Improved Energy Storage Performance of Insulated Graphene/Polymer Nanocomposites

Abstract

This study focused on suppression of high energy dissipation associated with polymer/graphene nanocomposites (PGNs), which hinders their practical applications as energy storage dielectric materials. This was carried out by insulating functionalized graphene nanoplatelets (fGNPs) with hydroxylated titanium dioxide (TD-OH) in poly (vinylidene fluoride) (PVDF) matrix. The composites were prepared by solution blending and melt compounding methods to ensure well dispersion and in situ thermally reduction of the co-particles. Successful insulation of fGNPs was investigated using Transmission Electron Microscope (TEM). Morphology of the composites were studied using Scanning Electron Microscope (SEM). Capacitance, energy dissipation factor and electrical resistance of the composites were later measured. Results obtained showed significant reduction in energy dissipation factor (Df) for insulated graphene composites with appreciable capacitance compared to bared graphene composites. For instance, about 77% reduction in Df and capacitance of 8.5E-8F were recorded for 6.67wt%fGNPs/10wt%TD-OH composite film when compared to 6.67wt%fGNPs composite film with 2.89E-7F capacitance at 100Hz. These observations were attributed to increase in insulative layers between adjacent graphene nanosheets, indirect contact of graphene sheets in PVDF matrix and low current leakage. Also, insulated fGNPs composite films showed higher electrical resistance compared to bared fGNPs composite films. Based on the results obtained and analysis, appropriate insulation of graphene nanosheets in polymer matrix can address the challenge of high-energy dissipation associated with PGNs. Such materials are expected to find application in electrostatic capacitor designing and other related engineering applications.