The interfacial instability of the Mg metal in chlorine-free magnesium electrolytes severely hinders the practical applications of rechargeable magnesium batteries (RMBs). Conventionally, the reversibility and longevity of Mg metal have been primarily associated with the bulk Mg2+ solvation structure in organic electrolytes. However, the electric double layer (EDL) is the real microscopic region where all electrochemical reactions occur. With the region, both electronic and ionic charges undergo periodic rearrangement with surface charge fluctuation during electrochemical processes. Consequently, the structure and properties of EDL critically influence the Mg electroplating process, which has been severely overlooked for a long time. Here, for the first time, we propose a novel strategy of tuning the anion structure in Mg salt to rearrange EDL, thereby simultaneously regulating the uniformity of electroplated Mg morphology and building an inorganic-rich, high-quality solid electrolyte interphase (SEI) layer, achieving a highly reversible Mg anode. We designed a novel highly fluorinated asymmetric Mg salt, magnesium perfluoro(2-ethoxyethane)sulfonate (Mg(PES)2), which endows the Mg metal anode with superior Coulombic efficiency (CE) of over 99.2 %, ultra-low overpotential of 20 mV and remarkable cyclability of over 4500 h This work introduces a new strategy for multivalent cation anodes, emphasizing interfacial chemistry regulation over traditional bulk solvation structure design. We believe this insightful approach will open up new frontiers in the design for advanced multivalent electrolyte development.

中文翻译：

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通过高度氟化不对称镁盐的可调双电层结构实现可逆的 Mg 化学


Mg 金属在无氯镁电解质中的界面不稳定性严重阻碍了可充电镁电池 （RMBs） 的实际应用。传统上，Mg 金属的可逆性和寿命主要与有机电解质中的块体 Mg2+ 溶剂化结构有关。然而，双电层 （EDL） 是所有电化学反应发生的真正微观区域。在该区域中，电子电荷和离子电荷在电化学过程中都会随着表面电荷波动而发生周期性重排。因此，EDL 的结构和性能对 Mg 电镀工艺产生了重大影响，而这一工艺长期以来一直被严重忽视。在这里，我们首次提出了一种新的策略，即调整 Mg 盐中的阴离子结构以重排 EDL，从而同时调节电镀 Mg 形态的均匀性并构建富含无机物的高质量固体电解质界面 （SEI） 层，实现高度可逆的 Mg 阳极。我们设计了一种新型高度氟化的不对称 Mg 盐，全氟（2-乙氧基乙烷）磺酸镁 （Mg（PES）2），它赋予 Mg 金属负极超过 99.2 % 的卓越库仑效率 （CE），20 mV 的超低过电位和超过 4500 h 的显着循环性这项工作引入了一种多价阳离子负极的新策略，强调界面化学调节而不是传统的体溶剂化结构设计。我们相信这种富有洞察力的方法将为先进的多价电解质开发设计开辟新的领域。