According to the process of this invention, first a manganese oxide seed
is prepared, which is then grown to obtain manganese oxide having large particle
diameters. The manganese oxide thus obtained is reacted with a lithium compound,
whereby lithium manganate having large particle diameters can be obtained. Since
the lithium manganate has large particle diameters and gives a high packing density,
lithium batteries with a high energy density can be provided by using the lithium manganate.