Enabling high energy storage performance in PVDF-based nanocomposites filled with high-entropy oxide nanofibers

Incorporating inorganic ceramic fillers in organic polymer matrix has been demonstrated as the major and effective strategy for excellent energy storage performance. Nevertheless, the excessive addition leads to the deterioration of breakdown strength and energy density, thus impedes the practical application. Herein, a completely new idea of preparing high-entropy oxide (Eu0.2Bi0·2Y0·2La0·2Cr0.2)2O3 (EBYLCO) nanofiber fillers is proposed and the EBYLCO-P(VDF-HFP)/PMMA nanocomposites are fabricated with an ultralow filling content. The enhanced entropy in the lattices results in the local polymorphic distortion and effectively increases the degree of the structural disorder. The random stress field and random electric field are remarkably enhanced. The pinning effect produced by the local polymorphic distortion restricts the movements of long polymer chains, which builds a stronger cross-linked network structure, reduces the loss under the strong electric field and further promotes the breakdown strength of the nanocomposites. Besides, the charge-shielding layers between polymer and nanofillers block the injection and transmission of space charges, which also contributes to high breakdown strength. Combining the enhanced breakdown strength of 509.4 kV mm−1 with the significantly increased polarization, the nanocomposite releases a maximum energy density of 15.13 J cm−3 and energy efficiency of 71%. This work is expected to provide a novel design paradigm for the nanofillers and further improves the energy storage capability for the dielectric capacitors.