Synthesis and Characterization of Sn Nanophases in a Ta2O5 Matrix

To investigate the effect of Sn-Ta2O5 nanostructures on lithium insertion and extraction, size-controlled Sn-Ta2O5 nanostructured electrodes, consisting of Sn nanoparticles in an amorphous, porous Ta2O5 matrix, were designed and fabricated using a cosputtering system with Sn metal and Ta2O5 targets. Transmission electron microscopy revealed well-dispersed Sn particles with average particle sizes of ~19 nm (sample A), ~30 nm (sample B), and ~50 nm (sample C). Both X-ray photoelectron spectroscopy and X-ray diffraction analysis of Sn-Ta2O5 confirmed that the Sn particles exist as a metallic crystalline structure, whereas the Ta2O5 matrix was present in an amorphous state. The performance of the Sn-Ta2O5 nanostructured electrode was superior to that of a Sn thin-film electrode during lithium insertion and extraction. The high-performance in the Sn-Ta2O5 nanostructured electrode is due to the larger number of reactive sites of Sn nanoparticles and the facilitation of the movement of lithium ions through the porous Ta2O5 matrix.