Fabricating sustainable electrodes for symmetric supercapacitors using lignosulfonate with two-step CO2 activation and plasma-assisted treatments

Abstract

In this study, lignosulfonate (LS) is utilized as a precursor to prepare lignosulfonate-activated carbon (LSAC) through a two-step CO₂ physical activation process. The LSAC is then employed as an electrode material and is assembled with PVA/H₂SO₄ gel electrolyte to fabricate supercapacitors. The experimental results reveal that the carbonization temperature, pre-oxidation treatment, and activation time considerably influence the pore characteristics of LSAC, thereby affecting its subsequent electrochemical performance. The optimal conditions, without pre-oxidation, carbonization at 700 °C, activation at 800 °C, and a 90 min activation time, LSAC achieves the highest specific surface area (1015.33 m²/g) and a carbon content of 83.110 %. The electrochemical testing demonstrates that the system attains the highest areal capacitance (646.78 mF/cm²) at a current of 0.25 mA, an energy density of 57.491 μWh/cm², a power density of 0.0667 mW/cm², and 99.13 % of capacitance retention after 4000 charge-discharge cycles. This research highlights the potential for LSAC to be applied in energy storage devices, thereby enhancing the recycling value of industrial lignin.