Improved breakdown strength and energy density of polyimide composites by interface engineering between BN and BaTiO3 fibers

Conventionally, interface effects between polymers and fillers are essential for determining the breakdown strength and energy storage density of polymer-based dielectric composites. In this study, we found that interface effects between different fillers have similar behavior. BN and BaTiO 3 fiber composite fillers with three different interface bonding strengths were successfully achieved by controlling composite processes (BT-fiber/BN < BT-fiber@BN < BT-fiber&BN), and introduced into a polyimide (PI) matrix to form composite films . Considerably enhanced breakdown strength and energy storage density were obtained in BT-fiber&BN/PI composites owing to strong interface bonding, compared to other two composite fillers, which are well supported by the data from the finite element simulation. Specifically, PI composites with only 3 wt% BT-fiber&BN possess an optimized energy storage density of approximately 4.25 J/cm 3 at 4343 kV/cm. These results provide an effective way for adjusting and improving the energy storage properties of polymer-based composites.