Patent ID: 8137847

Claim:
An active material for a non-aqueous electrolyte secondary battery comprising a lithium-containing transition metal oxide containing nickel and manganese and having a closest-packed structure of oxygen, wherein: an atomic ratio M Li /M T between the number of moles of lithium M Li and the number of moles of transition metal M T contained in said lithium-containing transition metal oxide is 1.1 to 1.4, said lithium-containing transition metal oxide has a crystal structure attributed to a hexagonal system, and the X-ray diffraction image of said crystal structure has a peak P 003 attributed to the (003) plane and a peak P 104 attributed to the (104) plane, an integrated intensity ratio I 003 /I 104 between the peak P 003 and the peak P 104 varies reversibly within a range from 0.7 to 1.5 in association with absorption and desorption of lithium by said lithium-containing transition metal oxide, said integrated intensity ratio varies linearly and continuously, and in said crystal structure, a lattice constant a representing a length of a axis and a lattice constant c representing a length of c axis satisfy 4.945<c/a, and c<14.30 Å.