Influence of Hydrocarbon and CO2 on the Reversibility of Li–O2 Chemistry Using In Situ Ambient Pressure X-ray Photoelectron Spectroscopy

Abstract

Identifying fundamental barriers that hinder reversible lithium–oxygen (Li–O2) redox reaction is essential for developing efficient and long-lasting rechargeable Li–O2 batteries. Addressing these challenges is being limited by parasitic reactions in the carbon-based O2–electrode with aprotic electrolytes. Understanding the mechanisms of these parasitic reactions is hampered by the complexity that multiple and coupled parasitic reactions involving carbon, electrolytes, and Li–O2 reaction intermediates/products can occur simultaneously. In this work, we employed solid-state cells free of carbon and aprotic electrolytes to probe the influence of surface adventitious hydrocarbons and carbon dioxide (CO2) on the reversibility of the Li–O2 redox chemistry using in situ synchrotron-based ambient pressure X-ray photoelectron spectroscopy. Direct evidence was provided, for the first time, that surface hydrocarbons and CO2 irreversibly react with Li–O2 reaction intermediates/products such as Li2O2 and Li2O, forming...