Interfacial Engineering of Hydrophobic Montmorillonite for High-Energy-Capability Polypropylene Nanocomposite Dielectrics

Polypropylene (PP) dielectric capacitors are crucial for electronics and electric power systems due to their high power density. However, their relatively low energy density limits their practical application in energy storage devices, presenting a long-standing challenge. Montmorillonite (MMT), a natural phyllosilicate mineral abundantly found on earth, features a two-dimensional nanosheet structure and excellent insulating properties. MMT nanosheets have shown promise in enhancing the breakdown strength and energy storage capability of PP dielectric, but compatibility issues with the PP matrix remain a challenge. In this study, we propose a novel surface modification strategy in which polystyrene (PS)-capped MMT (PCM) nanosheets are synthesized through a polymerization–dissolution process. The modified PCM nanosheets demonstrate improved compatibility and are well dispersed within the PP matrix. Optimal loading of the PCM nanosheets effectively dissipate charge energy and hinder the growth of electric trees in the PP matrix. As a result, the PP nanocomposite with 0.2 wt% PCM nanosheets exhibits an enhanced breakdown strength of 619 MV m−1 and a discharged energy density of 4.23 J cm−3, with an energy storage efficiency exceeding 90%. These findings provide a promising strategy for the development of high-energy-density dielectric capacitors in an economical manner.