Combined DFT–experimental, structural and microstructural analysis of Mo-doped NaNiFeMnO2 Layered Oxides

This study presents a combined computational and experimental investigation into the effects of molybdenum (Mo) doping on the structural and electronic properties of O3-type NaNi 0 . 25 Fe 0 . 25 Mn 0 . 5 O 2 (NNFM) layered cathode materials for sodium-ion batteries. First-principles density functional theory (DFT) calculations show that moderate Mo substitution, particularly at 10%, expands the Na-layer spacing and modifies the electronic states near the Fermi level, indicating enhanced electronic transport while preserving the layered framework. Experimental characterization using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric/differential thermal analysis (TGA/DTA), and microstructural imaging confirms phase purity, retention of the O3 structure, improved thermal robustness, and refined particle morphology in Mo-doped samples. The combined theoretical–experimental results identify 10% Mo-doped NNFM as a promising cobalt-free cathode composition with improved structural stability, more favourable electronic structure, and microstructural features expected to be beneficial for long-life sodium-ion battery operation.