Cathode Material Designing and Characterization: Co₃O₄/N‐doped Porous Carbon for Asymmetric Supercapacitors

Mesoporous Co 3 O 4 /N‐PC in powder form was synthesized via a wet‐chemical approach, and the resulting material was deposited onto nickel foam as a substrate without the use of a binder. Prior to device fabrication, a thorough analysis of suitable and cost‐effective aqueous alkaline and neutral electrolytes was conducted. Electrolyte optimization was performed using Co 3 O 4 /N‐PC/NF electrode with Na 2 SO 4 , NaOH, LiOH, and KOH electrolytes. The supercapacitor performance of the binder‐free deposited materials was found to be superior in KOH electrolyte compared to other aqueous electrolytes at equal concentrations. Further optimization of the KOH electrolyte concentration was carried out to achieve the best electrochemical performance for the Co 3 O 4 /N‐PC/NF electrode. Electrochemical results demonstrated that the Co 3 O 4 /N‐PC/NF electrode performed well in 1 M KOH electrolyte, surpassing its performance at other concentrations. Subsequently, a solid‐state asymmetric device was fabricated, utilizing Co 3 O 4 /N‐PC, activated carbon, and a KOH+PVA gel as the cathode, anode, and electrolyte, respectively. The assembled asymmetric Co 3 O 4 /N‐PC/NF‐AC/NF device exhibited an energy density of 12.08 Wh kg −1 and a power density of 2500 W kg −1 within a potential window of 1.5 V. Impressively, after nearly 3000 continuous GCD cycles, the device showed negligible initial specific capacitance decay. The device was also successfully tested for powering the LED.