Metallised film capacitors (MFC) can operate under much higher voltage compared to the foil capacitor due to their self-healing (SH) properties

which caters to their application with high energy storage density requirement. Excellent results were achieved on the enhancement of the energy storage density of the dielectric material

whereas the SH properties of the modified material were less concerned. In the present study

the simultaneous improvement of the energy storage density and the SH properties were proposed

by constructing double-layer metallised films of polypropylene (PP) and polymethyl methacrylate (PMMA). The breakdown strength of the PP/PMMA first increased and then decreased with the rising thickness of the PMMA layer. The dielectric constant was also raised because of the introduced ester groups. The highest energy storage density of 5.93 J/cm3 was obtained

which was 62.47% higher than the neat PP

whereas the dielectric loss was maintained around 0.01. The SH properties of PP/PMMA were systematically evaluated

that the SH energy decreased with the increasing PMMA ratio

and the equivalent conductivity at the SH point of the PP/PMMA decreased to only 1% of the neat PP

which largely benefit the stability of the MFC with reduced temperature rise.