Samples of the new hybrid sol-gel material are shown placed on a clear plastic substrate for testing.
Photo: John Toon
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.
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.
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 Georgia Tech. “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.”
The need for efficient, high-performance materials for electrical energy storage has been growing along with the demand for electrical energy in mobile applications. Dielectric materials can provide fast charge and discharge response, high energy storage, and power conditioning for defense, medical, and commercial applications. But it has been challenging to find a single dielectric material able to meet all of the material needs.
Hybrid sol-gel materials had shown potential for efficient dielectric energy storage because of their high orientational polarization under an electric field, so Perry’s research group decided to pursue these materials for the new capacitor applications.
The research, supported by the Office of Naval Research and the Air Force Office of Scientific Research, was reported in the journal Advanced Energy Materials.
— John Toon