Dendrite-Free Epitaxial Growth of Lithium Metal during Charging in Li-O2 Batteries.

Lithium (Li) dendrite formation is one of the major hurdles limiting the development of Li-metal batteries, including Li-O2 batteries. Herein, we report the first observation of the dendrite-free epitaxial growth of a Li metal up to 10-μm thick during charging (plating) in the LiBr-LiNO3 dual anion electrolyte under O2 atmosphere. This phenomenon is due to the formation of an ultrathin and homogeneous Li2 O-rich solid-electrolyte interphase (SEI) layer in the preceding discharge (stripping) process, where the corrosive nature of Br- seems to give rise to remove the original incompact passivation layer and NO3- oxidizes (passivates) the freshly formed Li surface to prevent further reactions with the electrolyte. Such reactions keep the SEI thin (<100 nm) and facilitates the electropolishing effect and gets ready for the epitaxial electroplating of Li in the following charge process.