WO2013065513A1 - Positive-electrode active material of non-aqueous electrolyte secondary cell, and non-aqueous electrolyte secondary cell - Google Patents

Positive-electrode active material of non-aqueous electrolyte secondary cell, and non-aqueous electrolyte secondary cell Download PDF

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WO2013065513A1
WO2013065513A1 PCT/JP2012/077231 JP2012077231W WO2013065513A1 WO 2013065513 A1 WO2013065513 A1 WO 2013065513A1 JP 2012077231 W JP2012077231 W JP 2012077231W WO 2013065513 A1 WO2013065513 A1 WO 2013065513A1
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oxide
positive electrode
electrolyte secondary
active material
secondary battery
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PCT/JP2012/077231
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French (fr)
Japanese (ja)
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デニス ヤウワイ ユ
柳田　勝功
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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
    • 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
    • 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
    • H01M4/36—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 positive electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.
  • non-aqueous electrolyte secondary batteries have been widely used as power sources for electronic devices and the like.
  • a carbon material such as graphite is used as the negative electrode active material of the non-aqueous electrolyte secondary battery.
  • graphite is used as the negative electrode active material of the non-aqueous electrolyte secondary battery.
  • a negative electrode active material that can replace the graphite and that can further increase the battery capacity has been conducted.
  • negative electrode active materials Materials that can be alloyed with lithium such as silicon have been studied as negative electrode active materials that can replace graphite.
  • the negative electrode active material made of a material alloyed with lithium generally has a large irreversible capacity, and the charge / discharge cycle is likely to decrease.
  • Patent Document 1 as a positive electrode active material, a first Li-containing transition metal composite oxide as a main component and a second Li-containing transition metal composite as a subcomponent are used. And using Li (Li x Mn 2x Co 1-3x ) O 2 (where 0 ⁇ x ⁇ 1/3) as the second Li-containing transition metal composite oxide.
  • Li (Li x Mn 2x Co 1-3x ) O 2 where 0 ⁇ x ⁇ 1/3) as the second Li-containing transition metal composite oxide.
  • Patent Document 1 when an irreversible capacity is given to the negative electrode active material, it is necessary to increase the initial charge end voltage of the battery. However, when the initial charge end voltage of the battery is increased, the nonaqueous electrolyte may be decomposed, and the charge / discharge cycle characteristics of the battery may be deteriorated.
  • the present invention does not require a high initial charge end voltage of a non-aqueous electrolyte secondary battery, and can impart excellent charge / discharge cycle characteristics to the non-aqueous electrolyte secondary battery.
  • the main purpose is to provide active materials.
  • the positive electrode active material of the nonaqueous electrolyte secondary battery of the present invention includes a first oxide and a second oxide.
  • the first oxide has a general formula: LiCo z M 1-z O 2 [wherein z is 0.3 ⁇ z ⁇ 1 and M is at least one of Ni and Mn. ] It consists of a compound represented by this.
  • the second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the positive electrode potential is 3.0 V (vs. Li / Li + ) To 4.3 V (vs.
  • the initial charge capacity of the nonaqueous electrolyte secondary battery is that the first oxide is used as the positive electrode active material instead of the second oxide.
  • the initial charge capacity of the non-aqueous electrolyte secondary battery is larger than the initial charge capacity of the non-aqueous electrolyte secondary battery using the positive electrode, and the first oxide is used as the positive electrode active material instead of the second oxide.
  • the lithium-containing metal oxide is lower than the initial charge / discharge efficiency of the nonaqueous electrolyte secondary battery using the positive electrode.
  • the nonaqueous electrolyte secondary battery of the present invention includes a positive electrode including the positive electrode active material, a negative electrode, a nonaqueous electrolyte, and a separator.
  • the nonaqueous electrolyte secondary battery can provide excellent charge / discharge cycle characteristics to the nonaqueous electrolyte secondary battery.
  • the positive electrode active material can be provided.
  • FIG. 1 is a schematic cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention.
  • FIG. 2 is a schematic diagram of a three-electrode test cell using the positive electrodes prepared in Examples, Comparative Examples and Reference Examples as working electrodes.
  • the nonaqueous electrolyte secondary battery 1 includes a battery container 17.
  • the battery case 17 is a cylindrical shape.
  • the shape of the battery container is not limited to a cylindrical shape.
  • the shape of the battery container may be, for example, a flat shape.
  • an electrode body 10 impregnated with a nonaqueous electrolyte is accommodated.
  • non-aqueous electrolyte for example, a known non-aqueous electrolyte can be used.
  • the non-aqueous electrolyte includes a solute, a non-aqueous solvent, and the like.
  • LiXF y As the solute of the nonaqueous electrolyte, for example, LiXF y (wherein X is P, As, Sb, B, Bi, Al, Ga or In, and y is 6 when X is P, As or Sb)
  • X is B, Bi, the y when Al, Ga or in, a 4
  • LiPF 6 LiBF 4 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO 2 ) 3 , LiC (C 2 F 5 SO 2 ) 3 and the like are preferable.
  • the nonaqueous electrolyte may contain one type of solute or may contain a plurality of types of solutes.
  • non-aqueous solvent for the non-aqueous electrolyte examples include cyclic carbonate, chain carbonate, or a mixed solvent of cyclic carbonate and chain carbonate.
  • cyclic carbonate examples include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, and the like.
  • chain carbonate examples include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate and the like.
  • a mixed solvent of a cyclic carbonate and a chain carbonate is preferably used as a non-aqueous solvent having a low viscosity, a low melting point, and a high lithium ion conductivity.
  • the mixing ratio of cyclic carbonate and chain carbonate should be in the range of 1: 9 to 5: 5 by volume ratio. Is preferred.
  • the non-aqueous solvent may be a mixed solvent of a cyclic carbonate and an ether solvent such as 1,2-dimetaxethane and 1,2-diethoxyethane.
  • an ionic liquid can be used as a nonaqueous solvent for the nonaqueous electrolyte.
  • the cation species and anion species of the ionic liquid are not particularly limited. From the viewpoint of low viscosity, electrochemical stability, and hydrophobicity, for example, a pyridinium cation, an imidazolium cation, or a quaternary ammonium cation is preferably used as the cation.
  • an ionic liquid containing a fluorine-containing imide anion is preferably used as the anion.
  • the non-aqueous electrolyte may be a gel polymer electrolyte obtained by impregnating a polymer electrolyte such as polyethylene oxide or polyacrylonitrile with an electrolytic solution, or an inorganic solid electrolyte such as LiI or Li 3 N.
  • the electrode body 10 is formed by winding a negative electrode 11, a positive electrode 12, and a separator 16 disposed between the negative electrode 11 and the positive electrode 12.
  • the separator 16 is not particularly limited as long as it can suppress a short circuit due to contact between the negative electrode 11 and the positive electrode 12 and can impregnate a nonaqueous electrolyte to obtain lithium ion conductivity.
  • the separator 16 can be formed of a resin porous film.
  • the resin porous film include a polypropylene or polyethylene porous film, a laminate of a polypropylene porous film and a polyethylene porous film, and the like.
  • the negative electrode 11 has a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode current collector can be composed of, for example, a foil made of a metal such as Cu or an alloy containing a metal such as Cu.
  • the negative electrode active material layer contains a negative electrode active material.
  • the negative electrode active material is not particularly limited as long as it can reversibly store and release lithium.
  • Examples of the negative electrode active material include a carbon material, a material alloyed with lithium, and a metal oxide such as tin oxide.
  • Specific examples of the carbon material include natural graphite, artificial graphite, mesophase pitch-based carbon fiber (MCF), mesocarbon microbeads (MCMB), coke, hard carbon, fullerene, and carbon nanotube.
  • Examples of the material to be alloyed with lithium include one or more metals selected from the group consisting of silicon, germanium, tin and aluminum, or one or more types selected from the group consisting of silicon, germanium, tin and aluminum. The thing which consists of an alloy containing a metal is mentioned.
  • the negative electrode active material layer may contain a known carbon conductive agent such as graphite and a known binder such as sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR).
  • a known carbon conductive agent such as graphite
  • a known binder such as sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR).
  • the positive electrode 12 has a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.
  • the positive electrode current collector can be made of, for example, a metal such as Al or an alloy containing a metal such as Al.
  • the positive electrode active material layer includes a positive electrode active material.
  • the positive electrode active material layer may contain appropriate materials such as a binder and a conductive agent in addition to the positive electrode active material.
  • a binder preferably used include, for example, polyvinylidene fluoride.
  • a conductive agent preferably used include carbon materials such as graphite and acetylene black.
  • the positive electrode active material includes a first oxide and a second oxide.
  • the first oxide has a general formula: LiCo z M 1-z O 2 [wherein z is 0.3 ⁇ z ⁇ 1 and M is at least one of Ni and Mn. ] It consists of a compound represented by this.
  • the first oxide preferably has a crystal structure belonging to the space group R-3m.
  • the first oxide is preferably lithium cobalt oxide (LiCoO 2 ).
  • the lithium cobalt oxide preferably has a layered structure.
  • the first oxide is preferably contained in the positive electrode active material by about 60% by mass to 95% by mass, and more preferably by about 70% by mass to 90% by mass.
  • the second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the positive electrode potential is 3.0 V (vs. Li / Li + ) To 4.3 V (vs. Li / Li + ), the initial charge capacity of the nonaqueous electrolyte secondary battery is that the first oxide is used as the positive electrode active material instead of the second oxide.
  • the initial charge capacity of the non-aqueous electrolyte secondary battery is larger than the initial charge capacity of the non-aqueous electrolyte secondary battery using the positive electrode, and the first oxide is used as the positive electrode active material instead of the second oxide.
  • the second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the potential of the positive electrode is 3.0 V (vs.
  • the initial state of the non-aqueous electrolyte secondary battery is The charge / discharge efficiency is positive when the first oxide is used as the positive electrode active material instead of the second oxide. Aqueous lower than the initial charge-discharge efficiency of electrolyte secondary battery using a lithium-containing metal oxide.
  • the second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the positive electrode potential is 3.0 V (vs. Li / Li + ) To 4.3 V (vs. Li / Li + ), the initial charge capacity of the nonaqueous electrolyte secondary battery exceeds 170 mAh / g, and the initial charge of the nonaqueous electrolyte secondary battery is A lithium-containing metal oxide that has a discharge efficiency of less than 70% is preferable.
  • the initial charge capacity is more preferably over 180 mAh / g.
  • the initial charge / discharge efficiency is more preferably less than 60%.
  • the surface area of the second oxide is preferably greater than 3 m 2 / g and more preferably greater than 7 m 2 / g in terms of BET specific surface area.
  • the surface area of the second oxide is a BET specific surface area and usually does not exceed 50 m 2 / g.
  • the second oxide is preferably contained in the positive electrode active material by about 5% by mass to 40% by mass, and more preferably by about 10% by mass to 30% by mass.
  • the second oxide is preferably a lithium-containing manganese oxide, and more preferably lithium manganate (LiMnO 2 ).
  • LiMnO 2 preferably has a crystal structure belonging to the space group c2 / m or a crystal structure belonging to the space group Pmnm.
  • the negative electrode active material made of a material that is alloyed with lithium such as silicon generally has a problem that the irreversible capacity is large and the charge / discharge cycle tends to decrease.
  • Patent Document 1 it is necessary to increase the initial charge end voltage of the battery when providing the irreversible capacity to the negative electrode active material. If the initial charge end voltage of the battery is increased, the nonaqueous electrolyte may be decomposed, and the charge / discharge cycle characteristics of the battery may deteriorate.
  • the positive electrode active material according to the present embodiment includes the first oxide and the second oxide. According to the positive electrode active material according to the present embodiment, it is not necessary to set the initial charge end voltage of the nonaqueous electrolyte secondary battery 1 high, and excellent charge / discharge cycle characteristics are imparted to the nonaqueous electrolyte secondary battery 1. obtain.
  • the reason for this can be considered as follows. That is, the second oxide of the positive electrode active material according to the present embodiment is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the potential of the positive electrode. Is charged from 3.0 V (vs. Li / Li + ) to 4.3 V (vs.
  • the initial charge / discharge efficiency of the nonaqueous electrolyte secondary battery is Instead, it comprises a lithium-containing metal oxide that is lower than the initial charge / discharge efficiency of the nonaqueous electrolyte secondary battery using the positive electrode using the first oxide as the positive electrode active material. For this reason, in the initial charge / discharge process of the nonaqueous electrolyte secondary battery 1, a sufficient amount of irreversible capacity can be given from the positive electrode active material to the negative electrode active material, and the negative electrode active material is prevented from being overdischarged. be able to.
  • the lithium-containing metal oxide constituting the second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal.
  • the initial charge capacity of the non-aqueous electrolyte secondary battery is replaced with the second oxide.
  • the initial charge capacity of the nonaqueous electrolyte secondary battery using the positive electrode using the first oxide as the positive electrode active material is larger. For this reason, it is possible to give a sufficient amount of irreversible capacity to the negative electrode active material in the initial charge / discharge process while suppressing a decrease in the initial charge capacity of the nonaqueous electrolyte secondary battery 1.
  • a nonaqueous electrolyte using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal in addition to the first oxide, a nonaqueous electrolyte using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal.
  • the initial charge / discharge of the nonaqueous electrolyte secondary battery A second oxide composed of a lithium-containing metal oxide whose efficiency is lower than the initial charge / discharge efficiency of a nonaqueous electrolyte secondary battery using a positive electrode in which the first oxide is used as the positive electrode active material instead of the second oxide.
  • the negative electrode active material By including the negative electrode active material, a sufficient amount of irreversible capacity can be imparted to the negative electrode active material even when the end-of-charge voltage is set low when the nonaqueous electrolyte secondary battery 1 is initially charged. Can be made difficult.
  • the negative electrode active material is a material that is alloyed with lithium, the charge / discharge cycle is likely to be reduced. Without setting it high, the non-aqueous electrolyte secondary battery 1 can be provided with excellent charge / discharge cycle characteristics.
  • the non-aqueous electrolyte secondary battery in which the second oxide is a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal has a positive electrode potential of 3.0 V (vs. Li / Li + ) To 4.3 V (vs. Li / Li + ), the initial charge capacity of the nonaqueous electrolyte secondary battery exceeds 170 mAh / g, and the initial charge of the nonaqueous electrolyte secondary battery is When the discharge efficiency is a lithium-containing metal oxide that is less than 70%, a sufficient amount from the positive electrode active material to the negative electrode active material even if the initial charge end voltage of the nonaqueous electrolyte secondary battery 1 is set lower. Of irreversible capacity.
  • the surface area of the second oxide exceeds 3 m 2 / g in terms of the BET specific surface area, a sufficient amount of irreversible capacity can be imparted to the negative electrode active material even if the amount of the second oxide in the positive electrode active material is reduced.
  • the charge / discharge cycle of the non-aqueous electrolyte secondary battery 1 can be improved.
  • the positive electrode active material in the nonaqueous electrolyte secondary battery 1, by using the positive electrode active material according to the present embodiment, a sufficient amount for the negative electrode active material even when the charge end potential of the positive electrode is 4.3 V (vs. Li / Li + ) or less. Of irreversible capacity.
  • Example 1 [Positive electrode active material] ⁇ First oxide> A predetermined amount of Li 2 CO 3 and Co 3 O 4 were mixed and held in air at 900 ° C. for 10 hours to obtain LiCoO 2 as the first oxide. When the obtained LiCoO 2 was analyzed by an X-ray diffraction method, the LiCoO 2 had a layered structure. LiCoO 2 had a crystal structure belonging to the space group R-3m.
  • LiMnO 2 As a second oxide.
  • the obtained LiMnO 2 had a BET specific surface area of 13 m 2 / g and an average particle size of 13 ⁇ m in d50.
  • LiMnO 2 was analyzed by X-ray diffraction, LiMnO 2 had a crystal structure belonging to the space group Pmnm.
  • the ratio (Ia / Ib) between the peak intensity Ia at 24.6 ° and the peak intensity Ib at 15.3 ° of LiMnO 2 was 0.37.
  • the ratio (Ic / Ib) of the peak intensity Ic at 45.0 ° to the peak intensity Ib at 15.3 ° of LiMnO 2 was 0.99.
  • the obtained positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed at a mass ratio of 90: 5: 5.
  • N-methyl-2-pyrrolidone was added to this mixture to prepare a positive electrode mixture slurry.
  • the obtained positive electrode mixture slurry was applied to a positive electrode current collector made of an aluminum foil and vacuum-dried at 110 ° C. to produce a positive electrode.
  • a three-electrode test cell 20 as shown in FIG. 2 was produced.
  • the above positive electrode was used as the working electrode 21 in an argon atmosphere.
  • Lithium metal was used as the counter electrode 22 and the reference electrode 23.
  • a polyethylene separator was used as the separator.
  • the non-aqueous electrolyte 24 a solution obtained by dissolving LiPF 6 to a concentration of 1.0 mol / l in a non-aqueous solvent in which ethylene carbonate and diethyl carbonate are mixed so as to have a volume ratio of 3: 7 is used. It was.
  • a current collecting tab was attached to each of the working electrode 21, the counter electrode 22, and the reference electrode 23.
  • An electrode-type test cell 20 was produced, and the initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, and capacity maintenance ratio at the 35th cycle were measured. These measurement results are shown in Table 1.
  • Example 1 A three-electrode test cell 20 was prepared in the same manner as in Example 1 except that the positive electrode active material was prepared using only the first oxide, and the initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, and 35 The capacity retention rate at the cycle was measured. These measurement results are shown in Table 1.
  • Comparative Example 2 A three-electrode test cell 20 was prepared in the same manner as in Example 1 except that the positive electrode active material was prepared using only the second oxide, and the initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, and 35 The capacity retention rate at the cycle was measured. These measurement results are shown in Table 1. In Comparative Example 2, since the initial discharge capacity was low, charging / discharging after the first cycle was not performed.
  • the second oxidation has a high initial charge capacity when charged from the positive electrode potential of 3.0 V (vs. Li / Li + ) to 4.3 V (vs. Li / Li + ).
  • the charge / discharge cycle characteristics were improved as compared with Comparative Example 1. This is presumably because the positive electrode active material having a high initial charge capacity suppressed the negative electrode active material from being overdischarged by giving the negative electrode active material an irreversible capacity at a low potential.
  • Example 1 A three-electrode test cell 20 was produced in the same manner as in Example 1 except that only LiMnO 2 having a BET specific surface area shown in Table 2 was used as the positive electrode active material.
  • Reference Example 2 A three-electrode test cell 20 was prepared in the same manner as in Reference Example 1 except that LiMnO 2 having the BET specific surface area shown in Table 2 was used as the second oxide, and the initial charge capacity, initial discharge capacity, and The initial charge / discharge efficiency was measured. These results are shown in Table 2.
  • Reference Example 3 A three-electrode test cell 20 was prepared in the same manner as in Reference Example 1 except that LiMnO 2 having the BET specific surface area shown in Table 2 was used as the second oxide, and the initial charge capacity, initial discharge capacity, and The initial charge / discharge efficiency was measured. These results are shown in Table 2.
  • Reference Example 5 A three-electrode test cell 20 was prepared in the same manner as in Reference Example 4 except that LiOH, MnO 2 and carbon were mixed at a molar ratio of 1.10: 1.00: 0.375. The capacity, initial discharge capacity, and initial charge / discharge efficiency were measured. These results are shown in Table 3. Also in Reference Example 5, LiMnO 2 having a crystal structure belonging to the space group c2 / m was included in the second oxide.
  • Reference Example 6 A three-electrode test cell 20 was prepared in the same manner as in Reference Example 4 except that LiOH, MnO 2 and carbon were mixed at a molar ratio of 1.20: 1.00: 0.375. The capacity, initial discharge capacity, and initial charge / discharge efficiency were measured. These results are shown in Table 3. Also in Reference Example 6, LiMnO 2 having a crystal structure belonging to the space group c2 / m was included in the second oxide.
  • Reference Example 7 A three-electrode test cell 20 was prepared in the same manner as in Reference Example 4 except that LiOH, MnO 2 and carbon were mixed at a mass molar ratio of 1.30: 1.00: 0.375. The charge capacity, initial discharge capacity, and initial charge / discharge efficiency were measured. These results are shown in Table 3. Also in Reference Example 7, LiMnO 2 having a crystal structure belonging to the space group c2 / m was included in the second oxide.
  • LiMnO 2 having a crystal structure belonging to the space group c2 / m of Reference Examples 4 to 7 is LiMnO having a crystal structure belonging to the space group Pmnm of Example 1 and Example 2.
  • FIG. 2 it can be seen that a large initial charge capacity can be imparted to the three-electrode test cell 20.

Abstract

Provided is a positive-electrode active material of a non-aqueous electrolyte secondary cell that does not require setting a high voltage the first time charging is completed for the non-aqueous electrolyte secondary cell, and is capable of providing excellent charge-discharge-cycle characteristics to the non-aqueous electrolyte secondary cell. This positive-electrode active material of a non-aqueous electrolyte secondary cell (1) a first oxide and a second oxide.

Description

非水電解質二次電池の正極活物質及び非水電解質二次電池Non-aqueous electrolyte secondary battery positive electrode active material and non-aqueous electrolyte secondary battery
　本発明は、非水電解質二次電池の正極活物質及び非水電解質二次電池に関する。 The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte secondary battery.
　近年、電子機器などの電源として非水電解質二次電池が広く用いられるようになってきている。非水電解質二次電池の負極活物質としては、一般に、黒鉛などの炭素材料が使用されている。しかしながら、非水電解質二次電池の電池容量をさらに大きくしたいという要望が高くなってきており、電池容量をさらに大きくし得る、黒鉛に代わる負極活物質の研究が行われている。 In recent years, non-aqueous electrolyte secondary batteries have been widely used as power sources for electronic devices and the like. Generally, a carbon material such as graphite is used as the negative electrode active material of the non-aqueous electrolyte secondary battery. However, there is an increasing demand for further increasing the battery capacity of the nonaqueous electrolyte secondary battery, and research on a negative electrode active material that can replace the graphite and that can further increase the battery capacity has been conducted.
　黒鉛に代わる負極活物質としては、ケイ素などのリチウムと合金化する材料が検討されている。しかしながら、リチウムと合金化する材料からなる負極活物質は、一般に不可逆容量が大きく、充放電サイクルが低下しやすい。 Materials that can be alloyed with lithium such as silicon have been studied as negative electrode active materials that can replace graphite. However, the negative electrode active material made of a material alloyed with lithium generally has a large irreversible capacity, and the charge / discharge cycle is likely to decrease.
　このような問題を解決するために、例えば特許文献１においては、正極活物質として、主成分である第１の含Ｌｉ遷移金属複合酸化物と、副成分である第２の含Ｌｉ遷移金属複合酸化物とを含み、第２の含Ｌｉ遷移金属複合酸化物としてＬｉ（ＬｉｘＭｎ２ｘＣｏ１－３ｘ）Ｏ２（式中、０＜ｘ＜１／３である）を用い、電池の初回の充電終止電圧を高く設定することにより、初回充電時に十分な量の不可逆容量（具体的には、正極活物質に含まれるリチウムイオン）を負極活物質に与え、電池の充放電サイクル特性を向上させることが提案されている。 In order to solve such a problem, for example, in Patent Document 1, as a positive electrode active material, a first Li-containing transition metal composite oxide as a main component and a second Li-containing transition metal composite as a subcomponent are used. And using Li (Li x Mn 2x Co 1-3x ) O 2 (where 0 <x <1/3) as the second Li-containing transition metal composite oxide. By setting the end-of-charge voltage of the battery to a high value, a sufficient amount of irreversible capacity (specifically, lithium ions contained in the positive electrode active material) is given to the negative electrode active material during the initial charge, improving the charge / discharge cycle characteristics of the battery. It has been proposed to let
特開２００９－１５８３２０号公報JP 2009-158320 A
　特許文献１では、負極活物質に不可逆容量を与える際に、電池の初回の充電終止電圧を高くする必要がある。しかしながら、電池の初回の充電終止電圧を高くすると、非水電解質が分解し、電池の充放電サイクル特性が悪化してしまう場合がある。 In Patent Document 1, when an irreversible capacity is given to the negative electrode active material, it is necessary to increase the initial charge end voltage of the battery. However, when the initial charge end voltage of the battery is increased, the nonaqueous electrolyte may be decomposed, and the charge / discharge cycle characteristics of the battery may be deteriorated.
　本発明は、非水電解質二次電池の初回の充電終止電圧を高く設定する必要がなく、非水電解質二次電池に優れた充放電サイクル特性を付与し得る、非水電解質二次電池の正極活物質を提供することを主な目的とする。 The present invention does not require a high initial charge end voltage of a non-aqueous electrolyte secondary battery, and can impart excellent charge / discharge cycle characteristics to the non-aqueous electrolyte secondary battery. The main purpose is to provide active materials.
　本発明の非水電解質二次電池の正極活物質は、第１酸化物と、第２酸化物とを含む。第１酸化物は、一般式：ＬｉＣｏｚＭ１－ｚＯ２［式中、ｚは、０．３＜ｚ≦１であり、Ｍは、Ｎｉ及びＭｎの少なくとも一種である。］で表される化合物からなる。第２酸化物は、第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、非水電解質二次電池の初期充電容量が、第２酸化物の代わりに第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充電容量よりも大きく、かつ、非水電解質二次電池の初期充放電効率が、第２酸化物の代わりに第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充放電効率よりも低いリチウム含有金属酸化物である。 The positive electrode active material of the nonaqueous electrolyte secondary battery of the present invention includes a first oxide and a second oxide. The first oxide has a general formula: LiCo z M 1-z O 2 [wherein z is 0.3 <z ≦ 1 and M is at least one of Ni and Mn. ] It consists of a compound represented by this. The second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the positive electrode potential is 3.0 V (vs. Li / Li + ) To 4.3 V (vs. Li / Li + ), the initial charge capacity of the nonaqueous electrolyte secondary battery is that the first oxide is used as the positive electrode active material instead of the second oxide. The initial charge capacity of the non-aqueous electrolyte secondary battery is larger than the initial charge capacity of the non-aqueous electrolyte secondary battery using the positive electrode, and the first oxide is used as the positive electrode active material instead of the second oxide. The lithium-containing metal oxide is lower than the initial charge / discharge efficiency of the nonaqueous electrolyte secondary battery using the positive electrode.
　本発明の非水電解質二次電池は、上記の正極活物質を含む正極と、負極と、非水電解質と、セパレータとを含む。 The nonaqueous electrolyte secondary battery of the present invention includes a positive electrode including the positive electrode active material, a negative electrode, a nonaqueous electrolyte, and a separator.
　本発明によれば、非水電解質二次電池の初回の充電終止電圧を高く設定する必要がなく、非水電解質二次電池に優れた充放電サイクル特性を付与し得る、非水電解質二次電池の正極活物質を提供することができる。 According to the present invention, it is not necessary to set the initial charge end voltage of the nonaqueous electrolyte secondary battery high, and the nonaqueous electrolyte secondary battery can provide excellent charge / discharge cycle characteristics to the nonaqueous electrolyte secondary battery. The positive electrode active material can be provided.
図１は、本発明の一実施形態における非水電解質二次電池の略図的断面図である。FIG. 1 is a schematic cross-sectional view of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. 図２は、実施例、比較例及び参考例で作製した正極を作用極として用いた三電極式試験用セルの模式図である。FIG. 2 is a schematic diagram of a three-electrode test cell using the positive electrodes prepared in Examples, Comparative Examples and Reference Examples as working electrodes.
　以下、本発明を実施した好ましい形態の一例について説明する。但し、下記の実施形態は、単なる例示である。本発明は、下記の実施形態に何ら限定されない。 Hereinafter, an example of a preferable embodiment in which the present invention is implemented will be described. However, the following embodiment is merely an example. The present invention is not limited to the following embodiments.
　また、実施形態などにおいて参照する図面は、模式的に記載されたものであり、図面に描画された物体の寸法の比率などは、現実の物体の寸法の比率などとは異なる場合がある。具体的な物体の寸法比率などは、以下の説明を参酌して判断されるべきである。 Also, the drawings referred to in the embodiments and the like are schematically described, and the ratio of dimensions of objects drawn in the drawings may be different from the ratio of dimensions of actual objects. The specific dimensional ratio of the object should be determined in consideration of the following description.
　図１に示されるように、非水電解質二次電池１は、電池容器１７を備えている。本実施形態では、電池容器１７は、円筒型である。但し、本発明において、電池容器の形状は、円筒型に限定されない。電池容器の形状は、例えば、扁平形状であってもよい。 As shown in FIG. 1, the nonaqueous electrolyte secondary battery 1 includes a battery container 17. In the present embodiment, the battery case 17 is a cylindrical shape. However, in the present invention, the shape of the battery container is not limited to a cylindrical shape. The shape of the battery container may be, for example, a flat shape.
　電池容器１７内には、非水電解質を含浸した電極体１０が収納されている。 In the battery container 17, an electrode body 10 impregnated with a nonaqueous electrolyte is accommodated.
　非水電解質としては、例えば、公知の非水電解質を用いることができる。非水電解質は、溶質、非水系溶媒などを含む。 As the non-aqueous electrolyte, for example, a known non-aqueous electrolyte can be used. The non-aqueous electrolyte includes a solute, a non-aqueous solvent, and the like.
　非水電解質の溶質としては、例えば、ＬｉＸＦｙ（式中、Ｘは、Ｐ、Ａｓ、Ｓｂ、Ｂ、Ｂｉ、Ａｌ、ＧａまたはＩｎであり、ＸがＰ、ＡｓまたはＳｂのときｙは６であり、ＸがＢ、Ｂｉ、Ａｌ、Ｇａ、またはＩｎのときｙは４である）、リチウムペルフルオロアルキルスルホン酸イミドＬｉＮ（ＣｍＦ２ｍ＋１ＳＯ２）（ＣｎＦ２ｎ＋１ＳＯ２）（式中、ｍ及びｎはそれぞれ独立して１～４の整数である）、リチウムペルフルオロアルキルスルホン酸メチドＬｉＣ（ＣｐＦ２ｐ＋１ＳＯ２）（ＣｑＦ２ｑ＋１ＳＯ２）（ＣｒＦ２ｒ＋１ＳＯ２）（式中、ｐ、ｑ及びｒはそれぞれ独立して１～４の整数である）、ＬｉＣＦ３ＳＯ３、ＬｉＣｌＯ４、Ｌｉ２Ｂ１０Ｃｌ１０、及びＬｉ２Ｂ１２Ｃｌ１２などが挙げられる。溶質としては、これらの中でも、ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＮ（Ｃ２Ｆ５ＳＯ２）２、ＬｉＮ（ＣＦ３ＳＯ２）（Ｃ４Ｆ９ＳＯ２）、ＬｉＣ（ＣＦ３ＳＯ２）３、ＬｉＣ（Ｃ２Ｆ５ＳＯ２）３などが好ましい。 As the solute of the nonaqueous electrolyte, for example, LiXF y (wherein X is P, As, Sb, B, Bi, Al, Ga or In, and y is 6 when X is P, As or Sb) There, X is B, Bi, the y when Al, Ga or in, a 4), lithium perfluoroalkyl sulfonic acid imide LiN (C m F 2m + 1 SO 2) (C n F 2n + 1 SO 2) ( wherein, m and n are each independently an integer of 1-4), lithium perfluoroalkyl sulfonic acid methide LiC (C p F 2p + 1 SO 2) (C q F 2q + 1 SO 2) (C r F 2r + 1 SO 2) ( wherein in, p, q and r are independently an integer of 1 ~ 4), LiCF 3 SO 3, LiClO 4, Li 2 B 10 Cl 10, and Li 2 B 12 Cl 12 and the like elevation It is. Among these, as solutes, LiPF 6 , LiBF 4 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiN (CF 3 SO 2 ) (C 4 F 9 SO 2 ), LiC (CF 3 SO 2 ) 3 , LiC (C 2 F 5 SO 2 ) 3 and the like are preferable.
　非水電解質は、１種類の溶質を含んでいてもよいし、複数種類の溶質を含んでいてもよい。 The nonaqueous electrolyte may contain one type of solute or may contain a plurality of types of solutes.
　非水電解質の非水系溶媒としては、例えば、環状カーボネート、鎖状カーボネートまたは環状カーボネートと鎖状カーボネートとの混合溶媒などが挙げられる。環状カーボネートの具体例としては、例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ビニレンカーボネートなどが挙げられる。鎖状カーボネートの具体例としては、例えば、ジメチルカーボネート、メチルエチルカーボネート、ジエチルカーボネートなどが挙げられる。なかでも、低粘度且つ低融点でリチウムイオン伝導度の高い非水系溶媒として、環状カーボネートと鎖状カーボネートとの混合溶媒が好ましく用いられる。環状カーボネートと鎖状カーボネートとの混合溶媒においては、環状カーボネートと鎖状カーボネートとの混合比（環状カーボネート：鎖状カーボネート）は、体積比で、１：９～５：５の範囲内にあることが好ましい。 Examples of the non-aqueous solvent for the non-aqueous electrolyte include cyclic carbonate, chain carbonate, or a mixed solvent of cyclic carbonate and chain carbonate. Specific examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, and the like. Specific examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate and the like. Of these, a mixed solvent of a cyclic carbonate and a chain carbonate is preferably used as a non-aqueous solvent having a low viscosity, a low melting point, and a high lithium ion conductivity. In the mixed solvent of cyclic carbonate and chain carbonate, the mixing ratio of cyclic carbonate and chain carbonate (cyclic carbonate: chain carbonate) should be in the range of 1: 9 to 5: 5 by volume ratio. Is preferred.
　非水系溶媒は、環状カーボネートと、１，２－ジメタキシエタン、１，２－ジエトキシエタンなどのエーテル系溶媒との混合溶媒であってもよい。 The non-aqueous solvent may be a mixed solvent of a cyclic carbonate and an ether solvent such as 1,2-dimetaxethane and 1,2-diethoxyethane.
　また、非水電解質の非水系溶媒としてイオン性液体を用いることもできる。イオン性液体のカチオン種、アニオン種は、特に限定されない。低粘度、電気化学的安定性、疎水性の観点から、カチオンとしては、例えばピリジニウムカチオン、イミダゾリウムカチオン、４級アンモニウムカチオンが好ましく用いられる。アニオンとしては、例えばフッ素含有イミド系アニオンを含むイオン性液体が好ましく用いられる。 Also, an ionic liquid can be used as a nonaqueous solvent for the nonaqueous electrolyte. The cation species and anion species of the ionic liquid are not particularly limited. From the viewpoint of low viscosity, electrochemical stability, and hydrophobicity, for example, a pyridinium cation, an imidazolium cation, or a quaternary ammonium cation is preferably used as the cation. As the anion, for example, an ionic liquid containing a fluorine-containing imide anion is preferably used.
　また、非水電解質は、ポリエチレンオキシド、ポリアクリロニトリルなどのポリマー電解質に電解液を含浸したゲル状ポリマー電解質、ＬｉＩ、Ｌｉ３Ｎなどの無機固体電解質などであってもよい。 The non-aqueous electrolyte may be a gel polymer electrolyte obtained by impregnating a polymer electrolyte such as polyethylene oxide or polyacrylonitrile with an electrolytic solution, or an inorganic solid electrolyte such as LiI or Li 3 N.
　電極体１０は、負極１１と、正極１２と、負極１１及び正極１２の間に配置されているセパレータ１６とが巻回されてなる。 The electrode body 10 is formed by winding a negative electrode 11, a positive electrode 12, and a separator 16 disposed between the negative electrode 11 and the positive electrode 12.
　セパレータ１６は、負極１１と正極１２との接触による短絡を抑制でき、かつ非水電解質を含浸して、リチウムイオン伝導性が得られるものであれば特に限定されない。セパレータ１６は、例えば、樹脂製の多孔膜により構成することができる。樹脂製の多孔膜の具体例としては、例えば、ポリプロピレン製やポリエチレン製の多孔膜、ポリプロピレン製の多孔膜とポリエチレン製の多孔膜との積層体などが挙げられる。 The separator 16 is not particularly limited as long as it can suppress a short circuit due to contact between the negative electrode 11 and the positive electrode 12 and can impregnate a nonaqueous electrolyte to obtain lithium ion conductivity. For example, the separator 16 can be formed of a resin porous film. Specific examples of the resin porous film include a polypropylene or polyethylene porous film, a laminate of a polypropylene porous film and a polyethylene porous film, and the like.
　負極１１は、負極集電体と、負極集電体の少なくとも一方の表面の上に配された負極活物質層とを有する。負極集電体は、例えば、Ｃｕなどの金属や、Ｃｕなどの金属を含む合金からなる箔により構成することができる。 The negative electrode 11 has a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode current collector can be composed of, for example, a foil made of a metal such as Cu or an alloy containing a metal such as Cu.
　負極活物質層には、負極活物質が含まれる。負極活物質は、リチウムを可逆的に吸蔵・放出できるものであれば特に限定されない。負極活物質としては、例えば、炭素材料、リチウムと合金化する材料、酸化スズなどの金属酸化物などが挙げられる。炭素材料の具体例としては、例えば、天然黒鉛、人造黒鉛、メソフェーズピッチ系炭素繊維（ＭＣＦ）、メソカーボンマイクロビーズ（ＭＣＭＢ）、コークス、ハードカーボン、フラーレン、カーボンナノチューブなどが挙げられる。リチウムと合金化する材料としては、例えば、ケイ素、ゲルマニウム、スズ及びアルミニウムからなる群から選ばれた１種以上の金属、またはケイ素、ゲルマニウム、スズ及びアルミニウムからなる群から選ばれた１種以上の金属を含む合金からなるものが挙げられる。 The negative electrode active material layer contains a negative electrode active material. The negative electrode active material is not particularly limited as long as it can reversibly store and release lithium. Examples of the negative electrode active material include a carbon material, a material alloyed with lithium, and a metal oxide such as tin oxide. Specific examples of the carbon material include natural graphite, artificial graphite, mesophase pitch-based carbon fiber (MCF), mesocarbon microbeads (MCMB), coke, hard carbon, fullerene, and carbon nanotube. Examples of the material to be alloyed with lithium include one or more metals selected from the group consisting of silicon, germanium, tin and aluminum, or one or more types selected from the group consisting of silicon, germanium, tin and aluminum. The thing which consists of an alloy containing a metal is mentioned.
　負極活物質層には、グラファイトなどの公知の炭素導電剤、カルボキシメチルセルロースナトリウム（ＣＭＣ）、スチレンブタジエンゴム（ＳＢＲ）などの公知の結着剤などが含まれていてもよい。 The negative electrode active material layer may contain a known carbon conductive agent such as graphite and a known binder such as sodium carboxymethyl cellulose (CMC) and styrene butadiene rubber (SBR).
　正極１２は、正極集電体と、正極集電体の上に配された正極活物質層とを有する。正極集電体は、例えば、Ａｌなどの金属、Ａｌなどの金属を含む合金により構成することができる。 The positive electrode 12 has a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. The positive electrode current collector can be made of, for example, a metal such as Al or an alloy containing a metal such as Al.
　正極活物質層は、正極活物質を含む。正極活物質層は、正極活物質に加えて、結着剤、導電剤などの適宜の材料を含んでいてもよい。好ましく用いられる結着剤の具体例としては、例えばポリフッ化ビニリデンなどが挙げられる。好ましく用いられる導電剤の具体例としては、例えば、黒鉛、アセチレンブラックなどの炭素材料などが挙げられる。 The positive electrode active material layer includes a positive electrode active material. The positive electrode active material layer may contain appropriate materials such as a binder and a conductive agent in addition to the positive electrode active material. Specific examples of the binder preferably used include, for example, polyvinylidene fluoride. Specific examples of the conductive agent preferably used include carbon materials such as graphite and acetylene black.
　正極活物質は、第１酸化物と第２酸化物とを含む。 The positive electrode active material includes a first oxide and a second oxide.
　第１酸化物は、一般式：ＬｉＣｏｚＭ１－ｚＯ２［式中、ｚは、０．３＜ｚ≦１であり、Ｍは、Ｎｉ及びＭｎの少なくとも一種である。］で表される化合物からなる。第１酸化物は、空間群Ｒ－３ｍに帰属される結晶構造を有することが好ましい。第１酸化物は、コバルト酸リチウム（ＬｉＣｏＯ２）であることが好ましい。コバルト酸リチウムは、層状構造を有することが好ましい。 The first oxide has a general formula: LiCo z M 1-z O 2 [wherein z is 0.3 <z ≦ 1 and M is at least one of Ni and Mn. ] It consists of a compound represented by this. The first oxide preferably has a crystal structure belonging to the space group R-3m. The first oxide is preferably lithium cobalt oxide (LiCoO 2 ). The lithium cobalt oxide preferably has a layered structure.
　第１酸化物は、正極活物質中に６０質量％～９５質量％程度含まれることが好ましく、７０質量％～９０質量％程度含まれることがより好ましい。 The first oxide is preferably contained in the positive electrode active material by about 60% by mass to 95% by mass, and more preferably by about 70% by mass to 90% by mass.
　第２酸化物は、第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、非水電解質二次電池の初期充電容量が、第２酸化物の代わりに第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充電容量よりも大きく、かつ、非水電解質二次電池の初期充放電効率が、第２酸化物の代わりに第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充放電効率よりも低い、リチウム含有金属酸化物である。より詳細には、第２酸化物は、第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、この非水電解質二次電池の初期充電容量が、第２酸化物の代わりに第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充電容量よりも大きく、かつ、第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、この非水電解質二次電池の初期充放電効率が、第２酸化物の代わりに第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充放電効率よりも低い、リチウム含有金属酸化物である。 The second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the positive electrode potential is 3.0 V (vs. Li / Li + ) To 4.3 V (vs. Li / Li + ), the initial charge capacity of the nonaqueous electrolyte secondary battery is that the first oxide is used as the positive electrode active material instead of the second oxide. The initial charge capacity of the non-aqueous electrolyte secondary battery is larger than the initial charge capacity of the non-aqueous electrolyte secondary battery using the positive electrode, and the first oxide is used as the positive electrode active material instead of the second oxide. It is a lithium-containing metal oxide that is lower than the initial charge / discharge efficiency of a non-aqueous electrolyte secondary battery using a positive electrode. More specifically, the second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the potential of the positive electrode is 3.0 V (vs. when charging .Li / from Li +) until 4.3V (vs.Li/Li +), the initial charge capacity of the non-aqueous electrolyte secondary battery, the first oxide in place of the second oxide Non-aqueous using a positive electrode with a positive electrode active material that is larger than the initial charge capacity of a non-aqueous electrolyte secondary battery using a positive electrode with a positive electrode as a positive electrode active material, and a negative electrode made of lithium metal When the electrolyte secondary battery is charged until the potential of the positive electrode is changed from 3.0 V (vs. Li / Li + ) to 4.3 V (vs. Li / Li + ), the initial state of the non-aqueous electrolyte secondary battery is The charge / discharge efficiency is positive when the first oxide is used as the positive electrode active material instead of the second oxide. Aqueous lower than the initial charge-discharge efficiency of electrolyte secondary battery using a lithium-containing metal oxide.
　第２酸化物は、第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、非水電解質二次電池の初期充電容量が、１７０ｍＡｈ／ｇを超え、かつ、非水電解質二次電池の初期充放電効率が、７０％未満となる、リチウム含有金属酸化物であることが好ましい。この初期充電容量は、１８０ｍＡｈ／ｇを超えることがより好ましい。また、この初期充放電効率は、６０％未満であることがより好ましい。第２酸化物の表面積は、ＢＥＴ比表面積で３ｍ２／ｇを超えることが好ましく、７ｍ２／ｇを超えることが好ましい。第２酸化物の表面積は、ＢＥＴ比表面積で、通常５０ｍ２／ｇを超えない。 The second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the positive electrode potential is 3.0 V (vs. Li / Li + ) To 4.3 V (vs. Li / Li + ), the initial charge capacity of the nonaqueous electrolyte secondary battery exceeds 170 mAh / g, and the initial charge of the nonaqueous electrolyte secondary battery is A lithium-containing metal oxide that has a discharge efficiency of less than 70% is preferable. The initial charge capacity is more preferably over 180 mAh / g. The initial charge / discharge efficiency is more preferably less than 60%. The surface area of the second oxide is preferably greater than 3 m 2 / g and more preferably greater than 7 m 2 / g in terms of BET specific surface area. The surface area of the second oxide is a BET specific surface area and usually does not exceed 50 m 2 / g.
　第２酸化物は、正極活物質中に５質量％～４０質量％程度含まれることが好ましく、１０質量％～３０質量％程度含まれることがより好ましい。 The second oxide is preferably contained in the positive electrode active material by about 5% by mass to 40% by mass, and more preferably by about 10% by mass to 30% by mass.
　第２酸化物は、リチウム含有マンガン酸化物であることが好ましく、マンガン酸リチウム（ＬｉＭｎＯ２）であることがより好ましい。ＬｉＭｎＯ２は、空間群ｃ２／ｍに帰属される結晶構造または空間群Ｐｍｎｍに帰属される結晶構造を有することが好ましい。 The second oxide is preferably a lithium-containing manganese oxide, and more preferably lithium manganate (LiMnO 2 ). LiMnO 2 preferably has a crystal structure belonging to the space group c2 / m or a crystal structure belonging to the space group Pmnm.
　上述の通り、ケイ素などのリチウムと合金化する材料からなる負極活物質は、一般に不可逆容量が大きく、充放電サイクルが低下しやすいという問題がある。このような問題を解決するために、例えば特許文献１のように、負極活物質に不可逆容量を与えることが考えられる。しかしながら、特許文献１の方法では、負極活物質に不可逆容量を与える際に、電池の初回の充電終止電圧を高くする必要がある。電池の初回の充電終止電圧を高くすると、非水電解質が分解し、電池の充放電サイクル特性が悪化してしまう場合がある。 As described above, the negative electrode active material made of a material that is alloyed with lithium such as silicon generally has a problem that the irreversible capacity is large and the charge / discharge cycle tends to decrease. In order to solve such a problem, it is conceivable to give an irreversible capacity to the negative electrode active material as in Patent Document 1, for example. However, in the method of Patent Document 1, it is necessary to increase the initial charge end voltage of the battery when providing the irreversible capacity to the negative electrode active material. If the initial charge end voltage of the battery is increased, the nonaqueous electrolyte may be decomposed, and the charge / discharge cycle characteristics of the battery may deteriorate.
　これに対して、本実施形態に係る正極活物質は、上記の第１酸化物と第２酸化物を含む。本実施形態に係る正極活物質によれば、非水電解質二次電池１の初回の充電終止電圧を高く設定する必要がなく、非水電解質二次電池１に優れた充放電サイクル特性を付与し得る。この理由は、次のように考えることができる。すなわち、本実施形態に係る正極活物質の第２酸化物は、第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、非水電解質二次電池の初期充放電効率が、第２酸化物の代わりに第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充放電効率よりも低いリチウム含有金属酸化物からなる。このため、非水電解質二次電池１の初期充放電過程において、正極活物質から負極活物質に十分な量の不可逆容量を与えることができ、負極活物質が過放電状態になることを抑制することができる。 On the other hand, the positive electrode active material according to the present embodiment includes the first oxide and the second oxide. According to the positive electrode active material according to the present embodiment, it is not necessary to set the initial charge end voltage of the nonaqueous electrolyte secondary battery 1 high, and excellent charge / discharge cycle characteristics are imparted to the nonaqueous electrolyte secondary battery 1. obtain. The reason for this can be considered as follows. That is, the second oxide of the positive electrode active material according to the present embodiment is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the potential of the positive electrode. Is charged from 3.0 V (vs. Li / Li + ) to 4.3 V (vs. Li / Li + ), the initial charge / discharge efficiency of the nonaqueous electrolyte secondary battery is Instead, it comprises a lithium-containing metal oxide that is lower than the initial charge / discharge efficiency of the nonaqueous electrolyte secondary battery using the positive electrode using the first oxide as the positive electrode active material. For this reason, in the initial charge / discharge process of the nonaqueous electrolyte secondary battery 1, a sufficient amount of irreversible capacity can be given from the positive electrode active material to the negative electrode active material, and the negative electrode active material is prevented from being overdischarged. be able to.
　さらに、第２酸化物を構成するリチウム含有金属酸化物は、第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、非水電解質二次電池の初期充電容量が、第２酸化物の代わりに第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充電容量よりも大きい。このため、非水電解質二次電池１の初期充電容量が低下することを抑制しつつ、初期充放電過程において、負極活物質に十分な量の不可逆容量を与えることができる。 Further, the lithium-containing metal oxide constituting the second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal. When charging from 3.0 V (vs. Li / Li + ) to 4.3 V (vs. Li / Li + ), the initial charge capacity of the non-aqueous electrolyte secondary battery is replaced with the second oxide. The initial charge capacity of the nonaqueous electrolyte secondary battery using the positive electrode using the first oxide as the positive electrode active material is larger. For this reason, it is possible to give a sufficient amount of irreversible capacity to the negative electrode active material in the initial charge / discharge process while suppressing a decrease in the initial charge capacity of the nonaqueous electrolyte secondary battery 1.
　以上のように、本実施形態に係る正極活物質では、上記の第１酸化物に加えて、第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、非水電解質二次電池の初期充放電効率が、第２酸化物の代わりに第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充放電効率よりも低いリチウム含有金属酸化物からなる第２酸化物を含むことにより、非水電解質二次電池１の初回充電時において、充電終止電圧を低く設定しても、負極活物質に十分な量の不可逆容量を与えることができ、負極活物質が過放電状態になりにくくすることができる。特に、負極活物質がリチウムと合金化する材料である場合、充放電サイクルが低下しやすいが、本実施形態に係る正極活物質を用いることにより、非水電解質二次電池１の充電終止電圧を高く設定せずに、非水電解質二次電池１に優れた充放電サイクル特性を付与し得る。 As described above, in the positive electrode active material according to this embodiment, in addition to the first oxide, a nonaqueous electrolyte using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal. When the secondary battery is charged until the positive electrode potential changes from 3.0 V (vs. Li / Li + ) to 4.3 V (vs. Li / Li + ), the initial charge / discharge of the nonaqueous electrolyte secondary battery A second oxide composed of a lithium-containing metal oxide whose efficiency is lower than the initial charge / discharge efficiency of a nonaqueous electrolyte secondary battery using a positive electrode in which the first oxide is used as the positive electrode active material instead of the second oxide. By including the negative electrode active material, a sufficient amount of irreversible capacity can be imparted to the negative electrode active material even when the end-of-charge voltage is set low when the nonaqueous electrolyte secondary battery 1 is initially charged. Can be made difficult. In particular, when the negative electrode active material is a material that is alloyed with lithium, the charge / discharge cycle is likely to be reduced. Without setting it high, the non-aqueous electrolyte secondary battery 1 can be provided with excellent charge / discharge cycle characteristics.
　第２酸化物が、第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、非水電解質二次電池の初期充電容量が、１７０ｍＡｈ／ｇを超え、かつ、非水電解質二次電池の初期充放電効率が、７０％未満となるリチウム含有金属酸化物である場合、非水電解質二次電池１の初回の充電終止電圧をより低く設定しても、正極活物質から負極活物質に十分な量の不可逆容量を与えることができる。 The non-aqueous electrolyte secondary battery in which the second oxide is a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal has a positive electrode potential of 3.0 V (vs. Li / Li + ) To 4.3 V (vs. Li / Li + ), the initial charge capacity of the nonaqueous electrolyte secondary battery exceeds 170 mAh / g, and the initial charge of the nonaqueous electrolyte secondary battery is When the discharge efficiency is a lithium-containing metal oxide that is less than 70%, a sufficient amount from the positive electrode active material to the negative electrode active material even if the initial charge end voltage of the nonaqueous electrolyte secondary battery 1 is set lower. Of irreversible capacity.
　第２酸化物の表面積が、ＢＥＴ比表面積で３ｍ２／ｇを超える場合、正極活物質中の第２酸化物の量を少なくしても負極活物質に十分な量の不可逆容量を与えることができ、非水電解質二次電池１の充放電サイクルを向上させることができる。 When the surface area of the second oxide exceeds 3 m 2 / g in terms of the BET specific surface area, a sufficient amount of irreversible capacity can be imparted to the negative electrode active material even if the amount of the second oxide in the positive electrode active material is reduced. The charge / discharge cycle of the non-aqueous electrolyte secondary battery 1 can be improved.
　非水電解質二次電池１では、本実施形態に係る正極活物質を用いることにより、正極の充電終止電位を４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）以下としても、負極活物質に十分な量の不可逆容量を与えることができる。 In the nonaqueous electrolyte secondary battery 1, by using the positive electrode active material according to the present embodiment, a sufficient amount for the negative electrode active material even when the charge end potential of the positive electrode is 4.3 V (vs. Li / Li + ) or less. Of irreversible capacity.
　以下、本発明について、具体的な実施例に基づいて、さらに詳細に説明する。但し、本発明は、以下の実施例に何ら限定されるものではなく、その要旨を変更しない範囲において適宜変更して実施することが可能である。 Hereinafter, the present invention will be described in more detail based on specific examples. However, the present invention is not limited to the following examples, and can be appropriately modified and implemented without departing from the scope of the invention.
　（実施例１）
　［正極活物質］
　〈第１酸化物〉
　所定量のＬｉ２ＣＯ３とＣｏ３Ｏ４とを混合し、空気中において９００℃で１０時間保持することによって、第１酸化物としてＬｉＣｏＯ２を得た。得られたＬｉＣｏＯ２をＸ線回折法で分析したところ、ＬｉＣｏＯ２は、層状構造を有していた。また、ＬｉＣｏＯ２は、空間群Ｒ－３ｍに帰属される結晶構造を有していた。 Example 1
[Positive electrode active material]
<First oxide>
A predetermined amount of Li 2 CO 3 and Co 3 O 4 were mixed and held in air at 900 ° C. for 10 hours to obtain LiCoO 2 as the first oxide. When the obtained LiCoO 2 was analyzed by an X-ray diffraction method, the LiCoO 2 had a layered structure. LiCoO 2 had a crystal structure belonging to the space group R-3m.
　〈第２酸化物〉
　所定量のＭｎ２Ｏ３とＬｉＯＨとを混合し、窒素ガス雰囲気中６００℃で５時間焼成し、第２酸化物としてＬｉＭｎＯ２を得た。得られたＬｉＭｎＯ２の表面積は、ＢＥＴ比表面積で１３ｍ２／ｇ，平均粒子径は、ｄ５０で１３μｍであった。ＬｉＭｎＯ２をＸ線回折法で分析したところ、ＬｉＭｎＯ２は空間群Ｐｍｎｍに帰属される結晶構造を有していた。ＬｉＭｎＯ２の２４．６°におけるピーク強度Ｉａと、１５．３°におけるピーク強度Ｉｂとの比（Ｉａ／Ｉｂ）は、０．３７であった。また、ＬｉＭｎＯ２の４５．０°におけるピーク強度Ｉｃと、１５．３°におけるピーク強度Ｉｂとの比（Ｉｃ／Ｉｂ）は、０．９９であった。 <Second oxide>
A predetermined amount of Mn 2 O 3 and LiOH were mixed and fired at 600 ° C. for 5 hours in a nitrogen gas atmosphere to obtain LiMnO 2 as a second oxide. The obtained LiMnO 2 had a BET specific surface area of 13 m 2 / g and an average particle size of 13 μm in d50. When LiMnO 2 was analyzed by X-ray diffraction, LiMnO 2 had a crystal structure belonging to the space group Pmnm. The ratio (Ia / Ib) between the peak intensity Ia at 24.6 ° and the peak intensity Ib at 15.3 ° of LiMnO 2 was 0.37. The ratio (Ic / Ib) of the peak intensity Ic at 45.0 ° to the peak intensity Ib at 15.3 ° of LiMnO 2 was 0.99.
　第１酸化物と第２酸化物とを第１酸化物：第２酸化物＝９０：１０の質量比で混合して、正極活物質を作製した。得られた正極活物質と、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９０：５：５となるように混合した。次に、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正極集電体に塗布し、１１０℃で真空乾燥することで、正極を作製した。 The first oxide and the second oxide were mixed at a mass ratio of first oxide: second oxide = 90: 10 to prepare a positive electrode active material. The obtained positive electrode active material, acetylene black as a conductive agent, and polyvinylidene fluoride as a binder were mixed at a mass ratio of 90: 5: 5. Next, N-methyl-2-pyrrolidone was added to this mixture to prepare a positive electrode mixture slurry. The obtained positive electrode mixture slurry was applied to a positive electrode current collector made of an aluminum foil and vacuum-dried at 110 ° C. to produce a positive electrode.
　次に、図２に示されるような三電極式試験用セル２０を作製した。アルゴン雰囲気下で、作用極２１として、上記の正極を用いた。対極２２及び参照極２３として、リチウム金属を用いた。セパレータとして、ポリエチレン製セパレーターを用いた。非水電解質２４として、エチレンカーボネートとジエチルカーボネートとを体積比が３：７となるように混合した非水系溶媒に、ＬｉＰＦ６を１．０ｍｏｌ／ｌの濃度になるように溶解させたものを用いた。なお、作用極２１、対極２２及び参照極２３には、それぞれ集電タブを取り付けた。 Next, a three-electrode test cell 20 as shown in FIG. 2 was produced. The above positive electrode was used as the working electrode 21 in an argon atmosphere. Lithium metal was used as the counter electrode 22 and the reference electrode 23. A polyethylene separator was used as the separator. As the non-aqueous electrolyte 24, a solution obtained by dissolving LiPF 6 to a concentration of 1.0 mol / l in a non-aqueous solvent in which ethylene carbonate and diethyl carbonate are mixed so as to have a volume ratio of 3: 7 is used. It was. A current collecting tab was attached to each of the working electrode 21, the counter electrode 22, and the reference electrode 23.
　［充放電試験］
　三電極式試験用セル２０について、２０ｍＡ／ｇの定電流で正極の電位が４．３Ｖ（vs. Ｌｉ／Ｌｉ＋）に達するまで充電し、その後、４．３Ｖ（vs. Ｌｉ／Ｌｉ＋）の定電圧で電流値が５ｍＡ／ｇに達するまで充電した。その後、２０ｍＡ／ｇの定電流で正極の電位が３．０Ｖ（vs. Ｌｉ／Ｌｉ＋）に達するまで放電を行った。この充放電をさらに３４サイクル行った。このときの初期充電容量、初期放電容量、初期充放電効率及び３５サイクル目の容量維持率を表１に示す。 [Charge / discharge test]
The three-electrode test cell 20 is charged at a constant current of 20 mA / g until the positive electrode potential reaches 4.3 V (vs. Li / Li + ), and then 4.3 V (vs. Li / Li + ). The battery was charged until the current value reached 5 mA / g at a constant voltage. Thereafter, discharging was performed at a constant current of 20 mA / g until the positive electrode potential reached 3.0 V (vs. Li / Li + ). This charge and discharge was further performed for 34 cycles. Table 1 shows the initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, and capacity retention rate at the 35th cycle at this time.
　（実施例２）
　第１酸化物と第２酸化物とを第１酸化物：第２酸化物＝８０：２０の質量比で混合して、正極活物質を作製したこと以外は、実施例１と同様にして三電極式試験用セル２０を作製し、初期充電容量、初期放電容量、初期充放電効率及び３５サイクル目の容量維持率を測定した。これらの測定結果を表１に示す。 (Example 2)
The first oxide and the second oxide were mixed at a mass ratio of first oxide: second oxide = 80: 20 to produce a positive electrode active material. An electrode-type test cell 20 was produced, and the initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, and capacity maintenance ratio at the 35th cycle were measured. These measurement results are shown in Table 1.
　（比較例１）
　第１酸化物のみを用いて正極活物質を作製したこと以外は、実施例１と同様にして三電極式試験用セル２０を作製し、初期充電容量、初期放電容量、初期充放電効率及び３５サイクル目の容量維持率を測定した。これらの測定結果を表１に示す。 (Comparative Example 1)
A three-electrode test cell 20 was prepared in the same manner as in Example 1 except that the positive electrode active material was prepared using only the first oxide, and the initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, and 35 The capacity retention rate at the cycle was measured. These measurement results are shown in Table 1.
　（比較例２）
　第２酸化物のみを用いて正極活物質を作製したこと以外は、実施例１と同様にして三電極式試験用セル２０を作製し、初期充電容量、初期放電容量、初期充放電効率及び３５サイクル目の容量維持率を測定した。これらの測定結果を表１に示す。なお、比較例２では、初期放電容量が低かったため、１サイクル目以降の充放電は行わなかった。 (Comparative Example 2)
A three-electrode test cell 20 was prepared in the same manner as in Example 1 except that the positive electrode active material was prepared using only the second oxide, and the initial charge capacity, initial discharge capacity, initial charge / discharge efficiency, and 35 The capacity retention rate at the cycle was measured. These measurement results are shown in Table 1. In Comparative Example 2, since the initial discharge capacity was low, charging / discharging after the first cycle was not performed.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示されるように、正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときの初期充電容量が高い第２酸化物（比較例２を参照）を第１酸化物に混合した実施例１及び実施例２では、比較例１に比して充放電サイクル特性が向上した。これは、初期充電容量の高い正極活物質が、低い電位で負極活物質に不可逆容量を与えることで、負極活物質が過放電状態になることを抑制したためであると考えられる。 As shown in Table 1, the second oxidation has a high initial charge capacity when charged from the positive electrode potential of 3.0 V (vs. Li / Li + ) to 4.3 V (vs. Li / Li + ). In Example 1 and Example 2 in which the product (see Comparative Example 2) was mixed with the first oxide, the charge / discharge cycle characteristics were improved as compared with Comparative Example 1. This is presumably because the positive electrode active material having a high initial charge capacity suppressed the negative electrode active material from being overdischarged by giving the negative electrode active material an irreversible capacity at a low potential.
　（参考例１）
　表２に示されるＢＥＴ比表面積を有するＬｉＭｎＯ２のみを正極活物質としたこと以外は、実施例１と同様にして三電極式試験用セル２０を作製した。 (Reference Example 1)
A three-electrode test cell 20 was produced in the same manner as in Example 1 except that only LiMnO 2 having a BET specific surface area shown in Table 2 was used as the positive electrode active material.
　［初期充放電試験］
　参考例１で得られた三電極式試験用セル２０について、２０ｍＡ／ｇの定電流で正極の電位が４．５Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）に達するまで充電し、その後、４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）の定電圧で電流値が５ｍＡ／ｇに達するまで充電した。その後、２０ｍＡ／ｇの定電流で正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）に達するまで放電を行った。このときの初期充電容量、初期放電容量及び初期充放電効率を表２に示す。 [Initial charge / discharge test]
The three-electrode test cell 20 obtained in Reference Example 1 was charged with a constant current of 20 mA / g until the positive electrode potential reached 4.5 V (vs. Li / Li + ), and then 4.3 V ( (vs. Li / Li + )) The battery was charged until the current value reached 5 mA / g. Thereafter, discharging was performed at a constant current of 20 mA / g until the potential of the positive electrode reached 3.0 V (vs. Li / Li + ). Table 2 shows the initial charge capacity, initial discharge capacity, and initial charge / discharge efficiency at this time.
　（参考例２）
　表２に示されるＢＥＴ比表面積を有するＬｉＭｎＯ２を第２酸化物として用いたこと以外は、参考例１と同様にして三電極式試験用セル２０を作製し、初期充電容量、初期放電容量及び初期充放電効率を測定した。これらの結果を表２に示す。 (Reference Example 2)
A three-electrode test cell 20 was prepared in the same manner as in Reference Example 1 except that LiMnO 2 having the BET specific surface area shown in Table 2 was used as the second oxide, and the initial charge capacity, initial discharge capacity, and The initial charge / discharge efficiency was measured. These results are shown in Table 2.
　（参考例３）
　表２に示されるＢＥＴ比表面積を有するＬｉＭｎＯ２を第２酸化物として用いたこと以外は、参考例１と同様にして三電極式試験用セル２０を作製し、初期充電容量、初期放電容量及び初期充放電効率を測定した。これらの結果を表２に示す。 (Reference Example 3)
A three-electrode test cell 20 was prepared in the same manner as in Reference Example 1 except that LiMnO 2 having the BET specific surface area shown in Table 2 was used as the second oxide, and the initial charge capacity, initial discharge capacity, and The initial charge / discharge efficiency was measured. These results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２に示されるように、ＢＥＴ比表面積が大きい第２酸化物を用いた参考例１及び参考例２では、三電極式試験用セル２０の初期充電容量が高く、負極活物質に不可逆容量を効率よく与えることができることが分かる。参考例３のように、第２酸化物のＢＥＴ比表面積が小さい場合、三電極式試験用セル２０の初期充電容量が小さくなることが分かる。 As shown in Table 2, in Reference Example 1 and Reference Example 2 using the second oxide having a large BET specific surface area, the initial charge capacity of the three-electrode test cell 20 is high, and the irreversible capacity is added to the negative electrode active material. It turns out that it can give efficiently. As in Reference Example 3, it can be seen that when the BET specific surface area of the second oxide is small, the initial charge capacity of the three-electrode test cell 20 is small.
　（参考例４）
　ＬｉＯＨとＭｎＯ２と炭素とを、１．００：１．００：０．３７５のモル比で混合し、アルゴン雰囲気中、４２５℃で５時間焼成した。得られた材料をＸ線回折法で分析したところ、空間群ｃ２／ｍで帰属される結晶構造を有するＬｉＭｎＯ２が含まれることが分かった。参考例４で得られた材料のみを第２酸化物として用い、第１酸化物を用いなかったこと以外は、実施例１と同様にして三電極式試験用セル２０を作製し、初期充電容量、初期放電容量及び初期充放電効率を測定した。これらの結果を表３示す。 (Reference Example 4)
LiOH, MnO 2 and carbon were mixed at a molar ratio of 1.00: 1.00: 0.375, and fired at 425 ° C. for 5 hours in an argon atmosphere. When the obtained material was analyzed by the X-ray diffraction method, it was found that LiMnO 2 having a crystal structure belonging to the space group c2 / m was contained. A three-electrode test cell 20 was prepared in the same manner as in Example 1 except that only the material obtained in Reference Example 4 was used as the second oxide and the first oxide was not used. The initial discharge capacity and the initial charge / discharge efficiency were measured. Table 3 shows these results.
　（参考例５）
　ＬｉＯＨとＭｎＯ２と炭素とを、１．１０：１．００：０．３７５のモル比で混合したこと以外は、参考例４と同様にして三電極式試験用セル２０を作製し、初期充電容量、初期放電容量及び初期充放電効率を測定した。これらの結果を表３に示す。なお、参考例５においても、空間群ｃ２／ｍで帰属される結晶構造を有するＬｉＭｎＯ２が第２酸化物に含まれていた。 (Reference Example 5)
A three-electrode test cell 20 was prepared in the same manner as in Reference Example 4 except that LiOH, MnO 2 and carbon were mixed at a molar ratio of 1.10: 1.00: 0.375. The capacity, initial discharge capacity, and initial charge / discharge efficiency were measured. These results are shown in Table 3. Also in Reference Example 5, LiMnO 2 having a crystal structure belonging to the space group c2 / m was included in the second oxide.
　（参考例６）
　ＬｉＯＨとＭｎＯ２と炭素とを、１．２０：１．００：０．３７５のモル比で混合したこと以外は、参考例４と同様にして三電極式試験用セル２０を作製し、初期充電容量、初期放電容量及び初期充放電効率を測定した。これらの結果を表３に示す。なお、参考例６においても、空間群ｃ２／ｍで帰属される結晶構造を有するＬｉＭｎＯ２が第２酸化物に含まれていた。 (Reference Example 6)
A three-electrode test cell 20 was prepared in the same manner as in Reference Example 4 except that LiOH, MnO 2 and carbon were mixed at a molar ratio of 1.20: 1.00: 0.375. The capacity, initial discharge capacity, and initial charge / discharge efficiency were measured. These results are shown in Table 3. Also in Reference Example 6, LiMnO 2 having a crystal structure belonging to the space group c2 / m was included in the second oxide.
　（参考例７）
　ＬｉＯＨとＭｎＯ２と炭素とを、１．３０：１．００：０．３７５の質量モル比で混合したこと以外は、参考例４と同様にして三電極式試験用セル２０を作製し、初期充電容量、初期放電容量及び初期充放電効率を測定した。これらの結果を表３に示す。なお、参考例７においても、空間群ｃ２／ｍで帰属される結晶構造を有するＬｉＭｎＯ２が第２酸化物に含まれていた。 (Reference Example 7)
A three-electrode test cell 20 was prepared in the same manner as in Reference Example 4 except that LiOH, MnO 2 and carbon were mixed at a mass molar ratio of 1.30: 1.00: 0.375. The charge capacity, initial discharge capacity, and initial charge / discharge efficiency were measured. These results are shown in Table 3. Also in Reference Example 7, LiMnO 2 having a crystal structure belonging to the space group c2 / m was included in the second oxide.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　表３に示されるように、参考例４～７の空間群ｃ２／ｍで帰属される結晶構造を有するＬｉＭｎＯ２は、実施例１及び実施例２の空間群Ｐｍｎｍで帰属される結晶構造のＬｉＭｎＯ２と同様に、三電極式試験用セル２０に大きな初期充電容量を付与することができることが分かる。 As shown in Table 3, LiMnO 2 having a crystal structure belonging to the space group c2 / m of Reference Examples 4 to 7 is LiMnO having a crystal structure belonging to the space group Pmnm of Example 1 and Example 2. Like FIG. 2 , it can be seen that a large initial charge capacity can be imparted to the three-electrode test cell 20.
１…非水電解質二次電池
１０…電極体
１１…負極
１２…正極
１６…セパレータ
１７…電池容器
２０…三電極式試験用セル
２１…作用極
２２…対極
２３…参照極
２４…非水電解質 DESCRIPTION OF SYMBOLS 1 ... Nonaqueous electrolyte secondary battery 10 ... Electrode body 11 ... Negative electrode 12 ... Positive electrode 16 ... Separator 17 ... Battery container 20 ... Three-electrode type test cell 21 ... Working electrode 22 ... Counter electrode 23 ... Reference electrode 24 ... Nonaqueous electrolyte

Claims (10)

  1. 　第１酸化物と第２酸化物とを含み、
    　前記第１酸化物は、一般式：ＬｉＣｏｚＭ１－ｚＯ２［式中、ｚは、０．３＜ｚ≦１であり、Ｍは、Ｎｉ及びＭｎの少なくとも一種である。］で表される化合物からなり、
    　前記第２酸化物は、前記第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、前記正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、前記非水電解質二次電池の初期充電容量が、前記第２酸化物の代わりに前記第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充電容量よりも大きく、かつ、前記非水電解質二次電池の初期充放電効率が、前記第２酸化物の代わりに前記第１酸化物を正極活物質とした正極を用いた非水電解質二次電池の初期充放電効率よりも低いリチウム含有金属酸化物である、非水電解質二次電池の正極活物質。     Including a first oxide and a second oxide;
    The first oxide has a general formula: LiCo z M 1-z O 2 [wherein z is 0.3 <z ≦ 1 and M is at least one of Ni and Mn. And a compound represented by
    The second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the positive electrode has a potential of 3.0 V (vs. Li). / from Li +) when charged to a 4.3V (vs.Li/Li +), the initial charge capacity of the nonaqueous electrolyte secondary battery, wherein the first oxide instead of the second oxide Greater than the initial charge capacity of a non-aqueous electrolyte secondary battery using a positive electrode with a positive electrode active material, and the initial charge / discharge efficiency of the non-aqueous electrolyte secondary battery is the second oxide instead of the second oxide. A positive electrode active material for a non-aqueous electrolyte secondary battery, which is a lithium-containing metal oxide that is lower than the initial charge / discharge efficiency of a non-aqueous electrolyte secondary battery using a positive electrode using 1 oxide as a positive electrode active material.
  2. 　前記第２酸化物は、前記第２酸化物を正極活物質とした正極と、リチウム金属からなる負極とを用いた非水電解質二次電池を、前記正極の電位が３．０Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）から４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）になるまで充電したときに、前記非水電解質二次電池の初期充電容量が、１７０ｍＡｈ／ｇを超え、かつ、前記非水電解質二次電池の初期充放電効率が、７０％未満となるリチウム含有金属酸化物である、請求項１に記載の非水電解質二次電池の正極活物質。 The second oxide is a non-aqueous electrolyte secondary battery using a positive electrode using the second oxide as a positive electrode active material and a negative electrode made of lithium metal, and the positive electrode has a potential of 3.0 V (vs. Li). / from Li +) when charged to a 4.3V (vs.Li/Li +), the initial charge capacity of the nonaqueous electrolyte secondary battery, exceed 170 mAh / g, and the nonaqueous electrolyte secondary The positive electrode active material of the nonaqueous electrolyte secondary battery according to claim 1, wherein the secondary battery is a lithium-containing metal oxide having an initial charge / discharge efficiency of less than 70%.
  3. 　前記第２酸化物の表面積が、ＢＥＴ比表面積で３ｍ２／ｇを超える、請求項１または２に記載の非水電解質二次電池の正極活物質。 The positive electrode active material of the nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein the surface area of the second oxide exceeds 3 m 2 / g in terms of a BET specific surface area.
  4. 　前記第２酸化物が、５質量％～４０質量％含まれる、請求項１～３のいずれか一項に記載の非水電解質二次電池の正極活物質。 The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the second oxide is contained in an amount of 5% by mass to 40% by mass.
  5. 　前記第２酸化物は、リチウム含有マンガン酸化物である、請求項１～４のいずれか一項に記載の非水電解質二次電池の正極活物質。 The non-aqueous electrolyte secondary battery positive electrode active material according to any one of claims 1 to 4, wherein the second oxide is a lithium-containing manganese oxide.
  6. 　前記第２酸化物は、ＬｉＭｎＯ２である、請求項１～５のいずれか一項に記載の非水電解質二次電池の正極活物質。 The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 5, wherein the second oxide is LiMnO 2 .
  7. 　前記ＬｉＭｎＯ２が、空間群ｃ２／ｍまたは空間群Ｐｍｎｍに帰属される結晶構造を有する、請求項６に記載の非水電解質二次電池の正極活物質。 The positive electrode active material of the nonaqueous electrolyte secondary battery according to claim 6, wherein the LiMnO 2 has a crystal structure belonging to the space group c2 / m or the space group Pmnm.
  8. 　請求項１～７のいずれか一項に記載の正極活物質を含む正極と、負極と、非水電解質と、セパレータとを含む、非水電解質二次電池。 A nonaqueous electrolyte secondary battery comprising a positive electrode comprising the positive electrode active material according to any one of claims 1 to 7, a negative electrode, a nonaqueous electrolyte, and a separator.
  9. 　前記負極は、負極活物質と負極集電体とを含み、
    　前記負極活物質がリチウムと合金化する材料である、請求項８に記載の非水電解質二次電池。     The negative electrode includes a negative electrode active material and a negative electrode current collector,
    The nonaqueous electrolyte secondary battery according to claim 8, wherein the negative electrode active material is a material alloyed with lithium.
  10. 　前記正極の充電終止電位が、４．３Ｖ（ｖｓ．Ｌｉ／Ｌｉ＋）以下である、請求項８に記載の非水電解質二次電池。 The nonaqueous electrolyte secondary battery according to claim 8, wherein a charge end potential of the positive electrode is 4.3 V (vs. Li / Li + ) or less.
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