WO2014083834A1 - Non-aqueous electrolyte secondary battery - Google Patents

Non-aqueous electrolyte secondary battery Download PDF

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Publication number
WO2014083834A1
WO2014083834A1 PCT/JP2013/006914 JP2013006914W WO2014083834A1 WO 2014083834 A1 WO2014083834 A1 WO 2014083834A1 JP 2013006914 W JP2013006914 W JP 2013006914W WO 2014083834 A1 WO2014083834 A1 WO 2014083834A1
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lithium
transition metal
secondary battery
metal oxide
electrolyte secondary
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PCT/JP2013/006914
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French (fr)
Japanese (ja)
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元治 斉藤
竹内　崇
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三洋電機株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—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
    • H01M10/0569—Liquid materials characterised by the solvents
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G51/00—Compounds of cobalt
    • C01G51/40—Cobaltates
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G51/00—Compounds of cobalt
    • C01G51/40—Cobaltates
    • C01G51/42—Cobaltates containing alkali metals, e.g. LiCoO2
    • C01G51/44—Cobaltates containing alkali metals, e.g. LiCoO2 containing manganese
    • C01G51/50—Cobaltates containing alkali metals, e.g. LiCoO2 containing manganese of the type [MnO2]n-, e.g. Li(CoxMn1-x)O2, Li(MyCoxMn1-x-y)O2
    • 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
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/76—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by a space-group or by other symmetry indications
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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 non-aqueous electrolyte battery.
  • Non-Patent Document 1 As one of the next generation high-capacity positive electrode active materials, lithium-containing oxides produced by ion-exchange of sodium-containing oxides are currently being studied (see Non-Patent Document 1).
  • LiCoO 2 having a crystal structure belonging to R-3m that is currently in practical use is charged to about 50% of lithium in LiCoO 2 by charging until the positive electrode potential exceeds 4.6 V (vs. Li / Li + ). It is known that the crystal structure collapses and the capacity retention rate decreases when the above is extracted, and therefore, when the battery is charged to a high potential of 4.8 V (lithium reference), the capacity maintenance is extremely deteriorated and the capacity maintenance rate is deteriorated. Yes.
  • LiCoO 2 having a crystal structure belonging to space group P6 3 mc which is a kind of lithium-containing oxide produced by ion-exchange of sodium-containing oxide, has a positive electrode potential of 4.6 V (vs. Li / Li + ), The crystal structure is maintained even when about 80% of lithium in LiCoO 2 is extracted.
  • Patent Document 1 it is difficult to produce LiCoO 2 having a crystal structure belonging to the space group P6 3 mc. This LiCoO 2 is obtained by preparing Na 0.7 CoO 2 having a P2 structure and ion-exchanging sodium with lithium.
  • an object of the present invention is to provide a non-aqueous electrolyte battery that can extract a large amount of lithium (high capacity) from the structure despite the fact that it includes the R-3m structure and can further improve the capacity retention rate. is there.
  • the nonaqueous electrolyte battery of the present invention is a nonaqueous electrolyte battery comprising a positive electrode including a positive electrode active material, a negative electrode, and a nonaqueous electrolyte, wherein the positive electrode active material has a crystal structure belonging to the space group P6 3 mc.
  • a lithium-containing transition metal oxide and a lithium-containing transition metal oxide having a crystal structure belonging to space group R-3m, and the nonaqueous electrolyte contains a fluorinated cyclic carbonate and a fluorinated chain ester It is characterized by.
  • the battery cycle is improved while increasing the capacity.
  • a nonaqueous electrolyte secondary battery which is an example of an embodiment of the present invention includes a positive electrode including a positive electrode active material, a negative electrode, and a nonaqueous electrolyte including a nonaqueous solvent.
  • a separator between the positive electrode and the negative electrode.
  • the nonaqueous electrolyte secondary battery has, for example, a structure in which an electrode body in which a positive electrode and a negative electrode are wound via a separator and a nonaqueous electrolyte are accommodated in an exterior body.
  • the positive electrode includes, for example, a positive electrode current collector such as a metal foil and a positive electrode active material layer formed on the positive electrode current collector.
  • a positive electrode current collector such as a metal foil and a positive electrode active material layer formed on the positive electrode current collector.
  • the positive electrode active material layer preferably includes a conductive agent and a binder in addition to the positive electrode active material.
  • the positive electrode active material includes both a lithium-containing transition metal oxide having a crystal structure belonging to space group P6 3 mc and a lithium-containing transition metal oxide having a crystal structure belonging to space group R-3m.
  • the peak intensity (Ir) of the index 104 considered to be a peak derived from the positive electrode active material belonging to the space group R-3m and the index 103 considered to be a peak derived from the positive electrode active material belonging to the space group P6 3 mc
  • 0 ⁇ Ia ⁇ 7.00, 0 ⁇ Ib ⁇ 3 0.00 is preferably satisfied.
  • a positive electrode active material including both a lithium-containing transition metal oxide having a crystal structure belonging to space group P6 3 mc and a lithium-containing transition metal oxide having a crystal structure belonging to space group R-3m is Li x1 Na y1 Co ⁇ .
  • ⁇ is less than the above range, the average discharge potential decreases.
  • ⁇ is larger than the above range, the crystal structure tends to be broken when charged until the positive electrode potential reaches 4.6 V (vs. Li / Li + ) or higher. It is more preferable that ⁇ is in the range of 0.95 ⁇ ⁇ 1.0 because the energy density is further increased. Further, when ⁇ is larger than the above range, the average discharge potential is lowered.
  • At least one element selected from magnesium, nickel, zirconium, molybdenum, tungsten, aluminum, chromium, vanadium, cerium, titanium, iron, potassium, gallium, and indium may be added to the lithium-containing oxide.
  • the addition amount of these elements is preferably 10 mol% or less with respect to the total mol amount of cobalt and manganese.
  • the inorganic compound include an oxide, a phosphoric acid compound, and a boric acid compound.
  • An example of the oxide is Al 2 O 3 .
  • Lithium-containing oxides can be made by ion exchange of sodium, sodium-containing oxide sodium containing lithium, cobalt, and manganese not exceeding the molar amount of sodium into lithium.
  • Na y2 Co ⁇ M ⁇ O ⁇ (0.66 ⁇ y2 ⁇ 1.0, 0.95 ⁇ ⁇ 1, 0 ⁇ ⁇ 0.05, 1.9 ⁇ ⁇ ⁇ 2.1, where M is Co It can be produced by ion-exchanging a part of sodium contained in the sodium-containing oxide represented by (a metal element other than).
  • Examples of the method for ion-exchanging sodium to lithium include at least one selected from the group consisting of lithium nitrate, lithium sulfate, lithium chloride, lithium carbonate, lithium hydroxide, lithium iodide, lithium bromide, and lithium chloride.
  • a method of adding a molten salt bed of lithium salt to a sodium-containing transition metal oxide is mentioned.
  • a method of immersing a sodium-containing transition metal oxide in a solution containing at least one lithium salt can be given.
  • the remaining sodium forms a sodium oxide before ion exchange, an oxide in which lithium and sodium are present in one structure.
  • sodium lithium oxide belonging to the space group P-6m2 is known.
  • Battery characteristics can be improved because a certain amount of sodium oxide remains in lithium oxide.
  • lithium oxide after ion exchange examples include an O2 structure of a space group P6 3 mc, an O3 structure of R-3m, an O6 structure, and a T2 structure of a space group Cmca.
  • the positive electrode active material may contain various oxides belonging to various space groups in the form of a mixture or a solid solution, but 51% or more of the composition should be a lithium oxide belonging to the space group P6 3 mc. Is desirable, and more desirably 70% or more.
  • the conductive agent is used to increase the electrical conductivity of the positive electrode active material layer.
  • the conductive agent include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. These may be used alone or in combination of two or more.
  • the above binder is used for maintaining a good contact state between the positive electrode active material and the conductive agent and enhancing the binding property of the positive electrode active material and the like to the surface of the positive electrode current collector.
  • the binder for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), or a modified product thereof is used.
  • the binder may be used in combination with a thickener such as carboxymethyl cellulose (CMC) or polyethylene oxide (PEO).
  • the positive electrode having the above structure can be charged until the positive electrode potential exceeds 4.6 V (vs. Li / Li + ).
  • the upper limit of the charge potential of the positive electrode is not particularly defined, but if it is too high, decomposition of the nonaqueous electrolyte is caused, and therefore, it is preferably 5.0 V (vs. Li / Li + ) or less.
  • the negative electrode includes, for example, a negative electrode current collector such as a metal foil, and a negative electrode active material layer formed on the negative electrode current collector.
  • a negative electrode current collector such as a metal foil
  • a negative electrode active material layer formed on the negative electrode current collector.
  • a metal foil that is stable in the potential range of the negative electrode such as copper a film in which a metal that is stable in the potential range of the negative electrode such as copper is arranged on the surface layer, or the like can be used.
  • the negative electrode active material layer preferably contains a binder in addition to the negative electrode active material capable of inserting and extracting lithium ions.
  • PTFE styrene-butadiene copolymer
  • the binder may be used in combination with a thickener such as CMC.
  • Examples of the negative electrode active material include natural graphite, artificial graphite, lithium, silicon, carbon, tin, germanium, aluminum, lead, indium, gallium, lithium alloy, carbon and silicon in which lithium is previously occluded, and alloys and mixtures thereof. Etc. can be used.
  • the non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent.
  • the nonaqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolyte solution), and may be a solid electrolyte using a gel polymer or the like.
  • the non-aqueous solvent contains a fluorinated cyclic carbonate and a fluorinated chain ester. By using such a solvent, elution of the positive electrode can be suppressed.
  • the fluorinated cyclic carbonate is preferably a fluorinated cyclic carbonate in which a fluorine atom is directly bonded to a carbonate ring. Examples thereof include 4-fluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,4-difluoro. Examples thereof include ethylene carbonate, 4,4,5-trifluoroethylene carbonate, and 4,4,5,5-tetrafluoroethylene carbonate. Of these, 4-fluoroethylene carbonate and 4,5-difluoroethylene carbonate are more preferable because of their relatively low viscosity and high formability of a protective film on the negative electrode.
  • the content of the fluorinated cyclic carbonate is preferably 5 to 50% by volume, more preferably 10 to 40% by volume, based on the total amount of the nonaqueous electrolyte.
  • the fluorinated chain ester preferably contains at least one of a fluorinated chain carboxylate ester or a fluorinated chain carbonate ester.
  • fluorinated chain carboxylic acid ester examples include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, or ethyl propionate partially or wholly fluorinated. Of these, methyl 3,3,3-trifluoropropionate is preferred because of its relatively low viscosity.
  • fluorinated chain carbonate examples include those in which part or all of hydrogen in dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate is fluorinated. Of these, methyl 2,2,2-trifluoroethyl carbonate is preferred.
  • the content of the fluorinated chain ester is preferably 30 to 90% by volume, more preferably 50 to 90% by volume, based on the total amount of the nonaqueous electrolyte.
  • non-aqueous electrolyte in addition to the fluorinated cyclic carbonate ester and the fluorinated chain ester, a non-aqueous electrolyte conventionally used in non-aqueous electrolyte batteries can be used together.
  • cyclic carbonates include ethylene carbonate and propylene carbonate.
  • chain carbonate examples include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.
  • ethers include 1,2-dimethoxyethane.
  • the non-aqueous electrolyte includes an alkali metal salt conventionally used in non-aqueous electrolyte batteries. Examples thereof include LiPF 6 and LiBF 4 .
  • battery constituent members used in conventional nonaqueous electrolyte batteries can be used as necessary.
  • separator a porous sheet having ion permeability and insulating properties is used.
  • the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric.
  • material of the separator polyolefin such as polyethylene and polypropylene is suitable.
  • Example 1 NaNO 3 , Co 3 O 4 , and TiO 2 (anatase type) were mixed so as to meet the stoichiometric ratio of Na 81/81 Co 79/81 Ti 1/81 O 2 . Then, the sodium containing transition metal oxide was obtained by hold
  • the obtained lithium-containing transition metal oxide was analyzed by powder X-ray diffraction, and as a result, it was found that it had a crystal structure belonging to the space group P6 3 mc and the space group R-3m (see FIG. 1).
  • the composition ratio of the obtained lithium-containing transition metal oxide was Li 0.905 Na 0.066 Co 0.988 Ti 0.012 . .
  • the obtained lithium-containing transition metal oxide was used as a positive electrode active material, and the positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed so that the mass ratio was 80:10:10. . Thereafter, N-methyl-2-pyrrolidone was added to the mixture to prepare a positive electrode mixture slurry. The obtained positive electrode mixture slurry was applied to a current collector made of an aluminum foil, and vacuum-dried at 110 ° C. to produce a working electrode 1.
  • a test cell shown in FIG. 2 was prepared using the working electrode 1, the counter electrode 2, the reference electrode 3, the separator 4, the nonaqueous electrolyte 5, and the container 6 under dry air having a dew point of ⁇ 50 ° C. or less. Note that lithium metal was used for the counter electrode 2 and the reference electrode 3. As the separator 4, a polyethylene separator was used.
  • the non-aqueous electrolyte 5 is a non-aqueous electrolyte in which 4-fluoroethylene carbonate (FEC) and methyl 3,3,3-trifluoropropionate (F-MP) are mixed so that the volume ratio is 2: 8.
  • FEC 4-fluoroethylene carbonate
  • F-MP methyl 3,3,3-trifluoropropionate
  • LiPF 6 dissolved at a concentration of 1.0 mol / L was used.
  • Electrode tabs 7 are attached to the working electrode 1, the counter electrode 2, and the reference electrode 3, respectively.
  • Example 2> Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 79/81 Co 79/81 Mn 1/81 Ti 1/81 O 2
  • a test cell was prepared in the same manner as in Example 1.
  • Example 3> Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 78/81 Co 78/81 Mn 2/81 Ti 1/81 O 2
  • Example 1 Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 78/81 Co 78/81 Mn 2/81 Ti 1/81 O 2
  • Example 1 Other than mixing NaNO 3
  • Example 4 Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 78/81 Co 78/81 Mn 1/81 Ti 2/81 O 2
  • a test cell was prepared in the same manner as in Example 1.
  • Example 5> Except that NaNO 3 , Co 3 O 4 , and TiO 2 (anatase type) were mixed in accordance with the stoichiometric ratio of Na 78/81 Co 78/81 Ti 3/81 O 2 , the same as in Example 1.
  • a test cell was prepared.
  • LiPF 6 was dissolved to a concentration of 1.0 mol / l in a non-aqueous electrolyte in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 2: 8.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • ⁇ Comparative Example 2> Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 79/81 Co 79/81 Mn 1/81 Ti 1/81 O 2 Produced a test cell in the same manner as in Comparative Example 1.
  • ⁇ Comparative Example 3> Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 78/81 Co 78/81 Mn 2/81 Ti 1/81 O 2 Produced a test cell in the same manner as in Comparative Example 1.
  • FIG. 1 shows LiCoO 2 (PDF # 75-0532) as an example of an XRD profile belonging to Examples 1 to 6, Comparative Examples 1 to 3, and space group R-3m.
  • the positive electrode active material having a positive electrode active material and the space group R-3m having a space group P6 3 mc are both present, since the structural change of the positive electrode active material having a space group R-3m is suppressed, Capacitance reduction due to structural changes accompanying cycles can be suppressed.
  • a positive electrode active material having a space group P6 3 mc and a positive electrode active material having a space group R-3m are produced by ion exchange of sodium oxide having a P2 structure (space group: P6 3 / mmc), and are subjected to XRD measurement. From this, it can be seen that the amount of the positive electrode active material having the space group R-3m is smaller than the amount of the positive electrode active material having the space group P6 3 mc.
  • 0 ⁇ Ia ⁇ 7.00 is preferable. More preferably, 0.07 ⁇ Ia ⁇ 7.00. Further, 0 ⁇ Ib ⁇ 3.00 is preferable. More preferably, 0.2 ⁇ Ib ⁇ 3.00.
  • Ia is larger than 7 and Ib is larger than 3, it is considered that structural deterioration is caused at a charging potential of 4.6 V (lithium reference) or higher.
  • the sealed battery according to the present invention is suitably used for electronic devices such as personal computers and mobile phones, and electric power sources such as electric vehicles and electric tools.

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Abstract

This non-aqueous electrolyte secondary battery is provided with a positive electrode including a positive electrode active material, a negative electrode, and a non-aqueous electrolyte, said positive electrode active material including both a lithium-containing transition metal oxide having a crystal structure belonging to a space group P63mc and a lithium-containing transition metal oxide having a crystal structure belonging to a space group R-3m, and said non-aqueous electrolyte including fluorinated cyclic carbonate esters and fluorinated chain esters.

Description

非水電解質二次電池Nonaqueous electrolyte secondary battery
　本願発明は、非水電解質電池に関するものである。 The present invention relates to a non-aqueous electrolyte battery.
　次世代の高容量正極活物質のひとつとして、ナトリウム含有酸化物をイオン交換して作製されるリチウム含有酸化物が現在研究されている（非特許文献１参照）。 As one of the next generation high-capacity positive electrode active materials, lithium-containing oxides produced by ion-exchange of sodium-containing oxides are currently being studied (see Non-Patent Document 1).
　現在実用化されているＲ－３ｍに属する結晶構造を有するＬｉＣｏＯ２は、正極電位が４．６Ｖ（ｖｓ. Ｌｉ／Ｌｉ＋）を超えるまで充電することにより、ＬｉＣｏＯ２中のリチウムを約５０％以上引き抜くと、結晶構造が崩れ、容量維持率が低下するため、４．８Ｖ（リチウム基準）という高い電位まで充電すると、極端に容量維持が悪化し、容量維持率が悪化することが知られている。(非特許文献２、３参照)
　一方、ナトリウム含有酸化物をイオン交換して作製されるリチウム含有酸化物の一種である空間群Ｐ６3ｍｃに属する結晶構造を有するＬｉＣｏＯ２は、正極電位が４．６Ｖ（ｖｓ. Ｌｉ／Ｌｉ＋）を超えるまで充電することにより、ＬｉＣｏＯ２中のリチウムを約８０％引き抜いても、結晶構造が維持される。(特許文献１参照)
　しかしながら、空間群Ｐ６3ｍｃに属する結晶構造を有するＬｉＣｏＯ２は作製することが困難である。このＬｉＣｏＯ２はＰ２構造のＮａ０．７ＣｏＯ２を作製し、ナトリウムをリチウムでイオン交換することによって得られるが、イオン交換する際の温度が１５０℃を超えるとＬｉＣｏＯ２の結晶構造が空間群Ｒ－３ｍに変化し、温度が低すぎるとイオン交換前の原料が残る。従って、７０％以上リチウムの脱離で容量維持率が極端に低下する空間群Ｒ－３ｍに由来の構造が生成を抑制することが必要であった。 LiCoO 2 having a crystal structure belonging to R-3m that is currently in practical use is charged to about 50% of lithium in LiCoO 2 by charging until the positive electrode potential exceeds 4.6 V (vs. Li / Li + ). It is known that the crystal structure collapses and the capacity retention rate decreases when the above is extracted, and therefore, when the battery is charged to a high potential of 4.8 V (lithium reference), the capacity maintenance is extremely deteriorated and the capacity maintenance rate is deteriorated. Yes. (See Non-Patent Documents 2 and 3)
On the other hand, LiCoO 2 having a crystal structure belonging to space group P6 3 mc, which is a kind of lithium-containing oxide produced by ion-exchange of sodium-containing oxide, has a positive electrode potential of 4.6 V (vs. Li / Li + ), The crystal structure is maintained even when about 80% of lithium in LiCoO 2 is extracted. (See Patent Document 1)
However, it is difficult to produce LiCoO 2 having a crystal structure belonging to the space group P6 3 mc. This LiCoO 2 is obtained by preparing Na 0.7 CoO 2 having a P2 structure and ion-exchanging sodium with lithium. When the temperature during ion exchange exceeds 150 ° C., the crystal structure of LiCoO 2 becomes the space group R If the temperature is too low, the raw material before ion exchange remains. Therefore, it was necessary to suppress the formation of a structure derived from the space group R-3m, in which the capacity retention rate is extremely reduced by desorption of lithium by 70% or more.
特開２０１１－２２８２７３JP2011-228273A
　すなわち、従来の空間群Ｐ６3ｍｃに属する結晶構造を有する正極活物質において、高容量かつ容量維持率の向上は困難であった。そこで、本願発明の目的は、Ｒ－３ｍ構造を含んでいるにも関わらず構造から多くのリチウムを引き抜け（高い容量）、さらに容量維持率が向上できうる非水電解質電池を提供することにある。 That is, in the positive electrode active material having a crystal structure belonging to the conventional space group P6 3 mc, it is difficult to improve the capacity and the capacity retention rate. Accordingly, an object of the present invention is to provide a non-aqueous electrolyte battery that can extract a large amount of lithium (high capacity) from the structure despite the fact that it includes the R-3m structure and can further improve the capacity retention rate. is there.
本願発明の非水電解質電池は、正極活物質を含む正極と、負極と、非水電解質とを備える非水電解質電池であって、正極活物質が、空間群Ｐ６3ｍｃに属する結晶構造を有するリチウム含有遷移金属酸化物と空間群Ｒ－３ｍに属する結晶構造を有するリチウム含有遷移金属酸化物を供に含み、非水電解質が、フッ素化環状炭酸エステルとフッ素化鎖状エステルとを含む、ことを特徴としている。 The nonaqueous electrolyte battery of the present invention is a nonaqueous electrolyte battery comprising a positive electrode including a positive electrode active material, a negative electrode, and a nonaqueous electrolyte, wherein the positive electrode active material has a crystal structure belonging to the space group P6 3 mc. A lithium-containing transition metal oxide and a lithium-containing transition metal oxide having a crystal structure belonging to space group R-3m, and the nonaqueous electrolyte contains a fluorinated cyclic carbonate and a fluorinated chain ester It is characterized by.
　本願発明によれば、容量を高めながら電池サイクルが向上する。 According to the present invention, the battery cycle is improved while increasing the capacity.
実施例１～５及び比較例１～３で作製した正極活物質の粉末Ｘ線回折パターンPowder X-ray diffraction patterns of positive electrode active materials prepared in Examples 1 to 5 and Comparative Examples 1 to 3 本願で使用した試験セルの模式図Schematic diagram of the test cell used in this application
　以下、本発明の実施形態を詳細に説明する。なお、本発明は、以下の実施形態に限定されるものではない。また、本発明の効果を奏する範囲を逸脱しない範囲で、適宜変更は可能である。さらに、他の実施形態との組み合わせも可能である。 Hereinafter, embodiments of the present invention will be described in detail. In addition, this invention is not limited to the following embodiment. Moreover, it can change suitably in the range which does not deviate from the range which has the effect of this invention. Furthermore, combinations with other embodiments are possible.
　本発明の実施形態の一例である非水電解質二次電池は、正極活物質を含む正極と、負極と、非水溶媒を含む非水電解質とを備える。また、正極と負極との間には、セパレータを設けることが好適である。非水電解質二次電池は、例えば、正極及び負極がセパレータを介して巻回されてなる電極体と、非水電解質とが外装体に収容された構造を有する。 A nonaqueous electrolyte secondary battery which is an example of an embodiment of the present invention includes a positive electrode including a positive electrode active material, a negative electrode, and a nonaqueous electrolyte including a nonaqueous solvent. In addition, it is preferable to provide a separator between the positive electrode and the negative electrode. The nonaqueous electrolyte secondary battery has, for example, a structure in which an electrode body in which a positive electrode and a negative electrode are wound via a separator and a nonaqueous electrolyte are accommodated in an exterior body.
　〔正極〕
　正極は、例えば、金属箔等の正極集電体と、正極集電体上に形成された正極活物質層とで構成される。正極集電体には、アルミニウムなどの正極の電位範囲で安定な金属の箔、アルミニウムなどの正極の電位範囲で安定な金属を表層に配置したフィルム等が用いられる。正極活物質層は、正極活物質の他に、導電剤及び結着剤を含むことが好適である。 [Positive electrode]
The positive electrode includes, for example, a positive electrode current collector such as a metal foil and a positive electrode active material layer formed on the positive electrode current collector. As the positive electrode current collector, a metal foil that is stable in the potential range of the positive electrode such as aluminum, a film in which a metal that is stable in the potential range of the positive electrode such as aluminum is disposed on the surface layer, or the like is used. The positive electrode active material layer preferably includes a conductive agent and a binder in addition to the positive electrode active material.
　上記正極活物質は、空間群Ｐ６3ｍｃに属する結晶構造を有するリチウム含有遷移金属酸化物と空間群Ｒ－３ｍに属する結晶構造を有するリチウム含有遷移金属酸化物とを共に含む。 The positive electrode active material includes both a lithium-containing transition metal oxide having a crystal structure belonging to space group P6 3 mc and a lithium-containing transition metal oxide having a crystal structure belonging to space group R-3m.
　なお、ＸＲＤ測定において、空間群Ｒ－３ｍに属する正極活物質由来のピークと考えられる指数１０４のピーク強度（Iｒ）と空間群Ｐ６3ｍｃに属する正極活物質由来のピークと考えられる指数１０３のピーク強度（Iｐ１）、および（１１０）のピーク強度（Iｐ２）よりＩa（＝Iｒ／Iｐ１）、Iｂ（＝Iｒ／Iｐ２）を見積もったとき、０＜Iａ≦７．００、０＜Iｂ≦３．００を満たすと好ましい。 In XRD measurement, the peak intensity (Ir) of the index 104 considered to be a peak derived from the positive electrode active material belonging to the space group R-3m and the index 103 considered to be a peak derived from the positive electrode active material belonging to the space group P6 3 mc When Ia (= Ir / Ip1) and Ib (= Ir / Ip2) are estimated from the peak intensity (Ip1) and the peak intensity (Ip2) of (110), 0 <Ia ≦ 7.00, 0 <Ib ≦ 3 0.00 is preferably satisfied.
　空間群Ｐ６3ｍｃに属する結晶構造を有するリチウム含有遷移金属酸化物と空間群Ｒ－３ｍに属する結晶構造を有するリチウム含有遷移金属酸化物とを共に含む正極活物質は、Ｌｉｘ１Ｎａｙ１ＣｏαＭβＯγ（０．８０＜ｘ１＜１.１、０＜ｙ１≦０．１０、０．９５＜α＜１、０＜β≦０．０５、１．９γ≦２．１、ＭはＣo以外の金属元素）で表されるリチウム含有遷移金属酸化物を使用することが好ましい。 A positive electrode active material including both a lithium-containing transition metal oxide having a crystal structure belonging to space group P6 3 mc and a lithium-containing transition metal oxide having a crystal structure belonging to space group R-3m is Li x1 Na y1 Co α. M β O γ (0.80 <x1 <1.1, 0 <y1 ≦ 0.10, 0.95 <α <1, 0 <β ≦ 0.05, 1.9γ ≦ 2.1, M is Co It is preferable to use a lithium-containing transition metal oxide represented by any other metal element.
　ｘ１が上記範囲より多いと遷移金属サイトにリチウムが入り、容量密度が減少する。 When x1 is larger than the above range, lithium enters the transition metal site and the capacity density decreases.
　ｙ１が上記範囲より多いと、ナトリウムが挿入又は脱離するときに結晶構造が崩れやすくなる。尚、ｙ１が上記範囲にある場合、ＸＲＤ測定でナトリウムを検出できない場合がある。 When y1 is more than the above range, the crystal structure is easily broken when sodium is inserted or desorbed. When y1 is in the above range, sodium may not be detected by XRD measurement.
　αが上記範囲より少ないと平均放電電位が低下する。また、αが上記範囲より多いと、正極電位を４．６Ｖ（vs. Ｌｉ／Ｌｉ＋）以上に達するまで充電したときに、結晶構造が崩れやすくなる。尚、αが０．９５＜α＜１．０の範囲であると、エネルギー密度がさらに高くなるためより好ましい。また、βが上記範囲より多くなると、平均放電電位が低下する。 If α is less than the above range, the average discharge potential decreases. On the other hand, if α is larger than the above range, the crystal structure tends to be broken when charged until the positive electrode potential reaches 4.6 V (vs. Li / Li + ) or higher. It is more preferable that α is in the range of 0.95 <α <1.0 because the energy density is further increased. Further, when β is larger than the above range, the average discharge potential is lowered.
　リチウム含有酸化物に、マグネシウム、ニッケル、ジルコニウム、モリブデン、タングステン、アルミニウム、クロム、バナジウム、セリウム、チタン、鉄、カリウム、ガリウム、インジウムから選ばれる元素のうち少なくとも一つの元素を添加してもよい。これら元素の添加量は、コバルトとマンガンの総ｍｏｌ量に対して１０ｍｏｌ％以下であることが好ましい。正極活物質の表面を無機化合物の微粒子で覆うことも可能である。無機化合物の例としては、酸化物、リン酸化合物、及びホウ酸化合物が挙げられる。また、酸化物の例としてはＡｌ２Ｏ３が挙げられる。 At least one element selected from magnesium, nickel, zirconium, molybdenum, tungsten, aluminum, chromium, vanadium, cerium, titanium, iron, potassium, gallium, and indium may be added to the lithium-containing oxide. The addition amount of these elements is preferably 10 mol% or less with respect to the total mol amount of cobalt and manganese. It is also possible to cover the surface of the positive electrode active material with fine particles of an inorganic compound. Examples of the inorganic compound include an oxide, a phosphoric acid compound, and a boric acid compound. An example of the oxide is Al 2 O 3 .
　リチウム含有酸化物は、ナトリウム、ナトリウムのモル量を超えないリチウム、コバルト、及びマンガンを含むナトリウム含有酸化物のナトリウムをリチウムにイオン交換することによって作製することができる。例えば、Ｎａｙ２ＣｏαＭβＯγ（０．６６＜ｙ２＜１．０、０．９５＜α＜１、０＜β≦０．０５、１．９≦γ≦２．１、ＭはＣｏ以外の金属元素）で表されるナトリウム含有酸化物に含まれるナトリウムの一部をリチウムでイオン交換することによって作製することができる。 Lithium-containing oxides can be made by ion exchange of sodium, sodium-containing oxide sodium containing lithium, cobalt, and manganese not exceeding the molar amount of sodium into lithium. For example, Na y2 Co α M β O γ (0.66 <y2 <1.0, 0.95 <α <1, 0 <β ≦ 0.05, 1.9 ≦ γ ≦ 2.1, where M is Co It can be produced by ion-exchanging a part of sodium contained in the sodium-containing oxide represented by (a metal element other than).
　ナトリウムをリチウムにイオン交換する方法としては、例えば、硝酸リチウム、硫酸リチウム、塩化リチウム、炭酸リチウム、水酸化リチウム、ヨウ化リチウム、臭化リチウム、及び塩化リチウムからなる群より選ばれた少なくとも一種のリチウム塩の溶融塩床をナトリウム含有遷移金属酸化物に加える方法が挙げられる。他にも、これら少なくとも一種のリチウム塩を含む溶液中にナトリウム含有遷移金属酸化物を浸漬する方法が挙げられる。 Examples of the method for ion-exchanging sodium to lithium include at least one selected from the group consisting of lithium nitrate, lithium sulfate, lithium chloride, lithium carbonate, lithium hydroxide, lithium iodide, lithium bromide, and lithium chloride. A method of adding a molten salt bed of lithium salt to a sodium-containing transition metal oxide is mentioned. In addition, a method of immersing a sodium-containing transition metal oxide in a solution containing at least one lithium salt can be given.
　このように作製したリチウム酸化物には、イオン交換が完全には進行しないため、ナトリウムが残存する。 In the lithium oxide thus prepared, sodium remains because ion exchange does not proceed completely.
　残存したナトリウムは、イオン交換前のナトリウム酸化物、リチウムとナトリウムが一つの構造中に存在する酸化物を形成する。例えば空間群Ｐ－６ｍ２に属するナトリウムリチウム酸化物などが知られている。 The remaining sodium forms a sodium oxide before ion exchange, an oxide in which lithium and sodium are present in one structure. For example, sodium lithium oxide belonging to the space group P-6m2 is known.
　リチウム酸化物中に一定量のナトリウム酸化物が残っていることで、電池特性の改善が図られる。 Battery characteristics can be improved because a certain amount of sodium oxide remains in lithium oxide.
　しかし、ｙ２が上記範囲より多い場合は水分を吸収し構造変化が起こる。 However, when y2 is larger than the above range, moisture is absorbed and structural change occurs.
　イオン交換後のリチウム酸化物として、例えば空間群Ｐ６3ｍｃのＯ２構造、Ｒ－３ｍのＯ３構造、Ｏ６構造、空間群ＣｍｃａのＴ２構造がある。 Examples of the lithium oxide after ion exchange include an O2 structure of a space group P6 3 mc, an O3 structure of R-3m, an O6 structure, and a T2 structure of a space group Cmca.
　正極活物質には、種々の空間群に属する各酸化物が混合物や固溶体の形で含まれていても構わないが、組成の５１％以上が空間群Ｐ６3ｍｃに属するリチウム酸化物であることが望ましく、さらに望ましくは７０％以上である。 The positive electrode active material may contain various oxides belonging to various space groups in the form of a mixture or a solid solution, but 51% or more of the composition should be a lithium oxide belonging to the space group P6 3 mc. Is desirable, and more desirably 70% or more.
　上記導電剤は、正極活物質層の電気伝導性を高めるために用いられる。導電剤には、カーボンブラック、アセチレンブラック、ケッチェンブラック、黒鉛等の炭素材料が挙げられる。これらを単独で用いてもよく、２種類以上を組み合わせて用いてもよい。 The conductive agent is used to increase the electrical conductivity of the positive electrode active material layer. Examples of the conductive agent include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. These may be used alone or in combination of two or more.
　上記結着剤は、正極活物質及び導電剤間の良好な接触状態を維持し、かつ正極集電体表面に対する正極活物質等の結着性を高めるために用いられる。結着剤には、例えば、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶｄＦ）、又はこれらの変性体等が用いられる。結着剤は、カルボキシメチルセルロース（ＣＭＣ）、ポリエチレンオキシド（ＰＥＯ）等の増粘剤と併用されてもよい。 The above binder is used for maintaining a good contact state between the positive electrode active material and the conductive agent and enhancing the binding property of the positive electrode active material and the like to the surface of the positive electrode current collector. As the binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), or a modified product thereof is used. The binder may be used in combination with a thickener such as carboxymethyl cellulose (CMC) or polyethylene oxide (PEO).
　上記構成を備えた正極は、正極電位が４．６Ｖ（vs. Ｌｉ／Ｌｉ＋）を超えるまで充電することができる。正極の充電電位の上限については特に定められるものではないが、高すぎると非水電解質の分解などを引き起こすため、５．０Ｖ（vs. Ｌｉ／Ｌｉ＋）以下が好ましい。 The positive electrode having the above structure can be charged until the positive electrode potential exceeds 4.6 V (vs. Li / Li + ). The upper limit of the charge potential of the positive electrode is not particularly defined, but if it is too high, decomposition of the nonaqueous electrolyte is caused, and therefore, it is preferably 5.0 V (vs. Li / Li + ) or less.
　尚、上記一般式で表されるリチウム含有遷移金属酸化物が４．６Ｖ（vs. Ｌｉ／Ｌｉ＋）を超えるまで充電されたとき、ｘ１の値は０＜ｘ１＜０.０１となっている。 When the lithium-containing transition metal oxide represented by the above general formula is charged to exceed 4.6 V (vs. Li / Li + ), the value of x1 is 0 <x1 <0.01. .
　〔負極〕
　負極は、例えば、金属箔等の負極集電体と、負極集電体上に形成された負極活物質層とを備える。負極集電体には、銅などの負極の電位範囲で安定な金属の箔、銅などの負極の電位範囲で安定な金属を表層に配置したフィルム等を用いることができる。負極活物質層は、リチウムイオンを吸蔵・脱離可能な負極活物質の他に、結着剤を含むことが好適である。結着剤としては、正極の場合と同様にＰＴＦＥ等を用いることもできるが、スチレン－ブタジエン共重合体（ＳＢＲ）又はこの変性体等を用いることが好ましい。結着剤は、ＣＭＣ等の増粘剤と併用されてもよい。 [Negative electrode]
The negative electrode includes, for example, a negative electrode current collector such as a metal foil, and a negative electrode active material layer formed on the negative electrode current collector. As the negative electrode current collector, a metal foil that is stable in the potential range of the negative electrode such as copper, a film in which a metal that is stable in the potential range of the negative electrode such as copper is arranged on the surface layer, or the like can be used. The negative electrode active material layer preferably contains a binder in addition to the negative electrode active material capable of inserting and extracting lithium ions. As the binder, PTFE or the like can be used as in the case of the positive electrode, but it is preferable to use a styrene-butadiene copolymer (SBR) or a modified product thereof. The binder may be used in combination with a thickener such as CMC.
　上記負極活物質には、天然黒鉛、人造黒鉛、リチウム、珪素、炭素、錫、ゲルマニウム、アルミニウム、鉛、インジウム、ガリウム、リチウム合金、予めリチウムを吸蔵させた炭素並びに珪素、及びこれらの合金並びに混合物等を用いることができる。 Examples of the negative electrode active material include natural graphite, artificial graphite, lithium, silicon, carbon, tin, germanium, aluminum, lead, indium, gallium, lithium alloy, carbon and silicon in which lithium is previously occluded, and alloys and mixtures thereof. Etc. can be used.
　〔非水電解質〕
　非水電解質は、非水溶媒と、非水溶媒に溶解した電解質塩とを含む。非水電解質は、液体電解質（非水電解液）に限定されず、ゲル状ポリマー等を用いた固体電解質であってもよい。 [Non-aqueous electrolyte]
The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The nonaqueous electrolyte is not limited to a liquid electrolyte (nonaqueous electrolyte solution), and may be a solid electrolyte using a gel polymer or the like.
　上記非水溶媒は、フッ素化環状炭酸エステルとフッ素化鎖状エステルとを含有する。このような溶媒を用いることによって、正極の溶出を抑制することが出来る。

　フッ素化環状炭酸エステルは、カーボネート環にフッ素原子が直接結合したフッ素化環状炭酸エステルであることが好ましく、その例として、４－フルオロエチレンカーボネート、４，５－ジフルオロエチレンカーボネート、４，４－ジフルオロエチレンカーボネート、４，４，５－トリフルオロエチレンカーボネート、４，４，５，５－テトラフルオロエチレンカーボネートが挙げられる。なかでも、４－フルオロエチレンカーボネート、４，５－ジフルオロエチレンカーボネートが、比較的粘度が低く、負極での保護被膜の形成性が高いためより好ましい。 The non-aqueous solvent contains a fluorinated cyclic carbonate and a fluorinated chain ester. By using such a solvent, elution of the positive electrode can be suppressed.

The fluorinated cyclic carbonate is preferably a fluorinated cyclic carbonate in which a fluorine atom is directly bonded to a carbonate ring. Examples thereof include 4-fluoroethylene carbonate, 4,5-difluoroethylene carbonate, 4,4-difluoro. Examples thereof include ethylene carbonate, 4,4,5-trifluoroethylene carbonate, and 4,4,5,5-tetrafluoroethylene carbonate. Of these, 4-fluoroethylene carbonate and 4,5-difluoroethylene carbonate are more preferable because of their relatively low viscosity and high formability of a protective film on the negative electrode.
　フッ素化環状炭酸エステルの含有量は、非水電解質の総量に対し５～５０体積％であることが好ましく、１０～４０体積％であることがさらに好ましい。 The content of the fluorinated cyclic carbonate is preferably 5 to 50% by volume, more preferably 10 to 40% by volume, based on the total amount of the nonaqueous electrolyte.
　フッ素化鎖状エステルは、フッ素化鎖状カルボン酸エステル又はフッ素化鎖状炭酸エステルの少なくとも一方を含むことが好ましい。 The fluorinated chain ester preferably contains at least one of a fluorinated chain carboxylate ester or a fluorinated chain carbonate ester.
　フッ素化鎖状カルボン酸エステルの例としては、酢酸メチル、酢酸エチル、酢酸プロピル、プロピオン酸メチル、又はプロピオン酸エチルの水素の一部または全部をフッ素化したものが挙げられる。なかでもメチル３，３，３－トリフルオロプロピオネートは比較的粘度が低いため好ましい。 Examples of the fluorinated chain carboxylic acid ester include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, or ethyl propionate partially or wholly fluorinated. Of these, methyl 3,3,3-trifluoropropionate is preferred because of its relatively low viscosity.
　フッ素化鎖状炭酸エステルの例としては、ジメチルカーボネート、エチルメチルカーボネート、ジエチルカーボネート、メチルプロピルカーボネート、エチルプロピルカーボネート、メチルイソプロピルカーボネートの水素の一部または全部をフッ素化されているものが挙げられる。なかでもメチル２，２，２－トリフルオロエチルカーボネートが好ましい。 Examples of the fluorinated chain carbonate include those in which part or all of hydrogen in dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate is fluorinated. Of these, methyl 2,2,2-trifluoroethyl carbonate is preferred.
　フッ素化鎖状エステルの含有量は、非水電解質の総量に対し３０～９０体積％であることが好ましく、５０～９０体積％であることがさらに好ましい。 The content of the fluorinated chain ester is preferably 30 to 90% by volume, more preferably 50 to 90% by volume, based on the total amount of the nonaqueous electrolyte.
　上記非水電解質には、フッ素化環状炭酸エステル及びフッ素化鎖状エステル以外にも、非水電解質電池に従来使用されている非水電解質を併せて用いることができる。その例として、環状炭酸エステル、鎖状炭酸エステル、エーテル類が挙げられる。環状炭酸エステルの例としては、エチレンカーボネート及びプロピレンカーボネートが挙げられる。鎖状炭酸エステルの例としては、ジメチルカーボネート、エチルメチルカーボネート及びジエチルカーボネートが挙げられる。エーテル類の例としては、１，２－ジメトキシエタンが挙げられる。 As the non-aqueous electrolyte, in addition to the fluorinated cyclic carbonate ester and the fluorinated chain ester, a non-aqueous electrolyte conventionally used in non-aqueous electrolyte batteries can be used together. Examples thereof include cyclic carbonates, chain carbonates, and ethers. Examples of cyclic carbonates include ethylene carbonate and propylene carbonate. Examples of the chain carbonate include dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate. Examples of ethers include 1,2-dimethoxyethane.
　上記非水電解質には、非水電解質電池に従来使用されているアルカリ金属塩が含まれる。その例として、ＬｉＰＦ６及びＬｉＢＦ４が挙げられる。
　本願発明の非水電解質電池には、必要に応じて従来の非水電解質電池に使用されている電池構成部材を使用することができる。以上、本発明を好適な実施形態により説明してきたが、こうした記述は限定事項ではなく、もちろん、種々の改変が可能である。 The non-aqueous electrolyte includes an alkali metal salt conventionally used in non-aqueous electrolyte batteries. Examples thereof include LiPF 6 and LiBF 4 .
In the nonaqueous electrolyte battery of the present invention, battery constituent members used in conventional nonaqueous electrolyte batteries can be used as necessary. As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.
　〔セパレータ〕
　セパレータには、イオン透過性及び絶縁性を有する多孔性シートが用いられる。多孔性シートの具体例としては、微多孔薄膜、織布、不織布等が挙げられる。セパレータの材質としては、ポリエチレン、ポリプロピレン等のポリオレフィンが好適である。 [Separator]
As the separator, a porous sheet having ion permeability and insulating properties is used. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. As the material of the separator, polyolefin such as polyethylene and polypropylene is suitable.
　以下、実施例により本発明をさらに詳細に説明するが、本発明はこれらの実施例に限定されるものではない。
〔試験セルの作製〕
＜実施例１＞
　ＮａＮＯ3、Ｃｏ3Ｏ4、及びＴｉＯ2（アナターゼ型）をＮａ81/81Ｃｏ79/81Ｔｉ1/81Ｏ2の化学量論比に合うように混合した。その後、空気中において９００℃で１０時間保持することによって、ナトリウム含有遷移金属酸化物を得た。 EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.
[Production of test cell]
<Example 1>
NaNO 3 , Co 3 O 4 , and TiO 2 (anatase type) were mixed so as to meet the stoichiometric ratio of Na 81/81 Co 79/81 Ti 1/81 O 2 . Then, the sodium containing transition metal oxide was obtained by hold | maintaining in the air at 900 degreeC for 10 hours.
　ＬｉＮＯ3とＬｉＯＨとをモル比が６１：３９となるように混合した溶融塩床を、得られたナトリウム含有遷移金属酸化物５ｇに対し５倍当量加え、２００℃で１０時間保持させることによって、ナトリウム含有遷移金属酸化物のナトリウムの一部をリチウムにイオン交換した。さらに、イオン交換後の物質を水洗して、リチウム含有遷移金属酸化物を得た。 By adding a 5-fold equivalent of a molten salt bed in which LiNO 3 and LiOH are mixed at a molar ratio of 61:39 to 5 g of the obtained sodium-containing transition metal oxide, and holding at 200 ° C. for 10 hours, A portion of the sodium of the sodium-containing transition metal oxide was ion exchanged with lithium. Further, the ion-exchanged material was washed with water to obtain a lithium-containing transition metal oxide.
　得られたリチウム含有遷移金属酸化物は、粉末Ｘ線回折法により分析を行った結果、空間群Ｐ６3ｍｃと空間群Ｒ―３ｍに属する結晶構造を有することが分かった（図１参照）。 The obtained lithium-containing transition metal oxide was analyzed by powder X-ray diffraction, and as a result, it was found that it had a crystal structure belonging to the space group P6 3 mc and the space group R-3m (see FIG. 1).
　また、ＩＣＰ発光分析を用いてコバルト、マンガン、リチウムおよびナトリウムの定量を行った結果、得られたリチウム含有遷移金属酸化物の組成比は、Ｌｉ0.905Ｎａ0.066Ｃｏ0.988Ｔｉ0.012であることが分かった。 Moreover, as a result of quantitative determination of cobalt, manganese, lithium and sodium using ICP emission analysis, it was found that the composition ratio of the obtained lithium-containing transition metal oxide was Li 0.905 Na 0.066 Co 0.988 Ti 0.012 . .
　得られたリチウム含有遷移金属酸化物を正極活物質とし、正極活物質と導電剤としてのアセチレンブラックと結着剤としてのポリフッ化ビニリデンとを質量比が８０：１０：１０となるように混合した。その後、この混合物にＮ－メチル－２－ピロリドンを加えて正極合剤スラリーを作製した。得られた正極合剤スラリーをアルミニウム箔からなる集電体に塗布し、１１０℃で真空乾燥することで、作用極１を作製した。 The obtained lithium-containing transition metal oxide was used as a positive electrode active material, and the positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed so that the mass ratio was 80:10:10. . Thereafter, N-methyl-2-pyrrolidone was added to the mixture to prepare a positive electrode mixture slurry. The obtained positive electrode mixture slurry was applied to a current collector made of an aluminum foil, and vacuum-dried at 110 ° C. to produce a working electrode 1.
　露点－５０℃以下のドライエアー下で、作用極１、対極２、参照極３、セパレーター４、非水電解質５、及び容器６を用いて図２に示す試験セルを作製した。尚、対極２及び参照極３にはリチウム金属を用いた。セパレーター４には、ポリエチレン製セパレーターを用いた。非水電解質５には、４－フルオロエチレンカーボネート（ＦＥＣ）とメチル３，３，３－トリフルオロプロピオネート（Ｆ－ＭＰ）とを体積比が２：８になるように混合した非水電解液に、ＬｉＰＦ6を１．０ ｍｏｌ／Ｌの濃度になるように溶解させたものを用いた。作用極１、対極２、及び参照極３には、それぞれ電極タブ７が取り付けられている。
＜実施例２＞
　ＮａＮＯ3、Ｃｏ3Ｏ4、ＴｉＯ2（アナターゼ型）及びＭｎ2Ｏ3をＮａ79/81Ｃｏ79/81Ｍｎ1/81Ｔｉ1/81Ｏ2の化学量論比に合うように混合した以外は実施例１と同様にして試験セルを作製した。
＜実施例３＞
　ＮａＮＯ3、Ｃｏ3Ｏ4、ＴｉＯ2（アナターゼ型）及びＭｎ2Ｏ3をＮａ78/81Ｃｏ78/81Ｍｎ2/81Ｔｉ1/81Ｏ2の化学量論比に合うように混合した以外は実施例１と同様にして試験セルを作製した。
＜実施例４＞
　ＮａＮＯ3、Ｃｏ3Ｏ4、ＴｉＯ2（アナターゼ型）及びＭｎ2Ｏ3をＮａ78/81Ｃｏ78/81Ｍｎ1/81Ｔｉ2/81Ｏ2の化学量論比に合うように混合した以外は実施例１と同様にして試験セルを作製した。
＜実施例５＞
　ＮａＮＯ3、Ｃｏ3Ｏ4、及びＴｉＯ2（アナターゼ型）をＮａ78/81Ｃｏ78/81Ｔｉ3/81Ｏ2の化学量論比に合うように混合した以外は実施例１と同様にして試験セルを作製した。
＜比較例１＞
ＮａＮＯ3、Ｃｏ3Ｏ4、及びＴｉＯ2（アナターゼ型）をＮａ81/81Ｃｏ79/81Ｔｉ1/81Ｏ2の化学量論比に合うように混合し、実施例１と同様にリチウム含有遷移金属酸化物を得た。 A test cell shown in FIG. 2 was prepared using the working electrode 1, the counter electrode 2, the reference electrode 3, the separator 4, the nonaqueous electrolyte 5, and the container 6 under dry air having a dew point of −50 ° C. or less. Note that lithium metal was used for the counter electrode 2 and the reference electrode 3. As the separator 4, a polyethylene separator was used. The non-aqueous electrolyte 5 is a non-aqueous electrolyte in which 4-fluoroethylene carbonate (FEC) and methyl 3,3,3-trifluoropropionate (F-MP) are mixed so that the volume ratio is 2: 8. In addition, LiPF 6 dissolved at a concentration of 1.0 mol / L was used. Electrode tabs 7 are attached to the working electrode 1, the counter electrode 2, and the reference electrode 3, respectively.
<Example 2>
Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 79/81 Co 79/81 Mn 1/81 Ti 1/81 O 2 A test cell was prepared in the same manner as in Example 1.
<Example 3>
Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 78/81 Co 78/81 Mn 2/81 Ti 1/81 O 2 A test cell was prepared in the same manner as in Example 1.
<Example 4>
Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 78/81 Co 78/81 Mn 1/81 Ti 2/81 O 2 A test cell was prepared in the same manner as in Example 1.
<Example 5>
Except that NaNO 3 , Co 3 O 4 , and TiO 2 (anatase type) were mixed in accordance with the stoichiometric ratio of Na 78/81 Co 78/81 Ti 3/81 O 2 , the same as in Example 1. A test cell was prepared.
<Comparative Example 1>
NaNO 3 , Co 3 O 4 , and TiO 2 (anatase type) were mixed so as to match the stoichiometric ratio of Na 81/81 Co 79/81 Ti 1/81 O 2 , and lithium-containing as in Example 1. A transition metal oxide was obtained.
　得られたリチウム含有遷移金属酸化物を正極活物質として、
エチレンカーボネート（ＥＣ）とエチルメチルカーボネート（ＥＭＣ）とを体積比が２：８になるように混合した非水電解液に、ＬｉＰＦ6を１．０ ｍｏｌ／ｌの濃度になるように溶解させたものを非水電解質として用いたこと以外は、実施例１と同様にして試験セルを作製した。
＜比較例２＞
　ＮａＮＯ3、Ｃｏ3Ｏ4、ＴｉＯ2（アナターゼ型）及びＭｎ2Ｏ3をＮａ79/81Ｃｏ79/81Ｍｎ1/81Ｔｉ1/81Ｏ2の化学量論比に合うように混合した以外は比較例１と同様にして試験セルを作製した。
＜比較例３＞
　ＮａＮＯ3、Ｃｏ3Ｏ4、ＴｉＯ2（アナターゼ型）及びＭｎ2Ｏ3をＮａ78/81Ｃｏ78/81Ｍｎ2/81Ｔｉ1/81Ｏ2の化学量論比に合うように混合した以外は比較例１と同様にして試験セルを作製した。 Using the obtained lithium-containing transition metal oxide as a positive electrode active material,
LiPF 6 was dissolved to a concentration of 1.0 mol / l in a non-aqueous electrolyte in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 2: 8. A test cell was prepared in the same manner as in Example 1 except that the sample was used as a nonaqueous electrolyte.
<Comparative Example 2>
Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 79/81 Co 79/81 Mn 1/81 Ti 1/81 O 2 Produced a test cell in the same manner as in Comparative Example 1.
<Comparative Example 3>
Other than mixing NaNO 3 , Co 3 O 4 , TiO 2 (anatase type) and Mn 2 O 3 to match the stoichiometric ratio of Na 78/81 Co 78/81 Mn 2/81 Ti 1/81 O 2 Produced a test cell in the same manner as in Comparative Example 1.
　実施例１～６、比較例１～３および空間群Ｒ－３ｍに属するＸＲＤプロファイル例としてＬｉＣｏＯ２（ＰＤＦ＃７５-０５３２）を図１に示す。 FIG. 1 shows LiCoO 2 (PDF # 75-0532) as an example of an XRD profile belonging to Examples 1 to 6, Comparative Examples 1 to 3, and space group R-3m.
　図１より実施例１～５、および比較例1～３には、空間群Ｐ６3ｍｃに対応するピークに加え、ＬｉＣｏＯ２と同様なピークプロファイルである００３および１０４の指数に対応するピークが確認できた。＊を付けたピークはイオン交換されずに残ったナトリウム酸化物のピークと推察される。 From FIG. 1, in Examples 1 to 5 and Comparative Examples 1 to 3, in addition to peaks corresponding to the space group P6 3 mc, peaks corresponding to indices of 003 and 104, which are the same peak profiles as LiCoO2, can be confirmed. It was. The peak marked with * is presumed to be the peak of sodium oxide remaining without ion exchange.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
〔充放電サイクル試験〕
　実施例１～３及び比較例１～３の各試験セルについて、０．２Ｉｔの定電流で正極電位が４．８Ｖ（vs. Ｌｉ／Ｌｉ+）に達するまで充電した。その後、０．２Ｉｔの定電流で正極電位が３．２Ｖ（vs. Ｌｉ／Ｌｉ+）に達するまで放電を行った。これを１０回繰り返し、１０サイクル目の容量を測定し、１０サイクル目の放電容量密度を１サイクル目の放電容量密度で除し、１００倍することで容量維持率を算出した。 [Charge / discharge cycle test]
The test cells of Examples 1 to 3 and Comparative Examples 1 to 3 were charged with a constant current of 0.2 It until the positive electrode potential reached 4.8 V (vs. Li / Li + ). Thereafter, discharging was performed at a constant current of 0.2 It until the positive electrode potential reached 3.2 V (vs. Li / Li + ). This was repeated 10 times, the capacity at the 10th cycle was measured, the discharge capacity density at the 10th cycle was divided by the discharge capacity density at the 1st cycle, and the capacity retention rate was calculated by multiplying by 100.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
表２の比較例1と実施例１とを比較すると、同一活物質では、非水電解質にＦＥＣ／ＦＭＰのフッ素系電解液を利用することで、サイクル特性が向上する。同様の効果は実施例２、３においても得られた。一般にフッ素含有非電解質は、耐酸化性が高く、充電電位４．８Ｖ（リチウム基準）でも安定していることが予想され、非水電解質の分解生成物が引き起こしうる正極へのダメージを減らすことができる。 Comparing Comparative Example 1 and Example 1 in Table 2 with the same active material, the cycle characteristics are improved by using a fluorine-based electrolytic solution of FEC / FMP as the non-aqueous electrolyte. Similar effects were obtained in Examples 2 and 3. In general, fluorine-containing non-electrolytes have high oxidation resistance and are expected to be stable even at a charging potential of 4.8 V (based on lithium), thereby reducing damage to the positive electrode that can be caused by decomposition products of the non-aqueous electrolyte. it can.
　また、空間群Ｐ６3ｍｃを有する正極活物質と空間群Ｒ－３ｍを有する正極活物質が共に存在することで、空間群Ｒ－３ｍを有する正極活物質の構造変化が抑制されることから、サイクルに伴う構造変化による容量減少を抑えることができる。 Moreover, by the positive electrode active material having a positive electrode active material and the space group R-3m having a space group P6 3 mc are both present, since the structural change of the positive electrode active material having a space group R-3m is suppressed, Capacitance reduction due to structural changes accompanying cycles can be suppressed.
　空間群Ｐ６3ｍｃを有する正極活物質と空間群Ｒ－３ｍを有する正極活物質は、Ｐ２構造（空間群：Ｐ６3/ｍｍｃ）のナトリウム酸化物を、イオン交換することで生成し、ＸＲＤ測定から、空間群Ｐ６3ｍｃを有する正極活物質の量より空間群Ｒ－３ｍを有する正極活物質の量が少ないことがわかる。 A positive electrode active material having a space group P6 3 mc and a positive electrode active material having a space group R-3m are produced by ion exchange of sodium oxide having a P2 structure (space group: P6 3 / mmc), and are subjected to XRD measurement. From this, it can be seen that the amount of the positive electrode active material having the space group R-3m is smaller than the amount of the positive electrode active material having the space group P6 3 mc.
　空間群Ｒ－３ｍに属する正極活物質由来のピークと考えられる指数１０４のピーク強度（Iｒ）と空間群Ｐ６3ｍｃに属する正極活物質由来のピークと考えられる指数１０３のピーク強度（Iｐ１）、および（１１０）のピーク強度（Iｐ２）よりＩa（＝Iｒ／Iｐ１）、Iｂ（＝Iｒ／Iｐ２）を見積もった。 The peak intensity (Ir) of index 104 considered to be a peak derived from the positive electrode active material belonging to space group R-3m, and the peak intensity (Ip1) of index 103 considered to be a peak derived from the positive electrode active material belonging to space group P6 3 mc, And Ia (= Ir / Ip1) and Ib (= Ir / Ip2) were estimated from the peak intensity (Ip2) of (110).
　よって、０＜Iａ≦７．００が好ましい。さらに好ましくは、０．０７≦Iａ≦７．００である。また、０＜Iｂ≦３．００が好ましい。さらに好ましくは、０．２≦Iｂ≦３．００である。 Therefore, 0 <Ia ≦ 7.00 is preferable. More preferably, 0.07 ≦ Ia ≦ 7.00. Further, 0 <Ib ≦ 3.00 is preferable. More preferably, 0.2 ≦ Ib ≦ 3.00.
　このピーク強度範囲において、空間群Ｒ－３ｍに属する正極活物質と空間群Ｐ６3ｍｃに属する正極活物質が共に存在していても、良好な容量維持率が得られる。 In this peak intensity range, even when a positive electrode active material belonging to the space group R-3m and a positive electrode active material belonging to the space group P6 3 mc are both present, a good capacity retention rate can be obtained.
　Iａが７より大きく、かつＩｂが３より大きい際には、４．６Ｖ（リチウム基準）以上の充電電位では構造劣化を引き起こすことが考えられる。 When Ia is larger than 7 and Ib is larger than 3, it is considered that structural deterioration is caused at a charging potential of 4.6 V (lithium reference) or higher.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　本発明による密閉型電池は、パーソナルコンピュータ、携帯電話等の電子機器や、電気自動車や電動工具等の電源に好適に用いられる。 The sealed battery according to the present invention is suitably used for electronic devices such as personal computers and mobile phones, and electric power sources such as electric vehicles and electric tools.
１・・・作用極
２・・・対極
３・・・参照極
４・・・セパレーター
５・・・非水電解質
６・・・容器
７・・・集電タブ DESCRIPTION OF SYMBOLS 1 ... Working electrode 2 ... Counter electrode 3 ... Reference electrode 4 ... Separator 5 ... Nonaqueous electrolyte 6 ... Container 7 ... Current collection tab

Claims (13)

  1. 　正極活物質を含む正極と、負極と、非水電解質とを備え、
    　前記正極活物質が、空間群Ｐ６3ｍｃに属する結晶構造を有するリチウム含有遷移金属酸化物と空間群Ｒ－３ｍに属する結晶構造を有するリチウム含有遷移金属酸化物を共に含み、
    　前記非水電解質が、フッ素化環状炭酸エステルとフッ素化鎖状エステルとを含む、ことを特徴とする非水電解質二次電池。     A positive electrode containing a positive electrode active material, a negative electrode, and a non-aqueous electrolyte,
    The positive electrode active material includes both a lithium-containing transition metal oxide having a crystal structure belonging to space group P6 3 mc and a lithium-containing transition metal oxide having a crystal structure belonging to space group R-3m;
    The non-aqueous electrolyte secondary battery, wherein the non-aqueous electrolyte includes a fluorinated cyclic carbonate and a fluorinated chain ester.
  2. 　前記リチウム含有遷移金属酸化物が、０＜Iａ≦７．００を満たす請求項１に記載の非水電解質二次電池。 The non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium-containing transition metal oxide satisfies 0 <Ia ≦ 7.00.
  3. 　前記リチウム含有遷移金属酸化物が、０＜Iｂ≦３．００を満たす請求項１または２に記載の非水電解質二次電池。 The non-aqueous electrolyte secondary battery according to claim 1, wherein the lithium-containing transition metal oxide satisfies 0 <Ib ≦ 3.00.
  4. 　前記空間群Ｐ６3ｍｃに属する結晶構造を有するリチウム含有遷移金属酸化物が、Ｌｉｘ１Ｎａｙ１ＣｏαＭβＯγ（０．８０＜ｘ１＜１.１、０＜ｙ１≦０．１０、０．９５＜α＜１、０＜β≦０．０５、１．９γ≦２．１、ＭはＣｏ以外の金属元素）で表されることを特徴とする、請求項１から３のいずれかに記載の非水電解質二次電池。 Lithium-containing transition metal oxide having a crystal structure belonging to the space group P6 3 mc is, Li x1 Na y1 Co α M β O γ (0.80 <x1 <1.1,0 <y1 ≦ 0.10,0 .95 <α <1, 0 <β ≦ 0.05, 1.9γ ≦ 2.1, and M is a metal element other than Co). The nonaqueous electrolyte secondary battery as described.
  5. 　前記空間群Ｐ６3ｍｃに属する結晶構造を有するリチウム含有遷移金属酸化物が、Ｌｉｘ１Ｎａｙ１ＣｏαＭβＯγ（０．８０＜ｘ１＜１.１、０＜ｙ１≦０．１０、０．９５＜α＜１、０＜β≦０．０５、１．９γ≦２．１、ＭはＣｏ以外の金属元素で少なくともＭｎもしくはＴｉを含む）で表されることを特徴とする、請求項１から３のいずれかに記載の非水電解質二次電池。 Lithium-containing transition metal oxide having a crystal structure belonging to the space group P6 3 mc is, Li x1 Na y1 Co α M β O γ (0.80 <x1 <1.1,0 <y1 ≦ 0.10,0 .95 <α <1, 0 <β ≦ 0.05, 1.9γ ≦ 2.1, and M is a metal element other than Co and contains at least Mn or Ti. The nonaqueous electrolyte secondary battery according to any one of 1 to 3.
  6. 前記空間群Ｐ６3ｍｃに属する結晶構造を有するリチウム含有遷移金属酸化物と空間群Ｒ－３ｍに属する結晶構造を有するリチウム含有遷移金属酸化物の全組成比率がＬｉｘ１Ｎａｙ１ＣｏαＭβＯγ（０．８０＜ｘ１＜１.１、０＜ｙ１≦０．１０、０．９５＜α＜１、０＜β≦０．０５、１．９γ≦２．１、ＭはＣｏ以外の金属元素で少なくともＭｎもしくはＴｉを含む）で表されることを特徴とする、請求項１から３のいずれかに記載の非水電解質二次電池。 The total composition ratio of the lithium-containing transition metal oxide having a crystal structure belonging to the space group P6 3 mc and the lithium-containing transition metal oxide having a crystal structure belonging to the space group R-3m is Li x1 Na y1 Co α M β O γ (0.80 <x1 <1.1, 0 <y1 ≦ 0.10, 0.95 <α <1, 0 <β ≦ 0.05, 1.9γ ≦ 2.1, M is a metal other than Co The nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the nonaqueous electrolyte secondary battery is represented by an element including at least Mn or Ti.
  7. 　前記空間群Ｐ６3ｍｃに属する結晶構造を有するリチウム含有遷移金属酸化物と空間群Ｒ－３ｍに属する結晶構造を有するリチウム含有遷移金属酸化物が、Ｎａｙ２ＣｏαＭβＯγ（０．６６＜ｙ２＜１．０、０．９５＜α＜１、０＜β≦０．０５、１．９≦γ≦２．１、ＭはＣｏ以外の金属元素で少なくともＭｎもしくはＴｉを含む）で表されるナトリウム含有酸化物に含まれるナトリウムの一部をリチウムでイオン交換することによって得られるリチウム含有遷移金属酸化物であることを特徴とする、請求項１から３のいずれかに記載の非水電解質二次電池。 The lithium-containing transition metal oxide having a crystal structure belonging to the space group P6 3 mc and the lithium-containing transition metal oxide having a crystal structure belonging to the space group R-3m are Na y2 Co α M β O γ (0.66 <Y2 <1.0, 0.95 <α <1, 0 <β ≦ 0.05, 1.9 ≦ γ ≦ 2.1, M is a metal element other than Co and contains at least Mn or Ti) The non-water according to any one of claims 1 to 3, which is a lithium-containing transition metal oxide obtained by ion exchange of a part of sodium contained in the sodium-containing oxide to be obtained with lithium. Electrolyte secondary battery.
  8. 　前記フッ素化環状炭酸エステルが、４－フルオロエチレンカーボネート又は４，５－ジフルオロエチレンカーボネートの少なくとも一方を含むことを特徴とする、請求項１から７のいずれかに記載の非水電解質二次電池。 The nonaqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein the fluorinated cyclic carbonate includes at least one of 4-fluoroethylene carbonate and 4,5-difluoroethylene carbonate.
  9. 　前記フッ素化鎖状エステルが、フッ素化鎖状カルボン酸エステル又はフッ素化鎖状炭酸エステルの少なくとも一方を含むことを特徴とする、請求項１から８のいずれかに記載の非水電解質二次電池。 9. The nonaqueous electrolyte secondary battery according to claim 1, wherein the fluorinated chain ester contains at least one of a fluorinated chain carboxylic acid ester and a fluorinated chain carbonate ester. 10. .
  10. 　前記フッ素化鎖状カルボン酸エステルが、メチル３，３，３－トリフルオロプロピオネートを含むことを特徴とする、請求項９に記載の非水電解質二次電池。 The nonaqueous electrolyte secondary battery according to claim 9, wherein the fluorinated chain carboxylic acid ester contains methyl 3,3,3-trifluoropropionate.
  11. 　前記フッ素化鎖状炭酸エステルが、メチル２，２，２－トリフルオロエチルカーボネートを含むことを特徴とする、請求項８に記載の非水電解質二次電池。 The non-aqueous electrolyte secondary battery according to claim 8, wherein the fluorinated chain carbonate includes methyl 2,2,2-trifluoroethyl carbonate.
  12. 　正極電位が４．６Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）を超えるまで充電することを特徴とする、請求項１～１１のいずれか１項に記載の非水電解質二次電池。 The nonaqueous electrolyte secondary battery according to any one of claims 1 to 11, wherein the battery is charged until the positive electrode potential exceeds 4.6 V (vs. Li / Li + ).
  13. 　正極活物質中の、空間群Ｐ６3ｍｃに属する結晶構造を有するリチウム含有遷移金属酸化物の物質量（mol）が空間群Ｒ－３ｍに属する結晶構造を有するリチウム含有遷移金属酸化物の物質量（mol）より多いことを特徴とする請求項１～１２のいずれか１項に記載の非水電解質二次電池。 The amount of lithium-containing transition metal oxide having a crystal structure belonging to space group R-3m in which the amount (mol) of lithium-containing transition metal oxide having a crystal structure belonging to space group P6 3 mc in the positive electrode active material The nonaqueous electrolyte secondary battery according to any one of claims 1 to 12, wherein the amount is more than (mol).
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