Hybrid graphene nanoplatelet/manganese oxide electrodes for solid-state supercapacitors and application to carbon fiber composite multifunctional materials

In this study, composite electrodes with hybrid formulation of graphene nanoplatelets and manganese oxide were fabricated. Graphene nanoplatelets modified with MnO2 particles under sonication in an organic solvent. The produced solution was utilized to form film electrodes on aluminum substrate and also to wet carbon fiber cloth in order to form multifunctional structural composite with energy storage ability. The morphology of the graphene nanoplatelet/manganese oxide electrodes was characterized by Scanning Electron Microscopy and Raman spectroscopy. Quasi solid-state electrolytes, consisted of different % wt. loadings of succinonitrile (SN), ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4) and copolymer poly vinylidenefluoride-hexafluoropropylene (PVDF-HFP), were prepared to be utilized as ionic conductors for the formation of supercapacitors. Differential scanning calorimetry (DSC) was used to characterize the thermal stability of the electrolytes. DSC studies confirmed that polymer electrolytes remain stable in the same phase over a wide temperature range of -40 to 140 °C. Also, mixture of epoxy and the quasi-solid polymer electrolyte was prepared to form a solid polymer electrolyte with higher stiffness. The electrochemical performance of the supercapacitor electrodes was evaluated by cyclic voltammetry, charge/discharge and impedance spectroscopy. The maximum value of specific capacitance achieved for the film electrodes was ˜450 F/g and for semi-solid and solid polymer electrolyte was ˜165 F/g and ˜15 F/g respectively. Finally, tensile tests performed at ambient conditions to determine the mechanical behavior of the supercapacitors. The results of this study are very promising for the development of materials with high combined performance in the field multifunctional composite structural materials with energy storage capabilities and can applied in a variety of industries such automotive, aerospace and wearable electronics.