A powder of a layered lithium-nickel-manganese-cobalt composite oxide for use as a positive-electrode material for lithium secondary battery is provided which, when used as a positive-electrode material for lithium secondary battery, enables a cost reduction and higher safety to be reconciled with improved battery performances.
The powder of a layered lithium-nickel-manganese-cobalt composite oxide for use as a positive-electrode material for lithium secondary battery is composed of secondary particles formed by the aggregation of primary particles. It has a composition represented by the following formula (I), has a volume resistivity of 5×105 Ω·cm or lower in the state of being compacted at a pressure of 40 MPa, and has a value of C/S, wherein C is the concentration of carbon contained therein (% by weight) and S is the BET specific surface area thereof (m2/g), of 0.025 or smaller. The powder has been regulated so as to have a volume resistivity not higher than the specified value and a considerably reduced carbon content while having a composition in a limited range, whereby a cost reduction and higher safety can be reconciled with improved battery performances.
Li1+zNixMnyCo1−x−yOδ (I)
(0<z≦0.91, 0.1≦x≦0.55, 0.20≦y≦0.90, 0.50≦x+y≦1, 1.9≦δ≦3)