Bulk Electronic Transformations in Si–Ge Alloys during Lithiation Probed by Si L2,3-edge X-ray Raman Scattering

Abstract Silicon–germanium alloys are promising high-capacity anode materials for lithium-ion batteries, yet their lithiation mechanisms remain only partially understood due to the limitations of conventional characterization techniques. In this work, Si L2,3-edge X-ray Raman scattering (XRS) is combined with Finite Difference Method Near Edge Structure (FDMNES) multiple-scattering calculations to investigate micron/submicron ball-milled and nanosized laser-pyrolyzed Si0.5Ge0.5 electrodes during the first lithiation cycle. Explicit SiGe and Li-rich Si–Ge structural models reveal a pronounced influence of Ge on the Si L2,3-edge line shape in the pristine state, whereas this effect becomes much less evident after lithiation. The Li-rich spectra of both materials are consistently described using the Li15(SiGe)4 model, while the different effective screening values required for BM and LP are interpreted as model-dependent descriptors of their local electronic environments rather than as quantitative measures of charge transfer. The broad intensity observed in the 103–109 eV region is consistent with overlapping contributions of the alloy electronic structure and oxidized Si environments, rather than being attributable to a unique lithiated species. These results demonstrate that Si L2,3-edge XRS, supported by explicit alloy modeling, provides a bulk-sensitive probe of electronic transformations in Si–Ge anodes and highlights the combined influence of alloying, morphology, and lithiation on the Si electronic response.