Bi3Se4 nanodots in porous carbon: A new anode candidate for fast lithium/sodium storage

Bismuth selenide has attracted considerable attention as anode materials due to its high theoretical capacity. However, its development has been limited to Bi2Se3-based composites up to now. Herein, a facile strategy to regulate the atomic ratio of BixSey is propsed and a new Bi3Se4-based anode material is successfully developed. Firstly, in-situ XRD technique is employed to disclose the combined conversion and alloying reactions mechanism. Besides, a uniform structure with Bi3Se4 nanodots embedded within a sheet-like carbon framework is verified, ensuring fast kinetics and efficient alleviation of stress derived from dramatic volume expansion. Furthermore, experimental results combined with theoretical calculations prove the formation of robust interfacial C-Se bonds, which could simultaneously enhance the inherent bulk electronic conductivity and accelerate ionic transportation. As expected, Bi3Se4-based electrode achieves an ultralong cycle life of 1500 cycles at a high current density of 2 A g−1 and fast lithium storage capability of 211 mAh g−1 at an ultrahigh rate of 20 A g−1. Such exceptional performance fully proves the huge potential of Bi3Se4-based electrode and also provides guidance for the exploration of other high-performance BixSey-based anodes.