Enhanced Cathode Reactions of the Solid-State Li-Air Battery By Operating Under Humidified Atmosphere

Abstract

Lithium-air (Li-air) battery has been considered to be a promising next-generation energy storage system owing to its high theoretical specific energy of 3,458 Wh/kg. Despite the progresses that have been made to improve the cell performance and reaction kinetics of Li-air battery, achieving its sustained reversibility still remains as a highly challenging goal because of the use of liquid electrolyte and carbonaceous materials in the cathode. These components could easily decompose by side reactions against highly oxidative radicals during cycling, leading to a poor cycle life of the cell. To address this instability issue, stable all-solid-state cathode has attracted research attention in accordance with the recent development of oxide-based solid electrolytes. Although a few meaningful approaches to demonstrate oxide-based solid-state cathodes have been reported, such cells were operated under pure oxygen atmosphere (Li-O2 battery), resulting in limited active interfaces for oxygen redox reactions and low specific capacity to the total weight of the cathode structure. Herein, we report the enhanced cathode reactions for Li-air battery by operating under humidified oxygen atmosphere to overcome the limitation of conventional oxide-based solid-state Li-O2 battery. For the cathode, a novel solid-state composite cathode structure consists of ruthenium-based oxide nanoparticles without any carbonaceous additives was prepared to catalyze the oxygen redox reactions. During cycling, the vaporized water molecules could significantly increase the discharge potential, discharge rates, and round-trip efficiency of the cathode. The morphological and structural analysis of the discharge products formed via water-involved reactions inside the pore structure, not only at the interfaces, were also conducted to figure out the effects of humidification. The resulting solid-state Li-air battery showed a superior cycle life with the high specific capacity to the cathode compared to conventional solid-state Li-O2 batteries. The details of the cathode properties and cell performances will be discussed in the presentation.