Enhancing the durability of aluminium-foil anodes in rechargeable lithium batteries via uniformly distributed alloy addition in the matrix phase

Abstract

Al-foil anodes suffer from self-reinforcing pulverization and surface passivation in liquid electrolytes, which significantly limit their cyclability. From the perspective of structural materials, alloy additions to the Al matrix present a promising strategy for managing morphological changes to enhance the performance of Al-foil anodes. However, establishing design guidelines requires a clear understanding of the underlying mechanisms. In this study, we focus on Si, a typical alloy addition known for strengthening Al alloys, and prepare Al-xSi foils (x = 0–4 wt%) to investigate how Si distribution influences reaction behavior and electrode properties. At low concentrations (x < 1%), Si is uniformly distributed in the Al matrix as a solid solution. At higher concentrations (1% < x < 4%), Si tends to agglomerate into large, micrometer-sized Si particles. During electrode reactions, uniformly distributed Si in the Al matrix is prone to forming amorphous Li–Si(-Al) domains during lithiation, preventing cracks in the recrystallized Al phase during subsequent delithiation. In contrast, agglomerated Si particles have negligible effects on the reaction behavior of Al-xSi foil anodes. With the highest amount of uniformly distributed Si, Al-1%Si shows a stable interface with a limited surface area increase, resulting in superior cyclability in full cells with LiCoO₂ cathodes. On the other hand, the limited interface restricts the kinetics of Li extraction, causing irreversible capacity loss, which needs further improvement to facilitate bulk diffusion in the matrix.