Self-assembled monolayers direct a LiF-rich interphase toward long-life lithium metal batteries

High–energy density lithium (Li) metal batteries (LMBs) are promising for energy storage applications but suffer from uncontrollable electrolyte degradation and the consequently formed unstable solid-electrolyte interphase (SEI). In this study, we designed self-assembled monolayers (SAMs) with high-density and long-range–ordered polar carboxyl groups linked to an aluminum oxide–coated separator to provide strong dipole moments, thus offering excess electrons to accelerate the degradation dynamics of carbon-fluorine bond cleavage in Li bis(trifluoromethanesulfonyl)imide. Hence, an SEI with enriched lithium fluoride (LiF) nanocrystals is generated, facilitating rapid Li+ transfer and suppressing dendritic Li growth. In particular, the SAMs endow the full cells with substantially enhanced cyclability under high cathode loading, limited Li excess, and lean electrolyte conditions. As such, our work extends the long-established SAMs technology into a platform to control electrolyte degradation and SEI formation toward LMBs with ultralong life spans. Description SAM to the rescue During cycling of lithium metal batteries, the formation of dendrites on the electrodes can cause failure of the battery over time. Liu et al. were able to enhance lithium stripping and plating using self-assembled monolayers (SAMs) containing carboxylic groups. The SAMs are deposited on the aluminum oxide–coated polypropylene separator and promote the formation of a lithium fluoride–rich solid electrolyte interphase that shows greater overall stability and enhanced lithium ion transport. —MSL Self-assembled monolayers help build a LiF-rich solid electrolyte interphase for a long-life-span Li metal anode.