Increasing demand for lighter and more powerful batteries has driven research into alternative technologies. One system that has received significant attention is Lithium-Oxygen. This system exploits the reduction of oxygen to lithium peroxide, by lithium metal, to provide a theoretical specific energy of 3500 Wh kg^-1. One of the major problems facing the Lithium-Oxygen battery is the passivation of the air electrode caused by insoluble lithium oxides and lithium carbonate formed during cycling. These products are not completely oxidized during the charge  step and therefore accumulate within the electrode causing the capacity to fade with each cycle¹.

This work focuses on identifying solution based catalysts in non-aqueous electrolytes to facilitate the oxidation of these insoluble products². The catalysts are oxidized at a higher potential than the lithium peroxide but undergo much faster electron transfer. Once oxidized the catalyst is able to oxidize any lithium peroxide or lithium carbonate remaining on the surface, unblocking the pores and therefore preserving the capacity over subsequent cycles. Analysis of the carbon electrode by x-ray diffraction is able to confirm Li₂O₂ as the discharge product. While the evolution and consumption of oxygen during cycling has been studied using on-line mass spectrometry. The figure included displays cyclic voltammograms of oxygen reduction and evolution with (black) and without (red) a catalyst. This demonstrates that that incorporation of such a catalyst can significantly reduce electrode passivation and therefore dramatically improve the cycle life of the cell. 

[1] Garcia-Araez, N.; Novák, P. Critical Aspects in the Development of Lithium–air Batteries. J. Solid State Electrochem. 2013, 17, 1793–1807.

[2] Lacey, M. J.; Frith, J. T.; Owen, J. R. A Redox Shuttle to Facilitate Oxygen Reduction in the Lithium Air Battery. Electrochem. commun. 2013, 26, 74–76.

Fig. 1. Cyclic voltammogram of oxygen reduction and evolution at 50mV s^-1. Cell consisted of a two electrodes; a glassy carbon working electrode (3mm) and Lithium foil counter/ reference electrode.