Hierarchical self-assembled interfaces in organic-inorganic nanoparticle/PEI composites: A strategy for enhanced high-temperature energy storage performance

Polymer dielectrics are widely used due to their ultra-high breakdown strength and low dielectric loss. However, mitigating the significant reduction in breakdown strength and energy storage efficiency caused by increased conductive loss at high temperatures remains a major challenge. In this study, a ternary composite dielectric is synthesized via the introduction of nano core-shell fillers SiC@SiO₂ and ferroelectric polymer P(VDF-HFP) into polyetherimide (PEI). This compositional design not only enable P(VDF-HFP) to form an "island-like" phase separation structure but also facilitate the spontaneous segregation of SiC@SiO₂ in P(VDF-HFP) phase. Consequently, self-assembled hierarchical SiC@SiO₂/P(VDF-HFP)/PEI interfaces are constructed in PEI matrix. Experimental results demonstrate that this dielectric maintains a low leakage current density over a wide temperature range, from room temperature to 150 °C. The introduction of two fillers creates more charge traps at the self-assembled hierarchical interface, effectively inhibiting the conductive loss mechanism. Finally, under 150 °C and 750 MV/m, the optimized dielectric achieves a discharge energy density of 10.10 J/cm³, an ultra-high energy storage efficiency (96.7%), and an excellent figure of merit (∼306.06). This work provides certain theoretical support for the construction of hierarchical interfacial modulation of carrier transport and the optimization of high-temperature polymer-based energy storage.