Progress on Sn-based thin-film anode materials for lithium-ion batteries

Thin-film lithium-ion batteries are the most competitive power sources for various kinds of micro-electro-mechanical systems and have been extensively researched. The present paper reviews the recent progress on Sn-based thin-film anode materials, with particular emphasis on the preparation and performances of pure Sn, Sn-based alloy, and Sn-based oxide thin films. From this survey, several conclusions can be drawn concerning the properties of Sn-based thin-film anodes. Pure Sn thin films deliver high reversible capacity but very poor cyclability due to the huge volume changes that accompany lithium insertion/extraction. The cycle performance of Sn-based intermetallic thin films can be enhanced at the expense of their capacities by alloying with inactive transition metals. In contrast to anodes in which Sn is alloyed with inactive transition metals, Sn-based nanocomposite films deliver high capacity with enhanced cycle performance through the incorporation of active elements. In comparison with pure Sn anodes, Sn-based oxide thin films show greatly enhanced cyclability due to the in situ formation of Sn nanodispersoids in an Li2O matrix, although there is quite a large initial irreversible capacity loss. For all of these anodes, substantial improvements have been achieved by micro-nanostructure tuning of the active materials. Based on the progress that has already been made on the relationship between the properties and microstructures of Sn-based thin-film anodes, it is believed that manipulating the multi-phase and multi-scale structures offers an important means of further improving the capacity and cyclability of Sn-based alloy thin-film anodes.