  The influence of elastic strain on the lithium vacancy formation and
migration in bulk LiCoO2 is evaluated by means of first-principles calculations
within density functional theory (DFT). Strain dependent energies are
determined directly from defective cells and also within linear elasticity
theory from the elastic dipole tensor (Gij) for ground state and saddle point
configurations. We analyze finite size-effects in the calculation of Gij,
compare the predictions of the linear elastic model with those obtained from
direct calculations of defective cells under strain and discuss the
differences. Based on our data, we calculate the variations in vacancy
concentration and mobility due to the presence of external strain in bulk
LiCoO2 cathodes. Our results reveal that elastic in-plane and out-of-plane
strains can significantly change the ionic conductivity of bulk LiCoO2 by an
order of magnitude and thus strongly affect the performance of Li-secondary
batteries.
