Enhanced high-temperature energy storage performance in PEI-based dielectric composite via constructing dual charge carrier transport barriers

Abstract

Polymer-based film capacitors are extensively employed in contemporary electronic circuits and power systems. However, under elevated temperatures and high electric fields, the conduction loss of polymers increases significantly, resulting in substantial degradation of their energy storage density (Ue) and charge-discharge efficiency (η). Consequently, how to improve both the Ue and η at high temperature is a major challenge for the practical application of film capacitors. Herein, a sandwich-structured polyetherimide (PEI)-based nanocomposite dielectric is designed. Specifically, ultrafine UiO-66 metal-organic framework (MOF) with a strong "electron-withdrawing" feature is introduced into PEI matrix as the outer layers to construct the deep trap domains, while the hydroxylated boron nitride nanosheets (OH-BNNS) with an "electron-repelling" characteristic are incorporated into the middle layer to form the high potential barrier regions. By introducing dual charge carrier transport barriers within the composite dielectric, both the charge carrier concentration and mobility within the dielectric under extreme electro-thermal conditions can be effectively regulated, which is beneficial to enhancing the comprehensive energy storage properties of the composite dielectric at high temperature. Specifically, at 150 ℃ and 200 ℃, the sandwich-structured composite dielectric achieves the Ue as high as 4.95 J cm-3 and 3.94 J cm-3 , as well as the high η of 90.7% and 83.4%, respectively. This corresponds to Ue improvements of 144% and 177% compared to PEI (~ 2.03 J cm-3 at 150 ℃ and ~ 1.42 J cm-3 at 200 ℃). This study provides a useful paradigm for developing high-temperature and highly-reliable polymer-based composite dielectrics.