This article summarizes our research on aqueous lithium-air rechargeable batteries. Lithium-air batteries have a far higher energy density and lower material cost than lithium-ion batteries, so that they are now attracting growing attention as possible power sources for electric vehicles. Presently, two types of rechargeable lithium-air batteries have been developed; non-aqueous and aqueous types. The aqueous type has a lower specific energy density than the non-aqueous system, but overcomes some severe problems that must still be addressed for the non-aqueous type, such as lithium metal corrosion by water from air and the high polarization of electrode reactions. The key component of the aqueous lithium-air battery is a water-stable lithium metal electrode (WSLE). The WSLE developed in our laboratory consists of lithium metal covered with a lithium conducting polymer electrolyte and a lithium conducting water-stable solid electrolyte, which was successfully operated in a saturated LiOH and LiCl aqueous solution.