Increasing round trip efficiency of hybrid Li–air battery with bifunctional catalysts

Previously it was shown that Pt as cathode catalyst has a large overpotential during charge in rechargeable hybrid Li–air battery with sulfuric acid catholyte. This article demonstrates that a bifunctional catalyst composed of Pt and IrO2 supported on carbon nanotubes can address this problem. The specially designed and synthesized bifunctional catalyst showed significant overpotential reduction and achieved a round trip energy efficiency of 81% after 10 cycles, higher than many achieved in aprotic Li–O2 batteries. The hybrid Li–air battery was discharged and recharged for 20 cycles at 0.2 mA/cm2, showing a fairly stable cell performance. A specific capacity of 306 mAh/g and a specific energy of 1110 Wh/kg were obtained for the hybrid Li–air battery in terms of acid weight.