A Pyridine Mediator Enables High-Efficiency, Long-Cycling Anode-Less/Free Lithium-Sulfur Batteries With Li₂S Cathodes

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Lithium sulfide (Li2S) is a high-capacity cathode material ideal for anode-less/free batteries due to its inherent lithium source.
• However, Li2S faces challenges including poor conductivity, high polarization, low utilization, and the shuttle effect, limiting battery lifespan.
• These issues hinder the practical application of Li2S in high-energy-density batteries.

Purpose of the Study:

• To introduce lithium pyridine-2-thiolate (PySLi) as a multifunctional mediator for Li2S-based anode-less/free batteries.
• To investigate PySLi's ability to enhance the electrochemical kinetics and stability of Li2S.
• To evaluate the performance improvements in terms of energy efficiency, cycling stability, and coulombic efficiency.

Main Methods:

• Electrochemical testing of Li||Li2S cells with and without PySLi mediator.
• Analysis of reaction pathways and redox kinetics of Li2S.
• Long-term cycling and stability tests of lithium metal anodes and anode-free/anode-less battery configurations.

Main Results:

• PySLi significantly enhances the electrochemical redox kinetics and stability of Li2S.
• Energy efficiency in Li||Li2S cells with PySLi stabilized at ~80% across various rates (0.1-3 C), outperforming cells without the mediator (22-49%).
• Improved lithium metal anode stability with >98% coulombic efficiency for 200 cycles and stable plating/stripping for 1000 hours.

Conclusions:

• Lithium pyridine-2-thiolate (PySLi) effectively mediates Li2S, overcoming its limitations in anode-less/free battery systems.
• The study demonstrates a new strategy for utilizing Li2S in high-energy-density, stable anode-less/free batteries.
• PySLi offers a promising pathway for advancing next-generation lithium battery technology.