Matter article published on Lithium oxychlorides!

Excited to share our latest work published in Matter! 🚀

“Exploring the soft cradle effect and ionic transport mechanisms in the LiMXCl₄ superionic conductor family”

https://lnkd.in/gHRrjzme

In this study, we investigate the crystalline LiMXCl₄ (M = Nb, Ta) oxychloride family—lithium superionic conductors that recently demonstrated an impressive Li-ion conductivity of 12.4 mS/cm at room temperature. But how much higher can we push the conductivity in this framework? And what fundamental mechanisms drive such rapid ion transport?

💡 Key findings:

Enhancing stability without compromising conductivity – By tuning cation (M) and anion (X) substitutions, we predict that fluoro-chlorides can offer improved electrochemical stability while maintaining high ionic conductivity.
Pushing conductivity beyond 100 mS/cm – Our analysis shows that the LiMXCl₄ framework can be optimized to achieve conductivities up to 100 mS/cm. Compared to close-packed chlorides and LaCl₃ frameworks, its higher Meyer-Neldel energy provides a clear advantage, enabling even greater conductivity and positioning LiMXCl₄ as a strong catholyte candidate for all-solid-state batteries.
Revealing the “soft cradle effect” – The LiMXCl₄ structures feature a unique 1D chain of octahedra, bound together by weak van der Waals interactions. Our analysis shows that the small-angle tilting motion of these octahedra is often temporally and spatially coupled with Li-ion hops. This behavior is similar to previously studied materials such as Li₃PS₄ and Li₂SO₄, where the isolated PS₄ or SO₄ tetrahedra tilt in response to nearby Li hops, providing additional degrees of freedom to stabilize migration pathways.

It was a great pleasure to work with Grace Wei on this paper. Also thanks to Xiaochen Yang and Yu Chen for their experimental efforts and Gerbrand Ceder for his invaluable support on this project. Looking forward to further experimental exploration of these oxychlorides as potential catholytes!