Enhanced Energy Storage Performance Achieved in Multilayered PVDF–PMMA Nanocomposites Incorporated with High-Entropy Oxide Nanofibers

Large depletion of fossil fuels promotes the sustainable development of renewable energy. Polymer-based dielectric nanocomposites are widely utilized owing to their ultrafast charging–discharging rate and high power density in pulse power systems, smart grids, and other electrical devices. In this paper, completely new high-entropy oxide (Eu0.2Bi0.2Y0.2La0.2Cr0.2)2O3 (in short, E) nanofibers are fabricated, and the multilayered nanocomposites are prepared with electrospinning and layer-by-layer hot-pressing processes. A high energy density of 20.11 J cm–3 and an efficiency of 64% are achieved at 598.9 kV mm–1 in the trilayered nanocomposites. First, the enhanced entropy of the lattices leads to local polymorphic distortion, which, to a certain extent, limits the movements of long polymer chains, reduces the dielectric loss, and improves the breakdown strength of the nanocomposites. Moreover, for multilayered nanocomposites, the Schottky barrier forms with the direct contact between the electrodes and ferroelectric polymer. The difference in permittivity of the materials in contact with the electrodes leads to the difference in the barrier height around the interfaces, which results in a larger local electric field and a higher breakdown strength. Besides, the multilayered nanocomposites improve the rough interfaces between inorganics and organics and reduce the probability of dielectric breakdown. This work provides a new filling strategy and structural-layer design for the application of flexible dielectric materials.