Bi₂S₃ Nanorods Deposited on Reduced Graphene Oxide for Potassium-Ion Batteries

Hierarchical nanocomposites with surface active bonding features serve as an efficient electrode material for high-performance Li-/Na-/K-ion batteries. Tuning the physiochemical properties of these hierarchical nanocomposites has a great impact on the extremely improved electrochemical performance, and it is attributed to the synergistic effect of heterogeneous components. Herein, we report a hydrothermally synthesized bismuth sulfide (Bi2S3) nanorod bonding on the surface of the reduced graphene oxide (rGO) matrix and investigate it as an anode material for potassium-ion batteries. This hierarchical nanocomposite anode exhibits a high initial reversible capacity (586 mA h g–1 at 100 mA g–1), long-term cycling stability (410 mA h g–1 after 1000 cycles, 70% capacity retention), and an outstanding rate capability (140 mA h g–1 at 3 A g–1). This excellent electrochemical performance of the Bi2S3/rGO nanocomposite is attributed to the presence of active sites in rGO nanosheets that not only enhances the electrical conductivity of Bi2S3 nanorods but also prevents the shuttle effect of polysulfide through the formation of the in-built C–S bond, which is confirmed by X-ray photoelectron spectroscopy. Through the ex-situ X-ray diffraction patterns analysis at different voltage regions, a phase transformation mechanism has been proposed for K-ion storage in Bi2S3 nanorods. An ex-situ high-resolution transmission electron microscopy analysis reveals the structural and morphological stability of Bi2S3 nanorods. Further, the kinetic studies confirmed that the surface dominated pseudocapacitive K-ion storage also plays a major role in improving the electrochemical performance of the Bi2S3 nanorods/rGO nanocomposite. The K-ion full cell is successfully assembled, which exhibits stable cycling performance after 100 cycles at 1 C rate.