Journey from supercapacitors to supercapatteries: recent advancements in electrochemical energy storage systems

Generation, storage, and utilization of most usable form, viz., electrical energy by renewable as well as sustainable protocol are the key challenges of today’s fast progressing society. This crisis has led to prompt developments in electrochemical energy storage devices embraced on batteries, supercapacitors, and fuel cells. Vast research and development are being executed worldwide on each of these systems. Although fuel cells and batteries possess higher energy density but excessive installation cost, bulkiness, low power capabilities, and short life time are major limitations till date. The performances of supercapacitors at present lie in-between these batteries and conventional capacitors, hence serve as supporting or secondary devices for uninterrupted power supply systems. Nonetheless, supercapacitors possess some indigenous qualities such as light weight, easy portability, high cycle life, and low maintenance requirement with the potentiality for high specific and energy densities. These attractive features have proposed scientific challenges that have promoted the urge for replacing conventional massive, low-lasting batteries. In recent past, nano-composite materials have been developed with improved energy density to replace the “first-generation supercaps.” Moreover, hybridizing with high energy battery materials can successfully solve the existing limitation of the available supercapacitors without sacrificing their cycling performances substantially. Thus, a novel concept of “supercapatteries” (supercapacitors + batteries) has emerged combining the merits of the charge storage mechanisms of both batteries and electrochemical capacitors so as to attain improved electrochemical performances. At the same time, scientists are trying to pursue cost effective designing methods without compromising with device efficiencies. The paper outlines the progress of supercapacitor technology with special emphasis on the tuning of nature, composition, electronic, and structural designing of electrode materials and electrolytes, cell fabrication along with other related parameters that may assist in enhancing the overall electrochemical device performances.