Galvanostatic Li Electrodeposition in LiTFSI-PC Electrolyte: Part I. Effects of Current Density in Initial Stage

Galvanostatic electrodeposition of Li was carried out in 1 M LiTFSI/PC electrolyte to investigate the effect of current density on the morphological variations during the initial stage of the electrodeposition. The solid electrolyte interphase (SEI) formation process was analyzed from the potential change combined with XPS and UPS measurements along with SEM observation of Li deposits. A significant difference in the deposited Li morphology was observed depending on the current density. The simultaneous growth of whisker-like and granular deposits was noticed at lower current density, while the experiments at higher current densities evolved rather uniform mesoscopic-sized rod development. The formation behavior of SEI prior to Li deposition also differed between lower and higher current densities, of which the transition was about 4 mA cm⁻². It was deduced that the formation history of SEI affected the surface defect density heterogeneity and mass transport properties inside SEI. The event of “sprouting,” in which Li precipitates nucleated and grown in SEI are extruded from the SEI layer into the electrolyte, certainly influenced the subsequent growth mode.