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

Lignin-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 sp(2)-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 sp(2)- and sp(3)-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 m(2) 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.