Effect of Strain on Polaron Hopping and Electronic Conductivity in Bulk LiCoO2

We apply the concept of the elastic dipole tensor to study the effect of strain on polaron hopping and electronic conductivity in ionic crystals. As a model system, we choose the commercially used cathode material for Li-ion batteries, namely, LiCoO2, which has a layered structure with alternating planes of oxygen, lithium, oxygen, and cobalt. It is demonstrated that the electronic conductivity of LiCoO2 increases (decreases) exponentially with compressive (tensile) strains. The results of the analytical elastic-dipole-tensor method are shown to be in good agreement with a direct approach in which migration barriers of polaron hopping as a function of strain are evaluated using density-functional-theory-based nudged elastic-band calculations. In a broader sense, the presented analytical approach can be used to study the effect of any induced or applied elastic strain field on the electronic conductivity of polarizable semiconductors and insulators.