Synthesis and characterization of oil palm biomass-based activated carbon with sodium alginate as solid-state supercapacitor materials for electric vehicle

This study investigates the performance of bio-based solid-state supercapacitor (SSS) for electric vehicle (EV) application to reduce usage of harmful and non-biodegradable materials in development of electrochemical energy storage. Oil palm empty fruit bunch was carbonized at 900°C and activated at 800°C to derive electrode active material. Sodium alginate (SA) was used as binder, electrolyte and separator. Specific surface area (SSA), porosity, surface morphology, crystal structure, elemental composition, as well as defects and disorder for the derived active material for electrode were determined. KOH-activated carbon (AC_KOH 800 ) achieved higher SSA of 1340 m²g −1 than deep eutectic solvent-activated carbon (AC_DES 800 ) of 154 m²g −1 . With KOH electrolyte and brittle glass fibre separator, the specific capacitance of 34.3 Fg −1 at 1.00 Ag −1 for the developed AC_KOH 800 electrode surpassed the 19.1 Fg −1 for the developed AC_DES 800 electrode. This could be attributed to the higher ions’ adsorption on the electrode surface of AC_KOH 800 than AC_DES 800 . SSS exhibited an energy density of 3.77 Whkg −1 at a power density of 65.0 Wkg −1 and capacitance retention rate of 76% after 1000 cycles. Also, SSS exhibited reduced internal resistance at elevated temperature with 1.70 Ω charge-transfer resistance at 85°C. The results indicated that bio-based SSS exhibited low internal resistance at elevated temperature as compared to room temperature due to enhanced ion mobility and conductivity as temperature increases. This highlights the importance of evaluating bio-based supercapacitor at varying temperatures to determine its performance and internal resistance under fluctuating operational temperatures of EV.