In-Situ Observation of Lithium Whisker Growth during Li Electrochemical Deposition

In spite of extensive research that has been done for several decades to utilize the lithium (Li) metal anode, Li metallic anode is still suffering from dendritic structure growth and low columbic efficiency. We address this problem with a new viewpoint for the mechanism of the Li dendritic structure growth and origin of low columbic efficiency. Our in-situ optical/TEM observation reveals that the growth of the dendritic structure starts from the root instead of the tip. The oxidation of Li metal was observed in the middle of the structure. This observation has a discrepancy with conventional dendrite growth mechanism. The elemental mapping suggests the partial dissolution of Li in the interface between the Li metal and copper (Cu) current collector. This observation further suggests that the Li dendritic structure growth from its root was originated from Li-Cu alloying process. We expect that the mechanism of Li root growth during electrodeposition will contribute to a new paradigm on Li metal anode application such as Li-ion, Li-S and Li-air batteries for the next generation of energy storage.