Deep insight into the lithium transportation mechanism and lithium deintercalation study on epsilon-LiVOPO4 cathode material by atomistic simulation and first-principles method
YT Xie and QY Wang and KS Dai and M Shui and J Shu, JOURNAL OF POWER SOURCES, 503, 230061 (2021).
In this work, atomistic simulation together with density functional theory (DFT) method is applied to study the concerted motion of lithium ions and the intercalation/deintercalation mechanism in cathode material epsilon-LiVOPO4. Two kinds of one dimensional Li+ diffusion paths along the direction of ->(a) - ->(b), that is Li1-2iO5 chains and Li2-2iO5 chains with an energy barrier of 0.066 eV and 0.35 eV, are revealed by molecular dynamics (MD) and bond-valence-energy-landscape mapping (BVEL). At higher temperature, extra diffusion paths between different Li1-2iO5 chains and Li2-2iO5 chains are found. MD studies show that Li+ migration along a-axis and b-axis own the same energy barrier of 0.128 eV and the estimated diffusion coefficient at room temperature (RT) is 1.4 x 10(-6) cm(2) s(-1) at the fully lithiated state. The lithium mobility is extremely high for the perfect lattice of epsilon-LiVOPO. In the process of lithium ion deintercalation, the lithium mobility is gradually depressed. The state of charge (SOC) dependency of Li+ diffusion coefficients shows a downward tendency.
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