NIOBIUM-COATED LITHIUM MANGANESE OXIDE POWDER AND MANUFACTURING METHOD THEREOF

To provide lithium manganese oxide powder being useful as a cathode active material of a lithium secondary battery, making it possible to curb the elution of Mn of the lithium manganese oxide powder and sufficiently improving cycle characteristics.MEANS FOR SOLVING THE PROBLEM: Niobium-coated lithium manganese oxide powder has a coating layer including niobium (Nb) in at least a part of a surface thereof, with a niobium content of 0.05 mass% or more and 3.0 mass% or less. The powder contains particles in a ratio of 50% or more in number, the particles having 1.2 or less of a variation coefficient of an atomic percentage ratio of Nb/Mn.SELECTED DRAWING: None 【課題】リチウムマンガン酸化物粉末のＭｎの溶出を抑制し、サイクル特性を十分に改善し得るリチウム二次電池の正極活物質として有用な該リチウムマンガン酸化物粉末を提供する。【解決方法】表面の少なくとも一部にニオブ（Ｎｂ）を含む被覆層を有するニオブ被覆リチウムマンガン酸化物粉末であって、ニオブの含有量が０．０５質量％以上３．０質量％以下であり、Ｎｂ／Ｍｎの原子パーセント比の変動係数が１．２以下である粒子を個数基準で５０％以上の割合で含む。【選択図】なし