LITHIUM-MANGANESE COMPOSITE OXIDE, POSITIVE ELECTRODE MATERIAL FOR LITHIUM SECONDARY CELL, POSITIVE ELECTRODE AND LITHIUM SECONDARY CELL, AND METHOD FOR PREPARING LITHIUM-MANGANESE COMPOSITE OXIDE

The invention provides a lithium manganese oxide spinel suited as a cathode active material for lithium ion secondary batteries showing excellent high-temperature cycling behavior. The lithium manganese oxide is represented by the following general formula (1): Li MnMO wherein 0 ≤ α ≤ 0.5, 0.005 ≤ y ≤ 0.5, -0.1 ≤ δ ≤ 0.1, and M represents a metal element other than Li and Mn, and which shows the ratio of a main peak intensity at 5 ± 40 ppm to a main peak intensity at 525 + 40 ppm (I /I), each intensity being obtained by Li-NMR measurement according to the following measuring method, falling within the following range: I 0ppm /I 500ppm ≤ 0.65y + 0.02