Binary Mg-1 at%Gd alloy anode for high-performance rechargeable magnesium batteries

Abstract

Rechargeable magnesium batteries (RMBs) become a highly promising candidate for the large-scale energy storage system by right of the high volumetric capacity, intrinsic safety and abundant resources of Mg anode. However, the uneven Mg stripping and large overpotential will cause a severe pitting perforation and the followed failure of Mg anode. Herein, we proposed a high-performance binary Mg-1 at% Gd alloy anode prepared by the melting and hot extrusion. The introduction of 1 at% Gd element can effectively reduce the Mg²⁺ diffusion energy barrier (0.34 eV) on alloy surface and induces the formation of a robust and low-resistance electrolyte/anode interphase, thus enabling a uniform and fast Mg plating/stripping. As a result, the Mg-1 at.% Gd anode displays a largely enhanced life of 220 h and a low overpotential of 213 mV at a high current density of 5.0 mA cm^-2 with 2.5 mAh cm^-2 . Moreover, the assembled Mg-1 at.% Gd//Mo₆ S₈ full cell delivers a high rate performance (73.5 mAh g^-1 at 5 C) and ultralong cycling stability of 8000 cycles at 5 C. This work brings new insights to design the new-type and practical Mg alloy anodes for commercial RMBs.

Keywords: Binary Mg alloys; Mg anodes; electrochemistry; long cycling life; rechargeable Mg batteries.