Remarkable High‐Temperature Energy Storage in Co‐Polymerized Polyetherimide Via Constructing Hybrid Electrostatic Potential Barriers

Abstract High‐temperature dielectric polymers are increasingly attracting significant interest for energy storage applications in harsh environments. However, the exponentially increased conduction losses under high temperatures and elevated electric fields often cause serious degradation of the capacitive performance of dielectrics. Unlike most reported energy‐level tuning strategies, this study introduces a novel approach that constructs localized electrostatic barriers to enhance the high‐temperature energy storage of polyetherimide (PEI) films. By copolymerizing amide groups MPD (1,3‐Phenylenediamine) and PAB (4,4′‐Diaminobenzanilide) into the PEI backbone, the strong electrostatic separation effect of amide dipoles is established, leading to a significant electric potentials difference. Density Functional Theory (DFT) proves that intermolecular local potential fluctuations generate significant hybrid electrostatic barriers (4.2 eV) to trap carriers and suppress their migration within the spatial freedom domain. Consequently, the largely suppressed leakage current and enhanced breakdown strength are yielded in co‐10PAB/90MPD polymer, creating a high energy density of 4.3 J cm⁻³ (η > 90%) at 200 °C as comparison to the original PEI‐MPD (2.1 J cm⁻³), which surpasses most high‐temperature energy storage polymers. This work demonstrates a promising paradigm of dipolar regulation at the molecular level for high‐temperature dielectrics.