Mg2Al3, a complex and disordered intermetallic compound as anode material for metal-air batteries

Abstract

The intermetallic compound Mg 2 Al 3 has been selected for this work to be tested as anode in a metal-air battery. The compound is prepared by a high-temperature synthesis from elements and its cubic structure (Fd 3 m, a=28.2341(3) Å) has been refined from X-ray single crystal diffraction data. It is characterized by a high level of disorder with a large number of partially filled atomic sites, split positions, and atomic mixing. The compound displays an interesting behavior towards self-corrosion in alkaline and saline environments, but the better electrochemical performances are obtained in saline NaCl electrolyte. It is shown that both Al and Mg are involved in the oxidation reaction that occurs at the Mg 2 Al 3 electrode used as anode in a metal-air battery. The operating voltage of an Mg 2 Al 3 -air cell is remarkably stable over several hours, and the Mg 2 Al 3 anode efficiency is higher than that of a pure Mg anode in a saline environment.

A review of sodium chloride-based electrolytes and materials for electrochemical energy technology

“…139 Researchers have revealed that the intermetallic compound Mg 2 Al 3 displayed interesting behavior towards self-corrosion in alkaline and saline environments, but better electrochemical performances were obtained in NaCl electrolyte. 140 However, Mg, as a reactive metal, is also susceptible to corrosion in aqueous solutions, thus reducing the anodic utilization rate. 141 A series of studies proved that doping Mg with minor alloying elements (including Al, Li, Pb, Zn, Ce, Y, Bi, Sn, In, Ga, etc.)…”

On the adaptability of 1/1 cubic approximant structure in the Mg–Al–Zn system with the particular example of Mg 32 Al 12 Zn 37

“…Except for Mg2Al3, they are described with totally ordered atomic arrangements. The Bergman line would be extended to Mg4Zn7 (or Mg36Zn64) [33] and Mg2Al3 (or Mg37.3Al62.7, according to its true formula [34,35]). Similarly, Mg21Zn25 (or Mg45.7Zn54.3, e/a = 2) [36] and Mg17Al12 (or Mg58.6Al41.4, e/a = 2.41) [37] are located at both ends the Φ-phase domain.…”

Performance of Mg–9Al–1In Alloy as Anodes for Mg-Air Batteries in 3.5 wt% NaCl Solutions

“…[1][2][3] Recently, Mg alloys have also attracted attention as anodes in Mg-air batteries, which are considered to be a promising power source and energy storage device because of their high theoretical voltages, high current capacities, and environmental friendliness. [4][5][6][7] Mg-air batteries have a negative standard electrode potential (−2.37 V vs SHE), high Faradic capacity (2.2 Ah g −1 ), and relatively low density (1.74 g cm −3 ). 8 Among various types of metal-air batteries, Mg-air batteries have the highest theoretical cell voltage (3.1 V) and a higher specific energy density (6.8 kwh kg −1 ) than Zn-air batteries (1.3 kwh kg −1 ).…”