NiCo2O4 Electrodes Prepared by Inkjet Printing on Kapton Substrates for Flexible Supercapacitor Applications

This study explores the fabrication and electrochemical performance of flexible NiCo2O4-based pseudo-capacitor electrodes, inkjet-printed onto flexible Kapton substrates. To circumvent the insulating nature of Kapton, a thin Au interlayer (20 nm) was introduced, significantly enhancing electrical conductivity. The effect of NiCo2O4 mass loading, ranging from 0.1 to 0.5 mg cm−2, was investigated. Optimal performance was achieved at a loading of 0.3 mg cm−2 on Au/Kapton substrates, yielding a specific capacitance of 520 F g−1 at 3.3 A g−1 and 90% capacitance retention after 1000 charge–discharge cycles. These results confirm that inkjet-printed NiCo2O4 electrodes, when combined with a conductive interlayer, exhibit excellent pseudo-capacitive behavior on flexible, non-conductive substrates. This approach demonstrates the feasibility of scalable, low-temperature fabrication techniques for high-performance flexible energy storage devices, suitable for emerging wearable technologies.