Extended Data Fig. 9: Schematic of the self-healing process in metallized polymer dielectric films.

The surge current induced by electrical breakdown can damage the polymer film by the intensive Joule heat, which can evaporate and oxidize the metal electrodes on the surface of films. When the freshly exposed area between the upper and lower electrodes is large enough to insulate the carbonized perforations around the breakdown site⁵³, the capacitor is still able to operate continuously at a full-rated voltage, merely at the expense of a small reduction in capacitance. This smart function of metallized films to clear a breakdown site with the energy released in the dielectric breakdown process is the so-called self-healing, which largely determines the service reliability of metallized dielectric polymer film capacitors⁵⁴.