Co-Free\nP2–Na_0.67Mn_0.6Fe_0.25Al_0.15O₂ as Promising Cathode\nMaterial for Sodium-Ion Batteries

Abstract

P2–Na_0.67Mn_0.6Fe_0.25Al_0.15O₂ (NaMFA) was developed as a cheaper and less-toxic\ncathode material for sodium-ion batteries than the Co analogous, P2–Na_0.67Mn_0.6Fe_0.25Co_0.15O₂ (NaMFC). Despite cobalt being considered to stabilize layered\nstructures upon cycling, NaMFA proved to have not only a higher specific\ncharge 163 mAh g^–1 compared to 141\nmAh g^–1 at a 0.1 C rate but also\na better cycling stability and rate capability than NaMFC. The structural\ntransitions occurring during sodiation/desodiation in the layered\nframes were characterized by operando X-ray diffraction (XRD) and\nX-ray absorption spectroscopy (XAS) analyses. Aluminum was found to\nstabilize the P2-phase and favor the Mn reduction on discharge, increasing\nthe amount of Na atoms reintercalated in the structure.