Vehicle drivetrain electrification is one of the many future challenges that automakers face. While there are many different EV system configurations, the one constant is the need for better electrochemical storage. Initially, this paper will discuss existing electrochemical systems and their potential to meet future vehicle requirements. We will then examine beyond Li-ion systems and their potential to replace current technology. Lithium-O2 batteries form lithium peroxide (Li2O2). This product formed on the electrocatalyst happens to be a wide band-gap semiconductor/insulator. This has ramifications for discharge, charge, and battery design. During discharge, the poor electronic conductivity of Li2O2 limits the amount and rate at which product can be formed. Under a constant discharge, the resistance of the electrode increases, causing a voltage drop that becomes sufficiently large and stops any further reaction. On charge, the decomposition of the product is inhibited by the resistance of the product; higher resistances require higher voltages. The implication for battery design is that electrocatalyst surface area becomes the controlling factor to achieve reversibility which increases battery volume. Product conductivity is fundamental to this system and can be marginally controlled by electrocatalyst selection. For an air battery’s maximum capacity, it requires a maximum amount of an insoluble non-conductive product. These are counterproductive. We show many variables such as the chemical composition, electrocatalyst surface structure, rate of electrochemical discharge, and depth of that discharge affect the morphology, shape and type of product. We also show that the nature of the solvent in the electrolyte solution also plays a role. We show this through multi-scan cyclic voltametry in combination with in-situ electrochemical scanning probe microscopy. With this analysis, it will be shown that the while the product conductivity may be variable, it is not the controlling mechanism, especially in the high power applications required for an automotive application.

Understanding the surface reactions of the lithium-air battery and its consideration for usage in an automotive application

253rd National Meeting (2017)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.