Designing coin-cell supercapacitors: Combining graphene foam with metal oxide composite electrodes for improved energy storage performance

This study presents the development of a high-performance supercapacitor using a sodium cobalt oxide integrated with graphene foam (NaCoO₂@GF), PVA-KOH membrane, and activated carbon derived from jute sticks (JC). The NaCoO₂@GF/PVA-KOH/JC full-cell device operates effectively across a voltage range of 0 to 1.7 V, demonstrating excellent reversibility and efficient charge storage through diffusion-controlled redox reactions. The device exhibits energy density up to 36.2 Wh kg⁻¹ at 0.5 A g-1 and power densitie up to 7749.2 W kg⁻¹ at 10 A, as confirmed by GCD data, and shows improved electrochemical performance after stability testing, with enhanced ionic conductivity and electrode material activation. Notably, the NaCoO₂@GF/PVA-KOH/JC supercapacitor achieves nearly 100 % Coulombic efficiency over 10,000 cycles, maintaining a retention of about 87 % for most cycles before a slight drop to 83 %. These results demonstrate the superior performance and potential of this composite material for practical energy storage applications.