Bis(aryl) Tetrasulfides as Cathode Materials for Rechargeable Lithium Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Inorganic Chemistry

Background:

• Organotetrasulfides feature a linear chain of four sulfur atoms.
• They can accept up to six electrons in reduction reactions.
• This characteristic makes them promising candidates for high-capacity electrode materials.

Purpose of the Study:

• To investigate three bis(aryl) tetrasulfides as cathode materials in lithium batteries.
• To understand the reduction reaction mechanisms and identify discharge products.
• To explore the impact of functional groups on electrochemical performance.

Main Methods:

• Electrochemical testing of lithium half cells using tetrasulfide catholytes.
• Theoretical calculations to elucidate reaction pathways.
• Spectroscopic analysis for product identification.

Main Results:

• Tetrasulfides exhibited two distinct voltage regions during discharge: a high-voltage slope and a low-voltage plateau.
• The high-voltage region involved persulfide and thiolate formation; the low-voltage region involved Li2S2/Li2S formation.
• Lithium half cells demonstrated high specific capacities maintained over 200 cycles.

Conclusions:

• Three reduction processes were identified for aryl tetrasulfides.
• Discharge products were successfully identified.
• Functional groups significantly influence the electrochemical properties, guiding the development of optimal aryl polysulfides for high-energy lithium batteries.