Cycle characterizations of LiMxMn2-xO4 (M = Co, Ni) materials for lithium secondary battery at wide voltage region

LiMxMn2-xO4 (M = Co, Ni) materials have been synthesized by a melt-impregnation method using gamma-MnOOH as the manganese source. Highly crystallized LiMxMn2-xO4 compounds were synthesized at a calcination temperature of 800 degrees C for 24 h in air. All compounds show a single phase except for LiNi0.5Mn1.5O4 based on the X-ray diffraction (XRD) diagram. With the increase of the doping content from 0.1 to 0.5, the capacity of doping materials decreases mainly in the 4 V region. Although LiM0.5Mn1.5O4 (M = Co, Ni) compound shows a small capacity in the (3 + 4) V region compared with parent LiMn2O4, it is a very effective material in reducing capacity loss in the 3 V region that is caused by the Jahn-Teller distortion. The doping of Co and Ni ions in the LiMn2O4 cathode material promotes the stability of this structure and provides an excellent cyclability. (C) 2000 Elsevier Science S.A. All rights reserved.