POSITIVE ELECTRODE ACTIVE SUBSTANCE FOR LITHIUM ION BATTERIES, POSITIVE ELECTRODE FOR LITHIUM ION BATTERIES, AND LITHIUM ION BATTERY

The present invention provides a positive electrode active material for lithium ion battery which has a high capacity and good rate characteristics can be provided. The positive electrode active material for lithium ion battery has a layer structure represented by the compositional formula: Li(NiM)O(wherein M represents at least one type selected from the group consisting of Mn, Co, Al, Mg, Cr, Ti, Fe, Nb, Cu and Zr, x denotes a number from 0.9 to 1.2, y denotes a number from 0.5 to 0.6, and z denotes a number of 1.9 or more), wherein the coordinates of the lattice constant a and compositional ratio (Li/M) are within the region enclosed by three lines given by the equations: y = -20.186x + 59.079, y = 35x - 99.393, and y = -32. 946x + 95.78 on a graph in which the x-axis represents a lattice constant a and the y-axis represents a compositional ratio (Li/M) of Li to M, and the lattice constant c is 14.2 to 14.25.