Li dendrite growth and Li+ ionic mass transfer phenomenon

► Li dendrite growth was observed in situ by a laser scanning confocal microscope. ► We focus the Li+ ionic mass transfer during the electrodeposition of Li metal. ► The morphology of Li dendrites is affected by anion species in electrolyte. ► The dendrite growth initiates without the depletion of Li+ ion at the electrode surface. ► The dendrite length shows the proportionality with the square root of time.