Interfacial Electrochemical Lithiation and Dissolution Mechanisms at a Sulfurized Polyacrylonitrile Cathode Surface

Area of Science:

• Materials Science
• Electrochemistry
• Computational Chemistry

Background:

• Sulfurized-polyacrylonitrile (SPAN) is a promising cathode material for safer, more efficient lithium-sulfur (Li-S) batteries.
• Understanding electrolyte-cathode interactions is key to optimizing Li-S battery performance and preventing polysulfide dissolution.

Purpose of the Study:

• To investigate the electrolyte-cathode interfacial electrochemistry and polysulfide dissolution in Li-S batteries with SPAN cathodes.
• To elucidate the role of lithium bis(fluorosulfonyl)imide (LiFSI) in Li-SPAN cell electrochemistry and cathode-electrolyte interphase (CEI) formation.

Main Methods:

• Ab initio molecular dynamics (AIMD) simulations to emulate SPAN discharge reactions.
• Density functional theory (DFT) and spectroscopy (Raman/IR, X-ray photoelectron spectroscopy) for cross-validation of structures and lithiation profiles.

Main Results:

• LiFSI is identified as a primary source for CEI formation and mediates polysulfide generation during SPAN lithiation.
• Ether solvents demonstrate superior solvation and stabilization of LiFSI and SPAN structures compared to carbonate solvents.
• Distinct CEI formation and electrochemical lithiation pathways are linked to the specific lithium bonding characteristics with oxygen and sulfur.

Conclusions:

• LiFSI plays a multifaceted role in Li-SPAN batteries, influencing CEI composition and polysulfide dynamics.
• Solvent choice significantly impacts electrolyte stability and interfacial behavior, with ethers offering advantages over carbonates.
• The study provides fundamental insights into the interfacial mechanisms governing Li-S battery performance with SPAN cathodes.