  Strain engineering is a powerful approach for tuning various properties of
functional materials. The influences of lattice strain on the Li-ion migration
energy barrier of lithium-ions in layered LiCoO2 have been systemically studied
using lattice dynamics simulations, analytical function and neural network
method. We have identified two Li-ion migration paths, oxygen dumbbell hop
(ODH), and tetrahedral site hop (TSH) with different concentrations of local
defects. We found that Li-ion migration energy barriers increased with the
increase of pressure for both ODH and TSH cases, while decreased significantly
with applied tensile uniaxial c-axis strain for ODH and TSH cases or
compressive in-plane strain for TSH case. Our work provides the complete
strain-map for enhancing the diffusivity of Li-ion in LiCoO2, and therefore,
indicates a new way to achieve better rate performance through strain
engineering.
