Enhanced energy storage performance of polyetherimide-based sandwich-structured dielectric films in elevated temperature range via using cyanoethyl cellulose layer

In order to satisfy the application of electronic device in the harsh environment, polymer-based dielectrics should have high discharge energy density (Ud) and high-temperature resistance synchronously. Herein, a series of sandwich-structured polymer films consisting of cyanoethyl cellulose (CEC) and polyetherimide (PEI) were fabricated by the solution casting method. The PEI-based sandwich-structured dielectric films showed high dielectric constant because of highly polarized CEC layer and the macroscopical interfacial polarization. In addition, the polymer films displayed the improved breakdown strength owning to the insulating PEI, barrier effect of the interface, and electric field redistribution. As a result, the maximal Ud of a positive sandwich-structured P–5C–P film with outer PEI layer and central CEC layer reached 6.8 J/cm3 (151% of pure PEI) along with charge-discharge efficiency of 80%. More importantly, at 100 °C and 150 °C, a high Ud of 5.5 J/cm3 and 3.0 J/cm3 were achieved in the P–5C–P film due to both high glass transition temperature (Tg) of PEI and CEC, which was 1.72 times and 1.36 times than that of pristine PEI, respectively. This work provides a new method for the preparation of high-performance sandwich-structured polymer dielectrics via selecting highly polarized central polymer layer with high Tg.