Hierarchical coral-like binder-free SbSnBi@Cu anode fabricated via pulsed reverse electrodeposition toward high-performance sodium storage

Sodium-ion batteries (SIBs) have become a promising alternative to lithium-ion batteries due to the abundant reserves and low cost of sodium resources. However, conventional Sb-based alloy anodes suffer from severe volume expansion, structural degradation, poor cycling stability and inferior rate capability, which severely hinder their practical applications. Herein, a hierarchical coral-like binder-free SbSnBi@Cu ternary alloy anode was in-situ synthesized on Cu foil via a pulsed reverse electrodeposition strategy. The reverse voltage triggered the dissolution–redeposition of the Cu current collector and realized efficient in-situ Cu doping, forming a multi-intermetallic synergistic electrode system. Material characterizations confirmed uniform distribution of Sb, Sn, Bi and Cu elements, as well as the generation of Cu₂Sb, Cu₃Sn, SbBi and SnSb phases. When evaluated as a binder-free anode for sodium storage, the optimized electrode delivered a high reversible capacity of 488.1 mAh·g −1 at 0.3 A·g −1 after 100 cycles with a capacity retention of 93%. Even at an ultrahigh rate of 15C, it still maintained 461.1 mAh·g −1 . The in-situ Cu doping and unique coral-like morphology synergistically buffered volume changes, enhanced electrical conductivity and improved structural integrity. This work provides an effective and scalable approach for designing high-performance alloy-based anodes for advanced SIBs.