High Interfacial-Energy Interphase Promoting Safe Lithium Metal Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Stable solid electrolyte interphase (SEI) formation is crucial for suppressing lithium dendrites in batteries.
• Achieving a desired SEI through electrolyte formulation is challenging due to complex electrochemical reactions.

Purpose of the Study:

• To develop a new strategy for engineering a stable SEI by modifying the lithium metal anode composition.
• To investigate the use of a lithium-strontium (Li-Sr) alloy anode for forming a strontium fluoride (SrF2)-rich SEI.

Main Methods:

• Designed a Li-11 wt% Sr alloy anode to intrinsically form a SrF2-rich SEI in fluorinated electrolytes.
• Employed Density Functional Theory (DFT) calculations and experimental characterization to analyze SEI properties.
• Fabricated and tested Li-Sr/Cu and Li-Sr/Li-Sr symmetric cells, as well as Li-Sr/cathode cells (LFP and NCM811).

Main Results:

• The SrF2-rich SEI exhibits high interfacial energy with lithium metal and superior mechanical strength, effectively suppressing dendrite growth.
• Li-Sr/Cu cells demonstrated high Coulombic efficiency (e.g., 99.42% at 1 mA cm-2) and stable cycling in Li-Sr/Li-Sr cells (180 cycles at 30 mA cm-2).
• Li-Sr anodes paired with LFP and NCM811 cathodes showed excellent capacity retention in various electrolytes.

Conclusions:

• Designing SEI properties by regulating the composition of the lithium metal anode is a viable and rational approach.
• The Li-Sr alloy anode strategy offers a promising pathway for developing safer and higher-performance lithium metal batteries.