Rechargeable aqueous lithium-air batteries with an auxiliary electrode for the oxygen evolution

A rechargeable aqueous lithium-air cell with a third auxiliary electrode for the oxygen evolution reaction was developed. The cell consists of a lithium metal anode, a lithium conducting solid electrolyte of Li1+x+yAlx(Ti,Ge)2−xSiyP3−yO12, a carbon black oxygen reduction air electrode, a RuO2 oxygen evolution electrode, and a saturated aqueous solution of LiOH with 10 M LiCl. The cell was successfully operated for several cycles at 0.64 mA cm−2 and 25 °C under air, where the capacity of air electrode was 2000 mAh gcathod−1. The cell performance was degraded gradually by cycling under open air. The degradation was reduced under CO2-free air and pure oxygen. The specific energy density was calculated to be 810 Wh kg−1 from the weight of water, lithium, oxygen, and carbon in the air electrode.