Carbon-Free Bifunctional Cathodes for the use in Lithium - Air Batteries with an Aqueous Alkaline Electrolyte

Carbon materials are widely used in gas diffusion electrodes due to their high electronic conductivity, stability, relatively low costs and catalytic activity towards oxygen reduction reaction (ORR) [1, 2]. During charging a lithium-air battery the cathode is operated in oxygen evolution reaction (OER) mode. Carbon materials corrode in OER mode. This leads to degradation and a power loss of the electrode [3, 4]. To improve long-term stability and reduce side reactions as H2 and CO2 evolution in OER operation mode carbon-free bifunctional cathodes for aqueous alkaline lithium-air batteries were prepared [5 -7]. Gas diffusion electrodes with the combination of silver or nickel modified with Co3O4 show high activity for both reactions ORR and OER and a significant improvement in performance and long-term stability [6, 7]. Gas diffusion electrodes were electrochemically investigated in a half cell. In addition to cyclic voltammograms electrochemical impedance spectroscopy (EIS) [8] was carried out. SEM and XRD were used for the physical and morphological investigations. [1] H. Ohkuma, I. Uechi, M. Matsui, Y. Takeda, O. Yamamoto, N. Imanishi, J. Power Sources 245 (2014) 947 [2] H. Arai, S. Müller, O. Haas, J. Electrochem. Soc. 147 (2000) 3584 [3] P. N. Ross, M. Sattler, J. Electrochem. Soc. 135 (1988) 1464 [4] P. N. Ross, H. Sokol, J. Electrochem. Soc. 131 (1984) 1742 [5] D. Wittmaier, T. Danner, N. Wagner, K. A. Friedrich, J. App. Electrochem. 43 (2013) 73 [6] D. Wittmaier, N. Wagner, K. A. Friedrich, H.A. Amin, H. Baltruschat, J. Power Sources 265 (2014) 299 [7] D.Wittmaier, S. Aisenbrey, N. Wagner, K.A.Friedrich, Electrochim. Acta, Accepted Paper (2014) [8] N. Wagner, “Electrochemical power sources – Fuel cells” in Impedance Spectroscopy: Theory, Experiment and Applications”, 2nd Edition, Edited by Evgenij Barsoukov and J. Ross Macdonald, John Wiley&Sons, Inc., ISBN: 0-471-64749-7, pp.497-537, 200