Li metal dendrite growth in LiPF6-propylene carbonate (PC) electrolyte was observed in situ by a laser scanning confocal microscope (LSCM) with a metallographic microscope. The development of the electro-deposited Li dendrite length was analyzed, and compared with dendrites grown in LiClO4-PC electrolyte solution. Different anions make different Solid Electrolyte Interphase (SEI) layers on the electrodeposited Li metal. This difference is one factor which causes the morphological variation and the different dendrite growth behavior of Li metal in these electrolytes. The relationship between the Li dendrite growth and Li+ ionic mass transfer rate associated with the electrodeposition of Li metal is examined, and dendrite initiation and growth rate are discussed. The authors find that ionic mass transfer plays an important role in dendrite growth behavior. (C) 2011 Elsevier B.V. All rights reserved.