Understanding the lithium transport mechanism in monoclinic Li3V2(PO4)(3) cathode material by atomistic simulation
YX Luo and M Shui and J Shu, RESULTS IN PHYSICS, 14, 102490 (2019).
In this work, atomistic simulation method based on core shell model is applied to observe the concerted motion of lithium ions in the perfect lattice of Li3V2(PO4)(3) cathode material. The simulation is carried out at a series of increasingly elevated temperatures in a super cell containing 8 unit cells. The superimposed Li+ trajectory at all timeframes offers an intuitive, reliable image of the Li+ migration in crystal lattice. It reveals Li+ diffusion mainly takes place on series of wave shaped planes without intersections extending infinitely toward a and c directions, or in a word, two dimensionally. The complete migration path along the c axis is supposed to be described as transferring through alternating 4a Li2 and 4a Li3 atoms. The Li+ migration along the a axis follows the mutually connected Li-O-n polyhedra chain. Li+ migration along the a axis owns the smallest energy barrier 0.44 eV. The estimated diffusion coefficient at RT is 3.2 x 10(-11) cm(2).s(-1). The hopping between two Li-O-n polyhedra chains via two vertex sharing Li2-O-5 polyhedron and Li1-O-5 polyhedron also makes diffusion along the b axis possible at higher temperature.
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