Interaction Mechanisms between Lithium Polysulfides/Sulfide and Small Organic Molecules

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Lithium polysulfides (LiPSs) are critical components in secondary lithium batteries, influencing battery performance.
• Understanding the interactions between LiPSs and functional groups is key to improving lithium-sulfur battery technology.

Purpose of the Study:

• To elucidate the binding mechanism of lithium polysulfides/sulfide with functional groups at the electronic level.
• To identify effective strategies for constraining LiPSs in lithium-sulfur battery systems.

Main Methods:

• Employed density functional theory (DFT) computational methods.
• Examined proton transfer, polysulfide orientation, electron affinity, and acid dissociation constants of organic molecules.
• Investigated binding energetics influenced by electrostatic attractions, functional group characteristics, and entropy contributions.

Main Results:

• Carboxyl groups effectively dissolve low-order polysulfides through proton transfer but are unstable.
• 1,2-diaminopropane with adjacent amino groups strongly anchors high-order polysulfides.
• Binding energetics are dominated by electrostatic interactions, functional group properties, and their spatial arrangement.

Conclusions:

• The study provides insights into the electronic-level interactions governing LiPSs binding.
• Findings can guide the selection of co-solvents for electrolytes and functional groups for cathode modification in lithium-sulfur batteries.
• Consideration of entropy contributions is important for accurate binding energy assessment.