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    Synergistic Impact of Vanadium Doping on the Structural and Electrochemical Performance of O3-NaMnO2 as Sodium-Ion Battery Cathode Material
    (Wiley-V C H Verlag Gmbh, 2025) Benzaid, Abdelali; Bounar, Nedjemeddine; Whba, Rawdah; Saoudel, Abdelmalek; Guler, Mihrihan; Altin, Serdar
    Vanadium-doped sodium manganese oxides (O3-NaMnO2) are promising cathode materials for sodium-ion batteries (SIBs) due to their structural stability and enhanced electrochemical performance. This study systematically investigates the effects of V doping (x = 0.03-0.50) on the structural, morphological, and electrochemical properties of NaMnO2 synthesized via a solid-state method. X-ray diffraction (XRD) confirms that low V doping (x <= 0.10) stabilizes the layered O3 structure and suppresses Jahn-Teller (JT) distortions, while higher doping induces a secondary Na0.5VO2 phase. Scanning and transmission electron microscopy (SEM/TEM) reveal that moderate V substitution (x = 0.10) improves particle uniformity and Na-ion transport. Electrochemical measurements show that both x = 0.03 and x = 0.10 exhibit good performance; however, x = 0.03 provides the best overall balance of high capacity, rate capability, and cycling stability, delivering initial charge and discharge capacities of 211 and 124 mAh/g, respectively. Redox and impedance analyses indicate reduced charge-transfer resistance and enhanced Na-ion kinetics at this composition. In contrast, excessive V doping (x >= 0.30) causes structural degradation and capacity fading. These results highlight the importance of controlled V doping in optimizing NaMnO2-based cathodes for high-performance SIBs.