Li₅NCl₂: A Fully-Reduced, Highly-Disordered Nitride-Halide Electrolyte for Solid-State Batteries with Lithium-Metal...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• High lithium-ion conductivity is essential for solid electrolytes in all-solid-state batteries.
• Many highly conductive solid electrolytes decompose when in contact with lithium metal, hindering battery performance.
• Stabilizing the lithium metal/solid electrolyte interface is critical for next-generation batteries.

Purpose of the Study:

• To investigate Li5NCl2 (LNCl) as a thermodynamically stable solid electrolyte against lithium metal.
• To elucidate the lithium diffusion mechanism and electrochemical stability of LNCl.
• To explore LNCl's potential as a protective layer in lithium-metal solid-state batteries.

Main Methods:

• Experimental techniques including Li nuclear magnetic resonance (NMR) and electrochemical impedance spectroscopy (EIS).
• Ab-initio calculations to understand Li diffusion pathways and electrochemical limits.
• Computational investigation of LNCl's chemical compatibility with other solid electrolytes.

Main Results:

• LNCl exhibits fast, locally confined Li motion, explained by disorder-induced diffusion jumps.
• The true anodic limit of LNCl was determined to be 0.6 V, aligning with theoretical calculations.
• LNCl demonstrates stability against lithium metal, suggesting its use as an artificial protection layer.

Conclusions:

• The study provides a fundamental understanding of Li diffusion in highly-disordered, fully-reduced electrolytes like LNCl.
• LNCl's stability and identified diffusion mechanisms offer a pathway for optimizing conductivity.
• LNCl shows promise as a protective layer for lithium-metal anodes in solid-state batteries.