Electrochemical and structural analysis of Mg substitution in lithium-rich layered oxide for lithium-ion battery

Mg-doped lithium-rich layered oxide Li_1.2Mn_0.54Ni_0.13Co_0.13O₂ with smooth morphology is synthesized by co-precipitation followed by calcination. The morphologies of bare particles and electrodes have been studied through scanning electron microscopy (SEM), which illustrates that, compared with the Mg-doped particles, the pristine particles are characteristic of angular and corrosion is much more likely to happen. Additionally, the Mg substitution can make the crystal structure stable during the electrode process and then enhance the cycle performance. Electrochemical impedance spectroscopy and transmission electron microscopy have been utilized to gain insight to the properties of pristine and Mg-doped particles before and after the electrode process. Mg-doped particles show lower charge transfer resistance and higher diffusion coefficients (D) of the diffusing lithium ions. After 100 cycles at 250 mA g^?1, the morphology and crystal structure of Mg-doped materials show smaller changes than those of pristine particles.