Bio-inspired design of a self-supported bismuth microforest for high performance sodium storage

Abstract

The sodium-ion battery (SIB) as a promising candidate for large-scale energy storage has attracted widespread attention in recent years. However, its practical application is plagued by the lack of suitable anode materials that can afford long cycle life, high rate capability and large capacity. Herein, we report a high-performance self-supported Bi microforest (MF) anode with Bi microtree arrays uniformly grown on porous Cu foil for SIBs. The Bi MF can be directly employed as an anode without using any binders and conductive additives. Finite-element analysis and electrochemical kinetics analyses reveal that such a tree-like microstructure facilitates fast Na⁺ diffusion and promotes effective stress dissipation. As a result, the Bi MF electrode shows exceptionally high rate capability (338.9 mA h g⁻¹ at 50 A g⁻¹ with a capacity retention of 94.2%) and excellent cycling stability (95.9% capacity retention after 1200 cycles at 1 A g⁻¹). More importantly, by pairing the Bi MF anode with a Na₃V₂(PO₄)₃ cathode, the assembled full cell achieves a long cycle life and an inspiring energy density of 132.2 W h kg⁻¹, showing the great potential of the Bi MF anode in sodium-ion full-cells.