Enhanced cycling performance in heat-treated tin-based composite oxide anode for lithium-ion batteries

Highlights: ► SnPxOy thin films were deposited on stainless steel substrates by electron-beam evaporation with post heat treatment at various temperatures for 4 h for use as anodes in thin-film lithium ion batteries. ► The thin films heat-treated for 4 h at 500 °C maintained a stable and high specific discharge capacity after 300 cycles. ► This result indicated that they still showed stable cyclability over 300 cycles. As evidenced by these results, addition of P2O5 leads to a significant increase in the cycling property. - Abstract: SnPxOy thin films were deposited on stainless steel substrates by electron-beam evaporation for use as anodes in thin-film lithium ion batteries. The thin films were heat-treated at various temperatures for 4 h, and their composition, microstructure, and electrochemical properties were characterized by Rutherford backscattering spectroscopy (RBS), X-ray diffraction (XRD), cyclic voltammetry (CV), and AC impedance spectroscopy. The specific discharge capacity of the as-deposited SnPxOy thin film anode decreased rapidly to 12 μAh cm−2-μm within 10 cycles. However, after heat treatment for 4 h at 500 °C, it maintained a high specific discharge capacity of 136 μAh cm−2-μm and excellent cyclability even after 300 cycles, in contrast to pure SnOx thin film.