WO2018025795A1 - Positive electrode active material for nonaqueous electrolyte secondary batteries, positive electrode using said positive electrode active material, and secondary battery - Google Patents

Positive electrode active material for nonaqueous electrolyte secondary batteries, positive electrode using said positive electrode active material, and secondary battery Download PDF

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Publication number
WO2018025795A1
WO2018025795A1 PCT/JP2017/027642 JP2017027642W WO2018025795A1 WO 2018025795 A1 WO2018025795 A1 WO 2018025795A1 JP 2017027642 W JP2017027642 W JP 2017027642W WO 2018025795 A1 WO2018025795 A1 WO 2018025795A1
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positive electrode
active material
electrode active
secondary battery
electrolyte secondary
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PCT/JP2017/027642
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French (fr)
Japanese (ja)
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基史 松田
肇 竹内
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株式会社三徳
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Priority to JP2018531878A priority Critical patent/JPWO2018025795A1/en
Publication of WO2018025795A1 publication Critical patent/WO2018025795A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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, a positive electrode containing the positive electrode active material, and a non-aqueous electrolyte secondary battery using the positive electrode.
  • Lithium ion secondary batteries which are a type of non-aqueous electrolyte secondary battery, are widely used as batteries for portable electronic devices such as video cameras, portable audio players, mobile phones, and notebook computers. In recent years, it has become mainstream that such a lithium ion secondary battery is used under a high voltage of 4.30 V or more. When charged at a high voltage, more capacity can be used, but there is a problem that the amount of Li desorbed from the positive electrode active material increases and the positive electrode active material tends to deteriorate.
  • Patent Document 1 proposes a method of stabilizing the crystal structure by substituting part of Co in the positive electrode active material with Na or K.
  • Patent Document 2 Co, Al, and Mg are added to the positive electrode active material LiNiO 2 , and at least one of K, Na, Rb, or Cs is further added to efficiently suppress the collapse of the Li layer. A method has been proposed.
  • Patent Documents 1 and 2 have a problem that the structure is not sufficiently stabilized during high-voltage charging and the capacity is low. Under such circumstances, the present inventors substituted a part of Li in the lithium-containing composite oxide particles with Na, adhered a specific surface modifier on the particle surface, and set the content ratio of each element within a specific range. It was found that a positive electrode active material exhibiting excellent characteristics during high-voltage charging can be obtained by controlling to (see Patent Document 3).
  • Patent Document 3 It has been found that the positive electrode active material described in Patent Document 3 exhibits a high discharge capacity and capacity retention ratio (cycle characteristics) when charged at a high voltage of 4.50V. However, if a higher voltage of, for example, 4.55 V or higher is used, the capacity retention rate cannot be said to be sufficient, and further improvement is required.
  • an object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that can exhibit a sufficient discharge capacity and an excellent capacity retention rate when charged at a high voltage of 4.55 V or higher.
  • Another object of the present invention is to provide a positive electrode containing the positive electrode active material and a non-aqueous electrolyte secondary battery manufactured using the positive electrode.
  • the present inventors control the Li content ratio, the Na content ratio, the ratio of Li and Na to other elements, etc. within a specific range in a positive electrode active material composed of lithium-containing composite oxide particles and a surface modifying material. Thus, it has been found that excellent discharge characteristics can be achieved at the time of high voltage charging of 4.55 V or more, and the present invention has been completed.
  • the lithium-containing composite oxide particles and the surface modifying substance attached to the surface of the particles the following formula (1): Li xy Na y Co w Al a Mg b M c O 2+ ⁇ ⁇ (1)
  • x, y, w, a, b, c, and ⁇ are the formulas 0.986 ⁇ (xy) ⁇ 1.050, 0 ⁇ y ⁇ 0.020, 0.996 ⁇ x ⁇ 1.050, 0.990 ⁇ w ⁇ 1.015, 0.005 ⁇ a ⁇ 0.020, 0.001 ⁇ b ⁇ 0.020, 0.0005 ⁇ c ⁇ 0.005, and ⁇ 0.
  • the ratio (x) / (w + a + b + c) of (Li + Na) to (Co + Al + Mg + M) is 0.930 or more and less than 0.990, and M is Ca, rare earth element, Ti, Zr, Selected from Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P, S, F, Cl, and H One or more elements.
  • a positive electrode active material for a non-aqueous electrolyte secondary battery wherein the surface modifying material contains one or more elements selected from Al, Mg, and M.
  • a positive electrode containing the positive electrode active material and a nonaqueous electrolyte secondary battery including the positive electrode are provided.
  • the positive electrode active material of the present invention has the above-mentioned specific composition, it has high structural stability, and therefore can exhibit a sufficient discharge capacity and an excellent capacity retention rate (cycle characteristics) when charged at a high voltage of 4.55 V or higher. .
  • a nonaqueous electrolyte secondary battery using a positive electrode containing the positive electrode active material has excellent discharge characteristics during high-voltage charging.
  • the positive electrode active material of the present invention is a positive electrode active material for a nonaqueous electrolyte secondary battery having a composition represented by the following formula (1).
  • x, y, w, a, b, c, and ⁇ are represented by the formula 0.986 ⁇ (xy) ⁇ 1.050, 0 ⁇ y ⁇ 0.020, 0.996 ⁇ x.
  • the ratio (x) / (w + a + b + c) of (Li + Na) to (Co + Al + Mg + M) is 0.930 or more and less than 0.990, and M is Ca, rare earth element, Ti, Zr, Hf , V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P, S, F, Cl, and H One or more elements are shown.
  • x represents the total content ratio (molar ratio) of Li and Na.
  • x is a value within the range of 0.996 ⁇ x ⁇ 1.050. If x is less than 0.996, the stability in the Li desorption state may decrease. On the other hand, when x exceeds 1.050, the crystallinity is lowered, so that the charge / discharge capacity and the capacity retention ratio (cycle characteristics) are lowered.
  • the range of x is preferably 1.030 or less, more preferably 1.010 or less, and still more preferably 0.999 or less. When x is 0.999 or less, a very excellent capacity maintenance ratio can be obtained particularly when charging at a high voltage of 4.55 V or more.
  • (xy) represents the content ratio (molar ratio) of Li.
  • (Xy) is a value in the range of 0.986 ⁇ (xy) ⁇ 1.050.
  • (xy) is less than 0.986, the stability of the crystal structure in the Li desorption state may be reduced.
  • (xy) is 1.050 or more, the crystallinity is lowered, so that the charge / discharge capacity and the capacity retention rate are lowered.
  • the range of (xy) is preferably less than 1.030, more preferably 1.003 or less, and still more preferably 0.990 or less. When (xy) is 0.990 or less, a very excellent capacity retention rate can be obtained particularly when charging at a high voltage of 4.55 V or more.
  • y represents the content ratio (molar ratio) of Na.
  • Na is dissolved in the layer of LiCoO 2 that is a layered compound, and can suppress the collapse of the crystal structure during charging when Li is desorbed. This is presumed to be because Na has a lower mobility than Li and takes time to pull out by applying a voltage, so it stays between the layers, suppresses the collapse of the crystal structure, and improves the durability during charging. Is done.
  • y it is possible to suppress the collapse of the crystal structure due to the detachment of Li, especially during continuous charging or high voltage charging of 4.3 V or higher. can get. Since Na has a larger ionic radius than Li, if a part of Li is replaced with Na, the interlayer expands.
  • y is 0 ⁇ y ⁇ 0.020.
  • y is preferably 0.002 or more, more preferably 0.004 or more.
  • y is preferably 0.018 or less, more preferably 0.010 or less. If y exceeds 0.020, it is presumed that the battery characteristics will be adversely affected, for example, Na will be excessive and Na will not enter the Li layer and the crystal structure cannot be maintained.
  • w represents the content ratio (molar ratio) of Co.
  • Co is one of the main elements constituting the positive electrode active material of the present invention.
  • the range of w is 0.990 ⁇ w ⁇ 1.015.
  • w is less than 0.990, the discharge capacity and the capacity retention rate decrease.
  • w exceeds 1.015, the stability of the crystal structure decreases.
  • a represents the Al content ratio (molar ratio). Al stabilizes the crystal structure, thereby improving thermal stability and continuous charge characteristics.
  • the range of a is 0.005 ⁇ a ⁇ 0.020, and preferably 0.010 ⁇ a ⁇ 0.016. When a is less than 0.005, the continuous charge characteristics are deteriorated. On the other hand, when a exceeds 0.020, the discharge capacity decreases.
  • b represents the content ratio (molar ratio) of Mg.
  • Mg stabilizes the crystal structure, thereby improving thermal stability and continuous charge characteristics.
  • the range of b is 0.001 ⁇ b ⁇ 0.020, and preferably 0.005 ⁇ b ⁇ 0.012. If b is less than 0.001, the structure stabilizing effect may not be sufficiently exhibited. On the other hand, if b exceeds 0.020, the specific surface area may become too small.
  • c represents the content ratio (molar ratio) of M.
  • M is Ca, rare earth element, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P 1 or more elements selected from S, F, Cl, and H. That is, M represents an element other than Li, Na, Co, Al, Mg, and O contained in the positive electrode active material of the present invention.
  • c represents the total content ratio (molar ratio) of the plurality of elements.
  • the range of c is 0.0005 ⁇ c ⁇ 0.005, and preferably 0.001 ⁇ c ⁇ 0.003.
  • “rare earth element” includes Y, Sc, and lanthanoid.
  • the stability of the crystal structure is further improved.
  • the content ratio (molar ratio) of Zr is preferably 0.0001 or more and less than 0.005, and more preferably 0.0005 or more and 0.003 or less. If the Zr content is less than 0.0001, the effect of improving the stability may not be sufficiently exhibited, and if it is 0.005 or more, the specific surface area may be too small.
  • the Li deintercalation or intercalation speed at the time of charge / discharge is increased, so that the load characteristics are improved.
  • the content ratio (molar ratio) of Ti is preferably 0.0001 or more and less than 0.005, and more preferably 0.0005 or more and 0.003 or less. If the Ti content is less than 0.0001, the load characteristic improvement effect may not be sufficiently exhibited, and if it is 0.005 or more, the growth of primary particles is suppressed, and the number of primary particles forming secondary particles is small. May increase.
  • the positive electrode active material of the present invention preferably contains both Ti and Zr as M. In this case, it is possible to manufacture a battery exhibiting high load characteristics and high capacity with stable quality using the positive electrode active material.
  • (2 + ⁇ ) represents the oxygen content (molar ratio).
  • the range of ⁇ is ⁇ 0.1 ⁇ ⁇ ⁇ 0.1, and is determined by the content ratio of Li, Na, Co, Al, Mg, and M.
  • (X) / (w + a + b + c) represents the molar ratio of (Li + Na) to (Co + Al + Mg + M).
  • the molar ratio (x) / (w + a + b + c) is 0.930 or more, preferably 0.960 or more, more preferably 0.965 or more.
  • the molar ratio (x) / (w + a + b + c) is less than 0.990, preferably 0.980 or less, and more preferably 0.975 or less. When this molar ratio is less than 0.930, the structural stability during charging is extremely lowered. On the other hand, when it is 0.990 or more, the capacity maintenance rate at the time of high voltage charging of 4.55 V or more may decrease. When this molar ratio is 0.980 or less, the discharge capacity is particularly improved.
  • the positive electrode active material of the present invention comprises lithium-containing composite oxide particles and a surface modifying material attached to the surface of the composite oxide particles. That is, the above formula (1) represents the total composition of the composite oxide particles and the surface modifier. This composition can be measured by quantitative analysis with an ICP (Inductively Coupled Plasma) analyzer.
  • ICP Inductively Coupled Plasma
  • the composite oxide particles include Li, Na, Co, and O, and optionally, Al, Mg, Ca, rare earth elements, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, One or more elements selected from Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P, S, F, Cl, and H may be included.
  • the composite oxide particles are preferably composed of Li, Na, Co, and O, and one or more elements selected from Mg, Ti, and Zr.
  • the surface modifier contains one or more elements selected from Al, Mg, and M.
  • Surface modifying substances are Al, Mg, Ca, rare earth elements, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, Si, and It is preferable to include one or more elements selected from Sn, and optionally to include one or more elements selected from Li, Na, Co, O, C, N, P, S, F, Cl, and H. You may go out. More preferably, the surface modifying material contains one or more elements selected from Al, Mg, Ti, Zr, and La. From the viewpoint of improving the capacity retention rate, it is particularly preferable that the surface modifier contains Al.
  • the surface modifying substance may be an inorganic compound such as a hydroxide, an oxide, or a carbonate, or may be a substance derived from the inorganic compound.
  • the inorganic compound include aluminum nitrate, aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, and an oxide having lithium ion conductivity.
  • the surface modifying substance is uniformly dispersed on the surface of the composite oxide particle.
  • “the surface modifying substance is attached to the surface of the composite oxide particle” means that the surface modifying substance is held in contact with the surface. It may be in a state of being adsorbed or adhered to the surface, or in a state in which the surface modifying substance is chemically bonded to the surface.
  • the method for preparing the composite oxide particles is not particularly limited.
  • a lithium compound as a lithium source, a sodium compound as a sodium source, a cobalt compound as a cobalt source, an aluminum compound as an aluminum source, a magnesium compound as a magnesium source, and an M-containing compound as an M source are obtained.
  • the resulting mixture can be fired to prepare composite oxide particles.
  • lithium compound examples include inorganic salts such as lithium hydroxide, lithium chloride, lithium nitrate, lithium carbonate, and lithium sulfate, and organic salts such as lithium formate, lithium acetate, and lithium oxalate.
  • inorganic salts such as lithium hydroxide, lithium chloride, lithium nitrate, lithium carbonate, and lithium sulfate
  • organic salts such as lithium formate, lithium acetate, and lithium oxalate.
  • Examples of the sodium compound include inorganic salts such as sodium hydroxide, sodium chloride, sodium nitrate, sodium carbonate, and sodium sulfate, and organic salts such as sodium formate, sodium acetate, and sodium oxalate.
  • inorganic salts such as sodium hydroxide, sodium chloride, sodium nitrate, sodium carbonate, and sodium sulfate
  • organic salts such as sodium formate, sodium acetate, and sodium oxalate.
  • cobalt compound examples include oxides, hydroxides, carbonates, oxyhydroxides, and the like. Cobalt oxide is preferably used.
  • the shape of the positive electrode active material is affected by the shape of the cobalt compound. Therefore, the shape of the positive electrode active material can be controlled by making the cobalt compound spherical or elliptical and adjusting the particle size, particle size distribution, and the like.
  • Examples of the aluminum compound include aluminum hydroxide, aluminum chloride, aluminum oxide, aluminum carbonate, aluminum nitrate, aluminum sulfate, and aluminum formate.
  • magnesium compound examples include magnesium hydroxide, magnesium carbonate, magnesium chloride, magnesium peroxide, magnesium oxide, magnesium nitrate, magnesium acetate, magnesium sulfate and the like.
  • M-containing compound examples include M-containing oxides, hydroxides, carbonates, sulfates, nitrates, halides, and the like. Depending on the element selected, the M-containing compound may be a gas containing M.
  • a predetermined amount of each of a lithium compound, a sodium compound, a cobalt compound, an aluminum compound, a magnesium compound, and an M-containing compound is weighed and mixed.
  • Mixing can be performed by a known method using a ball mill or the like, but it is preferable to use a high-speed stirring mixer to improve dispersibility.
  • the obtained mixture is fired. Firing can be performed by a known method using a cart furnace, a kiln furnace, a mesh belt furnace, or the like.
  • the calcination temperature may be 950 to 1050 ° C., preferably 1030 to 1050 ° C.
  • the firing time may be 1 to 24 hours.
  • the main baking may be performed by raising the temperature to the baking temperature.
  • Pre-baking and annealing are preferably performed at 500 to 800 ° C. for about 30 minutes to 6 hours.
  • lithium source sodium source
  • cobalt source aluminum source
  • magnesium source magnesium source
  • M source magnesium source
  • composite compounds may also be used.
  • a method in which Co, Al, Mg, and M are combined by a coprecipitation method to prepare a composite compound, which is mixed with a lithium compound and a sodium compound, and the resulting mixture is fired is also preferably performed.
  • the surface-modifying substance can be attached to the composite oxide particles by mixing the composite oxide particles with the raw material of the surface-modifying substance in a solvent and filtering and baking the resulting mixture. What is necessary is just to adjust the quantity of the composite oxide particle to mix and the amount of surface modification substance raw material so that the composition of Formula (1) may be obtained.
  • the molar ratio of the surface modifying material raw material to the composite oxide is 0.05 to 0.50 mol%. Of course, this molar ratio is the ratio of the composite oxide particles and the surface modifying material in the mixing step, and not the ratio of the composite oxide particles and the surface modifying material in the positive electrode active material.
  • the firing step may be performed at 200 to 700 ° C. for about 1 to 10 hours.
  • a method including the following steps is exemplified as a method of attaching the surface modifying substance to the composite oxide particles.
  • Step 1 Each of the composite oxide particles, the raw material of the surface modifying substance, and lithium hydroxide monohydrate (pH adjuster) is weighed.
  • Step 2 Lithium hydroxide monohydrate is dissolved in 100 mL of pure water, and then mixed oxide particles are added to prepare a first slurry liquid.
  • Step 3) A surface modifying substance raw material solution is prepared by dissolving a surface modifying substance raw material in 10 mL of pure water.
  • Step 4) The surface modifying substance raw material liquid is charged into the first slurry liquid to prepare a second slurry liquid.
  • Step 5 Stir the second slurry to stabilize the pH.
  • Step 6 The second slurry liquid whose pH is stabilized is filtered, and the obtained cake (filtrate) is washed with pure water.
  • Step 7) By baking the washed cake, the surface modifying substance is attached to the surface of the composite oxide particles, and a positive electrode active material is obtained.
  • Cleaning may be performed during the manufacturing process of the positive electrode active material.
  • Na that could not be completely dissolved between the layers of the composite oxide can be removed, thereby reducing Na eluted in the electrolytic solution and inhibiting insertion / extraction of lithium ions generated in the electrolytic solution.
  • Side reactions can be suppressed, and deterioration of charge / discharge characteristics due to Na can be minimized.
  • this washing may be performed before or after the surface modifier is attached to the surface of the composite oxide particle as long as the side reaction can be suppressed.
  • the aluminum nitrate when used as a raw material for the surface modifying substance, at least a part of the aluminum nitrate can be converted into aluminum hydroxide in the mixing step.
  • aluminum oxide or metal aluminum (aluminum alone) may be generated from aluminum hydroxide, and at least a part of the aluminum hydroxide may remain as it is. That is, in this case, by appropriately selecting the conditions of each step, aluminum nitrate, aluminum hydroxide, aluminum oxide, and / or aluminum simple substance can be attached to the surface of the composite oxide particle as a surface modifier.
  • one or more substances may be attached to the composite oxide particles as the surface modifying substance.
  • the above formula (1) represents the total composition of the plurality of substances and the composite oxide particles.
  • each element of the formula (1) is not uniformly distributed over the entire positive electrode active material, and the surface of the positive electrode active material is a surface modifying material.
  • the content ratio of the contained elements increases.
  • the positive electrode active material has a special composition and structure, and thus exhibits a remarkable effect.
  • the average particle diameter of the positive electrode active material is not particularly limited, but is preferably about 2 to 50 ⁇ m so that a sufficient density can be obtained when it is applied to the electrode plate. In order to improve the density, a plurality of positive electrode active materials having different average particle diameters within the average particle diameter range may be mixed.
  • the positive electrode for a non-aqueous electrolyte secondary battery of the present invention contains the above-described positive electrode active material of the present invention.
  • the positive electrode active material exhibits a stable crystal structure during charging, so that there is little deterioration due to continuous charging or high voltage charging, and high capacity and high capacity retention are achieved.
  • the positive electrode of the present invention may be produced by a known method. For example, a positive electrode active material and a conductive agent or a binder are kneaded in a dispersion medium, and the resulting slurry is applied to an electrode plate, dried, roller-rolled, cut into a predetermined size, and the positive electrode is Can be made.
  • the positive electrode active material of the present invention is used, the positive electrode active material, the conductive agent, the binder, and the like are uniformly dispersed, the slurry exhibits appropriate fluidity, and changes with time are small.
  • the thickness of the positive electrode is 40 to 120 ⁇ m.
  • the conductive agent binder, dispersion medium, electrode plate, etc. for producing the positive electrode
  • known ones can be used.
  • the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, ketjen black, and acetylene black.
  • binders fluorine resins (polytetrafluoroethylene, polyvinylidene fluoride, etc.), polyvinyl acetate, polymethyl methacrylate, ethylene-propylene-butadiene copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer Examples thereof include merging and carboxymethylcellulose.
  • dispersion medium examples include N-methylpyrrolidone, tetrahydrofuran, ethylene oxide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, dimethylformamide, dimethylacetamide and the like.
  • a porous or non-porous conductive substrate is used as the electrode plate.
  • the conductive substrate include metal foils such as Al, Cu, Ti, and stainless steel. Of these, an Al foil is preferable, and the thickness of the Al foil is preferably 10 to 30 ⁇ m.
  • the nonaqueous electrolyte secondary battery of the present invention has the above-described positive electrode for a nonaqueous electrolyte secondary battery of the present invention.
  • the positive electrode active material exhibits a stable crystal structure during charging, so that there is little deterioration due to continuous charging or high voltage charging, and a high capacity and a high capacity retention rate are achieved.
  • the nonaqueous electrolyte secondary battery of the present invention is mainly composed of a battery case, a positive electrode, a negative electrode, an organic solvent, an electrolyte, and a separator.
  • a solid electrolyte may be used instead of the organic solvent and the electrolyte (electrolyte solution).
  • Known materials can be used as the negative electrode, organic solvent, electrolyte, and separator.
  • the negative electrode is obtained by applying a negative electrode mixture in which a negative electrode active material, a binder, a conductive agent, a dispersion medium, and the like are mixed on a current collector made of a metal foil such as Cu, and then rolling and drying. It is done.
  • a negative electrode active material lithium metal, lithium alloy, amorphous carbon artificial graphite (soft carbon, hard carbon, etc.), carbonaceous material (natural graphite, etc.) and the like are used. If necessary, the same binder and dispersion medium as those for the positive electrode are used.
  • the type of the organic solvent is not particularly limited.
  • carbonates propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc.
  • ethers (1,2-dimethoxypropane, 1,3-dimethoxypropane, Tetrahydrofuran, 2-methyltetrahydrofuran, etc.
  • esters methyl acetate, ⁇ -butyrolactone, etc.
  • nitriles acetonitrile, butyronitrile, etc.
  • amides N, N-dimethylformamide, N, N-dimethylacetamide, etc.
  • Examples of the electrolyte dissolved in the organic solvent include LiClO 4 , LiPF 6 , LiBF 4 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCF 3 SO 3 , LiCF 3 CO 2 , Li (CF 3 SO 2 ) 2 , LiAsF 6 ,
  • Examples include LiB 10 Cl 10 , lower aliphatic lithium carboxylate, lithium tetrachloroborate, lithium tetraphenylborate, and imides. These may be used alone or in combination of two or more.
  • solid electrolytes examples include polymer electrolytes (polyethylene oxide electrolytes, etc.), sulfide electrolytes (Li 2 S—SiS 2 , Li 2 SP—S 2 S 5 , Li 2 S—B 2 S 3 etc.), etc. Is mentioned.
  • a so-called gel type electrolyte in which a nonaqueous electrolyte solution is held in a polymer can also be used.
  • a microporous thin film having high ion permeability, predetermined mechanical strength, and electronic insulation is preferably used.
  • a microporous thin film made of a material such as polyethylene, polypropylene, polyphenylene sulfide, polyethylene terephthalate, polyamide, or polyimide because of its excellent resistance to electrolyte and hydrophobicity. These materials may be used alone or in combination. From the viewpoint of manufacturing cost, it is preferable to use inexpensive polypropylene or the like.
  • the shape of the nonaqueous electrolyte secondary battery of the present invention can be selected from various shapes such as a cylindrical shape, a laminated shape, and a coin shape. Regardless of the shape, the above-described components are housed in the battery case, and the space between the positive electrode and the negative electrode to the positive electrode terminal and the negative electrode terminal is connected with a current collecting lead or the like, and the battery case is sealed.
  • Example 1 Manufacture of positive electrode active material
  • Lithium carbonate, sodium carbonate, cobalt oxide, aluminum hydroxide, magnesium hydroxide, titanium oxide, and zirconium oxide were weighed so that the positive electrode active material finally obtained had the composition shown in Table 1, and a high-speed stirring mixer To obtain a mixture.
  • the mixture was calcined at 700 ° C. for 4 hours using a box-type electric furnace, and then baked at 1030 ° C. for 5 hours to obtain a composite oxide.
  • Lithium hydroxide monohydrate was dissolved in 100 mL of pure water, and a composite oxide was added thereto to prepare a first slurry liquid.
  • aluminum nitrate nonahydrate was dissolved in 10 mL of pure water to prepare a surface modifying material raw material liquid.
  • the surface modifier material liquid is put into the first slurry liquid at a rate of 5 mL / min using a pipetter, it is stirred for 5 minutes or more, and it is confirmed that the pH is stable at around 10.7, and then the second slurry. A liquid was obtained.
  • the second slurry was filtered, and the resulting cake was washed with 200 mL of pure water.
  • the washed cake was heated to 500 ° C. at a temperature rising rate of 5 ° C./min, and baked for 3 hours after reaching 500 ° C. to obtain a positive electrode active material having the composition shown in Table 1.
  • This positive electrode active material is composed of composite oxide particles and an Al-containing surface modifier adhering to the surface.
  • the obtained positive electrode active material, graphite and acetylene black (conductive agent), and polyvinylidene fluoride (binder) were mixed at a mass ratio of 200: 4: 1: 10 and kneaded in N-methylpyrrolidone.
  • An electrode slurry was obtained. This electrode slurry was applied to an aluminum foil having a thickness of 20 ⁇ m, dried, press-molded to a thickness of 40 ⁇ m with a press machine, cut into a predetermined size, and terminals were spot welded to produce a positive electrode.
  • a test coin cell secondary battery was produced as follows. Metal lithium foil was used as a counter electrode (negative electrode), the positive electrode was used as a test electrode, and these were arranged in a battery case via a separator. A coin cell secondary battery was manufactured by injecting an electrolytic solution therein. The electrolytic solution was prepared by dissolving LiPF 6 as a supporting electrolyte at a concentration of 1M in a 1: 2 (volume ratio) mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC).
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • a charge / discharge test was performed as follows using the manufactured coin cell secondary battery. (1) The measurement temperature was 25 ° C., and in the first and second cycles, charging and discharging were performed under the conditions of a charge upper limit voltage 4.55 V, a discharge lower limit voltage 3.0 V, and a current density of 0.3 mA / cm 2 . (2) From the third cycle onward, charging / discharging was performed under the conditions of a charge upper limit voltage of 4.55 V, a discharge lower limit voltage of 3.0 V, and a current density of 1.5 mA / cm 2 .
  • Capacity retention rate (%) (discharge capacity at 22nd cycle / discharge capacity at 3rd cycle) ⁇ 100 Table 1 shows the discharge capacity and capacity retention rate of the first cycle.
  • Examples 2 to 6 and Comparative Examples 1 to 18 Cathode active materials of Examples 2 to 6 and Comparative Examples 1 to 18 were produced in the same manner as in Example 1 except that the composition of the raw material compounds was changed and the compositions shown in Table 1 were finally obtained. In addition, manganese sulfate (II) pentahydrate was used as a manganese source. A coin cell secondary battery was produced using each positive electrode active material in the same manner as in Example 1, and a charge / discharge test was performed. The results are shown in Table 1.

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Abstract

Provided are: a positive electrode active material which is capable of exhibiting sufficient discharge capacity and excellent capacity retention rate during high-voltage charging; a positive electrode which uses this positive electrode active material; and a secondary battery. This positive electrode active material is composed of lithium-containing composite oxide particles and a surface modification material adhered to the surfaces of the particles, and has a composition represented by formula (1). The surface modification material contains one or more elements selected from among Al, Mg and M. Lix-yNayCowAlaMgbMcO2+α (1) (In formula (1), x, y, w, a, b, c and α satisfy formulae 0.986 ≤ (x - y) < 1.050, 0 < y ≤ 0.020, 0.996 ≤ x ≤ 1.050, 0.990 ≤ w ≤ 1.015, 0.005 ≤ a ≤ 0.020, 0.001 ≤ b ≤ 0.020, 0.0005 ≤ c ≤ 0.005 and -0.1 ≤ α ≤ 0.1; the ratio of (Li + Na) to (Co + Al + Mg + M), namely (x)/(w + a + b + c) is 0.930 or more but less than 0.990; and M represents one or more elements selected from among Ca, rare earth elements, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P, S, F, Cl and H.)

Description

非水電解質二次電池用正極活物質、並びに該正極活物質を使用した正極及び二次電池Positive electrode active material for non-aqueous electrolyte secondary battery, and positive electrode and secondary battery using the positive electrode active material
　本発明は、正極活物質、該正極活物質を含有する正極、及び該正極を用いた非水電解質二次電池に関する。 The present invention relates to a positive electrode active material, a positive electrode containing the positive electrode active material, and a non-aqueous electrolyte secondary battery using the positive electrode.
　非水電解質二次電池の一種であるリチウムイオン二次電池は、ビデオカメラ、携帯型オーディオプレイヤー、携帯電話、ノートパソコン等の携帯用電子機器のバッテリーとして広く使用されている。近年、このようなリチウムイオン二次電池は４．３０Ｖ以上の高電圧下で使用されることが主流となってきている。高電圧で充電すると、より多くの容量を利用できる反面、正極活物質からＬｉが脱離する量が増え、正極活物質が劣化しやすいという問題がある。 Lithium ion secondary batteries, which are a type of non-aqueous electrolyte secondary battery, are widely used as batteries for portable electronic devices such as video cameras, portable audio players, mobile phones, and notebook computers. In recent years, it has become mainstream that such a lithium ion secondary battery is used under a high voltage of 4.30 V or more. When charged at a high voltage, more capacity can be used, but there is a problem that the amount of Li desorbed from the positive electrode active material increases and the positive electrode active material tends to deteriorate.
　上記問題を解決するために、正極活物質の構造を安定化させることが検討されている。構造を安定化させる手段として、正極活物質のコバルト酸リチウムにＣｏ以外の他元素を添加する方法や、Ｃｏを他元素で置換する方法が知られている。例えば、特許文献１では、正極活物質中のＣｏの一部をＮａやＫで置換することによって、結晶構造を安定化させる方法が提案されている。特許文献２では、正極活物質ＬｉＮｉＯ2にＣｏ、Ａｌ、及びＭｇを添加し、更にＫ、Ｎａ、Ｒｂ、又はＣｓの少なくとも１種を添加することで、Ｌｉ層の崩壊を効率的に抑制する方法が提案されている。 In order to solve the above problems, it has been studied to stabilize the structure of the positive electrode active material. As means for stabilizing the structure, a method of adding an element other than Co to lithium cobaltate, which is a positive electrode active material, and a method of replacing Co with another element are known. For example, Patent Document 1 proposes a method of stabilizing the crystal structure by substituting part of Co in the positive electrode active material with Na or K. In Patent Document 2, Co, Al, and Mg are added to the positive electrode active material LiNiO 2 , and at least one of K, Na, Rb, or Cs is further added to efficiently suppress the collapse of the Li layer. A method has been proposed.
　しかし、特許文献１及び２の方法は、高電圧充電時の構造安定化は十分ではなく、容量も低いという問題がある。このような状況下、本発明者は、リチウム含有複合酸化物粒子においてＬｉの一部をＮａで置換し、該粒子表面に特定の表面修飾物質を付着させ、各元素の含有割合を特定範囲内に制御することによって、高電圧充電時に優れた特性を示す正極活物質が得られることを見出した（特許文献３参照）。 However, the methods of Patent Documents 1 and 2 have a problem that the structure is not sufficiently stabilized during high-voltage charging and the capacity is low. Under such circumstances, the present inventors substituted a part of Li in the lithium-containing composite oxide particles with Na, adhered a specific surface modifier on the particle surface, and set the content ratio of each element within a specific range. It was found that a positive electrode active material exhibiting excellent characteristics during high-voltage charging can be obtained by controlling to (see Patent Document 3).
特開２００４－２６５８６３号JP 2004-265863 A 特開２００５－１１６４７０号JP-A-2005-116470 ＷＯ２０１５／００５４３９WO2015 / 005439
　特許文献３に記載の正極活物質は、４．５０Ｖという高電圧で充電した場合、高い放電容量及び容量維持率（サイクル特性）を示すことが分かっている。しかしながら、例えば４．５５Ｖ以上という更に高い電圧を用いると容量維持率は十分とは言えず、更なる改善が求められている。 It has been found that the positive electrode active material described in Patent Document 3 exhibits a high discharge capacity and capacity retention ratio (cycle characteristics) when charged at a high voltage of 4.50V. However, if a higher voltage of, for example, 4.55 V or higher is used, the capacity retention rate cannot be said to be sufficient, and further improvement is required.
　従って、本発明の課題は、４．５５Ｖ以上の高電圧充電時に十分な放電容量と優れた容量維持率を示し得る非水電解質二次電池用正極活物質を提供することにある。 Therefore, an object of the present invention is to provide a positive electrode active material for a non-aqueous electrolyte secondary battery that can exhibit a sufficient discharge capacity and an excellent capacity retention rate when charged at a high voltage of 4.55 V or higher.
　本発明の別の課題は、上記正極活物質を含有する正極、及び該正極を用いて製造した非水電解質二次電池を提供することにある。 Another object of the present invention is to provide a positive electrode containing the positive electrode active material and a non-aqueous electrolyte secondary battery manufactured using the positive electrode.
　本発明者らは、リチウム含有複合酸化物粒子と表面修飾物質とからなる正極活物質において、Ｌｉ含有割合、Ｎａ含有割合、Ｌｉ及びＮａの他の元素に対する比等を特定範囲内に制御することによって、４．５５Ｖ以上の高電圧充電時に優れた放電特性を達成できることを見出し、本発明を完成するに至った。 The present inventors control the Li content ratio, the Na content ratio, the ratio of Li and Na to other elements, etc. within a specific range in a positive electrode active material composed of lithium-containing composite oxide particles and a surface modifying material. Thus, it has been found that excellent discharge characteristics can be achieved at the time of high voltage charging of 4.55 V or more, and the present invention has been completed.
　すなわち、本発明によれば、リチウム含有複合酸化物粒子と該粒子の表面に付着した表面修飾物質とからなり、下記式（１）：
　　　　　Ｌｉx-yＮａyＣｏwＡｌaＭｇbＭcＯ2+α　・・・（１）
［式（１）中、ｘ、ｙ、ｗ、ａ、ｂ、ｃ、及びαは、式０．９８６≦（ｘ－ｙ）＜１．０５０、０＜ｙ≦０．０２０、０．９９６≦ｘ≦１．０５０、０．９９０≦ｗ≦１．０１５、０．００５≦ａ≦０．０２０、０．００１≦ｂ≦０．０２０、０．０００５≦ｃ≦０．００５、及び－０．１≦α≦０．１を満たし、（Ｌｉ＋Ｎａ）と（Ｃｏ＋Ａｌ＋Ｍｇ＋Ｍ）との比（ｘ）／（ｗ＋ａ＋ｂ＋ｃ）が０．９３０以上０．９９０未満であり、ＭはＣａ、希土類元素、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗ、Ｍｎ、Ｆｅ、Ｎｉ、Ｃｕ、Ａｇ、Ｚｎ、Ｂ、Ｇａ、Ｃ、Ｓｉ、Ｓｎ、Ｎ、Ｐ、Ｓ、Ｆ、Ｃｌ、及びＨから選ばれる１種以上の元素を示す。］で表される組成を有し、前記表面修飾物質がＡｌ、Ｍｇ、及びＭから選ばれる１種以上の元素を含む、非水電解質二次電池用正極活物質が提供される。 That is, according to the present invention, the lithium-containing composite oxide particles and the surface modifying substance attached to the surface of the particles, the following formula (1):
Li xy Na y Co w Al a Mg b M c O 2+ α ··· (1)
[In the formula (1), x, y, w, a, b, c, and α are the formulas 0.986 ≦ (xy) <1.050, 0 <y ≦ 0.020, 0.996 ≦ x ≦ 1.050, 0.990 ≦ w ≦ 1.015, 0.005 ≦ a ≦ 0.020, 0.001 ≦ b ≦ 0.020, 0.0005 ≦ c ≦ 0.005, and −0. 1 ≦ α ≦ 0.1 is satisfied, and the ratio (x) / (w + a + b + c) of (Li + Na) to (Co + Al + Mg + M) is 0.930 or more and less than 0.990, and M is Ca, rare earth element, Ti, Zr, Selected from Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P, S, F, Cl, and H One or more elements. And a positive electrode active material for a non-aqueous electrolyte secondary battery, wherein the surface modifying material contains one or more elements selected from Al, Mg, and M.
　また、本発明によれば、上記正極活物質を含有する正極、及び該正極を備えた非水電解質二次電池が提供される。 Also, according to the present invention, a positive electrode containing the positive electrode active material and a nonaqueous electrolyte secondary battery including the positive electrode are provided.
　本発明の正極活物質は上記特定の組成を有するので、高い構造安定性を有し、そのため４．５５Ｖ以上の高電圧充電時に十分な放電容量と優れた容量維持率（サイクル特性）を示し得る。当該正極活物質を含有する正極を用いた非水電解質二次電池は、高電圧充電時の放電特性に優れている。 Since the positive electrode active material of the present invention has the above-mentioned specific composition, it has high structural stability, and therefore can exhibit a sufficient discharge capacity and an excellent capacity retention rate (cycle characteristics) when charged at a high voltage of 4.55 V or higher. . A nonaqueous electrolyte secondary battery using a positive electrode containing the positive electrode active material has excellent discharge characteristics during high-voltage charging.
　本発明の正極活物質は、下記式（１）で表される組成を有する非水電解質二次電池用正極活物質である。
　　　　　Ｌｉx-yＮａyＣｏwＡｌaＭｇbＭcＯ2+α　・・・（１）
式（１）中、ｘ、ｙ、ｗ、ａ、ｂ、ｃ、及びαは、式０．９８６≦（ｘ－ｙ）＜１．０５０、０＜ｙ≦０．０２０、０．９９６≦ｘ≦１．０５０、０．９９０≦ｗ≦１．０１５、０．００５≦ａ≦０．０２０、０．００１≦ｂ≦０．０２０、０．０００５≦ｃ≦０．００５、及び－０．１≦α≦０．１を満たし、（Ｌｉ＋Ｎａ）と（Ｃｏ＋Ａｌ＋Ｍｇ＋Ｍ）との比（ｘ）／（ｗ＋ａ＋ｂ＋ｃ）が０．９３０以上０．９９０未満であり、ＭはＣａ、希土類元素、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗ、Ｍｎ、Ｆｅ、Ｎｉ、Ｃｕ、Ａｇ、Ｚｎ、Ｂ、Ｇａ、Ｃ、Ｓｉ、Ｓｎ、Ｎ、Ｐ、Ｓ、Ｆ、Ｃｌ、及びＨから選ばれる１種以上の元素を示す。 The positive electrode active material of the present invention is a positive electrode active material for a nonaqueous electrolyte secondary battery having a composition represented by the following formula (1).
Li xy Na y Co w Al a Mg b M c O 2+ α ··· (1)
In the formula (1), x, y, w, a, b, c, and α are represented by the formula 0.986 ≦ (xy) <1.050, 0 <y ≦ 0.020, 0.996 ≦ x. ≦ 1.050, 0.990 ≦ w ≦ 1.015, 0.005 ≦ a ≦ 0.020, 0.001 ≦ b ≦ 0.020, 0.0005 ≦ c ≦ 0.005, and −0.1 ≦ α ≦ 0.1 is satisfied, the ratio (x) / (w + a + b + c) of (Li + Na) to (Co + Al + Mg + M) is 0.930 or more and less than 0.990, and M is Ca, rare earth element, Ti, Zr, Hf , V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P, S, F, Cl, and H One or more elements are shown.
　式（１）において、ｘはＬｉとＮａの合計の含有割合（モル比）を表す。ｘは０．９９６≦ｘ≦１．０５０の範囲内の値である。ｘが０．９９６未満であると、Ｌｉ脱離状態における安定性が低下する場合がある。一方、ｘが１．０５０を超えると、結晶性が低下し、そのため充放電容量及び容量維持率（サイクル特性）が低下する。ｘの範囲は、好ましくは１．０３０以下であり、より好ましくは１．０１０以下であり、更に好ましくは０．９９９以下である。ｘが０．９９９以下であると、特に４．５５Ｖ以上の高電圧充電時に非常に優れた容量維持率が得られる。 In the formula (1), x represents the total content ratio (molar ratio) of Li and Na. x is a value within the range of 0.996 ≦ x ≦ 1.050. If x is less than 0.996, the stability in the Li desorption state may decrease. On the other hand, when x exceeds 1.050, the crystallinity is lowered, so that the charge / discharge capacity and the capacity retention ratio (cycle characteristics) are lowered. The range of x is preferably 1.030 or less, more preferably 1.010 or less, and still more preferably 0.999 or less. When x is 0.999 or less, a very excellent capacity maintenance ratio can be obtained particularly when charging at a high voltage of 4.55 V or more.
　式（１）において、（ｘ－ｙ）はＬｉの含有割合（モル比）を表す。正極活物質を電池に用いて充放電すると、Ｌｉ含有割合はディインターカレーション又はインターカレーションにより変動する。（ｘ－ｙ）は０．９８６≦（ｘ－ｙ）＜１．０５０の範囲内の値である。（ｘ－ｙ）が０．９８６未満の場合、Ｌｉ脱離状態における結晶構造の安定性が低下する場合がある。一方、（ｘ－ｙ）が１．０５０以上の場合、結晶性が低下し、そのため充放電容量及び容量維持率が低下する。（ｘ－ｙ）の範囲は、好ましくは１．０３０未満であり、より好ましくは１．００３以下であり、更に好ましくは０．９９０以下である。（ｘ－ｙ）が０．９９０以下であると、特に４．５５Ｖ以上の高電圧充電時に非常に優れた容量維持率が得られる。 In the formula (1), (xy) represents the content ratio (molar ratio) of Li. When the positive electrode active material is used for charging / discharging the battery, the Li content varies due to deintercalation or intercalation. (Xy) is a value in the range of 0.986 ≦ (xy) <1.050. When (xy) is less than 0.986, the stability of the crystal structure in the Li desorption state may be reduced. On the other hand, when (xy) is 1.050 or more, the crystallinity is lowered, so that the charge / discharge capacity and the capacity retention rate are lowered. The range of (xy) is preferably less than 1.030, more preferably 1.003 or less, and still more preferably 0.990 or less. When (xy) is 0.990 or less, a very excellent capacity retention rate can be obtained particularly when charging at a high voltage of 4.55 V or more.
　式（１）において、ｙはＮａの含有割合（モル比）を表す。Ｎａは、層状化合物であるＬｉＣｏＯ2の層間に固溶し、Ｌｉが脱離した状態となる充電時に結晶構造の崩壊を抑制することができる。これは、ＮａがＬｉと比べて移動度が小さく電圧印加による引き抜きに時間がかかるため、層間にとどまり、結晶構造の崩壊を抑制し、充電時の耐久性を向上させているためであると推測される。ｙを最適化することで、特に連続充電時や４．３Ｖ以上の高電圧充電時におけるＬｉの脱離による結晶構造の崩壊を抑制することができ、最終的に高容量や高容量維持率が得られる。ＮａはＬｉと比べてイオン半径が大きいため、Ｌｉの一部をＮａで置換すると層間が拡大する。これは粉末Ｘ線回折（ＸＲＤ）で観察されるピークがＮａを含まない材料と比べると低角側へシフトしていることで確認できる。ｙの範囲は０＜ｙ≦０．０２０である。ｙは好ましくは０．００２以上、より好ましくは０．００４以上である。一方、ｙは好ましくは０．０１８以下、より好ましくは０．０１０以下である。ｙが０．０２０を超えるとＮａ過多となり、Ｌｉ層にＮａが入りきらず結晶構造を維持できなくなるなど、最終的に電池特性に悪影響を及ぼすと推測される。 In the formula (1), y represents the content ratio (molar ratio) of Na. Na is dissolved in the layer of LiCoO 2 that is a layered compound, and can suppress the collapse of the crystal structure during charging when Li is desorbed. This is presumed to be because Na has a lower mobility than Li and takes time to pull out by applying a voltage, so it stays between the layers, suppresses the collapse of the crystal structure, and improves the durability during charging. Is done. By optimizing y, it is possible to suppress the collapse of the crystal structure due to the detachment of Li, especially during continuous charging or high voltage charging of 4.3 V or higher. can get. Since Na has a larger ionic radius than Li, if a part of Li is replaced with Na, the interlayer expands. This can be confirmed by the fact that the peak observed by powder X-ray diffraction (XRD) is shifted to a lower angle side as compared with a material not containing Na. The range of y is 0 <y ≦ 0.020. y is preferably 0.002 or more, more preferably 0.004 or more. On the other hand, y is preferably 0.018 or less, more preferably 0.010 or less. If y exceeds 0.020, it is presumed that the battery characteristics will be adversely affected, for example, Na will be excessive and Na will not enter the Li layer and the crystal structure cannot be maintained.
　式（１）において、ｗはＣｏの含有割合（モル比）を表す。Ｃｏは本発明の正極活物質を構成する主要元素の一つである。ｗの範囲は０．９９０≦ｗ≦１．０１５である。ｗが０．９９０未満であると放電容量及び容量維持率が低下する。一方、ｗが１．０１５を超えると結晶構造の安定性が低下する。 In the formula (1), w represents the content ratio (molar ratio) of Co. Co is one of the main elements constituting the positive electrode active material of the present invention. The range of w is 0.990 ≦ w ≦ 1.015. When w is less than 0.990, the discharge capacity and the capacity retention rate decrease. On the other hand, if w exceeds 1.015, the stability of the crystal structure decreases.
　式（１）において、ａはＡｌの含有割合（モル比）を表す。Ａｌは結晶構造を安定化し、これにより熱安定性及び連続充電特性を向上させる。ａの範囲は０．００５≦ａ≦０．０２０であり、好ましくは０．０１０≦ａ≦０．０１６である。ａが０．００５未満であると連続充電特性が低下する。一方、ａが０．０２０を超えると放電容量が低下する。 In the formula (1), a represents the Al content ratio (molar ratio). Al stabilizes the crystal structure, thereby improving thermal stability and continuous charge characteristics. The range of a is 0.005 ≦ a ≦ 0.020, and preferably 0.010 ≦ a ≦ 0.016. When a is less than 0.005, the continuous charge characteristics are deteriorated. On the other hand, when a exceeds 0.020, the discharge capacity decreases.
　式（１）において、ｂはＭｇの含有割合（モル比）を表す。Ｍｇは結晶構造を安定化し、これにより熱安定性及び連続充電特性を向上させる。ｂの範囲は、０．００１≦ｂ≦０．０２０であり、好ましくは０．００５≦ｂ≦０．０１２である。ｂが０．００１未満であると構造安定化効果が十分に現れない場合がある。一方、ｂが０．０２０を超えると比表面積が小さくなりすぎることがある。 In formula (1), b represents the content ratio (molar ratio) of Mg. Mg stabilizes the crystal structure, thereby improving thermal stability and continuous charge characteristics. The range of b is 0.001 ≦ b ≦ 0.020, and preferably 0.005 ≦ b ≦ 0.012. If b is less than 0.001, the structure stabilizing effect may not be sufficiently exhibited. On the other hand, if b exceeds 0.020, the specific surface area may become too small.
　式（１）において、ｃはＭの含有割合（モル比）を表す。ＭはＣａ、希土類元素、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗ、Ｍｎ、Ｆｅ、Ｎｉ、Ｃｕ、Ａｇ、Ｚｎ、Ｂ、Ｇａ、Ｃ、Ｓｉ、Ｓｎ、Ｎ、Ｐ、Ｓ、Ｆ、Ｃｌ、及びＨから選ばれる１種以上の元素を示す。すなわち、Ｍは、本発明の正極活物質に含まれるＬｉ、Ｎａ、Ｃｏ、Ａｌ、Ｍｇ、及びＯ以外の元素を表す。勿論、Ｍが複数の元素を示す場合、ｃは当該複数の元素の合計の含有割合（モル比）を表す。ｃの範囲は、０．０００５≦ｃ≦０．００５であり、好ましくは０．００１≦ｃ≦０．００３である。ｃが０．０００５以上であると結晶構造の安定性が向上し得る。一方、ｃが０．００５を超えると、詳細な機構は不明だが、容量維持率が低下する場合がある。なお、本発明において「希土類元素」はＹ、Ｓｃ、及びランタノイドを包含する。 In formula (1), c represents the content ratio (molar ratio) of M. M is Ca, rare earth element, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P 1 or more elements selected from S, F, Cl, and H. That is, M represents an element other than Li, Na, Co, Al, Mg, and O contained in the positive electrode active material of the present invention. Of course, when M represents a plurality of elements, c represents the total content ratio (molar ratio) of the plurality of elements. The range of c is 0.0005 ≦ c ≦ 0.005, and preferably 0.001 ≦ c ≦ 0.003. When c is 0.0005 or more, the stability of the crystal structure can be improved. On the other hand, when c exceeds 0.005, the detailed mechanism is unknown, but the capacity maintenance rate may be reduced. In the present invention, “rare earth element” includes Y, Sc, and lanthanoid.
　正極活物質がＭとしてＺｒを含む場合、結晶構造の安定性がより向上する。Ｚｒの含有割合（モル比）は、好ましくは０．０００１以上０．００５未満であり、より好ましくは０．０００５以上０．００３以下である。Ｚｒ含有割合が０．０００１未満であると安定性向上効果が十分に現れない場合があり、０．００５以上であると比表面積が小さくなりすぎることがある。 When the positive electrode active material contains Zr as M, the stability of the crystal structure is further improved. The content ratio (molar ratio) of Zr is preferably 0.0001 or more and less than 0.005, and more preferably 0.0005 or more and 0.003 or less. If the Zr content is less than 0.0001, the effect of improving the stability may not be sufficiently exhibited, and if it is 0.005 or more, the specific surface area may be too small.
　正極活物質がＭとしてＴｉを含む場合、充放電時におけるＬｉのディインターカレーション又はインターカレーションの速度が速くなるため、負荷特性が高くなる。Ｔｉの含有割合（モル比）は、好ましくは０．０００１以上０．００５未満であり、より好ましくは０．０００５以上０．００３以下である。Ｔｉ含有割合が０．０００１未満であると負荷特性改善効果が十分に現れない場合があり、０．００５以上であると一次粒子の成長が抑制され、二次粒子を形成する一次粒子の数が増加することがある。 When the positive electrode active material contains Ti as M, the Li deintercalation or intercalation speed at the time of charge / discharge is increased, so that the load characteristics are improved. The content ratio (molar ratio) of Ti is preferably 0.0001 or more and less than 0.005, and more preferably 0.0005 or more and 0.003 or less. If the Ti content is less than 0.0001, the load characteristic improvement effect may not be sufficiently exhibited, and if it is 0.005 or more, the growth of primary particles is suppressed, and the number of primary particles forming secondary particles is small. May increase.
　本発明の正極活物質は、ＭとしてＴｉとＺｒを共に含むのが好ましい。この場合、該正極活物質を用いて、高負荷特性及び高容量を示す電池を安定した品質で製造することが可能である。 The positive electrode active material of the present invention preferably contains both Ti and Zr as M. In this case, it is possible to manufacture a battery exhibiting high load characteristics and high capacity with stable quality using the positive electrode active material.
　式（１）において、（２＋α）は酸素の含有割合（モル比）を表す。αの範囲は－０．１≦α≦０．１であり、Ｌｉ、Ｎａ、Ｃｏ、Ａｌ、Ｍｇ、及びＭの含有割合により決定される。 In formula (1), (2 + α) represents the oxygen content (molar ratio). The range of α is −0.1 ≦ α ≦ 0.1, and is determined by the content ratio of Li, Na, Co, Al, Mg, and M.
　（ｘ）／（ｗ＋ａ＋ｂ＋ｃ）は（Ｌｉ＋Ｎａ）と（Ｃｏ＋Ａｌ＋Ｍｇ＋Ｍ）とのモル比を表す。モル比（ｘ）／（ｗ＋ａ＋ｂ＋ｃ）は０．９３０以上であり、好ましくは０．９６０以上であり、より好ましくは０．９６５以上である。また、モル比（ｘ）／（ｗ＋ａ＋ｂ＋ｃ）は０．９９０未満であり、好ましくは０．９８０以下であり、より好ましくは０．９７５以下である。このモル比が０．９３０未満である場合、充電時の構造安定性が極端に低下する。一方、０．９９０以上である場合は、４．５５Ｖ以上の高電圧充電時の容量維持率が低下する場合がある。このモル比が０．９８０以下であると、特に放電容量が向上する。 (X) / (w + a + b + c) represents the molar ratio of (Li + Na) to (Co + Al + Mg + M). The molar ratio (x) / (w + a + b + c) is 0.930 or more, preferably 0.960 or more, more preferably 0.965 or more. The molar ratio (x) / (w + a + b + c) is less than 0.990, preferably 0.980 or less, and more preferably 0.975 or less. When this molar ratio is less than 0.930, the structural stability during charging is extremely lowered. On the other hand, when it is 0.990 or more, the capacity maintenance rate at the time of high voltage charging of 4.55 V or more may decrease. When this molar ratio is 0.980 or less, the discharge capacity is particularly improved.
　本発明の正極活物質は、リチウム含有複合酸化物粒子と、該複合酸化物粒子の表面に付着した表面修飾物質とからなる。すなわち、上記式（１）は複合酸化物粒子と表面修飾物質の合計の組成を表す。この組成はＩＣＰ（Ｉｎｄｕｃｔｉｖｅｌｙ　Ｃｏｕｐｌｅｄ　Ｐｌａｓｍａ）分析装置で定量分析することによって測定できる。以下、リチウム含有複合酸化物粒子を単に複合酸化物粒子と称する。 The positive electrode active material of the present invention comprises lithium-containing composite oxide particles and a surface modifying material attached to the surface of the composite oxide particles. That is, the above formula (1) represents the total composition of the composite oxide particles and the surface modifier. This composition can be measured by quantitative analysis with an ICP (Inductively Coupled Plasma) analyzer. Hereinafter, the lithium-containing composite oxide particles are simply referred to as composite oxide particles.
　複合酸化物粒子はＬｉ、Ｎａ、Ｃｏ、及びＯを含み、更に任意にＡｌ、Ｍｇ、Ｃａ、希土類元素、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗ、Ｍｎ、Ｆｅ、Ｎｉ、Ｃｕ、Ａｇ、Ｚｎ、Ｂ、Ｇａ、Ｃ、Ｓｉ、Ｓｎ、Ｎ、Ｐ、Ｓ、Ｆ、Ｃｌ、及びＨから選ばれる１種以上の元素を含んでいてもよい。該複合酸化物粒子はＬｉ、Ｎａ、Ｃｏ、及びＯと、Ｍｇ、Ｔｉ、及びＺｒから選ばれる１種以上の元素とからなるのが好ましい。 The composite oxide particles include Li, Na, Co, and O, and optionally, Al, Mg, Ca, rare earth elements, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, One or more elements selected from Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P, S, F, Cl, and H may be included. The composite oxide particles are preferably composed of Li, Na, Co, and O, and one or more elements selected from Mg, Ti, and Zr.
　表面修飾物質はＡｌ、Ｍｇ、及びＭから選ばれる１種以上の元素を含む。表面修飾物質はＡｌ、Ｍｇ、Ｃａ、希土類元素、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗ、Ｍｎ、Ｆｅ、Ｎｉ、Ｃｕ、Ａｇ、Ｚｎ、Ｂ、Ｇａ、Ｓｉ、及びＳｎから選ばれる１種以上の元素を含むのが好ましく、更に任意にＬｉ、Ｎａ、Ｃｏ、Ｏ、Ｃ、Ｎ、Ｐ、Ｓ、Ｆ、Ｃｌ、及びＨから選ばれる１種以上の元素を含んでいてもよい。表面修飾物質はＡｌ、Ｍｇ、Ｔｉ、Ｚｒ、及びＬａから選ばれる１種以上の元素を含むのが更に好ましい。容量維持率改善の観点からは、表面修飾物質がＡｌを含むことが特に好ましい。 The surface modifier contains one or more elements selected from Al, Mg, and M. Surface modifying substances are Al, Mg, Ca, rare earth elements, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, Si, and It is preferable to include one or more elements selected from Sn, and optionally to include one or more elements selected from Li, Na, Co, O, C, N, P, S, F, Cl, and H. You may go out. More preferably, the surface modifying material contains one or more elements selected from Al, Mg, Ti, Zr, and La. From the viewpoint of improving the capacity retention rate, it is particularly preferable that the surface modifier contains Al.
　表面修飾物質は水酸化物、酸化物、炭酸化物等の無機化合物であってよく、該無機化合物に由来する物質であってもよい。無機化合物の具体例としては、硝酸アルミニウム、酸化アルミニウム、酸化マグネシウム、酸化チタン、酸化ジルコニウム、リチウムイオン伝導性を有する酸化物等が挙げられる。 The surface modifying substance may be an inorganic compound such as a hydroxide, an oxide, or a carbonate, or may be a substance derived from the inorganic compound. Specific examples of the inorganic compound include aluminum nitrate, aluminum oxide, magnesium oxide, titanium oxide, zirconium oxide, and an oxide having lithium ion conductivity.
　表面修飾物質は複合酸化物粒子の表面上で均一に分散して付着していることが好ましい。なお、本発明において「表面修飾物質が複合酸化物粒子の表面に付着している」とは、表面修飾物質が該表面に接触して保持されていることを意味し、表面修飾物質は該表面に吸着又は接着された状態であってよく、また表面修飾物質が該表面に化学的に結合している状態であってもよい。 It is preferable that the surface modifying substance is uniformly dispersed on the surface of the composite oxide particle. In the present invention, “the surface modifying substance is attached to the surface of the composite oxide particle” means that the surface modifying substance is held in contact with the surface. It may be in a state of being adsorbed or adhered to the surface, or in a state in which the surface modifying substance is chemically bonded to the surface.
　次に、複合酸化物粒子を調製する方法及び該粒子に表面修飾物質を付着させる方法、すなわち本発明の正極活物質を製造する方法について説明する。 Next, a method for preparing composite oxide particles and a method for attaching a surface modifier to the particles, that is, a method for producing a positive electrode active material of the present invention will be described.
　複合酸化物粒子を調製する方法は特に限定されない。例えば、リチウム源となるリチウム化合物、ナトリウム源となるナトリウム化合物、コバルト源となるコバルト化合物、アルミニウム源となるアルミニウム化合物、マグネシウム源となるマグネシウム化合物、及びＭ源となるＭ含有化合物を混合し、得られた混合物を焼成して、複合酸化物粒子を調製できる。 The method for preparing the composite oxide particles is not particularly limited. For example, a lithium compound as a lithium source, a sodium compound as a sodium source, a cobalt compound as a cobalt source, an aluminum compound as an aluminum source, a magnesium compound as a magnesium source, and an M-containing compound as an M source are obtained. The resulting mixture can be fired to prepare composite oxide particles.
　リチウム化合物としては、例えば、水酸化リチウム、塩化リチウム、硝酸リチウム、炭酸リチウム、硫酸リチウム等の無機塩や、蟻酸リチウム、酢酸リチウム、蓚酸リチウム等の有機塩が挙げられる。 Examples of the lithium compound include inorganic salts such as lithium hydroxide, lithium chloride, lithium nitrate, lithium carbonate, and lithium sulfate, and organic salts such as lithium formate, lithium acetate, and lithium oxalate.
　ナトリウム化合物としては、例えば、水酸化ナトリウム、塩化ナトリウム、硝酸ナトリウム、炭酸ナトリウム、硫酸ナトリウム等の無機塩や、蟻酸ナトリウム、酢酸ナトリウム、蓚酸ナトリウム等の有機塩が挙げられる。 Examples of the sodium compound include inorganic salts such as sodium hydroxide, sodium chloride, sodium nitrate, sodium carbonate, and sodium sulfate, and organic salts such as sodium formate, sodium acetate, and sodium oxalate.
　コバルト化合物としては、例えば、酸化物、水酸化物、炭酸塩、オキシ水酸化物等が挙げられる。好ましくはコバルト酸化物が用いられる。正極活物質の形状はコバルト化合物の形状に影響される。従って、コバルト化合物を球状又は楕円球状とし、その粒径や粒度分布等を調整することによって、正極活物質の形状を制御することができる。 Examples of the cobalt compound include oxides, hydroxides, carbonates, oxyhydroxides, and the like. Cobalt oxide is preferably used. The shape of the positive electrode active material is affected by the shape of the cobalt compound. Therefore, the shape of the positive electrode active material can be controlled by making the cobalt compound spherical or elliptical and adjusting the particle size, particle size distribution, and the like.
　アルミニウム化合物としては、例えば、水酸化アルミニウム、塩化アルミニウム、酸化アルミニウム、炭酸アルミニウム、硝酸アルミニウム、硫酸アルミニウム、蟻酸アルミニウム等が挙げられる。 Examples of the aluminum compound include aluminum hydroxide, aluminum chloride, aluminum oxide, aluminum carbonate, aluminum nitrate, aluminum sulfate, and aluminum formate.
　マグネシウム化合物としては、例えば、水酸化マグネシウム、炭酸マグネシウム、塩化マグネシウム、過酸化マグネシウム、酸化マグネシウム、硝酸マグネシウム、酢酸マグネシウム、硫酸マグネシウム等が挙げられる。 Examples of the magnesium compound include magnesium hydroxide, magnesium carbonate, magnesium chloride, magnesium peroxide, magnesium oxide, magnesium nitrate, magnesium acetate, magnesium sulfate and the like.
　Ｍ含有化合物としては、例えば、Ｍを含有する酸化物、水酸化物、炭酸塩、硫酸塩、硝酸塩、ハロゲン化物等が挙げられる。選択される元素によっては、Ｍ含有化合物はＭを含有するガスであってもよい。 Examples of the M-containing compound include M-containing oxides, hydroxides, carbonates, sulfates, nitrates, halides, and the like. Depending on the element selected, the M-containing compound may be a gas containing M.
　上記調製方法では、まず、リチウム化合物、ナトリウム化合物、コバルト化合物、アルミニウム化合物、マグネシウム化合物、及びＭ含有化合物をそれぞれ所定量秤量して混合する。混合はボールミル等を用いる公知の方法により行うことができるが、分散性を高めるために高速攪拌型ミキサーを用いて行うことが好ましい。 In the above preparation method, first, a predetermined amount of each of a lithium compound, a sodium compound, a cobalt compound, an aluminum compound, a magnesium compound, and an M-containing compound is weighed and mixed. Mixing can be performed by a known method using a ball mill or the like, but it is preferable to use a high-speed stirring mixer to improve dispersibility.
　次いで、得られた混合物を焼成する。焼成は台車炉、キルン炉、メッシュベルト炉等を用いて公知の方法により行うことができる。焼成温度は９５０～１０５０℃であってよく、好ましくは１０３０～１０５０℃である。焼成時間は１～２４時間であってよい。この焼成温度よりも低温で仮焼成した後、当該焼成温度まで昇温して本焼成してもよい。また、本焼成後に焼成温度より低い温度で焼鈍してもよい。仮焼成及び焼鈍は、５００～８００℃で３０分～６時間程度行うことが好ましい。 Next, the obtained mixture is fired. Firing can be performed by a known method using a cart furnace, a kiln furnace, a mesh belt furnace, or the like. The calcination temperature may be 950 to 1050 ° C., preferably 1030 to 1050 ° C. The firing time may be 1 to 24 hours. After pre-baking at a temperature lower than this baking temperature, the main baking may be performed by raising the temperature to the baking temperature. Moreover, you may anneal at temperature lower than baking temperature after this baking. Pre-baking and annealing are preferably performed at 500 to 800 ° C. for about 30 minutes to 6 hours.
　上述のようにリチウム源、ナトリウム源、コバルト源、アルミニウム源、マグネシウム源、及びＭ源としてそれぞれ別々の化合物を用いてもよいが、複合化合物を用いてもよい。例えば、Ｃｏ、Ａｌ、Ｍｇ、及びＭを共沈法等により複合化して複合化合物を調製し、これをリチウム化合物及びナトリウム化合物と混合し、得られた混合物を焼成する方法も好ましく行われる。 As described above, separate compounds may be used as the lithium source, sodium source, cobalt source, aluminum source, magnesium source, and M source, but composite compounds may also be used. For example, a method in which Co, Al, Mg, and M are combined by a coprecipitation method to prepare a composite compound, which is mixed with a lithium compound and a sodium compound, and the resulting mixture is fired is also preferably performed.
　例えば、溶媒中で上記複合酸化物粒子を表面修飾物質の原料と混合し、得られた混合物をろ過及び焼成することによって、複合酸化物粒子に表面修飾物質を付着させることができる。混合する複合酸化物粒子と表面修飾物質原料の量は、式（１）の組成が得られるように調整すればよい。通常、複合酸化物に対する表面修飾物質原料のモル比は０．０５～０．５０モル％である。当然ながら、このモル比は混合工程での複合酸化物粒子と表面修飾物質原料との比率であって、正極活物質中の複合酸化物粒子と表面修飾物質との比率ではない。焼成工程は２００～７００℃で１～１０時間程度行ってよい。 For example, the surface-modifying substance can be attached to the composite oxide particles by mixing the composite oxide particles with the raw material of the surface-modifying substance in a solvent and filtering and baking the resulting mixture. What is necessary is just to adjust the quantity of the composite oxide particle to mix and the amount of surface modification substance raw material so that the composition of Formula (1) may be obtained. Usually, the molar ratio of the surface modifying material raw material to the composite oxide is 0.05 to 0.50 mol%. Of course, this molar ratio is the ratio of the composite oxide particles and the surface modifying material in the mixing step, and not the ratio of the composite oxide particles and the surface modifying material in the positive electrode active material. The firing step may be performed at 200 to 700 ° C. for about 1 to 10 hours.
　複合酸化物粒子に表面修飾物質を付着させる方法として、より具体的には以下の工程を含む方法が挙げられる。
（工程１）複合酸化物粒子、表面修飾物質の原料、及び水酸化リチウム一水和物（ｐＨ調整剤）をそれぞれ秤量する。
（工程２）水酸化リチウム一水和物を１００ｍＬの純水に溶解させてから、複合酸化物粒子を投入して第一スラリー液を調製する。
（工程３）表面修飾物質原料を１０ｍＬの純水に溶解させて表面修飾物質原料液を調製する。
（工程４）表面修飾物質原料液を第一スラリー液に投入して第二スラリー液を調製する。
（工程５）第二スラリー液を撹拌してｐＨを安定させる。
（工程６）ｐＨを安定化した第二スラリー液をろ過し、得られたケーキ（ろ過物）を純水で洗浄する。
（工程７）洗浄したケーキを焼成することにより、表面修飾物質を複合酸化物粒子の表面に付着させ、正極活物質を得る。 More specifically, a method including the following steps is exemplified as a method of attaching the surface modifying substance to the composite oxide particles.
(Step 1) Each of the composite oxide particles, the raw material of the surface modifying substance, and lithium hydroxide monohydrate (pH adjuster) is weighed.
(Step 2) Lithium hydroxide monohydrate is dissolved in 100 mL of pure water, and then mixed oxide particles are added to prepare a first slurry liquid.
(Step 3) A surface modifying substance raw material solution is prepared by dissolving a surface modifying substance raw material in 10 mL of pure water.
(Step 4) The surface modifying substance raw material liquid is charged into the first slurry liquid to prepare a second slurry liquid.
(Step 5) Stir the second slurry to stabilize the pH.
(Step 6) The second slurry liquid whose pH is stabilized is filtered, and the obtained cake (filtrate) is washed with pure water.
(Step 7) By baking the washed cake, the surface modifying substance is attached to the surface of the composite oxide particles, and a positive electrode active material is obtained.
　正極活物質の製造過程で洗浄を行ってもよい。この洗浄によって複合酸化物の層間に固溶しきれなかったＮａを除去することができ、これにより電解液中に溶出するＮａを減らし、電解液中で発生するリチウムイオンの挿入脱離を阻害する副反応を抑制することができ、Ｎａによる充放電特性の低下を最小限に抑えられる。なお、この洗浄は、該副反応が抑制できるのであれば、表面修飾物質を複合酸化物粒子の表面に付着させる前に行っても後に行ってもよい。 Cleaning may be performed during the manufacturing process of the positive electrode active material. By this washing, Na that could not be completely dissolved between the layers of the composite oxide can be removed, thereby reducing Na eluted in the electrolytic solution and inhibiting insertion / extraction of lithium ions generated in the electrolytic solution. Side reactions can be suppressed, and deterioration of charge / discharge characteristics due to Na can be minimized. In addition, this washing may be performed before or after the surface modifier is attached to the surface of the composite oxide particle as long as the side reaction can be suppressed.
　例えば、表面修飾物質の原料として硝酸アルミニウムを用いる場合、混合工程において、硝酸アルミニウムの少なくとも一部が水酸化アルミニウムへと変換され得る。焼成工程では、焼成温度等の条件に依っては、水酸化アルミニウムから酸化アルミニウムや金属アルミニウム（アルミニウム単体）が生じることがあり、また水酸化アルミニウムの少なくとも一部がそのまま残ることもある。すなわち、この場合、各工程の条件を適宜選択することによって、表面修飾物質として硝酸アルミニウム、水酸化アルミニウム、酸化アルミニウム、及び／又はアルミニウム単体を複合酸化物粒子表面に付着させることができる。特に、アルミニウム単体又はアルミニウム単体と酸化アルミニウムとの組み合わせを複合酸化物粒子表面に付着させるのが好ましい。このように、本発明では、表面修飾物質として一種又は複数の物質を複合酸化物粒子に付着させてよい。複数の物質を付着させる場合は、上記式（１）は、当該複数の物質と複合酸化物粒子との合計の組成を表す。 For example, when aluminum nitrate is used as a raw material for the surface modifying substance, at least a part of the aluminum nitrate can be converted into aluminum hydroxide in the mixing step. In the firing step, depending on conditions such as the firing temperature, aluminum oxide or metal aluminum (aluminum alone) may be generated from aluminum hydroxide, and at least a part of the aluminum hydroxide may remain as it is. That is, in this case, by appropriately selecting the conditions of each step, aluminum nitrate, aluminum hydroxide, aluminum oxide, and / or aluminum simple substance can be attached to the surface of the composite oxide particle as a surface modifier. In particular, it is preferable to attach aluminum alone or a combination of aluminum alone and aluminum oxide to the surface of the composite oxide particles. Thus, in the present invention, one or more substances may be attached to the composite oxide particles as the surface modifying substance. In the case of attaching a plurality of substances, the above formula (1) represents the total composition of the plurality of substances and the composite oxide particles.
　本発明の正極活物質においては、上記製造方法から明らかなように、式（１）の各元素が正極活物質全体にわたって均一に分布しているわけではなく、正極活物質表面では表面修飾物質に含まれる元素の含有割合が高くなる。本発明の正極活物質のこのような構造（元素分布）を文言により一概に特定することは難しいが、当該正極活物質は特別な組成と構造を有し、そのため顕著な効果を示す。 In the positive electrode active material of the present invention, as is apparent from the above production method, each element of the formula (1) is not uniformly distributed over the entire positive electrode active material, and the surface of the positive electrode active material is a surface modifying material. The content ratio of the contained elements increases. Although it is difficult to specify such a structure (element distribution) of the positive electrode active material of the present invention in general terms, the positive electrode active material has a special composition and structure, and thus exhibits a remarkable effect.
　正極活物質の平均粒子径は特に限定されないが、極板に塗布したときに十分な密度を得ることができるよう、２～５０μｍ程度が好ましい。密度向上のため、当該平均粒子径範囲内で平均粒子径が異なる複数の正極活物質を混合してもよい。 The average particle diameter of the positive electrode active material is not particularly limited, but is preferably about 2 to 50 μm so that a sufficient density can be obtained when it is applied to the electrode plate. In order to improve the density, a plurality of positive electrode active materials having different average particle diameters within the average particle diameter range may be mixed.
　次に、本発明の非水電解質二次電池用正極について説明する。本発明の非水電解質二次電池用正極は、上述した本発明の正極活物質を含有する。この正極を非水電解質二次電池に用いると、正極活物質が充電時に安定した結晶構造を示すため、連続充電や高電圧充電による劣化が少なく、高容量及び高容量維持率が達成される。 Next, the positive electrode for a non-aqueous electrolyte secondary battery of the present invention will be described. The positive electrode for a nonaqueous electrolyte secondary battery of the present invention contains the above-described positive electrode active material of the present invention. When this positive electrode is used for a non-aqueous electrolyte secondary battery, the positive electrode active material exhibits a stable crystal structure during charging, so that there is little deterioration due to continuous charging or high voltage charging, and high capacity and high capacity retention are achieved.
　本発明の正極は公知の方法によって作製してよい。例えば、分散媒中で正極活物質と導電剤や結着剤等とを混錬し、得られたスラリーを電極板に塗布し、乾燥、ローラ圧延し、所定の寸法に裁断して、正極を作製できる。本発明の正極活物質を用いた場合、正極活物質、導電剤、結着剤等が均一に分散し、スラリーは適度な流動性を示し、経時変化が少ない。通常、正極の厚さは４０～１２０μｍである。 The positive electrode of the present invention may be produced by a known method. For example, a positive electrode active material and a conductive agent or a binder are kneaded in a dispersion medium, and the resulting slurry is applied to an electrode plate, dried, roller-rolled, cut into a predetermined size, and the positive electrode is Can be made. When the positive electrode active material of the present invention is used, the positive electrode active material, the conductive agent, the binder, and the like are uniformly dispersed, the slurry exhibits appropriate fluidity, and changes with time are small. Usually, the thickness of the positive electrode is 40 to 120 μm.
　正極を作製するための導電剤、結着剤、分散媒、電極板等も公知のものが使用できる。例えば、導電剤としては、天然黒鉛、人造黒鉛、ケッチェンブラック、アセチレンブラック等の炭素質材が挙げられる。結着剤としては、フッ素系樹脂（ポリテトラフルオロエチレンやポリフッ化ビニリデン等）、ポリ酢酸ビニル、ポリメチルメタクリレート、エチレン－プロピレン－ブタジエン共重合体、スチレン－ブタジエン共重合体、アクリロニトリル－ブタジエン共重合体、カルボキシメチルセルロース等が挙げられる。分散媒としては、Ｎ－メチルピロリドン、テトラヒドロフラン、エチレンオキシド、メチルエチルケトン、シクロヘキサノン、酢酸メチル、アクリル酸メチル、ジエチルトリアミン、ジメチルホルムアミド、ジメチルアセトアミド等が挙げられる。 As the conductive agent, binder, dispersion medium, electrode plate, etc. for producing the positive electrode, known ones can be used. Examples of the conductive agent include carbonaceous materials such as natural graphite, artificial graphite, ketjen black, and acetylene black. As binders, fluorine resins (polytetrafluoroethylene, polyvinylidene fluoride, etc.), polyvinyl acetate, polymethyl methacrylate, ethylene-propylene-butadiene copolymer, styrene-butadiene copolymer, acrylonitrile-butadiene copolymer Examples thereof include merging and carboxymethylcellulose. Examples of the dispersion medium include N-methylpyrrolidone, tetrahydrofuran, ethylene oxide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethyltriamine, dimethylformamide, dimethylacetamide and the like.
　電極板としては多孔性や無孔の導電性基板が用いられる。導電性基板の例としては、Ａｌ、Ｃｕ、Ｔｉ、ステンレス等の金属箔が挙げられる。中でもＡｌ箔が好ましく、Ａｌ箔の厚さは１０～３０μｍであるのが好ましい。 As the electrode plate, a porous or non-porous conductive substrate is used. Examples of the conductive substrate include metal foils such as Al, Cu, Ti, and stainless steel. Of these, an Al foil is preferable, and the thickness of the Al foil is preferably 10 to 30 μm.
　続いて、本発明の非水電解質二次電池について説明する。本発明の非水電解質二次電池は、上述した本発明の非水電解質二次電池用正極を有する。本発明の正極を非水電解質二次電池に用いると、正極活物質が充電時に安定した結晶構造を示すため、連続充電や高電圧充電による劣化が少なく、高容量及び高容量維持率が達成される。 Subsequently, the nonaqueous electrolyte secondary battery of the present invention will be described. The nonaqueous electrolyte secondary battery of the present invention has the above-described positive electrode for a nonaqueous electrolyte secondary battery of the present invention. When the positive electrode of the present invention is used for a non-aqueous electrolyte secondary battery, the positive electrode active material exhibits a stable crystal structure during charging, so that there is little deterioration due to continuous charging or high voltage charging, and a high capacity and a high capacity retention rate are achieved. The
　本発明の非水電解質二次電池は、主に電池ケース、正極、負極、有機溶媒、電解質、及びセパレータで構成される。有機溶媒と電解質（電解質溶液）に替えて固体電解質を用いてもよい。負極、有機溶媒、電解質、及びセパレータとしては公知のものが使用できる。 The nonaqueous electrolyte secondary battery of the present invention is mainly composed of a battery case, a positive electrode, a negative electrode, an organic solvent, an electrolyte, and a separator. A solid electrolyte may be used instead of the organic solvent and the electrolyte (electrolyte solution). Known materials can be used as the negative electrode, organic solvent, electrolyte, and separator.
　例えば、負極はＣｕ等の金属箔等からなる集電体上に負極活物質、結着剤、導電剤、及び分散媒等を混合した負極合剤を塗布した後、圧延、乾燥することにより得られる。負極活物質としては、リチウム金属、リチウム合金、アモルファス系炭素人造黒鉛（ソフトカーボン、ハードカーボン等）、炭素質材（天然黒鉛等）等が用いられる。必要に応じ、結着剤及び分散媒等は正極と同様のものが使用される。 For example, the negative electrode is obtained by applying a negative electrode mixture in which a negative electrode active material, a binder, a conductive agent, a dispersion medium, and the like are mixed on a current collector made of a metal foil such as Cu, and then rolling and drying. It is done. As the negative electrode active material, lithium metal, lithium alloy, amorphous carbon artificial graphite (soft carbon, hard carbon, etc.), carbonaceous material (natural graphite, etc.) and the like are used. If necessary, the same binder and dispersion medium as those for the positive electrode are used.
　有機溶媒の種類は特に限定されないが、例えば、カーボネート類（プロピレンカーボネート、エチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネート等）、エーテル類（１，２－ジメトキシプロパン、１，３－ジメトキシプロパン、テトラヒドロフラン、２－メチルテトラヒドロフラン等）、エステル類（酢酸メチル、Γ－ブチロラクトン等）、ニトリル類（アセトニトリル、ブチロニトリル等）、アミド類（Ｎ，Ｎ－ジメチルホルムアミド、Ｎ，Ｎ－ジメチルアセトアミド等）等が挙げられる。これらは単独で用いてもよく、２種以上を組み合わせて用いてもよい。 The type of the organic solvent is not particularly limited. For example, carbonates (propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc.), ethers (1,2-dimethoxypropane, 1,3-dimethoxypropane, Tetrahydrofuran, 2-methyltetrahydrofuran, etc.), esters (methyl acetate, Γ-butyrolactone, etc.), nitriles (acetonitrile, butyronitrile, etc.), amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), etc. Can be mentioned. These may be used alone or in combination of two or more.
　有機溶媒に溶解させる電解質としては、例えば、ＬｉＣｌＯ4、ＬｉＰＦ6、ＬｉＢＦ4、ＬｉＡｌＣｌ4、ＬｉＳｂＦ6、ＬｉＳＣＮ、ＬｉＣＦ3ＳＯ3、ＬｉＣＦ3ＣＯ2、Ｌｉ（ＣＦ3ＳＯ2）2、ＬｉＡｓＦ6、ＬｉＢ10Ｃｌ10、低級脂肪族カルボン酸リチウム、テトラクロロホウ素酸リチウム、テトラフェニルホウ素酸リチウム、イミド類等が挙げられる。これらは単独で用いてもよく、２種以上を組み合わせて用いてもよい。 Examples of the electrolyte dissolved in the organic solvent include LiClO 4 , LiPF 6 , LiBF 4 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCF 3 SO 3 , LiCF 3 CO 2 , Li (CF 3 SO 2 ) 2 , LiAsF 6 , Examples include LiB 10 Cl 10 , lower aliphatic lithium carboxylate, lithium tetrachloroborate, lithium tetraphenylborate, and imides. These may be used alone or in combination of two or more.
　固体電解質としては、例えば、高分子電解質（ポリエチレンオキサイド系電解質等）、硫化物系電解質（Ｌｉ2Ｓ－ＳｉＳ2、Ｌｉ2Ｓ－Ｐ2Ｓ5、Ｌｉ2Ｓ－Ｂ2Ｓ3等）等が挙げられる。また、高分子に非水電解質溶液を保持させた、いわゆるゲルタイプの電解質を用いることもできる。 Examples of solid electrolytes include polymer electrolytes (polyethylene oxide electrolytes, etc.), sulfide electrolytes (Li 2 S—SiS 2 , Li 2 SP—S 2 S 5 , Li 2 S—B 2 S 3 etc.), etc. Is mentioned. A so-called gel type electrolyte in which a nonaqueous electrolyte solution is held in a polymer can also be used.
　セパレータとしては、例えば、高いイオン透過度、所定の機械的強度、及び電子絶縁性を有する微多孔性薄膜を用いるのが好ましい。電解質に対する耐性と疎水性に優れていることから、例えば、ポリエチレン、ポリプロピレン、ポリフェニレンスルフィド、ポリエチレンテレフタレート、ポリアミド、ポリイミド等の材質からなる微多孔性薄膜の使用が好ましい。これらの材質は、単独で用いても、複数を組み合わせて用いても良い。製造コストの観点からは、安価なポリプロピレン等を用いることが好ましい。 As the separator, for example, a microporous thin film having high ion permeability, predetermined mechanical strength, and electronic insulation is preferably used. For example, it is preferable to use a microporous thin film made of a material such as polyethylene, polypropylene, polyphenylene sulfide, polyethylene terephthalate, polyamide, or polyimide because of its excellent resistance to electrolyte and hydrophobicity. These materials may be used alone or in combination. From the viewpoint of manufacturing cost, it is preferable to use inexpensive polypropylene or the like.
　本発明の非水電解質二次電池の形状は、円筒型、積層型、コイン型等の種々の形状から選択できる。いずれの形状であっても、上述の構成要素を電池ケースに収納し、正極及び負極から正極端子及び負極端子までの間を集電用リード等で接続し、電池ケースを密閉する。 The shape of the nonaqueous electrolyte secondary battery of the present invention can be selected from various shapes such as a cylindrical shape, a laminated shape, and a coin shape. Regardless of the shape, the above-described components are housed in the battery case, and the space between the positive electrode and the negative electrode to the positive electrode terminal and the negative electrode terminal is connected with a current collecting lead or the like, and the battery case is sealed.
　以下、実施例及び比較例により本発明を詳細に説明するが、本発明はこれらに限定されない。 Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
実施例１
（正極活物質の製造）
　最終的に得られる正極活物質が表１に示す組成を有するように、炭酸リチウム、炭酸ナトリウム、酸化コバルト、水酸化アルミニウム、水酸化マグネシウム、酸化チタン、及び酸化ジルコニウムをそれぞれ秤量し、高速撹拌ミキサーを用いて混合し、混合物を得た。 Example 1
(Manufacture of positive electrode active material)
Lithium carbonate, sodium carbonate, cobalt oxide, aluminum hydroxide, magnesium hydroxide, titanium oxide, and zirconium oxide were weighed so that the positive electrode active material finally obtained had the composition shown in Table 1, and a high-speed stirring mixer To obtain a mixture.
　次に、箱型の電気炉を用いて混合物を７００℃で４時間仮焼した後、１０３０℃で５時間焼成を行い、複合酸化物を得た。 Next, the mixture was calcined at 700 ° C. for 4 hours using a box-type electric furnace, and then baked at 1030 ° C. for 5 hours to obtain a composite oxide.
　１００ｇの複合酸化物、０．３８３ｇの硝酸アルミニウム九水和物（和光純薬工業株式会社製、一級、表面修飾物質の原料として使用）、及び０．１２９ｇの水酸化リチウム一水和物（和光純薬工業株式会社製、特級、ｐＨ調整剤として使用）をそれぞれ秤量した。複合酸化物に対する硝酸アルミニウム九水和物のモル比は０．１モル％であり、水酸化リチウム一水和物のモル比は０．３モル％に相当する。 100 g of complex oxide, 0.383 g of aluminum nitrate nonahydrate (manufactured by Wako Pure Chemical Industries, Ltd., used as a raw material for primary and surface modifying substances), and 0.129 g of lithium hydroxide monohydrate (Japanese sum) Koshu Pure Chemical Industries, Ltd., special grade, used as a pH adjuster) were weighed. The molar ratio of aluminum nitrate nonahydrate to the composite oxide is 0.1 mol%, and the molar ratio of lithium hydroxide monohydrate corresponds to 0.3 mol%.
　水酸化リチウム一水和物を１００ｍＬの純水に溶解させ、これに複合酸化物を投入して第一スラリー液を作製した。一方で硝酸アルミニウム九水和物を１０ｍＬの純水に溶解させて表面修飾物質原料液を作製した。表面修飾物質原料液を、ピペッターを用いて５ｍＬ／分の速度で第一スラリー液に投入した後、５分間以上撹拌し、ｐＨが１０．７付近で安定したことを確認して、第二スラリー液を得た。 Lithium hydroxide monohydrate was dissolved in 100 mL of pure water, and a composite oxide was added thereto to prepare a first slurry liquid. On the other hand, aluminum nitrate nonahydrate was dissolved in 10 mL of pure water to prepare a surface modifying material raw material liquid. After the surface modifier material liquid is put into the first slurry liquid at a rate of 5 mL / min using a pipetter, it is stirred for 5 minutes or more, and it is confirmed that the pH is stable at around 10.7, and then the second slurry. A liquid was obtained.
　第二スラリー液をろ過し、得られたケーキを２００ｍＬの純水で洗浄した。洗浄したケーキを昇温速度５℃／分で５００℃まで加熱し、５００℃に達してから３時間焼成して、表１に示す組成を有する正極活物質を得た。この正極活物質は、複合酸化物粒子とその表面に付着したＡｌ含有表面修飾物質とからなる。 The second slurry was filtered, and the resulting cake was washed with 200 mL of pure water. The washed cake was heated to 500 ° C. at a temperature rising rate of 5 ° C./min, and baked for 3 hours after reaching 500 ° C. to obtain a positive electrode active material having the composition shown in Table 1. This positive electrode active material is composed of composite oxide particles and an Al-containing surface modifier adhering to the surface.
（電池の製造）
　得られた正極活物質、グラファイト及びアセチレンブラック（導電剤）、並びにポリフッ化ビニリデン（結着剤）を、２００：４：１：１０の質量比で混合し、Ｎ－メチルピロリドン中で混練して、電極スラリーを得た。この電極スラリーを厚さ２０μｍのアルミニウム箔に塗布し、乾燥後、プレス機で厚さ４０μｍに加圧成型し、所定の寸法に裁断し、端子をスポット溶接して、正極を製造した。 (Manufacture of batteries)
The obtained positive electrode active material, graphite and acetylene black (conductive agent), and polyvinylidene fluoride (binder) were mixed at a mass ratio of 200: 4: 1: 10 and kneaded in N-methylpyrrolidone. An electrode slurry was obtained. This electrode slurry was applied to an aluminum foil having a thickness of 20 μm, dried, press-molded to a thickness of 40 μm with a press machine, cut into a predetermined size, and terminals were spot welded to produce a positive electrode.
　上記のとおり製造した正極を用いて、試験用コインセル二次電池を次のように作製した。対極（負極）として金属リチウム箔を用い、試験極として上記正極を用い、セパレータを介してこれらを電池ケース内に配置した。その中に電解液を注入してコインセル二次電池を製造した。なお、電解液は、エチレンカーボネート（ＥＣ）とジメチルカーボネート（ＤＭＣ）との１：２（体積比）の混合溶媒中に、支持電解質のＬｉＰＦ6を１Ｍ濃度で溶解させて調製した。 Using the positive electrode produced as described above, a test coin cell secondary battery was produced as follows. Metal lithium foil was used as a counter electrode (negative electrode), the positive electrode was used as a test electrode, and these were arranged in a battery case via a separator. A coin cell secondary battery was manufactured by injecting an electrolytic solution therein. The electrolytic solution was prepared by dissolving LiPF 6 as a supporting electrolyte at a concentration of 1M in a 1: 2 (volume ratio) mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC).
（充放電試験）
　製造したコインセル二次電池を用いて、以下のとおり充放電試験を行った。
（１）測定温度を２５℃とし、１サイクル目及び２サイクル目は、充電上限電圧４．５５Ｖ、放電下限電圧３．０Ｖ、電流密度０．３ｍＡ／ｃｍ2の条件で充放電を行った。
（２）３サイクル目以降は、充電上限電圧４．５５Ｖ、放電下限電圧３．０Ｖ、電流密度１．５ｍＡ／ｃｍ2の条件で充放電を行った。
（３）充放電電流０．３ｍＡ／ｃｍ2においての充電容量及び放電容量、並びに充放電電流１．５ｍＡ／ｃｍ2においての２２サイクル後の容量維持率を測定した。この容量維持率は下記式によって求めた。
　容量維持率（％）＝（２２サイクル目の放電容量／３サイクル目の放電容量）×１００
　１サイクル目の放電容量及び容量維持率を表１に示す。 (Charge / discharge test)
A charge / discharge test was performed as follows using the manufactured coin cell secondary battery.
(1) The measurement temperature was 25 ° C., and in the first and second cycles, charging and discharging were performed under the conditions of a charge upper limit voltage 4.55 V, a discharge lower limit voltage 3.0 V, and a current density of 0.3 mA / cm 2 .
(2) From the third cycle onward, charging / discharging was performed under the conditions of a charge upper limit voltage of 4.55 V, a discharge lower limit voltage of 3.0 V, and a current density of 1.5 mA / cm 2 .
(3) were measured charge capacity and discharge capacity, and capacity retention after 22 cycles of the charge and discharge current 1.5 mA / cm 2 of the charge and discharge current 0.3 mA / cm 2. This capacity retention rate was determined by the following formula.
Capacity retention rate (%) = (discharge capacity at 22nd cycle / discharge capacity at 3rd cycle) × 100
Table 1 shows the discharge capacity and capacity retention rate of the first cycle.
実施例２～６及び比較例１～１８
　原料化合物の配合を変更して最終的に表１に示す組成を得たこと以外は実施例１と同様に、実施例２～６及び比較例１～１８の正極活物質をそれぞれ製造した。なお、マンガン源としては硫酸マンガン（ＩＩ）五水和物を使用した。各正極活物質を用いて実施例１と同様にコインセル二次電池を作製し、充放電試験を行った。結果を表１に示す。 Examples 2 to 6 and Comparative Examples 1 to 18
Cathode active materials of Examples 2 to 6 and Comparative Examples 1 to 18 were produced in the same manner as in Example 1 except that the composition of the raw material compounds was changed and the compositions shown in Table 1 were finally obtained. In addition, manganese sulfate (II) pentahydrate was used as a manganese source. A coin cell secondary battery was produced using each positive electrode active material in the same manner as in Example 1, and a charge / discharge test was performed. The results are shown in Table 1.
[規則26に基づく補充 21.08.2017]　
Figure WO-DOC-TABLE-1
 [Supplement under rule 26 21.08.2017]
Figure WO-DOC-TABLE-1
　表１に示すように、実施例１～６では、各元素の組成比、特にＬｉ含有割合、Ｎａ含有割合、並びにＬｉ及びＮａの他の元素に対するモル比を特定範囲内に制御した。その結果、４．５５Ｖの高電圧充電による上記充放電試験において、１８９．０ｍＡｈ／ｇ以上という十分な放電容量と９０％以上という優れた容量維持率との両方を示す正極活物質が得られた。 As shown in Table 1, in Examples 1 to 6, the composition ratio of each element, particularly the Li content ratio, the Na content ratio, and the molar ratio of Li and Na to other elements were controlled within a specific range. As a result, a positive electrode active material having both a sufficient discharge capacity of 189.0 mAh / g or more and an excellent capacity maintenance rate of 90% or more was obtained in the above charge / discharge test by high voltage charge of 4.55V. .

Claims (8)

  1. 　リチウム含有複合酸化物粒子と該粒子の表面に付着した表面修飾物質とからなり、
    　下記式（１）：
    　　　　　Ｌｉx-yＮａyＣｏwＡｌaＭｇbＭcＯ2+α　・・・（１）
    ［式（１）中、ｘ、ｙ、ｗ、ａ、ｂ、ｃ、及びαは、式０．９８６≦（ｘ－ｙ）＜１．０５０、０＜ｙ≦０．０２０、０．９９６≦ｘ≦１．０５０、０．９９０≦ｗ≦１．０１５、０．００５≦ａ≦０．０２０、０．００１≦ｂ≦０．０２０、０．０００５≦ｃ≦０．００５、及び－０．１≦α≦０．１を満たし、（Ｌｉ＋Ｎａ）と（Ｃｏ＋Ａｌ＋Ｍｇ＋Ｍ）との比（ｘ）／（ｗ＋ａ＋ｂ＋ｃ）が０．９３０以上０．９９０未満であり、ＭはＣａ、希土類元素、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗ、Ｍｎ、Ｆｅ、Ｎｉ、Ｃｕ、Ａｇ、Ｚｎ、Ｂ、Ｇａ、Ｃ、Ｓｉ、Ｓｎ、Ｎ、Ｐ、Ｓ、Ｆ、Ｃｌ、及びＨから選ばれる１種以上の元素を示す。］で表される組成を有し、
    　前記表面修飾物質がＡｌ、Ｍｇ、及びＭから選ばれる１種以上の元素を含む、
    　非水電解質二次電池用正極活物質。     Consisting of lithium-containing composite oxide particles and a surface modifying substance attached to the surface of the particles,
    Following formula (1):
    Li xy Na y Co w Al a Mg b M c O 2+ α ··· (1)
    [In the formula (1), x, y, w, a, b, c, and α are the formulas 0.986 ≦ (xy) <1.050, 0 <y ≦ 0.020, 0.996 ≦ x ≦ 1.050, 0.990 ≦ w ≦ 1.015, 0.005 ≦ a ≦ 0.020, 0.001 ≦ b ≦ 0.020, 0.0005 ≦ c ≦ 0.005, and −0. 1 ≦ α ≦ 0.1 is satisfied, and the ratio (x) / (w + a + b + c) of (Li + Na) to (Co + Al + Mg + M) is 0.930 or more and less than 0.990, and M is Ca, rare earth element, Ti, Zr, Selected from Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P, S, F, Cl, and H One or more elements. And a composition represented by
    The surface modifier contains one or more elements selected from Al, Mg, and M;
    Positive electrode active material for non-aqueous electrolyte secondary battery.
  2. 　前記リチウム含有複合酸化物粒子がＬｉ、Ｎａ、Ｃｏ、及びＯを含み、更にＡｌ、Ｍｇ、Ｃａ、希土類元素、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗ、Ｍｎ、Ｆｅ、Ｎｉ、Ｃｕ、Ａｇ、Ｚｎ、Ｂ、Ｇａ、Ｃ、Ｓｉ、Ｓｎ、Ｎ、Ｐ、Ｓ、Ｆ、Ｃｌ、及びＨから選ばれる１種以上の任意元素を含んでいてもよい、請求項１に記載の非水電解質二次電池用正極活物質。 The lithium-containing composite oxide particles contain Li, Na, Co, and O, and Al, Mg, Ca, rare earth elements, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe 1 or more elements selected from Ni, Cu, Ag, Zn, B, Ga, C, Si, Sn, N, P, S, F, Cl, and H may be included. The positive electrode active material for nonaqueous electrolyte secondary batteries as described in 2.
  3. 　前記表面修飾物質がＡｌ、Ｍｇ、Ｃａ、希土類元素、Ｔｉ、Ｚｒ、Ｈｆ、Ｖ、Ｎｂ、Ｔａ、Ｃｒ、Ｍｏ、Ｗ、Ｍｎ、Ｆｅ、Ｎｉ、Ｃｕ、Ａｇ、Ｚｎ、Ｂ、Ｇａ、Ｓｉ、及びＳｎから選ばれる１種以上の元素を含み、更にＬｉ、Ｎａ、Ｃｏ、Ｏ、Ｃ、Ｎ、Ｐ、Ｓ、Ｆ、Ｃｌ、及びＨから選ばれる１種以上の任意元素を含んでいてもよい、請求項１又は２に記載の非水電解質二次電池用正極活物質。 The surface modifying material is Al, Mg, Ca, rare earth element, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ni, Cu, Ag, Zn, B, Ga, Si, And one or more elements selected from Sn, and one or more optional elements selected from Li, Na, Co, O, C, N, P, S, F, Cl, and H. The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 1 or 2, which is good.
  4. 　ｘ及びｙが式０．９８６≦（ｘ－ｙ）≦１．００３を満たす、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用正極活物質。 The positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein x and y satisfy a formula 0.986 ≦ (xy) ≦ 1.003.
  5. 　ｘ及びｙが式０．９８６≦（ｘ－ｙ）≦０．９９０を満たす、請求項４に記載の非水電解質二次電池用正極活物質。 The positive electrode active material for a nonaqueous electrolyte secondary battery according to claim 4, wherein x and y satisfy the formula 0.986 ≦ (xy) ≦ 0.990.
  6. 　（Ｌｉ＋Ｎａ）と（Ｃｏ＋Ａｌ＋Ｍｇ＋Ｍ）との比（ｘ）／（ｗ＋ａ＋ｂ＋ｃ）が０．９６０以上０．９８０以下である、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用正極活物質。 6. The positive electrode for a non-aqueous electrolyte secondary battery according to claim 1, wherein the ratio (x) / (w + a + b + c) of (Li + Na) to (Co + Al + Mg + M) is 0.960 or more and 0.980 or less. Active material.
  7. 　請求項１～６のいずれか一項に記載の非水電解質二次電池用正極活物質を含有する、非水電解質二次電池用正極。 A positive electrode for a non-aqueous electrolyte secondary battery comprising the positive electrode active material for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6.
  8. 　請求項７に記載の非水電解質二次電池用正極を備えた、非水電解質二次電池。 A non-aqueous electrolyte secondary battery comprising the positive electrode for a non-aqueous electrolyte secondary battery according to claim 7.
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