Li₂S Cathode Mediated by Diphenyl Chalcogenides in All-Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium sulfide (Li2S) is a promising cathode material for all-solid-state batteries.
• Li2S exhibits high ion and electron blocking, leading to high charge overpotential and potential electrolyte decomposition.
• Sulfide electrolytes have a narrow electrochemical window, limiting battery operation.

Purpose of the Study:

• To investigate diphenyl chalcogenides as redox mediators to reduce the initial charge voltage of Li2S.
• To improve the utilization of Li2S in all-solid-state lithium-sulfur batteries.
• To enhance the stability and energy density of solid-state batteries.

Main Methods:

• Synthesis and characterization of Li2S-diphenyl chalcogenide composites.
• Electrochemical testing of all-solid-state batteries utilizing Li2S-diphenyl chalcogenide cathodes.
• Evaluation of battery performance, including initial charge capacity, voltage, and cycling stability.

Main Results:

• Diphenyl ditelluride (DPDTe) demonstrated the highest initial charge capacity for Li2S (963.1 mAh g-1).
• The Li2S-DPDTe composite cathode enabled a low initial charge voltage of 2.4 V with Li7P3S11 electrolyte and In-Li anode.
• The battery maintained an average areal discharge capacity of 0.9 mAh cm-2 after 360 cycles.

Conclusions:

• Diphenyl chalcogenides effectively act as redox mediators to lower the activation overpotential of Li2S.
• This approach aligns with the electrochemical window of sulfide electrolytes, enabling higher Li2S utilization.
• The findings provide valuable insights for developing high-energy-density all-solid-state batteries.