Synergistic enhancement of high-temperature stability and energy-storage performance in polypropylene dielectric films via molecular trap engineering

Abstract

Polypropylene (PP)-based dielectric films suffer from low energy-storage density and poor thermal stability, limiting their application in advanced power electronics operating at elevated temperatures. Here, we propose a molecular-trap engineering strategy to simultaneously enhance the dielectric performance, thermal reliability, and processability of PP. A polar voltage-stabilizing molecule, 4-(allyloxy)-2-hydroxybenzophenone (AOHBP), is incorporated into the PP matrix via a scalable melt-blending process, forming deep charge traps in the amorphous regions that effectively suppress carrier migration and leakage current. Meanwhile, weak interactions between AOHBP and PP chains induce a “chain-pinning effect,” improving matrix rigidity and restricting segmental motion at high temperatures. The optimized PP/AOHBP-2 film achieves a breakdown strength of 802 MV m⁻¹ and an ultrahigh discharged energy density of 9.16 J cm⁻³ with an efficiency over 90% at 25 °C, while maintaining 5.33 J cm⁻³ and 88.3% efficiency at 120 °C. Enhanced cycling stability, power density, and self-healing capability are also realized. This work provides a scalable molecular design paradigm for high-performance PP-based dielectric films with exceptional energy-storage capability and thermal endurance for next-generation film capacitors.