Achieving high energy density at a low electric field of high-temperature sandwich-structured polymer dielectric composite by PVDF crystallinity regulation

Electrostatic energy storage dielectric polymers are essential for pulsed power applications due to their high power density. However, it suffers from low energy density and poor efficiency at high temperatures, which seriously hinders its application. Herein, a polyetherimide – MgO/polymethyl methacrylate/poly(vinylidene fluoride) – polyetherimide sandwich-structured composite was prepared by solution casting and hot-pressing. The experimental results show that MgO acted as a nuclear agent to promote the crystallization of PVDF, thereby improving the polarization at high temperatures. At 150 °C, the optimized composite exhibited a high discharge energy density of 3.34 J cm−3 when the charge–discharge efficiency was above 90% at 350 MV m−1. MgO alleviated both the ferroelectric loss and conduction loss at the low electric field as well, resulting in high polarization and high efficiency at the low electric field. Through this work, we made a new attempt to enhance the energy storage performance of high-temperature polymer-based dielectric composites under a low electric field.