Exploiting cation aggregation in new magnesium amidohaloaluminate electrolytes for magnesium batteries

Etienne V. Brouillet, Marco Amores, Serena A. Corr, Stuart D. Robertson

Research output: Contribution to journalArticle

Abstract

Mg batteries present an attractive and sustainable alternative to Li-ion batteries, wherein magnesium metal as an anode displays a superior theoretical volumetric energy density of 3833 Ah L−1 versus 2062 Ah L-1 for lithium. An outstanding crucial bottleneck in realising their more widespread uptake is the development of suitable electrolytes, where electrode passivation, a limited electrochemical window, conditioning requirements, low ion mobility and low Coulombic efficiencies all contribute to current limitations in Mg batteries. In an area thus far dominated by the thermodynamically stable [Mg2Cl3]+ dinuclear cation, we present here a novel family of magnesium amidohaloaluminate electrolytes [(Dipp)(SiMe3)2NAlCl3]- [MgxCl2x-1]+ where the magnesium chloride cation aggregation has been tailored (x = 1, 2, 3) by substitution of the coordinating ligand to the Mg2+ centre, and show how directly altering this cation affects battery performance (Dipp = 2,6-diisoproplyphenyl, Me = methyl). The electrochemical activity of these new electrolytes has been evaluated by cyclic voltammetry, galvanostatic cycling and impedance spectroscopy in Mg-metal symmetrical cells as well as in battery cells with the Mo6S8 Chevrel phase cathode material against magnesium metal. The monomeric and dimeric magnesium amidohaloaluminate electrolytes facilitate reversible Mg plating and stripping from the Mg-metal anode with excellent stability, withstanding over 70 hours of continuous cycling. We demonstrate the compatibility of these novel electrolytes with the Mo6S8 Chevrel intercalation cathode material, allowing cycling of a Mg-metal cell up to 100 cycles with Coulombic efficiencies above 95%.
Original languageEnglish
Pages (from-to)2305-2312
Number of pages8
JournalInorganic Chemistry Frontiers
Volume7
Issue number12
Early online date1 May 2020
DOIs
Publication statusPublished - 21 Jun 2020

Keywords

  • magnesium batteries
  • Li-ion batteries
  • rechargeable battery

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