Synthesis and characterization of Sn nanophases in a Ta₂O ₅ matrix

To investigate the effect of Sn-Ta₂O₅ nanostructures on lithium insertion and extraction, size-controlled Sn-Ta₂O ₅ nanostructured electrodes, consisting of Sn nanoparticles in an amorphous, porous Ta₂O₅ matrix, were designed and fabricated using a cosputtering system with Sn metal and Ta₂O ₅ 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 Ta ₂O₅ 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.