Template-free electrodeposited coral-like SeSb alloy on copper foil as anode with biphasic synergy for high-performance sodium-ion batteries

<p dir="ltr">Antimony-based materials exhibit a great potential in sodium-ion battery applications due to their high capacity (660 mAh·g⁻¹) and appropriate sodium alloying potential (∼0.5 V vs. Na⁺). However, during the charging-discharging cycling process, they may undergo severe volume changes (up to 390 %), leading to rapid capacity decay, which hinders their practical applications. Herein, a coral-like SeSb alloy film was in-situ grown on copper foil via a template-free electrodeposition method combined with annealing. The introduction of selenium establishes a biphasic sodiation mechanism, effectively buffering volume expansion and enhancing electrochemical activity. Moreover, the ternary SeSbCu alloy phase generated during the annealing process acts as an “alloy adhesive”, strengthening the interfacial bonding force and suppressing structural detachment during cycling. The density functional theory (DFT) calculations show that the introduction of selenium reduces the Na⁺ diffusion energy barrier to 0.11 eV. Through the synergistic optimization of composition and structure, the SeSb alloy was endowed with excellent sodium storage performance. It delivered an initial discharge capacity of 579.6 mAh·g⁻¹ at a current rate of 1 C, with a capacity retention rate of 87 % after 100 cycles. At a rate of 10 C, it still maintained a reversible capacity of 323.6 mAh·g⁻¹, which is significantly superior to that of pure antimony anodes (126.4 mAh·g⁻¹). This template-free synthesis method for preparing coral-like SeSb alloys posing an efficient energy storage characteristics is a low-cost process that could accelerate the wide practical application of sodium-ion batteries.</p>