Study of [EMIM] [EtSO₄] ionic liquid-based gel polymer electrolyte mediated with hydroquinone redox additive for flexible supercapacitors

Gel Polymer Electrolytes (GPEs) are considered as suitable candidates in the design of energy storage devices like flexible supercapacitors due to their higher safety and flexibility. Incorporating small quantity of redox additives in GPE significantly improves their conductivity and is considered as an innovative method to enhance the capacitance of supercapacitors, because both electrolyte and electrode materials contribute to the capacitance. In this work, performance of Flexible Supercapacitor's (FSCs) using symmetrical Laser Induced Graphene (LIG) as electrodes and ionic liquid 1-Ethyl-3-Methylimidazolium Ethyl Sulfate [EMIM] [EtSO₄] incorporated in Gel Polymer Electrolyte (GPE) with and without redox additive Hydroquinone (HQ) is presented. Upon electrochemical characterization using Galvanostatic Charge Discharge (GCD), it was found that the FSC with redox additive showed highest areal capacitance and energy density of 15.1 mFcm⁻² and 1.54 μWhcm⁻² respectively and FSC without redox additive showed an areal capacitance and energy density of 1.94 mFcm⁻² and 0.14 μWhcm⁻² respectively at 2 mAcm⁻². The device with redox additive also showed 100 % columbic efficiency after 50 cycles and maintained 80 % capacitance for 5000 charge-discharge cycles. Additionally, the electrolyte with the redox additive showed superior conductivity of 10.8 mScm⁻¹, demonstrating that modifying electrolyte by adding redox additive has been a simple yet effective method to enhance the overall performance of FSCs. Also, the synthesized LIG was characterized by X-ray Diffraction (XRD), Raman and Scanning Electron Microscopy techniques which confirmed the formation of bi-layer porous graphene.