Mg Battery Electrolytes from Aluminate and Borate Complexes in Ionic Liquids
All of the reversible Mg electrolytes have thus far only been shown to work in ether based solvents, and mainly reported specifically in THF. There are a few practical reasons for this, which will be discussed in this presentation. However, our group was interested in testing the Al and B-based systems in Ionic liquids (ILs), which have several advantageous electrochemical characteristics of their own.6 We therefore report on studies of Mg-organohaloaluminate/borate complexes in ILs. Speciation conditions within the IL media will be discussed and correlated with the electrochemical behavior. Figure 1 shows one such example in which PhMgCl was combined with AlCl3 at a 2:1 molar equivalent ratio within butyl-methylpyrrolidinium bis(trifluorosulfonyl)imide (BMPyrTFSI). This work builds on efforts in our group and elsewhere that has shown a great difficulty with obtaining reversible deposition/dissolution of Mg in ionic liquids using more conventional Mg salts.7 Data like that of figure 1 demonstrate that the appropriate combination of ionic liquid and Mg complex could provide a capable electrolyte for Mg batteries. The unusual looping from the current response in figure 1 is a result of conditions unique to ionic liquids and will be discussed. Further conditions to be considered here will be the effect of the R group, IL cation/anion, temperature, concentration and Mg:Al or Mg:B ratio in the solutions.
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