Effect of Co doping in LiMn2O4

Lithium transition-metal oxides Li(Mn2-xCox)O-4 (0 less than or equal to x less than or equal to 0.5) are synthesized by solid-state reaction. X-ray a nd electrochemical data show that the replacement of Mn3+ (d(4)) ions by Co 3+ (d(6)) in the octahedral framework of the spinel eliminates the local di sorder present in the lattice around the [Mn3+O6] octahedra. The capacity l oss observed in the undoped Li/LiMn2O4 cell is about 25% after 20 cycles, w hereas that for the x = 0.1 and 0.2 doped spinel materials is about 0.48 an d 1%, respectively. The good capacity retention of Li(Mn2-xCox)O-4 (0.1 les s than or equal to x less than or equal to 0.5) electrode is attributed to the stabilization of the spinel structure by Cc doping for Mn ion sites. Th e chemical substitution of Co3+ for Mn3+ in LiMn2O4 improves the efficiency in maintaining electrochemical capacity over a large number of cycles with out sacrificing initial reversible capacity at room temperature. (C) 2001 E lsevier Science B.V. All rights reserved.