3D Bismuth Anode with Synergistic Structural and Interfacial Optimization for High-Performance Sodium-Ion Capacitors

Sodium-ion capacitors (SICs) suffer from a pronounced kinetic mismatch between anodes and cathodes. Bismuth-based anodes have emerged as promising candidates to mitigate this issue, owing to their low operating potential (∼0.6 V), excellent rate capability (50 A g^-1), and high theoretical specific capacity (∼384 mAh g^-1). Nevertheless, their practical widespread adoption is severely hindered by the drastic volume expansion (∼354%) during cycling. Here, Bi nanoparticles anchored on porous carbon (Bi@PCN) are synthesized via liquid-phase reduction and thermal reduction as a high-rate SIC anode. The composite delivers excellent rate performance (50 A g^-1) and cycling stability (10,000 cycles). The porous carbon framework alleviates volume expansion during alloying, helping to maintain the electrode architecture without degradation. The Bi@PCN//AC SIC achieves high energy/power densities of 118.16 Wh kg^-1 and 11,574.83 W kg^-1, demonstrating the potential of high-rate alloy-based anodes for advanced SICs.