Materials for energy storage: Review of electrode materials and methods of increasing capacitance for supercapacitors

Supercapacitors (SCs) have shown great promise as a possible solution to the increasing world demand for efficient energy storage. Two types of mechanisms for SCs exist (double-layer and pseudocapacitive), and each type utilizes a wide variety of materials. In this review, a detailed overview of the mechanisms employed by SCs is provided in the introduction, and many studies are compared in order to determine which materials produce electrodes with high capacitance and cyclability in SCs, and to summarize and gauge the state of such research. The types of materials looked at include graphene and graphene nanocomposites, activated carbons from renewable materials, conducting polymers, and transition metal dichalcogenides. Additionally, different methods of activation that are meant to increase specific capacitance are examined. Among the dozens of materials found in the literature during this study, the ones that exhibited the highest specific capacitances are rGO/PANI (Reduced Graphene Oxide/Polyaniline), and PANI-NFS/GF (Polyaniline Nanofiber Sponge Filled Graphene Foam) demonstrated impressive performances. These materials all exceeded the current expectations of SCs by remarkable amounts, and more research into similar materials is highly encouraged. As more fundamental studies carried out for understanding the mechanisms of SCs, energy density and specific capacitance values continue to improve. Production of SCs from renewable materials encourage optimism for environmentally friendly options soon becoming feasible for use on larger scales.