Multi-Channel Hollow Carbon Nanofibers with Graphene-Like Shell-Structure and Ultrahigh Surface Area for High-Performance Zn-Ion Hybrid Capacitors

Porous carbon is the most promising cathode material for Zn-ion hybrid capacitors (ZIHCs), but is limited by insufficient active adsorption sites and slow ion diffusion kinetics during charge storage. Herein, a pore construction-pore expansion strategy for synthesizing multi-channel hollow carbon nanofibers (MCHCNF) is proposed, in which the sacrificial template-induced multi-channel structure eliminates the diffusion barrier for enhancing ion diffusion kinetics, and the generated ultrahigh surface area and high-density defective structures effectively increase the quantity of active sites for charge storage. Additionally, a graphene-like shell structure formed on the carbon nanofiber surface facilitates fast electron transport, and the highly matchable pore size of MCHCNF with electrolyte-ions favors the accommodation of charge carriers. These advantages lead to the optimized ZIHCs exhibit high capacity (191.4 mAh g(-1)), high energy (133.1 Wh kg(-1)), along with outstanding cycling stability (93.0% capacity retention over 15000 cycles). Systematic ex situ characterizations reveal that the dual-adsorption of anions and cations synergistically ensures the outstanding electrochemical performance, highlighting the importance of the highly-developed porous structure of MCHCNF. This work not only provides a promising strategy for improving the capacitive capability of porous materials but also sheds light on charge storage mechanisms and rational design for advanced energy storage devices.