High Energy Density of Biaxially Oriented Polypropylene Film in Cryogenic Environment for Advanced Capacitor

In this paper, a method of significantly increasing the energy density of biaxially oriented polypropylene (BOPP) film by cryogenic environment has been proposed. The notable enhancements in the dielectric and energy storage performance can be attributed to precise microstructure manipulation, aimed at controlling charge injection limitations and optimizing molecular chain dynamics. The experimental results show that the maximum discharged energy density of BOPP film with thicknesses of 3.4 μm has reached 11.83 J/cm3 at -196 °C (2.9 times that at 25 °C) with a charge-discharge efficiency of 92.74%. The DC breakdown strength as high as 1120.4 kV/mm is obtained at -196 °C, exhibiting a substantial 63.7% augmentation compared to the measurement at 25 °C. Furthermore, reductions in conductance loss and capacitance loss (post self-healing testing) are realized. Mechanistic insights into the observed enhancements are investigated through computational simulations. This research provides a pivotal advancement and valuable perspective towards the development of film capacitors boasting the excellent energy storage characteristics.