High-temperature energy storage properties of polyetherimide composites with tailored boron nitride quantum dots

Polymer film capacitors are currently being extensively investigated due to their advantages of outstanding power density and processability. However, the charge-discharge efficiency and energy density at high temperature for polymer dielectrics need to be further developed to fulfill the potential applications. In this study, sandwiched polyetherimide (PEI) composites with boron nitride quantum dots (BNQDs) have been prepared, in which BNQD/PEI composite as the outer layer prevents the diffusion of charge carriers with low conduction loss, and the relaxor P(VDF-TrFE-CFE) inner film serves as high electric displacement. The BNQDs are synthesized through the solvothermal reaction, and their inclusion enhances the dielectric constant and interfacial polarization of the composite. The presence of quantum dots restricts the hopping of charge carriers at high temperatures by increasing the activation of the energy barrier, which improves the dielectric reliability of PEI composites. Since the BNQD/PEI outer layer affords the majority of the electric field based on the principle of field strength distribution, large charge-discharge efficiency at high temperature is achieved in the optimal composite film. For example, an energy density of 9.9 J cm^-3with an efficiency of 90% at 450 MV m^-1is reached in 3 wt% multilayer film at 100 °C. The strategy of polymer multilayer film incorporated with tailored quantum dots offers an efficient approach for developing high-performance polymer dielectrics that withstand harsh electrical and thermal conditions.