Lithium mobility in the layered oxide Li1− xCoO2

Abstract

The Li +-ion chemical diffusion coefficient in the layered oxide Li 0.65CoO 2 has been measured to be D ̃ = 5 × 10 −12 m 2 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 Li 1− x CoO 2, 0.45 < (1 − x) < 0.80, compare favorably with the D ̃ = 5 to 7 × 10 -12 m 2 s -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 Li x TiS 2.