Li-Mn spinel oxide cathode materials were prepared by annealing of Li-Mn sp
inel oxide containing an oxygen deficiency, which were synthesized by high-
temperature calcination, under various oxygen pressures. The effects of the
annealing conditions on the produced phase were studied. From the changes
of the lattice constant and the chemical composition, it was found that the
spinel oxides prepared by high-temperature calcination were oxidized by th
e low-temperature annealing. The change in the oxidation degree during the
low-temperature annealing decreased with an increase in the Li/Mn molar rat
io. The effect of the preparation conditions on the reversible Li-intercala
tion/deintercalation reaction was also examined from the view points of the
oxygen deficiency. These experimental results implied that the cycle perfo
rmance in the oxygen-deficient Li-Mn spinel oxide was improved by the low-t
emperature annealing, and that the cycle performance of Li-Mn spinel oxide
cathode depended on the oxygen stoichiometry rather than the Li/Mn molar ra
tio. However, it was found that the complete recovery of the oxygen defect
structure was impossible when the oxygen deficiency was large enough. (C) 2
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