Improvement of high-voltage cycling behavior of surface-modified Li[Ni1/3Co1/3Mn1/3]O2 cathodes by fluorine substitution for Li-ion batteries

To improve the electrochemical property of Li[Ni1/3Co1/3Mn1/3]O-2 at high upper voltage limit of 4.6 V, fluorine was partly substituted for oxygen. Variation of lattice parameters and X-ray photoelectron spectroscopy analysis suggest that fluorine is both substituted in bulk and coated on the surface of Li[Ni1/3Co1/3Mn1/3]O-2. Li[Ni1/3Co1/3Mn1/3]O2-zFz (z = 0.05 and 0.1) showed stable cycling performance and improvement of high rate capability compared to bare Li[Ni1/3Co1/3Mn1/3]O-2. In addition, fluorine substitution catalyzes the growth of the primary particles, which in turn resulted in high tap density as well as high volumetric capacity compared to Li[Ni1/3Co1/3Mn1/3]O-2. Differential scanning calorimetry at 4.6 V clearly shows that fluorine substitution markedly improves the thermal stability of Li[Ni1/3Co1/3Mn1/3]O2-zFz. (c) 2005 The Electrochemical Society.