  A novel approach is presented to efficiently include transport effects in
thin active material coating layers of all-solid-state batteries using a
dimensionally reduced formulation embedded into a three-dimensionally resolved
coupled electrochemo-mechanical continuum model. In the literature, the effect
of coating layers is so far captured by additional zero-dimensional resistances
to circumvent the need for an extremely fine mesh resolution. However, a
zero-dimensional resistance cannot capture transport phenomena along the
coating layer, which can become significant, as we will show in this work.
Thus, we propose a model which resolves the thin coating layer in a
two-dimensional manifold based on model assumptions in the direction of the
thickness. This two-dimensional formulation is monolithically coupled with a
three-dimensional model representing the other components of a battery cell.
The approach is validated by showing conservation properties and convergence
and by comparing the results with those computed with a fully resolved model.
Results for realistic microstructures of a battery cell, including coating
layers as well as design recommendations for a preferred coating layer, are
presented. Based on those results, we show that existing modeling approaches
feature remarkable errors when transport along the coating layer is
significant, whereas the novel approach resolves this.
