Enhancing the Dielectric Strength and Energy Storage Performance of All-Organic Polycarbonate-Based Films via Conjugated Molecule Chlorination

Dielectric capacitors are critical devices for the advancement of renewable energy transmission and electric vehicles. However, conventional polypropylene-based capacitor films often suffer from a low energy density and limited thermal resistance. Development of low-loss polymer dielectric materials exhibiting excellent energy storage performance at room and high temperatures has become imperative. In this study, attractive dielectric and energy storage performances were achieved by regulating charge behavior. We selected quinone derivatives as calculated by the electron affinity of numerous molecules and incorporated them into a polycarbonate (PC) matrix as deep traps. With chloride substitution, a 61.2% enhancement in breakdown strength is achieved with energy density of 7.16 J/cm–3 at 700 MV/m, much higher than conventional pristine PC films (3.63 J/cm–3). This idea was inherited and applied to further develop a chlorinated perylene diimide (4Cl–C18PDI)-doped film for application at elevated temperatures. The dielectric breakdown strength reached 722.4 MV/m, representing a 50.8% enhancement compared to PC. Moreover, The PC/4Cl–C18PDI films demonstrated a high energy storage density (3.89 J/cm3 at 150 °C), which is more than ten times higher than that of the PC films while maintaining a low dielectric loss. This study offers valuable insights into the design of polymer-based dielectric materials with simultaneously high energy density and thermal stability.