Analysis of the Electrochemical Impedance Spectra and the Structure of the Solid Electrolyte Interphase at the Electrodeposited Metallic Lithium Using the Distribution of Relaxation Times Method

The goal of this work is to confirm our earlier conclusion that the regularities observed during the electrodeposition of metallic lithium on copper and lithium electrodes can be associated with differences in the properties of the so-called solid electrolyte interphase formed at these electrodes in contact with the electrolyte. To do this, we analyzed the electrochemical impedance spectra measured during the above processes by using the method of the distribution of relaxation times. The electrolyte addition with surfactants (the cetyltrimethylammonium bromide and hexadecylpyridinium bromide) was shown to lead to a significant change in the properties of the solid electrolyte interphase layers and a noticeable increase in the values of the impedance components associated with the Faradaic processes at these electrodes. This indicates an inhibition of the lithium electrodeposition processes and the related process of dendrite formation under these conditions. At the same time, no such impedance components were observed at the fresh-formed deposit, which confirms our earlier conclusion that the effects of surfactants on the dendrite formation are associated with the changes in the properties of the solid electrolyte interphase layers in the presence of the surfactants, rather than the surfactants’ adsorption at lithium and blocking of the dendrite growth.