In Situ Spectroscopic Studies of the Electrochemistry of Dioxygen in Non-Aqueous Li-Air Battery Electrolytes

The non-aqueous lithium-oxygen battery is one of a host of emerging opportunities available for enhanced energy storage [1]. Unlike a conventional battery where the reagents are contained within the cell, the lithium-oxygen cell uses dioxygen from the atmosphere to electrochemically form the discharge product lithium peroxide. Degrees of reversible oxidation and formation of lithium peroxide has been demonstrated in a number of non-aqueous electrolyte classes, mostly notably in dimethysulfoxide based electrolytes [2], thus making the lithium-oxygen cell a potential energy storage device. A schematic representation of the rechargeable non-aqueous Li-O₂ cell is shown in the Figure. On discharge, lithium ions formed at the lithium metal anode are transported across the electrolyte and into the pores of the air-cathode. O₂ from the atmosphere enters the cathode, and dissolves into the electrolyte within the pores. It is then reduced at the porous carbon electrode surface by electrons from the external circuit and combines with Li⁺ from the electrolyte, leading to the formation of solid Li₂O₂ as the final discharge product. Surprisingly, the reaction in some electrolytes is fairly reversible, Li₂O₂ can be oxidised, releasing oxygen gas. The challenge for the Li-O₂ cell is the progress of development of the air-cathode that allows highly reversible formation of Li₂O₂ in a stable electrolyte within its pores [3-6]. 

This talk will present our groups recent results of the electrochemistry of dioxygen in non-aqueous electrolytes on planar and single crystal electrodes, of which particular electrolytes could have practical application within a lithium-oxygen cell. Discussion will touch upon how the electrochemistry can be related to electrode substrate and will be presented with in situ spectroscopic studies that identify intermediate and surface species during the oxygen reduction reaction.

1. P.G. Bruce, S. Freunberger, L.J. Hardwick, J.-M. Tarascon, Nature Mater. (2012) 11 19
2. Z. Peng, S.A. Freunberger, Y. Chen, P.G. Bruce, Science, (2012) 337 563
3. S. Freunberger, Y. Chen, N. Drewett, L.J. Hardwick, F. Bardé, P.G. Bruce, Angew. Chem. Int. Ed. (2011) 50 8609
4. S. Freunberger, Y. Chen, Z. Peng, J. Griffin, L.J. Hardwick, F. Bardé, P. Novák, P.G. Bruce, J. Amer. Chem. Soc. (2011) 133 8040
5. Z. Peng, S. Freunberger, L.J. Hardwick, Y. Chen, V. Giordani, F. Bardé, P. Novák, J.-M. Tarascon, D. Graham, P.G. Bruce, Angew. Chem. Int. Ed. (2011) 50 63514
6. M. Leskes, N Drewett, L.J. Hardwick, P.G. Bruce, G.R. Goward, C.P. Grey, Angew. Chem. Int. Ed. (2012) 51 8560