▎ 摘　　要

Polymer/graphene nanocomposites have shown promising potentials in energy storage applications due to their high permittivity, enhanced energy storage density, flexibility, and improved thermal and mechanical properties. The addition of graphene nanosheets to polymer matrix improves existing and incorporate new properties on such nanocomposites for various engineering applications. For instance, graphene nanosheets in polymer matrix are believed to form microcapacitors. Each microcapacitor contributes to the effective capacitance and dielectric constant of the composite. Although research has proved polymer/graphene composites as high dielectric constant materials, the major challenges facing their practical applications are high energy dissipation, high dielectric loss, and low electric field strength. In view of this, many researchers have shown efforts to minimize energy losses associated with polymer/graphene composites by insulating graphene nanosheets with different organic and inorganic substances. This is believed to prevent direct contact of graphene nanosheets and reduce the high mobility of pi-orbital or free electrons in the polymer matrix. However, maintaining high dielectric constant at low dielectric loss in polymer/graphene composites has not been achieved. If this challenge can be addressed in the future, polymer/graphene composites can yield energy storage capacity comparable with those of electrochemical capacitors. Therefore, this review considered energy storage and loss capacity of poly(vinylidene fluoride)/graphene nanocomposites from the perspective of electrical and dielectric properties. This article to the best of our ability reviewed various research results on dielectric constants/losses, breakdown strengths, energy densities, and electrical and thermal conductivities of poly(vinylidene fluoride)/graphene nanocomposites. Results extracted from the different published literature were tabulated and discussed at length to outline the reasons for the high dielectric loss in the neighborhood of percolation thresholds and the way forward.