Energy storage density and efficiency of polyetherimide nanocomposites diminished by the temperature dependent charge hopping

The utilization of renewable energies requires extensive use of energy storage equipment such as dielectric capacitor. Polyetherimide nanocomposites (PEI PNCs) have high energy storage performance, and become the next generation advanced dielectrics However, the quantitative relation between the charge transport and energy storage of PEI PNCs is not very clear, restricting further improvement of their performance. Considering the charge injection from electrodes and the charge hopping transport inside the dielectric, the energy storage and release model of capacitors was established. Firstly, the conductivities of PEI PNCs were simulated, and the charge transport parameters were determined by comparing with the experiments. Then, the electric displacement-electric field (D-E) loops of PEI PNCs were simulated, and the discharged energy density and energy efficiency were calculated from them. The simulation results are consistent with the experiments, and the quantitative relationship between charge injection and transport parameters and energy storage performance is established. In addition, it is found that the energy storage density and efficiency are diminished by the increase of hopping distance at high temperatures. Increasing the hopping barrier, reducing the hopping distance and its temperature dependence through nano-doping can significantly improve the energy storage performance under high temperatures and high electric fields.