Multilayer nanocomposites with ultralow loadings of nanofillers exhibiting superb capacitive energy storage performance

Extensive research has been carried out to enhance the capacitive energy storage capability of dielectric polymers through the design of multilayer polymer nanocomposites, which typically comprise a polarization layer with high-loading fillers (>10 vol%) and a breakdown strength (E-b) layer with relatively low filler loadings (<= 5 vol%). However, high filler loadings in the multilayer nanocomposites generally scarify the breakdown strength and mechanical properties and complicate film processing. It has been a tremendous challenge to balance polarization and breakdown strength in layered composites with low loadings of nanofillers. Herein, we present, for the first time, multilayered polymer nanocomposites with ultralow loadings of nanofillers, e.g., 0.2 vol% filler for high polarization and 2 vol% loadings for enhanced breakdown strength, to break the aforementioned tradeoff. The newly designed multilayer nanocomposites exhibit a markedly improved discharged energy density of 25.1 J cm(-3) along with an exceptional charging-discharging efficiency of 93.8%, which is by far the best comprehensive capacitive performance of a dielectric polymer nanocomposite reported to date. The impact of the architectures and compositions of the multilayer composite films on the dielectric properties and capacitive performance has been investigated. Finite element simulations are carried out to further understand the breakdown processes of the multilayer composite films with ultra-low loadings of the nanofillers. This contribution opens new opportunities for the development of scalable layered polymer composite dielectrics for high-energy-density capacitors.