Effects of Freeze-Quenching Process on Energy Storage Performance of PVDF Films

Polymer materials are considered ideal for high-energy-density film capacitors due to the light weight, flexibility, and high breakdown strength. Polyvinylidene fluoride (PVDF) is one of the most widely used polymers in energy storage applications due to its unique crystal structure and excellent polarization properties. This study systematically investigated the effects of freeze-quenching process on the crystal structure and energy storage performance of PVDF films. Various PVDF films were prepared at different heating temperatures (170, 180, 190 and 200 °C) and cooling temperatures (0, −15, −30 and −40 °C). This study demonstrates that thermal treatment at 180 °C yields the most pronounced enhancement in α-phase crystallinity of PVDF, while cryogenic treatment at −30 °C shows optical efficacy in promoting α-phase formation. This study identified that 180 °C thermal treatment produced the most significant enhancement in PVDF’s α-phase content, while −30 °C cold treatment produced the most significant enhancement in PVDF’s α-phase content. Notably, the PVDF film prepared under optimized processing conditions (heating temperature of 180 °C and cooling temperature of −30 °C) achieved an ultra-high energy storage density of 13.22 J/cm3 at an electric field strength of 519.74 kV/mm. This process has opened up a new path for the application of polymer film capacitors.