Solid‐State Synthesis and Characterization of Mg‐Substituted P2‐Na0.70Ni0.45Mn0.55O2 Cathode Materials for Practical Sodium‐Ion Batteries

Abstract Sodium ion batteries are considered as a potential alternative to existing Li‐ion batteries. Layered transition metal oxides are found to be suitable cathode candidates for Na‐ion batteries. In this study, solid state synthesis of P2‐Na 0.7 Ni 0.45 Mn 0.55 O 2 with different Mg substitutions is reported. The synthesized materials are characterized thoroughly using X‐ray diffraction (XRD), field‐emission scanning electron microscopy (FE‐SEM), energy dispersive spectroscopy (EDS), inductively coupled plasma atomic emission spectroscopy (ICP‐AES), and x‐ray photoemission spectroscopy (XPS) analysis. SEM analysis reveals the morphology of synthesized materials to layered structure with a particle size in the range of 5–50 µm. Powder XRD shows all synthesized materials of P2 structure irrespective of Mg substitution. A spurious P3 phase is observed in 0% and 5% of Mg substituted samples which are absent in 10% and 15% of Mg substituted materials. Electrochemical performance analysis shows specific capacity reduces with Mg substitution whereas mid‐voltage reaches maximum up to 3.5 V with 10% substitution. 10% Mg substituted NMO shows a specific capacity 105 mA h g −1 in the voltage ranges of 2–4.3 V versus Na/Na + with excellent cycling stability and rate capability.