High-temperature polymer dielectric films with excellent energy storage performance utilizing inorganic outerlayers

The optimization of high-temperature polymer capacitors is critical to the development of power electronics in harsh environments. The conduction loss of polymers increases dramatically at high temperatures, leading to a decrease in energy density and charge/discharge efficiency, which is a major impediment for capacitor applications. In this work, polyetherimide (PEI) composite films with trilayer structures are designed, in which the boron nitride nanosheet (BNNS) outer layers are optimized for charge blocking effect at multiple interfaces. The modulation of the inorganic layers not only increases the barrier height for charge injection from the electrodes, but also creates a PEI layer/BNNS layer interface that facilitates the formation of traps, thus effectively suppressing further carrier transport. Experiment and simulation verify that the construction of the trilayer structure promotes electric field redistribution, which significantly enhances high-temperature energy storage performance. At 200 °C, the energy density of the trilayer composite film is 3.81 J cm−3 with a charge/discharge efficiency >90 %, which is 766 % higher than PEI film (0.44 J cm−3 with a charge/discharge efficiency >90 %). Notably, the energy storage performance of trilayer composite film at high temperature is far superior to the reported high-temperature polymer dielectric films. This work demonstrates the promising potential of multilayer structures applied to dielectric polymer composite films at high temperatures.