Oxygen dissolution behaviour in (52/48) mol% Li2CO3/Na2CO3 electrolyte containing Ba and Ca additives

Oxygen dissolution in (52/48) mol % Li2CO3/Na2CO3 melt containing minor additions of two earth alkaline carbonates has been investigated as a function of temperature and gas composition. The addition of 3 mol% of (1.5BaCO3 + 1.5CaCO3) to the Li/Na carbonate melt yields an increase of the total oxygen solubility at 923 K of about three times the value obtained for the additive-free electrolyte. Moreover, the presence of Ba and Ca in the Li/Na carbonate makes the O2 solubilization process dependent on the temperature changes within the entire range examined, i.e. 823 K-973 K. The main oxygenated species produced within the additive-containing Li/Na system remains essentially invariant at 923 K with respect to the additive-free melt (superoxide + peroxymonocarbonate, SOP + POMCP). Meanwhile, at 873 K, a change has been verified in the mechanism of oxygen dissolution from molecular oxygen to SOP + POMCP, thus explaining the different melt behaviour at temperatures lower than 923 K.