Highly Fluorinated Interphase Enables the Exceptional Stability of Monolithic Al Foil Anode for Li‐Ion Batteries

Abstract Directly using aluminum (Al) foil as anode material offers a streamlined manufacturing process by eliminating the need for conductive additives, binders, and casting procedures. Nonetheless, monolithic Al foil anodes often suffer from mechanical failure and poor cyclability, posing challenges for practical adoption. In this study, a high‐concentration ether‐based electrolyte is employed to boost the durability of the Al foil anode. In contrast to traditional low‐concentration electrolytes, the use of 5 m lithium bis(fluorosulfonyl)imide in 1,2‐dimethoxyethane promotes the priority decomposition of anions, leading to the creation of a fluoride‐rich solid electrolyte interphase (SEI) layer with exceptional structural modulus and high ion conductivity. These outcomes, coupled with Al's superior compatibility in the chosen electrolyte, enable a record‐breaking cycle life of up to 400 cycles for Li//Al half‐cells, when operated at a high areal capacity of 1 mAh cm −2 . In full‐cell configurations, an outstanding capacity retention is also observed, with 96.9% after 150 cycles even under practical conditions involving a 40 µm thin Al foil and a 7.4 mg cm −2 LiFePO 4 cathode. These results not only mark the pioneering use of high‐concentration ether‐based electrolyte systems in Al foil anodes but also showcase the high potential for developing low‐cost and high‐energy Al foil‐based LIBs.