Cesium chemistry enables microporous carbon nanofibers with biomimetic ion transport channels for zinc-ion capacitors

Abstract

Efficient ion transport and storage are critical for high-performance zinc-ion capacitors (ZICs). However, conventional carbon materials face challenges in optimizing ion storage due to limited ion-accessible sites and mismatched pore structures. In this work, we report a cesium-directed carbonization strategy that bypasses the conventional deacetylation process, enabling the direct transformation of cellulose acetate into flexible carbon nanofiber (CNF) films. The cesium chemistry not only preserves fiber integrity but also induces hierarchical micropores (0.78 nm and 1.1 nm) that are precisely tailored for hydrated Zn²⁺ ions. These ion transport channels mimic natural ion pathways, enabling rapid ion migration and efficient storage. The optimized CNF₁₀₀-750 achieves a high capacity of 203 mAh g⁻¹ at 0.1 A g⁻¹, an excellent energy density of 133.9 Wh kg⁻¹, and outstanding cycling stability with 96.6% retention after 90 000 cycles. In situ EIS, ex situ XRD and XPS analyses reveal the reversible surface redox reactions, which underpins the excellent electrochemical performance. This work establishes a scalable route for high-performance ZICs and provides new insights into designing biomimetic ion channels in porous carbon materials.