Combustion synthesis and characterization of substituted lithium cobalt oxides in lithium batteries

Substituted lithium cobaltates LiC0.5M0.5O2 (where M = Ni, Mg, Mn, Zn) have been synthesized by the combustion of mixtures obtained from aqueous solut ions containing the respective metal nitrates, LiNO3, and urea in stoichiom etric amounts, The mixtures, when dried and fired at 700 degreesC, ignite a nd yield submicron-sized powders. Physical properties of the synthesized pr oducts are discussed in the light of structural (XRD, SEM) and spectroscopi c (FTIR and Raman) measurements. XRD results show that most of the compound s have a structure similar to LiCoO2, while LiCo0.5Mn0.5O2 crystallises wit h the modified-spinel structure. FTIR and Raman measurements probed the cat ionic environment in LiC0.5M0.5O2 structures in order to investigate cation distribution and local distortion in the lithiated lattice. Performances o f lithiated oxides as cathode materials in lithium batteries and substituti ve effect on electrochemical properties have been investigated. Stable char ge-discharge features have been observed for Li//LiCo0.5M0.5O2 cells cycled in the potential range from 3.0 to 4.2 volts when Ni and Zn dopants are us ed, (C) 2000 Elsevier Science B.V. All rights reserved.