Enhanced Energy Storage Properties of Polypropylene through Crystallization Modulation

Abstract

Polypropylene (PP), renowned for its high breakdown strength ( E ), low dielectric loss (tan δ), and excellent self-healing properties, is widely utilized as the state-of-the-art dielectric polymer in power capacitors and green electric vehicles. However, the low dielectric constant ( K ) and limited discharged energy density ( U e ) of polypropylene hinder the development of dielectric capacitors in miniaturization and integration. Here, a scalable polypropylene-based dielectric film with excellent energy storage properties comprising the lanthanide functional fillers (WBG) has been prepared using a melt extrusion process. Remarkably, the composite film with only 0.10 wt % of WBG demonstrates a high U e of 7.05 J/cm 3 and an ultrahigh charge–discharge efficiency (η) of 99.6% at 581.6 MV/m, coupled with long-term cyclic dielectric stability. The enhanced energy storage properties have been systematically analyzed and attributed to the formation of the β-crystalline phase and enhanced polarization induced by WBG. In a practical application demonstration, dielectric capacitors constructed from extruded composite films display stronger brightness, exhibiting a higher capacity than pure PP capacitors. This work provides a strategy to fabricate polypropylene dielectric films with excellent energy storage properties on an industrial scale.