Low-entropy amorphous dielectric polymers for high-temperature capacitive energy storage†

Abstract

Electrostatic capacitors based on polymer dielectrics are essential components in advanced electronic and electrical power systems. An urgent challenge, however, is how to improve their capacitive performance at high temperatures to meet the rising demand for electricity in a harsh-environment present in the emergent applications such as electric vehicles, renewable energy, and aerospace systems. Here, we report a low-entropy amorphous polymer with locally extended chain conformation comprising high-T_g poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) blended with polystyrene (PS) that exhibits an energy density as high as 5.5 J cm⁻³ with an efficiency of >90% at an electric field of 600 MV m⁻¹ at 150 °C, outperforming the existing dielectric polymers. Our results reveal that regulating the conformation entropy of polymer chains introduces a favorable locally extended polymer chain conformation, resulting in dense chain packing with short-range ordered but long-range disordered microstructures, and inhibits the transport of electrons in dielectric polymers, consequently, leading to the substantial improvements of capacitive performance at elevated temperatures. This low-entropy approach is scalable, general, ultra-low-cost and simple, paving the way for mass fabrication of high-performance and high-quality polymer films required for high-temperature film capacitors.