| 摘要 |
PROBLEM TO BE SOLVED: To improve three characteristics including the charge/discharge capacities, cycle characteristic and high-temperature stability at a good balance by substituting part of sites occupied by manganese atoms in the lithium-manganese oxide having a spinel structure with an atom having the valence in a specific range, and selecting the average valence of manganese. SOLUTION: A lithium-manganese oxide is used at the positive electrode active material of a lithium secondary battery. The positive electrode active material, a conductive material and a binder are mixed, and a positive electrode mix is molded into a sheet shape as a positive electrode 1. This lithium- manganese oxide is obtained by substituting parts of the 16d site occupied by manganese atoms by an element M substituted in the state of trivalence or below and an element N substituted in the state of tetravalence or above, and the average valence of manganese is 3.501 or above. The average valence of manganese is normally 3.8 or below, desirably 3.58 or below. The total substitution quantity of the element M and element N is normally set to 5-25 atom.%, desirably 12.5-17.5 atom.%, against manganese atoms. |
