Envisaging Future Energy Storage Materials for Supercapacitors: An Ensemble of Preliminary Attempts

Recent developments in supercapacitor technology in terms of materials and devices are reviewed herein. Beyond the conventional materials (i. e., carbonaceous matters, metallic compounds and conducting polymers), various multifunctional materials are reported in literature as future supercapacitive materials. A comprehensive account on such materials is lacking due to the diversified electrochemical characteristics of these materials. In this review, we bring all such non-conventional multifunctional energy storage materials under a same umbrella for summarizing the recent advancements in supercapacitors. The envisaged multifunctional materials include metal-organic-frameworks (MOFs), covalent-organic-frameworks (COFs), heteroatom-doped carbonaceous materials, biomass-derived porous carbons, black phosphorous, mixed conductors, perovskite nanoparticles, polyoxometalates (POMs), redox active electrolytes, slurry materials for flow supercapacitors, thermal self-charging materials, thermal self-protective materials, piezoelectric materials and electrochromic materials. Inherent pros and cons of each class of material are discussed, and materials modifications towards the successful device fabrications are highlighted herewith. While the MOF-based supercapacitors are drawing some attentions, other non-conventional energy storage materials are truly in the nascent stage of developments. This review culminates with summary and proposed future directions for product developments. In brief, this article provides a holistic view regarding all non-conventional multifunctional energy storage materials for future supercapacitor technology.