(583ey) Mechanistic Insights On the Electrochemistry At the Lithium-Air Cathodes

Nonaqueous lithium-air batteries are promising electrochemical storage devises with very high theoretical specific capacity and energy density. Li-air batteries are comprised of an anode (pure metallic lithium), an air electrode (cathode, commonly composed of porous structure, mainly carbon), and an aprotic electrolyte. The chemistry at the cathode is fairly complex and plays an important role in the performance of the Li-air batteries. The cathode of Li-air batteries needs to facilitate (i) the transport of Li⁺ throughout the electrode in order to enable the formation of Li₂O₂ (ii) the electrochemical reactions (oxygen reduction reaction (ORR) and oxygen evolution reaction (OER)) with low overpotential losses, (iii) the storage of Li₂O₂ in the porous media to achieve high capacity, and (iv) conduction of electrons with high efficiency. We have employed in-situ infrared spectroscopy in combination with electrochemical methods and electron microscopy to determine the chemical/electrochemical transformations that govern the electrochemistry at the carbon-based Li-air cathodes. We have been able to determine the effect of cathode composition (i.e. architecture, the addition of an electrocatalyst and electrolyte layer) on the chemistry during the charge/discharge cycles. These studies have led to insights on improving the efficiency and stability of carbon-based Li-air cathodes.