Rechargeable Al-Metal Aqueous Battery Using NaMnHCF as a Cathode: Investigating the Role of Coated-Al Anode Treatments for Superior Battery Cycling Performance

Rechargeable Al-ion aqueous batteries (AIABs) are emerging contenders for massive battery systems due to economic, abundance, environmental, and safety advantages. However, the high capacity of metallic-Al remains untapped due to native oxide barrier formation. Engineering oxide removal by treating Al metal with an ionic liquid mixture solves this problem but the role of this treated-Al (TAl) in influencing full-cell battery performance is not yet fully understood. At the same time, the stability and compatibility of the coating layer applied on Al metal remain unexplored for long-term handling in full-cell assembly lines. Here, we explore the above two aspects of TAl in the context of a full-cell AIAB. First, a highly stable cathode material, NMnHCF, is demonstrated to successfully store an Al-ion by reversibly transforming from the monoclinic to tetragonal phase. A high energy density surpassing previous equivalent reports has been reported. Second, it is revealed that combinations of electrolyte-TAl pairings significantly influence the overall battery performance, wherein electrolyte conductivity influences the Al plating/stripping overpotential, which in turn dictates the overall battery performance. We also document that chlorinated coatings on TAl are stable under ambient atmosphere for at least 40 h and prevent reoxidation of the bulk aluminum metal during battery fabrication and electrochemical cycling.