| 摘要 |
A positive electrode material capable of achieving high charge and discharge efficiency and a secondary battery using the positive electrode material. The positive electrode material contains a Li.Ni composite oxide or a Li.Ni.Co composite oxide. Each of the composite oxides has a characteristic that a reduction wave in a current-potential curve obtained by cyclic voltammetry does not have a current peak in a range where the potential is larger than 3.4V and smaller than 3.6V with a Li metal potential used as a reference. The Li.Ni composite oxide has a mole ratio of Ni to Li (Ni/Li) larger than 1.0 and is therefore non-stoichiometric. Thus, in the positive electrode made of the positive electrode material, occurrence of a distortion in a charging and discharging process is suppressed, polarization does not become large even at the last stage of the discharge, and a high charge and discharge efficiency can be achieved.
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