Biomass-Derived Graphene-Based Materials Embedded with Onion-Like Carbons for High Power Supercapacitors

We report a facile method to produce composites of hierarchically porous graphene-based materials embedded with onion-like carbons (Gr-OLCs) for high power density supercapacitors. Gr-OLCs were produced from the mixture of glucose, thiourea, and ammonium chloride, through stepwise reactions including a condensation reaction, subsequent blow into three-dimensional (3D) structure, and carbonization process. Owing to its high surface area, hierarchical pore distribution, and interconnected carbon networks embedded with onion-like carbons, this carbon showed high specific capacitance of 140 F g ⁻¹ even at a high current density of 64 A g ⁻¹ . Interconnected carbon networks and hierarchical pore structrues served to facilitate the movement of electrolyte ions within the electrode and provide an efficient pathway for the movement of charge carriers, resulting in an exceptionally high power density of 1,737 kW kg ⁻¹ with an energy density of 30 Wh kg ⁻¹ at current density of 256 A g ⁻¹ . Studies on the complex capacitance revealed that a supercapacitor with these carbon electrodes exhibited stable energy storage features with minimal capacitive loss, achieving both high power and energy densities. This work provides a new type of carbon-based electrode materials that can meet the requirements for high power energy storage devices.