Modulation of micropores to remold the rate capability of lignin-derived porous carbon cathodes in zinc-ion hybrid supercapacitors

Abstract

Recent advancements in energy storage systems highlight the potential of zinc-ion hybrid capacitors (ZIHCs) due to their synergistic combination of high energy and power density. To solve the poor rate capability of porous carbon cathodes in Zn²⁺ storage, we propose a chemical activation and in situ templating strategy to tailor the pore structure of lignin-derived porous carbon (LPC). Mesoporous channels are engineered via the in situ pyrolysis of ZnC₂O₄ to generate nano-ZnO templates to facilitate rapid zinc ion transport. Simultaneously, gas evolution during pyrolysis exfoliates the carbon framework, while the etch effect of ZnCl₂ results in the formation of abundant large micropores. The optimized LPC-2-3 exhibits a high specific surface area (SSA) of 1086 m² g⁻¹, a large microporous structure (0.9–2 nm), and a hierarchical porous structure. Notably, when the current density increases from 0.1 to 50 A g⁻¹, it retains 55.6 % of the initial capacity, which demonstrates outstanding electrochemical performances. The superior Zn²⁺ ion storage capability of LPC-2-3 is ascribed to the hierarchical porous structure, which ensures efficient Zn²⁺ ion transport. This work highlights the critical role of large micropore-dominated structures in the rate performance of ZIHCs and provides valuable perspective to the design of high-rate porous carbon cathodes through targeted pore structure engineering.