Study on the influence of different manganese sources on the formation of P2/β Bi-phase cathode materials for sodium ion batteries

This work focuses on the effect of the of Mn 3+ /Mn 4+ ratio in the reactants on the structure and electrochemical properties of NaMn 0.9 Cu 0.1 O 2 cathode materials for sodium-ion batteries. By systematically varying the manganese valence states in the reactants, we observed a phase transition from the β-phase to the P2-phase with increasing Mn 3+ concentrations in the reactants, contrary to the expected favorability of the β-phase at higher Mn 3+ levels. This finding suggests a complex interplay between the valence states of the reactants and phase formation mechanisms, which needs further investigation. Additionally, electrochemical testing indicated that the phase composition significantly impacts the electrochemical performance of the material. Specifically, the M0 sample, possessing the optimal P2/β ratio, exhibited excellent electrochemical performances, achieving a high initial discharge capacity of 155.1 mA h g −1 and remains 88.1 % after 40 cycles. These results emphasize the importance of precursor selection and valence management in the development of high-performance cathode materials for sodium-ion batteries.