Abstract: A positive electrode active material for a lithium ion secondary battery, the positive electrode active material including a lithium-nickel composite oxide having a hexagonal layered structure and configured by single primary particles or by single primary particles and secondary particles with a plurality of aggregated primary particles, wherein a number proportion of the single primary particles to all of the particles is 30% or more, a ratio of a (003) diffraction peak intensity I(003) to a (104) diffraction peak intensity I(104) (I(003)/I(104)) is 2.0 or more, and a degree of circularity is 0.93 or more and 1.00 or less.

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, 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 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 nonaqueous electrolyte secondary batteries has a high charge/discharge capacity and produces high output, as well as has high filling ability. The positive electrode active material includes lithium-nickel composite oxide particles are formed by agglomeration of multiple primary particles, include pores, and have a layered crystal structure. The lithium-nickel composite oxide particles have an average particle size of 15 ?m or more and 30 ?m or less. The percentage of an area of the pores measured by a cross-sectional observation of the lithium-nickel composite oxide particles with respect to a cross-sectional area of the lithium-nickel composite oxide particles is 1.0% or more and 5.0% or less. A lithium-tungsten compound containing tungsten and lithium is present on the surface of and inside the secondary particles. The lithium-tungsten compound is present on at least part of the surface of the primary particles.

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: 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: A positive electrode active material for a nonaqueous electrolyte secondary battery is provided, which can establish both high capacity and high output when used for a positive electrode material. A positive electrode active material for a nonaqueous electrolyte secondary battery comprises primary particles of a lithium-nickel composite oxide represented by the following general formula (1) and secondary particles composed by aggregation of the primary particles, wherein a 1-nm to 200-nm thick film containing W and Li is present on the surface of the primary particles, and a c-axis length in the LiNi composite oxide crystal ranges from 14.183 to 14.205 angstroms. General formula: LibNi1-x-yCoxMyO2??(1) (In the formula, M is at least one type of element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo, and 0.95?b?1.03, 0<x?0.15, 0<y?0.07, and x+y?0.16 are satisfied.

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 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 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: In one aspect, a method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery, includes mixing first lithium nickel composite oxide particles containing lithium tungstate and second lithium nickel composite oxide particles not containing lithium tungstate. The first lithium nickel composite oxide particles have a composition represented by Liz1Ni1-x1-y1Cox1M1y1O2, and include a core material containing secondary particles each corresponding to an aggregation of a plurality of primary particles, and the lithium tungstate existing on at least a part of a surface of the primary particles on a surface of and inside the first lithium nickel composite oxide particles. The second lithium nickel composite oxide particles have a composition represented by Liz2Ni1-x2-y2Cox2M2y2O2, and include secondary particles each corresponding to an aggregation of a plurality of 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 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, 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: 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 nonaqueous electrolyte secondary batteries has a high charge/discharge capacity and produces high output, as well as has high filling ability. The positive electrode active material includes lithium-nickel composite oxide particles are formed by agglomeration of multiple primary particles, include pores, and have a layered crystal structure. The lithium-nickel composite oxide particles have an average particle size of 15 ?m or more and 30 ?m or less. The percentage of an area of the pores measured by a cross-sectional observation of the lithium-nickel composite oxide particles with respect to a cross-sectional area of the lithium-nickel composite oxide particles is 1.0% or more and 5.0% or less. A lithium-tungsten compound containing tungsten and lithium is present on the surface of and inside the secondary particles. The lithium-tungsten compound is present on at least part of 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.

Abstract: A positive electrode active material for a nonaqueous electrolyte secondary battery is provided, which can establish both high capacity and high output when used for a positive electrode material. A positive electrode active material for a nonaqueous electrolyte secondary battery comprises primary particles of a lithium-nickel composite oxide represented by the following general formula (1) and secondary particles composed by aggregation of the primary particles, wherein a 1-nm to 200-nm thick film containing W and Li is present on the surface of the primary particles, and a c-axis length in the LiNi composite oxide crystal ranges from 14.183 to 14.205 angstroms. General formula: LibNi1-x-yCoxMyO2??(1) (In the formula, M is at least one type of element selected from Mg, Al, Ca, Ti, V, Cr, Mn, Nb, Zr and Mo, and 0.95?b?1.03, 0<x?0.15, 0<y?0.07, and x+y?0.16 are satisfied.

Abstract: In one aspect, a method for producing a positive electrode active material for a nonaqueous electrolyte secondary battery, includes mixing first lithium nickel composite oxide particles containing lithium tungstate and second lithium nickel composite oxide particles not containing lithium tungstate. The first lithium nickel composite oxide particles have a composition represented by Liz1Ni1-x1-y1Cox1M1y1O2, and include a core material containing secondary particles each corresponding to an aggregation of a plurality of primary particles, and the lithium tungstate existing on at least a part of a surface of the primary particles on a surface of and inside the first lithium nickel composite oxide particles. The second lithium nickel composite oxide particles have a composition represented by Liz2Ni1-x2-y2Cox2M2y2O2, and include secondary particles each corresponding to an aggregation of a plurality of primary particles.