Sustainable Low-Temperature Activation to Customize Pore Structure and Heteroatoms of Biomass-Derived Carbon Enabling Unprecedented Durable Supercapacitors

Due to the unreasonable configuration of the porous structure and heteroatoms, the heteroatom-doped hierarchical porous carbon employed in supercapacitors generally demonstrates an imbalance in durability and rate performance. Herein, we have exploited a mild and sustainable one-step activation route with KMnO4 as the activator to synthesize a nitrogen/oxygen dual-doped hierarchical porous carbon (MHPC) with quasi-ordered mesopores. The evolution mode and detailed activation mechanism of KMnO4 have been verified by an operando XRD characterization. The three-electrode measurements reveal that as-synthesized MHPCs demonstrate outstanding electrochemical performance, and further kinetic assessments disclose their surface-controlled dominant fast electrochemical kinetics. Owing to the prominent hierarchical porous structure, considerable heteroatom content, and fast electrochemical kinetics, the constructed symmetric supercapacitors exhibit a high specific capacity (255.5 F g(-1) at 1 A g(-1)), outstanding rate performance (85% retention at 50 A g(-1)), and unprecedented durability (97.8% capacity retention after 100,000 cycles). Furthermore, all-solid-state symmetric supercapacitors still present high energy and power density (7.1 Wh kg(-1) at 244 W kg(-1)) as well as a remarkable lifespan (89.5% capacitance retention over 50,000 cycles). This work has successfully exploited a new activation method to synthesize the biomass-derived carbon with a prominent hierarchical porous structure.