sp3-Defect and pore engineered carbon framework for high energy density supercapacitors

Carbon based supercapacitor suffers from low energy density due to inefficient electrical double-layer storage mechanism. Herein, sp(3)-defect engineered sp(2) carbon framework with hierarchical porous architecture (HCF) is developed via a one-step chemical vapor deposition (CVD) method for high energy density supercapacitor. Theoretical calculations are performed firstly and results reveal that the sp(3)-defects in host sp(2) carbon sheets promote the sodium-ion storage performance attributed to the reduced energy barrier of sodium-ion adsorption and increased density of states around Fermi level. The HCF is extensively characterized and the results show that the density of sp(3)-defects and hierarchical micro-meso-macropore size of HCF can be well tuned by regulating the CVD temperature. Owing to reasonably engineered sp(3)-defects (similar to 32.8 at%), well-defined multiscale pore architectures and wide interlayer in HCF, extra pseudocapacitive sodium-ion storage sites are obtained and therefore a capacitance up to 558.8 F/g is achieved. The resultant HCF based symmetric supercapacitor device gives a high energy density of 38.76 Wh/kg at a power density of 375.04 W/kg and still retains 30.00 Wh/kg at a high power density of 5970.15 W/kg. This work provides a facile strategy to explore the intrinsic defect in carbon electrode materials for high performance energy storage systems.