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

Sb 2 Te 3 and its amorphous carbon-modified nanocomposite (Sb 2 Te 3 –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 Sb 2 Te 3 and Sb 2 Te 3 –C nanocomposite electrodes. In both electrodes, Sb 2 Te 3 is converted into Na 3 Sb and Na 2 Te during Na insertion. However, Na 3 Sb and Na 2 Te in only the Sb 2 Te 3 –C nanocomposite electrode recombine into the original Sb 2 Te 3 phase after full Na extraction. As a consequence of its interesting conversion/recombination reaction during sodiation/desodiation reaction, the Sb 2 Te 3 –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 ).