Fabrication of flexible supercapacitor through light scribe method to achieve high performance energy storage device

Abstract

For Electrode materials in supercapacitors, surface area and porosity is a key feature to achieve high performance. Due to a high theoretical surface area(>2600𝑚2𝑔⁄), promising flexibility, and high tensile strength, graphene and graphene based supercapacitors are getting the high region of interest from last few years. Reduced graphene oxide (RGO), material with 2D hexagonal structure of 𝑠𝑝2 carbons like graphene is preferably used at the place of graphene because of more readily available and possibilities of doping or other stuructural modifications to get better perfornmance. By inspiring from these favourable properties, in this work, we have used RGO as an electrode material in supercapacitor system which was formed by reduction of graphene oxide by a simple and low-cost light scribe technique. The chemical and structural characterization of material was carried out by XRD which shows the structural changes after reduction by lightscribe method. Optical images were taken with an optical microscope to observe the changes in colour contrast after reduction. SEM was also used to see the morphological change in material, and finally Raman spectroscopy was used to verify the RGO formation. Electrochemical characterization techniques cyclic voltammetry (CV), galvanostatic charge discharge (GCD) and electrochemical impedance spectrosocpy (EIS) were used to study the capacitive performance of the double layer supercapacitor system with RGO as an electrode material. Samples with different light scribe cycles and different thicknesses were fabricated and characterized to study the effect of lightscribe cycles to achieve higher performance in terms of higher specific capacitance. Supercapacitor sample with higher numbers of scribing cycles at 14 cycles shows higher specific areal capacitance of 8.75 mF/cm2 compare to lower scribed sample at 7 scribe cycles which shows areal capacitance of 0.765 mF/cm2 at a same current density of 0.125 mA/cm2. As second step of the experiment, surface modification was done by ultrathin coating of ZnO on RGO by atomic layer deposition technique (ALD) technique, which is a surface controlled layer-by-layer deposition method. Effect of ZnO coating was also studied by comparing the capacitive performance of the light scribed RGO sample before and after coating, and few layers of ZnO coated sample shows the enhancement of the specific areal capacity. To further achieve highest possible capacitance by optimizing the number of scribe cycles during reduction and effects of ZnO coating on RGO. To achieve highest possible capacities of such low cost highly desirable flexible system, the optimization of laser scribing parameters (for the uncoated system) and ALD coating parameters (to control the thickness and structure of the thin coating) are in progress.