Stable Solid Electrolyte Interphase Formation Induced by Monoquat-Based Anchoring in Lithium Metal Batteries

The lithium (Li) metal anode is considered to be a promising candidate for next-generation batteries but is impeded by Li dendrites and the resulting poor reversibility. Here, we introduce monoquat salts with an ability to anchor onto the Li metal surface through pyridine moieties as electrolyte additives. We systematically varied both the number and the spatial arrangement of anchoring units along with the number of positive charges bearing PF6 counteranions to probe their impact on Li metal protection. A high surface concentration of PF6 counteranions and their immediate reaction with the deposited Li facilitate the in situ formation and homogeneous distribution of LiF in the surface passivation layer. Our results revealed that the monoquat dication, through stable pyridine-based anchoring, formed an ionically conductive and dense solid electrolyte interphase layer and showed superior cycling performance in both ether-based and carbonate-based electrolytes, thus clearly demonstrating the importance of the anchoring strategy for Li metal surface protection.