Dielectric and energy storage properties of nanocomposites with core–shell paraffin-engineered BaTiO3 in polyimides

In this work, PI was chosen as polymer matrix, PI composite films embedded with BaTiO 3 were prepared by in-situ polymerization. BaTiO 3 nanofillers were modified with paraffin to form a core–shell structure in order to improve the dispersion and compatibility with PI matrix. The permittivity of paraffin@BT/PI composite films with 40 wt% filler loading increase to 8.0 (1 kHz), which is about 2.4 times higher than that of pristine PI. The composites show stable capacitance in the range of 80 to180 °C. The energy storage density of composites with 40 wt% filler loading is as high as 3.31 J cm −3 under 180 MV m −1 , which is 2.4 times higher than that of pristine PI (0.97 J cm −3 at 180 MV m −1 ). However, the charge–discharge efficiency is 29.03%, and the discharge energy density is only 0.96 J cm −3 at 180 MV m −1 . To weigh the pros and cons, the composites with 30 wt% filler loading exhibit a better energy storage property, with a η of 70.45% (180 MV m −1 ) and discharge energy density of 1.03 J cm −3 at 180 MV m −1 .