First principles study of the crystal, electronic structure, and diffusion mechanism of polaron-Na vacancy of Na3MnPO4CO3 for Na-ion battery applications

Based on first principles calculations, we investigate the geometry, electronic structure, and diffusion mechanism of Na ions in Na3MnPO4CO3 using density functional theory with a Hubbard potential correction. Our results suggest that the structure of Na3MnPO4CO3 can be deintercalated with more than one Na ion, and that the removal of a Na ion can form a bound polaron. We find that our calculations of the intercalation voltages for the redox couples Mn2+/Mn3+ and Mn3+/Mn4+ agree very well with the experimental data. In addition, we demonstrate that Na in Na3MnPO4CO3 can diffuse in three directions with low activation energy barriers, allowing a fast charging rate.