In Situ Polysulfide Detection in Lithium Sulfur Cells

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-sulfur (Li/S) batteries offer higher specific energy than Li-ion batteries but suffer from capacity fade.
• This fade is primarily caused by the dissolution of intermediate polysulfide species in the electrolyte, hindering long-term cycling stability.
• Current methods to study polysulfide solubility often rely on ex-situ spectroscopic techniques, which can be complex and time-consuming.

Purpose of the Study:

• To develop a novel in situ electrochemical method for detecting and quantifying dissolved polysulfides in Li/S batteries.
• To correlate electrochemical signals with polysulfide concentrations and battery performance.
• To validate the effectiveness of different strategies for mitigating polysulfide dissolution.

Main Methods:

• An in situ electrochemical polysulfide detection method was established using cyclic voltammetry.
• The voltammetric response was analyzed and correlated with discharge capacity and polysulfide levels.
• Experiments included modifications to the sulfur cathode (metal sulfides) and separator (ceramic coatings), as well as the use of highly concentrated electrolytes.

Main Results:

• The cyclic voltammetric peaks directly correlated with increased discharge capacity, indicating the presence of polysulfide species.
• Strategies such as adding metal sulfides to the cathode and ceramic coatings on the separator were shown to reduce polysulfide concentrations.
• Highly concentrated electrolytes demonstrated no detectable dissolved polysulfide species, suggesting a promising avenue for future research.

Conclusions:

• The developed in situ electrochemical method provides a valuable tool for real-time monitoring of polysulfide content in Li/S batteries.
• This method can effectively quantify the performance of polysulfide-sequestering strategies.
• Future advancements in Li/S battery technology can leverage this technique to accelerate the development of durable and high-performance energy storage systems.