Visualizing Phase Heterogeneity and Defects in Cycled NMC622: From Ordered H1 to Disordered Hexagonal Phase Evolution

Ni‐rich lithium transition metal oxide (LiNi 0.6 Mn 0.2 Co 0.2 O 2 ) is a widely used cathode material due to its high energy density and good stability. However, structural changes occurring across multiple length scales, from the atomic to the electrode level, during battery cycling can significantly affect performance. In this study, we combine X‐ray diffraction, Raman mapping, and SEM and TEM imaging as a complementary approach for in‐depth and easily accessible electrode analysis. Ex situ characterization enables detailed investigation of structural phenomena within the electrode. Raman mapping reveals structural gradients within the electrode layer during charging and discharging. XRD data analysis reveals multiple phase transitions from H1 to H2, H2 to H3, and following by two disordered hexagonal phases during charging to high potentials. Additionally, we demonstrate the structural differences induced by the various charging strategies. SEM and TEM analyses show that 4.3 V cycling exhibits planar gliding, grain coarsening, and primary particle loosening, whereas cycling above 4.7 V additionally generates severe intragranular cracks and crystal bending. The integrated insights from XRD, Raman mapping, HR‐SEM and HR‐TEM advance the understanding of the delithiation and re‐lithiation mechanisms, phase evolution, phase gradients, unit cell, and morphological changes, thereby providing a deeper understanding of material characteristics and limitations under cycling conditions.