Unconventional Dendrite‐Free Deposition of Mg Metal Anodes at Low Temperatures

ABSTRACT Temperature plays a critical role in governing the plating behavior of metallic anodes by regulating ionic conductivity of the electrolyte, desolvation energy, and charge transfer processes in the solid‐electrolyte interphase (SEI). While low temperature commonly triggers dendritic growth on metallic anodes (e.g., Li, Na, and Zn), the temperature effect on Mg plating/stripping behaviors remains unknown thus far. Herein, we report an unconventional temperature‐dependent deposition behavior of Mg anodes that tends to form dendrite‐free deposits at low temperatures. Integration of cryo‐transmission electron microscopy, atomic force microscopy, and x‐ray photoelectron spectroscopy reveals that the SEI layer formed at low temperatures has an ultrathin thickness (∼2‐3 nm) and is enriched in high‐modulus inorganic compounds, which facilitates the uniform deposition of Mg anodes. As a result, the Mg metal anode realizes an exceptional average Coulombic efficiency up to 99.92% over 2000 cycles at −20°C. This study demonstrates the unconventional deposition behavior of Mg metal anodes at low temperatures, underpinning their potential for low‐temperature applications and advancing the fundamental understanding of metal deposition.