The simultaneously achieved high permittivity and low loss in tri-layer composites via introducing negative permittivity layer

Dielectric composites with excellent power densities have garnered significant attentions in electrical systems and pulsed energy storage. However, the low permittivity and high dielectric loss are greatly limit their applications. Herein, we present a novel approach involving tri-layer composites, where a middle negative-e ' layer is sandwiched between outer positive-e ' layers. This design aims to realize the balance of comprehensive performances by the interfacial polarization and synergistic effect between positive and negative-e ' layers. Amazingly, the composite with content 3-5-3 with the thickness ratio of 1:20:1 shows remarkable permittivity of 679 coupled with a low loss tangent of 0.017 @ 10 kHz, which is approximately 141 times higher than PI matrix with 4.8 of permittivity. Remarkably, the composite with content 3-5-3 (1:1:1) exhibited an improved Ud and high eta of 1.35 J/cm3 and 94.5 %, respectively. This work presents a new class of tri-layer composites with negative-e ' layer, whose design method is applicable in high-property dielectric composites.