Deciphering the role of LiBr as redox mediator in Li-O2 Aprotic Batteries

TL;DR

This paper investigates how different solvents influence the performance and stability of LiBr as a redox mediator in lithium-oxygen batteries, revealing solvent-specific reaction pathways and stability issues.

Contribution

It provides new insights into solvent effects on LiBr-mediated Li-O2 batteries, identifying solvent-dependent reaction mechanisms and stability considerations.

Findings

Singlet oxygen evolution occurs only in TEGDME electrolyte.

DME and DMSO enable singlet oxygen-free oxygen evolution.

DME remains chemically stable under working conditions.

Abstract

Lithium-oxygen batteries are among the most promising energy storage systems due to their high theoretical energy density, but their practical implementation is hindered by poor reversibility and parasitic reactions. Redox mediators such as LiBr have emerged as a strategy to enhance reaction kinetics and reduce overpotentials. In this study, we explore the impact of three different solvents, dimethoxyethane (DME), tetraethylene glycol dimethyl ether (TEGDME), and dimethyl sulfoxide (DMSO), on the electrochemical performance and reaction pathways of LiBr-mediated Li-O2 cells. Our results reveal that a 1O2 evolution channel that leads to singlet oxygen-induced cell degradation is active only in the TEGDME-based electrolyte. Both DME and DMSO allow singlet oxygen-free Oxygen Evolution Reaction, but only DME is found chemically stable in the LiBr-mediated Li-O2 cell working conditions. These findings highlight the critical role of solvent-mediator interactions in determining the performance of Li-O2 cells.