Résumé
In the search for sustainable cathode materials for Na–ion batteries, Mn-based oxides have emerged as attractive candidates owing to their earth abundance and structural versatility. In this context, a comprehensive investigation of the electrochemical behavior of the sodium-rich Mn2+ oxide Na10Mn4O9 toward sodium extraction/insertion is presented. The structural framework of this phase, prepared through a simple solid-state synthesis at 450 °C, is built on MnO4 and MnO3 polyhedra. Seven sodium ions per unit formula can be extracted during the first charge, and XAS analysis reveals the main transformation into a layered NaxMnO2·Na2O composite. Upon further cycling, once this phase is formed, the material delivers a reversible capacity of 110 mAh g–1 at an average potential of 2.24 V vs Na+/Na.