Reactivity, stability and selectivity of Li-O2 interfaces . Nenad Markovic Materials Science Division, Argonne National Laboratory, Lemont, IL-60439   The Li-O2battery is generating a great deal of interest because theoretically it possesses a specific energy 5-10 times that of a conventional Li-ion battery. Very little is known about the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) in lithium-air battery cathodes based on aprotic organic electrolytes. A systematic study using both traditional RDE measurements as well as cell level measurements in conjunction with various characterization techniques will be presented. We begin by drawing analogies between the oxygen electrode reactions in the aqueous electrolyte, in particular alkaline electrolyte, and the aprotic (Li+ free) non-aqueous electrolytes. Employing extended surfaces of Au we will demonstrate that the ORR in these electrolytes is governed by the same principles that dictate the reaction mechanisms in protic solvents. We will also employ R(R)DE techniques to both quantitatively and qualitatively determine the reaction products namely the superoxide and peroxide. This will be used to determine the stability of the various ethers and carbonate solvents toward the superoxide species. Extending this study to Li+ based solvents will be used to further determine the products formed, their stability, their strength of adsorption to the electrode surface, and the measure of reversibilities achieved using RDE measurements. Furthermore, using an electrochemical voltammetric finger printing technique, we will aim to understand the nature of products formed in the presence of Li+ cations and the ease of their re-chargeability. Extending this approach to study carbonaceous materials will help us better delineate the role of morphology, nature of carbon and the relative geometry effects on observed reversibility of Li-O¬2 cathode interfaces. A careful study on the role of surface active groups and their impact on both the reduction and oxidation reactions will be studied both in a traditional three-electrode setup as well as our in-house design battery cell design (KF cell). The presence of side reactions that can occur at the cathode interfaces, particularly related to electrolyte oxidation will be discussed briefly. This will help us to understand the reaction that determines the observed charging plateaus. The KF cell then allows us to both determine the potentials at which gasses are generated/consumed using a pressure-change measurement, which can then in conjunction with DEMS be used to identify the nature of products formed during the charging process. Also, using the “expected products” in the battery directly we determine the expected voltages at which they can be oxidized and correlate them with the real battery charging potentials. This helps us to draw a conclusion regarding the nature of products formed during discharge and the potential charging reactions. < volver