Chromium zirconium oxynitride: A unique cyclically stable high energy bimetallic pseudocapacitive electrode material

Binary transition metal oxides with abundant active sites are highly promising electrode materials for high-performance supercapacitors (SC), but their low conductivity remains a major challenge. Enhancing electrical conductivity can significantly improve their supercapacitive properties. In this study, a chromium zirconium oxynitride (CrZrOxNy) electrode material is designed and synthesized using an ammonia-free soft urea technique. The mesoporous CrZrOxNy material exhibits a specific surface area of 111 m(2)/g, whereas zirconium oxynitride (ZrOxNy) has 33 m(2)/g. The CrZrOxNy electrode achieves a specific capacitance of 1880 F/g at 1 A/g, compared to 927 F/g for the ZrOxNy electrode. This superior performance is attributed to the enhanced conductivity of the bimetallic oxynitride material. Incorporating Cr into the ZrOxNy matrix increases the conductivity to 1.259 S/m, while the conductivity of pure ZrOxNy is only 0.002 S/m. An asymmetric supercapacitor device using CrZrOxNy as the positive electrode material achieves maximum energy and power densities of 70 Wh/kg and 13.27 kW/kg, respectively, with 91 % cyclic stability after 5000 cycles. Additionally, the self-discharge current density of ZrOxNy (0.68 mA/g) is reduced to 0.5 mA/g in CrZrOxNy due to the effective substitution of chromium. This work demonstrates that CrZrOxNy is a promising electrode material for energy storage applications and presents a novel strategy for improving the performance of energy storage devices based on bimetallic oxynitrides.