Effects of Zn and Nb doping on the performance of NCM622: a first principles study

LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) is a promising and widely used cathode material, but its further application is limited by serious structural instability and Li⁺/Ni²⁺ mixing. Doping is one of the most effective modification methods. In our study, first-principles calculations were used to explore the effects of single Nb, Zn, or dual Zn-Nb doping on the electrochemical performances of NCM622. It was found that single Zn doped NCM622 achieved the highest energy density (1067.239 mWh g^-1) and the lowest Li⁺ diffusion barrier of 0.507 eV, but its volume change rate obviously increased, indicating a stronger structural instability. Single Nb doping also enhanced the electrochemical performances, but the effect was not outstanding, whereas Zn-Nb dual doping synergistically optimized the performance of NCM622. The Zn-Nb dopants enhanced the structural stability of the layered structure with a widened voltage range and suppressed oxygen release, and realized a higher energy density and a reduced Li⁺ migration barrier of 0.627 eV. This study provides insights into the dual element doping that is helpful to experimentally realize high-performance cathodes.