Scalable all-organic polymer dielectrics for high-temperature film capacitors with construction of deep-trap level and cross-linking network

Abstract

Polymer dielectrics are key component for energy storage capacitors in modern electronical equipment with their high breakdown strength, great reliability and processable for large-scale manufacture. However, deteriorated capacitive performance due to dramatically increased conductive loss at elevated temperature fails polymer dielectrics to meet the rising demand for harsh working environment. Herein, a novel thermosetting polymer benzoxazines (BZ) is selected, and a serial of polyetherimide (PEI)/benzoxazines (BZ) dielectric films designed with rich traps are prepared for high temperature capacitive application. The density functional theory (DFT) simulations have revealed that energy barrier can be formed based on the difference in energy band structure of BZ and PEI. Constructed concurrently with dense cross-linking network formed by the polymerization of benzoxazines monomers, PEI/BZ composites can exhibits great capability in restraining the charge transport, suppressing the leakage current density, therefore endowing a significant improvement in energy storage density at elevated temperature. At 150 °C, the PEI/5 wt% BZ composite processes energy storage density (U_e) as high as 4.64 J cm⁻³ with charge–discharge efficiency of 92 % at 550 MV m⁻¹, representing a 2.3-fold increase compared to pure PEI, and capacitive reliability of 50,000 cycles at 400 MV m⁻¹. Notably, integrated with the controllability of BZ monomer, straightforward film fabrication and the over-all low cost, this design strategy have shed a bright light in the industrial manufacture of high-temperature capacitive materials with superior energy storage performance.