Secondary capacitors and second cells are mostly used in large-capacity power storage devices such as energy storage system (ESS), and many studies are being conducted to improve the efficiency and economic feasibility of such energy storage devices. While porous carbon has been used as a carbon-based electrode material for energy storage devices, studies were recently conducted to enhance the electrode efficiency using carbon-based nanomaterials such as carbon nanotubes (CNTs) and graphene. CNT requires a metal catalyst for synthesis, and a post-treatment process must be followed to improve its purity. Also, it is difficult to accurately formulate and disperse CNT when it is used as an electrode material. As graphene has a one-dimensional planar structure, its reactivity is higher than that of CNT, which has a two-dimensional structure. It is difficult, however, to develop a large-scale and high-quality synthesis technology for the commercialization of graphene. Carbon nanowalls (CNWs), which were found during the synthesis of CNT, are carbon-based materials and have a two-dimensional structure in which several layers of graphene are vertically grown on a substrate. CNWs with this unique appearance have the largest reaction surface area among the carbon-based materials. As CNWs are carbon-based materials, they have high electrical conductivity and electron affinity. Therefore, they can be used as electrode materials to improve the performance of electrodes. The large-area mass production of CNWs is possible through the microwave plasma enhanced chemical vapor deposition(PECVD) method.