Three dimensional graphene: A prospective architecture for high performance supercapacitors

Graphene has been studied extensively owing to its unique two dimension structure, high conductivity, superior electron mobility, and extremely high specific surface area. The prompt progress in the applications of graphene over the past several years has resulted in remarkable achievements in a range of fields, such as electronics, sensors, photocatalysis, and energy conversion and storage. The two dimensional planar structure of graphene makes it compatible with applications in traditional electronic device architectures. On the other hand, the applications of graphene-based materials in photocatalysis, sensing, or supercapacitor fields often require graphene materials with higher surface areas. Therefore, the performance of supercapacitors employing 2D planar graphene architectures is still unsatisfactory. To develop high performance supercapacitors, the integration of 2D graphene sheets into 3D macroscopic assemblies has attracted the attention of both academia and industry. This is because 3D graphene structures can provide ultra-large accessible surface areas for synthesizing electric double layers and facile routes for electron and electrolyte transportation in interconnected conductive networks. Therefore, supercapacitors with 3D graphene-based materials, as active electrodes, are expected to show excellent performance. This critical review gives an overview of the progress in the fabrication of 3D graphene-based supercapacitors and their structural achievements. The electrochemical performance of supercapacitors based on 3D graphene composite systems, such as 3D graphene/polymer and 3D graphene/metal oxide composites, are also introduced and discussed to provide useful insight for the design and fabrication of high performance SCs.