Rapid developments in portable and miniaturized high power electronic devices have taken place over the time. Energy storage devices are extensively being researched to meet the ever-increasing energy demands. There is a need to develop greener and sustainable materials for harnessing energy and its storage with some potential applications. Numerous multicomponent nanostructured materials are reported to be used to improve the efficiency and performance of a variety of electronic devices. Among a host of the nanomaterials explored so far, carbon nanotubes have dragged much attention and this is attributed to their novel properties. Lot of active research is being dedicated toward improving the gravimetric performance and enormous achievements have been reported. Gravimetric performance measures are conventionally used to assess the performance of these devices, but this does not give a realistic picture of the device capacity. Volumetric and areal performances are found to be more accurate and reliable measures for evaluating the capacity of these high-powered compact devices. Nanomaterials possess high surface area but low volumetric densities which result in poor performance and limit their applicability. This chapter highlights various approaches to achieve high gravimetric and volumetric capacity using carbon nanotubes.