Use of Li-M-Mn-O [M = Co, Cr, Ti] spinels prepared by a sol-gel method as cathodes in high-voltage lithium batteries

Doped spinels of formula LiM0.2Mn1.8O4 (M = Cr, Ca) and LiTi0.19Mn1.76O4 were prepared by using a sol-gel method involving Mn(acac)(3), Cr(acac)(3), [Ti(acac)(3)](2)[TiCl6] and Li2CO3 as precursors and propionic acid as chelating agent. On firing at 600 degrees C, the gels gave normal spinel phases of a high purity. The Co and Cr spinels consisted of very uniformly shaped microcrystals. The three doped spinels were tested as cathodes in 4 V lithium cells. The best performance was exhibited by the Go-doped spinel, followed by the Cr-doped spinel. By contrast, LiTi0.79Mn1.76O4 exhibited significant capacity fading upon cycling. All lithium in the Co- and Cr-doped manganese spinels can be extracted by charging the cells above 5 V. Under these conditions, the cell based on the Cr-doped spinel provided the best electrochemical performance. Ionic size and ligand field stabilization energies were considered in explaining the structural stability of the spinels: which has a direct effect on cathode performance. (C) 1999 Elsevier Science BN; All rights reserved.