Active material for lithium secondary battery, electrode for lithium secondary battery, lithium secondary battery, and method for producing the same

Abstract

It is an object of the present invention to provide an active material for a lithium secondary battery having high discharge capacity and excellent in high rate discharge characteristics and a lithium secondary battery using the same. The active material for a lithium secondary battery containing a solid solution of a lithium-transition metal composite oxide having an α-NaFeOtype crystal structure and the lithium secondary battery using the same have features that the composition ratios of the metal elements contained in the solid solution satisfy LiCoNiMgMn(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 P; and the active material has discharge capacity exceeding 200 mAh/g. Further, in addition to the above-mentioned features, they have features that an intensity ratio between the diffraction peak of (003) plane and the diffraction peak of (114) plane measured by X-ray diffractometry is I/I≧1.15 and/or the half width of the diffraction peak of (003) plane is 0.15° or less and the half width of the diffraction peak of (114) plane is 0.25° or less.