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

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.