All-organic nanocomposite dielectrics contained with polymer dots for high-temperature capacitive energy storage

High-temperature polymer dielectrics with high energy density are urgently needed for capacitive energy storage fields. However, the huge conduction loss at elevated temperatures makes the capacitive performance of polymers degrade sharply, limiting the application of them. Herein, the polymer dots (PDs) with high-electron-affinity were introduced into high-temperature polymers to prepare all-organic nanocomposite dielectrics by solution casting. It is found that polymer dots capture injected electrons via strong electrostatic attraction and impede charges transport and accumulation inside composites, thus reducing leakage current density and improving high-temperature energy storage performance. Consequently, the high-temperature capacitance performance of nanocomposites was improved significantly and reached over 2.5 times that of the pristine polymers, e.g., the energy density of polyetherimide (PEI)/PD reached 3.24 J·cm⁻³ with excellent electrical fatigue reliability over 20,000 times. This work addresses the current problem of poor discharged energy density of polymer dielectrics at high temperatures with a simple and universal method.