Effect of mixed phase with shape control on lithium ions transport during conversion reaction in the manganese oxide anode

Abstract

Conversion-type transition metal oxides have gained significant attention as promising anode materials for next generation lithium-ion batteries (LIBs). In this work, the various oxidation states and shapes of manganese oxide are investigated to utilize conversion-type anode materials. A nanostructured δ-MnO₂ was synthesized by the solution plasma process, followed by controlled calcination temperature to achieve distinct phases and morphologies, including nanocrystalline α-MnO₂, rod-shaped α-MnO₂/Mn₂O₃, and microscale Mn₂O₃. Among these, the mixed phase of α-MnO₂/Mn₂O₃ exhibited excellent electrochemical performances, including a high specific discharge capacity of 1352 mAh/g at 0.1 A/g and high-rate capability of 545 mAh/g at 2 A/g. The results of materials and electrochemical characterization suggested that α-MnO₂ contributed to the enhanced specific capacity, whereas Mn₂O₃ provided sufficient Li-ion transport. Moreover, the rod-shape with a suitable specific surface area led to stable electrolyte interphase formation, resulting in a higher specific capacity at both low and high c-rates. Our finding of mixed phases with morphologies effects for electrochemical properties contributes to the electrode design and development of Mn-based anode for next generation LIBs.