Tin-based composite oxide thin-film electrodes prepared by pulsed laser deposition

Tin-based composite oxide (TCO) thin films with a reversible capacity of 460 mAh/g and good stability were fabricated by pulsed laser reactive deposition in an oxygen ambient. X-ray diffraction and atomic force microscopy show that nanocrystalline SnO{sub 2} is dispersed in an amorphous oxide matrix. The lithium ion insertion and extraction process in a 1 M LiPF{sub 6} nonaqueous electrolyte are examined. Cyclic voltammetry shows an irreversible reduction process in the first cycle. X-ray photospectroscopy spectra unambiguously revealed a conversion of Sn(IV) to metallic Sn. In situ spectroelectrochemical measurements demonstrate significant transmittance drops with the Li/TCO cells. The results show that the alloying of tim with lithium occurs reversibly following the irreversible reduction of tin oxide in the TCO film, which is consistent with the electrochemical mechanism proposed by Courtney and Dahn.