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.