Nanotechnology has opened up new frontiers by offering unique enabling technologies and new materials for energy storage. In particular, graphitic carbon nanomaterials (e.g. carbon nanotubes, graphene sheets) have been playing a more and more important role in the development of high-performance supercapacitors 4, 5. The aim of this article is to summarize recent progress in the development of supercapacitors (especially electrical double layer capacitors) based on carbon nanomaterials and to provide various rational concepts for materials engineering to improve device performance.