A perspective on the key factors of safety for rechargeable magnesium batteries

Abstract

Rechargeable Mg batteries (RMBs) have become one of the best subsitutes for lithium-ion batteries due to the high volumetric capacity, abundant resources, and uniform plating behavior of Mg metal anode. However, the safety hazard induced by the formation of high-modulue Mg dendrites under a high current density (10 mA cm−1) was still revealed in recent years. It has forced researchers to re-examine the safety of RMBs. In this review, the intrinsic safety factors of key components in RMBs, such as uneven plating, pitting and flammability of Mg anode, heat release and crystalline water decomposition of cathode, strong corrosion, low oxidition stability and flammability of electrolytes, and so forth, are systematacially summarized. Their origins, formation mechanisms, and possible safety hazards are deeply discussed. To develop high-performance Mg anode, current strategies including designing artificial SEI, three-dimensional substrates, and Mg alloys are summarized. For practical electrolytes, the configurations of boron-centered anions and simple Mg salts and the functionalized solvent with high boiling point and low flammability are suggested to comprehensively design. In addition, the future study should more focus on the investigation on the thermal runaway and decomposition of cathode materials and separators. This review aims to provide fundamental insights into the relationship between electrochemistry and safety, further promoting the sustainable development of RMBs.