CeO2 thin films obtained by sol-gel deposition and annealed in air or argon

Thin films of CeO2 were prepared on SnO2/F-coated glass plates by the sol-gel dip-coating process using CeCl3·7H2O as a precursor. The films were heat-treated in an air or argon atmosphere. The structural, electrochemical and optical properties of these films depend on the preparation conditions. Transmission electron microscopy (TEM) showed the films to be polycrystalline with randomly orientated crystallised domains of up to 10 nm in size. The degree of crystallinity of films heat-treated in argon is higher than that of those heat-treated in air, and therefore their charge capacity values (15.9 mC cm-2 after 100 cycles) and reversibility of the ion-storage process (0.99 after 100 cycles) are higher than for films heat-treated in air (10.5 mC cm-2 and 0.86 after 100 cycles, respectively). Both films are optically passive under Li+ ion insertion and have high optical transmittance (>80%)