Coin-Cell Electric Double-Layer Capacitors with African Palm Kernel Activated Carbon Under Series and Parallel Connection

The growing demand for efficient and sustainable energy storage has intensified interest in green materials known for their high-power density. In this work, we evaluated the electrochemical and electrical performance of coin-cell supercapacitors with activated carbon electrodes from palm kernel shell. Two activated carbons were obtained using KOH and ZnCl₂ as activating agents at 700 °C and then superficially modified with nitric acid. The KOH-activated carbon electrodes showed the highest specific surface area (1181 m² g^-1) and the best electrochemical behavior, reaching an average gravimetric capacitance of 56. ± 9.2 F g^-1. The coins were characterized electrically by series and parallel arrangements, yielding specific energy and specific power densities of 2.6 Wh kg^-1 and 475 W kg^-1, and 1.8 Wh kg^-1 and 353 W kg^-1, at 0.001 A and 0.75 V for parallel and series arrangements, respectively.