Competitive\nLithiation Mechanism of Silicon in Aluminum–Silicon\nAlloy Foil Anodes for Lithium-Ion Batteries

Alloying-type foil anodes have garnered interdisciplinary\nattention\nfor the development of future high-energy-density lithium-ion batteries\n(LIBs). However, the relative research is still in the infant stage,\nwith many unexplored mechanisms regarding uneven lithiation, sluggish\nlithiation kinetics, low Coulombic efficiency, severe stress concentration,\nand rapid mechanic-electrochemical failure. Herein, we investigate\nthe electrochemical behavior, corresponding microstructure variation,\nand phase transition process of aluminum (Al)–silicon (Si)\nalloy foils to elucidate the intricate interplay between Al and Si\nduring lithiation/delithiation processes, on the basis of which a\nmechanism of competing lithiation of Si in the anode of Al–Si\nalloy foils for LIBs is proposed. During partial lithiation/delithiation,\nAl primarily governs the process due to its high electrical conductivity\nand alloying plateau advantage, whereas precipitated crystalline Si\nprovides phase boundaries (PBs) that effectively enhance lithiation\nkinetics without any capacity contribution. However, Si particles\nplay diverse roles in the first full lithiation and the subsequent\ncycling, from providing PBs to directly participating in lithiation,\ninfluencing the overall performance of the Al–Si foils. This\ncomprehensive understanding of the competitive lithiation mechanism\nsheds light on optimizing the design and engineering of Al–Si\nalloy foil anodes, potentially leading to enhanced performance and\nlongevity in LIBs with high energy density.