The diffusion coefficient of Li+ ions (DLi) in the battery material LixCoO2 was investigated by means of muon-spin relaxation (μ+SR), because DLi for positive electrode materials had not been determined correctly so far. Based upon performing experiments in zero-field and weak longitudinal-fields at temperatures up to 400K, the fluctuation rate of the fields on the muons due to their interaction with the nuclear moments was determined. Combined with susceptibility data and electrostatic potential calculations, clear Li+ ion diffusion was detected above ~150K. The DLi estimated from the fluctuation rate was in very good agreement with predictions from first-principles calculations, and the μ+SR technique was suggested to be a novel and optimum probe for detecting DLi.

A Novel Tool for Detecting Li Diffusion in Solids Containing Magnetic Ions; μ+SR Study on LixCoO2. J.Sugiyama, K.Mukai, Y.Ikedo, H.Nozaki, M.Månsson, I.Watanabe: Journal of Physics - Conference Series, 2010, 225[1], 012052