Modulating Li⁺ and Polysulfide Solvation with Low-Density Moderately Solvating Electrolytes for Lithium-Sulfur...

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries offer high theoretical energy density but face challenges like polysulfide shuttling and unstable interfaces.
• The electrolyte is critical for ion transport and sulfur conversion, influencing overall battery performance.

Purpose of the Study:

• To develop a novel electrolyte that addresses polysulfide shuttling and interphasial instability in Li-S batteries.
• To optimize electrolyte properties for enhanced Li-S cell performance, including Li metal stabilization and redox kinetics.

Main Methods:

• Introduction of a moderately solvating electrolyte (MSE) using low-density, low-viscosity, nonfluorinated ether co-solvents.
• Analysis of solvent-solvent and solvent-ion interactions to understand Li+ desolvation and SEI formation.
• Evaluation of MSE performance in high-mass loading Li-S cells at various temperatures and with lean electrolyte content.

Main Results:

• The optimized MSE effectively weakens Li+-solvent pairing and strengthens cation-anion interactions, promoting a stable solid-electrolyte interphase (SEI).
• MSE limits polysulfide dissolution while improving active material accessibility and wettability, altering sulfur deposition mechanisms.
• Stable cycling of high-mass loading Li-S cells (> 3.5 mg cm⁻²) was achieved at room temperature and 45°C, with a pouch cell demonstrating lean electrolyte operation (4.5 µL mg s⁻¹).

Conclusions:

• The developed MSE offers a practical strategy for creating high-performance electrolytes for Li-S batteries.
• The study provides valuable mechanistic insights into the operation of Li-S cells with tailored electrolyte compositions.
• MSE demonstrates significant potential for advancing the commercial viability of Li-S battery technology.