Ni-rich layered lithium transition metal oxides LiNixMnyCo2O2 (1-y-z ≥ 0.6) are promising candidates for cathode materials,but their practical applications are hindered by high-voltage instability and fast capacity fading.Using density functional theory calculations,we demonstrate that Na-,F-doping,and Na/F-co-doping can stabilize the structure and result into a higher open circuit voltage than pristine LiNi0.6Mn0.2Co0.2O2 (NMC622) during the charging process,which may attain greater discharge capacity.F doping may inhibit the diffusion of Li ions at the beginning and end of charging;Na doping may improve Li ion diffusion due to the increase in Li layer spacing,consistent with prior experiments.Na/F-co-doping into NMC622 promotes rate performance and reduces irreversible phase transitions for two reasons:(i) a synergistic effect between Na and F can effectively restrain the Ni/Li mixing and then enhances the mobility of Li ions and (ii) Ni/Li mixing hinders the Ni ions to migrate into Li layers and thus,stabilizes the structure.This study proposes that a layer cathode material with high electrochemical performance can be achieved via rational dopant modification,which is a promising strategy for designing efficient Li ion batteries.