Molecular dynamics simulation of lithium ion diffusion in LiCoO sub(2) cathode material

• Published in: Solid state ionics 2015-11, Vol.280, p.10-17
• Main Authors: Fallahzadeh, R, Farhadian, N
• Format: Article
• Language: English
• Subjects: Cathodes; Diffusion; Diffusion coefficient; Electric potential; Lithium; Simulation; Transporting; Voltage
• ISSN: 0167-2738
• DOI: 10.1016/j.ssi.2015.07.001

In this study, lithium ion (Li super(+)) diffusion inside lithium cobalt oxide (LiCoO sub(2)) as a cathode material is investigated using molecular dynamics (MD) simulation. The effect of some important parameters such as voltage, Li super(+) content, and diffusion axis on Li super(+) diffusion coefficient value is explored and compared with the experimental data. The results show that Li super(+) diffusion coefficient in LiCoO sub(2) material is in the order of 10 super(- 12) to 10 super(- 13) cm super(2)/s, which is in agreement with the experimental data. Increased voltage value and decreased Li super(+) content raise the Li super(+) diffusion coefficient. In addition, the comparison of the Li super(+) diffusion coefficient along different axes of the crystal layer reveals that transporting lithium ions in a direction perpendicular to the layers of cathode material is more difficult than transporting them in a direction parallel to the layers. It can decrease the diffusion coefficient of Li super(+) by about 20%, especially at high voltage value and low Li super(+) content. But the diffusion coefficient in both directions has the same order of magnitude, which may explain different values of Li super(+) diffusion coefficient in various experimental methods. Replacing Co super(3 +) with Fe super(3 +) for increasing the capacity and stability of cathode material may slightly diminish the values of Li super(+) diffusion coefficient, which is in agreement with the experimental results.