Design principles of high-voltage aqueous supercapacitors

A principal challenge in the 21st century is reliable energy storage, which is vital to deal with the high safety risk and insufficient energy density of current commercial energy storage devices. An aqueous supercapacitor (AqSC) is one of the most promising candidates for future high safety energy storage devices owing to the non-inflammability, non-toxicity, high ionic conductivity, low cost of aqueous electrolytes, and the high power energy and stability of supercapacitors. However, the low energy density caused by the narrow thermodynamically stable potential range of aqueous electrolytes is the main obstacle to realize the large-scale application of AqSCs. To fabricate high energy density AqSCs, an enormous effort has been made to extend their operating voltage in the past few decades. Herein, we review the recent progresses on designing high-voltage AqSCs, with the main focus on the mechanism of AqSCs, understanding of electrochemical electrode potential, and the recent strategies for extending the voltage window of AqSCs. First, the background, energy storage mechanism, and device configurations for AqSCs are summarized. Then, we move to the origin of electrochemical potential and the recent strategies for designing high-voltage AqSCs. This review also briefly discusses the challenges facing AqSCs and our perspectives in future research. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

The article discusses the principal challenge of reliable energy storage in the 21st century, focusing on the potential advantages and challenges facing aqueous supercapacitors as future high safety energy storage devices, as well as the efforts made in the past few decades to design high energy density AqSCs.