Revealing In Situ Li Metal Anode Surface Evolution upon Exposure to CO2 Using Ambient Pressure X-Ray Photoelectron Spectroscopy.

Because they deliver outstanding energy density, next-generation lithium metal batteries (LMBs) are essential to the advancement of both electric mobility and portable electronic devices. However, the high reactivity of metallic lithium surfaces leads to the low electrochemical performance of many secondary batteries. Besides, Li deposition is not uniform, which has been attributed to the low ionic conductivity of the anode surface. In particular, lithium exposure to CO2 gas is considered detrimental due to the formation of carbonate on the solid electrolyte interphase (SEI). In this work, we explored the interaction of Li metal with CO2 gas as a function of time using ambient pressure X-ray photoelectron spectroscopy to clarify the reaction pathway and main intermediates involved in the process during which oxalate formation has been detected. Furthermore, when O2 gas is part of the surrounding environment with CO2 gas, the reaction pathway is bypassed to directly promote carbonate as a single product.