Highly Reversible Na-Ion Reaction in Nanostructured Sb2Te3-C Composites as Na-Ion Battery Anodes

Sb2Te3 and its amorphous carbon-modified nanocomposite (Sb2Te3-C) are synthesized by simple solid-state synthetic methods, and their potential as anode materials for rechargeable Na-ion batteries (NIBs) is evaluated. Ex situ X-ray diffraction and high-resolution transmission electron microscopy clearly demonstrate the sodiation/desodiation reaction mechanism of the Sb2Te3 and Sb2Te3-C nanocomposite electrodes. In both electrodes, Sb2Te3 is converted into Na3Sb and Na2Te during Na insertion. However, Na3Sb and Na2Te in only the Sb2Te3-C nanocomposite electrode recombine into the original Sb2Te3 phase after full Na extraction. As a consequence of its interesting conversion/recombination reaction during sodiation/desodiation reaction, the Sb2Te3-C nanocomposite electrode exhibits a long cycle life with highly reversible gravimetric and volumetric capacity (373 mAh g(-1) and 765 mAh cm(-3) over 50 cycles) and fast rate capability (1 C: 391 mAh g(-1) and 802 mAh cm(-3); 2 C: 377 mAh g(-1) and 773 mAh cm-3). (C) 2017 The Electrochemical Society.