The surface of Li[Ni1/3Co1/3Mn1/3]O-2 particles was modified by a simple dry coating with (NH4)(3)AlF6 as a coating agent. The (NH4)(3)AlF6-coated Li[Ni1/3Co1/3Mn1/3]O-2 showed enhanced lithium-ion intercalation stability and thermal stability at 55 degrees C and a high cutoff voltage of 4.5 V. Electrochemical impedance spectroscopy and transmission electron microscopy showed that the (NH4)(3)AlF6 coating on the Li[Ni1/3Co1/3Mn1/3]O-2 particles played a key role in stabilizing the interface between the cathode and the electrolyte.