Stability of the Solid Electrolyte Interface on the Li Electrode in Li-S Batteries

Area of Science:

• Electrochemistry
• Materials Science

Background:

• Lithium-sulfur (Li-S) batteries offer high theoretical energy density.
• The practical application of Li-S batteries is hindered by electrolyte instability and side reactions.
• Understanding sulfur and lithium interactions is crucial for improving Li-S battery longevity.

Purpose of the Study:

• To investigate the reactivity and stability of sulfur and lithium in various nonaqueous electrolytes.
• To identify reaction products between sulfur and lithium.
• To evaluate the protective role of the solid electrolyte interface (SEI) against these reactions.

Main Methods:

• High-performance liquid chromatography-mass spectroscopy (HPLC-MS) was employed to quantify sulfur and polysulfides.
• Quantitative stability studies of sulfur and lithium in eight different electrolytes were conducted.
• Qualitative identification of reaction products between sulfur and lithium was performed.

Main Results:

• Sulfur was found to react with lithium in most common electrolytes used for Li-S batteries.
• Specific reaction products between sulfur and lithium were identified.
• The solid electrolyte interface (SEI) on lithium demonstrated a protective effect in some electrolytes.
• Polysulfide ions were observed to degrade the SEI, compromising its protective function.

Conclusions:

• The inherent reactivity between sulfur and lithium in electrolytes is a significant challenge for Li-S battery development.
• The effectiveness of the SEI is limited by its susceptibility to degradation by polysulfide ions.
• Further research is needed to develop stable electrolytes and robust SEI layers for practical Li-S batteries.