Aluminum Foil Anodes for Li-ion Rechargeable Batteries: The Role of Li Solubility within β-LiAl

Li-ion battery (LIB) electrodes contain a substantial amount of electrochemically inactive materials, including binder, conductive agent, and current collectors. These extra components significantly dilute the specific capacity of whole electrodes, and thus have led to efforts to utilize foils, e.g., Al, as the sole anode material. Interestingly, the literature has many reports of fast degradation of Al electrodes, where less than a dozen cycles can be achieved. However, in some studies, Al anodes demonstrate stable cycling life with several hundred cycles. In this work, we present a successful pathway for enabling long-term cycling of simple Al foil anodes: β-LiAl phase grown from Al foil (α-Al) exhibits a cycling life of 500 cycles with a ~96% capacity retention when paired with a commercial cathode. The excellent performance stems from strategic utilization of the Li solubility range of β-LiAl that can be (de-)lithiated without altering its crystal structure. This solubility range at room temperature is determined to be ~6 at%. Consequently, this design circumvents the critical issues associated with the α/β/α phase transformations, such as volume change, mechanical strain, and nanopore formation. Application-wise, the maturity of aluminum industry, combined with excellent sustainability prospects, makes this anode an important option for future devices.