DOPED LI-MN SPINELS - PHYSICAL CHEMICAL CHARACTERISTICS AND ELECTROCHEMICAL PERFORMANCE IN LI BATTERIES/

Several doped spinel-type Li-Mn oxides of formula Li1+xMyMn2-(x+y)O4+2 , where Mn is partly replaced by Li, Cu, Zn, Ni, Co, Fe, Cr, Ga, Al, B , or Ti, were prepared by a solid-state reaction at 730 degrees C. The se spinels were investigated by X-ray powder diffraction, thermal anal ysis, slow step voltammetry, and galvanostatic cycling at medium-high rates. Even substitutional levels as low as 0.05 atom/formula unit pro duce structural effects that are reflected in the electrochemical char acteristics. The substituents may occupy either tetrahedral 8a sites o r octahedral 16d sites. Examples of the first type of substitution are provided by Ga3+ and Zn2+, while octahedral sites are preferred by, e .g., Ni2+ and Cr3+. Cycling at practical rates produces capacities of similar to 100 mA h/g for the best materials with limited capacity los ses (3-6.10(-2) mA h/g.cycle). The lower Mn3+ content with respect to undoped spinel explains the initially lower capacities.