Abstract: Provided is a method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries, the method including: a mixing step of obtaining a W-containing mixture of Li-metal composite oxide particles represented by the formula: LizNi1-x-yCoxMyO2 and composed of primary particles and secondary particles formed by aggregation of the primary particles, 2 mass % or more of water with respect to the oxide particles, and a W compound or a W compound and a Li compound, the W-containing mixture having a molar ratio of the total amount of Li contained in the water and the solid W compound, or the W compound and the Li compound of 1.5 or more and less than 3.0 with respect to the amount of W contained therein; and a heat treatment step of heating the W-containing mixture to form lithium tungstate on the surface of the primary particles.

Abstract: Provided is a method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries, the method including: a mixing step of obtaining a W-containing mixture of Li metal composite oxide particles represented by the formula: LizNi1-x-yCOxMyO2 and composed of primary particles and secondary particles formed by aggregation of the primary particles, 2 mass % or more of water with respect to the oxide particles, and a W compound or a W compound and a Li compound, the W-containing mixture having a molar ratio of the total amount of Li contained in water and the solid W compound or the W compound and the Li compound of 3 to 5 with respect to the amount of W contained therein; and a heat treatment step of heating the W-containing mixture to form lithium tungstate on the surface of the primary particles of the Li metal composite oxide particles.

Abstract: Provided is a positive electrode active material for nonaqueous electrolyte secondary batteries that is represented by the general formula (1): LiaNi1-x-yCoxMyWzO2+? (where 0?x?0.35, 0?y?0.35, 0.0008?z?0.030, 0.97?a?1.25, and 0???0.20, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti, and Al) and is constituted by a Li-metal composite oxide composed of primary particles and secondary particles formed by aggregation of the primary particles, wherein a compound including Li and W is formed on the surface of the primary particles of the composite oxide and the amount of W contained in the compound is such that the number of atoms of W is 0.08 to 0.30 at % with respect to the total number of atoms of Ni, Co, and M contained in the positive electrode active material.

Abstract: Provided is a method for producing the positive electrode active material for nonaqueous electrolyte secondary batteries, including a first step of mixing a Li-metal composite oxide powder which is represented by the general formula: LizNi1-x-yCoxMyO2 (where 0?x?0.35, 0?y?0.35, and 0.97?z?1.30 are satisfied, and M is at least one element selected from Mn, V, Mg, Mo, Nb, Ti and Al) and constituted by primary particles and secondary particles, to an alkaline solution with a W compound dissolved therein, and immersing a resulting mixture, followed by solid-liquid separation, to obtain a W mixture with W uniformly dispersed on the surface of the primary particles of the composite oxide, and a second step of heat-treating the W mixture to thereby form a compound containing W and Li on the surface of the primary particles of the composite oxide powder.

Abstract: A method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries, includes: a mixing step of adding a W compound powder having a solubility A adjusted to 2.0 g/L or less to a Li-metal composite oxide powder and stirring in water washing of the composite oxide powder, the solubility A being determined by stirring the W compound in water having a pH of 12.5 at 25° C. for 20 minutes, the composite oxide powder being represented by the formula: LicNi1-x-yCoxMyO2 and composed of primary and secondary particles, followed by solid-liquid separation, to thereby obtain a tungsten-containing mixture with the tungsten compound dispersed in the composite oxide powder; and a heat-treating step of heat-treating the mixture to uniformly disperse W on the surface of primary particles and thereby form a compound containing W and Li from the W and Li in the mixture, on the surface of primary particles.

Abstract: Provided is a method for producing a positive electrode active material for nonaqueous electrolyte secondary batteries, including: a water-washing step of mixing, with water, Li—Ni composite oxide particles represented by the formula: LizNi1-x-yCoxMyO2 and composed of primary particles and secondary particles formed by aggregation of the primary particles to water-wash it, and performing solid-liquid separation to obtain a washed cake; a mixing step of mixing a W compound powder free from Li with the washed cake to obtain a W-containing mixture; and a heat treatment step of heating the W-containing mixture, the heat treatment step including: a first heat treatment step of heating the W-containing mixture to disperse W on the surface of the primary particles; and subsequently, a second heat treatment step of heating it at a higher temperature than in the first heat treatment step to form a lithium tungstate compound on the surface of the primary particles.

Abstract: A positive electrode active material for a non-aqueous electrolyte secondary battery, including primary particles of a lithium nickel composite oxide represented by the formula: LibNi1-x-yCoxMyO2 wherein M represents at least one element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo; b represents a number satisfying 0.95?b?1.03; and x represents a number satisfying 0<x?0.15 and y represents a number satisfying 0<y?0.07, wherein the sum total of x and y is 0.16 or smaller, i.e., x+y?0.16) and secondary particles that are aggregates of the primary particles, wherein microparticles containing W and Li are present on the surface of each of the primary particles, and the length of axis-c of the lithium nickel composite oxide is 14.183 angstroms or more as determined by a Rietveld analysis of X-ray diffraction data on the oxide.