ZnS/CuS nanoparticles encapsulated in multichannel carbon fibers as high-performance anode materials for flexible Li-ion capacitors

Transition metal sulfides (TMSs) are widely recognized for their potential as anode materials in the development of flexible lithium-ion capacitors (FLICs) owing to their high theoretical capacity. However, their practical application has been significantly limited by rapid capacity decay and sluggish kinetics associated with TMS volume variation. In response to these challenges, we have prepared ZnS/CuS nanoparticles embedded in continuous and multichannel carbon fibers (CFs). This was achieved through a process involving blow-spinning and subsequent sulfidation. Notably, the electrochemical performance of these materials was largely improved, owing to the synergistic effect of bimetallic sulfides. The ZnS/CuS-CF anode material demonstrated a high specific capacity of over 900 mAh g⁻¹ at a current density of 0.2 A g⁻¹. Furthermore, it exhibited superior rate capacity (300 mAh g⁻¹ at 20 A g⁻¹) and excellent cyclic stability, maintaining its performance over 1000 cycles at 10 A g⁻¹. We also prepared lithium-ion capacitors (LICs) using the same method. These LICs exhibited a maximum energy density of 136 Wh kg⁻¹, a high power density of 43.5 kW kg⁻¹, and an impressive cyclic stability over 4000 cycles. In addition, the FLICs, when configured in the form of a pouch cell, demonstrated significant potential for the development of smart, flexible electronic devices.