Rechargeable Mg metal batteries enabled by a protection layer formed in vivo

The rise of rechargeable Mg batteries, a candidate for replacing lithium-ion batteries, is constrained by the electrolytes severely. Unfortunately, the Mg anode usually forms a blocking layer to impede the penetration of divalent Mg2+ in traditional electrolytes. Here, we demonstrate a protection layer formed in vivo on the surface of Mg metal anodes by adding GeCl4 into ether electrolyte, successfully preserving structure stability and showing a low overpotential even at high current density of 10 mA cm(-2). Due to the excess additives in electrolyte, self-repair effect of the protection layer emerges over electrochemical cycling. Significantly, full cells with Mg metal anodes paired with both TiS2 and Ti3C2 cathodes in GeCl4-containing ether electrolyte are also presented. Our work paves a new way towards rational design of self-repair protection layer via a facile chemistry route in simple Mg salt electrolyte system.