Stabilizing a Lithium Metal Battery by an In Situ Li₂S-modified Interfacial Layer via Amorphous-Sulfide Composite...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• Solid-state electrolytes (CSEs) are promising for next-generation batteries but face challenges with interfacial stability and lithium metal anode compatibility.
• Decomposition of polymer components like poly(vinylidene difluoride) (PVDF) can form resistive interlayers, hindering ion transport.
• Improving the solid electrolyte-interphase (SEI) is critical for efficient lithium plating and stripping.

Purpose of the Study:

• To develop a novel composite solid electrolyte (SLCSE) strategy for in situ formation of a lithium sulfide (Li2S) interfacial layer.
• To enhance the wettability and lithium deposition process at the lithium anode/solid electrolyte interface.
• To investigate the impact of the Li2S-modified interfacial layer (SMIL) on electrochemical performance.

Main Methods:

• Fabrication of an amorphous-sulfide-LiTFSI-poly(vinylidene difluoride) (PVDF) composite solid electrolyte (SLCSE).
• In situ formation of a Li2S-modified interfacial layer (SMIL) between the lithium anode and SLCSE.
• Density functional theory (DFT) calculations to compare Li migration energy barriers through SMIL and LiF-modified interfacial layers (FMIL).
• Electrochemical characterization of the SLCSE, including ionic conductivity and transference number measurements.
• Assembly and testing of Li||SLCSE||LiFePO4 cells to evaluate rate performance.

Main Results:

• The novel SLCSE strategy successfully produces an in situ Li2S layer (SMIL) at the lithium anode interface.
• SMIL effectively retards PVDF decomposition and significantly improves lithium metal wettability with the solid electrolyte.
• DFT calculations show a lower Li migration energy barrier through SMIL compared to FMIL.
• The SLCSE exhibits a Li ionic transference number of 0.44 and ionic conductivity of 3.42 × 10⁻⁴ S/cm at room temperature.
• Li||SLCSE||LiFePO4 cells demonstrate excellent rate capability, retaining high capacity at elevated current densities.

Conclusions:

• The proposed in situ Li2S formation strategy using SLCSE is effective in creating a stable and conductive interface for lithium metal anodes.
• The SMIL enhances lithium ion transport and deposition, overcoming limitations associated with traditional solid electrolytes.
• This approach offers a promising pathway for developing high-performance and safe solid-state lithium batteries.