Stoichiometry dependence of electrochemical performance of thin-film SnOx microbattery anodes deposited by radio frequency magnetron sputtering

Thin-film SnOx microbattery anodes, with various oxygen deficiencies, are d eposited from a SnO2 target on to an ambient temperature substrate by radio frequency (RF) magnetron sputtering. The high reversible capacity and cycl e performance characteristics of SnOx are described. RF power density and p rocess gas pressure during deposition are fixed at 2.5 W/cm(2) and 10 mTorr , respectively. The SnOx films are characterized by energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spect roscopy (XPS). Constant-current galvanostatic charge-discharge tests of hal f cells are also performed. The stoichiometric parameter x increases with t he increase in oxygen partial pressure, but decreases when the number of Sn chips placed on the target material in an argon atmosphere are increased. It is observed that SnOx transforms to lithium oxide and metallic Sn after an initial Li intercalation reaction. The charge-discharge performance of t he tin oxide films is found to be dependent on stoichiometry. In the presen t work, SnO1.43 is the optimum stoichiometry, exhibiting the highest revers ible capacity (498.33 mu A h/cm(2) mu m) and the lowest irreversible capaci ty (301.79 mu A h/cm(2) mu m). (C) 2000 Elsevier Science S.A. All rights re served.