Enhanced Electrochemical Performance of CuO Capsules@CDs Composites for Solid-State Hybrid Supercapacitor

Capsule-like CuO/CDs (CuO@CDs) with a surface area of 33.12 m² g^-1 were synthesized by the hydrothermal treatment, compared to 19.02 m² g^-1 for pristine CuO. An anode was then fabricated from capsule-like CuO@CDs to form a hybrid solid-state supercapacitor (HSSC) with the activated carbon (AC) cathode and PVA/1M KOH as an electrolyte. Three electrode system offered 1208.88 F/g (specific capacitance at 2 A/g current density) and unveiled a remarkable life cycle (retention) and Coulombic efficiency (CF): 93 and 98% after 5000 charge-discharge cycles at 10 A/g. In terms of performance, the HSSC delivered 1.5 V and 102.60 F/g (50.74 C/g) at 2 A/g, 8437.50 W/kg (power density), and 36.90 Wh/kg (energy density). The HSSC still retained 92% of cyclic stability and 83% of CF after 10,000 cycles.