Periodic Reporting for period 3 - CAMBAT (Calcium and magnesium metal anode based batteries)
Reporting period: 2020-01-01 to 2021-06-30
In parallel, a detailed investigation on the passivation layers being formed at the surface of Ca metal electrode was performed in order to identify the passivation layer component allowing for Ca2+ migration. Borates were identified as potential passivation layer component allowing for Ca plating. A simple pre-passivation procedure was then tested, allowing us to transfer a passivated electrode (the passivation layer containing borates) in an electrolyte that was optimized in terms of ion pairing but which does not usually allow for Ca plating. After this pre-passivation step, not only Ca plating could be observed, but an enhanced electrochemical response – ca. 4 times higher current densities was observed. This strongly suggests that the nature of the passivation layer is key to enable Ca plating and that the composition of the electrolyte plays a major role in the overall plating kinetics. Both the cation mobility in the electrolyte and the interfacial phenomena such as de-solvation are thus interconnected properties of utmost importance for practical Ca batteries.