The observation of electrochemical dissolution of lithium metal using electrochemical quartz crystal microbalance and in-situ tapping mode atomic force microscopy

The electrochemical behavior of lithium metal in nonaqueous electrolytes co ntaining a small amount of HF was analyzed using an electrochemical quartz crystal microbalance (ECQCM) and in-situ fluid tapping mode atomic force mi croscopy (F-TMAFM). The mass change obtained by the ECQCM revealed that ele ctrochemically dissolved lithium metal was accompanied by chemical reaction s of the lithium metal with the nonaqueous electrolytes. On the other hand, the dissolution of the electrodeposited lithium metal was clearly observed with the F-TMAFM. This observation indicates that a breakdown of the surfa ce film on the lithium metal takes place during the dissolution process. Fr om these results obtained using the ECQCM and F-TMAFM methods, it can be co ncluded that the chemical reactions of lithium metal with nonaqueous electr olytes are caused by the breakdown of the surface film. This phenomenon is strongly related to the low Coulombic efficiency of the deposition and diss olution cycles of lithium metal in nonaqueous electrolytes containing HF.