A Li-Rich Fluorinated Lithium Zirconium Chloride Solid Electrolyte for 4.8 V-Class All-Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Chloride solid-state electrolytes (SEs) are crucial for all-solid-state batteries (ASSBs).
• Lithium zirconium chloride (Li2ZrCl6) shows promise due to abundant Zr but suffers from low ionic conductivity and poor high-voltage stability.
• Existing methods fail to simultaneously improve ionic conductivity and structural integrity.

Purpose of the Study:

• To develop a novel chloride solid electrolyte with enhanced ionic conductivity and high-voltage stability for ASSBs.
• To overcome the trade-off between lithium-ion mobility and structural stability in existing materials.
• To create a material suitable for practical application in high-performance ASSBs.

Main Methods:

• A two-pronged strategy involving partial fluorination and excess lithium ion incorporation was employed.
• Synthesis of a Li-rich fluorinated halide SE (Li2.3ZrCl6.1F0.2).
• Fabrication and testing of an all-solid-state cell using Li2.3ZrCl6.1F0.2, LiCoO2 cathode, and Li-In anode.

Main Results:

• The novel Li-rich fluorinated halide SE (Li2.3ZrCl6.1F0.2) demonstrated doubled ionic conductivity compared to pristine Li2ZrCl6.
• Significantly improved high-voltage stability was achieved.
• The all-solid-state cell delivered a high initial specific capacity (198.0 mAh g-1 at 0.1 C) and excellent capacity retention (78.5% after 150 cycles) within 3.0-4.8 V.

Conclusions:

• The developed Li-rich fluorinated halide SE offers a viable solution for enhancing ASSB performance.
• This material overcomes critical limitations of previous chloride SEs, enabling higher energy density and longer cycle life.
• The findings pave the way for advanced, safer, and more efficient all-solid-state batteries.