Mechanical Properties of LiCoO2 Under High Pressure Conditions: A First-Principles Study

Lithium cobalt oxide (LiCoO2) is a widely used cathode material whose mechanical behavior under pressure is increasingly relevant to cell manufacturing and extreme-environment applications. Yet a coordinated understanding of how hydrostatic pressure simultaneously affects its structural, elastic, and vibrational properties has been lacking. Here, we employ first-principles DFT-GGA-PBE calculations to investigate the structure, elastic constants and moduli, and phonon band structure of R3¯m LiCoO2 under hydrostatic pressure from 0 to 50 GPa. The in-plane and interlayer lattice parameters contract anisotropically, with the c-axis showing greater compliance; our computed c/a evolution reproduces the experimentally observed decreasing trend, lying systematically ∼2% below the convergent experimental datasets over the experimentally covered pressure range, with the deviation narrowing toward the highest experimentally covered pressures. All six independent pressure-corrected elastic constants increase monotonically and satisfy the Born stability criteria over the full pressure range. The polycrystalline bulk modulus more than doubles from 0 to 50 GPa, while the Young’s and shear moduli increase by 27–37%, with zero-pressure values (BH=144.76 GPa, EH=214.65 GPa, GH=85.66 GPa) in good agreement with pulse–echo and nanoindentation measurements. Phonon frequencies exhibit a systematic blueshift, with the highest-frequency optical modes hardening at an average rate of 0.102 THz/GPa, and remain real across the entire Brillouin zone, confirming the dynamical stability of the R3¯m phase. The correlated hardening of elastic moduli and phonon frequencies is consistent with pressure-induced bond shortening and the associated strengthening of the interatomic interactions, as evidenced by the monotonic contraction of the Co–O and Li–O bonds (by 4.1% and 9.7%, respectively, over the full pressure range). These results provide a quantitative benchmark for the mechanical behavior of layered oxide cathodes under pressure and offer a reference for related materials.