Cost-effective strategy for high-temperature energy storage performance of polyimide nanocomposite films

The performance of most polymer-based film capacitors deteriorates severely at high temperatures, while high T_g polymer capacitors, despite their good performance at high temperatures, but their performance still decays severely after prolonged operation at high temperature. This study involves the deposition of a wide bandgap SiO₂ inorganic layer on both surfaces of polyimide (PI) films using electron beam thermal evaporation. The findings indicate a substantial enhancement in the breakdown field strength and energy storage density of the composite films at elevated temperature following the deposition of the SiO₂ inorganic layer. Specifically, a 100-nm-thick inorganic layer resulted in a breakdown field strength of 459.65 MV m⁻¹ and an energy storage density of 3.2 J cm⁻³ at 150 °C. Subsequently, the polyimide film coated with a 100 nm SiO₂ inorganic layer was infused with small quantities of SrTiO₃ nanoparticles, leading to a breakdown field strength of 504.08 MV m⁻¹ and an energy storage density of 6.75 J cm⁻³ and maintained an efficiency of 90.9 %. These results surpass the performance of the majority of high-temperature polymer films reported to date, with the inorganic layer deposited via electron beam thermal evaporation matching that of the costly magnetron sputtering method. The study presents a cost-effective method suitable for large-scale industrial production, significantly enhancing the electrical performance of PI at elevated temperatures and offering an economical solution for the commercialization of poly composite-based high-temperature capacitors.