| 摘要 |
PROBLEM TO BE SOLVED: To provide an active material excellent in charge/discharge cycle characteristics and less in deterioration of capacity even after high-rate charging/discharging, and a secondary battery using the active material.SOLUTION: A composite oxide is represented by a compositional formula: NaMnMO(where, x equals to from 0.40 to 0.65, y equals to from 0.02 to 0.20, and z equals to from 0 to 0.1, and M represents at least one selected from transition metal elements). In the composite oxide, the M contains an element including a positive ion with a diameter larger than that of Mn, so that volume change of the crystal lattice of the composite oxide is reduced, and charge/discharge cycle characteristics and charge/discharge rate dependency of capacity are improved. |
