Suppression of Unwanted Reactions on the Carbon-Based Air Electrode

Abstract

In the past decade, lithium ion batteries have played a dominant power source for items ranging from portable electronics to hybrid electric vehicles. However, they still do not offer enough energy density to meet the ever-increasing demands of many applications despite extensive research to explore ways to increase their charge-storage capability. As a new energy storage system, Li-air batteries have attracted numerous attentions because they have the potential to provide several times higher capacity than commercial Li-ion cells [1-2]. Li-air batteries have been developed in different types according to the electrolytes employed, such as aqueous, non-aqueous, and hybrid systems. Because of relatively simple configuration and large real capacity, non-aqueous system is most active all Li-air batteries. Much research effort has been devoted in order to enhance the performance of Non-aqueous Li-air cells [3-4]. However, they still are facing fundamental and practical challenges such as low rate capability, limited cycle life resulting from the instability of the electrode and electrolyte, and significant overpotential on charge due to slow kinetics of dissociation from reaction products (such as Li2O2). These critical issues are highly attributed to the air electrode, the reaction place between lithium ion and oxygen, and electrolyte directly contact with electrode. In this study, the suppression of unwanted reactions on the air electrode during cycling is main issue. With aim to suppress the unwanted reactions, the surface of carbon was passivated by stable materials. The surface defects of carbon facilitate unwanted electrolyte decomposition reactions during cycling, which deteriorate the cyclic performance of air cell [5-6]. So the passivation of carbon is expected as an effective approach for enhancing the cycling performance of the Li-air batteries.