The figure above (Molecular Dynamics simulations by the group of Mathieu Salanne): shows ionic liquid surrounded by two porous carbon electrodes. It explains how the positive (red) and negative (green) ions interact with the carbon surface. The charging mechanism involves the exchange of ions between the bulk and the electrode. This simulation yields much higher capacitance values than in models using simplified regular electrode geometries. |
An
international team of materials researchers including Drexel
University’s Dr. Yury Gogotsi has given the engineering world a better
look at the inner functions of the electrodes of supercapacitors—the
low-cost, lightweight energy storage devices used in many electronics,
transportation and many other applications. In a piece published in the
March 4 edition of Nature Materials,
Gogotsi, and his collaborators from universities in France and England,
take another step toward finding a solution to the world’s demand for
sustainable energy sources.
Gogotsi,
a professor in Drexel’s College of Engineering and director of the A.J.
Drexel Nanotechnology Institute, teamed with Mathieu Salanne, Céline
Merlet and Benjamin Rotenberg from the Université Paris 06, Paul A.
Madden from Oxford University and Patrice Simon and Pierre-Louis Taberna
of Université Paul Sabatier. What the group has produced is the first
quantitative picture of the structure of ionic liquid absorbed inside
disordered microporous carbon electrodes in supercapacitors.
Supercapacitors have the capability of storing and delivering more power
than batteries; moreover, they can last for up to a million of
charge-discharge cycles. These characteristics are significant because
of the intermittent nature of renewable energy production.
According
to the researchers, the excellent performance of supercapacitors is due
to ion adsorption in porous carbon electrodes. The molecular mechanism
of ion behavior in pores smaller than 1 nm remains poorly understood.
The mechanism proposed in this research opens the door for the design of
materials with improved energy storage capabilities.
The
authors suggest that in order to build higher-performance materials,
researchers should know whether the increase in energy storage is due to
only a large surface area or if the pore size and geometry also play a
role. The results of this study provide guidance for development of
better electrical energy storage devices that will ultimately enable
wide utilization of renewable energy sources.
“This
breakthrough in understanding of energy storage mechanisms became
possible due to collaboration between research groups from four
universities in three countries,” Gogotsi said. “Moreover, the team used
carbon structure models developed by our colleagues Dr. Jeremy Palmer
and Dr. Keith Gubbins from the North Carolina State University. This is a
clear demonstration of the importance of collaboration between
scientists working in different disciplines and even in different
countries.”
On the molecular origin of supercapacitance in nanoporous carbon electrodes
