North Carolina State University physicists have found a way to improve high-energy-density capacitors so that they can store up to seven times as much energy per unit volume as the traditional capacitor structures. High-performance capacitors would bring to hybrid and electric cars much greater acceleration, to rockets and spacecraft, faster steering, and improved lasers — among many other electrical applications.

The amount of energy that a capacitor can store depends on the dielectric material between the metal surfaces. A polymer called PVDF has interested physicists as a possible high-performance dielectric. It exists in two forms, polarized and unpolarized. In both cases, its structure is mostly frozen-in and changes only slightly when a capacitor is charged up. Mixing a second polymer called CTFE with PVDF results in a material with regions that can change their structure, enabling a capacitor employing this mixture to store and release unprecedented amounts of energy.

The team, led by Vivek Ranjan, concluded that a more ordered arrangement of the material inside the capacitor could further increase the energy storage of new high-performance capacitors, which already store energy four times more densely than capacitors used in industry. The predictions of higher energy density capacitors have yet to be experimentally tested.