Novel Bimetallic Activated Center Alloying Mechanism Positive Electrodes for Aluminum Storage

Abstract Aluminum is the most abundant metal element in the Earth's crust, thus developing the rechargeable aluminum‐ion batteries (AIBs) provides an ideal opportunity to realize cells with pleasing energy‐to‐price ratios. However, the further development of AIBs is plagued by the scarcity of suitable positive electrode materials. Here, for the first time, a tin‐based alloy positive electrode material for AIBs, Co ₃ Sn ₂ wrapped with graphene oxide (Co ₃ Sn ₂ @GO composite) is well‐designed and investigated to understand the aluminum storage behavior. A series of experimental measurements and theoretical calculations results reveal that a novel “bimetallic activated center alloying reaction” aluminum storage mechanism is occurred on the prepared Co ₃ Sn ₂ positive electrode. The reversible alloying/de‐alloying process in AlCl ₃ /[EMIm]Cl ionic liquid, where both Co and Sn in Co ₃ Sn ₂ alloys react electrochemically with Al ³⁺ to form Al _x Sn and Al _y Co is first put forward. This study delineates new insights on the aluminum storage mechanism, which may guide to ultimately exploit the energy benefits of “bimetallic activated center alloying redox”.