Highly Solvating Electrolytes for Lithium-Sulfur Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries face challenges with low sulfur utilization at high sulfur loadings and minimal electrolyte.
• Soluble polysulfide intermediates significantly impact Li-S battery discharge mechanisms and overall performance.
• Understanding polysulfide behavior is key to optimizing Li-S battery energy density.

Purpose of the Study:

• To investigate high donor number (DN) electrolytes for enhanced polysulfide dissolution in Li-S batteries.
• To determine the necessity of increased polysulfide dissolution for sulfur utilization under practical conditions.
• To evaluate solvent effects on polysulfide speciation and stability.

Main Methods:

• Comparative analysis of electrolyte co-solvents (dimethylacetamide, dimethyl sulfoxide, 1-methylimidazole vs. dimethoxyethane).
• Electrochemical and chemical characterization of polysulfide species in Li-S cells.
• Investigation of electrolyte stability with lithium metal and polysulfides.

Main Results:

• High DN solvents facilitate increased polysulfide dissolution, which is beneficial for sulfur utilization.
• Polysulfide speciation, particularly the S3•− radical anion, varies significantly with concentration and solvent.
• Instability issues were identified in conventional and high DN solvents with lithium metal and polysulfides.

Conclusions:

• Increased polysulfide dissolution via high DN electrolytes is essential for high sulfur utilization in lean electrolyte Li-S batteries.
• Rational electrolyte design requires considering polysulfide speciation and solvent stability.
• This work provides a foundation for developing optimal electrolytes for high energy density Li-S batteries.