Introduction to supercapattery

The accelerated research for alternative energy resources also catalyzes the development of efficient electrochemical energy systems that can meet the latest technological demands. Although supercapacitors and batteries are being extensively used, their stand-alone efficiencies are still not enough to fulfill the quest for energy demand and supply. Hybrid energy storage devices that can combine the features of batteries and supercapacitors are expected to bridge the performance gap between the two technologies. This chapter will give an insight into a hybrid energy storage system, which is named the supercapattery. The features of supercapattery, which can tackle current challenges faced by existing energy storage technology, will be discussed. Unfortunately, a lot of misleading concepts are presented in the literature about the charge storage mechanism of different materials and, ultimately, they are categorized wrongly. This has led to the elevated values of performance parameters of energy storage materials compared to their original values. These issues are also highlighted critically. Especially, the difference between pseudocapacitive and battery-grade materials is elaborated in detail. Moreover, the situations where a battery-grade material can give the electrochemical signature of pseudocapacitive materials is also discussed from the electrochemical point of view. Overall, this chapter will give a brief introduction of supercapattery and will help in understanding the differences between pseudocapacitive materials and battery materials.