Lithium nickel manganese composite oxide, positive electrode active material for lithium secondary battery, lithium secondary battery, and method of producing lithium nickel manganese composite oxide

Abstract

The present invention relates to a lithium nickel manganese composite oxide which includes secondary particles in which a plurality of primary particles are aggregated with each other, and is represented by General Formula (1): LixNiyMnzO2 (in Formula (1), x is 0.95≤x≤1.1, y is 0.45≤y≤0.5, z is 0.45≤z≤0.5, and y=z is satisfied), wherein Li contained in a transition metal layer does not form LiMn6, wherein the lithium nickel manganese composite oxide has a manganese-rich layer from a surface of the secondary particles toward an inside of the secondary particles, wherein a ratio of a number of Mn atoms to a number of Ni atoms (Mn/Ni ratio) in the manganese-rich layer is 1.0 or more and 1.5 or less, and wherein the lithium nickel manganese composite oxide has a space group R-3m, an a-axis lattice constant of 2.87 Å to 2.90 Å, and a c-axis lattice constant of 14.28 Å to 14.32 Å.

Dependencies are inferred from the claim text.