Improved Dielectric Constant and Energy Density of Polypropylene Film by Introducing BC Interlayers for Power Capacitor

This study introduces a bacterial cellulose (BC) functional layer into a polypropylene (PP) matrix to enhance the energy storage properties of PP films. The morphology and electrical properties of composite films with varying layer ratios were systematically investigated. Optimal performance was achieved with a PP to functional layer thickness ratio of 8:1:8, yielding an energy density of 6.33 J/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 25 °C, 5.59 J/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 85 °C, and 4.99 J/cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> at 125 °C. Leakage conductivity decreased by 84%-98%, and the DC breakdown field strength showed slight improvement at elevated temperatures. The sandwich structure effectively enhanced overall polarization through the functional layer, improving charge storage capacity. Furthermore, the BC layer, characterized by its tunable bandgap and high thermal stability, mitigated charge migration and enhanced high temperature performance. This approach highlights the potential of interfacial structure design to optimize the energy storage capabilities of dielectric films.