Synergy of micro-/mesoscopic interfaces in multilayered polymer nanocomposites induces ultrahigh energy density for capacitive energy storage

High-energy-density dielectric materials are highly desirable for the miniaturization and integration of modern electronics and power modules for applications in electrical power, communication, medical and defense systems. However, the conventional polymer nanocomposites with nanofillers randomly dispersed exhibit a limited energy storage performance (e.g. discharged energy density <15 J/cm³ and efficiency <70%). Here, we demonstrate the multilayer structure as an effective route to polymer nanocomposites that concurrently have ultrahigh discharge energy density and high efficiency. Compared to the random-dispersed nanocomposites, the rationally designed multilayered polymer nanocomposites are capable of integrating the suppressed effects of dielectric/electrode and dielectric/dielectric interfaces on charge injection and migration to remarkably enhance the breakdown strength and are expected to deliver an unprecedentedly high energy density of ∼35.4 J/cm³ (an enhancement of ∼1100% over the bench-mark biaxially-oriented polypropylene). This work provides insight into the design and fabrication of polymer nanocomposite with high energy density and discharge efficiency for capacitive energy storage applications.