Researchers Develop a New Way to Improve Supercapacitors

An international team of researchers, including a chemistry professor from the University of Bristol, has developed a new method to enhance supercapacitors—energy storage devices—by creating a new class of detergents that are chemically associated with laxatives.

Recently reported in the journal Nature Materials, the paper shows why these detergents, known as ionic liquids, are better electrolytes when compared to existing materials and can enhance supercapacitors.

Although organic and aqueous electrolytes are currently utilized, manufacturers and researchers have been recently testing ionic liquids rather than increased performance.

While ionic liquids exist as salts at room temperature, they are unexpectedly not crystalline solids but actually liquids as their name suggests. This provides ionic liquids with many benefits over traditional electrolytes because they are non-flammable, stable, and usually much more eco-friendly.

To study the fascinating potential provided by ionic liquids for evolving electrochemical technologies, the researchers created a unique set of highly efficient detergent-like ionic liquid electrolytes and elucidated how they operate at the surfaces of electrodes.

Interpreting the working of these electrolytes will help in designing much more efficient devices that can be used for storing electrical energy.

To make this discovery required a team of scientists with a very diverse skill set, spanning chemical synthesis, advanced structural, microscopy and electrical techniques as well as computational methods. This work demonstrates the power of scientific research ‘without borders’, the groups from different nations contributed their own expertise to make ‘the whole greater than the sum of parts’.

Julian Eastoe, Study Co-Author and Professor, School of Chemistry, University of Bristol

Co-author, Xianwen Mao, from the Massachusetts Institute of Technology (MIT), added: “We engineered a new class of ionic liquids that can store energy more efficiently. These detergent-like ionic liquids can self-assemble into sandwich-like bilayer structures on electrode surfaces. And that is the very reason why they give better energy storage performance.”

Normally, for electrolytes that come in contact with a charged electrode, electrostatic Coulombic interactions dominate the distribution of ions. Conversely, the distribution of ions can be regulated by making the ionic liquids amphiphilic, or soap-like, so that the molecules currently have individual non-polar and polar domains, precisely like normal detergents.

Following this, these soap-like electrolytes unexpectedly create bilayer structures on the surfaces of electrodes, resulting in relatively enhanced energy storage capabilities. The researchers discovered that energy storage performance is also influenced by temperature and applied voltage.

This new set of electrolytes could be used in challenging operations, like space exploration and oil drilling; however, they may also lead to the development of new and enhanced supercapacitors in hybrid cars. Such devices are important components in contemporary hybrid cars and can outpace batteries in terms of better efficiency and higher power.

This is specifically true during regenerative braking in which mechanical work is converted into electrical energy. This electrical energy, in turn, can be stored rapidly in supercapacitors ready to be discharged.

This not only decreases energy consumption but is also much more eco-friendly. More significantly, with the help of novel electrolytes like those created in this analysis, upcoming supercapacitors may be able to store more amounts of energy when compared to batteries, possibly substituting batteries in applications like grid-level energy storage facilities, personal electronics, and electrical vehicles.