To exceed the demands of current hybrid, plug-in hybrid and electric vehicles, new battery systems with high energy density are required. Magnesium (Mg) is an attractive alternative to current lithium-ion technologies because of the transfer of 2 electrons per magnesium-ion, higher volumetric capacity of magnesium metal compared to lithium metal (3833 mAh/cm3 Mg vs 2061 mAh/cm3 Li), and greater natural abundance. However, magnesium metal plating/stripping is not possible from analogues of conventional Li-ion electrolytes such as Mg(ClO4)2 or Mg(PF6)2 in carbonate electrolytes. Rather, electrolytes based on organohaloaluminates and organoborates have been favored for electrochemical deposition / dissolution, although corrosion of non-noble metals remains an issue. A deep analytical investigation of the anode / electrolyte interface is essential to understand the complex processes for magnesium batteries and develop future magnesium electrolytes. To analyze the mechanism of Mg deposition and dissolution at the anode, we have combined electrochemical transport measurements with X-ray absorption spectroscopy performed at the beamline 6.3.1.2 ISAACs at the Advanced Light Source. Coupled with potentio/galvano static measurements, we have studied the dynamic interface for magnesium deposition and stripping from the active [Mg2(μ-Cl)3∙6THF](AlCl4) electrolyte using in situ Mg K-edge XANES (Figure 1). From the analysis, we have devised a multi-step mechanism for magnesium deposition from this electrolyte. In addition, we have developed the tools to extend the in situ capabilities to novel electrolyte systems based on magnesium borohydride.

Anode/electrolyte interface for magnesium batteries

249th National Meeting (2015)

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