Anode-Free Lithium-Sulfur Cells Enabled by Rationally Tuning Lithium Polysulfide Molecules

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium-sulfur (Li-S) batteries face challenges with lithium-metal anode reversibility and sulfur cathode kinetics.
• These limitations hinder the practical application and long-term stability of Li-S battery technology.

Purpose of the Study:

• To develop a molecular tailoring strategy for lithium polysulfides to overcome key Li-S battery limitations.
• To synergistically enhance both anode reversibility and cathode kinetics in Li-S cells.

Main Methods:

• Utilized tin(IV) iodide (SnI4) to coordinate with lithium polysulfides, forming soluble complexes.
• Investigated the formation of a lithium thiostannate (Li2SnS3)-rich anode interphase layer.
• Evaluated performance in anode-free, lean-electrolyte pouch cells with a lithium sulfide (Li2S) cathode.

Main Results:

• SnI4 coordination created a stable Li2SnS3 anode interphase layer with low ionic resistance, improving Li plating/stripping efficiency.
• Soluble SnI4-polysulfide complexes suppressed polysulfide clustering, enhancing sulfur conversion kinetics under lean electrolyte conditions.
• Achieved 78% capacity retention after 100 cycles in pouch cells, demonstrating synergistic improvements.

Conclusions:

• Molecular tailoring of lithium polysulfides with SnI4 offers a viable strategy to address critical Li-S battery performance bottlenecks.
• The approach effectively improves anode stability and cathode reaction kinetics, paving the way for more practical Li-S batteries.