Multilayered ferroelectric polymer films incorporating low-dielectric-constant components for concurrent enhancement of energy density and charge–discharge efficiency

Ferroelectric polymers are the materials of choice for capacitive energy storage owing to their highest dielectric constants (K) and the best energy densities among the current dielectric polymers. Herein, different from the conventional approaches based on the incorporation of high-K fillers into the single-layer films to enhance the capacitive performance, a low-K polymer, i.e. PMMA with a K value of 3–4, is selected as an example and introduced into the layered configurations of the ferroelectric polymer. Both improvements in the energy density (U_e) and charge–discharge efficiency (η) over those of the pristine polymer have been achieved via the establishment of multiple interlaminar interfaces and modulation of component ratios. The influence of film configuration on the capacitive performance has been systematically studied. The trilayered all-polymer film with optimized component ratio is capable of operating with a charge–discharge efficiency as high as 84% and concurrently delivering an energy density up to 20.3 J cm⁻³, surpassing the capacitive performance of the currently available polymer dielectrics that present the upper limits of U_e of ~20 J cm⁻³ and η of ~80%. Along with excellent stability of dielectric and mechanical properties of the polymer films, this work suggests great potential of the multicomponent ferroelectric polymers with layered architecture for electrical energy storage applications.