Ultra-low dielectric loss and high thermal stability achieved by hierarchical microcapacitor structure in nanocomposites via surface topological modulation

The urgent need for miniaturized high-reliable electronic devices requires polymer film capacitors with stable dielectric properties under extreme environments. The traditional surface coating structure can barely boost the performance of energy storage dielectric materials , which are confronted with a high dielectric loss and low breakdown strength . Herein, reduced polyaniline (R-PANI) grows in the form of vertically oriented nanorods on the surface of porous carbon embedded with ultrafine BaTiO 3 , resulting in a hierarchical microcapacitor structure. The surface topology modulation of R-PANI dramatically increases the aspect ratio of the nanoparticles perpendicular to the external electric field, thus suppressing the leakage current and restraining the subsequent dielectric loss of the nanocomposite. The nanocomposite filled with 8 wt% C@BT@R-PANI exhibits a breakdown strength of 316.50 MV/m, a high dielectric constant of 66.8, and an ultra-low dielectric loss of 0.00663 at 1 kHz. Under a moderate electric field of 150 MV/m, the energy density increases to 2.75 J/cm 3 and the charge-discharge efficiency ( η ) reaches 80.09%. In addition, the nanocomposite exhibits an excellent dielectric-thermal stability in the range of 30–150 °C, making it a potential candidate for high-temperature dielectric materials.