Dual-Anion Reinforced Cathode-Electrolyte Interphase for Stable Conversion-Type Cathode

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Pyrite (FeS2) is a promising cathode material for high-energy-density batteries.
• The polysulfide shuttle effect causes rapid capacity decline in FeS2 batteries.
• Advanced electrolyte design is crucial for improving battery performance.

Purpose of the Study:

• To develop a nonflammable locally concentrated ionic liquid electrolyte (LCILE) for Li/FeS2 batteries.
• To mitigate the polysulfide shuttle effect in FeS2 cathodes.
• To enhance the cyclic stability and energy density of Li/FeS2 batteries.

Main Methods:

• Formulation of a LCILE using LiFSI, AMImTFSI, and TTE.
• Investigation of the electrolyte's solvation structure and anion aggregation.
• Analysis of the cathode-electrolyte interphase (CEI) formation on the FeS2 cathode.
• Electrochemical cycling of Li/FeS2 batteries to evaluate performance.

Main Results:

• The LCILE exhibited a tailored solvation structure with FSI-TFSI dual-anion-dominated aggregates (AGGs).
• The AGGs effectively suppressed the polysulfide shuttle effect.
• A robust dual-anion-derived CEI was formed on the FeS2 cathode.
• The Li/FeS2 battery achieved 627 mAh g-1 after 200 cycles with 90% capacity retention.

Conclusions:

• The developed LCILE significantly enhances the cyclic stability of FeS2 cathodes.
• This electrolyte design offers a promising strategy for future high-energy-density Li/FeS2 batteries.
• The findings provide insights into designing advanced electrolytes for conversion-type battery materials.