Electrochemical lithium insertion in some niobates MNb2O6 (M=Mn, Co, Ni, Cu, Zn and Cd)

Several oxides with the general formula MNb2O6 (M=Mn, Co, Ni, Cu, Zn and Cd) have been tested as cathodes for lithium batteries. When discharging electrochemical cells using these niobates as active materials down 0.5 V, the maximum observed lithium content (x) in LixMNb2O6 was x=0.9, 0.9, 1.15, 1.5, 2.3 and 3.0 for M=Mn, Co, Zn, Cd, Ni and Cu, respectively. In situ X-ray diffraction experiments revealed in all cases a certain loss of crystallinity as the insertion reaction proceeds. Only the copper niobate showed an almost complete amorphization after the initial discharge. The kinetics of lithium insertion in these compounds was studied by electrochemical spectroscopy in a stepping potential mode.