Pseudocapacitive Storage in Molybdenum Oxynitride Nanostructures Reactively Sputtered on Stainless‐Steel Mesh Towards an All‐Solid‐State Flexible Supercapacitor

Abstract Exploiting pseudocapacitance in rationally engineered nanomaterials offers greater energy storage capacities at faster rates. The present research reports a high‐performance Molybdenum Oxynitride (MoON) nanostructured material deposited directly over stainless‐steel mesh (SSM) via reactive magnetron sputtering technique for flexible symmetric supercapacitor (FSSC) application. The MoON/SSM flexible electrode manifests remarkable Na + ‐ion pseudocapacitive kinetics, delivering exceptional ≈881.83 F g −1 capacitance, thanks to the synergistically coupled interfaces and junctions between nanostructures of Mo 2 N, MoO 2 , and MoO 3 co‐existing phases, resulting in enhanced specific surface area, increased electroactive sites, improved ionic and electronic conductivity. Employing 3D Bode plots, b ‐value, and Dunn's analysis, a comprehensive insight into the charge‐storage mechanism has been presented, revealing the superiority of surface‐controlled capacitive and pseudocapacitive kinetics. Utilizing PVA‐Na 2 SO 4 gel electrolyte, the assembled all‐solid‐state FSSC (MoON/SSM||MoON/SSM) exhibits impressive cell capacitance of 30.7 mF cm −2 (438.59 F g −1 ) at 0.125 mA cm −2 . Moreover, the FSSC device outputs a superior energy density of 4.26 µWh cm −2 (60.92 Wh kg −1 ) and high power density of 2.5 mW cm −2 (35.71 kW kg −1 ). The device manifests remarkable flexibility and excellent electrochemical cyclability of ≈91.94% over 10,000 continuous charge–discharge cycles. These intriguing pseudocapacitive performances combined with lightweight, cost‐effective, industry‐feasible, and environmentally sustainable attributes make the present MoON‐based FSSC a potential candidate for energy‐storage applications in flexible electronics.