NOVELTY - A lithium-containing metal oxide comprises crystal containing lithium-containing metal oxide (A) having spinel structure containing lithium-manganese-containing complex oxide (a) (I) and lithium containing metal oxide (B) having layered structure containing lithium-manganese-containing complex oxide (b) (II), in which lithium is arranged in layered form dissolved with active substance.    USE - Lithium-containing metal oxide is used for forming positive electrode of lithium-ion secondary battery (claimed). Uses include but are not limited to photovoltaic power generation, wind power generation, electrical storage device, and power supply for electric vehicle and consumer appliances.    ADVANTAGE - The lithium-containing metal oxide provides lithium-ion secondary battery with high capacitance and heavy current passage property during discharge.    DETAILED DESCRIPTION - A lithium-containing metal oxide comprises crystal containing lithium-containing metal oxide (A) having spinel structure containing lithium-manganese-containing complex oxide (a) of formula: Li1+kMn2-xMxO4-a (I) and lithium containing metal oxide (B) having layered structure containing lithium-manganese-containing complex oxide (b) of formula: Li2Mn1-yM'yO3-b (II), in which lithium is arranged in layered form dissolved with active substance.    M,M'=metallic element other than Mn and Li;    k,a,b=0-1 (excluding 1);    x=0-0.5 (excluding 0);and    y=0-1.    An INDEPENDENT CLAIM is included for manufacture of lithium-containing metal oxide, which involves baking hydroxide salt or carbonate of lithium and/or manganese, and carbonate, hydroxide salt, sulfate, nitrate, hydrochloride, acetate, or oxide of metal other than manganese and lithium by primary baking process, obtaining the lithium-containing metal oxide (A), mixing lithium compound (C) of formula: LizCaObHc (III) with the lithium-containing metal oxide (A), baking obtained mixture at a temperature lower than the highest calcination temperature by secondary baking process, and obtaining the lithium-containing metal oxide (B).