The Thermal and Structural Behavior of Li-Rich Cathode Materials Investigated By Synchrotron-Based X-Ray Techniques

Recently, composite layered material between Li₂MnO₃ and LMO₂ (where M= Mn, Co, Ni), also known as the lithium rich cathode material, has received pronounced attention and has been considered as promising cathode materials due to their high discharge capacity of ~250 mAh g^-1 . However, there are several intrinsic problems associated with this material family that need to be solved; e.g., the voltage as well as the capacity decay during cycling, the high irreversible capacity loss in the first cycle, poor rate capability, and oxygen release during cycling, in order to adopt these materials in practical cells. Thermal stability is another challenge which could greatly impact the safety of lithium-ion batteries. In this study, we use in situ X-ray diffraction technique to elucidate the thermal degradation mechanism of 0.5Li₂MnO₃-0.5LiNi_0.33Co_0.33Mn_0.33O₂ lithium rich cathode material in the absence and presence of electrolyte to simulate the real life battery conditions and compare its thermal behavior with the commercial LiNi_0.33Co_0.33Mn_0.33O₂ cathode material. We show that the thermal induced phase transformations in delithiated lithium rich cathode material are much more intense compared to similar single phase layered cathode material in the presence of electrolyte.