The chemical diffusion coefficients of lithium ions (D-Li) in spherical Li[Ni0.5Mn0.3Co0.2]O-2 are systematically determined by galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS). The D-Li obtained from GITT are greatly dependent on the lithium content and cell potential. In the charge process, the D-Li values are in the range of 9.0 x 10(-11) to 3.3 x 10(-9) cm(2) s(-1). In the discharge process, the D-Li values are in the range of 1.9 x 10(-11) to 3.9 x 10(-9) cm(2) s(-1). In addition, the minimum values in the D-Li are observed at the stoichiometry x approximate to 0.25 for Li1-x[Ni0.5Mn0.3Co0.2]O-2, which coincide with the voltage-plateau region at about 3.75 V. The Du obtained from EIS are in the range of 1.7 x 10(-11) to 6.5 x 10(-9) cm(2) s(-1) and the variation tendency with cell potential is consistent with the results obtained from GITT during the charge process. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.