Biomass-derived biochar materials as sustainable energy sources for electrochemical energy storage devices

High power and energy density electrochemical energy storage devices are more important to reduce the dependency of fossil fuels and also required for the intermittent storage of renewable energy. Among various energy storage devices, carbon serves as a predominant choice of electrode material owing to abundance, electrical conductivity, and control over the intrinsic properties. In this context, biomass, an abundant, inexpensive, and renewable source to produce biochars has gained significant research attention not only to mitigate the environmental concern, but also to promote the development of sustainable energy storage applications. In this review, recent progresses towards the conversion and efficient utilization of biomass and its derived biochar as electrode materials for energy storage devices, including supercapacitors and batteries (Li-ion, Na-ion, Li–S, and Metal-air) is summarized and discussed. The various sources of biomass, processes to derive biochar from the biomass, and the effects of various parameters involved in the synthesis methods to tailor its morphology, surface area, pore structure, and composition of the biochars along with the structure-activity relationship and technology-to-market is elaborated, which will lead to remarkable exploration of biomass towards realizing sustainable energy storage devices.