LAUSR

Abstract Improving the energy density of supercapacitors without sacrificing their large charge storage capacity, high power density, and excellent cycle stability is extremely attractive for researchers. Herein, we develop a mixed alkaline aqueous (MAA) electrolyte with widened operation voltage. Meanwhile, a biomass-derived interconnected hierarchical porous carbon (IHPC) with controlled pore size distribution, ultra-large specific surface area (up to 3463 m2 g−1), and high conductivity (up to 8.7 S cm−1) is prepared to match this electrolyte. The obtained IHPC can stably charge-discharge within 1.3 V and exhibit a high specific capacitance of up to 462 F g−1 in the MAA electrolyte. The symmetrical supercapacitors based on the prepared IHPC and the MAA electrolyte deliver a high specific energy of up to 19.7 Wh kg−1 at a specific power of 203 W kg−1, while a specific energy of 14.5 Wh kg−1 is recorded at a large specific power of 12.2 kW kg−1. Meanwhile, the assembled devices based on the MAA electrolyte exhibit good rate capability and excellent cycle stability, up to 89% of initial specific capacitance is retained even at a large current density of 20 A g−1, and more than 91.4% of initial specific capacitance is retained after 30,000 cycles.