Fe- and Ni-substituted Li2MnO3 (Li1+x(FeyNiyMn1−2y)1−xO2, 0 < x < 1/3, y = 0.1, 0.15, 0.2) was prepared using coprecipitation–calcination. Its electrochemical properties were sensitive to the calcining atmosphere or the charging mode. Calcination in N2 atmosphere or selecting stepwise charging mode respectively engender better electrochemical performance than calcination in an air atmosphere or selecting galvanostatic charging mode. In fact, the sample for which y = 0.15 calcined in N2 atmosphere exhibited higher discharge capacity than that for the sample calcined in air atmosphere when stepwise charging mode was selected. By selecting stepwise charging mode instead of galvanostatic charging mode, the initial discharge capacity was increased and cyclability was improved. Among the samples calcined in N2 atmosphere, samples for which y = 0.1 and 0.15 were found to have attractive composition as positive electrode materials by selecting stepwise charging mode.