Interfacial Molecule Mediators in Cathodes for Advanced Li-S Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• The cathode-electrolyte interface in lithium-sulfur (Li-S) batteries presents complex reaction challenges hindering commercialization.
• Developing effective interfacial mediators is crucial for enhancing Li-S battery performance and stability.

Purpose of the Study:

• To design and implement small molecules as interfacial mediators for Li-S battery cathodes.
• To investigate the impact of tris(4-fluorophenyl)phosphine (TFPP) on polysulfide interactions and electrochemical kinetics.

Main Methods:

• Theoretical calculations to assess binding performance of candidate molecules.
• Experimental validation of TFPP as an interfacial mediator in Li-S battery cathodes.
• Electrochemical testing to evaluate capacity decay and cycling stability.

Main Results:

• Theoretical calculations indicated strong binding performance for TFPP.
• Experimental results showed TFPP's F and P atoms form strong chemical interactions with polysulfides.
• These interactions modified electrochemical kinetics and promoted short-chain lithium sulfide formation.
• The optimized electrode demonstrated a low capacity decay rate of 0.042% per cycle at 5 C over 1000 cycles.

Conclusions:

• Molecular design of interfacial mediators, specifically TFPP, significantly improves Li-S battery performance.
• TFPP effectively stabilizes the cathode-electrolyte interface by managing polysulfide behavior.
• The study provides a promising strategy for advancing the commercialization of high-performance Li-S batteries.