In situ AFM Observations of Li-Oxygen Electrochemical Reactions

Abstract: The morphologies of crystalline lithium peroxide (Li2O2) discharge products in Li-O2 batteries have been shown to exhibit a dependency on subtle variations within the battery cell-operating environment including exposure to ambient air, moisture, or additives. As a result, imaging battery discharge products in real time under carefully controlled environmental conditions is a challenging obstacle for complete mechanistic understanding of Li2O2 growth and deposition during discharge in metal-air batteries. Here, we report the design of a completely enclosed cell for high-resolution in situ AFM imaging of Li-O2 battery discharge products. The air-and moisture-free electrochemical cell environment enabled the observation of different product morphologies during AFM imaging when LiTFSI in oxygen-saturated tetraethylene glycol dimethyl ether (tetraglyme) solvent was employed. This in situ AFM cell development brings complimentary information to various proposed mechanisms for lithium oxygen reaction.