A proof of concept of a structural supercapacitor made of graphene coated woven carbon fibers: EIS study and mechanical performance

Abstract

A multifunctional supercapacitor based on a graphene nanoplatelet (GNP) coated woven carbon fiber (WCF) composite has been manufactured and its electrochemical and mechanical performance has been evaluated. Specific capacitance from voltammetry tests is about three times higher than the non-coated WCFs and several orders of magnitude above neat polymer WCF composites. Furthermore, an electrochemical impedance spectroscopy (EIS) analysis has been carried out in the coated and non-coated WCF capacitors. The equivalent circuit consisted on a series/parallel resistance/constant phase elements. EIS results show that the coated samples have superior capacitor properties, confirmed by chronoamperometry tests. The values of energy and peak power densities were also significantly higher in the coated WCFs, proving higher capabilities as supercapacitors. In addition, mechanical performance of structural supercapacitor is affected by the simultaneous addition of a polymer electrolyte and GNPs, with a reduction of mechanical strength when compared to neat polymer composites. However, and due to the lower viscosity of the electrolyte, there is a higher compaction of the material promoting an increase of WCF volume fraction on the LY-PEGDGE matrix samples, leading to similar values of Young Modulus. Despite the detriment of mechanical properties, they were far above other WCF-based structural supercapacitors. The proof of concept by illuminating a LED was highly successful, proving promising capabilities as structural supercapacitors.