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    Influence of pressure on elasticity, mechanical properties, and Li diffusion in battery electrode material LiCoO2: First-principles calculations
    (2023-09-01)
    Sailuam, Wutthigrai
    ;
    Fongkaew, Ittipon
    ;
    Busayaporn, Wutthikrai
    ;
    Klinkla, Rakchat
    ;
    Phacheerak, Kanoknan
    This study used first-principles calculations based on density functional theory with generalized gradient approximation (GGA) of the Perdew Burke and Ernzerhof (PBE) parameterized form to investigate the influence of pressure on the structural, elastic, and mechanical properties of rhombohedral LiCoO<inf>2</inf>. The results indicate that rhombohedral LiCoO<inf>2</inf> remains stable up to 10 GPa. The calculated ground state properties agree well with experimental and other calculation data, validating the approach. Additionally, the calculated elastic constants, bulk modulus, Young's modulus, shear modulus, and Poisson's ratio at 0 GPa agree with previous results. The study found that all elastic constants continuously increase with increasing pressure. The deformation resistances along the axial direction are stronger than those in shape. The relationship between elasticity and length is such that C<inf>11</inf> > C<inf>33</inf>, indicating that the incompressibility along the a axis is stronger than that along the c axis. The analysis of Poisson's ratio (ν) and Pugh's criterion B/G strongly suggests that rhombohedral LiCoO<inf>2</inf> exhibits ductile behavior under pressure up to 10 GPa. The material is clearly anisotropic behavior, but the material exhibits improved isotropic behavior as pressure increases. Regarding Li ion diffusion in rhombohedral LiCoO<inf>2</inf>, the study found that the migration pathway for Li ions in rhombohedral LiCoO<inf>2</inf> is a direct route that extends from the V<inf>Li</inf> site to the closest Li site. The diffusion process is hindered by a diffusion energy barrier of 0.87 eV, which is in good agreement with available theoretical data. Furthermore, the Li ion diffusion energy barrier increases with pressure because the decrease in d<inf>mean</inf> and polyhedral volume, along with changes in angle and torsional distortion factors of CoO<inf>6</inf> octahedra, which can reduce the charging and discharging speeds of Li-ion batteries that use rhombohedral LiCoO<inf>2</inf> as the cathode material.
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    Effect of thermal annealing on the structure of LiCoO2 powders prepared by co-precipitation method
    (2021-12-01)
    Khejonrak, Awadol
    ;
    Chanlek, Narong
    ;
    Sukkha, Usa
    ;
    Triamnak, Narit
    ;
    Chirawatkul, Prae
    Lithium cobalt oxide (LiCoO<inf>2</inf>) powder was prepared by co-precipitation method and annealed at different temperatures of between 300 and 700 °C. The effect of annealing temperature and effect washing process with deionized water on the crystal structures of the prepared LiCoO<inf>2</inf> powders were thoroughly studied by Synchrotron powder X-Ray Diffraction (Syn-XRD), X-ray Absorption Spectroscopy (XAS), Dispersive Raman Microscopy (Raman) techniques. The change in chemical composition as a function of annealing temperature was also investigated by X-ray Photoelectron Spectroscopy (XPS) technique. The crystal structural results identified the phase evolution of the prepared LiCoO<inf>2</inf> powders upon heat treatment. The formation of HT-LiCoO<inf>2</inf> phase was observed at annealing temperature as low as 300 °C.