;
Amides such as N, N-dimethylformamide, N, N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone;
Carbamates such as 3-methyl-2-oxazolidone;
Sulfur-containing compounds such as dimethyl sulfate, dimethyl sulfite, dipropyl sulfite, ethylene sulfite, dimethyl sulfone, ethyl methyl sulfone, diphenyl sulfone, sulfolane, methyl methanesulfonate, dimethyl sulfoxide, 1,3-propane sultone;
Can be used. Two or more of these may be mixed and used as the non-aqueous solvent.
　非水電解液に用いられる非水溶媒は、引火点が７０℃以上の溶媒から選ばれる少なくとも１種の溶媒であることが好ましく、前記非水電解液に対して引火点が７０℃以上の溶媒を２５体積％以上含むことが好ましい。電池の耐熱性向上の観点から、引火点が７０℃以上の溶媒は、非水電解液に対し３５体積％以上含むことがより好ましく、４５体積％以上含むことがさらに好ましく、６０体積％以上含むことが特に好ましい。 The non-aqueous solvent used for the non-aqueous electrolyte is preferably at least one solvent selected from solvents having a flash point of 70 ° C. or higher, and a solvent having a flash point of 70 ° C. or higher with respect to the non-aqueous electrolyte. It is preferable that 25 volume% or more is included. From the viewpoint of improving the heat resistance of the battery, the solvent having a flash point of 70 ° C. or higher is more preferably contained in an amount of 35% by volume or more, more preferably 45% by volume or more, and more preferably 60% by volume or more. It is particularly preferred.
　非水溶媒の引火点は、公開された情報を参照出来る。また、一般的な引火点測定試験により測定することも出来る。引火点測定試験方法としては、セタ密閉式（ＪＩＳ　Ｋ２２６５−２、ＩＳＯ　３６７９、ＡＳＴＭ　Ｄ３２７８、Ｄ３８２８）があげられる。 引 For the flash point of non-aqueous solvent, you can refer to the published information. It can also be measured by a general flash point measurement test. Examples of the flash point measurement test method include a seta sealing type (JIS K2265-2, ISO 3679, ASTM D3278, D3828).
　引火点が７０℃以上の溶媒としては、プロピレンカーボネート、エチレンカーボネート、γ−ブチロラクトン、γ−バレロラクトン、δ−バレロラクトン、ε−カプロラクトン、１，３−ジメチル−２−イミダゾリジノン、ジメチルサルフェート、ジプロピルサルファイト、エチレンサルファイト、ジメチルスルホン、エチルメチルスルホン、ジフェニルスルホン、スルホラン、メタンスルホン酸メチル、ジメチルスルホキシド、１，３−プロパンサルトンなどがあげられ、これらのうちの２種以上を混合して使用してもよい。これらの中でも、プロピレンカーボネート、エチレンカーボネート、γ−ブチロラクトン、γ−バレロラクトン、ε−カプロラクトン、エチレンサルファイト、ジメチルスルホン、エチルメチルスルホン、スルホラン、１，３−プロパンサルトンからなる群から選ばれる少なくとも１種の溶媒を用いることが好ましく、プロピレンカーボネート、エチレンカーボネート、γ−ブチロラクトン、エチレンサルファイト、スルホランからなる群から選ばれる少なくとも１種の溶媒を用いることがより好ましい。 Examples of the solvent having a flash point of 70 ° C. or higher include propylene carbonate, ethylene carbonate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, ε-caprolactone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfate, Dipropyl sulfite, ethylene sulfite, dimethyl sulfone, ethyl methyl sulfone, diphenyl sulfone, sulfolane, methyl methane sulfonate, dimethyl sulfoxide, 1,3-propane sultone, etc. are included, and two or more of these are mixed May be used. Among these, at least selected from the group consisting of propylene carbonate, ethylene carbonate, γ-butyrolactone, γ-valerolactone, ε-caprolactone, ethylene sulfite, dimethyl sulfone, ethyl methyl sulfone, sulfolane, and 1,3-propane sultone. It is preferable to use one type of solvent, and it is more preferable to use at least one type of solvent selected from the group consisting of propylene carbonate, ethylene carbonate, γ-butyrolactone, ethylene sulfite, and sulfolane.
　前記非水電解液には、セパレータとの濡れ性を良くするために、トリオクチルフォスフェート、ジフェニルエーテル、パーフルオロアルキル基を有するポリオキシエチレンエーテル類、パーフルオロオクタンスルホン酸エステル類等の界面活性剤の１種または２種以上を添加しても良い。界面活性剤の添加量は、好ましくは電解液重量に対して３重量％以下であり、より好ましくは０．０１~１重量％である。 In order to improve the wettability with the separator, surfactants such as trioctyl phosphate, diphenyl ether, polyoxyethylene ethers having a perfluoroalkyl group, and perfluorooctane sulfonate esters are included in the non-aqueous electrolyte. One or more of these may be added. The addition amount of the surfactant is preferably 3% by weight or less, more preferably 0.01 to 1% by weight with respect to the weight of the electrolytic solution.
＜正極＞
　本発明において、正極は、ナトリウムイオンをドープかつ脱ドープできる正極活物質を有する。また、正極は、集電体と、集電体の上に担持された、上記正極活物質を含む正極合剤とから構成されてよい。正極合剤は、上記正極活物質以外にも必要に応じて導電材やバインダーを含む <Positive electrode>
In the present invention, the positive electrode has a positive electrode active material that can be doped and dedoped with sodium ions. Moreover, a positive electrode may be comprised from a collector and the positive mix containing the said positive electrode active material carry | supported on the collector. The positive electrode mixture contains a conductive material and a binder as necessary in addition to the positive electrode active material.
＜正極活物質＞
　本発明において、正極活物質は、ナトリウム含有遷移金属化合物からなり、該ナトリウム含有遷移金属化合物は、ナトリウムイオンをドープかつ脱ドープすることができる。 <Positive electrode active material>
In the present invention, the positive electrode active material comprises a sodium-containing transition metal compound, and the sodium-containing transition metal compound can be doped and dedoped with sodium ions.
　前記ナトリウム含有遷移金属化合物としては、次の化合物をあげることができる。
　すなわち、ＮａＦｅＯ２、ＮａＭｎＯ２、ＮａＮｉＯ２およびＮａＣｏＯ２等のＮａＭ３ ａ１Ｏ２で表される酸化物、Ｎａ０．４４Ｍｎ１−ａ２Ｍ３ ａ２Ｏ２で表される酸化物、Ｎａ０．７Ｍｎ１−ａ２Ｍ３ ａ２Ｏ２．０５で表される酸化物（Ｍ３は１種以上の遷移金属元素、０＜ａ１＜１、０≦ａ２＜１）；
　Ｎａ６Ｆｅ２Ｓｉ１２Ｏ３０およびＮａ２Ｆｅ５Ｓｉ１２Ｏ３０等のＮａｂ１Ｍ４ ｃＳｉ１２Ｏ３０で表される酸化物（Ｍ４は１種以上の遷移金属元素、２≦ｂ１≦６、２≦ｃ≦５）；
　Ｎａ２Ｆｅ２Ｓｉ６Ｏ１８およびＮａ２ＭｎＦｅＳｉ６Ｏ１８等のＮａｄＭ５ ｅＳｉ６Ｏ１８で表される酸化物（Ｍ５は１種以上の遷移金属元素、２≦ｄ≦６、１≦ｅ≦２）；
　Ｎａ２ＦｅＳｉＯ６等のＮａｆＭ６ ｇＳｉ２Ｏ６で表される酸化物（Ｍ６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、ＮａＭｎＰＯ４、Ｎａ３Ｆｅ２（ＰＯ４）３、Ｎａ３Ｖ２（ＰＯ４）２Ｆ３、Ｎａ１．５ＶＯＰＯ４Ｆ０．５、Ｎａ４Ｆｅ３（ＰＯ４）２Ｐ２Ｏ７、Ｎａ４Ｍｎ３（ＰＯ４）２Ｐ２Ｏ７、Ｎａ４Ｎｉ３（ＰＯ４）２Ｐ２Ｏ７、Ｎａ４Ｃｏ３（ＰＯ４）２Ｐ２Ｏ７等のリン酸塩；
　Ｎａ２ＦｅＰＯ４Ｆ、Ｎａ２ＶＰＯ４Ｆ、Ｎａ２ＭｎＰＯ４Ｆ、Ｎａ２ＣｏＰＯ４Ｆ、Ｎａ２ＮｉＰＯ４Ｆ等のフッ化リン酸塩；
　ＮａＦｅＳＯ４Ｆ、ＮａＭｎＳＯ４Ｆ、ＮａＣｏＳＯ４Ｆ、ＮａＦｅＳＯ４Ｆ等のフッ化硫酸塩；
　ＮａＦｅＢＯ４、Ｎａ３Ｆｅ２（ＢＯ４）３等のホウ酸塩；
　Ｎａ３ＦｅＦ６、Ｎａ２ＭｎＦ６等のＮａｈＭ７Ｆ６で表されるフッ化物（Ｍ７は１種以上の遷移金属元素、２≦ｈ≦３）；等があげられる。 Examples of the sodium-containing transition metal compound include the following compounds.
That, NaFeO 2, NaMnO 2, NaNiO 2 and NaCoO oxide represented by NaM 3 a1 O 2, such as 2, oxide represented by Na 0.44 Mn 1-a2 M 3 a2 O 2, Na 0. 7 Oxide represented by Mn 1-a2 M 3 a2 O 2.05 (M 3 is one or more transition metal elements, 0 <a1 <1, 0 ≦ a2 <1);
Oxides represented by Na b1 M 4 c Si 12 O 30 such as Na 6 Fe 2 Si 12 O 30 and Na 2 Fe 5 Si 12 O 30 (M 4 is one or more transition metal elements, 2 ≦ b1 ≦ 6, 2 ≦ c ≦ 5);
Na 2 Fe 2 Si 6 O 18 and Na 2 MnFeSi 6 O 18 Na d M 5 e Si 6 O 18 oxide represented by such (M 5 is one or more transition metal elements, 2 ≦ d ≦ 6, 1 ≦ e ≦ 2);
Na 2 FeSiO Na f M 6 g Si oxide represented by 2 O 6, such as 6 (M 6 is at least one element selected from the group consisting of transition metal elements, Mg and Al, 1 ≦ f ≦ 2, 1 ≦ g ≦ 2)
NaFePO 4 , NaMnPO 4 , Na 3 Fe 2 (PO 4 ) 3 , Na 3 V 2 (PO 4 ) 2 F 3 , Na 1.5 VOPO 4 F 0.5 , Na 4 Fe 3 (PO 4 ) 2 P 2 Phosphates such as O 7 , Na 4 Mn 3 (PO 4 ) 2 P 2 O 7 , Na 4 Ni 3 (PO 4 ) 2 P 2 O 7 , Na 4 Co 3 (PO 4 ) 2 P 2 O 7 ;
Fluorophosphates such as Na 2 FePO 4 F, Na 2 VPO 4 F, Na 2 MnPO 4 F, Na 2 CoPO 4 F, Na 2 NiPO 4 F;
Fluorosulfates such as NaFeSO 4 F, NaMnSO 4 F, NaCoSO 4 F, NaFeSO 4 F;
Borates such as NaFeBO 4 , Na 3 Fe 2 (BO 4 ) 3 ;
Na 3 FeF 6, Na (the M 7 1 or more transition metal elements, 2 ≦ h ≦ 3) 2 MnF fluoride represented by Na h M 7 F 6 etc. 6; and the like.
　本発明において、前記正極活物質としては、以下の式（Ａ）で表される複合金属酸化物を好ましく用いることができる。以下の式（Ａ）で表される複合金属酸化物を正極活物質として用いることで、電池の充放電容量を向上させることができる。
　ＮａａＭ１ ｂＭ２Ｏ２　　　　　（Ａ）
　（ここで、Ｍ１は、Ｍｇ、Ｃａ、ＳｒおよびＢａからなる群より選ばれる１種以上の元素を表し、Ｍ２は、Ｍｎ、Ｆｅ、Ｃｏ、Ｃｒ、Ｖ、ＴｉおよびＮｉからなる群より選ばれる１種以上の元素を表し、ａは０．５以上１以下であり、ｂは０以上０．５以下であり、かつａ＋ｂは０．５以上１以下である。） In the present invention, a composite metal oxide represented by the following formula (A) can be preferably used as the positive electrode active material. By using the composite metal oxide represented by the following formula (A) as the positive electrode active material, the charge / discharge capacity of the battery can be improved.
Na a M 1 b M 2 O 2 (A)
(Here, M 1 represents one or more elements selected from the group consisting of Mg, Ca, Sr and Ba, and M 2 represents a group consisting of Mn, Fe, Co, Cr, V, Ti and Ni. Represents one or more selected elements, a is 0.5 or more and 1 or less, b is 0 or more and 0.5 or less, and a + b is 0.5 or more and 1 or less.
＜導電材＞
　前記導電材としては、炭素材料を用いることができる。炭素材料として、カーボンブラック（例えば、アセチレンブラック、ケッチェンブラック、ファーネスブラック等）、繊維状炭素材料（カーボンナノチューブ、カーボンナノファイバー、気相成長炭素繊維等）などをあげることができる。上記炭素材料は、表面積が大きく、電極合剤中に少量添加されることにより、得られる電極内部の導電性を高め、充放電効率および大電流放電特性を向上させることも可能である。通常、正極合剤中の導電材の割合は、正極活物質１００重量部に対して４~２０重量部であり、２種以上含有してもよい。 <Conductive material>
A carbon material can be used as the conductive material. Examples of the carbon material include carbon black (for example, acetylene black, ketjen black, furnace black), fibrous carbon material (carbon nanotube, carbon nanofiber, vapor grown carbon fiber, etc.) and the like. The carbon material has a large surface area, and when added in a small amount in the electrode mixture, it is possible to improve the conductivity inside the resulting electrode and improve the charge / discharge efficiency and large current discharge characteristics. Usually, the proportion of the conductive material in the positive electrode mixture is 4 to 20 parts by weight with respect to 100 parts by weight of the positive electrode active material, and two or more kinds may be contained.
＜バインダー＞
　前記の電極に用いられるバインダーとしては、例えば、フッ素化合物の重合体や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などがあげられる。 <Binder>
Examples of the binder used for the electrode include a polymer of a fluorine compound and an addition polymer of a monomer containing an ethylenic double bond not containing a fluorine atom.
　前記バインダーのガラス転移温度は−５０~２５℃が好ましい。ガラス転移温度を上記範囲内とすることにより、得られる電極の柔軟性を向上させ、また、低温環境下においても十分使用可能なナトリウム二次電池を得ることができる。 The glass transition temperature of the binder is preferably -50 to 25 ° C. By setting the glass transition temperature within the above range, the flexibility of the obtained electrode can be improved, and a sodium secondary battery that can be sufficiently used even in a low temperature environment can be obtained.
　本発明において、バインダーの好ましい例としては、
　ポリテトラフルオロエチレン、ポリクロロトリフルオロエチレン、テトラフルオロエチレン−パーフルオロアルキルビニルエーテル共重合体、エチレン−テトラフルオロエチレン共重合体、エチレン−クロロトリフルオロエチレン共重合体、テトラフルオロエチレン−ヘキサフルオロプロピレン共重合体等のフッ素樹脂；
　フッ化ビニリデン−ヘキサフルオロプロピレン共重合体、フッ化ビニリデン−テトラフルオロエチレン共重合体、フッ化ビニリデン−ヘキサフルオロプロピレン−テトラフルオロエチレン共重合体、フッ化ビニリデン−ペンタフルオロプロピレン共重合体、フッ化ビニリデン−ペンタフルオロプロピレン−テトラフルオロエチレン共重合体、フッ化ビニリデン−パーフルオロメチルビニルエーテル−テトラフルオロエチレン共重合体、フッ化ビニリデン−クロロトリフルオロエチレン共重合体等のフッ素ゴム；
　ポリアクリル酸、ポリアクリル酸アルカリ塩（ポリアクリル酸ナトリウム、ポリアクリル酸カリウム、ポリアクリル酸リチウム等）、ポリアクリル酸アルキル（アルキル部分の炭素数は１から２０）、アクリル酸−アクリル酸アルキル（アルキル部分の炭素数は１から２０）共重合体、ポリアクリロニトリル、アクリル酸−アクリル酸アルキル−アクリロニトリル共重合体、ポリアクリルアミド、アクリロニトリル−ブタジエン共重合体、アクリロニトリル−ブタジエン共重合体水素化物等のアクリル系ポリマー；
　ポリメタクリル酸、ポリメタクリル酸アルキル（アルキル基はアルキル部分の炭素数は１から２０）、メタクリル酸−メタクリル酸アルキル共重合体等のメタクリル系ポリマー；
　ポリビニルアルコール（部分ケン化または完全ケン化）、エチレン−ビニルアルコール共重合体、ポリビニルピロリドン、エチレン−酢酸ビニル共重合体、エチレン−酢酸ビニル−アクリル酸アルキル（アルキル基はアルキル部分の炭素数は１から２０）共重合体、エチレン−メタクリル酸共重合体、エチレン−アクリル酸共重合体、エチレン−メタクリル酸アルキル共重合体、エチレン−アクリル酸アルキル共重合体、エチレン−アクリロニトリル共重合体等のオレフィン系ポリマー；
　アクリロニトリル−スチレン−ブタジエン共重合体、スチレン、アクリロニトリル共重合体、スチレン−ブタジエン共重合体、スチレン−ブタジエン共重合体水素化物等のスチレン含有ポリマーがあげられる。
　特に、ハロゲン化ビニリデン由来の構造単位を有する共重合体を用いた場合、電極合剤密度の高い電極が得られやすく、電池の体積エネルギー密度が向上するため好ましい。 In the present invention, preferred examples of the binder include
Polytetrafluoroethylene, polychlorotrifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, ethylene-tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer Fluororesins such as polymers;
Vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-pentafluoropropylene copolymer, fluoride Fluoro rubbers such as vinylidene-pentafluoropropylene-tetrafluoroethylene copolymer, vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene copolymer, vinylidene fluoride-chlorotrifluoroethylene copolymer;
Polyacrylic acid, polyacrylic acid alkali salts (sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, etc.), alkyl polyacrylate (the alkyl part has 1 to 20 carbon atoms), acrylic acid-alkyl acrylate ( The alkyl moiety has 1 to 20 carbon atoms, such as copolymers, polyacrylonitrile, acrylic acid-alkyl acrylate-acrylonitrile copolymers, polyacrylamides, acrylonitrile-butadiene copolymers, acrylonitrile-butadiene copolymer hydrides, etc. Based polymers;
Methacrylic polymers such as polymethacrylic acid, polyalkylmethacrylate (the alkyl group has 1 to 20 carbon atoms in the alkyl moiety), methacrylic acid-alkylmethacrylate copolymer;
Polyvinyl alcohol (partially or completely saponified), ethylene-vinyl alcohol copolymer, polyvinylpyrrolidone, ethylene-vinyl acetate copolymer, ethylene-vinyl acetate-alkyl acrylate (the alkyl group has 1 carbon atom in the alkyl moiety) 20) Olefin such as copolymer, ethylene-methacrylic acid copolymer, ethylene-acrylic acid copolymer, ethylene-alkyl methacrylate copolymer, ethylene-alkyl acrylate copolymer, ethylene-acrylonitrile copolymer Based polymers;
Examples thereof include styrene-containing polymers such as acrylonitrile-styrene-butadiene copolymer, styrene, acrylonitrile copolymer, styrene-butadiene copolymer, and styrene-butadiene copolymer hydride.
In particular, when a copolymer having a structural unit derived from vinylidene halide is used, an electrode having a high electrode mixture density is easily obtained, and the volume energy density of the battery is improved.
＜正極の製造方法＞
　正極は、例えば、ナトリウムイオンをドープかつ脱ドープできる正極活物質を含む正極合剤を、正極集電体に担持することで製造される。正極集電体に正極合剤を担持する方法としては、例えば、正極活物質、導電材、バインダーおよび溶媒を混練して正極合剤ペーストを作製し、得られた正極合剤ペーストを、集電体へ塗布、乾燥する方法があげられる。正極合剤ペーストを、集電体へ塗布する方法としては特に制限されない。例えば、スリットダイ塗工法、スクリーン塗工法、カーテン塗工法、ナイフ塗工法、グラビア塗工法、静電スプレー法等の方法があげられる。また、塗布後に行う乾燥は、熱処理によって行ってもよいし、送風乾燥、真空乾燥などにより行ってもよい。熱処理により乾燥を行う場合には、その温度は、通常５０~１５０℃程度である。また、乾燥後にプレスを行ってもよい。プレス方法は、金型プレスやロールプレスなどの方法をあげることができる。以上にあげた方法により、電極を製造することができる。また、電極合剤の厚みは、通常５~５００μｍ程度である。 <Method for producing positive electrode>
The positive electrode is manufactured, for example, by supporting a positive electrode mixture containing a positive electrode active material that can be doped and dedoped with sodium ions on a positive electrode current collector. As a method for supporting the positive electrode mixture on the positive electrode current collector, for example, a positive electrode active material, a conductive material, a binder and a solvent are kneaded to prepare a positive electrode mixture paste, and the obtained positive electrode mixture paste is collected into a current collector. A method of applying to the body and drying is mentioned. The method for applying the positive electrode mixture paste to the current collector is not particularly limited. Examples thereof include slit die coating method, screen coating method, curtain coating method, knife coating method, gravure coating method, electrostatic spray method and the like. Moreover, the drying performed after application may be performed by heat treatment, or may be performed by air drying, vacuum drying, or the like. When drying is performed by heat treatment, the temperature is usually about 50 to 150 ° C. Moreover, you may press after drying. Examples of the pressing method include a mold press and a roll press. An electrode can be manufactured by the method mentioned above. The thickness of the electrode mixture is usually about 5 to 500 μm.
　前記正極合剤ペーストにおける正極合剤成分の割合、すなわち、正極合剤ペースト中の正極活物質、導電材およびバインダーの合計の割合は、得られる電極の厚み、塗布性の観点から、通常４０~７０重量％である。 The ratio of the positive electrode mixture component in the positive electrode mixture paste, that is, the total ratio of the positive electrode active material, the conductive material, and the binder in the positive electrode mixture paste is usually 40 to 40 from the viewpoint of the thickness of the obtained electrode and applicability. 70% by weight.
　本発明の正極において、集電体としては、Ａｌ、Ｎｉ、ステンレスなどの導電体をあげることができ、薄膜に加工しやすく、安価であるという点でＡｌが好ましい。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およびエンボス状であるもの、ならびに、これらを組み合わせたもの（例えば、メッシュ状平板など）があげられる。集電体表面にエッチング処理により凹凸を形成させてもよい。 In the positive electrode of the present invention, examples of the current collector include Al, Ni, stainless steel and the like, and Al is preferable in that it is easy to process into a thin film and is inexpensive. The shape of the current collector is, for example, 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 flat plate). Can be given. Concavities and convexities may be formed on the surface of the current collector by etching.
＜正極活物質の製造方法＞
　正極活物質の一例であるナトリウム含有遷移金属酸化物は、焼成により本発明に用いられるナトリウム含有遷移金属酸化物となり得る組成を有する金属含有化合物の混合物を焼成することによって製造できる。具体的には、対応する金属元素を含有する金属含有化合物を所定の組成となるように秤量し混合した後に、得られた混合物を焼成することによって製造できる。例えば、好ましい金属元素比の一つであるＮａ：Ｍｎ：Ｆｅ：Ｎｉ＝１：０．３：０．４：０．３で表される金属元素比を有するナトリウム含有遷移金属酸化物は、Ｎａ２ＣＯ３、ＭｎＯ２、Ｆｅ３Ｏ４、Ｎｉ２Ｏ３の各原料を、Ｎａ：Ｍｎ：Ｆｅ：Ｎｉのモル比が１：０．３：０．４：０．３となるように秤量し、それらを混合し、得られた混合物を焼成することによって製造できる。ナトリウム含有遷移金属酸化物がＭ１（Ｍ１は、Ｍｇ、Ｃａ、ＳｒおよびＢａからなる群より選ばれる１種以上の元素）を含有するときは、混合時に、Ｍ１を含有する原料を追加すればよい。 <Method for producing positive electrode active material>
The sodium-containing transition metal oxide, which is an example of the positive electrode active material, can be produced by firing a mixture of metal-containing compounds having a composition that can be used for the sodium-containing transition metal oxide used in the present invention by firing. Specifically, the metal-containing compound containing the corresponding metal element can be produced by weighing and mixing so as to have a predetermined composition, and then firing the resulting mixture. For example, a sodium-containing transition metal oxide having a metal element ratio represented by Na: Mn: Fe: Ni = 1: 0.3: 0.4: 0.3, which is one of the preferred metal element ratios, is Na 2 CO 3 , MnO 2 , Fe 3 O 4 , and Ni 2 O 3 are weighed so that the molar ratio of Na: Mn: Fe: Ni is 1: 0.3: 0.4: 0.3 And mixing them and firing the resulting mixture. When the sodium-containing transition metal oxide contains M 1 (M 1 is one or more elements selected from the group consisting of Mg, Ca, Sr and Ba), a raw material containing M 1 is added during mixing. do it.
　本発明に用いられるナトリウム含有遷移金属化合物を製造するために用いることができる金属含有化合物としては、酸化物、ならびに高温で分解および／または酸化したときに酸化物になり得る化合物、例えば水酸化物、炭酸塩、硝酸塩、ハロゲン化物またはシュウ酸塩を用いることができる。ナトリウム化合物としては、水酸化ナトリウム、塩化ナトリウム、硝酸ナトリウム、過酸化ナトリウム、硫酸ナトリウム、炭酸水素ナトリウム、蓚酸ナトリウムおよび炭酸ナトリウムからなる群より選ばれる１種以上の化合物をあげることができ、これらの水和物をあげることもできる。取り扱い性の観点で、より好ましくは炭酸ナトリウムである。マンガン化合物としてはＭｎＯ２が好ましく、鉄化合物としてはＦｅ３Ｏ４が好ましく、ニッケル化合物としてはＮｉ２Ｏ３が好ましい。また、これらの金属含有化合物は、水和物であってもよい。 Examples of the metal-containing compound that can be used to produce the sodium-containing transition metal compound used in the present invention include oxides and compounds that can be converted to oxides when decomposed and / or oxidized at high temperatures, such as hydroxides. , Carbonates, nitrates, halides or oxalates can be used. Examples of the sodium compound include one or more compounds selected from the group consisting of sodium hydroxide, sodium chloride, sodium nitrate, sodium peroxide, sodium sulfate, sodium bicarbonate, sodium oxalate, and sodium carbonate. Hydrates can also be given. From the viewpoint of handleability, sodium carbonate is more preferable. The manganese compound is preferably MnO 2 , the iron compound is preferably Fe 3 O 4 , and the nickel compound is preferably Ni 2 O 3 . These metal-containing compounds may be hydrates.
　金属含有化合物の混合物は、例えば以下の沈殿法により金属含有化合物の前駆体を得、得られた金属含有化合物の前駆体と前記ナトリウム化合物とを混合して得ることができる。
　具体的には、Ｍ２（ここで、Ｍ２は前記と同義）の原料として、塩化物、硝酸塩、酢酸塩、蟻酸塩、蓚酸塩等の化合物を用いて、これらを水に溶解し、沈殿剤と接触させることで金属含有化合物の前駆体を含有した沈殿物を得ることができる。これらの原料の中でも、塩化物が好ましい。また、水に溶解し難い原料を用いる場合、例えば、原料として、酸化物、水酸化物、金属材料を用いる場合には、これらの原料を、塩酸、硫酸、硝酸等の酸またはこれらの水溶液に溶解させて、Ｍ２を含有する水溶液を得ることもできる。 The mixture of metal-containing compounds can be obtained, for example, by obtaining a precursor of a metal-containing compound by the following precipitation method, and mixing the obtained precursor of the metal-containing compound and the sodium compound.
Specifically, compounds such as chloride, nitrate, acetate, formate, and oxalate are used as raw materials for M 2 (where M 2 is as defined above), and these are dissolved in water and precipitated. A precipitate containing a precursor of a metal-containing compound can be obtained by contacting with an agent. Of these raw materials, chloride is preferred. In addition, when using raw materials that are difficult to dissolve in water, for example, when using oxides, hydroxides, and metal materials as raw materials, these raw materials are added to acids such as hydrochloric acid, sulfuric acid, nitric acid, or aqueous solutions thereof. dissolved, it is also possible to obtain an aqueous solution containing M 2.
　さらに、前記沈殿剤としては、ＬｉＯＨ（水酸化リチウム）、ＮａＯＨ（水酸化ナトリウム）、ＫＯＨ（水酸化カリウム）、Ｌｉ２ＣＯ３（炭酸リチウム）、Ｎａ２ＣＯ３（炭酸ナトリウム）、Ｋ２ＣＯ３（炭酸カリウム）、（ＮＨ４）２ＣＯ３（炭酸アンモニウム）および（ＮＨ２）２ＣＯ（尿素）からなる群より選ばれる化合物を１種以上用いることができ、該化合物の水和物を１種以上用いてもよく、化合物と水和物とを併用してもよい。また、これらの沈殿剤を水に溶かして、水溶液で用いることが好ましい。水溶液中の沈殿剤の濃度は、０．５~１０モル／Ｌ程度、好ましくは、１~８モル／Ｌ程度である。また、沈殿剤としてはＫＯＨを用いることが好ましく、より好ましくは、これを水に溶かしたＫＯＨ水溶液である。また、水溶液の沈殿剤として、アンモニア水をあげることもでき、これと前記化合物の水溶液とを併用してもよい。 Furthermore, as the precipitant, LiOH (lithium hydroxide), NaOH (sodium hydroxide), KOH (potassium hydroxide), Li 2 CO 3 (lithium carbonate), Na 2 CO 3 (sodium carbonate), K 2 CO One or more compounds selected from the group consisting of 3 (potassium carbonate), (NH 4 ) 2 CO 3 (ammonium carbonate) and (NH 2 ) 2 CO (urea) can be used, and hydrates of the compounds can be used. 1 or more types may be used and a compound and a hydrate may be used together. Moreover, it is preferable to dissolve these precipitants in water and use them in an aqueous solution. The concentration of the precipitating agent in the aqueous solution is about 0.5 to 10 mol / L, preferably about 1 to 8 mol / L. Moreover, it is preferable to use KOH as a precipitant, More preferably, it is the KOH aqueous solution which melt | dissolved this in water. Moreover, ammonia water can be mention | raise | lifted as a precipitation agent of aqueous solution, and this and the aqueous solution of the said compound may be used together.
　Ｍ２を含有する水溶液と沈殿剤との接触方法としては、Ｍ２を含有する水溶液に、沈殿剤または沈殿剤の水溶液を添加する方法、沈殿剤の水溶液に、Ｍ２を含有する水溶液を添加する方法、水に、Ｍ２を含有する水溶液および沈殿剤または沈殿剤の水溶液を添加する方法をあげることができる。これらの添加時には、攪拌を伴うことが好ましい。また、上記の接触方法の中では、水溶液状の沈殿剤に、Ｍ２を含有する水溶液を添加する方法が、ｐＨを保ちやすく、粒径を制御しやすい点で好ましい。この場合、沈殿剤の水溶液に、Ｍ２を含有する水溶液を添加していくに従い、そのｐＨが低下していく傾向にあるが、このｐＨが９以上、好ましくは１０以上となるように調節しながら、Ｍ２を含有する水溶液を添加するのが好ましい。また、この調節は、沈殿剤の水溶液を添加することによっても行うことができる。 The method of contacting the aqueous solution with a precipitating agent containing M 2, to an aqueous solution containing M 2, a method of adding an aqueous solution of precipitant or precipitant, an aqueous solution of the precipitating agent, adding an aqueous solution containing M 2 And a method of adding an aqueous solution containing M 2 and a precipitating agent or an aqueous solution of a precipitating agent to water. At the time of these additions, it is preferable to involve stirring. Among the above contact methods, the method of adding an aqueous solution containing M 2 to the aqueous precipitation agent is preferable in terms of easy maintenance of pH and easy control of the particle size. In this case, as the aqueous solution containing M 2 is added to the aqueous solution of the precipitant, the pH tends to decrease, but the pH is adjusted to 9 or more, preferably 10 or more. while, preferably added an aqueous solution containing M 2. This adjustment can also be performed by adding an aqueous solution of a precipitant.
　上記の接触により、沈殿物を得ることができる。この沈殿物は、金属含有化合物の前駆体を含有する。 A precipitate can be obtained by the above contact. This precipitate contains a precursor of a metal-containing compound.
　また、Ｍ２を含有する水溶液と沈殿剤との接触後は、通常、スラリーとなり、これを固液分離して、沈殿物を回収する。固液分離はいかなる方法によってもよいが、操作性の観点では、ろ過などの固液分離による方法が好ましく用いられ、噴霧乾燥などの加熱して液体分を揮発させる方法を用いてもよい。また、回収された沈殿物について、洗浄、乾燥などを行ってもよい。固液分離後に得られる沈殿物には、過剰な沈殿剤の成分が付着していることもあり、洗浄により当該成分を減らすことができる。洗浄のときに用いる洗浄液は、水が好ましく、アルコール、アセトンなどの水溶性有機溶媒を用いてもよい。また、乾燥は、加熱乾燥によって行えばよく、送風乾燥、真空乾燥等によってもよい。加熱乾燥によって行う場合には、通常５０~３００℃で行い、１００~２００℃程度でで行うのが好ましい。また、洗浄、乾燥は２回以上行ってもよい。 Moreover, after contact with the aqueous solution and the precipitating agent containing M 2 is usually becomes slurry, which was solid-liquid separation, the precipitate is collected. Solid-liquid separation may be performed by any method, but from the viewpoint of operability, a method by solid-liquid separation such as filtration is preferably used, and a method of volatilizing the liquid by heating such as spray drying may be used. Moreover, you may perform washing | cleaning, drying, etc. about the collect | recovered deposit. The precipitate obtained after the solid-liquid separation may have an excessive component of the precipitant attached thereto, and the component can be reduced by washing. The cleaning liquid used for cleaning is preferably water, and a water-soluble organic solvent such as alcohol or acetone may be used. Further, the drying may be performed by heat drying, and may be performed by air drying, vacuum drying, or the like. When it is carried out by heat drying, it is usually carried out at 50 to 300 ° C. and preferably at about 100 to 200 ° C. Moreover, you may perform washing | cleaning and drying twice or more.
　ナトリウム化合物と金属含有化合物の前駆体との混合方法としては、乾式混合、湿式混合のいずれによってもよいが、簡便性の観点では、乾式混合が好ましい。混合装置としては、攪拌混合、Ｖ型混合機、Ｗ型混合機、リボン混合機、ドラムミキサーおよびボールミルをあげることができる。また、焼成は、用いるナトリウム化合物の種類にもよるが、通常４００~１２００℃程度の温度で保持して行えばよく、好ましくは５００~１０００℃程度である。また、前記保持温度で保持する時間は、通常０．１~２０時間であり、好ましくは０．５~１０時間である。前記保持温度までの昇温速度は、通常５０~４００℃／時間であり、前記保持温度から室温までの降温速度は、通常１０~４００℃／時間である。また、焼成は、大気、酸素、窒素、アルゴンまたはそれらの混合ガスの雰囲気下で行うことができるが、大気雰囲気下が好ましい。 As a method for mixing the sodium compound and the precursor of the metal-containing compound, either dry mixing or wet mixing may be used, but from the viewpoint of simplicity, dry mixing is preferable. Examples of the mixing apparatus include stirring and mixing, a V-type mixer, a W-type mixer, a ribbon mixer, a drum mixer, and a ball mill. The firing may be carried out usually at a temperature of about 400 to 1200 ° C., preferably about 500 to 1000 ° C., although it depends on the type of sodium compound used. The time for holding at the holding temperature is usually 0.1 to 20 hours, preferably 0.5 to 10 hours. The rate of temperature rise to the holding temperature is usually 50 to 400 ° C./hour, and the rate of temperature drop from the holding temperature to room temperature is usually 10 to 400 ° C./hour. Moreover, although baking can be performed in the atmosphere of air | atmosphere, oxygen, nitrogen, argon, or those mixed gas, an atmospheric condition is preferable.
　金属含有化合物として、フッ化物、塩化物等のハロゲン化物等を適量用いることによって、生成する複合金属酸化物の結晶性、複合金属酸化物を構成する粒子の平均粒径を制御することができる。この場合、ハロゲン化物は、反応促進剤（フラックス）としての役割を果たす場合もある。フラックスとしては、例えばＮａＦ、ＭｎＦ３、ＦｅＦ２、ＮｉＦ２、ＣｏＦ２、ＮａＣｌ、ＭｎＣｌ２、ＦｅＣｌ２、ＦｅＣｌ３、ＮｉＣｌ２、ＣｏＣｌ２、ＮＨ４ＣｌおよびＮＨ４Ｉをあげることができ、これらを混合物の原料（金属含有化合物）として、または、混合物に適量添加して用いることができる。また、これらのフラックスは、水和物であってもよい。
　その他の反応促進剤である金属含有化合物として、Ｎａ２ＣＯ３、ＮａＨＣＯ３Ｂ２Ｏ３およびＨ３ＢＯ３をあげることができる。 By using an appropriate amount of a halide such as fluoride or chloride as the metal-containing compound, the crystallinity of the produced composite metal oxide and the average particle size of the particles constituting the composite metal oxide can be controlled. In this case, the halide may play a role as a reaction accelerator (flux). Examples of the flux include NaF, MnF 3 , FeF 2 , NiF 2 , CoF 2 , NaCl, MnCl 2 , FeCl 2 , FeCl 3 , NiCl 2 , CoCl 2 , NH 4 Cl and NH 4 I. Can be used as a raw material of the mixture (metal-containing compound) or by adding an appropriate amount to the mixture. These fluxes may be hydrates.
Examples of other metal-containing compounds that are reaction accelerators include Na 2 CO 3 , NaHCO 3 B 2 O 3, and H 3 BO 3 .
　本発明に用いられるナトリウム含有遷移金属化合物をナトリウム二次電池用正極活物質として用いる場合、上記のようにして得られるナトリウム含有遷移金属化合物に、ボールミル、ジェットミル、振動ミル等の工業的に通常用いられる装置を用いた粉砕を行い、洗浄、分級等を行って、粒度を調節することが好ましい。また、焼成を２回以上行ってもよい。また、ナトリウム含有遷移金属化合物の粒子表面をＳｉ、Ａｌ、Ｔｉ、Ｙ等を含有する無機物質で被覆する等の表面処理をしてもよい。 When the sodium-containing transition metal compound used in the present invention is used as a positive electrode active material for a sodium secondary battery, the sodium-containing transition metal compound obtained as described above is usually industrially used, such as a ball mill, a jet mill, and a vibration mill. It is preferable to adjust the particle size by performing pulverization using an apparatus to be used, washing, classification, and the like. Moreover, you may perform baking twice or more. Further, a surface treatment such as coating the particle surface of the sodium-containing transition metal compound with an inorganic substance containing Si, Al, Ti, Y or the like may be performed.
＜本発明のナトリウム二次電池−負極＞
　本発明のナトリウム二次電池で用いることができる負極としては、負極活物質を含む負極合剤を負極集電体に担持した電極、ナトリウムイオンをドープかつ脱ドープ可能なナトリウム金属またはナトリウム合金電極を用いることができる。負極活物質としては、前記のナトリウム金属またはナトリウム合金以外に、ナトリウムイオンをドープかつ脱ドープすることができるコークス類、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などの炭素材料、金属、があげられる。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、または微粉末の凝集体などのいずれでもよい。ここで、炭素材料は、導電材としての役割を果たす場合もある。 <Sodium secondary battery of the present invention-negative electrode>
As a negative electrode that can be used in the sodium secondary battery of the present invention, an electrode in which a negative electrode mixture containing a negative electrode active material is carried on a negative electrode current collector, a sodium metal or sodium alloy electrode that can be doped and dedoped with sodium ions, Can be used. As the negative electrode active material, in addition to the above-mentioned sodium metal or sodium alloy, carbon such as coke, carbon black, pyrolytic carbons, carbon fiber, and organic polymer compound fired body that can be doped and dedoped with sodium ions Materials and metals. The shape of the carbon material may be any of a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, or an aggregate of fine powder. Here, the carbon material may play a role as a conductive material.
　炭素材料としては、カーボンブラック、熱分解炭素類、炭素繊維、有機材料焼成体などの非黒鉛化炭素材料（以下、ハードカーボンともいうことがある。）をあげることができる。ハードカーボンとしては、Ｘ線回折法による層間距離ｄ（００２）が０．３６０ｎｍ以上０．３９５ｎｍ以下であり、ｃ軸方向の結晶子の大きさＬｃが１．３０ｎｍ以下であるものが好ましい。またラマン分光測定より得られるＲ値（ＩＤ／ＩＧ）が１．０７以上３以下であるものが好ましい。ここで、波長５３２ｎｍのレーザーを照射して、ラマン分光測定を行うことにより得られるラマンスペクトル（縦軸は任意単位の散乱光強度であり、横軸はラマンシフト波数（ｃｍ−１）である。）において、横軸１３００~１４００ｃｍ−１の範囲および横軸１５７０~１６２０ｃｍ−１の範囲のそれぞれに１つずつピークを有し、該スペクトルの６００~１７４０ｃｍ−１の波数範囲について、２つのローレンツ関数および１つのベースライン関数を用いてフィッティングを行って得られるフィッティング関数から、ベースライン関数を除去して得られるフィッティングスペクトルにおいて、横軸１３００~１４００ｃｍ−１の範囲における縦軸の最大値をＩＤ、横軸１５７０~１６２０ｃｍ−１の範囲における縦軸の最大値をＩＧとし、ＩＤをＩＧで除して、Ｒ値（ＩＤ／ＩＧ）が得られる。 Examples of the carbon material include non-graphitized carbon materials (hereinafter sometimes referred to as hard carbon) such as carbon black, pyrolytic carbons, carbon fibers, and fired organic materials. The hard carbon is preferably one having an interlayer distance d (002) by an X-ray diffraction method of 0.360 nm or more and 0.395 nm or less and a crystallite size Lc in the c-axis direction of 1.30 nm or less. Moreover, the R value (ID / IG) obtained by Raman spectroscopy is preferably 1.07 or more and 3 or less. Here, a Raman spectrum obtained by irradiating a laser having a wavelength of 532 nm and performing Raman spectroscopic measurement (the vertical axis is the scattered light intensity in an arbitrary unit, and the horizontal axis is the Raman shift wave number (cm −1 ). ) In the range of 1300 to 1400 cm -1 on the horizontal axis and one peak in the range of 1570 to 1620 cm -1 on the horizontal axis, and two Lorentz functions for the wave number range of 600 to 1740 cm -1 of the spectrum In the fitting spectrum obtained by removing the baseline function from the fitting function obtained by performing fitting using one baseline function, the maximum value of the vertical axis in the range of the horizontal axis 1300 to 1400 cm −1 is ID, the maximum value of the vertical axis in the range of the horizontal axis 1570 ~ 1620 cm -1 and IG, By dividing D by IG, R value (ID / IG) is obtained.
　ハードカーボンとしては、例えば、非黒鉛化炭素材料からなるカーボンマイクロビーズをあげることができ、具体的には、日本カーボン社製のＩＣＢ（商品名：ニカビーズ）があげられる。炭素材料を構成する粒子の形状としては、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、または微粒子の凝集体形状などがあげられる。炭素材料を構成する粒子の形状が球状である場合、その平均粒径は好ましくは０．０１μｍ以上３０μｍ以下であり、より好ましくは０．１μｍ以上２０μｍ以下である。 As the hard carbon, for example, carbon micro beads made of non-graphitized carbon material can be mentioned, and specifically, ICB (trade name: Nika beads) manufactured by Nippon Carbon Co., Ltd. can be mentioned. Examples of the shape of the particles constituting the carbon material include a flake shape such as natural graphite, a spherical shape such as mesocarbon microbeads, a fibrous shape such as graphitized carbon fiber, and an aggregate shape of fine particles. When the shape of the particles constituting the carbon material is spherical, the average particle diameter is preferably 0.01 μm or more and 30 μm or less, more preferably 0.1 μm or more and 20 μm or less.
　負極活物質に用いられる金属の例として、スズ、鉛、シリコン、ゲルマニウム、リン、ビスマス、アンチモンなどがあげられる。合金の例としては、上記金属からなる群から選ばれる２種以上の金属からなる合金、上記金属と遷移金属からなる群から選ばれる２種以上の金属からなる合金があげられ、また、Ｓｉ−Ｚｎ、Ｃｕ２Ｓｂ、Ｌａ３Ｎｉ２Ｓｎ７などの合金があげられる。これらの金属、合金は炭素材料と併用して集電体に担持されて、電極活物質として用いられる。 Examples of the metal used for the negative electrode active material include tin, lead, silicon, germanium, phosphorus, bismuth, and antimony. Examples of the alloy include an alloy composed of two or more metals selected from the group consisting of the above metals, an alloy composed of two or more metals selected from the group consisting of the above metals and transition metals, and Si— Examples of the alloy include Zn, Cu 2 Sb, and La 3 Ni 2 Sn 7 . These metals and alloys are used as an electrode active material by being carried on a current collector in combination with a carbon material.
　負極活物質に用いられる酸化物の例としては、Ｌｉ４Ｔｉ５Ｏ１２等があげられる。硫化物の例としては、ＴｉＳ２、ＮｉＳ２、ＦｅＳ２、Ｆｅ３Ｓ４等があげられる。窒化物の例としては、Ｎａ３Ｎ、Ｎａ２．６Ｃｏ０．４Ｎ等のＮａ３−ｘＭｘＮ（但し、Ｍは遷移金属元素、０≦ｘ≦３）等があげられる。 Examples of the oxide used for the negative electrode active material include Li 4 Ti 5 O 12 and the like. Examples of sulfides include TiS 2 , NiS 2 , FeS 2 , Fe 3 S 4 and the like. Examples of nitrides, Na 3 N, Na 2.6 Co 0.4 Na such as N 3-x M x N (where, M is a transition metal element, 0 ≦ x ≦ 3), and the like.
　負極活物質であるこれらの炭素材料、金属、酸化物、硫化物、窒化物は、併用してもよく、結晶質または非晶質のいずれでもよい。サイクル特性の観点からは、負極活物質としては、炭素材料を用いることが好ましく、ハードカーボンを用いることがより好ましい。 These carbon materials, metals, oxides, sulfides, and nitrides that are negative electrode active materials may be used in combination, and may be crystalline or amorphous. From the viewpoint of cycle characteristics, it is preferable to use a carbon material as the negative electrode active material, and it is more preferable to use hard carbon.
　これらの炭素材料、金属、酸化物、硫化物、窒化物は、主に、集電体に担持されて、電極として用いられる。 These carbon materials, metals, oxides, sulfides, and nitrides are mainly supported on current collectors and used as electrodes.
　負極合剤は、必要に応じて、バインダー、導電材を含有してもよい。バインダー、導電材としては、上記正極に用いられるバインダー、導電材と同様のものをあげることができる。 The negative electrode mixture may contain a binder and a conductive material as necessary. Examples of the binder and conductive material include the same binders and conductive materials used for the positive electrode.
　上記負極合剤に含まれるバインダーとしては、好ましくは、ポリアクリル酸、ポリアクリル酸ナトリウム、ポリアクリル酸リチウム、ポリアクリル酸カリウム、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、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、ポリフッ化ビニリデン、ポリテトラフルオロエチレン、フッ化ビニリデン−テトラフルオロエチレン共重合体、フッ化ビニリデン−ヘキサフルオロプロピレン−テトラフルオロエチレン共重合体等をあげることができ、これらは単独でも２種類以上を組み合わせて用いてもよい。負極合剤への電解液の濡れ性向上の観点から、負極合剤に含まれるバインダーとしては、ポリフッ化ビニリデン、フッ化ビニリデン−テトラフルオロエチレン共重合体、フッ化ビニリデン−ヘキサフルオロプロピレン−テトラフルオロエチレン共重合体からなる群から選ばれる１種以上を用いることが好ましい。 The binder contained in the negative electrode mixture is preferably polyacrylic acid, sodium polyacrylate, lithium polyacrylate, potassium polyacrylate, carboxymethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, ethylene-vinyl acetate. Copolymer, styrene-butadiene copolymer, polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, etc. These may be used alone or in combination of two or more. From the viewpoint of improving the wettability of the electrolyte solution to the negative electrode mixture, the binder contained in the negative electrode mixture includes polyvinylidene fluoride, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoro. It is preferable to use one or more selected from the group consisting of ethylene copolymers.
　負極合剤におけるバインダーの割合としては、炭素材料１００重量部に対し、通常０．５~３０重量部程度、好ましくは２~２０重量部程度である。 The ratio of the binder in the negative electrode mixture is usually about 0.5 to 30 parts by weight, preferably about 2 to 20 parts by weight with respect to 100 parts by weight of the carbon material.
　負極集電体としては、Ａｌ、Ｃｕ、Ｎｉおよびステンレスをあげることができ、薄膜に加工しやすく、安価であるという点でＡｌが好ましい。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およびエンボス状であるもの、ならびに、これらを組み合わせたもの（例えば、メッシュ状平板など）があげられる。集電体表面にエッチング処理による凹凸を形成させてもよい。 Examples of the negative electrode current collector include Al, Cu, Ni, and stainless steel, and Al is preferable because it can be easily processed into a thin film and is inexpensive. The shape of the current collector is, for example, 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 flat plate). Can be given. Concavities and convexities may be formed by etching on the current collector surface.
＜本発明のナトリウム二次電池−セパレータ＞
　本発明のナトリウム二次電池で用いることができるセパレータとしては例えば、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、フッ素樹脂、含窒素芳香族重合体などの材質からなる、多孔質フィルム、不織布、織布などの形態を有する材料を用いることができる。また、これらの材質を２種以上用いた単層または積層セパレータとしてもよい。セパレータとしては、例えば特開２０００−３０６８６号公報、特開平１０−３２４７５８号公報等に記載のセパレータをあげることができる。セパレータの厚みは、電池の体積エネルギー密度が上がり、内部抵抗が小さくなるという点で、機械的強度が保たれる限り薄いほど好ましい。セパレータの厚みは一般に、５~２００μｍ程度が好ましく、より好ましくは５~４０μｍ程度である。 <Sodium Secondary Battery-Separator of the Present Invention>
Examples of the separator that can be used in the sodium secondary battery of the present invention include porous films, nonwoven fabrics, woven fabrics, and the like made of materials such as polyolefin resins such as polyethylene and polypropylene, fluororesins, and nitrogen-containing aromatic polymers. A material having a form can be used. Moreover, it is good also as a single layer or laminated separator which used 2 or more types of these materials. Examples of the separator include those described in JP 2000-30686 A, JP 10-324758 A, and the like. The thickness of the separator is preferably as thin as possible as long as the mechanical strength is maintained in that the volume energy density of the battery is increased and the internal resistance is reduced. In general, the thickness of the separator is preferably about 5 to 200 μm, more preferably about 5 to 40 μm.
　セパレータは、好ましくは、熱可塑性樹脂を含有する多孔質フィルムを有する。二次電池においては、通常、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（シャットダウンする。）ことが重要である。したがってセパレータは、通常の使用温度を越えた場合に、できるだけ低温でシャットダウンする（セパレータが、熱可塑性樹脂を含有する多孔質フィルムを有する場合には、多孔質フィルムの微細孔を閉塞する。）こと、およびシャットダウンした後、ある程度の高温まで電池内の温度が上昇しても、その温度により破膜することなく、シャットダウンした状態を維持すること、換言すれば、耐熱性が高いことが求められる。セパレータとして、耐熱樹脂を含有する耐熱多孔層と熱可塑性樹脂を含有する多孔質フィルムとが積層されてなる積層多孔質フィルムを有するセパレータを用いることにより、本発明の二次電池の熱破膜をより防ぐことが可能となる。ここで、耐熱多孔層は、多孔質フィルムの両面に積層されていてもよい。 The separator preferably has a porous film containing a thermoplastic resin. In a secondary battery, normally, when an abnormal current flows in the battery due to a short circuit between the positive electrode and the negative electrode, the current is interrupted to prevent an excessive current from flowing (shut down). is important. Therefore, the separator shuts down at the lowest possible temperature when the normal use temperature is exceeded (when the separator has a porous film containing a thermoplastic resin, the micropores of the porous film are blocked). Even after the shutdown, even if the temperature in the battery rises to a certain high temperature, it is required to maintain the shutdown state without breaking the film due to the temperature, in other words, to have high heat resistance. By using a separator having a laminated porous film in which a heat resistant porous layer containing a heat resistant resin and a porous film containing a thermoplastic resin are laminated as a separator, the thermal breakage of the secondary battery of the present invention It becomes possible to prevent more. Here, the heat-resistant porous layer may be laminated on both surfaces of the porous film.
　以下、本発明を実施例によりさらに詳細に説明する。なお、ナトリウム含有遷移金属化合物およびハードカーボンの各種評価は、以下の測定により行った。 Hereinafter, the present invention will be described in more detail with reference to examples. Various evaluations of the sodium-containing transition metal compound and hard carbon were performed by the following measurements.
１．ナトリウム含有遷移金属化合物およびハードカーボンの粉末Ｘ線回折測定
　ナトリウム含有遷移金属化合物の粉末Ｘ線回折測定は株式会社リガク製ＲＩＮＴ２５００ＴＴＲ型を用いて行った。測定は、ナトリウム含有遷移金属化合物を専用のホルダーに充填し、ＣｕＫα線源を用いて、回折角２θ＝１０~９０°の範囲にて行い、粉末Ｘ線回折図形を得た。ハードカーボンについても上記と同様の操作にて粉末Ｘ線回折図形を得た。 1. Powder X-ray diffraction measurement of sodium-containing transition metal compound and hard carbon Powder X-ray diffraction measurement of sodium-containing transition metal compound was performed using RINT2500TTR type manufactured by Rigaku Corporation. The measurement was performed by filling a sodium-containing transition metal compound in a dedicated holder and using a CuKα ray source in a diffraction angle range of 2θ = 10 to 90 ° to obtain a powder X-ray diffraction pattern. For hard carbon, a powder X-ray diffraction pattern was obtained in the same manner as described above.
２．ナトリウム含有遷移金属化合物の組成分析
　粉末を塩酸に溶解させた後、誘導結合プラズマ発光分析法（ＳＩＩ製、ＳＰＳ３０００、以下ＩＣＰ−ＡＥＳと呼ぶことがある。）を用いて測定した。 2. Composition analysis of sodium-containing transition metal compound After the powder was dissolved in hydrochloric acid, it was measured using an inductively coupled plasma emission analysis method (manufactured by SII, SPS3000, hereinafter sometimes referred to as ICP-AES).
３．非水電解液の粒度分布測定
　非水電解液の粒度分布測定は、Ｚｅｔａｓｉｚｅｒ　Ｎａｎｏ（Ｎａｎｏ　ＺＳ（ＺＥＮ３６００）、シスメックス株式会社製）を用いて行った。測定にはガラス製キュベットを用い、２５℃で測定した。 3. Particle size distribution measurement of non-aqueous electrolyte The particle size distribution measurement of the non-aqueous electrolyte was performed using Zetasizer Nano (Nano ZS (ZEN3600), manufactured by Sysmex Corporation). The measurement was performed at 25 ° C. using a glass cuvette.
　＜製造例１＞（複合金属酸化物Ａ１および正極ＡＥ１の製造）
　ポリプロピレン製ビーカー内で、蒸留水３００ｍｌに、水酸化カリウム４４．８８ｇを添加し、攪拌により溶解し、水酸化カリウムを完全に溶解させ、水酸化カリウム水溶液（沈殿剤）を調製した。また、別のポリプロピレン製ビーカー内で、蒸留水３００ｍｌに、塩化鉄（ＩＩ）四水和物２１．２１ｇ、塩化ニッケル（ＩＩ）六水和物１９．０２ｇ、塩化マンガン（ＩＩ）四水和物１５．８３ｇを添加し、攪拌により溶解し、鉄−ニッケル−マンガン含有水溶液を得た。前記沈殿剤を攪拌しながら、これに前記鉄−ニッケル−マンガン含有水溶液を滴下することで、沈殿物が生成したスラリーを得た。次いで、該スラリーについて、ろ過・蒸留水洗浄を行い、１００℃で乾燥させて沈殿物を得た。沈殿物と炭酸ナトリウムと水酸化カルシウムとをモル比でＦｅ：Ｎａ：Ｃａ＝０．４：０．９９：０．０１となるようにして秤量した後、メノウ乳鉢を用いて乾式混合して混合物を得た。次いで、該混合物をアルミナ製焼成容器に入れ、電気炉を用いて大気雰囲気中８５０℃で６時間保持して焼成を行い、室温まで冷却し、複合金属酸化物Ａ１を得た。複合金属酸化物Ａ１の粉末Ｘ線回折分析を行うと、α−ＮａＦｅＯ２型の結晶構造に帰属されることがわかった。また、ＩＣＰ−ＡＥＳにより、複合金属酸化物Ａ１の組成を分析すると、Ｎａ：Ｃａ：Ｆｅ：Ｎｉ：Ｍｎのモル比は０．９９：０．０１：０．４：０．３：０．３であった。そして、上記のようにして得られた複合金属酸化物Ａ１と、導電材としてアセチレンブラック（ＨＳ１００、電気化学工業株式会社製）、バインダー溶液としてＶＴ４７１（ダイキン工業株式会社製）、溶媒としてＮＭＰ（キシダ化学株式会社製）とを用いて正極合剤ペーストを作製した。複合金属酸化物Ａ１：導電材：バインダー：ＮＭＰ＝９０：５：５：１００（重量比）の組成となるように秤量し、ディスパーマット（ＶＭＡ−ＧＥＴＺＭＡＮＮ社製）を用い４，０００ｒｐｍ、５分間攪拌、混合することで、正極合剤ペーストを得た。得られた正極合剤ペーストを、厚さ２０μｍのアルミ箔にドクターブレードを用いて塗工し、６０℃で２時間乾燥後、ロールプレス（ＳＡ−６０２、テスター産業株式会社製）を用いて、２００ｋＮ／ｍの圧力で圧延することで正極ＡＥ１を得た。 <Production Example 1> (Production of Composite Metal Oxide A 1 and Positive Electrode AE 1 )
In a polypropylene beaker, 44.88 g of potassium hydroxide was added to 300 ml of distilled water and dissolved by stirring to completely dissolve potassium hydroxide, thereby preparing an aqueous potassium hydroxide solution (precipitating agent). Further, in another polypropylene beaker, 21.21 g of iron (II) chloride tetrahydrate, 19.02 g of nickel (II) chloride hexahydrate, and manganese (II) chloride tetrahydrate were added to 300 ml of distilled water. 15.83 g was added and dissolved by stirring to obtain an iron-nickel-manganese-containing aqueous solution. While stirring the precipitant, the iron-nickel-manganese-containing aqueous solution was added dropwise thereto to obtain a slurry in which a precipitate was generated. Next, the slurry was filtered and washed with distilled water, and dried at 100 ° C. to obtain a precipitate. The precipitate, sodium carbonate, and calcium hydroxide were weighed so that the molar ratio of Fe: Na: Ca = 0.4: 0.99: 0.01, and then dry-mixed using an agate mortar. Got. Then the mixture was placed in an alumina calcination vessel, then calcined by holding for six hours at 850 ° C. in an air atmosphere using an electric furnace and then cooled to room temperature to obtain a composite metal oxide A 1. When a powder X-ray diffraction analysis of the composite metal oxide A 1 was performed, it was found that the composite metal oxide A 1 was assigned to the α-NaFeO 2 type crystal structure. Further, when the composition of the composite metal oxide A 1 is analyzed by ICP-AES, the molar ratio of Na: Ca: Fe: Ni: Mn is 0.99: 0.01: 0.4: 0.3: 0. 3. The composite metal oxide A 1 obtained as described above, acetylene black (HS100, manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductive material, VT471 (manufactured by Daikin Kogyo Co., Ltd.) as a binder solution, and NMP (as a solvent) A positive electrode mixture paste was prepared using Kida Chemical Co., Ltd.). Composite metal oxide A 1 : Conductive material: Binder: Weighed to have a composition of NMP = 90: 5: 5: 100 (weight ratio), and 4,000 rpm, 5 using a disperse mat (made by VMA-GETZMANN) A positive electrode mixture paste was obtained by stirring and mixing for a minute. The obtained positive electrode mixture paste was applied to a 20 μm thick aluminum foil using a doctor blade, dried at 60 ° C. for 2 hours, and then using a roll press (SA-602, manufactured by Tester Sangyo Co., Ltd.) A positive electrode AE 1 was obtained by rolling at a pressure of 200 kN / m.
＜製造例２＞（炭素材料Ｃ１および炭素電極ＣＥ１の製造）
　日本カーボン社製のＩＣＢ（商品名：ニカビーズ）を焼成炉に導入し、炉内をアルゴンガス雰囲気下とした後、アルゴンガスを毎分０．１Ｌ／ｇ（炭素材料の重量）の割合で流通させながら、室温から毎分５℃の速度で１６００℃まで昇温し、１６００℃で１時間保持した後、冷却し、炭素材料Ｃ１を得た。炭素材料Ｃ１の粉末Ｘ線回折測定より、層間距離ｄ（００２）は０．３６８ｎｍであり、ｃ軸方向の結晶子の大きさＬｃは１．１７ｎｍであることが分かった。また、ラマン分光測定より得られるＲ値（ＩＤ／ＩＧ）は１．４１であることが分かった。炭素材料Ｃ１、バインダーとしてポリフッ化ビニリデン（ＰＶｄＦ）（株式会社クレハ製、ＫＦポリマー　Ｗ＃１３００）、溶媒としてＮＭＰ（キシダ化学株式会社製）を用いた電極合剤ペーストを作製した。炭素材料Ｃ１：ＰＶｄＦ：ＮＭＰ＝９０：１０：１００（重量比）の組成となるように秤量し、ディスパーマット（ＶＭＡ−ＧＥＴＺＭＡＮＮ社製）を用い攪拌、混合することで、電極合剤ペーストを得た。回転羽の回転条件は、２，０００ｒｐｍ、１０分間とした。得られた電極合剤ペーストを、銅箔にドクターブレードを用いて塗工し、６０℃で２時間乾燥後、ロールプレスを用いて、１００ｋＮ／ｍで圧延することで炭素電極ＣＥ１を得た。 <Production Example 2> (Production of carbon material C 1 and carbon electrode CE 1 )
ICB (trade name: Nika beads) manufactured by Nippon Carbon Co., Ltd. was introduced into the firing furnace, and the inside of the furnace was placed in an argon gas atmosphere, and then argon gas was distributed at a rate of 0.1 L / g (weight of carbon material) per minute. The temperature was raised from room temperature to 1600 ° C. at a rate of 5 ° C. per minute, held at 1600 ° C. for 1 hour, and then cooled to obtain a carbon material C 1 . From powder X-ray diffraction measurement of the carbon material C 1, the interlayer distance d (002) is 0.368Nm, size Lc in the c-axis direction of the crystallite was found to be 1.17 nm. Moreover, it turned out that R value (ID / IG) obtained from a Raman spectroscopic measurement is 1.41. An electrode mixture paste was prepared using carbon material C 1 , polyvinylidene fluoride (PVdF) (manufactured by Kureha Co., Ltd., KF polymer W # 1300) as a binder, and NMP (manufactured by Kishida Chemical Co., Ltd.) as a solvent. Carbon material C 1 : PVdF: NMP = 90: 10: 100 (weight ratio) is weighed so as to have a composition, and is stirred and mixed using a disperse mat (VMA-GETZMANN Co., Ltd.). Obtained. The rotation conditions of the rotating blades were 2,000 rpm for 10 minutes. The obtained electrode mixture paste was applied to a copper foil using a doctor blade, dried at 60 ° C. for 2 hours, and then rolled at 100 kN / m using a roll press to obtain carbon electrode CE 1 . .
　＜実施例１＞（ナトリウム二次電池Ｂ１の製造）
　１Ｌ中に１．３モルのＮａＰＦ６を含むプロピレンカーボネート（ＰＣ）溶液（ＮａＰＦ６　ＰＣ）（キシダ化学株式会社製）と、フルオロエチレンカーボネート（ＦＥＣ）（キシダ化学株式会社製）とを９８：２（体積比）の割合で、あわせて２５ｍＬとなるようにスクリュー管（アズワン製、型番Ｎｏ．７）に取り、８０℃に加熱した状態で、全長２０ｍｍのポリテトラフルオロエチレン回転子を用い２５０ｒｐｍで、アルゴンガス雰囲気下で６時間攪拌し、非水電解液ＥＬ１（１Ｌ中に１．３モルのＮａＰＦ６を含むＰＣ／ＦＥＣ）を調整した。なお、ＰＣおよびＦＥＣの引火点は、キシダ化学株式会社発行の製品安全データシードにおいて、それぞれ１３５℃、１２２℃と開示されており、非水電解液ＥＬ１に対するＰＣとＦＥＣの割合は、９１体積％である。非水電解液ＥＬ１の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされ、ナトリウム塩が２５℃での飽和溶解度を超えて含まれていることを確認した。コインセル（宝泉株式会社製）の下側パーツの窪みに、直径１４．５ｍｍに打ち抜いた正極ＡＥ１を置き、負極として、直径１５．０ｍｍに打ち抜いた炭素電極ＣＥ１を、電解液に非水電解液ＥＬ１を、セパレータとしてポリエチレン多孔質フィルム（厚み２０μｍ）を用いてナトリウム二次電池Ｂ１を作製した。なお、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。 <Example 1> (Production of Sodium Secondary Battery B 1)
A propylene carbonate (PC) solution (NaPF 6 PC) containing 1.3 mol of NaPF 6 in 1 L (manufactured by Kishida Chemical Co., Ltd.) and fluoroethylene carbonate (FEC) (manufactured by Kishida Chemical Co., Ltd.) 98: 2 Take the screw tube (manufactured by ASONE, model No. 7) to a total volume ratio of 25 mL and heat at 80 ° C. using a polytetrafluoroethylene rotor with a total length of 20 mm at 250 rpm. The mixture was stirred for 6 hours under an argon gas atmosphere to prepare a non-aqueous electrolyte EL 1 (PC / FEC containing 1.3 mol of NaPF 6 in 1 L). The flash points of PC and FEC are disclosed as 135 ° C. and 122 ° C., respectively, in the product safety data seed issued by Kishida Chemical Co., Ltd. The ratio of PC and FEC to non-aqueous electrolyte EL 1 is 91 vol. %. As a result of measuring the particle size distribution of the non-aqueous electrolyte EL 1 , it was confirmed that particles were counted in a region of 10 nm or more and 200 nm or less, and that the sodium salt exceeded the saturation solubility at 25 ° C. A positive electrode AE 1 punched to a diameter of 14.5 mm is placed in a recess in the lower part of a coin cell (manufactured by Hosen Co., Ltd.), and a carbon electrode CE 1 punched to a diameter of 15.0 mm is used as the negative electrode in the electrolyte. the electrolyte EL 1, to produce a sodium secondary battery B 1 with polyethylene porous film (thickness 20 [mu] m) as a separator. The battery was assembled in a glove box in an argon atmosphere.
　＜実施例２＞（ナトリウム二次電池Ｂ２の製造）
　１Ｌ中に２．０モルのＮａＰＦ６を含むＰＣと、ＰＣ（キシダ化学株式会社製）と、ＦＥＣとを７４：２４：２（体積比）の割合とした以外は、実施例１と同様の操作で非水電解液ＥＬ２（１Ｌ中に１．５モルのＮａＰＦ６を含むＰＣ／ＦＥＣ）を調整した。非水電解液ＥＬ２に対するＰＣとＦＥＣの割合は、９０体積％である。非水電解液ＥＬ２の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされ、ナトリウム塩が２５℃での飽和溶解度を超えて含まれていることを確認した。電解液に非水電解液ＥＬ２を用いた以外は、実施例１と同様の操作でナトリウム二次電池Ｂ２を作製した。 <Example 2> (Production of Sodium Secondary Battery B 2)
The same as Example 1 except that PC containing 2.0 mol of NaPF 6 in 1 L, PC (manufactured by Kishida Chemical Co., Ltd.), and FEC were in a ratio of 74: 24: 2 (volume ratio). The non-aqueous electrolyte EL 2 (PC / FEC containing 1.5 mol of NaPF 6 in 1 L) was prepared by the operation. The ratio of PC and FEC to the non-aqueous electrolyte EL 2 is 90% by volume. As a result of measuring the particle size distribution of the non-aqueous electrolyte EL 2 , it was confirmed that particles were counted in a region of 10 nm or more and 200 nm or less and that the sodium salt was included exceeding the saturation solubility at 25 ° C. Except for using the non-aqueous electrolyte EL 2 in the electrolytic solution, to prepare a sodium secondary battery B 2 by operating the same manner as in Example 1.
　＜実施例３＞（ナトリウム二次電池Ｂ３の製造）
　１Ｌ中に２．０モルのＮａＰＦ６を含むＰＣと、ＦＥＣとを９８：２（体積比）の割合とした以外は、実施例１と同様の操作で、非水電解液ＥＬ３（１Ｌ中に２．０モルのＮａＰＦ６を含むＰＣ／ＦＥＣ溶液）を調整した。非水電解液ＥＬ３に対するＰＣとＦＥＣの割合は、８６体積％である。非水電解液ＥＬ３の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされ、ナトリウム塩が２５℃での飽和溶解度を超えて含まれていることを確認した。電解液に非水電解液ＥＬ３を用いた以外は、実施例１と同様の操作でナトリウム二次電池Ｂ３を作製した。 <Example 3> (Production of Sodium Secondary Battery B 3)
A non-aqueous electrolyte EL 3 (in 1 L) was prepared in the same manner as in Example 1 except that PC containing 2.0 mol of NaPF 6 in 1 L and FEC were in a ratio of 98: 2 (volume ratio). the PC / FEC solution) containing 2.0 mol of NaPF 6 in the adjustment. The ratio of PC and FEC to the non-aqueous electrolyte EL 3 is 86% by volume. As a result of measuring the particle size distribution of the non-aqueous electrolyte EL 3 , it was confirmed that the particles were counted in the region of 10 nm to 200 nm, and the sodium salt was included exceeding the saturation solubility at 25 ° C. Except for using the non-aqueous electrolyte solution EL 3 in the electrolytic solution, to prepare a sodium secondary battery B 3 in the same manner as in Example 1.
　＜実施例４＞（ナトリウム二次電池Ｂ４の製造）
　非水電解液ＥＬ４として１Ｌ中に２．０モルのＮａＰＦ６を含むＰＣを２５ｍＬとなるようにスクリュー管（アズワン製、型番Ｎｏ．７）に取り、８０℃に加熱した状態で、全長２０ｍｍのポリテトラフルオロエチレン回転子を用い２５０ｒｐｍで、アルゴンガス雰囲気下で６時間攪拌したものを用いた。非水電解液ＥＬ４に対するＰＣの割合は、８６体積％である。非水電解液ＥＬ４の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされ、ナトリウム塩が２５℃での飽和溶解度を超えて含まれていることを確認した。１Ｌ中に２．０モルのＮａＰＦ６を含むＰＣ（非水電解液ＥＬ４）を用いた以外は、実施例１と同様の操作でナトリウム二次電池Ｂ４を作製した。 <Example 4> (Preparation of Sodium Secondary Battery B 4)
PC containing 2.0 mol of NaPF 6 in 1 L as non-aqueous electrolyte EL 4 is taken into a screw tube (manufactured by ASONE, model No. 7) so as to be 25 mL, and heated to 80 ° C., with a total length of 20 mm. And a polytetrafluoroethylene rotator prepared by stirring at 250 rpm in an argon gas atmosphere for 6 hours. Percentage of PC relative to the non-aqueous electrolyte EL 4 is a 86% by volume. As a result of measuring the particle size distribution of the non-aqueous electrolyte EL 4 , it was confirmed that the particles were counted in the region of 10 nm or more and 200 nm or less, and the sodium salt was included exceeding the saturation solubility at 25 ° C. A sodium secondary battery B 4 was produced in the same manner as in Example 1 except that PC (nonaqueous electrolyte EL 4 ) containing 2.0 mol of NaPF 6 in 1 L was used.
　＜実施例５＞（ナトリウム二次電池Ｂ５の製造）
　１Ｌ中に２．０モルのＮａＰＦ６を含むＰＣに、１Ｌ中に２．５モルのＮａＰＦ６を含むＰＣとなるように、ＮａＰＦ６（Ｊｏｈｎｓｏｎ　Ｍａｔｔｈｅｙ社製）を加えた以外は、実施例１と同様の操作で、非水電解液ＥＬ５（１Ｌ中に２．５モルのＮａＰＦ６を含むＰＣ）を調整した。非水電解液ＥＬ５に対するＰＣの割合は、８２体積％である。非水電解液ＥＬ５の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされ、ナトリウム塩が２５℃での飽和溶解度を超えて含まれていることを確認した。電解液に非水電解液ＥＬ５を用いた以外は、実施例１と同様の操作でナトリウム二次電池Ｂ５を作製した。 <Example 5> (Production of Sodium Secondary Battery B 5)
Example 1 except that NaPF 6 (manufactured by Johnson Matthey) was added to a PC containing 2.0 mol of NaPF 6 in 1 L so as to be a PC containing 2.5 mol of NaPF 6 in 1 L. The non-aqueous electrolyte EL 5 (PC containing 2.5 mol of NaPF 6 in 1 L) was prepared in the same manner as in Example 1. Percentage of PC relative to the non-aqueous electrolyte EL 5 is 82% by volume. As a result of measuring the particle size distribution of the non-aqueous electrolyte EL 5 , it was confirmed that the particles were counted in a region of 10 nm to 200 nm, and the sodium salt was contained exceeding the saturation solubility at 25 ° C. Except for using the non-aqueous electrolyte EL 5 in the electrolytic solution, to prepare a sodium secondary battery B 5 in the same manner as in Example 1.
　＜実施例６＞（ナトリウム二次電池Ｂ６の製造）
　１Ｌ中に１．０モルのＮａＮ（ＳＯ２ＣＦ３）２を含むＰＣ（キシダ化学株式会社製）に、１Ｌ中に２．０モルのＮａＮ（ＳＯ２ＣＦ３）２を含むＰＣとなるようにＮａＮ（ＳＯ２ＣＦ３）２（ＮａＴＦＳＩ）（キシダ化学株式会社製）を加えた以外は、実施例１と同様の操作で、非水電解液ＥＬ６（１Ｌ中に２．０モルのＮａＮ（ＳＯ２ＣＦ３）２を含むＰＣ）を調整した。非水電解液ＥＬ６に対するＰＣの割合は、６８体積％である。非水電解液ＥＬ６の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされ、ナトリウム塩が２５℃での飽和溶解度を超えて含まれていることを確認した。電解液に非水電解液ＥＬ６を用いた以外は、実施例１と同様の操作でナトリウム二次電池Ｂ６を作製した。 <Example 6> (Production of Sodium Secondary Battery B 6)
A PC containing 1.0 mol of NaN (SO 2 CF 3 ) 2 in 1 L (manufactured by Kishida Chemical Co., Ltd.) becomes a PC containing 2.0 mol of NaN (SO 2 CF 3 ) 2 in 1 L. The non-aqueous electrolyte EL 6 (2.0 mol of NaN in 1 L) was prepared in the same manner as in Example 1 except that NaN (SO 2 CF 3 ) 2 (NaTFSI) (manufactured by Kishida Chemical Co., Ltd.) was added. (PC containing (SO 2 CF 3 ) 2 ) was adjusted. The ratio of PC to non-aqueous electrolyte EL 6 is 68% by volume. As a result of measuring the particle size distribution of the non-aqueous electrolyte EL 6 , it was confirmed that particles were counted in a region of 10 nm to 200 nm, and that the sodium salt exceeded the saturation solubility at 25 ° C. A sodium secondary battery B 6 was produced in the same manner as in Example 1 except that the non-aqueous electrolyte EL 6 was used as the electrolyte.
　＜実施例７＞（ナトリウム二次電池Ｂ７の製造）
　１Ｌ中に１．０モルのＮａＰＦ６を含むＰＣ（キシダ化学株式会社製）と、ＦＥＣとを９８：２（体積比）の割合で混合し、さらに１Ｌ中に０．３モルのＮａＴＦＳＩを含むＰＣとなるようにＮａＴＦＳＩ（キシダ化学株式会社製）を加えた以外は、実施例１と同様の操作で、非水電解液ＥＬ７（１Ｌ中に１．０モルのＮａＰＦ６および０．３モルのＮａＴＦＳＩを含むＰＣ／ＦＥＣ）を調整した。非水電解液ＥＬ７に対するＰＣとＦＥＣの割合は、８９体積％である。非水電解液ＥＬ７の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされ、ナトリウム塩が２５℃での飽和溶解度を超えて含まれていることを確認した。電解液に非水電解液ＥＬ７を用いた以外は、実施例１と同様の操作でナトリウム二次電池Ｂ７を作製した。 <Example 7> (Production of Sodium Secondary Battery B 7)
PC (made by Kishida Chemical Co., Ltd.) containing 1.0 mol of NaPF 6 in 1 L and FEC are mixed at a ratio of 98: 2 (volume ratio), and further 0.3 mol of NaTFSI is contained in 1 L. The non-aqueous electrolyte EL 7 (1.0 mol of NaPF 6 and 0.3 mol in 1 L) was prepared in the same manner as in Example 1 except that NaTFSI (manufactured by Kishida Chemical Co., Ltd.) was added so as to be PC. PC / FEC containing NaTFSI). The ratio of PC and FEC to non-aqueous electrolyte EL 7 is 89% by volume. As a result of measuring the particle size distribution of the non-aqueous electrolyte EL 7 , it was confirmed that particles were counted in a region of 10 nm or more and 200 nm or less and that the sodium salt was contained exceeding the saturation solubility at 25 ° C. Except for using the non-aqueous electrolyte EL 7 in the electrolytic solution, to prepare a sodium secondary battery B 7 in the same manner as in Example 1.
　＜実施例８＞（ナトリウム二次電池Ｂ８の製造）
　１Ｌ中に１．０モルのＮａＰＦ６を含むＰＣ（キシダ化学株式会社製）に、１Ｌ中に１．０モルのＮａＴＦＳＩを含むＰＣとなるようにＮａＴＦＳＩを加えた以外は、実施例１と同様の操作で、非水電解液ＥＬ８（１Ｌ中に１．０モルのＮａＰＦ６および１．０モルのＮａＴＦＳＩを含むＰＣ）を調整した。非水電解液ＥＬ８に対するＰＣの割合は、８０体積％である。非水電解液ＥＬ８の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされ、ナトリウム塩が２５℃での飽和溶解度を超えて含まれていることを確認した。電解液に非水電解液ＥＬ８を用いた以外は、実施例１と同様の操作でナトリウム二次電池Ｂ８を作製した。 <Example 8> (Production of Sodium Secondary Battery B 8)
Example 1 except that NaTFSI was added to a PC containing 1.0 mol of NaPF 6 in 1 L so as to be a PC containing 1.0 mol of NaTFSI in 1 L. The non-aqueous electrolyte EL 8 (PC containing 1.0 mol of NaPF 6 and 1.0 mol of NaTFSI in 1 L) was prepared by the above procedure. Percentage of PC relative to the non-aqueous electrolyte EL 8 is 80% by volume. As a result of measuring the particle size distribution of the non-aqueous electrolyte EL 8 , it was confirmed that the particles were counted in the region of 10 nm to 200 nm, and the sodium salt was included exceeding the saturation solubility at 25 ° C. Except for using the non-aqueous electrolyte EL 8 in the electrolytic solution, to prepare a sodium secondary battery B 8 in the same manner as in Example 1.
　＜比較例１＞（ナトリウム二次電池ＢＨ１の製造）
　１Ｌ中に１．０モルのＮａＰＦ６を含むＰＣ（キシダ化学株式会社製）と、ＰＣと、ＦＥＣを４９：４９：２（体積比）の割合とした以外は、実施例１と同様の操作で、非水電解液ＥＨ１（１Ｌ中に０．５モルのＮａＰＦ６を含むＰＣ／ＦＥＣ）を調整した。非水電解液ＥＨ１に対するＰＣとＦＥＣの割合は、９７体積％である。非水電解液ＥＨ１の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされず、ナトリウム塩は２５℃での飽和溶解度以下であった。電解液に非水電解液ＥＨ１を用いた以外は、実施例１と同様の操作でナトリウム二次電池ＢＨ１を作製した。 <Comparative example 1> (Manufacture of sodium secondary battery BH 1 )
The same operation as in Example 1 except that PC containing 1.0 mol of NaPF 6 in 1 L (Kishida Chemical Co., Ltd.), PC, and FEC were in a ratio of 49: 49: 2 (volume ratio). The non-aqueous electrolyte EH 1 (PC / FEC containing 0.5 mol of NaPF 6 in 1 L) was prepared. The ratio of PC and FEC to the non-aqueous electrolyte EH 1 is 97% by volume. As a result of measuring the particle size distribution of the non-aqueous electrolyte EH 1, no particles were counted in the region of 10 nm or more and 200 nm or less, and the sodium salt was below the saturation solubility at 25 ° C. A sodium secondary battery BH 1 was produced in the same manner as in Example 1 except that the non-aqueous electrolyte EH 1 was used as the electrolyte.
　＜比較例２＞（ナトリウム二次電池Ｍ２の製造）
　１Ｌ中に１．０モルのＮａＰＦ６を含むＰＣと、ＰＣと、ＦＥＣとを７８：２０：２（体積比）の割合とした以外は、実施例１と同様の操作で、非水電解液ＥＨ２（１Ｌ中に０．８モルのＮａＰＦ６を含むＰＣ／ＦＥＣ）を調整した。電解液に非水電解液ＥＨ２を用いた以外は、実施例１と同様の操作でナトリウム二次電池ＢＨ２を作製した。非水電解液ＥＨ２に対するＰＣとＦＥＣの割合は、９４体積％である。非水電解液ＥＨ２の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされず、ナトリウム塩は２５℃での飽和溶解度以下であった。 <Comparative Example 2> (Production of Sodium Secondary Battery M 2)
A nonaqueous electrolyte solution was obtained in the same manner as in Example 1 except that PC containing 1.0 mol of NaPF 6 in 1 L, PC, and FEC were in a ratio of 78: 20: 2 (volume ratio). EH 2 (PC / FEC with 0.8 mol NaPF 6 in 1 L) was prepared. A sodium secondary battery BH 2 was produced in the same manner as in Example 1 except that the non-aqueous electrolyte EH 2 was used as the electrolyte. The ratio of PC and FEC to the non-aqueous electrolyte EH 2 is 94% by volume. Nonaqueous electrolyte EH 2 particle size distribution measurement the result of, not counted particles to 200nm following areas above 10 nm, the sodium salt was less than the saturation solubility at 25 ° C..
　＜比較例３＞（ナトリウム二次電池ＢＨ３の製造）
　１Ｌ中に１．０モルのＮａＴＦＳＩを含むＰＣを２５ｍＬとなるようにスクリュー管（アズワン製、型番Ｎｏ．７）に取り、８０℃に加熱した状態で、全長２０ｍｍのポリテトラフルオロエチレン回転子を用い２５０ｒｐｍで、アルゴンガス雰囲気下で６時間攪拌し、非水電解液ＥＨ３を調整した。電解液に非水電解液ＥＨ３を用いた以外は、実施例１と同様の操作でナトリウム二次電池ＢＨ３を作製した。非水電解液ＥＨ３の粒度分布測定を行った結果、１０ｎｍ以上２００ｎｍ以下の領域に粒子がカウントされず、ナトリウム塩は２５℃での飽和溶解度以下であった。 <Comparative Example 3> (Production of Sodium Secondary Battery BH 3)
PC containing 1.0 mol of NaTFSI in 1 L is taken into a screw tube (manufactured by ASONE, model No. 7) to 25 mL and heated to 80 ° C., and a polytetrafluoroethylene rotor having a total length of 20 mm is in using 250 rpm, and stirred for 6 hours under argon gas atmosphere, to prepare a non-aqueous electrolyte EH 3. A sodium secondary battery BH 3 was produced in the same manner as in Example 1 except that the non-aqueous electrolyte EH 3 was used as the electrolyte. As a result of measuring the particle size distribution of the non-aqueous electrolyte EH 3 , particles were not counted in the region of 10 nm or more and 200 nm or less, and the sodium salt was less than the saturation solubility at 25 ° C.
　＜充放電試験＞
　充放電試験の前に、ナトリウム二次電池Ｂ１~Ｂ８、ＢＨ１~~ＢＨ３の作動を安定化させる処置（安定化処置）を行った後、出力試験および充放電サイクル試験を行った。
　＜安定化処置＞
　レストポテンシャルから３．２Ｖに達するまで、０．０５Ｃレート（２０時間で完全充電する速度）でＣＣ（コンスタントカレント）充電を行った後、０．１Ｃレート（１０時間で完全充電する速度）で２．０Ｖに達するまでＣＣ放電する通電処置を１サイクル行った。さらに、３．８Ｖに達するまで０．０５ＣレートでＣＣ充電を行った後、０．１Ｃレートで２．０Ｖに達するまでＣＣ放電する通電処置を１サイクル行った。続いて、４．０Ｖに達するまで０．０５ＣレートでＣＣ−ＣＶ（コンスタントボルテージ）充電（０．００５Ｃ電流値到達で充電終了）を行った後、０．１Ｃレートで２．０Ｖに達するまでＣＣ放電する通電処置を１サイクル行った。加えて、４．０Ｖに達するまで０．１ＣレートでＣＣ−ＣＶ充電（０．０２Ｃ電流値到達で充電終了）を行った後、０．２Ｃレートで２．０Ｖに達するまでＣＣ放電する通電処置を３サイクル行った。
　＜出力試験＞
　上記安定化処置の後、以下の条件で出力試験を行った。４．０Ｖに達するまで０．２ＣレートでＣＣ−ＣＶ充電（０．０２Ｃ電流値到達で充電終了）を行った後、０．２Ｃレートで２．０Ｖに達するまでＣＣ放電する充放電試験を行った。その後、充電条件は上記条件と同様とし、放電電流を０．５、１、２、５、１０Ｃレートとした出力試験を行った。表１には、０．２Ｃ放電容量に対する５Ｃ放電容量の比（５Ｃ放電容量／０．２Ｃ放電容量×１００（％））を示す。
　＜充放電サイクル試験＞
　上記出力試験後、以下の条件で充放電サイクル試験を行った。４．０Ｖに達するまで０．２ＣレートでＣＣ−ＣＶ充電（０．０２Ｃ電流値到達で充電終了）を行った後、０．２Ｃレートで２．０Ｖに達するまでＣＣ放電する充放電試験を行った。その後、４．０Ｖに達するまで１ＣレートでＣＣ充電を行った後、０．５Ｃレートで２．０Ｖに達するまでＣＣ放電する充放電試験を４９サイクル行った。最後に、４．０Ｖに達するまで０．２ＣレートでＣＣ−ＣＶ充電（０．０２Ｃ電流値到達で充電終了）を行った後、０．２Ｃレートで２．０Ｖに達するまでＣＣ放電する充放電試験を行った。表１には、充放電サイクル試験前後での放電容量維持率（サイク示す。 <Charge / discharge test>
Prior to the charge / discharge test, the sodium secondary batteries B 1 to B 8 and BH 1 to BH 3 were stabilized (stabilized), and then the output test and the charge / discharge cycle test were performed. .
<Stabilization treatment>
CC (Constant Current) charge at 0.05C rate (speed to fully charge in 20 hours) until it reaches 3.2V from the rest potential, then 2 at 0.1C rate (speed to fully charge in 10 hours) 1 cycle of energization treatment for CC discharge until reaching 0 V was performed. Furthermore, CC charging was performed at a 0.05 C rate until reaching 3.8 V, and then a current-carrying treatment for performing CC discharging until reaching 2.0 V at a 0.1 C rate was performed for one cycle. Subsequently, after performing CC-CV (constant voltage) charging at 0.05C rate until reaching 4.0V (the charge is terminated when the current value of 0.005C is reached), CC is charged until reaching 2.0V at 0.1C rate. One cycle of the energization treatment for discharging was performed. In addition, after conducting CC-CV charging at 0.1C rate until reaching 4.0V (charging completed when reaching 0.02C current value), CC discharge until reaching 2.0V at 0.2C rate For 3 cycles.
<Output test>
After the stabilization treatment, an output test was performed under the following conditions. After performing CC-CV charge at a 0.2C rate until reaching 4.0V (charging is completed when the current value reaches 0.02C), a charge / discharge test is performed to perform CC discharge until reaching 2.0V at a 0.2C rate. It was. Thereafter, an output test was performed under the same charging conditions as those described above, with discharge currents of 0.5, 1, 2, 5, 10C. Table 1 shows a ratio of 5C discharge capacity to 0.2C discharge capacity (5C discharge capacity / 0.2C discharge capacity × 100 (%)).
<Charge / discharge cycle test>
After the output test, a charge / discharge cycle test was performed under the following conditions. After performing CC-CV charge at a 0.2C rate until reaching 4.0V (charging is completed when the current value reaches 0.02C), a charge / discharge test is performed to perform CC discharge until reaching 2.0V at a 0.2C rate. It was. Then, after performing CC charge at 1 C rate until reaching 4.0 V, 49 cycles of charge and discharge tests were performed for CC discharge until reaching 2.0 V at 0.5 C rate. Finally, after performing CC-CV charge at 0.2C rate until it reaches 4.0V (charge end when 0.02C current value is reached), CC charge / discharge until 2.0V is reached at 0.2C rate A test was conducted. Table 1 shows the discharge capacity retention rate before and after the charge / discharge cycle test (cycled).
Figure JPOXMLDOC01-appb-T000001
 　比較例３においては、安定化処置の時点で、不可逆な反応が進行し、充放電効率、放電容量の低下が顕著であったため、出力特性試験、サイクル特性試験に至らなかった。
Figure JPOXMLDOC01-appb-T000001
 In Comparative Example 3, an irreversible reaction progressed at the time of the stabilization treatment, and the decrease in charge / discharge efficiency and discharge capacity was remarkable. Therefore, the output characteristic test and the cycle characteristic test were not achieved.
　表１より、本発明の有用性が確かめられた。 From Table 1, the usefulness of the present invention was confirmed.
　本発明によれば、比較的速い速度、すなわち、比較的大きな電流値（１Ｃレート）で充電した際の充放電サイクル特性に優れたナトリウム二次電池を提供することができる。しかも、出力特性にも優れたナトリウム二次電池を提供することができる。 According to the present invention, it is possible to provide a sodium secondary battery excellent in charge / discharge cycle characteristics when charged at a relatively high speed, that is, at a relatively large current value (1C rate). In addition, a sodium secondary battery excellent in output characteristics can be provided.

Claims (4)

  1. 　ナトリウムイオンをドープかつ脱ドープできる正極活物質を有する正極と、ナトリウムイオンをドープかつ脱ドープできる負極活物質を有する負極と、非水溶媒と、該非水溶媒への飽和溶解度を超えるナトリウム塩とからなる非水電解液を有するナトリウム二次電池。 From a positive electrode having a positive electrode active material that can be doped and dedoped with sodium ions, a negative electrode having a negative electrode active material that can be doped and dedoped with sodium ions, a non-aqueous solvent, and a sodium salt that exceeds the saturation solubility in the non-aqueous solvent A sodium secondary battery having a non-aqueous electrolyte.
  2. 　前記ナトリウム塩が、ＮａＰＦ６、ＮａＢＦ４、ＮａＣｌＯ４、ＮａＮ（ＳＯ２ＣＦ３）２、ＮａＮ（ＳＯ２Ｃ２Ｆ５）２、ＮａＣＦ３ＳＯ３、ＮａＡｓＦ６、ＮａＳｂＦ６、ＮａＢＣ４Ｏ８、低級脂肪族カルボン酸ナトリウム塩、ＮａＡｌＣｌ４、ＮａＰＯ２Ｆ２、Ｎａ２ＰＯ３Ｆからなる群から選ばれる少なくとも１種の塩である請求項１記載のナトリウム二次電池。 The sodium salt is NaPF 6 , NaBF 4 , NaClO 4 , NaN (SO 2 CF 3 ) 2 , NaN (SO 2 C 2 F 5 ) 2 , NaCF 3 SO 3 , NaAsF 6 , NaSbF 6 , NaBC 4 O 8 , 2. The sodium secondary battery according to claim 1, wherein the sodium secondary battery is at least one salt selected from the group consisting of lower aliphatic carboxylic acid sodium salt, NaAlCl 4 , NaPO 2 F 2 , and Na 2 PO 3 F.
  3. 　前記非水電解液が、前記非水電解液１Ｌに対して、前記ナトリウム塩を、１．０モル以上３．０モル以下含んでいる非水電解液である請求項１または２に記載のナトリウム二次電池。 The sodium according to claim 1 or 2, wherein the non-aqueous electrolyte is a non-aqueous electrolyte containing 1.0 to 3.0 mol of the sodium salt with respect to 1 L of the non-aqueous electrolyte. Secondary battery.
  4. 　前記非水電解液が、引火点が７０℃以上の非水溶媒を、前記非水電解液に対して２５体積％以上含む非水電解液である請求項１から３のいずれかに記載のナトリウム二次電池。 4. The sodium according to claim 1, wherein the non-aqueous electrolyte is a non-aqueous electrolyte containing a non-aqueous solvent having a flash point of 70 ° C. or higher with respect to the non-aqueous electrolyte by 25 vol% or more. Secondary battery.
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WO2017149204A3 (en) * 2016-03-04 2017-12-21 Broadbit Batteries Oy Rechargeable sodium cells for high energy density battery use
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WO2016183638A1 (en) * 2015-05-20 2016-11-24 Deakin University Electrochemical cell
US11961963B2 (en) 2015-05-20 2024-04-16 Deakin University Electrochemical cell
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JP7483375B2 (en) 2017-03-17 2024-05-15 ブロードビット バッテリーズ オーイー Electrolytes for supercapacitors and high power batteries

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