Patent ID: 8808584

Claim:
An active material for a lithium secondary battery comprising a solid solution of a lithium-transition metal composite oxide having an α-NaFeO 2 type crystal structure, wherein the composition ratios of metal elements contained in the solid solution satisfy Li 1+(x/3) Co 1−x−y−z Ni y/2 Mg z/2 Mn (2x/3)+(y/2)+(z/2) (x>0; y>0; z>0; x+y+z<1); the active material has an x-ray diffraction pattern capable of belonging to space group P3 1 12 or R3 − m; and a peak intensity ratio between the diffraction peak intensity I (003) of (003) plane and the diffraction peak intensity I (114) of (114) plane or the diffraction peak intensity I (104) of (104) plane measured by x-ray diffractometry is I (003) /I (114) ≧1.15 or I (003) /I (104) ≧1.15.