Hierarchical layer to layer of ternary heterostructure: Nanograin nickel carbonate embedded layered NiMnO₃-rGO-Co₃O₄ composite array as a high-performance electrode for hybrid supercapacitors

Heterostructured metallic electrode materials fabricated by altering the structurally engineered morphologies are promising in ameliorating electrodes' functionality in energy storage applications. Effective and novel double-shell sandwich-like NiCO₃/NiMnO₃-rGO-Co₃O₄ (Ni-NMO-rGO-CoO) nanoflake array (NFA) heterostructures were prepared on highly conducting 3D Ni foam using a two-step hydrothermal process. rGO wrapping on the NiCO₃ embedded NiMnO₃ (Ni-NMO) nanocomposite flakes improved the cycling stability and avoided volume expansion by acting as an interlayer. The surface decorated Co₃O₄ nanograins showed a uniform distribution over the rGO wrapped Ni-NMO and facilitated the pathways for fast ion diffusion kinetics to enhance the specific capacity of the electrode. The layer to layered Ni-NMO-rGO-CoO NFA electrode yielded an ascendant specific capacity of 188.8 mA h g⁻¹ (3.9 F cm⁻²) at 1 mA g⁻¹. The fabricated all-solid-state Ni-NMO-rGO-CoO//AC hybrid supercapacitors (HSCs) showed a superior energy density of 57.2 W h kg⁻¹ at 472.2 W kg⁻¹ with 97.7% capacitance retention after 10 000 cycles. The fabricated HSCs have potential applications in portable electronics. The Ni-NMO-rGO-CoO NFA ternary layered architecture offers a promising approach for fabricating high-performance hierarchical composite array electrodes for next-generation energy storage devices.