A new kind of high-voltage negative electrode material for thin-film rechargeable lithium-ion batteries was prepared through electrochemically reductive decomposition of an amorphous Li-V-Si-O thin solid electrolyte film. The thin solid electrolyte film was prepared by pulsed laser deposition, showing 1.3 x 10(-7) S cm(-1) in ionic conductivity with negligible electronic conductivity. Electrochemical lithium insertion into the thin solid electrolyte film was observed at ca. 1.7 V (vs Li/Li+), which was the potential window of the reduction side for the film electrolyte. When the lithium insertion/extraction reaction was repeated over the reductive-side potential window (1.0-4.0 vs Li/Li+) at low current density, the charge/discharge capacity gradually increased with the repetition of the reaction. Consequently, large charge/discharge capacity (350 mAh g(-1)) was achieved under quasi-open-circuit voltage conditions between 1.2 and 2.7 V (vs Li/Li+). X-ray photoelectron spectroscopy analysis revealed that the redox reaction of vanadium ions in the film compensated the electrical charge balance for the lithium insertion/extraction reaction of the film electrolyte. The apparent lithium diffusion coefficient of the film was 1 x 10(-1)5 cm(2) s(-1) < D-Li(app) < 2 x 10(-13) cm(2) s(-1). (C) 2006 The Electrochemical Society.