Synergy of charge steric hindrance and micro-polarization regulation for enhancing high-temperature energy storage performance of polymer composite dielectrics

Abstract

Dielectric thin-film capacitors are core components of advanced electrical systems, but the degradation of their energy storage characteristics at high temperatures severely limits their applications. This paper innovatively proposes a method for synergistic control of charge trapping and micropolarization across a wide temperature range through a layer-by-layer assembly structure, and prepares a composite dielectric thin film with excellent high-temperature energy storage characteristics based on polyimide (PI). On the one hand, epoxy resin (DGEBA) acts as an organic assembly layer, and the interface phase formed by chemical bonding with PI transforms the trap energy levels, creating a charge trapping barrier to block breakdown paths, thus ensuring the maximization of material polarization. On the other hand, surface-modified strontium barium titanate (BST)@SiO₂ core–shell particles, as the inorganic assembly layer, form stable secondary amine bonds with epoxy molecules through amino groups, constructing a gradient dielectric hierarchical structure to achieve micropolarization control of local charges and improve the overall polarization capability of the material. In addition, the epoxy resin cured with 1-methylimidazole forms a rigid polyether network with high crosslinking density with PI, effectively ensuring the excellent energy storage performance of the material at high temperatures. Through the optimized regulation of the assembly layer count, a PI composite dielectric film (assembled with two layers) achieved a discharge energy density of 5.75 J cm⁻³ at 200 °C, while maintaining a discharge energy efficiency of no less than 80%. Its maximum discharge energy density reached 6.39 J cm⁻³ (with a discharge energy efficiency of 77.18%).