Electrochemical behaviour of solid lithium cobaltate (LiCoO2) and lithium manganate (LiMn2O4) in an aqueous electrolyte system

Lithium cobaltate (LiCoO2) and lithium manganate (LiMn2O4) were synthesized by self-propagating high-temperature combustion and their phase purity and composition were characterized by X-ray diffraction and inductively couple d plasma spectroscopy. These transition metal oxides were mechanically immo bilized on the surface of paraffin-impregnated graphite electrodes and thei r cyclic voltammetric behaviour in aqueous alkali electrolytes was examined . It was shown that both the oxides undergo proton insertion upon the reduc tion of Co3+ to Co2+ in LiCoO2 and Mn4+ to Mn3+ in LiMn2O4, while they dein tercalate protons on the reverse oxidation. Scanning electron microscopy re veals spherical LiCoO2 particles with a very narrow size distribution. Ener gy dispersive X-ray detection proved the absence of metal cation intercalat ion.