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

Abstract

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.