Comprehensive Characterization of SiO₂-Doped Activated Carbon from OPEFB and Geothermal Silica with Varying Concentrations for Lithium-Ion Coin Cell Anodes

In this research, activated carbon was synthesized from oil palm empty fruit bunches (OPEFB) and subsequently doped with SiO₂ derived from geothermal sand waste for application in lithium-ion coin cells. The chemical activation process, optimized through variations in NaOH concentration, identified C–1 M as the best structure, exhibiting a surface area of 107.79 m² g⁻¹, a specific capacity of 243.72 mAh g⁻¹, and voltage stability up to 2.52 V. Following silica doping, the SiO₂–G/C–1 M composite achieved a remarkable surface area of 191.67 m² g⁻¹, an enhanced capacitance of 375.88 mAh g⁻¹, and stable voltage output of 2.76 V. These improvements resulted from increased mesoporosity, expanded ion diffusion pathways, and enriched active site availability. The results validate silica-doped OPEFB carbon as a scalable, high-performance electrode potential for next-generation sustainable energy storage systems.