Superior energy storage of sandwiched PVDF films by separate introduction of core-shell Ag@BT nanoparticles and 2D MXene nanosheets

Polymer-based dielectrics exhibit promising applications in energy storage devices due to their enormous power density, good flexibility, and low cost. However, the low energy storage density remains to be the bottleneck. Here, sandwiched polymer-ceramic nanocomposite films are designed by stacking the PVDF middle layer incorporated Ag-decorated BaTiO₃ (BT) ceramic nanoparticles (Ag@BT NPs) and the PVDF top/bottom layers embedded 2D layered MXene nanosheets. Interestingly, the optimal performances with a reversible energy storage density (W_re) as high as ∼ 22.3 J/cm³ with an efficiency η ∼ 77% at a low electric field of 270 MV/m are achieved for the film with 5 wt% DA@Ag@BT/PVDF middle layer. Strong interfacial coupling, ionic interaction, and enhanced breakdown strength due to the Coulomb blocking effect in the hierarchical structures with different fillers are responsible for the high energy storage performance. Moreover, the phase-field simulation further proved an appropriate amount of DA@Ag@BT NPs can effectively prevent the formation of the conductive network, inhibit the dielectric loss and improve the breakdown strength. This hierarchical strategy demonstrates an applicable route for fabricating polymer nanocomposites with high performance.