Physical crosslinking optimized high-temperature capacitive energy storage of polyetherimide nanocomposites with ultralow C60 particles

The extreme operating environments of film capacitors have created an urgent need for a new generation of polymer dielectric materials. Polymer-based composites are a more efficient option in terms of outstanding performance and large-scale industrialized production. Herein, C₆₀ is selected as a functional filler to be combined with commercial polyetherimide (PEI) through electrostatic interactions to construct polymer nanocomposites (C₆₀/PEI). Ultralow-filled C₆₀/PEI nanocomposites achieve the comprehensive improvement of electrical, thermal and mechanical performance due to the physical cross-linking points acted by C₆₀ particles. C₆₀ shows a strong ability to inhibit electron transfer due to the unique zero-dimensional cage structure and high electron affinity, which reduces the conduction loss at high temperatures. Theoretical and experimental results show that the introduction of trace amounts of C₆₀ particles into PEIs constructs stable carrier traps and significantly improves the high-temperature energy storage characteristics. The dielectric permittivity and breakdown strength are increased from 3.24 to 447 MV/m for PEI to 3.45 and 520 MV/m for the optimal C₆₀/PEI nanocomposite at 150 °C, respectively. Consequently, the optimal C₆₀/PEI nanocomposite achieves a discharged energy density (U_d) of 3.69 J/cm³ at 150 °C, which is higher than 2.65 J/cm³ of PEI. This provides a convenient and effective strategy to synergistically improve the comprehensive performance of polymer nanocomposite films for high-temperature energy storage applications.