Influence of Stacking Morphology and Edge Nitrogen Doping on the Dielectric Performance of Graphene–Polymer Nanocomposites

We demonstrate that functional groups obtained by varying the preparation route of reduced graphene oxide (rGO) highly influence filler morphology and the overall dielectric performance of rGO-relaxor ferroelectric polymer nanocomposite. Specifically, we show that nitrogen-doping by hydrazine along the edges of reduced graphene oxide embedded in poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) results in a dielectric permittivity above 10 000 while maintaining a dielectric loss below 2. This is one of the best-reported dielectric constant/dielectric loss performance values. In contrast, rGO produced by the hydrothermal reduction route shows a much lower enhancement, reaching a maximum dielectric permittivity of 900. Furthermore, functional derivatives present in rGO are found to strongly affect the quality of dispersion and the resultant percolation threshold at low loading levels. However, high leakage currents and lowered breakdown voltages offset the advantages of increased capacitance in these ultrahigh-k systems, resulting in no significant improvement in stored energy density.