Interfacial polarization regulation of ultrathin 2D nanosheets inducing high energy storage density of polymer-based nanocomposite with opposite gradient architecture

High discharge energy density (Udis) has been achieved via regulating the interfacial polarization of ultra-thin 2D Sr2Nb2O7 nanosheets (SNO NSs) and constructing opposite gradient architecture. To further increase the dielectric constant (εr) of SNO NSs and therefore motivate high interfacial polarization, core-shell structured 2D nanosheets include Sr2Nb2O7@TiO2 NSs and Sr2Nb2O7@BaTiO3 NSs are successfully prepared and utilized as fillers in poly(vinylidene fluoride) (PVDF)/ polymethyl methacrylate (PMMA) blend polymer matrix (BPM). In addition, opposite gradient architecture, include high polarization layer (PL), high insulating layer (IL) filled with large size BN nanosheets (BN NSs) and middle transition layer, are constructed to depress the electric breakdown strength (Eb) degradation. As expected, the [email protected] NSs filled films with an optimal composition achieve excellent Udis of 32.51 J cm−3 with charge-discharge efficiency (η) of 0.64 near the Weibull Eb of 651.52 MV m−1. This Udis value is the most prominent in dielectric polymer nanocomposites under equivalent applied electrical field. The opposite gradient architecture can effectively depress the Eb degradation by preventing the electric trees evolution, which is confirmed by finite element simulations. This work provides a novel paradigm to fabricate high Udis energy storage polymer-based nanocomposites filled with 2D nanofillers.