Heat-Treatment Effect on Phase Stability, Cation Distribution, Chemical Composition, and Electrochemical Behavior for Fe-Substituted Li₂MnO₃

By combining coprecipitation, hydrothermal, and firing methods under various firing temperatures (500−750 °C), Fe-substituted Li 2 MnO 3 (nominal formula Li 1.2 Fe 0.4 Mn 0.4 O 2 ) samples were prepared. A pure O3 phase was obtained below 700 °C. However, a small amount of spinel ferrite-like LiFe 5 O 8 coexisted as an impurity phase for the sample that was fired at 750 °C. The maximum initial and 10th discharge capacities were obtained at 600−650 °C because of the balance between the development of 3d cation ordering, their primary particle size, and Li content, depending on the iron valence, which is changeable between 3+ and 4+.