First-principles study on the properties of Ta doped P2-Na2/3Fe1/3Mn2/3O2 for Na-ion batteries

P2-Na2/3Fe1/3Mn2/3O2 (NFM) is a layered transition material with abundant raw materials, high specific capacity, and excellent cycling stability, a potential cathode material for sodium-ion batteries. The considerable size and substantial mass of Na+ present notable challenges concerning unfavorable reaction kinetics and structural instability during the insertion and extraction processes. This presents a formidable obstacle for practical applications. Ta5+ is characterized by higher valence and more muscular bonding energy, and doping Ta in NFM leads to the formation of a stable crystal structure. In the present work, we use first-principles calculations within the DFT + U framework to investigate different concentrations of Ta-doped MFMs to overcome these drawbacks. The calculated results show that the introduction of Ta elements reduces the formation energy and enhances the structural stability. It also enhances the electronic conductivity (i.e., the band gap, Eg = 0) and lowers the ion mobility barrier. In addition, we also investigate the electronic structure, spin, and magnetic properties of doping controlled electrode materials to investigate the doping effect regulating migration energy barriers. This study suggests that Ta-doped NFMT is a good alternative due to higher performance compared to the pristine NFM.