Phase-Transition-Induced Crack Formation in LiNi_0.8Mn_0.1Co_0.1O₂ Cathode Materials: A Comparative Study of Single-Crystalline and Polycrystalline Morphologies Using <i>Operando</i> X-ray CT

Nickel-rich layered oxides, particularly LiNi0.8Mn0.1Co0.1O2 (NMC811), are considered some of the most promising candidates for next-generation battery cathode materials due to their high voltage, high capacity, and cost-effectiveness, which is attributed to the reduction in the cobalt content. However, nickel-rich layered materials suffer from significant capacity decay, especially at high voltages. Therefore, directly observing the crystal structure changes in NMC811 under high voltage and the growth of cracks is crucial for understanding the capacity decay mechanism in these materials. In the present study, we utilized synchrotron radiation technology to enable real-time tracking of lattice and morphological changes. Specifically, we performed high-resolution X-ray diffraction on two different forms of NMC811 (single crystalline and polycrystalline) under various delithiation states to analyze their crystal structure changes. Additionally, operando X-ray computed tomography tests were conducted to observe the morphological changes during charging and discharging.