Growing Li 2 O 2 surfaces on discharge cause electrolyte degradation and capacity loss in Li–O 2 batteries

Journal article

Ether-based solvents have shown promise as the most stable candidates for the electrolyte solution in the Li–O2 battery. However, the yield of Li2O2 after discharge is less than 100%, despite achieving a near-ideal ratio of charge passed to O2 consumed (2e−/O2) for the reduction of O2 to Li2O2. The loss of Li2O2 leads to the observed capacity fade on cycling and is associated with electrolyte degradation. Here we investigate the chemical formation of Li2O2 from superoxide in two commonly used ether solutions, dimethoxyethane and tetraethylene glycol dimethyl ether. The results indicate that it is the freshly growing Li2O2 surface reacting with the electrolyte solution that is the dominant source of Li2O2 loss and electrolyte degradation. Additionally, we quantify common side products from the degradation, including Li2CO3, HCO2Li, CH3CO2Li and H2O, and identify the composition of ethylene oxides formed during the reaction.

Authors: Chau, C; Nimmo, T; Dewar, D; Rees, GJ; Tan, C

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Royal Society of Chemistry
• Journal: EES Batteries
• Publication date: 2025-10-02
• Acceptance date: 2025-09-25
• DOI: 10.1039/d5eb00137d
• EISSN: 3033-4071
• Language: English