Modeling Singlet Oxygen-Induced Degradation Pathways Including Environmental Effects of 1,2-Dimethoxyethane in Li-O₂...

Area of Science:

• Computational chemistry
• Materials science
• Electrochemistry

Background:

• Lithium-oxygen (Li-O2) batteries offer high energy density but suffer from electrolyte degradation.
• Parasitic reactions involving singlet oxygen (1O2) and ether-based electrolytes like 1,2-dimethoxyethane (DME) are a key concern.

Purpose of the Study:

• To investigate reaction mechanisms between 1O2 and DME using DFT.
• To understand how the Li-O2 battery environment influences these parasitic reactions.

Main Methods:

• Density functional theory (DFT) calculations.
• Modeling of the electrolyte environment using implicit solvent models, Li+ coordination, and external electric fields.

Main Results:

• Two reaction pathways for 1O2 attack on DME were identified: a single-step C-C bond cleavage and a two-step hydroperoxide formation.
• Reaction initial barriers range from 17-26 kcal mol-1 under relevant battery conditions.
• Barriers decrease with increasing dielectric constant and electric field strength.

Conclusions:

• DFT calculations elucidate key parasitic reaction pathways in Li-O2 batteries.
• The electrolyte environment significantly lowers reaction barriers, promoting degradation.
• Findings provide insights for designing more stable ether-based electrolytes for Li-O2 batteries.