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

Ferroelectric/polymer based dielectric nanocomposites deliver high power density, but low discharged energy density (U_e) and charge–discharge efficiency (η), which are resulted from high remnant electrical displacement (D_r) 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 (D_max) and small D_r can substantially increase D_max-D_r 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 (E_b), which are confirmed by finite element simulations. Consequently, benefited from large D_max-D_r of 7.93 µC/cm² and E_b of 5281.68 kV/cm, PLZST@Al₂O₃/P(VDF-HFP) nanocomposites with 3 wt% filler contents exhibit simultaneously a large U_e 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.