Improved Mechanical Characterization of LiCoO2 Cathode Material by Ab-Initio Calculations Using Density Functional Theory

In the application of density functional theory (DFT) cal-culations to LiCoO2 (LCO) cathode material of lithium -ion batteries, this study investigates the differences between the obtained values for lattice constants, elastic constants, and stress-strain curves using different calculation condition such as exchange-correlation energy functionals; additionally, it attempts to improve the accuracy of the mechanical character-ization of the DFT calculation. The results reveal that the adoption of Perdew-Wang (PW91) functional with dispersion corrections is better in the structural optimization of the DFT calculation for the LCO cathode compared with other calcu-lation conditions, such as the adoption of Perdew-Burke-Ernzerhof (PBE) and revised PBE for solids (PBE-solid), which have been used in previous studies. The high accuracy of the lattice constant calculations in the structural optimiza-tion using PW91 results in a relatively high evaluation accu-racy of the mechanical properties of these cathode materi-als. Additionally, a strong correlation between the lattice (or lattice volumes) and elastic constants is observed; evidently, a slight deviation in the lattice constants causes a relatively significant change in the elastic constants. In some of the calcu-lation results for stress-strain curves, differences in the elastic limits (elastic regions) dependent on the selected exchange -correlation functionals are clearly observed.