Electrochemical study of mass transfer in Li-Mg and Li-Mg-Al alloys

The interdiffusion coefficients in Li-Mg alloys and Li-Mg-Al alloys were evaluated using transient techniques such as chronopotentiometry and chronoamperometry. Anodic or cathodic pulses were imposed on the alloy electrodes under galvanostatic and potentiostatic conditions. Taking into account charging of the double layer, ohmic drop, adsorption of diffusing species and electrolyte-electrode boundary shift, the diffusion coefficients of lithium in Li-Mg alloys (α-phase and β-phase) and in Li-Mg-Al alloys were estimated at around 420°C. In the case of Li-Mg α-phase alloys, the values of the diffusion coefficients,D _Li, can be represented in a polynomial expansion of the composition of the alloy,X _Li (mol%) as follows: $$ln D_{Li} = - 19.850 - 0.4294X_{Li} + 0.0249X_{Li}^2$$ The diffusion coefficients of lithium in Li-Mg (β-phase) alloys show extremely large values (?10^?6 cm²s^?1) as also in the Li-Al β-phase alloys.