An Electrochemically Polymerized Protective Layer for a Magnesium Metal Anode

Rechargeable magnesium (Mg) batteries are promising beyond Li-ion technologies due to their high volumetric capacity (3832 mAh cm–3) and high natural abundance. Nonetheless, the Mg metal anode is incompatible with most conventional electrolytes, which leads to the formation of an ionically passivating layer, and it also suffers from growth of dendrites similar to Li, which can cause failure of the cells. In this study, 1,3-dioxolane (DOL) was electrochemically polymerized to form a thin, Mg2+-conducting elastomeric artificial solid electrolyte interphase (ASEI) layer by pretreating Mg metal anodes. This protective ASEI layer enables excellent cyclability of Mg–Mg symmetric cells at high current density over 400 h at a stable, low overpotential (0.50 V vs Mg2+/Mg) without cell short-circuiting, while untreated pristine Mg symmetric cells quickly failed. Surface chemistry analysis by X-ray photoelectron spectroscopy showed that the poly-DOL component in the elastomer was well preserved postcycling.