Engineering MoS₂ Nanosheets on Spindle-Like α-Fe₂O₃ as High-Performance Core–Shell Pseudocapacitive Anodes for Fiber-Shaped Aqueous Lithium-Ion Capacitors

Fiber-shaped aqueous lithium-ion capacitors (FALICs) featured with high energy and power densities together with outstanding safety characteristics are emerging as promising electrochemical energy-storage devices for future portable and wearable electronics. However, the lack of high-capacitance fibrous anodes is a major bottleneck to achieve high performance FALICs. Here, hierarchical MoS₂@α-Fe₂O₃ core–shell heterostructures consisting of spindle-shaped α-Fe₂O₃ cores and MoS₂ nanosheet shells on a carbon nanotube fiber (CNTF) are successfully fabricated. Originating from the unique core/shell architecture and prominent synergetic effects for multi-components, the resulting MoS₂@α-Fe₂O₃/CNTF anode delivers a remarkable specific capacitance of 2077.5 mF cm⁻² (554.0 F cm⁻³) at 2 mA cm⁻², substantially outperforming most of the previously reported fibrous anode materials. Further density functional theory calculations reveal that the MoS₂@α-Fe₂O₃ nano-heterostructure possesses better electrical conductivity and stronger adsorption energy of Li⁺ than those of the individual MoS₂ and α-Fe₂O₃. By paring with the self-standing LiCoO₂/CNTF battery-type cathode, a prototype quasi-solid-state FALIC with a maximum operating voltage of 2.0 V is constructed, achieving impressive specific capacitance (253.1 mF cm⁻²) and admirable energy density (39.6 mWh cm⁻³). Additionally, the newly developed FALICs can be woven into the flexible textile to power wearable electronics. This work presents a novel effective strategy to design high-performance anode materials for next-generation wearable ALICs.