Facile and scalable pulsed electrodeposition of bi-active Bi-Sb alloy for high performance sodium ion batteries

Although sodium ion batteries (SIB) have shown great potential for large-scale energy storage systems, the development of high-performance anode materials for SIB is crucial for their progress. However, the cycling performance of SIB is currently limited by severe volume changes during the sodiation/desodiation process. To overcome this problem, a bi-active metal alloying strategy has been proposed. In this study, we utilized pulsed electrodeposition to prepare bismuth-antimony alloy anode materials. The resulting Bi44.9Sb55.1 alloy anode exhibited exceptional specific capacity, rate performance, and stability. After the second cycle, the discharge/ charge capacities were 505.3 mAh center dot g  1/496.7 mAh center dot g  1 at 1 A center dot g  1, with a coulombic efficiency of over 98 %. Even after 50 cycles, the capacities remained at 494.7 mAh center dot g  1/481.9 mAh center dot g  1 with a capacity retention rate of 97.9 %. These excellent properties were attributed to the stable structure and suitable voids for electron transport and ion diffusion in the Bi44.9Sb55.1 alloy, which effectively mitigated volume expansion during cycling. The reaction kinetics and mechanism were studied using cyclic voltammetry, in situ X-ray diffraction, and nuclear magnetic resonance techniques. Our work provides valuable insights for the development of bi-active metal alloy anodes for SIB.