Sodium Storage Enabled by Coral Reef-like Bi–Sb–Fe–P Alloys Synthesized via Pulsed Electrodeposition

Sodium-ion batteries (SIBs) are emerging as a promising alternative to lithium-ion batteries due to the abundance and cost-effectiveness of sodium (Na) resources. For the first time, we report a template-free synthesis of Bi–Sb–Fe–P negative electrodes designed to leverage their high theoretical sodium storage capacity. Notably, the incorporation of phosphorus (P) significantly enhances the performance of the Bi–Sb–Fe–P negative electrode, which is characterized by a unique coral reef-like nanoscale morphology. Phosphorus serves as a structure-directing agent during the electrodeposition process, regulating the surface morphology and facilitating the formation of this distinctive architecture. These features enable the Bi–Sb–Fe–P negative electrode to exhibit outstanding electrochemical performance, achieving a specific capacity of 727 mA h·g^–1 after 100 cycles with a high retention rate of 90%, corresponding to a negligible capacity loss of only 0.16% per cycle. In contrast, the Bi–Sb–Fe negative electrode, with its irregular cluster-like structure, delivers a significantly lower specific capacity of 346 mA h·g^–1 in identical cycling conditions. Furthermore, cyclic voltammetry (CV) measurements were performed to elucidate the reaction mechanisms and charge dynamics of both negative electrode materials. The findings highlight the significant potential of Bi–Sb–Fe–P as a next-generation negative electrode material tailored for high-performance SIB applications.