Texas State researchers develop process for energy-storing ‘supercapacitors’

News Reporter

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William Stapleton, assistant professor at the Ingram School of Engineering, leads a research team at Texas State in the development of a “supercapacitor” capable of storing greater amounts of energy in smaller packages.

Texas State researchers have developed a process to create high-heat tolerant, energy storing “supercapacitors” from a raw material that will help green energy initiatives in the future.

The capacitors store an electrical charge that can be rapidly transferred to electronic devices. “Supercapacitors” function like capacitors but can store a greater charge in a smaller package.

The raw material, calcium-copper-titanate, or CCTO, was recognized as a possible supercapacitor material in 2000 and has since been studied worldwide. According to Raghvendra Pandey, electrical engineering professor, he and William Stapleton, assistant professor of electrical engineering, have been studying CCTO for several years.

“What we’ve done is worked on refining the process of manufacturing to maximize the ability of CCTO to service as a capacitor,” Stapleton said.

Supercapacitors that offer efficient, high-speed energy with a large amount of storage are important in many fields, Stapleton said. Green energy and electric vehicles could profit instantly from the CCTO material, he said.
CCTO is made into a ceramic material by using heat, pressure and time so that it has the best possible properties as a capacitor, Stapleton said.

“This material has a lot of potential and I think we can continue to refine what we can do with it,” Stapleton said.
The group of researchers, led by Pandey, found the efficiency of a CCTO supercapacitor depends on the relationship between two properties of the material known as permittivity and loss tangent.

Permittivity is the quality of the capacitor material that allows it to store energy. Higher permittivity values characterize a superior capacitor, Pandey said.

The loss tangent, or loss factor of energy, is determined by how much goes into and out of the capacitor, Stapelton said.

“It tends to be, for any material, that the more energy you’re storing, the higher the loss factor is,” Stapleton said.
The problem has been finding ways to raise the amount of energy stored in the capacitor while reducing the loss of energy, Stapleton said.

When the loss of energy is high, the capacitor cannot hold a saved charge for more than a few seconds, Pandey said.

Efforts to hold the high permittivity while reducing the loss of energy would fail in CCTO unless the material is processed in the ceramic way, Stapleton said.

Ceramic material is ideal for harsh environments because it is durable and capable of handling high temperatures, Stapleton said. The current form of capacitors cannot handle that sort of temperature range, while the CCTO based materials can withstand up to about 700 degrees centigrade, Stapleton said.

The research was done under a contract from US Ferroics LLC, the company that was the main contractor for the project, funded by the Air Force Office of Scientific Research, Pandey said.

Neither the company nor the Air Force showed any interest in protecting the invention by filing for a patent, so there are no plans to commercialize the work, Pandey said.