Enhancement of thermal stability and energy storage capability of flexible Ag nanodot/polyimide nanocomposite filmsvia in situsynthesis

High-temperature electrostatic capacitors are in urgent demand owing to the rapid development of advanced power electronic applications. However, obtaining polymer films with excellent discharge energy density and efficiency is still a huge challenge under harsh environmental conditions. Here, novel Ag nanodot/polyimide (Ag-ND/PI) nanocomposite films are designed and prepared through an in situ method. The energy storage capability and thermal stability of the PI matrix are significantly improved via loading a small amount of Ag-NDs, owing to the Coulomb-blockade effect and high thermal conductivity. Particularly, a high discharge energy density (Ud) of 5.16 J cm−3 at 600 MV m−1 is achieved for nanocomposite films with an ultralow filler content of 0.1 vol% Ag-NDs at room temperature, which is 260% higher than that of the pristine PI (2.02 J cm−3 at 450 MV m−1). Concurrently, the corresponding nanocomposite films exhibit an excellent high-temperature Ud of 2.56 J cm−3, together with efficiency exceeding 80% at a temperature of 150 °C at 400 MV m−1. Therefore, this research unveils a new method towards high-performance polymer capacitors for high-temperature applications.