Ionic liquids ILs for magnesium Mg electrochemistry

8 Formulae of the ionic liquids and relevant salts tested as potential electrolyte solutions for rechargeable Mg batteries. 

It appears that Mg electrodes, even if initially active, reach passivation in all the IL-based systems presented in Fig. 13.8, no matter which Mg salts are used. Passivation occnrs due to reactions of magnesinm with several types of ILs (as is the case for imidazolinm-based systems), or to reactions with unavoidably present trace water. Onr previons stndies [31] may indicate the reactivity of bare Mg metal with anions snch as ClOF and BF4. The results of such reactivity are the formation of insolnble Mg halides that completely block the Mg electrodes. 

In certain IL systems, such as ethyl-methyl imidazolium-AICI4, Mg metal visibly dissolves. We tried to repeat the experiments described by Nuli et al. [50,51] but were unable to obtain any reversible behavior of Mg electrodes or reversible Mg deposition-dissolntion processes or noble metal electrodes in any of the IL systems described in Fig. 13.8. Hence, we have to conclude that most commonly used ILs, including those showing apparent high cathodic stability, are not suitable solvents for reversible Mg electrodes. Thereby, ILs cannot be considered as compatible/promising electrolyte solutions for non-aqueous magnesium electrochemistry. 

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