Synthesis and Structure Stability of Na-Rich P3-Naxmn1-Yniyo2 (X>0.8) for High Energy Density Na-Ion Batteries

Layered oxides with the general composition NaxMO2 (M=transition metal) have attracted a lot of attention for their composition diversity and promising electrochemical performances as positive electrode for sodium-ion batteries. Increasing the energy density while maintaining power capabilities delivered by P-type layered oxides is one of the remaining key challenges to make Na-ion batteries competitive for several use cases.The investigation of chemical process allows to demonstrate that high Na content P3-NaxMn1-yNiyO2 layered oxides can be obtained at low synthesis temperature using hydroxide precursors for both transition metal and Na sources. Besides, the obtaining of a Mn1-yNiy solid solution of a single P3-type polymorph allows to show the stabilizing effect of Ni and the comparison with widely reported P2-NaxMn2/3Ni1/3O2 reference compound, underlines that the stacking sequence P3-type vs P2-type does not clearly affect the electrochemical behavior of layered oxides.