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 = ,0.04, y = ,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 LiOHH20 and LiF salts. The average particle size of the powders was about 10-15 u.m and the size distribution was quite narrow due to the homogeneity of the metal carbonate, [Ni0.4Co0.2Mn(0.4-x)Mgx]CO3 (x = ,0.04) precursors. Although the LifNi0.4Co0.2Mn0.36Mg0.04JO1.92F0.08delivered 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.o4]O2.