Improved high-temperature energy storage of polyetherimide by energy level structure regulation

Polyetherimide (PEI) for high-temperature energy storage still face the critical problem of low discharged energy density. The dramatic increase in leakage current is the basic reason for the deterioration of energy storage characteristics under elevated temperatures. Herein, a molecular engineering strategy is presented to suppress electrical conduction by introducing a high electron-affinity dianhydride structure into the main chain of PEI. The energy band structure of PEI is markedly affected by the dianhydride, which is illustrated by experimental research and density functional theory (DFT) calculations. Structures with high electron-affinity act as trap centers to capture carriers, significantly inhibiting conduction at elevated temperatures. Consequently, the PEI hybrid film exhibits a discharged energy density of 4.01 J/cm3 and a charge-discharge efficiency of 91% at 150 °C. The high throughput and easy processing of the PEI hybrid film makes it a potential choice for energy storage under harsh conditions. This work represents a route for preparing polymer dielectrics with outstanding energy storage characteristics capable of operating in high temperature environments.