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

Abstract

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.