Entropy‐Driven Conformational Disorder Enables Outstanding High‐Temperature Energy Storage in Dielectric Polymers

Abstract

ABSTRACT The pursuit of high‐temperature polymer dielectrics is consistently hindered by the intrinsic tradeoff between ensuring robust electrical insulation and maintaining thermal stability. While aromatic polyimide (PI) has superior thermal resistance, its dense π–π stacking facilitates the formation of charge transfer complexes, causing significant leakage and capacitive failure at elevated temperatures. In this study, we developed an entropy‐driven conformational disorder strategy to maximize the conformational entropy of our designed ternary random copolymerized PI (R‐PI, Δ S conf = 5.76 J/(mol·K)). The π‐conjugation decoupling and electron localization of the R‐PI were achieved by dynamic conformational flipping. Density functional theory and molecular dynamics calculations indicate that the structural randomized state generates a highly fluctuating electrostatic potential field. This field creates high‐density deep energy traps that effectively suppress the long‐range hopping transport of charge carriers. As a result, the optimal R‐PI‐0.5 delivers a discharged energy density of 6.12 J/cm 3 ( η = 91.1%) under an applied field of 650 MV/m at 200°C. This molecular‐level design paradigm leverages conformational entropy to exceed traditional dielectric limits, offering a robust pathway for next‐generation harsh‐environment energy storage.