Stable Oxyhalide-Nitride Fast Ionic Conductors for All-Solid-State Li Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Rechargeable all-solid-state lithium metal batteries (ASSLMBs) are crucial for electric vehicles and grid storage.
• Lithium (Li) dendrite growth in solid-state electrolytes (SSEs) hinders ASSLMB practical application.
• Effective SSEs require chemical stability with Li, fast Li transfer, and high interface energy.

Purpose of the Study:

• To design and synthesize novel, low-cost, and sustainable oxyhalide-nitride solid electrolytes (ONSEs).
• To investigate the dendrite-suppression capabilities of ONSEs in ASSLMBs.
• To evaluate the electrochemical performance and stability of ONSEs in Li||Li symmetric cells and ASSLMBs.

Main Methods:

• Synthesis of LiₓN<0xE1><0xB5><0xA7>I<0xE2><0x82><0x9B>-qLiOH (x = 3y + z, 0 ≤ q ≤ 0.75) oxyhalide-nitride solid electrolytes (ONSEs).
• Characterization of ONSEs for chemical stability against Li, interface energy, and ionic conductivity.
• Electrochemical testing of ONSEs in Li||Li symmetric cells and ASSLMBs with LiCoO₂ cathodes.

Main Results:

• The synthesized ONSEs exhibit chemical stability with Li and high interface energy (>43.08 meV Å⁻²), effectively suppressing Li dendrite growth.
• ONSEs demonstrate improved thermodynamic oxidation stability (>3 V vs Li⁺/Li) due to increased Li-N bond ionicity.
• Optimized ONSEs achieved an ionic conductivity of 0.52 mS cm⁻¹, enabling over 500 hours of stable cycling in Li||Li symmetric cells.
• Bilayer ONSE/Li₃InCl₆ electrolytes provided 90% capacity retention over 500 cycles in Li||LiCoO₂ cells.

Conclusions:

• The developed ONSEs offer a promising solution for suppressing Li dendrite growth in ASSLMBs.
• These sustainable and stable electrolytes enhance the safety and longevity of solid-state batteries.
• The findings pave the way for the practical application of ASSLMBs in demanding energy storage systems.