Superior High-Temperature Energy Storage Performance of Poly(ether imide) Capacitive Films by Incorporating Core–Shell Structured BN@MgO Fillers
Tiandong Zhang, Ziqi Jin, Hua Li, Zhaotong Meng, Yue Zhang, Yongquan Zhang, Changhai Zhang, Qingguo Chi, Mengjia Feng
Abstract
Dielectric capacitors are widely used in electrical engineering due to their excellent insulation, high safety, and high power density. However, under high-temperature conditions, injected electric charges from metal electrodes, along with thermally generated charges, lead to a rapid increase in leakage current and severe degradation of insulation performance in polymer capacitive films, limiting long-term and stable operation. To address this issue, core–shell structured BN@MgO inorganic fillers were prepared using the magnetron sputtering method, with MgO as the core and BN as the shell. Results demonstrate that BN@MgO fillers significantly reduce conduction loss in poly(ether imide) (PEI) films by forming charge traps at interfacial regions between the fillers and the PEI matrix. The built-in electric field between BN and MgO efficiently captures mobile charges, enhancing the electrical insulation properties at elevated temperatures. Optimizing the doping content and BN shell thickness leads to a discharge energy density of 3.9 J/cm 3 at 150 °C, with a charge/discharge efficiency of 90% for PEI/ [email protected] (2.5h) composite films. Additionally, excellent cyclic reliability and performance are maintained after 50,000 charge/discharge cycles. The study presents an efficient method for constructing core–shell BN@MgO fillers and clarifies mechanisms for restricting charge mobility.