Morphology-controllable synthesis of nanocarbons and their application in advanced symmetric supercapacitor in ionic liquid electrolyte

Abstract Controllable synthesis of nanocarbons with tunable morphologies from sustainable biomass through facile one-step route for ionic liquid based supercapacitors with high energy density and high power characteristics is of great interest but remains an ongoing challenge. Herein, we report the design and synthesis of nanocarbons with tunable morphologies (i.e., honeycomb-like porous carbons, carbon nanosheets and irregular-shaped carbon microparticles) from sustainable pine barks through reliable one-step chemical activation process. We found that the honeycomb-like porous carbons can be produced via direct KOH activation while the uniform carbon nanosheets were obtained by employing magnesium powder as the reactive self-sacrificing template. These three samples have different morphologies and textural properties render them totally disparate electrochemical performance in ionic liquid electrolyte. Benefiting from its distinct structural advantages, the as-obtained porous carbon nanosheets has excellent electrochemical capacitive performance including large specific capacitance (193 F/g at 1 A/g), superior rate capability (superior specific capacitance retention of 69.4% at 40 A/g), good cycling stability (good capacitance retention after 8000 cycles) and integrated high energy density& high power characteristics (excellent energy density of 55.8 Wh/kg even at an ultrahigh power density of 39.375 kW/kg). We believed that this work reported here not only provides a versatile strategy towards nanocarbons with tunable morphologies from sustainable biomass but also sheds some new light to efficiently regulate the morphologies of nanocarbons for electrochemical energy storage applications.