Energy density and efficiency of scalable polymer nanocomposites utilizing core-shell PLZST@Al2O3 antiferroelectric fillers with dielectric gradient

•P(VDF-HFP) composite with core–shell structured PLZST@Al2O3 AFE filler is obtained.•AFE fillers with core–shell promote concomitant enhancement of the Dmax and Eb.•An ultra-high Ue of 17.95 J/cm3 and large η of 75% are obtained in nanocomposites.•Finite element simulation indicates Al2O3 increases electric tree evolving branch. Ferroelectric/polymer based dielectric nanocomposites deliver high power density, but low discharged energy density (Ue) and charge–discharge efficiency (η), which are resulted from high remnant electrical displacement (Dr) of ferroelectric fillers and large dielectric difference between ferroelectrics and polymers, constrain their use in integrated electronic equipments. Here, we provide an effective and low-cost strategy for developing high-energy–density and high-efficiency dielectric nanocomposites by incorporating core–shell structured PLZST@Al2O3 nanoparticles (NPs) as fillers into P(VDF-HFP) polymer matrix. The introduction of PLZST antiferroelectric (AFE) cores with large maximum electrical displacement (Dmax) and small Dr can substantially increase Dmax-Dr values and narrow D-E loops of dielectric nanocomposites. The addition of Al2O3 shells with wide band gap and dielectric constant near that of the P(VDF-HFP) matrix can prevent the charge injection from electrodes and cause the applied electric field evenly distribute, and thus inhibit the leakage current and increase the breakdown strength (Eb), which are confirmed by finite element simulations. Consequently, benefited from large Dmax-Dr of 7.93 µC/cm2 and Eb of 5281.68 kV/cm, PLZST@Al2O3/P(VDF-HFP) nanocomposites with 3 wt% filler contents exhibit simultaneously a large Ue of 17.95 J/cm3 and high η of 75%, which outperform those of all latest NPs/polymer nanocomposites in terms of overall capacitive performances and are even higher than those achieved in polymer nanocomposites loaded with nanowires or nanofibers fabricated by complicated methods. This study exhibits a promising way to promote the industrialized fabrication of dielectric capacitors through capitalizing on the synergy of the dielectric constant gradient, wide band gap and AFE characteristics of the fillers.