Preparation of a novel cross-linked polyetherimide with enhanced breakdown strength and high-temperature energy storage performance

Polymer dielectrics with excellent energy storage performance at high temperature are urgently needed in advanced applications, such as hybrid electric vehicles, smart grid and pulsed power sources. Polyetherimide (PEI), which is supposed to be the most promising candidate among polymer dielectric materials, displays a limitation for high-temperature polymer dielectrics owing to the rapidly decreasing discharged energy density ( U d ) and charge-discharge efficiency ( η ). Herein, a novel PEI with cross-linked networks was firstly prepared by utilising 2,4,6-Triaminopyrimidine (TAP) as a cross-linker. The results showed that the breakdown strength of the cross-linked PEI (c-PEI) with 2 wt% TAP increased to 399.4 MV/m, showing an increment of 23.3% in comparison with non-cross-linked PEI. Additionally, owing to the restrained polarisation loss and relaxation loss by cross-linked networks, the dielectric loss of c-PEI dielectric gradually decreased with the increasing content of TAP. Of particular significance was the c-PEI dielectrics exhibiting improved U d and η at high temperature. The maximum U d of c-PEI with 2 wt% TAP was 2.53 J/cm 3 at 150°C, which was 24.8% higher than non-cross-linked PEI (2.11 J/cm 3 at 150°C). This research provides an innovative strategy to achieve novel PEI dielectrics with improved U d and η at high temperature.