Laser-induced graphene electrode-based supercapacitors: insight on the influence of aqueous electrolytes on its energy storage potential

Flexible supercapacitors based on laser-induced graphene (LIG) have emerged as a promising solution for scalable and cost-effective energy storage applications owing to their ease of fabrication and eco-friendly nature. However, the role of aqueous electrolytes in energy storage and conduction in thin-film electrodes has not yet been well explored. This study focused on optimizing the laser parameters, including the laser speed and power, to enhance the properties of LIG electrodes while investigating the influence of different aqueous electrolytes on electrochemical performance. The optimized laser parameters were a laser speed of 180 mm s⁻¹ and power of 40 W. The optimized electrodes were characterized using Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and Brunauer–Emmett–Teller surface parameter study. The characterization results revealed that the optimized LIG was highly defective, with an I_D/I_G ratio of 2.38, surface area of 25.146 m² g⁻¹, and pore diameter of 13.74 nm. Supercapacitors with H₂SO₄ exhibited a superior areal capacitance (34 mF cm⁻²) because of their high ionic conductivity, redox activity, and efficient H⁺ ion transport (hydrated radius: 2.8 Å). Na₂SO₄ and KOH showed lower capacitance (15 and 17 mF cm⁻²), limited by larger Na⁺ and K⁺ hydrated radii. The defect density increased fivefold compared to the benchmarks, enhancing the electrochemical performance eightfold. These findings underscore the role of laser parameter optimization in improving LIG-based energy-storage devices.