Metallized stacked polymer film capacitors for high-temperature capacitive energy storage

Metallized film capacitors towards capacitive energy storage at elevated temperatures and electric field extremes call for high-temperature polymer dielectrics with high glass transition temperature (Tg), large bandgap (Eg), and concurrently excellent self-healing ability. However, traditional high-temperature polymers possess conjugate nature and high S value (C/(H + O) ratio), which compromises Eg and self-healing properties. Herein, we provide a series of novel molecules-fully alicyclic polymers based on commercial Kapton PI (Al-PIs), which exhibit intrinsic decoupling conjugate and decreasing S, leading to high Eg and robust self-healing. The Al-PIs possess much increased Eg of 5.23 eV (Tg of 242 °C) or Eg of 5.01 eV (Tg of 280 °C) with a lowered S < 0.7, which approaches Eg of 5.93 eV and S of 0.5 for the commercial benchmark biaxially oriented polypropylene (BOPP) applied at low temperatures (≤70 °C). Consequently, Al-PI delivers a record discharge energy density with 90 % discharge efficiency (Uη90) of up to 8.04 J/cm3 at 150 °C, 5.74 J/cm3 at 200 °C, and 3.12 J/cm3 at 250 °C, respectively. Besides, Al-PI is capable of self-healing even at 200 °C. We also demonstrate a stacked Al-PI metallized film capacitor with discharge energy density up to 1.6 J/cm3 and discharge efficiency of 98 % at 150 °C. These results confirm that alicyclic polymers are promising candidates for high-performance dielectric films and capacitors under extreme thermal and electric field conditions.