Coal-Derived Activated Carbon for Electrochemical Energy Storage: Status on Supercapacitor, Li-Ion Battery, and Li–S Battery Applications

In this era of exponential growth in energy demand and its adverse effect on global warming, electrochemical energy storage systems have been a hot pursuit in both the scientific and industrial communities. In this regard, supercapacitors, Li-ion batteries, and Li–S batteries have evolved as the most plausible storage systems with excellent commercial adaptations. Intending to get the best performance from these systems, researchers all over the world have been engaging to develop various new methods for the synthesis of advanced carbon materials with a target of economical viability, abundance, low cost, and ease of preparation. Among them, activated carbon has proven to be an attractive electrode material due to its many advantageous properties such as a large surface area, high pore density, good conductivity, low cost, and good mechanical and chemical stability compared to other alternatives, such as high-cost graphene, carbon nanotubes, Mxenes, transition metal complexes, and conducting polymers. Among the numerous synthetic and biological resources that are used for the synthesis of activated carbon, coal/coal-like materials have found tremendous importance in recent times due to their relative abundance, extremely low cost, and excellent large-scale production possibilities. The present review attempts to collect all the significant innovations carried out for the use of cheap and economically viable coal-derived/-based activated carbon and its composites in supercapacitors, Li-ion batteries, and Li–S batteries and to critically evaluate their comparative performances. The progress in advanced three-dimensional printing technology for these energy storage applications is also discussed. The highlight of this review is also to assess the challenges that remain for the synthesis of high-performance electroactive-activated carbon materials from coal-based resources as alternative electrode materials, which would become promising candidates in the foreseeable future.