Atomic insight into Li+ ion transport in amorphous electrolytes LixAlOyCl3+x−2y (0.5 ≤ x ≤ 1.5, 0.25 ≤ y ≤ 0.75)

Abstract

The recent study of viscoelastic amorphous oxychloride electrolytes has opened up a new field of research for solid-state electrolytes. In this work, we chose a Li–Al–O–Cl system containing disordered structures with varying O/Cl ratios and Li⁺ contents to study their structural characteristics and ion transport mechanism using ab initio molecular dynamics (AIMD) simulation and machine learning interatomic potential based molecular dynamics (MLIP-based MD) simulation. It is found that O-doping results in the presence of a skeleton of Al-chains formed by AlOCl tetrahedra and an increase in glass forming ability, causing Cl atoms' rotation around centered-Al within the tetrahedron thus facilitating the motion of Li⁺ ions. However, a further increase in the O/Cl ratio decreases the number of rotating Cl atoms, weakening the transport of Li⁺. So increasing glass forming ability without reducing Cl content or by methods through controlling synthesis conditions, is useful to promote Li⁺ ion conduction of oxychloride electrolytes.