Pore Sieving and Surficial Charge-Driven Desolvation for High Spatial Charge Density Carbon Cathodes in Zinc-Ion Hybrid Capacitors

Abstract

Aqueous zinc-ion hybrid capacitors (ZIHCs) have emerged as a sustainable energy storage technology. However, the slow diffusion of large solvated Zn²⁺ within nanopores and the restriction on the electric double layer (EDL) thickness limit the spatial charge density in carbon electrodes. Herein, multi-channel porous carbon nanofibers (MC-PCNFs) are designed with customized porosity and high-charge-density interfaces to facilitate rapid [Zn(H₂O)₆]²⁺ desolvation and compact EDL formation. The designed hierarchical hollow structure maximizes ion accessibility, while precisely tuned 1.07 nm pores enable direct [Zn(H₂O)₆]²⁺ adsorption onto catalytic desolvation sites, significantly reducing the desolvation energy barrier. The resulting ZIHCs achieve a high reversible capacity of 221 mAh g⁻¹, a battery-level energy density of 170.2 Wh kg⁻¹ (based on cathode materials), outstanding long-term cycling stability (>90,000 cycles, 98.7% retention), and practically high areal capacities. Through in/ex situ spectroscopy, theoretical calculations, kinetic analysis, and electrochemical quartz crystal microbalance (EQCM) analysis, the charge storage and interfacial desolvation mechanisms are comprehensively elucidated. This study provides a scalable and effective strategy for catalytic desolvation and high spatial charge density engineering, paving the way for next-generation high-energy, long-cycle-life ZIHCs.