Improved Capacitive Energy Storage Nanocomposites at High Temperature Utilizing Ultralow Loading of Bimetallic MOF

It is urgent to develop high-temperature dielectrics with high energy density and high energy efficiency for next-generation capacitor demands. Metal-organic frameworks (MOFs) have been widely used due to their structural diversity and functionally adaptable properties. Doping of metal nodes in MOFs is an effective strategy to change the band gap and band edge positions of the original MOFs, which helps to improve their ability to bind charges as traps. In this work, the incorporation of ultralow loading (<1.5 wt%) of novel bimetallic MOFs (ZIF 8-67) into the polyetherimide (PEI) polymer matrix is exhibited. With the addition of ZIF 8-67, the breakdown strength and energy storage capacity of ZIF 8-67/PEI nanocomposites are significantly improved, especially at high temperatures (200 °C). For example, the energy densitiy of the 0.5 wt% ZIF 8-67/PEI nanocomposite is up to 2.96 J cm^-3 , with an efficiency (η) > 90% at 150 °C. At 200 °C, the discharge energy density of 0.25 wt% ZIF 8-67/PEI nanocomposites can still reach 1.84 J cm^-3 with a η > 90%, which is nine times higher than that of pure PEI (0.21 J cm^-3 ) under the same conditions, and it is the largest improvement compared with the previous reports.