Multivariate hyperspectral data analytics across length scales to probe compositional, phase, and strain heterogeneities in electrode materials

Authors: David A. Santos, Justin L. Andrews, Binbin Lin, Luis R. De Jesus, Yuting Luo, Savannah Pas, Michelle A. Gross, Luis Carillo, Peter Stein, Yu Ding, Bai-Xiang Xu and Sarbajit Banerjee

The origins of performance degradation in batteries can be traced to atomistic phenomena, accumulated at mesoscale dimensions, and compounded up to the level of electrode architectures. Hyperspectral X-ray spectromicroscopy techniques allow for the mapping of compositional variations, and phase separation across length scales with high spatial and energy resolution. We demonstrate the design of workflows combining singular value decomposition, principal-component analysis, k-means clustering, and linear combination fitting, in conjunction with a curated spectral database, to develop high-accuracy quantitative compositional maps of the effective depth of discharge across individual positive electrode particles and ensembles of particles. Using curated reference spectra, accurate and quantitative mapping of inter- and intraparticle compositional heterogeneities, phase separation, and stress gradients is achieved for a canonical phase-transforming positive electrode material, α-V₂O₅. Phase maps from single-particle measurements are used to reconstruct directional stress profiles showcasing the distinctive insights accessible from a standards-informed application of high-dimensional chemical imaging.
In the subsequent structural assessment, the predicted Young’s modulus is employed in the buckling and vibration analyses of FG porous beams, which are constructed by a six-layer laminated beam model and consist of high-, medium-, and low-density layers with varying designated relative densities. The Timoshenko beam theory and the Ritz method are applied to derive and solve the governing equations. Convergence and validation studies are performed accordingly to ensure the validity of presented results, followed by a parametric study to examine various FG beams concerning different porosity distributions, boundary conditions, and slenderness ratios. The prominence of graded porosities is evidenced by apparently promoted beam stiffness with over 30% and 10% increments in the critical buckling load and fundamental natural frequency, respectively. The graded porosities can be linked to realistic closed-cell Aluminium foams with developed quantitative relations, shedding important and practical guidance into the porous structural design.

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