Non-Intuitive Concomitant Enhancement of Dielectric Permittivity, Breakdown Strength and Energy Density in Percolative Polymer Nanocomposites by Trace Ag Nanodots
Polymer nanocomposite is considered as the promising dielectric media for electrostatic capacitors which are critical energy storage devices for pulse power applications due to its ultrahigh power density, superior cyclic lifetime and reliability. The maximum energy density of percolative nanocomposites filled with conductive fillers is seriously compromised by their intrincally low breakdown strength despite of the very high dielectric permittivity. Here we demonstrate that trace amount of Ag nanodots (~ 0.05 vol.%) in situ synthesized in poly(vinylidene fluoride-hexafluoropropylene) matrix give rise to concomitant enhancement of dielectric permittivity (~ 50%) and breakdown strength (~ 15%) hence ultrahigh discharge energy density (~ 27 J cm−3 ), which is the highest energy density ever achieved for percolative polymer composites. Experiment and first principle calculation results show the non-intuitive enhancement could be attributed to charge-transfer complexes formed between nanodots and the polymer chains and enhanced chain mobility under electric field.