Remarkably improving the specific energy of supercapacitor based on a biomass-derived interconnected hierarchical porous carbon by using a newly-developed mixed alkaline aqueous electrolyte with widened operation voltage

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.