Engineering Ion Diffusion Pathways in rGO‐integrated Ni‐doped Co3O4 Composites for Efficient Energy Storage in Asymmetric Supercapacitors

Enhancing the ion transport properties in redox‐active channels of transition metal oxides is challenging due to their moderate ionic and electronic conductivities, which need to be improved to meet the requirements of energy storage. To address such issues, an optimal molar ratio (0.08) of Ni was doped into Co3O4 with the highest weight percentage (8%) of rGO content to develop Co3.92Ni0.08O4@rGO (Co3O4‐IV), by employing a combination of hydrothermal/solvothermal methods. This approach showed promising electrochemical performance. Various characterization techniques were used to analyze phase development. X‐ray diffraction (XRD) survey verified the cubic phase, and uniform dispersion was observed by transmission electron microscopy (TEM). A comprehensive electrochemical investigation of the as‐fabricated electrode series demonstrated the Co3O4‐IV to be the most effective electrode, using a three‐electrode setup. The highest specific capacity, energy, and power density have been reported as 1431.30 C/g, 79.51 Wh/kg, and 8000 W/kg for Co3O4‐IV, based on galvanostatic charge/discharge (GCD) analysis. Additionally, the practical life application was assessed by constructing an asymmetric device and achieved an excellent energy density of 78.94 Wh/kg at 750 W/kg, with notable capacity retention of 90.10% after 10 000 cycles. Ion transport properties such as ionic conductivity (0.062 S/cm), transference number (0.19), rate constant (4.72 × 10−8 cm/s), and a reasonable diffusion rate (2.69 × 10−13 m2/s) support increased energy‐storage capability. From a practical life application perspective, the assembled coin cell demonstrated the ability to light up the LED for 0.48 s. Therefore, the device with enhanced ion transport features should be considered for advanced energy‐storage applications.