The 0.3Li2MnO3·0.7Li[Mn0.60Ni0.25Co0.15]O1.975F0.025 cathode materials were synthesized by using a co-precipitation process in a Couette-Taylor reactor. Fluorine was substituted to facilitate the movement of lithium ions by forming more compact SEI layer and reduce the dissolution of transition metals, and lower internal impedance with charging/discharging cycling. In order to chemically remove the Li2O, the 0.3Li2MnO3·0.7Li [Mn0.60Ni0.25Co0.15]O1.975F0.025 composites was preconditioned by a HNO3 solution. The acid-treated 0.3Li2MnO3·0.7Li[Mn0.60Ni0.25Co0.15]O1.975F0.025 was showed the low initial irreversible capacity and the higher discharge capacity. The acid-treated and fluorine-substituted materials delivered the low initial discharge capacities, but it gradually increased during cycles.