A non-flammable and chloride-free electrolyte towards safer rechargeable Mg batteries

Rechargeable Mg batteries are considered one of the most promising next-generation energy storage devices. However, their safety is of growing importance and needs to be considered during their practical applications. Herein, we present a safer Mg battery utilizing a non-flammable and chloride-free electrolyte consisting 0.5 m Mg(TFSI) 2 in hexamethylphosphoramide (HMPA) with 2-methoxyethylamine (MOEA) as the additive. This electrolyte promotes the construction of P, N-rich solid electrolyte interphase on Mg anode, exhibit highly reversibly deposit Mg, as well as exhibits no ignition under open-flame testing. Experimental and theoretical calculations indicate that the introduction of MOEA decrease HMPA coordination numbers in the solvation structure. Consequently, the Mg||Mg symmetric cell delivers a lower overpotential and stably cycled over 700 h at a current density of 0.1 mA cm −2 and a capacity of 0.1 mAh cm −2 . Moreover, the cell coupling the Mg anode and Mo 6 S 8 cathode deliver a capacity of 48.3 mAh g −1 after 500 cycles at 100 mA g −1 with a high average coulombic efficiency close to 100%. Our work provides a novel electrolyte design for the development of high safety rechargeable Mg batteries.