Controlling the conductivity and microporosity of biocarbon to produce supercapacitors with battery-level energies at an ultrahigh power

Abstract

In order to meet the demands of new-generation electric vehicles that require high power output (over 15 kW/kg), it is crucial to increase the energy density of carbon-based supercapacitors to a level comparable to that of batteries, while maintaining a high power density. We report a porous carbon material produced by immersing poplar wood (PW) sawdust in a solution of KOH and graphene oxide (GO), followed by carbonization. The resulting material has exceptional properties as an electrode for high-energy supercapacitors. Compared to the material prepared by the direct carbonization of PW, its electrical conductivity was increased from 0.36 to 26.3 S/cm. Because of this and a high microporosity of over 80%, which provides fast electron channels and a large ion storage surface, when used as the electrodes for a symmetric supercapacitor, it gave a high energy density of 27.9 Wh/[email protected] kW/kg in an aqueous electrolyte of 1.0 mol/L Na₂SO₄. The device also had battery-level energy storage with maximum energy densities of 73.9 Wh/[email protected] kW/kg and 67.6 Wh/kg@40 kW/kg, an ultrahigh power density, in an organic electrolyte of 1.0 mol/L TEABF₄/AN. These values are comparable to those of 30−45 Wh/kg for Pb-acid batteries and 30−55 Wh/kg for aqueous lithium batteries. This work indicates a way to prepare carbon materials that can be used in supercapacitors with ultrahigh energy and power densities.

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