Semi-Alicyclic Dipolar Glass Dielectric Polymer Capacitors for Superior High-Temperature Capacitive Energy Storage

Ultrahigh-power-density metallized film capacitors at elevated temperatures and electric field extremes are key components in electrical and electronic systems. The miniaturization, integration, and cost-effectiveness of the systems demand high-energy-density, high-efficiency, and reliable dielectrics. A major challenge is to concurrently break multiple paradoxes of bandgap (E_g) with glass transition temperature (T_g), dielectric constant (ɛ_r) with E_g, and self-healing capability with T_g. In this contribution, a class of semi-alicyclic dipolar glass dielectric polymers (sAl-DG) is developed, with an alternating non-conjugated alicyclic unit and a strong dipolar group aromatic unit. The alicyclic unit synergistically confers a large E_g and the potential for strong self-healing while the other unit concurrently endows high polarization and thermal stability, effectively decoupling the multiple paradoxes. As a result, sAl-DG delivers large E_g with 3.99-4.26 eV, high T_g with 218-387 °C, high ɛ_r with 3.39-3.71 (200°C, 1 kHz) and simultaneously excellent self-healing ability with self-healing energy of 15.03 mJ. Hence, this molecular decoupling strategy enables a superior discharge energy density with 90% discharge efficiency (U_η90) of up to 6.2 J cm^-3 at 200 °C, and state-of-the-art 3.94 J cm^-3 at 250 °C. Plus, a stacked sAl-DG capacitor demonstrates 1.06 J cm^{- 3} at 94% efficiency under 250 MV m^-1 and 200°C, showcasing operational viability.