Reversible electrochemical insertion of lithium in nanocrystalline lanthanide doped ceria thin films with the fluorite structure

Thin films of lanthanide doped ceria formula Ce0.85Ln0.15O1.925 [Ln=lanthanide (III)] and Ce0.85Y0.15O1.925 were deposited on ITO-coated glass substrates and characterised for structure, morphology, crystallite size, spectral transmittance before and after lithium insertion and the amount and reversibility of lithium insertion by cyclic voltammetry. The films were found to be smooth, continuous, single phase and crystalline at 450°C, with the fluorite structure. Crystallite size values ranged from around 6 nm at 450°C and 9–16 nm at 600°C. Electrochemical studies showed a wide variance of behaviour towards reversible lithium intercalation with ionic size of the lanthanide, those doped with Nd, Dy and Y showing the highest charge capacities of around 20–25 mC. The films showed excellent transparency both before, after and during lithium insertion.