A lithium-manganese complex oxide represented by a formula Li[Mn.sub.2-X-Y
Li.sub.X M.sub.Y ]O.sub.4+.delta. (wherein M is at least one element
selected from the groups IIa, IIIb and VIII of the 3rd and 4th periods,
and 0.02.ltoreq.X.ltoreq.0.10, 0.05.ltoreq.Y.ltoreq.0.30 and
-0.2.ltoreq..delta.<0.2), having a spinel crystalline structure of
0.22.degree. or less of half value width of the (400) plane of powder
X-ray diffraction by CuK.alpha. and an average diameter of crystal grains
by SEM observation of 2 .mu.m or less, and a spinel crystalline structure
lithium-manganese complex oxide having a BET specific surface area of 1.0
m.sup.2.multidot.g.sup.-1 or less; production methods thereof; and a
lithium secondary battery which uses the lithium-manganese complex oxide
as the positive electrode active material are described.
Ένα σύνθετο οξείδιο λίθιο-μαγγάνιου που αντιπροσωπεύεται από έναν τύπο λη[Μν.σuψ.2-Χ-Υ Li.sub.X M.sub.Y ]O.sub.4+.delta. (όπου το μ είναι τουλάχιστον ένα στοιχείο που επιλέγεται από τις ομάδες IIa, IIIb και VIII των 3$α και 4$α περιόδων, και το 0.02.ltoreq.X.ltoreq.0.10, 0.05.ltoreq.Y.ltoreq.0.30 και -0.2.ltoreq..delta.
