Oxidation potential is the tendency for a metal to lose electrons and become oxidized. This is a useful concept to know as it plays a role in many applications, including corrosion resistance and lithium-ion battery cell design.
Aluminium oxide, or Al2O3, is a commonly used aluminium alloy that has become the standard current collector in many Li-ion batteries. It is resistant to anodic dissolution and has long been a popular metal for use in these devices, but it is also susceptible to damage from the high voltages required to generate the current.
Fortunately, there are now a number of alternative methods to achieve the same corrosion protection as anodising. However, these methods are generally not as robust as anodising due to their limitations in terms of their self-healing properties.
The oxidation potential of an aluminium surface is one of the most important factors determining its level of corrosion resistance. As a result, a careful choice of the thickness of the protective coating can be critical for maintaining its performance and preventing localised corrosion.
Simulations of this oxidation behaviour are a promising method of studying the properties of this material as they allow us to examine the structural changes that occur during the oxidation process. Using our atomistic model, we can determine the density of a metal-oxide junction as a function of its position in z and see how this changes over the course of the oxidation process.
We find that the oxidation process is self-limiting as shown in the figure below, and the resulting oxide layer is of a low stoichiometric ratio of oxygen to aluminium. We also find that the density at Al-AlOx interfaces decreases and the atomic structure of the deposited aluminium contacts crystallises. These results are in line with experimental reports on the structure of these surfaces.