Positively charged colloidal Nanoparticle/Polymer composites for High-Temperature capacitive energy Storage: A promising approach

The issue of inorganic nanoparticle aggregation has impeded the development of nanocomposite applications. In this study, calcium silicate colloidal nanoparticles (CSO) with positively charged surfaces were prepared using triethylamine (TEA) as a capping agent. Owing to the electrostatic repulsion, the CSO colloidal particles are distributed evenly throughout the polyimide (PI), thus preventing the accumulation of electric fields and enhancing breakdown strength (BDS). Furthermore, the positively charged colloidal nanoparticles enhance the resistivity of the PI composite by absorbing electrons produced under high electric fields and reducing electron transit. The beneficial impact of CSO introduction on BDS is confirmed by the electrical breakdown simulation of PI composite films based on a Multiphysics finite element model. Besides, the positively charged colloidal particles promote the improvement of dielectric performance, resulting in the excellent high-temperature energy storage properties of the PI/CSO composite (BDS = 616.5 MV/m, Ue = 7.33 J/cm3, and η = 70 % @ 150 °C). Even in a high-temperature environment of 200 °C, the PI/CSO film still possesses rapid charge–discharge capability (t0.9 = 0.0554 μs) and an ultra-high power density (PD = 130.9 MW/cm3), positioning it as a highly promising material for high-temperature film capacitors.