Ultrafine MOF as charge trap enables superior high-temperature energy storage performance in polyetherimide composites dielectrics

Polymer dielectrics are crucial for electrostatic energy storage and offer broad application prospects in advanced high-power electrical systems, but their energy storage performance declines considerably due to increased conductivity at elevated temperatures. This work presents a structurally-simple high-temperature composite dielectric by incorporating positively charged ultrafine UIO-66 nanoparticles into polyetherimide (PEI) matrix. Be distinguished from traditional sub-micron MOF structures that usually reported in very recently, the newly-found nanoscale effect endows the ultrafine UIO-66 (∼12.9 nm) with largely-increased active sites, surface charge density and electron affinity. These ultrafine UIO-66 nanoparticles can capture free charge through strong electrostatic interactions and introduce deeper traps in composite dielectrics, reducing conduction loss and improving energy storage property significantly at elevated temperatures. Specifically, filling only as tiny as 0.5 wt% ultrafine UIO-66 endows the PEI-based composite with ultra-high energy densities of 5.9J cm −3 and 3.7 J cm −3 accompanied by high charge–discharge efficiencies of 91.4 % and 84.1 % at 150 ℃ and 200 ℃, respectively. These obtained performance in this work surpasses those of most previously reported mono-layered composite counterparts. This study provides a straightforward and effective strategy for designing high-temperature polymer dielectrics in advanced electrical and electronic systems, offering a new route for future applications and developments.