Stable Magnesium Negative Electrodes Achieved via Dy Microalloying for Rechargeable Magnesium Batteries.

Abstract

Rechargeable magnesium batteries (RMBs) are a promising alternative technology to lithium-ion batteries owing to the abundant resources, high theoretical volumetric energy density, and relatively high safety. Nevertheless, the nonuniform deposition/dissolution behavior, interfacial passivation, and exacerbated polarization under high current densities of magnesium metal negative electrodes severely impede their practical implementation. In this study, we propose a Dy microalloying strategy to regulate the microstructure and deposition/dissolution behavior of the magnesium negative electrode. The incorporation of low-concentration Dy (0.7 wt %) induces grain refinement and crystal texture evolution and alleviates galvanic corrosion due to the similar electrode potentials of Dy and Mg. This synergistic effect enhances the electrochemical reaction kinetics, structural integrity, and interfacial stability, thereby improving the uniformity of Mg deposition/dissolution. Therefore, the Mg-0.7Dy alloy negative electrode achieves a long cycle life exceeding 2500 h in symmetric cells at 1 mA cm-2 and 1 mA h cm-2. Moreover, the Mg-0.7Dy∥Mo6S8 full cell maintains a specific capacity of 59.67 mA h g-1 after 4000 cycles at 5 C, corresponding to a high capacity retention of 93.84%. This work demonstrates the feasibility of regulating the microstructure and deposition/dissolution behavior of the magnesium negative electrode through Dy microalloying engineering, offering a feasible strategy for developing high-performance negative electrodes for RMBs.

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