Enhanced Energy Storage Properties of Four-Layer Composite Films via Strategic Macrointerface Modulation

Dielectric capacitors play a crucial role in the field of energy storage; however, the low discharged energy density (<i>U</i>_e) of existing commercial dielectrics limits their future applications. Currently, further improvement in the <i>U</i>_e of dielectrics is constrained by the challenge of simultaneously achieving high permittivity (ε_r) and high breakdown electric field strength (<i>E</i>_b). To address this issue, we designed a series of four-layer poly(vinylidene fluoride) (PVDF)-based composite films comprising three functional layers: a sodium bismuth titanate (NBT) plus PVDF composite (NBT&PVDF) layer to achieve high ε_r values and a pure PVDF layer and a boron nitride (BN) plus PVDF composite (BN&PVDF) layer to achieve high <i>E</i>_b values. This design synergistically enhanced the ε_r and <i>E</i>_b values of the composite films by exploiting low-loss macrointerface polarization via adjustment of the functional layer stacking order, as supported by simulation analyses. Ultimately, the composite film with a topmost layer of pure PVDF, followed by an NBT&PVDF layer, another pure PVDF layer, and a BN&PVDF layer achieved an enhanced <i>U</i>_e value of 26.42 J·cm^-3 and excellent efficiency of 80.03% at an ultrahigh <i>E</i>_b value of 770 MV·m^-1. This approach offers an innovative pathway for developing advanced energy storage composite dielectrics via macrointerface manipulation.