Na2Mn(CO3)2: A carbonate based prototype cathode material for Na-ion batteries with high rate capability — An ab-initio study

• Published in: Electrochimica acta Vol. 439; p. 141687
• Main Authors: Sudarsanan, Vishnu, Augustine, Anu Maria, Ravindran, P.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 20.01.2023
• Subjects: Ab-inito; Cathode materials; Diffusion; Na-ion batteries; Polyanionic materials; Cathode materials; Diffusion; Polyanionic materials; Ab-inito; Na-ion batteries
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2022.141687

Considering the mounting demand for energy storage systems and the issues associated with the current cathode materials, it is necessary that the search space for novel cathode materials for rechargeable batteries should be widened. In this regard, we have presented the structural, lattice dynamical, electrochemical, and electronic structure studies of a carbonate-based prototype cathode material for Na-ion batteries, using first-principles calculations. The existence of a carbon-containing Mn compound Na2Mn(CO3)2 is predicted using first-principles calculations and the compound is expected to crystallize in trigonal crystal structure with R3̄ space group. The electrochemical analyses reveal that this cathode material could deliver a theoretical capacity of 243mAh/g and a theoretical average voltage of 3.6 V. The desodiation process is modeled via finding the stable crystal structure of intermediate compositions for different Na/vacancy concentrations. The electronic structure and charge density analysis of these intermediate compositions reveal that Mn, O, and a small contribution from C involve in the desodiation process. Even though the involvement of O in the redox is high, we have found that the oxygen evolution during desodiation is not favored thermodynamically, indicating a possible enhancement in the specific capacity. The chemical bonding analyses indicate that the Mn-O bonding interaction is iono-covalent, whereas the C-O bond exhibits a more covalent character with small ionicity. The activation energy of the diffusion barrier for the Na diffusion through the lower energy path in Na2Mn(CO3)2 is estimated to be 0.22 eV using nudged elastic band method. We postulate high ionic conductivity and thereby high rate capability for Na2Mn(CO3)2 as the Na diffusion coefficient is relatively higher compared with that of Li in cathodes used for commercial Li-ion batteries. [Display omitted]