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

Abstract

The ‘composite’ layered material of 0.5Li₂MnO₃·0.5LiMn_0.42Ni_0.42Co_0.16O₂ 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 (E_a) 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 1^st cycle) are kinetically limited as compared with that from the LiMn_0.42Ni_0.42Co_0.16O₂ component, and the lithium ion insertion processes into the MnO₂ (after the 1^st cycle) component are kinetically limited as compared with that into the Mn_0.42Ni_0.42Co_0.16O₂ component. In addition, the interface reaction of the lithium ion into the Mn_0.42Ni_0.42Co_0.16O₂ component is also easier than that of the lithium ion into the MnO₂ component originated from the Li₂MnO₃ component.