Mie University, Japan
Lithium-air secondary batteries with a lithium metal anode and an air cathode are an attractive energy storage system because they have high theoretical energy density. Two types of lithium-air batteries have been developed, namely, non-aqueous and aqueous types. We have studied aqueous type of lithium-air batteries, which consist of a lithium electrode, an aqueous electrolyte with LiCl, and an air electrode. A protected lithium electrode, Li/PEO18LiTFSI/Li1+xTi2-xAlx(PO4)3 was stable in a saturated LiOH with 10 M LiCl aqueous electrolyte, which showed a pH value of ca. 9.
In this study, applicability of air electrodes in this moderately alkaline aqueous solution were examined. Carbon electrodes with perovskite-type oxide catalysts were used as air electrodes. The catalytic activity for oxygen reduction and evolution, and chemical, electrochemical stabilities were evaluated for these perovskites. Various carbon materials are studied for the long term polarization in the LiOH-LiCl electrolyte. The effect of ion exchange membranes is also investigated which are applied to avoid direct deposition of solid LiOH on the air electrode.