An Electrochemical Impedance Spectroscopy (EIS) Study of Zn-Doped Li (Ni<sub>1/3</sub>Co<sub>1/3</sub>Mn<sub>1/3</sub>) O<sub>2 </sub>Cathode Materials in the First Delithiation Process

Li (Ni 1/3 Co 1/3 Mn 1/3 ) O 2 cathode materials doped by Zn were synthesized by a co-precipitation routine, the first delithiation process of the samples with 0-4wt% of Zn doping were studied by electrochemical impedance spectroscopy (EIS) under the polarized voltage of 2.8-4.6V. The fitting results based on EIS data indicate that delithiation reactions happen within the voltage range of 3.7-4.4V ; The resistances of SEI film and charge transfer are both decreased significantly, whereas Li + diffusion ability through layered crystalline lattice is improved largely with the increase of zinc doping from 0 to 4wt%.