Vanadium-Doped Bi 2 S 3 @Co 1−x S Heterojunction Nanofibers as High-Capacity and Long-Cycle-Life Anodes

Lithium-ion batteries (LIBs) are considered one of the most important solutions for energy storage; however, conventional graphite anodes possess limited specific capacity and rate capability. Bismuth sulfide (Bi 2 S 3 ) and cobalt sulfide (Co 1−x S) with higher theoretical capacities have emerged as promising alternatives, but they face challenges such as significant volume expansion during electrochemical cycling and poor electrical conductivity. To tackle these problems, vanadium was doped into Bi 2 S 3 to improve its electronic conductivity; subsequently, a vanadium-doped Bi 2 S 3 (V-Bi 2 S 3 )@Co 1−x S heterojunction structure was synthesized via a facile hydrothermal method to mitigate volume expansion by the closely bonded heterojunction interface. Moreover, the built-in electric field (BEF) created at the heterointerfaces can significantly enhance charge transport and facilitate reaction kinetics. Additionally, the nanofiber morphology of the V-Bi 2 S 3 @Co 1−x S heterojunction structure further contributed to improved electrochemical performance. As a result, the V-Bi 2 S 3 electrode exhibited better electrochemical performance than the pure Bi 2 S 3 electrode, and the V-Bi 2 S 3 @Co 1−x S electrode showed a significantly enhanced performance compared to the V-Bi 2 S 3 electrode. The V-Bi 2 S 3 @Co 1−x S heterojunction electrode displayed a high capacity of 412.5 mAh g −1 after 2000 cycles at 1.0 A g −1 with high coulombic efficiencies of ~100%, indicating a remarkable long-term cycling stability.