Superior High‐Temperature Energy Storage Performance in All‐Organic Composite Dielectrics Achieved by Synergistic Regulation of Free Volume and Charge Distribution

Abstract Developing polymer dielectrics with stable high‐temperature energy storage performance remains a pivotal challenge for next‐generation electrical systems. However, the exponentially increasing conduction loss at elevated temperatures results in a decline in both energy storage density and efficiency. Herein, a cross‐scale synergistic regulation strategy that integrates mesoscale free volume and molecular‐scale charge trap, effectively addressing the issue of free volume collapse and space charge accumulation under thermal‐electric coupling stress is proposed. By blending polyimide with polyetherimide and introducing a low‐cost n‐type organic semiconductor, 1,4,5,8‐naphthalenetetracarboxylic dianhydride, the resulting single‐layer composite achieved a discharge energy density ( U _d ) of 5.01 J cm ⁻³ with a charge–discharge efficiency ( η ) close to 90% under 500 MV m ⁻¹ at 150 °C. Additionally, multi‐layer gradient architecture is employed to further enhance the high‐temperature energy storage properties of the composites. Ultimately, the resultant 0.5‐2.0‐0.5 three‐layer composite demonstrates a U _d of 6.95 J cm ⁻³ at 150 °C with a η of 84.5%. Even under 200 °C, 0.5‐2.0‐0.5 delivers a U _d of 3.24 J cm ⁻³ with a η of 90.1%. This research presents a novel strategy for enhancing the energy storage performance of all‐organic polymer dielectrics under high‐temperature conditions.