Constructing Bi2Se3/Bi2O3 heterostructure as promising anode for efficient sodium-ion storage

Sodium-ion batteries (SIBs) have been a promising potential alternative for sustainable electrochemical energy-storage devices. Bismuth-based materials can reserve substantial Na ions through alloying reaction and conversion reaction, leading to superior theoretical capacity. However, the alloying reaction is always accompanied by huge volume change during sodiation/desodiation processes. Herein, a flower-like Bi2Se3/Bi2O3 heterostructure is designed to address the structural degeneration problem of Bi-based materials. Diverse Bi2Se3/Bi2O3 heterostructures are produced via a facile hydrothermal reaction and subsequent annealing process, presenting apparently improved rate capability and cycling stability. Such excellent Na ion storage performance attributes to the charge redistribution around heterointerfaces caused by the unmatched band structure of two building blocks. The redistributed charges induce a dissimilar charged space nearby the phase boundaries, which not only enhance the structural integrity via coulombian force but also accelerate the diffusion of Na ions traversing heterointerfaces through electric field force. Meanwhile, the unique surface conducting states of Bi2Se3 can facilitate charge transport effectively. The initial discharge capacity of electrode reached 571 mAh/g at the current density of 0.1 A/g and maintained 310 mAh/g after 100 cycles. This work may provide a new route to enhance the structural stability of the serious volume expansion electrode materials.