Cation vacancy and discharge capacity of Li[Mn2-xLix]O4 spinel for lithium ion secondary batteries

Manganese spinel for lithium ion secondary batteries has been investigated. In order to find out the best composition in Li[Mn 2-x Li x ]O 4 , manganese spinel with various Li/Mn ratios were synthesized and evaluated to measure lattice constant, Mn oxidation state, true density, T c1 in TGA (Thermogravimetric Analysis) curve and initial discharge capacity. The results indicate excess Li ion substitutes for Mn ion in the 16d octahedral site. Differences between theoretical and experimental values of true density and discharge capacity suggest the existence of some vacancies in spinel structure. From TGA curve and discharge capacity, a cation vacancy model seems to be more practical than an oxygen vacancy model.