Long-Term Stable Lithium Metal Anode in Highly Concentrated Sulfolane-Based Electrolytes with Ultrafine Porous...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Highly concentrated electrolytes with lithium bis(fluorosulfonyl)imide (LiFSI) and sulfolane (SL) offer promise for lithium metal batteries due to stability and safety.
• Conventional polyolefin separators exhibit poor wettability with these concentrated electrolytes, hindering stable lithium metal anode performance.

Purpose of the Study:

• To develop a separator that improves the wettability of concentrated LiFSI/SL electrolytes for stable lithium metal anodes.
• To investigate the electrochemical performance and interfacial properties of a novel separator in concentrated electrolytes.

Main Methods:

• Fabrication and characterization of a three-dimensionally ordered macroporous polyimide (3DOM PI) separator.
• Electrochemical testing of lithium metal cells using the 3DOM PI separator with a 1:2.5 LiFSI/SL electrolyte.
• Electrochemical and spectroscopic analyses to understand the solid electrolyte interphase (SEI) formation and stability.

Main Results:

• The 3DOM PI separator demonstrated excellent wettability and electrolyte uptake with the concentrated LiFSI/SL electrolyte.
• Stable lithium plating/stripping cycling was achieved with ca. 98% Coulombic efficiency for over 400 cycles at 1.0 mA cm^-2.
• Anion-derived SEI layer formation was observed, reducing side reactions and preventing dendrite growth.

Conclusions:

• Polar and porous separators like 3DOM PI are effective in enhancing affinity with concentrated electrolytes.
• The developed system enables the formation of a stable, Li⁺ ion conductive SEI layer, crucial for long-term lithium metal anode stability.
• This approach offers a viable strategy for achieving long-term stable lithium metal anodes in high-performance batteries.