High‐Performance Solid‐State Supercapacitors Based on Eco‐friendly N‐Doped Graphene‐like Nanosheets/Nanosized NiCo Oxide Nanocomposite Produced by Green Facile Technology

The present research focuses on the eco‐friendly production of N‐Doped Graphene‐like Nanosheets (E‐NG)/Nanosized NiCo Oxide Nanocomposite with remarkable electrochemical energy storage (EES) performance, as a highly‐valuable electrode material for real supercapacitor applications. Distinctively, the nanocomposite has been prepared, starting from the constituents’ synthesis and ending with their compounding, via ecofriendly, facile, cost‐competitive, and scalable techniques. Specifically, the nanocomposite compounding was carried out by a simple green ultrasound mixing in aqueous solution technique that has been first employed for the development of graphene/metal oxide nanocomposites as supercapacitors’ electrodes. The microstructural features of the produced E‐NG/0.5NiCo(O) nanocomposite reveal intensive interference between E‐NG nanosheets and NiCo(O) nanoparticles. The electrochemical evaluations disclose superb EES performance metrics of the nanocomposite in a 3‐electrode configuration and both symmetric and asymmetric 2‐electrode supercapacitor devices, as compared to literature. Thus, the asymmetric supercapacitor device based on E‐NG/0.5NiCo(O) nanocomposite and E‐NG electrodes gives outstanding EES performance, with a specific capacitance of 355 Fg − ¹, an energy density of 52.3 Whkg − ¹, and 90% capacitance retention after 5000 cycles, due to the synergistic combination of EDLC and pseudocapacitive mechanisms for charge storage as quantitatively estimated by Dunn's model. Overall, this study can greatly contribute towards substantial advancements in the global electrical power supply from renewable‐energy sources, employing green material‐manufacture technologies.