In the last years, concerns on Li availability have prompted the search for suitable alternatives to rechargeable Li-ion batteries. Batteries based on multivalent charge carriers (Mⁿ⁺) can exhibit advantages in terms of energy density since for a certain amount of M carriers the capacity is doubled (n=2) or tripled (n=3) when compared to single valent carriers like Li⁺ or Na⁺. Calcium is an attractive candidate due to its low cost, natural abundance and low reduction potential. At this very early stage of the Ca-batteries technology, the quest for a high specific energy cathode material is an active field. The general goal of our work is the identification of materials able to function as positive electrode in Ca batteries.

DFT is a unique tool to quickly screen a variety of structures and compositions to identify potential cathode materials for this novel technology. The general strategy is firstly to calculate average voltage and volume changes associated to the Ca insertion reaction. Further, DFT theory could be applied to gather additional information regarding electronic and ionic conductivities, crystal structure of intercalated phases and precise voltage-composition-curves at various temperatures. In this communication, we will present a survey of recent results for oxides, silicates and sulphides as cathode for Ca batteries. Special attention is given to the calculation and analysis of Ca migration pathways using the NEB method. In good agreement with parallel experimental investigations [1-3], we found that the low ionic mobility is the main handicap for the insertion/deinsertion of Ca ions in most structures. Yet, for some materials, Ca intercalation is predicted at low C rates.

Acknowledgments: Authors are grateful for financial support from European Union H2020-FETOPEN funded project CARBAT-766617.

References;

[1]. M.E. Arroyo-de Dompablo, C. Krich, J. Nava-Avendaño, M.R. Palacin, F. Barde. Phys. Chem. Chem. Phys. 18 (2016) 19966.

[2]. M.E. Arroyo-de Dompablo, C. Krich, J. Nava-Avendaño, N. Biskup, M.R. Palacin, F. Barde. Chem. Mater. 28 (2016) 6886.

[3]. D. Tchitchekova, A. Ponrouch, R. Verrelli, T. Broux, C. Frontera, A. Sorrentino, F. Barde, N. Biskup, M.E. Arroyo-de Dompablo, M.R. Palacin. Chem. Mater. 30 (2018) 847.