Positive electrode active material for lithium secondary cell

Abstract

The present invention relates to a positive electrode active material including a lithium metal composite oxide having a layer crystal structure, and provides a novel positive electrode active material for a lithium secondary cell, which can suppress the reaction with an electrolyte solution and can raise the charge-discharge cycle ability of the cell, and can make good the output characteristics of the cell. There is proposed a positive electrode active material for a lithium secondary cell, including an active particle having a surface portion where one or a combination of two or more (these are referred to as 'surface element A') of the group consisting of Al, Ti and Zr is present, on a surface of a particle including a lithium metal composite oxide having a layer crystal structure and represented by the general formula: Li1+xM1−xO2 (wherein M is one or a combination of two or more (these are referred to as 'constituent element M') of the group consisting of Mn, Co, Ni, transition elements of from the third group elements to the 11th group elements of the periodic table, and typical elements up to the third period of the periodic table), wherein the ratio (CA/CM) of a concentration CA of the surface element A to a concentration CM of the constituent element M is higher than 0 and lower than 0.8, as measured by XPS; the amount of surface lithium impurity is smaller than 0.40% by weight; and in an X-ray diffraction pattern measured by XRD, the ratio (003)/(104) of an integral intensity of the peak originated from the (003) plane to an integral intensity of the peak originated from the (104) plane is higher than 1.15.