Atomic insight into Li$^+$ ion transport in amorphous electrolytes Li$_x$AlO$_y$Cl$_{3+x-2y}$ (0.5 $\leq$ x $\leq$ 1.5, 0.25 $\leq$ y $\leq$ 0.75)

TL;DR

This study investigates Li$^+$ ion transport in amorphous Li-Al-O-Cl electrolytes using advanced simulations, revealing how O-doping influences structural features and ion mobility, with implications for improving solid-state electrolyte performance.

Contribution

It introduces a combined AIMD and MLIP-based MD approach to analyze the structural and transport mechanisms in amorphous oxychloride electrolytes, highlighting the role of O/Cl ratio in ion conduction.

Findings

O-doping creates Al-chain skeletons facilitating Li$^+$ movement.

Increasing O/Cl ratio initially enhances ion transport, then weakens it.

Controlling synthesis conditions can optimize electrolyte conductivity.

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 Li-Al-O-Cl system containing disordered structures with varying O/Cl ratio and Li$^+$ content 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 the increase of glass forming ability, causing Cl atoms' rotation around centered-Al within the tetrahedron thus facilitating the motion of Li$^+$ ions. However, further increase of 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, are useful to promote Li$^+$ ion conducting of oxychloride electrolytes.