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Stable artificial solid electrolyte interfaces for lithium batteries

A rechargeable lithium metal battery (LMB), which uses metallic lithium at the anode, is among the most promising technologies for next generation electrochemical energy storage devices due to its high energy density, particularly when Li is paired with energetic conversion cathodes such as sulfur, oxygen/air, and carbon dioxide. Practical LMBs in any of these designs remain elusive due to multiple stubborn problems, including parasitic reactions of Li metal with liquid electrolytes, unstable/dendritic electrodeposition at the anode during cell recharge, and chemical reaction of dissolved cathode conversion products with the Li anode. The solid electrolyte interface (SEI) formed between lithium metal and liquid electrolytes plays a critical role in all of these processes. We report on the chemistry and interfacial properties of artificial SEI films created by in-situ reaction of a strong Lewis Acid AlI3 additive, Li metal, and aprotic liquid electrolytes. We find that these SEI films impart exceptional interfacial stability to a Li metal anode. We further show that the improvements come from at least three processes: (i) in-situ formation of Li-Al alloy, (ii) formation of a LiI salt layer on Li, and (iii) creation of a stable polymer thin film on the lithium metal anode.