Interfacial Molecular Synergism: A New Pathway to Ultra-Efficient Energy Storage in Bilayer Polymer Dielectrics

Poly(vinylidene fluoride)-based (PVDF-based) ferroelectric polymers with the highest dielectric constant among known polymers represent the most promising class of dielectric materials for high energy density capacitor applications. However, their energy storage capacity has been consistently constrained by the high conduction loss and relatively low dielectric strength. Here, a novel interfacial molecular synergism strategy is proposed to enhance the energy storage performance of PVDF-based bilayer films, resulting in remarkable improvement in the Young's modulus and discharge energy storage efficiency (η). The significant enhancement is attributed to the formation of dense interfacial molecular entanglement between rigid polymers and the PVDF-based matrix via multi-site molecular synergism, which effectively alleviates interfacial mismatch and reduces conduction loss. Furthermore, the high polarity and large dipole moment of the cyano groups strengthen the molecular entanglement at the interface, further restricting charge migration and capturing charge carriers to suppress charge injection. Consequently, the bilayer film exhibits concomitantly the highest discharge energy density (U_d≈ 13.87 J cm⁻³) and a prominent η (η≈ 97.2%) along with an ultrahigh breakdown field strength (E_b≈ 767.1 MV m⁻¹). This work offers valuable insights into facilitating the industrial production of high-performance polymer dielectrics.