High-specific-energy aqueous supercapacitor with extended operating potential using trichloroacetic acid electrolyte

Extending the operating potential of electrolytes is an efficient strategy to improving the energy density of aqueous supercapacitors. In this work, trichloroacetic acid (TCA) is firstly developed to be an efficient acid electrolyte with extended operating potential to improve the energy density of the aqueous carbon-based supercapacitors. Meanwhile, a hierarchical porous carbon (HPC) with a high specific surface area of up to 3356 m2 g−1 derived from inedible fruits of flowering plums is prepared to match the newly developed TCA electrolyte. The prepared HPC exhibits a high specific capacitance of up to 460 F g−1 in the TCA electrolyte at 1 A g−1. The symmetric supercapacitor device based on the prepared HPC and TCA electrolyte can stably work at 1.3 V with excellent cycle durability, more than 95.4% of initial specific capacitance is reserved after 20000 cycles. Meanwhile, high specific energy of 18.8 Wh kg−1 is delivered at 203 W kg−1, which value is 2.38 times higher than the device using H2SO4 electrolyte. Energy density of the acidic aqueous supercapacitors can be dramatically improved by employing the newly developed TCA electrolyte while the large power density and excellent cycle durability of carbon-based supercapacitors can be well retained. [Display omitted] •TCA is firstly developed to be an efficient acid electrolyte for aqueous supercapacitors.•A biomass-derived HPC with a SSA of up to 3356 m2 g−1 is prepared to match TCA electrolyte.•High specific capacitance of 460 F g−1 is achieved within a potential window of −0.3−1.0 V.•The assembled supercapacitor can stably work under 1.3 V with excellent cycle durability.•High specific energy of 18.8 Wh kg−1 is delivered by the assembled aqueous supercapacitor.