Significant role of magnesium substitution in improved performance of layered O3‐Na‐Mn‐Ni‐Mg‐O cathode material for developing sodium‐ion batteries

The swap of inactive elements is an auspicious strategy for enhancing electrochemical performance and structural durability of the layer cathode material in sodium ion batteries (SIBs). In this regard, the O3-type Na0.9Mn0.65Ni0.35O2 and inactive element Mg substituted Na0.9Mn0.55Ni0.35Mg0.1O2 and Na0.9Mn0.60Ni0.35Mg0.05O2 cathode materials were prepared using simple solid state reaction for SIBs. The Rietveld refinement confirms the cathode materials have rhombohedral structure and R-3m space group. O3-Na0.9Mn0.55Ni0.35Mg0.1O2, O3-Na0.9Mn0.60Ni0.35Mg0.05O2, and O3-Na0.9Mn0.65Ni0.35O2 deliver discharge capacity of 174, 179, and 202 mAh g−1 in the voltage range from 2 to 4 V at current density of 0.1C. Moreover, partial quantity of magnesium (Mg) substitution enhances the structural stability by increasing sodium-oxide (NaO2) diffusion layer and reducing the transition metal oxide (TMO2) layers during cycling process in cathode materials for SIBs. HIGHLIGHTS O3-Na0.9Mn0.60Ni0.35Mg0.05O2 cathode is prepared via solid state reaction. Mg substitution is enlarged Na-ion diffusion layer. The prepared cathode reveals discharge capacity of 179 mAh g−1. The obtained cathode exhibits good cycle performance.