Lithium Deposition from a Piperidinium–based Ionic Liquid: Rapping Dendrites on the Knuckles

Abstract

AbstractUsing cyclic voltammetry (CV), in‐situ scanning tunneling microscopy (STM) and electrochemical quartz crystal microbalance (EQCM) the initial stages of lithium deposition on Au(111) from a solution of lithium bis(trifluoromethylsulfonyl)imide in the commercially available ionic liquid 1‐methyl‐1‐propylpiperidinium bis(trifluoromethylsulfonyl)imide (MPPipTFSI) were investigated. We could identify three distinct cathodic peaks in the potential range from 0 to −2.5 V (vs. Pt quasi‐reference electrode), corresponding to different lithium deposition modes. While in the potential region of the under‐potential deposition (UPD) (−1.2 to −1.8 V) the growth of monoatomic high islands (300–370 pm) takes place, Li bulk deposition occurs at potentials <−2.3 V. Finally, the third peak at 0 V, which only appears after a previous bulk deposition, is connected to a strand‐like growth of lithium at (111) terraces with a uniform orientation over the whole substrate. Interestingly, once reaching a step‐edge, the one‐dimensional growth continues into the electrolyte, indicating the initial stages of Li dendrite formation.