Electrolyte challenges and strategies toward better rechargeable magnesium-metal batteries

Rechargeable magnesium-metal batteries (RMBs) are promising candidates for large-scale energy storage systems, leveraging magnesium's abundant crustal reserves, high theoretical capacity, low redox potential, and high inherent safety. However, the practical implementation of RMBs remains severely constrained by the limited availability of efficient electrolytes capable of simultaneously providing a wide voltage window, rapid Mg²⁺ transport, and good chemical compatibility with electrodes. Particularly, a passivation layer impermeable to Mg²⁺ ions is readily formed on the Mg anode surface in most conventional electrolytes, thereby inhibiting continuous Mg deposition/stripping. Therefore, it is highly necessary to develop innovational high-performance electrolytes for RMBs. This review first dissects the fundamental challenges faced by the electrolytes in RMBs and proposes the requirements of practical electrolytes for RMBs. Afterwards, we systematically analyze the electrochemical roles of key components, including Mg salts, solvents, and functional additives, in regulating ion transport and interfacial dynamics. Furthermore, particular emphasis is placed on electrode–electrolyte interphase engineering strategies to tailor Mg²⁺ desolvation kinetics and restrain parasitic reactions at the electrode/electrolyte interface. Finally, we present future research perspectives aimed at the rational design of efficient electrolytes, advancing the development of high-performance RMBs.