Improving the Energy Storage Performance of a Chlorinated Poly(vinyl chloride) Film at Elevated Electric Field and Temperature via a Simple Annealing Process

Abstract

High energy density and efficiency are crucial factors for polymeric dielectrics to satisfy the emerging demand in high-pulse metallized film capacitors. However, achieving high energy density in polar polymeric dielectrics is usually accompanied by a sharp decline in the energy discharge efficiency at elevated electric fields and temperatures. In this work, we investigated the dielectric and energy storage properties of chlorinated poly(vinyl chloride) (CPVC) with moderate polarity. Due to the random distribution of chlorine atoms on the polymer chain, CPVC displays a medium permittivity of about 3 and low loss. Moreover, high-temperature annealing is used to promote the rearrangement of CPVC chain segments, which contributes to the formation of CPVC microcrystals. Consequently, the storage modulus and glass transition temperature (Tg) along with the thermal stability of CPVC are improved due to the microcrystals as physical cross-linking points. Compared to pristine CPVC, heat-treated CPVC shows reduced dielectric loss and elevated breakdown strength. As a result, a high energy density of 9.4 J/cm3 and a discharge efficiency of 82.7% at 625 MV/m are obtained in heat-treated CPVC. This work offers a straightforward approach to improving the energy storage properties of CPVC so that it can be used for high-pulse metallized film capacitors.