Turbocharged supercapacitors from new ionic liquids

Turbocharged supercapacitors from new ionic liquids

Wed, 02/10/2019


Publication by Laboratoire de chimie, in Nature Materials, on August 2019.

A new article in Nature Materials describes the discovery of a new class of electrolytes, which can improve energy storage efficiency in supercapacitors.

A team of scientists from US, France, UK and Australia has worked out a way to improve energy storage devices called supercapacitors, by designing a new class of ionic liquids based on common, non-toxic chemicals.

The Nature Materials paper explains why these new ionic liquids, are better electrolytes than current materials and can improve supercapacitors.  

Currently, aqueous and organic electrolytes are used, but more recently, researchers and manufacturers have been testing ionic liquids instead to boost performance. Although ionic liquids are salts, at room temperature they are surprisingly not crystalline solids: as their name suggests they are in fact liquids. This gives ionic liquids numerous advantages over conventional electrolytes because they are stable, non-flammable, and often much more environmentally friendly.

To explore the exciting potential offered by ionic liquids for emerging electrochemical technologies the authors designed a new set of highly efficient detergent-like ionic liquid electrolytes and explained how they work at electrode surfaces. Understanding how they operate will help design even more efficient devices for storing electrical energy.

“We engineered a new class of ionic liquids that can store energy more efficiently” says Xianwen Mao (MIT, USA), one of the authors of the study. “These detergent-like ionic liquids can self-assemble into sandwich-like bilayer structures on electrode surfaces. And that is very reason why they give better energy storage performance.”

Typically, for electrolytes in contact with a charged electrode, the distribution of ions is dominated by electrostatic Coulombic interactions. However, this distribution can be controlled by making the ionic liquids soap-like, or amphiphilic, so that the molecules now have separate polar and non-polar domains, exactly like common detergents. These soap-like electrolytes then spontaneously form bilayer structures on the electrode surfaces, leading to much improved energy storage capabilities. The researchers found that temperature and applied voltage also affect the energy storage performance.

This new class of electrolytes may be suitable for challenging operations, such as oil drilling and space exploration, but they may also pave the way to new and improved supercapacitors in hybrid cars. These devices are essential components in modern hybrid cars, and can outperform batteries in terms of higher power and better efficiency. This is particularly the case during regenerative braking where mechanical work is turned into electrical energy, which can be stored quickly in supercapacitors ready to be released. This reduces energy consumption and is much more environmentally friendly. More importantly, using the new electrolytes such as developed in this study, future supercapacitors may even be able to store more energy than batteries, potentially replacing batteries in applications such as electrical vehicles, personal electronics, and grid-level energy storage facilities.

Source: Self-assembled nanostructures in ionic liquids facilitate charge storage at electrified interfaces. Xianwen Mao, Paul Brown, Ctirad Červinka, Gavin Hazell, Hua Li, Yinying Ren, Di Chen, Rob Atkin, Julian Eastoe, Isabelle Grillo, Agilio. A. H. Padua, Margarida. F. Costa Gomes et T. Alan Hatton. Nature Materials, August 2019. DOI : 10.1038/s41563-019-0449-6


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