(July 30, 2015) Using
a hybrid silica sol-gel material and self-assembled monolayers of a common
fatty acid, researchers have developed a new capacitor dielectric material that
provides an electrical energy storage capacity rivaling certain batteries, with
both a high energy density and high power density.
If the material can be scaled up from laboratory samples,
devices made from it could surpass traditional electrolytic capacitors for
applications in electromagnetic propulsion, electric vehicles and
defibrillators. Capacitors often complement batteries in these applications
because they can provide large amounts of current quickly.
The new material is composed of a silica sol-gel thin film
containing polar groups linked to the silicon atoms and a nanoscale
self-assembled monolayer of an octylphosphonic acid, which provides insulating
properties. The bilayer structure blocks the injection of electrons into the
sol-gel material, providing low leakage current, high breakdown strength and
high energy extraction efficiency.
“Sol-gels with organic groups are well known and fatty acids
such as phosphonic acids are well known,” noted Joseph Perry, a professor in
the School of Chemistry and Biochemistry at the Georgia Institute of
Technology. “But to the best of our knowledge, this is the first time these two
types of materials have been combined into high-density energy storage
devices.”