Advanced Self-Phase-Separating Electrolytes for High-Performance Lithium-Sulfur Batteries.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries offer high theoretical energy density but suffer from poor cycle life due to lithium polysulfide (LiPSs) shuttle and sluggish redox kinetics.
• Optimizing sulfur utilization and anode stability remains a key challenge for practical Li-S battery applications.

Purpose of the Study:

• To design a self-phase-separating electrolyte that simultaneously enhances Li-S battery kinetics and suppresses LiPSs shuttle effects.
• To achieve stable cycling and high energy density in Li-S batteries through spatial electrolyte partitioning.

Main Methods:

• Utilized co-solvents (1,2-dimethoxyethane and cyclopentyl methyl ether) to induce spontaneous electrolyte phase separation based on LiPSs dissolution characteristics.
• Engineered a dual-zone electrolyte system with distinct solvation strengths at the cathode and anode.
• Fabricated and tested single-layer and multi-layer Li-S pouch cells with high sulfur loading and thin lithium anodes.

Main Results:

• The self-phase-separating electrolyte successfully created a strong-solvation region at the cathode for rapid kinetics and a weak-solvation region at the anode for stable solid electrolyte interphase (SEI) formation.
• Achieved stable cycling over 170 cycles in single-layer pouch cells with 4.3 mg$_{s}$ cm$^{-2}$ sulfur loading and 50 µm Li anodes.
• Demonstrated a 1.8 Ah multi-layer pouch cell delivering 323 Wh kg$^{-1}$ energy density with stable cycling over 50 cycles under lean electrolyte conditions.

Conclusions:

• The proposed self-phase-separating electrolyte strategy effectively addresses the trade-off between sulfur redox kinetics and anode interfacial stability in Li-S batteries.
• This dual-zone synergistic mechanism offers a promising pathway for developing high-performance and long-lasting metal-sulfur batteries.
• The findings provide a viable solution for enhancing the practical applicability of lithium-sulfur battery technology.