Synchrotron-based X-ray diffraction and absorption spectroscopy studies on layered LiNixMnyCozO2 cathode materials: A review

LiNixMnyCozO2 (NMCs, x + y + z = 1) represents one promising class of cathode materials for next-generation lithium-ion batteries (LIBs). Compared to the commercialized LiCoO2, the NMC cathodes feature their much higher capacity and lower cost. However, the NMC cathodes, especially for the Ni-rich ones (x >= 0.5), are still experiencing a series of fundamental challenges, such as interfacial instability and structural evolutions. In addressing these issues, it is crucial to explore their underlying mechanisms to guide the rational design of such materials. To this end, in situ and operando X-ray techniques have enabled materials characterizations during battery operation and thereby provide insights on electrochemical reactions in a real-time mode. Thus, these techniques are very attractive and powerful for battery development. In this regard, synchrotron-based X-ray diffraction (XRD) and absorption spectroscopy (XAS) techniques are particularly useful. In this review, we specially summarize the up-to-date research efforts using in situ and operando XRD and XAS for developing lasting improved NMC cathode materials. These two techniques have produced a large amount of compelling data helping researchers gain better understandings and find potential technical solutions of various NMC cathodes.

Automated summary

NMC cathode materials offer higher capacity and lower cost, yet face challenges that require exploring mechanisms using in situ and operando X-ray techniques for rational design guidance. XRD and XAS techniques play a crucial role in battery development.