Bio-inspired carbon cathodes with sub-nanometer confinement for high-performance zinc-ion storage

Abstract

The slow desolvation and interfacial transport dynamics of Zn²⁺ present significant challenges for aqueous zinc-ion hybrid capacitors (AZIHCs), adversely affecting their performance and durability. Drawing inspiration from natural zinc transport proteins, we introduce a biomimetic approach utilizing microporous carbon materials (BMCs) that feature sub-nanometer confinement and a high concentration of oxygen-rich functional groups. These BMCs are synthesized through a scalable KOH activation method using green petroleum coke as a precursor, allowing precise control over the pore structure and surface characteristics. This innovative design emulates natural ion channels, facilitating the desolvation of Zn²⁺ and enabling rapid electrostatic interactions. Electrochemical tests indicate a substantial enhancement in Zn²⁺ storage capabilities, with the optimized BMCs (ISC-2) achieving an energy density of 95.2 Wh kg⁻¹, exceptional rate performance, and remarkable cycling stability, evidenced by over 99% capacity retention after 50 000 cycles. In situ Raman spectroscopy combined with in situ EIS was employed to elucidate the critical correlation between nanopore confinement, surface characteristics, and Zn²⁺ transport behavior. In addition, ex situ XPS analysis was carried out to further clarify the underlying charge storage mechanism. This work provides a foundation for molecular-level design strategies for next-generation AZIHC cathodes and deepens the theoretical understanding of electrochemical interfaces under confinement.