Synthesis of Microscopic 3D Graphene for High-Performance Supercapacitors with Ultra-High Areal Capacitance

Despite graphene being considered an ideal supercapacitor electrode material, its use in commercial devices is limited because few methods exist to produce high-quality graphene at a large scale and low cost. A simple method is reported to synthesize 3D graphene by graphenization of coal tar pitch with a K₂CO₃ catalyst. This produces 3D graphenes with high specific surface areas up to 2113 m² g^-1 and exceptional crystallinity (Raman I_D/I_G as low as ≈0.15). The material has an outstanding specific capacitance of 182.6 F g^-1 at a current density of 1.0 A g^-1. This occurs at a mass loading of 30 mg cm^-2 which is 3 times higher than commercial requirements, yielding an ultra-high areal capacitance of 5.48 F cm^-2. The K₂CO₃ is recycled and reused over 10 cycles with material quality and electrocapacitive performance of 3D graphene retained and verified after each cycle. The synthesis method and resulting electrocapacitive performance properties create new opportunities for using 3D graphene more broadly in practical supercapacitor devices.