Improvement of electrochemical properties of Li[Ni0.4Co0.2Mn(0.4−x)Mgx]O2−yFy cathode materials at high voltage region

Spherical Li[Ni0.4Co0.2Mn(0.4−x)Mgx]O2−yFy (x = 0, 0.04, y = 0, 0.08) with phase-pure and well-ordered layered structure have been synthesized by heat-treatment of spherical [Ni0.4Co0.2Mn0.4−xMgx]3O4 precursors with LiOH·H2O and LiF salts. The average particle size of the powders was about 10–15 μm and the size distribution was quite narrow due to the homogeneity of the metal carbonate, [Ni0.4Co0.2Mn(0.4−x)Mgx]CO3 (x = 0, 0.04) precursors. Although the Li[Ni0.4Co0.2Mn0.36Mg0.04]O1.92F0.08 delivered somewhat slightly lower initial discharge capacity, however, the capacity retention, interfacial resistance, and thermal stability were greatly enhanced comparing to the Li[Ni0.4Co0.2Mn0.4]O2 and Li[Ni0.4Co0.2Mn0.36Mg0.04]O2.