Process for production of positive electrode active material

Abstract

A nonaqueous secondary cell is provided, which includes a positive electrode including an active material having the formula: Li.sub.y Ni.sub.1-x Me.sub.x O.sub.2 where Me is one of Ti, V, Mn and Fe; the number of moles of x and y: 0.2<y.ltoreq.1.3; when Me is Ti, V or Fe, 0<x<0.5; and when Me is Mn, 0.ltoreq.x<0.6; having a hexagonal crystal structure and lattice constants a.sub.0 and c.sub.0 in the ranges of 2.83 to 2.89 .ANG. and 14.15 to 14.31 .ANG., respectively, as identified by X-ray diffraction pattern; a negative electrode of Li, an alloy of li or a carbon material intercalated with Li; and a nonaqueous electrolyte. The active material having the formula: Li.sub.y Ni.sub.1-x Mn.sub.x O.sub.2 where the number of moles of x and y are 0.ltoreq.x.ltoreq.0.3 and 1.0.ltoreq.y.ltoreq.1.3 is produced by employing as starting materials an amount of a compound of divalent Mn corresponding to the number of atomic moles of Mn indicated by x, an amount of a nickel compound corresponding to the number of atomic moles of Ni indicated by 1-x, and an amount of a lithium compound corresponding to the number of atomic moles of Li indicated by y; predrying the starting materials, subjecting to a first heat treatment in an oxidizing atmosphere and passing through a cooling stage to produce an intermediate; and subjecting the intermediate to a second heat treatment at a different temperature from that in the first treatment in an oxidizing atmosphere.