Thin-Film Faradaic/Electric Double-Layer Capacitor Enabled by Porous Chromium Nitride Electrode

With the rise of wearable device applications, efficient energy storage devices with flexible properties have become an important research direction. Among these devices, supercapacitors with high stability and instantaneous high power output for energy storage systems have attracted research attention. In this study, we demonstrate the possibility of applying nitrogen-doped chromium (Cr:CrN) thin films to flexible electrostatic double-layer capacitor (EDLC) electrodes. Chromium (Cr) electrodes undergo nitriding through sputtering, imparting interstitial defect characteristics and a nanoporous structure to the Cr layers. The resulting Cr:CrN layer not only exhibits excellent electrical conductivity but also enhances the faradaic process due to its interstitial defect properties. Experimental findings demonstrate that EDLCs employing Cr:CrN thin film electrodes exhibit exceptional performance, including fast charging, high current density tolerance, and cost-effectiveness. On glass substrates, the device achieves a maximum specific capacitance value of 6.69 mF/cm² and an energy density of 0.33 Wh/m² at an operating voltage of 3 V. Meanwhile, the flexible device demonstrates a specific capacitance value of 0.90 mF/cm² and an energy density of 0.02 Wh/m² at an operating voltage of 2 V. These results underscore the significant potential of Cr:CrN films as electrodes for EDLCs, particularly in flexible applications. Graphical Abstract: (Figure presented.)