Regulating Charge Transport in Polyetherimide via Small-Molecule Deep Traps for Efficient High-Temperature Energy Storage

All-organic dielectric polymers are promising high-temperature capacitive materials to enable energy storage applications in hybrid vehicles, deep oil, and gas extraction. However, semiconductor fillers with both a wide bandgap E g and a high electron affinity E a remain rarely reported. Here, we identify tetrabromo-1,4-benzoquinone (TBQ) as an alternative quinone-based small-molecule semiconductor, which exhibits a concurrently large E g of 3.24 eV and E a of 4.16 eV. We use TBQ to tune dielectric energy storage of benchmark polyetherimide (PEI). We find that the optimal TBQ doping level of 1.00 wt % yields the optimized dielectric energy storage properties. At 150 °C and 650 MV·m −1, the discharge energy density of PEI/TBQ reaches 6.6 J·cm −3 with a charge−discharge efficiency above 90%, which is superior to that of pristine PEI. These findings are expected to promote the development of all-organic dielectric polymers for high-temperature capacitive energy storage applications.