Enhanced energy storage performance of bilayer composite films with Na0.5Bi0.5TiO3 platelets

Polymer-based dielectric composites with enhanced energy storage performances occupy a pivotal position in the modern power electronics industry. Unfortunately, these dielectric composite materials still exist unsolvable problems, especially the deficient breakdown strength (Eb) and heat amassment caused by dielectric loss. Herein, the novel bilayer composite films comprised of pristine poly(vinylidene fluoride) (PVDF) as the top layer and Na0.5Bi0.5TiO3 (NBT)/PVDF composite doped with two-dimensional (2D) NBT platelets as the bottom layer were designed and prepared. Subsequently, the dielectric and energy storage properties of these bilayer structure composite films were analyzed. The results demonstrate that this bilayer structure with optimized NBT content increases the dielectric constant, enhances the Eb, and reduces the dielectric loss, thus notably improving discharged efficiency (I) and discharged energy density (Ue). Eventually, an ultrahigh I of 80.3% and a superior Ue of 22.6 J cm-3 are gained at 650 MV m-1 with the composite layer involving 5 vol% 2D NBT platelets. Therefore, this new strategy of simultaneously increasing the Ue and I of the composite film will provide new thoughts for the exploitation of high-performance capacitors.