Active material for lithium secondary battery, electrode for lithium secondary battery, and lithium secondary battery

Abstract

[Object]; There is provided an active material for a lithium secondary battery, which has a high initial efficiency and a high discharge capacity, and particularly has a high discharge capacity at a low temperature (excellent low-temperature characteristic), and a lithium secondary battery using the active material. [Solution]; An active material for a lithium secondary battery, which contains a solid solution of a lithium transition metal composite oxide having an α-NaFeOcrystal structure, wherein the composition ratio of metal elements contained in the solid solution satisfies, LiNaCoNiMnO(0<y≦0.1, 0.4≦c≦0.7, x+a+b+c=1, 0.1≦x≦0.25, −0.2≦d≦0.2), the active material has an X-ray diffraction pattern attributable to a space group R3-m (P312), and in the Miller index hkl, the half width of the diffraction peak of the (003) is 0.30° or less and the half width of the diffraction peak of the (114) plane is 0.50° or less. Further, the average of three oxygen position parameters determined from crystal structure analysis by the Rietveld method on the basis of the X-ray diffraction pattern is preferably 0.264 or less.