Sustainable energy storage device based on NiCo2O4 nanoflakes via one step microwave irradiation

• Quick and energy-efficient method using 600 W power for 15 min at 60 °C. • Optimized particle size enhances electrochemical performance. • High specific capacitance 932 F/g for NiCo₂O₄ nanoflakes in 6 M KOH due to fast ion transport. • Stable cycling performance, making it suitable for supercapacitor applications. NiCo 2 O 4 nanoflakes (NFs) were synthesized by microwave irradiation method. Characterization of the synthesized NiCo 2 O 4 NFs was done using XRD, FTIR, SAED, SEM, HR-TEM and XPS. The crystallite size calculated using Debye-Scherrer formula was found to be ∼7.86 and nanoflake morphology was confirmed using SEM/TEM. Electrochemical studies, including cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS), were conducted to evaluate the performance. In a three-electrode system, NiCo 2 O 4 NFs demonstrated a high specific capacitance of 932 F g⁻¹ at a scan rate of 5 mVs⁻¹ and retained 97.37% capacitance after 2000 cycles at 5 A g⁻¹. Asymmetric supercapacitor device (NiCo 2 O 4 ||6 M KOH|| AC) delivered a maximal energy density of 25.90 Wh Kg⁻¹ and power density of 96.92 W Kg⁻¹. Due to rapid redox activity and superior electron-ion transport, NiCo 2 O 4 NFs exhibited excellent properties for usage in high performance supercapacitors with exceptional power density.