Multiscale Investigation Elucidating the Structural Complexities and Electrochemical Properties of Layered-Layered Composite Cathode Materials Synthesized at Low Temperatures

Layered-layered composite (xLi2MnO3∙(1 x) LiMO2, M = Mn, Ni, Co, and Fe) cathode materials have attracted much attention as cathodes for high energy density lithium ion batteries. However, these materials are structurally unstable resulting from complicated phase transformation mechanisms during cycling. Additionally, the complex structural characteristics and structural stability of these materials largely depend on their preparation methods. Studying the correlation between multiscale structural properties and preparation methods is important in the development of layered-layered composite cathode materials. In this work, 0.5Li2MnO3∙0.5LiCoO2 composite materials were prepared with different heating and cooling rates with a maximum temperature of 600 οC. The structural properties of the 0.5Li2MnO3∙0.5LiMO2 composite materials were investigated using combined in-situ X-ray absorption spectroscopy (XAS), in-situ X ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high resolution transmission electron microscopy (HRTEM) techniques. Heating and cooling rates have no significant effect on either the crystal or local atomic structures of the prepared samples. However, the microstructure was critically important for its impact on electrochemical properties.