Regulating interfacial entropy to enhance high-temperature breakdown strength and energy storage performance of polypropylene nanocomposites

The rapid development of new energy vehicles and renewable energy sources has created a growing demand for polymers with high energy storage performance. However, the breakdown strength and energy storage performance of conventional polymers deteriorate significantly at elevated temperatures, making it difficult to meet the requirements of these emerging applications. In this work, an interfacial region was introduced into a polypropylene (PP) matrix to influence the characteristics of molecular chain movement (i.e., interfacial entropy), thereby enhancing the breakdown strength and energy storage performance of PP nanocomposites. Experimental results indicate that both the breakdown strength and energy storage performance of PP/MgO-PI composites first increase and then decrease with increasing filler concentration, reaching a peak at 3 wt%. A conduction-breakdown-energy storage combined model based on multi-entropy excitation, charge trapping, and molecular chain displacement was employed for simulation studies. It was revealed that the interfacial region structure confines the molecular chain movement, which reduces the molecular chain mobility and increases the charge hopping barrier. Consequently, this leads to a reduction in conduction loss and an enhancement in breakdown strength, ultimately improving both the charge-discharge efficiency and the discharged energy density.