CPM Seminar

Computational Modeling of Calcium Ion Batteries

Manuel Smeu

Department of Physics
Binghamton University

Batteries utilizing Ca ions have received very little attention to date due to difficulties in identifying adequate cathode materials and electrolytes, although advancements have been made on both fronts. If these challenges can be overcome, Ca can offer an abundant and affordable alternative to Li for grid storage and in other applications where portability is not a priority. This also offers many opportunities to study and exploit novel physics and electrochemistry. For example, the multivalent nature of Ca ions allows for two electrons to be transferred for a single atom, thereby permitting higher volumetric capacities. For such technologies to be developed, appropriate cathodes need to be identified that will allow for reversible intercalation of CA²⁺ ions and that can provide a desirable voltage, which will be addressed in the first part of the talk. We use density functional theory to make predictions about the voltage, stability and ion diffusion properties of various cathodes, including the Chevrel phase (Mo₆S₈), and several manganese dioxide (MnO₂) polymorphs. We found that the intercalation of Ca yields a higher voltage than that of Mg for nearly all systems considered, and the volumetric capacity can exceed that of Li ions. Next, we address the electrolyte. Ab initio molecular dynamics simulations were carried out to model the chemical reactions that occur at the metallic Ca anode, to study the solid electrolyte interphase (SEI) layer that forms, and to model the ion diffusion through this layer. Our results show that the realization of Ca ion batteries is feasible as long as the cathode and electrolyte are carefully selected to be compatible with CA²⁺ ions.