In situ observation of dendrite growth of electrodeposited Li metal

The dendrite growth behavior of Li metal galvanostatically electrodeposited on Ni substrate in a LiClO₄ -propylene carbonate electrolyte solution was in situ observed by a laser scanning confocal microscope with a metallographic microscope. A Li dendrite precursor is stochastically evolved on Ni substrate probably through a solid electrolyte interphase layer produced by the surface chemical reaction between a reduced Li metal and an organic electrolyte. The measured length of randomly growing Li dendrite arms was statistically analyzed. The initiation period of the dendrite precursor becomes shorter with increasing current density and decreasing LiClO₄ concentration. Once it has been initiated, the ionic mass transfer rate starts to govern the growth process of the dendrite arm length, exceeding over the surface chemistry controlling step. The dendrite arm length averaged over the substrate surface grows linearly proportional to the square root of time. The lower the concentration of LiClO₄, the steeper the inclination of the line at 5 mA cm-2, whereas the concentration dependence of inclination is not evident at 0.5 mA cm-2.