Lignin organic–inorganic supramolecular aggregate derived N,O co-doped porous carbon nanosheets for high performance zinc-ion hybrid capacitors†

Abstract

Nitrogen and oxygen co-doped porous carbon holds considerable potential for enhancing zinc-ion hybrid capacitors (ZIHCs) in large-scale energy storage. However, designing high-performance carbonaceous cathodes with accessible active sites and efficient ion transport pathways remains challenging. Herein, we employed a multi-scale assembly strategy to construct lignin-based organic–inorganic supramolecular aggregates (LSA) to prepare nitrogen and oxygen co-doped porous carbon nanosheets (S-NLPC), achieving an exceptionally high specific surface area of 2848.1 m² g⁻¹, a hierarchical porous structure, and substantial levels of nitrogen and oxygen doping (N: 4.0 at% and O: 8.9 at%). The carbon nanosheets saturated with customized micro–mesopores significantly enhance the kinetics of ion transport and storage, while the nitrogen and oxygen doping improves the accessibility of high-density active sites and introduces additional chemisorption sites. As a result, the ZIHCs utilizing S-NLPC as the cathode demonstrate an enhanced specific capacitance of 433 F g⁻¹ (192.4 mA h g⁻¹), superior energy density of 154.3 W h kg⁻¹ at 80.2 W kg⁻¹, and remarkable cycling stability with a capacity retention of 90.2% after 20 000 cycles at 5 A g⁻¹. Furthermore, ex situ characterization reveals that the superior zinc ion storage performance of S-NLPC is primarily attributed to the reversible chemisorption of oxygen functional groups and the co-adsorption mechanism of Zn²⁺ and H⁺. This work presents a novel strategy for constructing lignin-based inorganic–organic aggregates utilizing multi-scale forces, providing new insights into the structural design of carbon-based cathodes for high-performance ZIHCs.