A Quasi 2D Flexible Micro-Supercapacitor Based on MnO₂//NiCo₂O₄ as a Miniaturized Energy-Storage Device

A miniaturized and flexible asymmetric micro-supercapacitor (ASC) based on surface-modified MnO₂@Au and thin nanosheets of NiCo₂O₄@Au (termed 2D-qMnO₂//NiCo₂O₄ micro-supercapacitor) is reported. A lightweight and superior flexible micro-supercapacitor is successfully achieved using conventional microfabrication techniques. The proposed electrodeposition method is very effective for the surface modification and, as a result, uniform and high-quality 2D-quasi MnO₂ and NiCo₂O₄ thin-film formation on a collector current is achieved. The fabricated 2D-qMnO₂//NiCo₂O₄@Au and polymeric gel electrolyte-based micro-supercapacitor has advantageous features, with a high areal capacitance of 5.36 mF cm⁻². The 2D-qMnO₂//NiCo₂O₄ MSC delivers a high energy density of 0.42 mWh cm⁻² at 48.90 mW cm⁻² power density with superior cycling stability (89.62 %) over initial 5000 cycles. Impedance analysis showed that the 2D-qMnO₂//NiCo₂O₄ MSC device has a phase angle of −73° with an extremely small relaxation time constant of 14 ms. Finally, excellent device performance of the 2D-qMnO₂//NiCo₂O₄ MSC under different bending and twisting is demonstrated to evaluate its mechanical flexibility.