2LB-6 : Stability and cycle performance of nonaqueous electrolytes in lithium air battery

Lithium air batteries have now received increasing attention owing to the much higher theoretical energy density than the current state-ofthe- art lithium ion technology. Hence, lithium air batteries are considered as possible power sources for the next generation range-anxiety-free electric vehicles. However, recent tremendous research activities clearly revealed that there are many issues to be overcome such as high charge overpotential, fast capacity fading, low oxygen efficiency, etc. Since these critical problems are closely related with the nature of the used electrolytes, identification of stable electrolytes is the most important task for true rechargeable lithium air battery. Li-air battery is typically composed of lithium metal anode, organic solvent dissolved with lithium salt, and porous carbon cathode. During operation in the discharge and charge cycle, the reactive superoxide ion and lithium peroxide may attack the susceptible organic electrolyte, yielding several by-products such as lithium carbonate, lithium carboxylate, and lithium alkyl carboxylates. The side-products caused evolution of carbon dioxide and hydrogen rather than oxygen in charge as well as loss of capacity and cell failure. Many research groups all around world have tried to develop a stable electrolyte to suppress the side reaction and hence to enhance cycle performance in the cell. In the early stage, the carbonates such as propylene carbonate were used for the electrolytes. In-situ DEMS analysis and other spectroscopic tools have elucidated that the carbonates are susceptible to the nucleophilic attack by superoxide ion and are unsuitable for lithium air battery. After that, attention was shifted to many other solvents. Among them, so far ether-based solvents including TEGDME and DME, amide-based solvent such as DMA, and sulfoxide solvents such as DMSO are considered relatively stable against the harsh environment in lithium air battery operation. Our group also makes intense effort to develop desirable electrolytes by means of in-situ quantitative DEMS as well as other analytical instruments. In this talk, I will present and discuss the current research state on stability and cycle performance of the lithium air battery electrolytes.