Electrolytes for Magnesium Batteries: Which Way to Go?

Abstract

Magnesium battery technology is one of the promising post-lithium technology, that has potential to reduce our lithium dependence, and at the same time outperform current Li-ion technology. Magnesium is more abundant, hence cheaper, and comes with promises of higher energy density and lower tendency to dendrite formation – possibility of metallic anode application. Higher capacity of such battery comes from double charge of magnesium ion, that also causes battery chemistry more difficult. Especially electrode/electrolyte interface becomes tricky, and simple transfer of electrolyte concept from lithium technology is not possible. Reversible plating/stripping of magnesium has been demonstrated many times, however in most of the cases from highly reactive and/or aggressive electrolytes. That put some obstacles on the way for future commercialization and a key challenge on the road to a rechargeable magnesium batteries is the development of non-corrosive magnesium electrolytes.For some time, role of chloride in electrode process was considered to be essential for reduction of magnesium ions. However new studies show possible operation of magnesium battery with Cl-free electrolyte. Conditions for that are not completely clear, and here we are going to put some light on the processes occurring at electrode/electrolyte interfaces. DFT calculations are used to understand desolvation of magnesium ion, which is a key step prior to reduction at the electrode. Comparison of both systems, with standard and Cl-free electrolytes, shows the possibility to tune electrode process by changes in electrolyte composition, indicating the way towards the less reactive, and less corrosive systems. Presented results were obtained within E-MAGIC project, which received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 824066.