Active material for non-aqueous electrolyte secondary battery and manufacturing method therefore

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 MLi/MT between the number of moles of lithium MLi and the number of moles of transition metal MT 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 P003 attributed to the (003) plane and a peak P104 attributed to the (104) plane,
• an integrated intensity ratio I003/I104 between the peak P003 and the peak P104 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,
• when said lithium-containing transition metal oxide desorbs lithium until its potential versus lithium metal reaches 5 V, the oxygen array in said crystal structure undergoes substantially no change, 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.