A cathode electroactive material for use in lithium ion secondary cells, process
for producing the material, and lithium ion secondary cells using the cathode electroactive
material, wherein the electroactive material predominantly comprises an LiMn
composite oxide particles with the spinel structure and particles of the electroactive
material have an average porosity of 15% or less, the porosity being calculated
by employing the following equation:
(wherein A represents a total cross-section area of pores included in a
cross-section of one secondary particle, and B represents the cross-section area
of one secondary particle), a tapping density of 1.9 g/ml or more, a size of crystallites
of 400 -960 , a lattice constant of 8.240 or less. The
cathode electroactive material of the present invention is formed of particles
which are dense and spherical and exhibit excellent packing characteristics to
an electrode, and exhibit high initial capacity and capacity retention percentage
at high temperature.
