New Insights into the Operating Voltage of Aqueous Supercapacitors

Abstract

The main limitation of aqueous supercapacitors (SCs) lies in their narrow operating voltages, especially when compared with organic SCs. Fundamental understanding of factors relevant to the operating voltage helps providing guidance for the assembly of high-voltage aqueous SCs. In this regard, this concept analyzes the deciding factors for the operating voltage of aqueous SCs. Strategies applied to expand the operating voltage are summarized and discussed from the aspects of electrolyte, electrode, and asymmetric structure. Dynamic factors associated with water electrolysis and maximally using the available potential ranges of electrodes are particularly emphasized. Finally, other promising approaches that have not been explored and their challenges are also elaborated, hoping to provide more insights for the design of high-voltage aqueous SCs.

Biomass‐Derived Carbon: A Value‐Added Journey Towards Constructing High‐Energy Supercapacitors in an Asymmetric Fashion

“…The wide application of SSCs is mainly held back by their low energy density and narrow operating voltage window. [50] The type of electrode materiala nd electrolyte playa vital role in determining the potentialw indow of an aqueous electrolyte based SC. The thermodynamically stable voltage window of aw ater molecule is 1.23 V. However,f ew reports are availablet oe nhance the energy density of the SCs by optimizing the surfacec hargea nd enlarging the potential window higher than 1V;t hus demonstrating that there is alwaysu nusedp otential beyond the upper and lower limits of potentialb ased on aqueous SSCs.…”

High‐Performance and Ultra‐Stable Aqueous Supercapacitors Based on a Green and Low‐Cost Water‐In‐Salt Electrolyte

“…where E is the energy density, C is the capacitance, and V is the operation voltage window . Since the energy density is proportional to the voltage squared, raising the operating voltage is considered as an effective strategy to improve the energy density of devices . Electrolytes, the source of the ions that conduct between two electrodes, play a very important role in determining the operating voltage and the overall performance of devices .…”

Dual‐Strategy to Construct Aqueous‐Based Symmetric Supercapacitors with High Volumetric Energy Density

“…In comparison, aqueous electrolytes have shown many advantages over IL and organic electrolytes, such as safety, low cost, non‐toxicity and easy device assembly . However, the ESW of the aqueous electrolyte is extremely limited by the decomposition voltage of water of 1.23 V, resulting in limited practical applications . Surprisingly, Suo et al.…”