Simulation-assisted study of ion transport in low-cost laser-scribed graphene electrodes for supercapacitors
摘要
A proper understanding of ion transport and electric double-layer (EDL) formation in porous electrodes is essential for improving supercapacitor performance. In this work, ion transport and charge storage in porous carbon electrodes are first investigated using physics-based simulations in COMSOL Multiphysics by coupling secondary current distribution with transport of diluted species in porous media. The simulated cyclic voltammetry exhibits near-ideal capacitive behavior over scan rates of 0.02–0.10 V/s, yielding an average areal capacitance of ~ 0.2 mF/cm2 with a capacitance decay of ~ 6.6% at higher scan rates due to diffusion-limited pore accessibility. The effective Na⁺ transport rate increases from ~ 27 mol m−3 s−1 to ~ 210 mol m−3 s−1 with increasing scan rate, accompanied by concentration polarization. Guided by these results, laser-scribed graphene (LSG) electrodes are fabricated using a low-cost LightScribe DVD optical drive (5 mW, 788 nm). Laser reduction decreases the oxygen content of graphene oxide (GO) from 47.88 wt% to 32.44 wt% and increases the electrical conductivity to ~ 7.45 S/m. Electrochemical measurements in 1 M Na₂SO₄ reveal EDL-dominated behavior with an areal capacitance of 3.388 mF/cm2 at 0.05 V/s scan rate, an energy density of 0.12 mWh/cm3, power density of 6.94 W/cm3, whereas equivalent series resistance of ~ 36 Ω, showing good agreement with simulation predictions.