Intrinsic Defect and Deformation on Local Structure Caused by Rare‐Earth Ions in the Na3V2(PO4)2F3 Cathode Material

Abstract

Na3V2(PO4)2F3 has been attracting a lot of attention as a positive electrode material for sodium‐ion batteries (SIBs). The deformation of local structure caused by rare‐earth ions and intrinsic defect properties in Na3V2(PO4)2F3 as a positive electrode for SIB have been investigated with atomistic simulation based on the lattice energy minimization. A good reproduction of the Na3V2(PO4)2F3 structure is obtained. It is revealed that Na Frenkel defect, which is formed by sodium interstitial and vacancy pair, is the most favorable type of intrinsic defect. This leads to the formation of stable sodium vacancy required for the Na‐ion diffusion. The results indicate that trivalent rare‐earth dopants at the V3+ site are the most energetically favorable dopants for Na3V2(PO4)2F3, and that the incorporation at the Na and P site could be used as a strategy to increase the sodium vacancy and interstitial, respectively. The deformation in the local structure by the rare‐earth ions doping at the V site is also investigated as helpful in improving the rate performance of SIBs.