Aluminum–Silicon Alloy Foils as Low-Cost, Environmentally Friendly Anodes for Lithium-Ion Batteries

Aluminum foils are highly promising anode materials for enabling next-generation Li-ion batteries that are simultaneously low-cost, environmentally friendly, and high-performing. However, the practical application of Al foil anodes has been hindered by the issues of low Coulombic efficiency and rapid mechanical failure, leading to poor cycle life. Here, we demonstrate the positive effect of as low as 1% silicon addition (Al99.0Si1.0) on the performance of a free-standing, aluminum foil anode. The Al99.0Si1.0 foil anode displays substantial improvements in both cycle life (>100 cycles) and Coulombic efficiency (>99.5%) compared to pure Al in both half-cells and full cells paired with a LiFePO4 cathode. Ex situ morphological analysis with scanning electron microscopy reveals the formation of a large, interconnected network of deep cracks in Al99.0Si1.0 after the initial cycle, generating nanostructured, porous aluminum "islands" supported by a pristine, unreacted aluminum substrate. We believe that this highly stable structure allows for facile lithium transport and has the capability to freely expand/contract without isolation from the base foil, preventing rapid mechanical failure of the electrode. Our results demonstrate the potential of Al–Si alloy foil anodes as a low-cost, sustainable battery material, and the study will stimulate further exploration of Al-alloy foil anodes.