Speaker
Description
Improving the performance of rechargeable batteries in terms of energy density, lifetime, and reliability requires a detailed understanding of the electrochemical processes governing electrode behaviour at the atomic and electronic scales. Charge compensation in layered oxide cathodes typically involves multiple redox-active centres, most notably transition metals such as Mn and Ni, whose relative contributions evolve throughout cycling and are difficult to disentangle using single-edge or single-technique analyses.
Here, we present a correlative operando framework that tracks the coupled evolution of Mn and Ni redox activity by applying Multivariate Curve Resolution (MCR) to X-ray Absorption Spectroscopy (XAS) data. Operando Mn and Ni K-edge XAS datasets are each independently decomposed via MCR into chemically meaningful spectral components and their associated concentration profiles. These profiles are then time-synchronized and plotted against one another, allowing the Mn-Ni relationship to be read directly from the shape of the resulting trajectory: periods of coordinated redox activity appear as linear segments, with the slope reflecting the relative rate of Mn versus Ni evolution, while periods in which one metal remains redox-inactive while the other continues to evolve appear as flat, decoupled segments.
Applied to Li- and Na-based layered oxides, this approach reveals a sequence of distinct linear regimes with characteristic slopes, separated by transitions that mark changes in charge-compensation mode across the state of charge, features that are not evident from absolute spectral analysis of either edge alone. We demonstrate this across 14 operando datasets generated through extensive, long-term worldwide collaborations, showing that by working in the space of relative component coevolution rather than absolute spectral change, this correlative MCR approach is inherently robust to experimental noise and material-specific spectral features, offering a transferable intermediate step between raw operando data and mechanistic interpretation of redox dynamics in battery electrodes.