Lignosulfonate-Assisted Synthesis of Porous Carbon-Supported MnO2 Composites with Reinforced Interface Bonding for High-Performance Asymmetric Supercapacitors

Carbon/transition metal oxide composites exhibit promising potential as electrode materials for energy storage, but regulating their interfacial composite structures remains a formidable challenge. In this work, we develop a lignosulfonate-assisted synthesis strategy to fabricate a porous carbon-supported MnO2 composite (LSC/MnO2-2) with a robust interface for asymmetric supercapacitors (ASCs). The functionalized lignin porous carbon, achieved through π–π interactions with lignosulfonate, exhibited improved dispersibility, thereby facilitating the deposition of MnO2 onto the carbon matrix. Consequently, LSC/MnO2-2 demonstrates uniform MnO2 loading and enhanced interfacial bonding. The robust interaction between Mn sites and the lignosulfonate-functionalized carbon substrate can promote electron transfer and ion transfer kinetics, effectively activating the electrochemical activity of MnO2. The as-prepared LSC/MnO2-2 demonstrates high specific capacitances of 750 F/g at 0.5 A/g and 400 F/g at 10.0 A/g in a 1 M KOH electrolyte. Furthermore, the assembled ASC exhibits an outstanding energy density of 54.4 Wh/kg at 998.2 W/kg and excellent cyclic stability (94.7% retention over 10,000 cycles at 2.0 A/g). This study presents an alternative method to precisely control the deposition of metal oxides onto carbon materials, aiming to enhance the performance of carbon composites.