Synthesis of zirconium oxynitride via ammonia-free soft urea method for an asymmetric supercapacitor with high power density

Abstract

Zirconium oxynitride (ZrOxNy) electrode material is successfully synthesized using an ammonia-free technique called soft urea. X-ray diffraction (XRD) is used to evaluate the crystal structure and phase purity of the as synthesised oxynitride material. XRD patterns reveal the presence of monoclinic zirconia (ZrO2) and rhombohedral ZrOxNy. Zirconium oxynitride possesses a specific surface area of 33 m2/g with a specific capacitance of 927 F/g at 1 A/g. An asymmetric supercapacitor device fabricated with ZrOxNy and activated carbon (Ac) (ZrOxNy//AC) delivered an energy density of 55.5 Wh/kg at a power density of 2.2 kW/kg. ZrOxNy-based supercapacitor outperforms most of the reported oxynitrides in terms of energy and power density. The as-developed device has a rate capability of 40.5% at 25 A/g and a capacitance retention of 93% over 2000 cycles. The material provides a stable Coulombic efficiency (100%) even at a higher current density (25 A/g). Leakage current studies are performed on the fabricated device, obtaining a leakage current density of 2.8 × 10−7 A/ cm2. This study reveals that ZrOxNy is a promising electrode material for energy storage applications.