Inhibiting inter-layer gliding in transition metal layered oxides through interphase engineering for sodium-ion batteries

Inter-layer gliding induced phase transitions are widely recognized as the predominant cause of performance degradation in layered oxide positive electrode materials utilized in Na/Li-ion batteries. However, effectively restraining these phase transitions at a fundamental level poses a significant challenge. In this study, we elucidate that gliding at the X2/Y3 (X, Y = P or O) interphase layer can be thermodynamically inhibited through an energetically driven gliding-inhibition mechanism, by systematic structural analysis and correlated energy calculations. Building upon this insight, we propose interphase engineering as an effective approach to mitigate phase transitions. The resulting P2/P3-Na_0.46Mn_0.9Ni_0.1O₂ material, featuring dense and uniform P2/P3 interphases, exhibits notable enhancements in both cycling stability and rate capability. Detailed structure probing conducted through advanced atomic-level electron microscopy and synchrotron X-ray diffraction corroborates the role of the P2/P3 interphase structure in suppressing gliding and phase transition. Furthermore, the widespread applicability of the X2/Y3 interphase concept is validated through the successful implementation in several other extended X2/Y3 interphase materials. These findings provide further understanding of interphase phenomena and suggest a strategy to suppress phase transition in layered positive electrode materials.