Improved Working Temperature and Capacitive Energy Density of Biaxially Oriented Polypropylene Films with Alumina Coating Layers
Zhiwei Bao, Xinzhe Du, Song Ding, Jiahao Chen, Zhizhan Dai, Chuanchuan Liu, Yuchen Wang, Yuewei Yin, Xiaoguang Li
Abstract
High-temperature dielectric energy-storage properties are crucial for polymer-based capacitors for harsh environment applications. However, biaxially oriented polypropylene (BOPP), a state-of-the-art commercial capacitor dielectric, can work only below 105 °C. Here, we present a versatile method to enhance its working temperature by depositing alumina (Al2O3) layers onto BOPP films via magnetron sputtering. Compared with a pure BOPP film, the sandwiched Al2O3/BOPP/Al2O3 structure shows a higher dielectric constant, a lower electrical conduction loss, stronger mechanical properties, higher thermal conductivity, and especially increased working temperature. As a result, the composite film delivers a high discharged energy density of 0.45 J/cm3 under 200 MV/m (the actual operating electric field in hybrid electric vehicles) at 125 °C. The discharged energy density and energy-storage efficiency (∼97.7%) are highly stable over 5000 cycles at 125 °C. This work provides an effective route to develop high-temperature polymer-based capacitors.