Gradient Perovskite Ionic–Electronic Heterointerphases for Deep Cycling Mg Metal Anodes

摘要

Direct use of metals with low redox potential and high capacity as anodes canenable high energy density batteries. Mg metal has been considered as anideal anode for its high critical current density and earth-abundance, but itsdevelopment has been impeded by the lacking of Mg-compatible yet costeffectiveelectrolyte. Artificial layers that prevent direct Mg-electrolyte contactwhile permit Mg~（2+） to transport through, mitigate the anode–electrolyteincompatibility and allow industrial Li battery electrolyte analog to implement.However, charge transport through these artificial layers remains elusive,let alone to quantitatively design the layer thickness, components, and theirdistribution. Here it is shown that by using a gradient mixed ion-electronconducting layer, which is prepared by a transferable perovskite film, the ion/electron transport path can be individually and continually tuned. It is foundthat a high Coulombic efficiency of 99.2% can be obtained for Mg anode in0.5 M Mg(TFSI)_2/DME electrolyte. It is also shown that long cycling full cellswith a low N/P ratio (N/P ≈ 3.42 for Mg|Mo_6S_8, N/P ≈ 2.06 for Mg|Cu_(2-x)S) canbe achieved. It is suggested that rational interfacial engineering will open newway to design practical Mg metal batteries.