Visualizing interfacial collective reaction behaviour of Li-S batteries

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Lithium-sulfur (Li-S) batteries offer high energy density and low cost, making them promising for energy storage.
• The shuttle effect of lithium polysulfides and interfacial reaction mechanisms remain poorly understood due to characterization limitations.
• Understanding dynamic polysulfide behavior is critical for advancing Li-S battery technology.

Purpose of the Study:

• To directly visualize and understand the nanoscale interfacial reactions of lithium polysulfides in Li-S batteries.
• To elucidate the dynamic transformation, aggregation, deposition, and dissolution of lithium polysulfides at high temporal-spatial resolution.
• To investigate the role of active sites in mediating polysulfide conversion pathways.

Main Methods:

• In situ liquid-cell electrochemical transmission electron microscopy (LCE-TEM) for atomic-scale visualization.
• Molecular dynamics (MD) simulations to investigate electrostatic interactions and phase formation.
• Ab initio molecular dynamics (AIMD) simulations to verify collective charge transfer.

Main Results:

• Direct visualization of lithium polysulfide transformation on electrode surfaces at the atomic scale.
• Discovery of an unexpected gathering-induced collective charge transfer on active-centre-immobilized surfaces.
• Observation of instantaneous deposition of non-equilibrium Li2S nanocrystals from a dense polysulfide liquid phase.
• Identification of distinct reaction pathways: collective charge transfer on active sites versus step-by-step conversion on inactive surfaces.

Conclusions:

• A novel collective interfacial reaction pathway for lithium polysulfides has been unveiled.
• The findings deepen the fundamental understanding of reaction mechanisms within Li-S batteries.
• This research provides new insights into controlling polysulfide behavior for improved Li-S battery performance.