XAS investigation of Li-rich, Co-poor layered oxide cathode material with high capacity

We present an ex situ X-ray absorption spectroscopy investigation into lithiation–delithiation of the lithium-rich, but cobaltpoor cathode material Li[Li0.2Ni0.16Mn0.56Co0.08]O2. The main focus of this work is to address the role of manganese and oxygen in the electrochemical redox process and, especially, to identify the phenomena occurring during the initial activation, that is, during the first delithiation–lithiation cycle. Although manganese is not taking part in the initial electrochemical oxidation process, the results indicate that complete Ni2+/Ni4+ and partial Co3+/Co4+ redox processes occur. The electrochemical performance of the material, considering the full and partial redox inactivity of Mn and Co, reveals the participation of oxygen in the overall electrochemical redox process. Finally, it is found, surprisingly, that a partial reduction of Co and Ni takes place at the end of the initial activation.