Reducing conduction losses in high energy density polymer using nanocomposites

For energy storage applications, it is critical that the dielectric material possesses low losses, especially the conduction losses, which could become significant at high temperatures and high electric fields. We investigate the conduction at fields up to 100 MV/m and high temperatures in a semi-crystalline poly(tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) terpolymer which has been shown to be attractive for high energy density capacitors. Experimental results show that the insulating nanofillers are very effective in reducing the conduction current, i.e., a more than two orders of magnitude reduction in conduction can be achieved with less than 1 wt.% (< 0.5 vol. %) of Al2O3 nanofillers. Experimental measurements are compared with multiscale simulations, which shows that the dominant conduction mechanism, i.e., carrier hopping in the polymer, is markedly reduced owing to a large decrease in the mobile carrier concentrations and increased trap depth, caused by the nanofillers.