Improving high-temperature energy storage performance of PI dielectric capacitor films through boron nitride interlayer

As an important power storage device, the demand for capacitors for high-temperature applications has gradually increased in recent years. However, drastically degraded energy storage performance due to the critical conduction loss severely restricted the utility of dielectric polymers at high temperatures. Hence, we propose a facile preparation method to suppress the conductivity loss of polyimide (PI) films by inserting boron nitride interlayer. The experimental results and computational simulations indicate that consecutive boron nitride interlayer has better effect on suppressing leakage current density of the entire material compared with uniform dispersed boron nitride nanosheet (BNNS) composite films. The experimental results show that the leakage current density of PI films is reduced by an order of magnitude and a classy energy density of 2.58 J/cm3 at a charge–discharge efficiency of 90% has been achieved at 150 °C, far better than pristine PI (0.75 J/cm3 of energy density and 65% of efficiency under 275 kV/mm and at 150 °C). The method we reported in this work is applicable to a variety of polymer dielectric films produced by solution casting for elevated temperature energy storage application. Aiming at the main problem of drastically degraded of energy storage performance caused by the sharp increase of leakage current of polymer dielectric film at high temperature, the energy storage performance of PI at 150 °C is improved by embedding boron nitride intermediate layer in PI.