Electrochemical performance of a symmetric supercapacitor device designed using laser-produced multilayer graphene

We report an economical approach for the fabrication of laser-produced graphene (LPG) electrodes, which results in an improved electrochemical performance. Polyimide polymer was used as the starting material for LPG synthesis and was irradiated under ambient conditions with a CO₂ laser. The prepared LPG samples were characterized by Raman spectroscopy and FTIR, which validated the formation of multilayer graphene containing sp² hybridized C＝C bonds. FE-SEM revealed three-dimensional (3D) sheet-like structures, while HR-TEM images showed lattice planes with an interplanar spacing of approximately 0.33 nm, corresponding to the (002) plane of graphene. Their electrochemical performance showed a remarkable areal specific capacitance (C_A) of 51 mF cm⁻² (170 F g⁻¹) at 1 mA cm⁻² (3.3 A g⁻¹) in a three-electrode configuration with 1 mol L⁻¹ KOH as the aqueous electrolyte. The LPG electrodes produced an energy density of ~3.5 µWh cm⁻² and a power density of ~350 µW cm⁻², demonstrating significant energy storage ability. They also had an excellent cycling stability, retaining 87% of their specific capacitance after 3 000 cycles at 1 mA/cm². A symmetric supercapacitor fabricated with LPG electrodes and the 1 mol L⁻¹ KOH electrolyte had a specific capacitance of 23 mF cm⁻² and showed excellent retention after 10 000 cycles, showing LPG’s potential for use in supercapacitors.