Spiral waves on the sphere for an alloy electrodeposition model

This paper focuses on the emergence of spiral waves in a specific morpho-electrochemical reaction-diffusion model on a sphere. This study fits in the framework of the morphological control of material electrodeposited onto spherical particles that is crucial to the energetic efficiency of the recharge process as well as to the durability of energy storage devices. The spherical geometry for the electrode surface is of notable practical interest since spheres are the shape of choice for flow batteries and metal-air devices [35]. Motivated by this technological framework, in this paper we extend the results on pattern formation in [27] to include investigations on the spiral wave phenomenology. We show that spiral waves emerge because of the interplay between two specific model parameters: one regulating the oscillatory dynamics in the kinetics and the other one related to the domain size. We present systematic numerical simulations based on the finite element method LSFEM [45,50] accompanied by the computation of suitable indicators that allow to characterize and compare the spatio-temporal features. Interestingly, the model also supports a mechanism of spirals break up leading to a complex spatio-temporal phenomenology. The findings of our study have been validated with experimental results on Ag-In and Ag-Co electrodeposition. The research that led to the present paper was partially supported by a grant of the group GNFM of INdAM.