Research published today in the journal Nature Materials describes research from an international team of scientists, which explains why detergents called ionic liquids could be better electrolytes than current materials in supercapacitors.
Supercapacitors are able to store large amounts of energy for a short period of time, and are often used in situations where batteries would charge too slowly.
Currently, aqueous and organic electrolytes are used, but recently researchers and manufacturers have been testing ionic liquids – which are, as the name suggests, a liquid at room temperature. This means they’re stable, non-flammable and often more environmentally friendly than conventional electrolytes used for energy storage.
The authors, part of an international team of scientists, designed a new set of detergent-like ionic liquid electrolytes, which are chemically related to laxatives, and described how they would work at the interface with electrodes inside a supercapacitor.
"We engineered a new class of ionic liquids that can store energy more efficiently,” said Xianwen Mao, from the Massachusetts Institute of Technology. "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."
Normally the distribution of electolytes in contact with a charged electrode is dominated by electrostatic Coulombic interactions. But by making the ionic liquids amphiphilic – with by hydrophilic and hydrophobic parts, like soap – the distribution of can be controlled.
These soap-like electrolytes form bilayer structures at the electrode surface, improving energy storage capabilities. It’s hoped that this new class of electrolytes could find uses in challenging environments such as oil drilling and space exploration, as well as paving the way for new and improved supercapacitor in hybrid cars, where they are used to store large amounts of energy during regenerative braking.
Eventually, future supercapacitors may be able to store more energy than batteries – allowing for quick charging vehicles and electronics, without some of the problems associated with lithium-ion cells.