Electrochemical kinetics of the 0.5Li2MnO3·0.5LiMn0.42Ni0.42Co0.16O2 ‘composite’ layered cathode material for lithium-ion batteries

The ‘composite’ layered material of 0.5Li2MnO3·0.5LiMn0.42Ni0.42Co0.16O2 has been successfully prepared by the solid state reaction method, and was characterized by XRD and SEM methods. The kinetics of the electrochemical insertion and extraction of lithium ions during the first three cycles in this material was investigated in detail by the open-circuit voltage (OCV), galvanostatic intermittent titration technique (GITT), and electrochemical impedance spectroscopy (EIS) methods. The activation energies (Ea) of interfacial lithium ion transfer at various oxidation–reduction reactions were evaluated from the temperature-dependence of lithium ion transfer resistance. The results show that the electrochemical kinetics of the lithium ion extraction and insertion reactions in the first three cycles of this ‘composite’ material is mainly controlled by the Li2MnO3 and Li2MnO3-related components in this material. The lithium ion extraction processes from the Li2MnO3 component and LiMnO2 component (after the 1st cycle) are kinetically limited as compared with that from the LiMn0.42Ni0.42Co0.16O2 component, and the lithium ion insertion processes into the MnO2 (after the 1st cycle) component are kinetically limited as compared with that into the Mn0.42Ni0.42Co0.16O2 component. In addition, the interface reaction of the lithium ion into the Mn0.42Ni0.42Co0.16O2 component is also easier than that of the lithium ion into the MnO2 component originated from the Li2MnO3 component.