Microstructure-driven electro-chemo-mechanical behavior and degradation pathways in Si-Al based alloy anodes with different Al contents

초록

Silicon (Si) offers very high capacity for lithium-ion battery anodes, but severe volume-change-driven damage limits cycle life. Although nanostructured Si can mitigate pulverization, its complex and costly processing hinders scalable use. Here, we demonstrate a post-treatment-free approach in which water-atomized Si-Al-based alloy powders are directly used as anode active materials. By tuning the Al content, three alloys with distinct rapidly solidified microstructures were produced, and their electro-chemo-mechanical degradation was examined using cross-sectional SEM, in situ electrochemical dilatometry, TEM-based phase analysis, and nanoindentation. With increasing Al content, the powders exhibit apparent refinement of Si-rich domains; however, cycling stability does not improve, indicating that refinement alone is insufficient for atomized Si alloy anodes. Instead, durability is governed by the stability and electrochemical reactivity of the metallic matrix. The Si-rich alloy primarily shows degradation consistent with progressive SEI-related losses, whereas the Al-rich alloys undergo rapid capacity fade associated with lithiation of the Al-containing matrix (LiAl formation), which promotes deformationdriven damage, cracking, and electrical disconnection. These results suggest a processing-composition trade-off for scalable Si-Al based alloy anodes: Al can assist microstructure refinement during atomization, but excessive Al increases matrix participation and accelerates mechanically driven failure.

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