Recent developments in zinc metal anodes, cathodes, and electrolytes for zinc-ion hybrid capacitors

Abstract

Recent developments in Li-ion batteries, Na-ion batteries, and supercapacitors are redefining their applications in several portable and large-scale energy storage applications. However, the demand for energy storage devices with the combination of high energy density and high power density is rapidly increasing and research on hybrid-ion capacitors, which combines the benefits of battery and capacitors is gaining much momentum. The multivalent-ion-based energy storage device, zinc-ion hybrid capacitors (ZICs) are gaining attention as a low-cost and eco-friendly alternative to commercial lithium and sodium analogues for several energy storage applications. ZICs combine the benefits of batteries and capacitors, exhibiting a high energy-power density combination, and remarkable safety. The energy–power–cycle life metrics of ZICs are often controlled by the Zn metal anode, electrolytes, and cathode employed in the system. Research on ZICs are still in the nascent stage and requires a lot of attention to address the issues and to enable their use in commercial application. This review presents a comprehensive summary of recent developments in ZICs with particular emphasis on several materials and design strategies developed to address the key issues in ZICs. Moreover, the revolving issues with each component of ZICs, the strategies to overcome issues, and their influence on the performance of ZICs are briefly discussed. Recent trends in applications of emerging 2D materials, pseudocapacitive materials, MXenes, and flexible capacitors systems are also discussed as this could be a trendsetter for next-generation storage devices. Furthermore, a brief outlook and perspective on the future research of ZICs are provided, which will help the researcher to direct their future research towards the development of scalable next-generation energy storage systems.