An In Situ Thiourea Modified Anode Current Collector for Rechargeable Mg Batteries

Rechargeable Mg batteries have gained great interest thanks to the abundant resources and high theoretical capacity of Mg metal anode. However, it suffers from severe passivation and extremely poor plating/stripping kinetics. Herein, a simple salt electrolyte system of Mg(OTf) 2 /MgCl 2 -DME is studied, and the poor Mg affinities on typical metal current collectors are revealed as the key factor for rapid cell failure. Accordingly, an interphase modification on Cu current collector by the in situ generation of a magnesiophilic Cu-thiourea (CuTU) complex is presented. It provides active sites for solvated Mg 2+ as well as Mg. This not only homogenizes Mg 2+ flux but also helps with the release of solvated species to lower the desolvation barrier. The high affinity with Mg further enables the dense and uniform growth of Mg deposits. Thanks to these merits, the facile and reversible plating/stripping of Mg is realized. As a result, the symmetric cells with Mg pre-deposited on CuTU-Cu electrodes stably operate for over 2600 h, which is a 34-fold increase in comparison to the standard Mg foil. Full cells coupling the Mg-CuTU-Cu anode and a PDI-EDA cathode with an N/P ratio of 3 deliver a high capacity of 251 mAh g −1 as well as stable cycling.