Dense organic molecules/graphene network anodes with superior volumetric and areal performance for asymmetric supercapacitors†
Volumetric and areal capacitance are as important as gravimetric capacitance for small energy storage devices. However, achieving both a high volumetric and a high areal capacitance is still a big challenge. Here we report a dense redox organic molecules/graphene network, in which highly redox active sodium anthraquinone-2-sulfonate (AQS) molecules are anchored on interconnected and highly conductive graphene sheets by noncovalent π–π interactions to form high-performance supercapacitors (SCs). The AQS/graphene (AQS/G) has a high volumetric specific capacitance of up to 650 F cm−3 and an excellent rate capability (422 F cm−3 even at 30 A g−1), as well as a good cycling stability. A maximum areal specific capacitance of 13.3 F cm−2 is achieved at a high mass loading of 32 mg cm−2 (200 μm in thickness), which is amongst the highest values recorded for organic-based materials for SCs. An asymmetric SC constructed with AQS/G and RuO2/graphene delivers a maximum volumetric energy density of 44 W h L−1. This outstanding performance is attributed to the excellent electron conduction and ion transport provided by the dense but interconnected graphene network. This work suggests a new way for organic-based high-performance electrode materials to be used in electrochemical energy storage devices.