Ultra-high caive energy storage at 200 °C achieved in polyetherimide-based nanocomposites by metal/ceramic composite design

Polymer films are promising dielectric materials for energy storage capacitors due to their light weight and flexibility. However, the adverse coupling between the permittivity and the breakdown strength presents a significant challenge for the enhancement of energy storage, especially at high temperatures. In this work, the Au@AO@Au@BT metal/ceramic composite nanofibers are prepared, in which barium titanate (BT) ceramic is used as the core to improve the permittivity and heat resistance of the nanocomposites. Aluminum oxide (AO) provides excellent interfacial compatibility, and the breakdown strength of the nanocomposite is enhanced by gold nanoparticles (Au NPs) with Coulomb blockade effect. This strategy achieves the compatibility of high permittivity and breakdown strength and improves the energy storage performance. As a result, the nanocomposites containing 0.3 wt% nanofibers achieve an ultra-high energy density of 8.64 J/cm 3 at 200 °C with an efficiency > 80 %, which is improved by 256 % compared to pure PEI (2.43 J/cm 3 ).