Improvement of High-Voltage Cycling Behavior of Surface-Modified Li[Ni[sub 1∕3]Co[sub 1∕3]Mn[sub 1∕3]]O[sub 2] Cathodes by Fluorine Substitution for Li-Ion Batteries

Abstract

To improve the electrochemical property of Li[Ni1∕3Co1∕3Mn1∕3]O2Li[Ni1∕3Co1∕3Mn1∕3]O2 at high upper voltage limit of 4.6V4.6V , 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]O2Li[Ni1∕3Co1∕3Mn1∕3]O2 . Li[Ni1∕3Co1∕3Mn1∕3]O2−zFzLi[Ni1∕3Co1∕3Mn1∕3]O2−zFz ( z=0.05z=0.05 and 0.1) showed stable cycling performance and improvement of high rate capability compared to bare Li[Ni1∕3Co1∕3Mn1∕3]O2Li[Ni1∕3Co1∕3Mn1∕3]O2 . 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]O2Li[Ni1∕3Co1∕3Mn1∕3]O2 . Differential scanning calorimetry at 4.6V4.6V clearly shows that fluorine substitution markedly improves the thermal stability of Li[Ni1∕3Co1∕3Mn1∕3]O2−zFzLi[Ni1∕3Co1∕3Mn1∕3]O2−zFz .