Chronoamperometric studies of LiCoO2 and LiNiO2 particles during lithium-ion insertion/extraction

Lithium-ion insertion/extraction kinetics at a single particle of transition metal oxides (LiCoO2 and LiNiO2) were investigated with microelectrode technique, in which a fine metal filament was manipulated to make an electric contact with a single particle placed in an electrolyte solution. The apparent chemical diffusion coefficient (D-app) of lithium ion was determined by potential-step chronoamperograms assuming spherical diffusion in the particle. It was found that the diffusion rate of lithium ions within these layered oxides increases with the expansion of interlayer distance. In addition to such general tendency, the plots of D-app showed minimum values at the two-phase reaction regions.