In-depth lithium transportation mechanism and lithium intercalation study of BaLi2Ti6O14 anode material by atomistic simulations
QY Wang and FP Gu and YT Xie and MA Shui and J Shu, JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 879, 114790 (2020).
Atomistic simulations based on pedone interatomic potential model and first principle method are applied to observe the concerted motion of lithium ions in the lattice of BaLi2Ti6O14 anode material. The superimposed Li+ trajectory at all timeframes offers an intuitive, reliable image of the Li+ migration mechanism in crystal lattice. It reveals three possible Li+ migration paths, that is, 16 g Li-8e/8c interstitial octahedral site -16 g Li along c direction, 16 g Liempty 8f/ 4b16 g Li along a direction and Ti3/Ti4 mediated hopping along b axis realized by Ti-Li disordering. The site displacement function (SDF) analysis shows that Ti-Li exchange does not happen for most of the simulation time. Mean square displacement (MSD) of the Li+ motion gives the energy barrier value of three migration modes and accordingly, the extrapolated diffusion coefficients at room temperature. These results show that the Li+ transportation along c-axis and a-axis are the dominant Li+ migration routes for BaLi2Ti6O14 material. 7 intermediate phases are determined according to the formation energy curve and the voltage profile is predicted accurately accordingly. Also, the state of the charge (SOC) dependency of the lithium vitality shows that upon the initiation of the lithium ion intercalation, the lithium ion diffusion coefficient soars quickly, reaches the maximum at x = 1 and then fluctuates in a small range (1.6 x 10(-10) -2.9 x 10(-9) cm(2).s(-1)).
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