Significant Energy Density of Discharge and Charge–Discharge Efficiency in Ag@BNN Nanofillers-Modified Heterogeneous Sandwich Structure Nanocomposites

The development of innovative dielectrics by considerably improving their energy densities of discharge is important for current electronic power systems. We present here newly designed heterogeneous sandwich structure nanocomposites (i.e., P(VDF-HFP)-xwt%Ag@BN nanosheets (Ag@BNN)/PEI-P(VDF-HFP)). The outer ferroelectric-type P(VDF-HFP) layers enhanced the dielectric displacement, while PEI reduced the losses due to its linear characteristic. Besides, the use of Ag@BNN as nanofillers improved the dielectric displacement, as well as breakdown strength. Consequently, the ideal sandwich structure achieved a significant energy density of 11.3 J/cm3 and decent charge–discharge efficiency of 80% at about 510 MV/m. This discharge energy density is the highest reported until now when charge–discharge efficiency of ≥80% is considered as the threshold. In-depth analysis revealed that comparatively higher Dmax – Dr (i.e., 4.7 μC/cm2), as well as the utmost breakdown strength (i.e., 510 MV/m), assisted in achieving this relatively higher discharge energy density. The finite element simulation demonstrated the efficacy of using Ag@BNN over BNN as nanofillers; i.e., it showed diverged electric field vectors near Ag nanoparticles, optimum electric field distribution between the sandwich structure layers, and improved dielectric displacement, in comparison with unmodified BNNs. The ideal sandwich structure also showed a short discharge time of 9.02 μs, a high power density of 0.165 MW/cm3, and an excellent lifetime until 40 000 cycles. This study shows that heterogeneous sandwich-structured nanocomposites with a surface decorated Ag@BNN nanofillers can be used in advanced dielectrics and pulsed power devices.