Reduction of Irreversibility in the First Charge of Tin Oxide Thin Film Negative Electrodes

Sputter deposited 3000 A tin oxide thin films into which metallic lithium (6000 A) was reacted were studied to develop a new negative electrode for thin film rechargeable lithium batteries. The crystal structure and chemical composition of the lithium reacted tin oxide films were characterized by X-ray diffraction (XRD) analysis and Auger electron spectroscopy, respectively. The charge/discharge performances of these films exhibited capacities >400 mAh/g for >75 cycles. There was no irreversible plateau near 0.8 V vs. Li/Li due to reduction of SnO 2 to Sn and Li 2 O during the first charge half-cycle. XRD and scanning transmission electron microscopy results suggest that the lithium-reacted tin oxide thin film consists of metallic tin, lithium oxide, and reduced tin oxide, and the reacted thin films show reduced microcracks created by density fluctuations.