Side-Chain-Type Polyimide-Cu Complexes with Suppressed Activation Energy of Relaxation for Advanced High-Temperature Capacitor

Abstract

The burgeoning growth of the new energy vehicles and aviation industry has escalated the need for energy storage capacitors capable of stable operation in harsh environments. The advent of metal-polyimide complexes has illuminated a novel approach for preparing temperature-resistant capacitors. However, the general application of these metal-polyimide complexes is impeded by the high dielectric loss and low breakdown strength, consequences of main-chain coordination and excessive metal ions content. Herein, our study proposes a novel polyimide-Cu complex material (POP-Cu) predicated on side-chain-type pyridine-Cu coordination, utilizing the structural backbone PMDA-ODA of mature commercial PI (Kapton) with reliable performance. Owing to the high degree of freedom afforded by the side chain with suppressed relaxation activation energy and the long-range electron delocalization formed by d-π coordination, the dielectric constant of this material containing merely 2.7 mol% Cu increases from 3.25 (POPI) to 5.58, while maintaining a remarkably low dielectric loss of 0.0066. Meanwhile, this material exhibits a substantial DC breakdown strength of 436.2 MV·m⁻¹ and a high energy density of 5.42 J·cm⁻³, coupled with superior mechanical and thermal properties. Even at 150 °C, it retains over 90% of its room-temperature energy density, demonstrating notable dielectric stability under high temperatures. These attributes underscore its promising application for capacitors operating in harsh environments.