Laser-Induced Graphene electrode and Eco-friendly Chitosan-Poly(ethylene)glycol-LiClO4 Electrolytes for All-Solid state Flexible Supercapacitors

Abstract

The growing global demand for flexible, safe, and sustainable energy storage systems has intensified research into advanced materials for next-generation electrochemical devices. In response to this need, the present study focuses on the preparation and characterization of a biopolymer blend electrolyte using Chitosan (CS) and Poly(ethylene)glycol 8000 (PEG) with incorporating lithium perchlorate (LiClO₄) for solid-state supercapacitor applications. The optimal blend composition 70 wt.% of CS and 30 wt.% of PEG (named CP30) was subsequently doped with varying concentrations of LiClO₄ (10-50 wt.%, named CPLxx, with representing the weight percentage) to enhance ionic conductivity. Electrochemical Impedance Spectroscopy (EIS) revealed a maximum room temperature ionic conductivity of 127 μS cm^-1 for the CPL40 (70 wt.% CS, 30 wt.% PEG and 40 wt.% of LiClO₄) composition, attributed to improved segmental mobility and lithium-ion dissociation. Electrochemical stability up to 3.23 V was established via Linear Sweep Voltammetry (LSV). Two solid state double layer capacitors were fabricated with this solid electrolyte, employing activated carbon, and Laser induced graphene (LIG) as symmetric electrodes. The activated carbon-based device demonstrated a maximum specific capacitance of 5.32 Fg^-1 at 0.1 mAcm^-2, while the LIG-based device exhibited an areal capacitance of 18.83 mFcm^-2 at 0.08 mAcm^-2. Both systems showed remarkable cycling stability, retaining 75.5% and 71% of their initial capacitance after 5000 charge-discharge cycles. Additionally, the LIG-based device maintained 97.8% capacitance retention after 500 mechanical bending cycles, underscoring its flexibility and electrochemical durability. The influence of electrode loading was carefully addressed to enable a fair and meaningful performance evaluation of the two systems. These findings collectively demonstrate the potential of CS-PEG-LiClO₄ biopolymer electrolytes integrated with carbonbased electrodes to realize eco-friendly, high-performance, and flexible all-solid-state supercapacitors.