Maybe this reference can give the information you need.
Shaju, K. M.; Subba Rao, G. V.; Chowdari, B. V. R., Electrochemical Kinetic Studies of Li-Ion in O2-Structured Li2/3(Ni1/3Mn2/3)O2 and Li(2/3)+x(Ni1/3Mn2/3)O2 by EIS and GITT. Journal of The Electrochemical Society 2003, 150 (1), A1-A13.
Vasu - Following techniques - Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and Galvanostatic, Intermittent Tritration Techniques are used to determine diffusion Coefficient. Diffusion Coefficient values varies from 10 base -14 to -12. cm sq/sec.
Also look up the paper published in Solid State Ionics - vol 180 issues 2-3, 9th March 2009 p, 222. Good luck.