Electrochemical supercapacitors are emerging devices of prime importance in energy sustainability due to their superior characteristics, unmatched by any other charge storage device. These exceptional properties include: 1) high power densities at relatively high energy densities and 2) long cycle life. These characteristics have already been exploited in various applications such as power electronics, large scale transport systems comprising subway trains and buses, energy storage at intermittent generators including windmills, and smart grid applications. Smart grid needs will include grid stability, frequency smoothing, peak shifting, and frequency regulation. This interest has spurned a large number of interesting technologies including the evolution of new materials for use in the electrodes such as graphene, transition metal oxides, and transition metal nitrides. The use of non-aqueous electrolytes and ionic liquids has also led to very high energy densities. The challenge however, lies in maintaining cyclability and stability at high rates.