Mg(PF6)2-Based Electrolyte Systems: Understanding Electrolyte-Electrode Interactions for the Development of Mg-Ion Batteries

Evan N Keyzer; Hugh F J Glass; Zigeng Liu; Paul M Bayley; Siân E Dutton; Clare P Grey; Dominic S Wright

doi:10.1021/jacs.6b04319

Mg(PF6)2-Based Electrolyte Systems: Understanding Electrolyte-Electrode Interactions for the Development of Mg-Ion Batteries

J Am Chem Soc. 2016 Jul 20;138(28):8682-5. doi: 10.1021/jacs.6b04319. Epub 2016 Jul 11.

Authors

Evan N Keyzer¹, Hugh F J Glass^{1

2}, Zigeng Liu¹, Paul M Bayley¹, Siân E Dutton², Clare P Grey¹, Dominic S Wright¹

Affiliations

¹ Department of Chemistry, University of Cambridge , Lensfield Road, Cambridge CB2 1EW, U.K.
² Cavendish Laboratory, Department of Physics, University of Cambridge , JJ Thomson Avenue, Cambridge CB3 0HE, U.K.

PMID: 27359196
DOI: 10.1021/jacs.6b04319

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.

Publication types

Research Support, Non-U.S. Gov't