Advancing Energy Storage Technology through Hybridization of Supercapacitors and Batteries: A Review on the Contribution of Carbon-Based Nanomaterials

Fast depletion of fossil fuel and other non-renewable energy resources with their negative environmental impact have raised the quest for eco-friendly and sustainable energy resources. Sustainable energy resources such as solar and wind energy are periodical. Therefore, such energy resources can only be effectively utilized with advanced energy storage technology. Currently, various energy storage technologies such as batteries and supercapacitors are available with various energy storage properties. For instance, batteries are characterized with high energy and low power density. On the other hand, supercapacitors are low energy and high power density devices. The high power density of supercapacitors results to their faster charging and discharging capability compared to batteries. While batteries can accommodate higher energy compared to supercapacitors. Therefore, to obtain single energy storage material/device with both high energy and power density is a challenge in the energy storage sector. However, various efforts have been made to address this challenge through combinations of various materials or devices. For instance, carbon-based nanomaterials such as graphene and carbon nanotubes have been extensively studied in design of supercapacitors for high energy storage density. While supercapacitors and batteries have been hybridized on the effort to obtain energy storage device with both high energy and power density for advanced energy storage technology. Therefore, this review looks into the contribution of carbon-based nanomaterials in improving energy storage density of supercapacitors and their hybridization with batteries as the way forward to obtain energy storage materials/devices with both high energy and power density for advanced energy storage technology.