title: Mg(PF6)2-Based Electrolyte Systems: Understanding Electrolyte-Electrode Interactions for the Development of Mg-Ion Batteries.
abstract: 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.
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Evan N
authors.initials: EN
authors.lastname: Keyzer
authors.affiliation: 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.
authors.forename: Hugh F J
authors.initials: HF
authors.lastname: Glass
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Zigeng
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Paul M
authors.initials: PM
authors.lastname: Bayley
authors.affiliation: Cavendish Laboratory, Department of Physics, University of Cambridge , JJ Thomson Avenue, Cambridge CB3 0HE, U.K.
authors.forename: Siân E
authors.initials: SE
authors.lastname: Dutton
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Clare P
authors.initials: CP
authors.lastname: Grey
authors.affiliation: Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
authors.forename: Dominic S
authors.initials: DS
authors.lastname: Wright