Electric double layer capacitors, also called supercapacitors, ultracapacitors, and electrochemical capacitors, are gaining increasing popularity in high power energy storage applications. Novel carbon materials with high surface area, high electrical conductivity, as well as a range of shapes, sizes and pore size distributions are being constantly developed and tested as potential supercapacitor electrodes. This article provides an overview of the electrochemical studies on activated carbon, carbide derived carbon, zeolite-templated carbon, carbon aerogel, carbon nanotube, onion-like carbon, and graphene. We discuss the key performance advantages and limitations of various nanostructured carbon materials and provide an overview of the current understanding of the structure–property relationships related to the transport and adsorption of electrolyte ions on their surfaces, specific and volumetric capacitance, self-discharge, cycle life, electrolyte stability, and others. We discuss the impact of microstructural defects, pore size distribution, pore tortuosity, chemistry and functional groups on the carbon surface, nanoscale curvature, and carbon-electrolyte interfacial energy. Finally, we review state-of-the art commercial large scale applications of supercapacitors, including their use in smart grids and distributed energy storage, hybrid electric and electric vehicles, energy efficient industrial equipment, ships, wind power stations, uninterruptible power supplies, power backup, and consumer devices. WIREs Energy Environ 2014, 3:424–473. doi: 10.1002/wene.102

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Conflict of interest: The authors have declared no conflicts of interest for this article.