Salt Concentration Control of Polysulfide Dissolution, Diffusion, and Reactions in Lithium-Sulfur Battery...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries face challenges from polysulfide (PS) dissolution, impacting performance and lifespan.
• Understanding PS dissolution and migration mechanisms, especially under varying states of charge (SOC), is crucial for Li-S battery improvement.

Purpose of the Study:

• To investigate the impact of high electrolyte salt concentrations on polysulfide solubility and transport in Li-S batteries.
• To elucidate the behavior of long- and short-chain polysulfides and trisulfur radicals under different salt concentrations.

Main Methods:

• Utilized *operando* Raman spectroscopy to monitor polysulfide species in real-time.
• Examined a wide range of LiTFSI concentrations (0.3-7.0 m) in DME:DOL (1:1, v/v) electrolyte.

Main Results:

• Increased electrolyte salt concentration reduced the solubility and slowed the transport of both PS dianions (S_4-8 ^2-) and trisulfur radicals (S₃ ^•-) at the lithium anode.
• The concentration of S₃ ^•- decreased more significantly than S₆ ^2-, suggesting inhibited radical formation in concentrated electrolytes.
• Observed shifts in local solvation structure due to high salt concentration control PS behavior.

Conclusions:

• High electrolyte salt concentrations effectively mitigate polysulfide dissolution and migration in Li-S batteries.
• Understanding the influence of solvation structure on polysulfide dynamics is key to enhancing Li-S battery performance.
• This research provides critical mechanistic insights for designing advanced Li-S battery electrolytes.