EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Lithium-ion batteries have revolutionized the field of energy storage. World battery production has exploded in recent years, and demand will continue to grow in the future. However, there are fears of supply or cost problems for certain raw materials. Faced with this observation, it is therefore important to consider an alternative to the lithium-ion technology.
Among the so-called “post-lithium” systems, the Mg-ion batteries are interesting. Magnesium metal theoretically exhibits high capacities, and its low redox potential is compatible with the design of batteries with high energy densities. However, the difficult diffusion of Mg2+ ions in the classic host structures of positive electrode materials (layered or polyanionic compounds) is a challenge. The solution could be to consider positive sulfur-based electrodes, whose electrochemical conversion process also theoretically offers high theoritical capacities. The first electrolyte formulations proposed are in particular the Mg(HMDS)2-AlCl3 or MgCl2-AlC3 mixtures in ethereal solvents. The presence of chlorides increases the corrosive nature of the electrolyte, which is not suitable for industrial transfer. We proposed in 2019 the use of alloys to replace magnesium as the negative electrode and thus be able to use simpler electrolytes in particular based on Mg(TFSI)2. This follows from the good electrochemical behavior of certain elements of the p-block (bismuth, tin, etc.) with the magnesium ions. We will present here a first evaluation of the alloys Mg3Bi2, Mg2Sn and Mg2Pb prepared by mechanochemical synthesis, and the comparison of their electrochemical behavior in a system as standardized as possible. With the same objective, we will also present methods to create artificial layer of the same p-block elements on the magnesium surface.

French National Research Agency (ANR-19-CE05-0013 and ANR-10-LABX-76-01) are acknowledged for funding.