Fabrication and Characterization of Laser Scribed Flexible Supercapacitor

Abstract

Recently, supercapacitors have attracted a tremendous amount of attention as energy-storage devices due to their high-power density, fast charge–discharge ability, excellent reversibility, and long cycling life. In this research work, we demonstrate a laser scribed super capacitor based on polyimide (PI) substrate for the storage of electrical energy. PI substrate of thickness 200μm and area 1cm × 1cm was reduced by a laser engraver with a 450 nm wavelength in the form of stackable supercapacitor electrodes. Although, PI itself exhibits non-conductive behavior; however, by laser irradiation we change the surface properties of PI and reduce its resistance. The chemical property of irradiated PI was characterized by using Raman, FTIR and XRD where the carbon peak was observed at 2*theta = 25.44 in case of XRD results, which confirms the reduction of PI material in to a graphene-like substance. The electrical conductivity was analyzed with a probe station and observed to be 1.6mS. Two conductive regions were assembled into a capacitor device by sandwiching different electrolytes (KOH/H2O, H3PO4/H2O, KOH+KI/PVA, H3PO4/PVA) in between. The best capacitance value was achieved by using the H3PO4/PVA as an electrolyte in between the electrodes. During the charging and discharging characterization of the capacitor device, current density was observed to be 1.5mA/cm2. When this supercapacitor capacitance versus voltage analysis was carried out and the device showed 75mF/cm2 against a voltage sweep of ±2V. The galvanostatic charging and discharging curve shows a symmetric behavior with respect to time exhibiting the stability and durability of the device. At lower scan rate the capacitance value is higher but the value of current is lower. In this paper the device capacitance value is checked by changing the electrolyte, by changing the Scan rate and by changing the laser intensity. All these parameters effect the performance of the device.