Tailoring Lignin‐Derived Porous Carbon Toward High‐Energy Lithium‐Ion Capacitor Through Varying Sp2‐ and Sp3‐Hybridized Bonding

Abstract

AbstractLignin‐derived porous carbon (LPC) shows great potential as electrode material for supercapacitors. However, precise control over the pore structure during the conventional carbonization–activation process remains challenging. Here, a molecular‐level strategy to tailor the pore structure through tuning inter‐/intra‐molecular bonding of lignin in a pre‐carbonization process is shown. Based on operando pyrolysis analysis, a molecular evolution model is proposed to elucidate the relationship between pre‐carbonization and the resulting porosity of LPC. Lignin undergoes a condensation process with an increase of sp2‐hybridized carbon bonding during pre‐carbonization, causing the extension of polycyclic aromatic structure and leading to an increased mesopore volume in the final porous carbon. The variation in the content ratio of sp2‐ and sp3‐hybridized carbon bonding provides insights into the spatial structure evolution of pre‐carbonized lignin, which correlates well with changes in the porous structure of LPC. The LPCs show ultrahigh specific surface area up to 3219 m2 g−1 and tailored meso‐/micropore distribution. The lithium‐ion capacitor full‐cell tests demonstrate the great potential of LPCs in energy storage applications with superior energy density and power density. This work provides a feasible strategy to precisely design the microstructure of LPC, offering promising prospects for energy storage technologies.