Construction of a Free-Standing Bismuth Carbon Nanofiber-Based Composite Anode Integrated with Molybdenum Disulfide for High-Performance Sodium-Ion Batteries

Developing free-standing electrodes without the need of metal current collectors, binders, and conductive additives are essential for promoting the development of sodium-ion batteries (SIBs) to attain higher energy density. In this study, we developed and effectively synthesized a novel three-dimensional free-standing sodium-ion battery anode material with the composition of Bi@MoS₂@C carbon nanofibers by cleverly utilizing the energy storage advantages of each material. By growing MoS₂ nanospheres on Bi carbon nanofibers and coating them with a carbon layer, this free-standing system achieves both structural optimization and synergistic performance enhancement. Experimental results show that this composite electrode has a remarkably high initial specific capacity of 275.31 mA h g⁻¹ at a current density of 0.5 A g⁻¹, significantly exceeding that of Bi carbon nanofibers (150.6 mA h g⁻¹). Furthermore, it retains a capacity retention of 96.07% after 800 cycles, which significantly exceeds that of pristine MoS₂ (72.33 mA h g⁻¹) as a sodium-ion battery anode. The significant performance improvement originates from the free-standing structural design and synergistic effects of Bi carbon nanofibers, MoS₂ nanospheres and carbon layer, which not only provide 3D electron transport pathways and improved conductivity but also effectively accommodate volume changes during the charging and discharging processes. This work offers a promising and practical strategy for designing high-performance free-standing energy storage electrodes through hybrid mechanisms and synergistic effects.