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

Substituted lithium cobaltates LiCo0.5M0.5O2 (where M=Ni, Mg, Mn, Zn) have been synthesized by the combustion of mixtures obtained from aqueous solutions containing the respective metal nitrates, LiNO3, and urea in stoichiometric amounts. The mixtures, when dried and fired at 700°C, ignite and yield submicron-sized powders. Physical properties of the synthesized products are discussed in the light of structural (XRD, SEM) and spectroscopic (FTIR and Raman) measurements. XRD results show that most of the compounds have a structure similar to LiCoO2, while LiCo0.5Mn0.5O2 crystallises with the modified-spinel structure. FTIR and Raman measurements probed the cationic environment in LiCo0.5M0.5O2 structures in order to investigate cation distribution and local distortion in the lithiated lattice. Performances of lithiated oxides as cathode materials in lithium batteries and substitutive effect on electrochemical properties have been investigated. Stable charge–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 used.