Cosolvent Electrolyte Design for Li-S Batteries: Suppressing the Shuttle Effect via Phase Separation

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries offer high energy density and low cost, making them attractive for next-generation energy storage.
• Commercialization is limited by the polysulfide shuttle effect, leading to poor cycling performance.
• Existing solutions often involve inactive additives, which reduce overall energy density.

Purpose of the Study:

• To present a fundamental strategy for suppressing the polysulfide shuttle effect in Li-S batteries.
• To design a cosolvent-based electrolyte that avoids inactive additives.
• To investigate the influence of solvent miscibility on polysulfide transport and electrochemical performance.

Main Methods:

• A high donor number solvent was used as the base electrolyte.
• Four cosolvents with varying physicochemical properties were systematically introduced.
• The solubility of lithium polysulfides was tuned by adjusting the cosolvent composition.
• Local phase separation was induced by combining low-miscibility solvents.

Main Results:

• Tuning cosolvent composition allowed systematic control over lithium polysulfide solubility and electrochemical kinetics.
• Local phase separation in low-miscibility solvent mixtures effectively hindered polysulfide diffusion.
• The cosolvent-based electrolyte significantly mitigated the shuttle effect.
• Substantially improved cycling stability was achieved in the Li-S batteries.

Conclusions:

• Cosolvent-based electrolyte design is a viable fundamental strategy to enhance Li-S battery performance.
• Avoiding inactive additives is crucial for maintaining high energy density.
• Solvent miscibility plays a critical role in controlling polysulfide transport and suppressing the shuttle effect.
• This approach offers a promising new direction for developing advanced Li-S battery electrolytes.