Enhanced high-temperature energy storage performance in a 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 (U_e) and charge–discharge efficiency (η). Consequently, improving both U_e 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, an ultrafine UiO-66 metal–organic framework (MOF) with a strong “electron-withdrawing” feature is introduced into the PEI matrix as the outer layer to construct deep trap domains, while hydroxylated boron nitride nanosheets (OH-BNNS) with an “electron-repelling” characteristic are incorporated into the middle layer to form 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 for enhancing the comprehensive energy storage properties of the composite dielectric at high temperature. Specifically, at 150 °C and 200 °C, the sandwich-structured composite dielectric achieves a U_e as high as 4.95 J cm⁻³ and 3.94 J cm⁻³, as well as a high η of 90.7% and 83.4%, respectively. This corresponds to U_e improvements of 144% and 177% compared to PEI (∼2.03 J cm⁻³ at 150 °C and ∼1.42 J cm⁻³ at 200 °C). This study provides a useful paradigm for developing high-temperature and highly reliable polymer-based composite dielectrics.