Balancing Anodic Stability and Cathodic Kinetics in Practical Lithium-Sulfur Batteries With Non-fluorinated Weakly...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries offer high theoretical energy density but face challenges with Li-metal anode stability and sulfur cathode kinetics.
• Polysulfide shuttling and the formation of inactive species degrade Li-S battery performance and lifespan.

Purpose of the Study:

• To develop a weakly solvating electrolyte (WSE) that simultaneously improves Li-metal anode stability and sulfur cathode conversion kinetics in Li-S batteries.
• To investigate the mechanisms by which the WSE suppresses polysulfide shuttling and enhances interfacial stability.

Main Methods:

• A WSE was formulated using 1 M lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) in cyclopentyl methyl ether (CPME) with a 1,3-dioxolane (DOL) additive.
• The WSE's effect on Li-metal anode stability was assessed by analyzing the solid electrolyte interphase (SEI) formation.
• Cathode performance was evaluated by examining the cathode electrolyte interphase (CEI) and conversion kinetics of sulfur-carbon (S/C) composites.

Main Results:

• The WSE effectively suppressed lithium polysulfide (LiPSs) shuttling by forming an anion-dominated Li+ solvation structure, leading to a stable SEI on the Li-metal anode.
• The DOL additive facilitated a hybrid CEI, maintaining cathode conversion kinetics and preventing dead Li2S accumulation.
• Li-S batteries with WSE achieved a high initial capacity (≈1208 mAh g-1), 98.6% average Coulombic efficiency, and 82.4% capacity retention over 200 cycles.
• Stable cycling over 100 cycles was demonstrated in a Li-S pouch cell under demanding conditions.

Conclusions:

• The developed WSE offers a promising strategy for simultaneously addressing anodic and cathodic challenges in Li-S batteries.
• This electrolyte design enhances Li-S battery performance, enabling stable and efficient energy storage.
• The findings pave the way for practical applications of high-energy Li-S batteries.