Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
Cavendish Laboratory, Department of Physics, University of Cambridge , JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
J Am Chem Soc. 2016 Jul 20;138(28):8682-5. doi: 10.1021/jacs.6b04319. Epub 2016 Jul 11.
Mg(PF6)2-based electrolytes for Mg-ion batteries have not received the same attention as the analogous LiPF6-based electrolytes used in most Li-ion cells owing to the perception that the PF6(-) anion decomposes on and passivates Mg electrodes. No synthesis of the Mg(PF6)2 salt has been reported, nor have its solutions been studied electrochemically. Here, we report the synthesis of the complex Mg(PF6)2(CH3CN)6 and its solution-state electrochemistry. Solutions of Mg(PF6)2(CH3CN)6 in CH3CN and CH3CN/THF mixtures exhibit high conductivities (up to 28 mS·cm(-1)) and electrochemical stability up to at least 4 V vs Mg on Al electrodes. Contrary to established perceptions, Mg electrodes are observed to remain electrochemically active when cycled in the presence of these Mg(PF6)2-based electrolytes, with no fluoride (i.e., MgF2) formed on the Mg surface. Stainless steel electrodes are found to corrode when cycled in the presence of Mg(PF6)2 solutions, but Al electrodes are passivated. The electrolytes have been used in a prototype Mg battery with a Mg anode and Chevrel (Mo3S4)-phase cathode.
基于 Mg(PF6)2 的电解质在 Mg 离子电池中的应用尚未得到与类似的 LiPF6 基电解质相同的关注，因为人们认为 PF6(-)阴离子在 Mg 电极上分解并使 Mg 电极钝化。目前尚未报道 Mg(PF6)2 盐的合成，也未对其溶液进行电化学研究。在这里，我们报告了复杂的 Mg(PF6)2(CH3CN)6 的合成及其溶液电化学。Mg(PF6)2(CH3CN)6 在 CH3CN 和 CH3CN/THF 混合物中的溶液表现出高电导率（高达 28 mS·cm(-1)）和电化学稳定性，在 Al 电极上至少可达 4 V 以上。与既定观念相反，当在这些基于 Mg(PF6)2 的电解质中循环时，Mg 电极被观察到保持电化学活性，在 Mg 表面上没有形成氟化物（即 MgF2）。发现不锈钢电极在存在 Mg(PF6)2 溶液的情况下循环时会腐蚀，但 Al 电极被钝化。该电解质已用于具有 Mg 阳极和 Chevrel（Mo3S4）相阴极的原型 Mg 电池中。
