Galvanostatic Li Electrodeposition in LiTFSI-PC Electrolyte: Part II. Coupling Phenomena in Growth Process

Li electrodeposition in LiTFSI/PC electrolyte up to 2.22 mAh cm-2 was performed by changing the current density from 0.2 to 60 mA cm-2 under optical microscope observation with a resolution of a few micrometers. The evolution of morphological variation followed by the initial stage (less than 0.028 mAh cm-2 in Part 1) was carefully observed. Two-step linearity was obtained in the relationship between the time variations of apparent electrode diameter and the square root of the duration period. At lower current densities less than 2 mA cm-2, locally and stochastically grown Li deposits with several ten micrometers in length were observed. It grew through SEI layer characterized probably by significant heterogeneous surface chemistry nature. Above 8 mA cm-2, the mass transfer effects on the electrode potential and deposit morphologies became predominant. The movement of suspended particles was occasionally observed. It suggested the induction of natural convection in the organic electrolyte. The limiting current density accompanying Li electrodeposition along a vertical Ni cathode was calculated to be 44 mA cm-2, which was well consistent with the LSV measurement.