‘Laxatives’ May Ease Challenge of Lithium-Ion Alternative

An international team of scientists reveal research into boosting supercapacitor performance as an alternative EV power source to Li-ion batteries.

January 1, 2020

Stuart Birch

Detergent-like ionic liquids on an electrode surface. (Brown)

The R&D dimension of the automotive industry often reveals novel solutions and cross-linking between materials, but a team of international scientists has come up with something truly unusual: boosting supercapacitor power and efficiency using newly developed “laxatives.” It’s all about developing improved electrolytes as part of a program to enhance supercapacitor performance, making them more practical with enhanced energy storage for use in hybrid and electric vehicles (EVs).

Dr. Gavin Hazell, pictured, said: “This is an attractive prospect for car manufacturers; the technology is affordable and scalable.” (University of Chester)

To do this, the team designed a new class of detergents involving the use of self-assembled nanostructures in detergent-like ionic liquids (IL), to facilitate improved charge storage at electrified interfaces. These detergents are chemically similar to human laxatives, said Dr. Gavin Hazell, a chemistry lecturer at the University of Chester’s Faculty of Science and Engineering, and a member of the international team: “A discovery of this kind utilizes scientists from across the globe. We have a very diverse set of skills including synthetic chemistry, advanced structural, microscopy and computational methods.”

The team’s findings (published in the journal Nature Materials) may contribute to the long hoped-for achievement of supercapacitors matching or exceeding the storage and power density of lithium-ion batteries. At present, automotive supercapacitors have only secondary roles such as harvesting energy via regenerative braking or e-turbocharging systems. Supercapacitors also can be used to supply rapid but brief energy-burst functions such as for stop-start ICE systems. And they can be used as an energy storage source by conventionally powered delivery vehicles that make many very short journeys in an equally short timeframe.

Small-angle neutron scattering

Schematic of common electrolytes (left) and ionic liquid detergent-like electrolytes (right) on an electrode surface. (Brown)

Using a technique called small-angle neutron scattering (SANS), Dr. Hazell’s role in the project was to identify the underlying structural features essential to the operation of the new electrolytes. He explained that the team’s research focused on finding novel storage mechanisms at IL-electrode interfaces.

“The team discovered that surface active ILs (SAILs), which contain amphiphilic structures inducing self-assembly, exhibit enhanced charge-storage performance at electrified surfaces,” Hazell said. “This newly reported phenomenon could bring the energy storage capability of a supercapacitor in line with lithium-ion battery technology. This is likely to have implications for the rapidly evolving automotive industry that is seeing a shift towards hybrid and fully electric vehicles.”

Hazell said it was possible that technology of this kind may be utilized within the next decade, particularly in hybrid vehicles where many rapid charge/discharge cycles are required: “A key aspect of this study is that the materials used are abundant. The molecular components can be found in a variety of household items including laxatives and soaps. This is an attractive prospect for car manufacturers as the technology is affordable and production scalable.”

He said the work demonstrated the power of scientific research “without borders” and added: “The groups from different nations were able to successfully combine their individual expertise to allow this fascinating discovery.” His contribution to the global effort was to identify the underlying structural features, which are essential to the operation of the new electrolytes using the SANS technique.

The SANS experiments were conducted at the Science and Technology Facilities Council (STFC) funded international facility Institute Laue Langevin (ILL), Grenoble, France. The paper is entitled: Self-assembled nanostructures in ionic liquids facilitate charge storage at electrified interfaces, by Xianwen Mao, Paul Brown, Ctirad Červinka, Gavin Hazell, Hua Li, Yinying Ren, Di Chen, Rob Atkin, Julian Eastoe, Isabelle Grillo, Agilio. AH Padua, Margarida F Costa Gomes and T Alan Hatton. It is dedicated to the memory of co-author Isabelle Grillo.