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 selfhealing 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 βcrystalline 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.