Lithium mobility in the layered oxide Li1−xCoO2

The Li+-ion chemical diffusion coefficient in the layered oxide Li0.65CoO2 has been measured to be D̃ = 5 × 10−12 m2 s−1 by three independent techniques: (1) from the Warburg prefactor, (2) from the transition frequency for semi-infinite to finite diffusion lengths in steady-state ac-impedence measurements and (3) from a modified Tubandt method that uses ac-impedance data to distinguish interfacial and surface-layer resistances from the bulk resistance of the sample. This value and a small increase in D̃ with (1 − x) in Li1−xCoO2, 0.45 < (1 − x) < 0.80, compare favorably with the D̃ = 5 to 7 × 10-12m2s-1 obtained by Honders for this system with pulse techniques. A qualitative discussion is presented as to why this composition dependence and why D̃ for this system is a factor of five larger than that for Li+-ion diffusion in LixTiS2.