Gliding-Induced Stacking Faults in Layered Oxide Cathode

Abstract In layered oxide cathodes, the utilization of high states of charge inevitably triggers complex phase transitions, accompanied by significant translational symmetry breaking. Although in situ X-ray diffraction has long been employed to monitor these transitions, quantitatively resolving the stochastic nature of planar defects remains a formidable challenge. In this work, we establish a robust analytical framework that correlates stacking faults with diffraction patterns, enabling the quantitative elucidation of one-dimensional stacking disorder. Taking the prototypical P2-to-O2 transition as a model, we demonstrate that this phase transition is a highly dynamic evolution governed by stochastic interlayer gliding. Through combined theoretical and experimental analyses, we reveal that the P2-to-O2 transition proceeds via an interlayer-asynchronized route, featuring an ordered OP6 intergrowth phase at the midpoint, which is an intermediate structure frequently misidentified as OP4 in the literature due to neglected unit cell periodicity constraints. Furthermore, by constructing and validating structural models that explicitly account for stacking defects, we establish a quantitative link among layer gliding, local coordination evolution, and subsequent transition-metal migration. Ultimately, the established descriptor framework serves as a standardized baseline amidst intricate structural evolutions, enabling the precise description and quantitative comparison of phase transition behaviors.