Durian-Inspired Design of Bismuth-Antimony Alloy Arrays for Robust Sodium Storage

Sodium-ion batteries have attracted widespread attention for cost-effective and large-scale electric energy storage. However, their practical deployment has been largely retarded by the lack of choice of efficient anode materials featuring large capacity and electrochemical stability and robustness. Herein, we report a durian-inspired design and template-free fabrication of a robust sodium anode based on triangular pyramid arrays of Bi_0.75Sb_0.25 alloy electrodeposited on Cu substrates. The Bi_0.75Sb_0.25 arrays exhibit an appreciable electrochemical robustness for sodium storage, sustaining a reversible capability 335 mAh g^-1 at a high rate of 2.5 A g^-1 and 87% of the initial capacity over 2000 cycles. We further demonstrate the applicability of the Bi_0.75Sb_0.25 array anode in sodium full cells by pairing it with a Na₃V₂(PO₄)₃/C cathode. This full cell achieves a high specific energy of 203 Wh kg^-1 (based on both active electrodes). Such an enhanced performance is attributed to the thorny-durian-like architecture and bimetallic alloy composition. The pyramid tip induces ion enrichment for rapid charge-transfer reaction, while the alloy design reduces the electrode volume swelling for stable Na cycling.