The Origin of Improved Cycle Stability of Li-O2 Batteries Using High-Concentration Electrolytes

The intrinsic instability of organic electrolytes seriously impedes practical applications of lithium–oxygen (Li-O2) batteries. Recent studies have shown that the use of high-concentration electrolytes can suppress the decomposition reaction of electrolytes and help enhance cell reversibility. However, the fundamental nature of concentrated electrolytes’ ability to improve the chemical durability and stability of Li-O2 batteries remains unclear. In this work, we conducted computational studies to elucidate the origin of the enhanced oxidative/reductive stability of three representative solvents—DMSO, DME, and EC—in high-concentration electrolytes. The modeling results identify that Li+-solvent complexes, one of the solvate components, are the easiest to decompose in concentrated electrolytes. Thermodynamic and kinetic characterizations reveal that more anions in concentrated electrolytes are responsible for improving the oxidative and reductive stability of electrolytes. In addition, more Li+ ions, acting as a scavenging or stabilizing agent for superoxide anion (O2−), also improve the stability of electrolytes against oxidation in Li-O2 batteries. This work provides a mechanistic understanding of the enhanced cycle stability of a Li-O2 battery using high-concentration electrolytes.