Portable Li-ion batteries are used extensively in iPods, laptops and mobile phones, and yet the mechanism of Li ion diffusion is not well understood. We have grown single crystals of LixCoO2 that are large enough to study Li ion diffusion via incoherent quasi-elastic neutron scattering on OSIRIS. The Li ion diffusion is confined within hexagonal planes and, therefore, the sample will be mounted with the (hk0) plane horizontal. We estimate a diffusion coefficient of about 10^-5 cm^2 s^-1 at T ~ 600K, and we shall measure the quasi-elastic energy broadening as a function of Q within the (hk0) plane at this temperature. The PG(004) will give sufficient energy resolution and Q coverage to compare with a Chudley-Elliott model of jump diffusion. The temperature dependence will yield activation energies and enable comparison with first-principles calculations.