Polyphenylene Oxide Film Sandwiched between SiO<sub>2</sub> Layers for High-Temperature Dielectric Energy Storage
Zhizhan Dai, Jiangheng Jia, Song Ding, Yiwei Wang, Xiang‐Sen Meng, Zhiwei Bao, Shu‐Hong Yu, Shengchun Shen, Yuewei Yin, Xiaoguang Li
Abstract
The commercial capacitor using dielectric biaxially oriented polypropylene (BOPP) can work effectively only at low temperatures (less than 105 °C). Polyphenylene oxide (PPO), with better heat resistance and a higher dielectric constant, is promising for capacitors operating at elevated temperatures, but its charge–discharge efficiency (η) degrades greatly under high fields at 125 °C. Here, SiO 2 layers are magnetron sputtered on both sides of the PPO film, forming a composite material of SiO 2 /PPO/SiO 2 . Due to the wide bandgap and high Young’s modulus of SiO 2, the breakdown strength ( E b ) of this composite material reaches 552 MV/m at 125 °C (PPO: 534 MV/m), and the discharged energy density ( U e ) under E b improves to 3.5 J/cm 3 (PPO: 2.5 J/cm 3 ), with a significantly enhanced η of 89% (PPO: 70%). Furthermore, SiO 2 /PPO/SiO 2 can discharge a U e of 0.45 J/cm 3 with an η of 97% at 125 °C under 200 MV/m (working condition in hybrid electric vehicles) for 20,000 cycles, and this value is higher than the energy density (∼0.39 J/cm 3 under 200 MV/m) of BOPP at room temperature. Interestingly, the metalized SiO 2 /PPO/SiO 2 film exhibits valuable self-healing behavior. These results make PPO-based dielectrics promising for high-temperature capacitor applications.