Solvation-driven interphase engineering and mechanical failure pathways in large-scale anode-free lithium metal...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Anode-free lithium-metal batteries offer high energy density but face challenges with interface stability and safety.
• Current electrolytes often lead to dendrite formation and thermal runaway, limiting practical application.

Purpose of the Study:

• To investigate the role of fluorinated-ether solvation chemistry in interphase formation and battery performance.
• To develop a stable and safe electrolyte for high-energy anode-free lithium-metal batteries.

Main Methods:

• Utilized 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) in a localized high-concentration electrolyte.
• Analyzed Li+ solvation shell structure using advanced spectroscopic techniques (NMR, XPS, DEMS).
• Tested performance and safety in large-format 18650 anode-free cells.

Main Results:

• Introduced a novel PF6--dominated solvation shell structure.
• Formed a dense, LiF-rich solid-electrolyte interphase, enhancing stability.
• Achieved high energy densities (278-308 Wh kg-1 cell level) and near 100% coulombic efficiency.
• Demonstrated non-flammable behavior and UN38.3 safety compliance.

Conclusions:

• Fluorinated-ether solvation chemistry is critical for engineering stable interphases in anode-free lithium-metal batteries.
• Solvation-driven interphase engineering offers a viable pathway to safe, high-energy batteries.
• Lithium plating-induced mechanical expansion, not interfacial instability, is the primary failure mode.