Recent advances in materials and device technologies for aqueous hybrid supercapacitors

Abstract

Aqueous hybrid supercapacitors (AHSCs) offer potential safety and eco-friendliness compared with conventional electrochemical energy storage devices that use toxic and flammable organic electrolytes. They can serve as the bridge between aqueous batteries and aqueous super-capacitors by combining the advantages of high energy of the battery electrode and high power as well as long lifespan of the capacitive electrode. Over the past few decades, extensive research efforts have been devoted to developing advanced materials and fascinating device architectures for AHSCs. However, further development related to the compatibilities between the battery-type electrode and capacitive electrode remains stagnant mainly due to discrepancy encountered in terms of reaction kinetics and capacity. This review focuses on the recent progress made in the field of AHSCs via elucidating the main concepts on the design of battery and capacitive electrodes and emerging electrolytes. In particular, ingenious AHSCs that possess either better flexibility toward materials selection or better device functionality such as those with “dual-ion” energy storage mechanism and non-polarity feature are also discussed. Recent advances and unresolved issues in multivalent ion hybrid devices (in particular, zinc-ion AHSCs) are further outlined. Finally, future research directions and challenges for AHSCs are presented, which are anticipated to deliver higher energy and demonstrate greater multifunctionalities for more breakthrough technology applications.