Bionic Hollow Porous Carbon Nanofibers for Energy-Dense and Rapid Zinc Ion Storage

Abstract

Suboptimal spatial utilization and inefficient access to internal porosity preclude porous carbon cathodes from delivering high energy density in zinc-ion hybrid capacitors (ZIHCs). Inspired by the function of capillaries in biological systems, this study proposes a facile coordination-pyrolysis method to fabricate thin-walled hollow carbon nanofibers (CNFs) with optimized pore structure and surface functional groups for ZIHCs. The capillary-like CNFs maximize the electrode/electrolyte interface area, facilitating the optimal utilization of energy storage sites. The precision-engineered pore sizes in the fiber walls are specifically tailored to accommodate solvated [Zn(H₂O)₆]²⁺, thus enhancing ion storage capacity and supporting accelerated transport kinetics. The resultant ZIHCs achieve a battery-grade energy density of 132.8 Wh kg⁻¹ (based on active material), remarkable stability (98.7 % retention after 80,000 cycles at 10 A g⁻¹), along with practically high areal capacities. Combined in situ/ex situ spectroscopic characterizations, kinetic analyses, and theoretical calculations revealed that the superior energy storage performance arises from the advantageous microstructure of the biomimetic CNFs and the reversible physical/chemical adsorption process. This investigation offers a novel strategy for designing high-efficiency zinc ion storage carbon nanomaterials and provides insights into the cathodic storage mechanisms essential for advancing ZIHCs.