Suppressing vertical aluminum growth via accelerated interfacial Cl − dynamics for high‐areal‐capacity, long‐life aluminum metal anodes

Abstract Despite the high theoretical volumetric capacity of aluminum metal anodes (AMAs), their practical use in rechargeable aluminum batteries (RABs) is hindered by low capacity utilization and short‐circuit‐induced cell failure. Herein, we investigate the aluminum nucleation and growth behavior on a 2D electrode platform to uncover the origins of such failures, integrating experimental analysis with theoretical calculations. We find that the failure capacity is strongly dependent on separator thickness, irrespective of separator type. Short‐circuiting arises from unfavorable multi‐step reactions, where inefficient Cl − removal promotes vertical Al growth due to localized accumulation of reaction products. Based on these insights, we design a 3D nanostructured graphitic carbon electrode (3D‐GCE) to mitigate local AlCl 4 − buildup and enhance Al reversibility. Additionally, a Cl‐doped polypropylene (Cl‐PP) separator is employed to facilitate Cl − transport via the Grotthuss mechanism. This integrated design achieves a record capacity of ~8.2 mAh cm −2 and stable cycling over 500 cycles with a single thin PP separator. image