On discharge, Li+ from the electrolyte and e- from the external circuit combine with O2 from the air, the process is reversible. We have demonstrated evolution of O2 on charging. Capacities as high as 855 mAhg-1 (based on the total mass of the cathode plus the additional mass of O2) have been achieved and values of 1220 mAhg-1 are, in principle, possible.
||Several experiments have been carried out to demonstrate the electrochemical decomposition of Li2O2. Powder X–ray diffraction data were collected on porous composite electrodes before and after discharging where sufficient charge was extracted to decompose fully all of the Li2O2 formed on the previous discharge. We have also successfully confirmed these results by the use of in situ mass spectroscopy showing the release of O2 due to decomposition of the Li2O2.
Differential Electrochemical Mass Spectroscopy
From:   Ogasawara T, Débart A, Holzapfel M, Novák P, Bruce PG. "Rechargeable Li2O2 Electrode for Lithium Batteries".
J. Am. Chem. Soc. 128(4): 1390-1393 2006
||In situ mass spectroscopy during electrochemical cycling.
We have explored the influence of catalyst type, investigating a range of oxygen catalysts including a variety of transition metal oxides; Fe2O3, Fe3O4, CuO, Co3O4 and CoFe2O4. The catalyst type not only influences overall capacity but also has a key role in determining the potential required to drive the reverse reaction and recharge the cell.
From:   Débart A, Paterson AJ, Bao J, Bruce PG, "Alpha-MnO2 Nanowires: A Catalyst For The O2 Electrode in Rechargeable Lithium Batteries".
Angew. Chem. Int. Ed. in press