ABSTRACT Aluminum metal is a reliable material for use as aluminum-ion battery (AIB) anodes due to its sustainable cycle. However, there have been conflicting studies regarding dendrite growth on aluminum foil surfaces. This study aims to clarify this issue by characterizing aluminum foil anodes with varying molar ratios of AlCl 3:EMIC ionic liquid electrolyte for AIBs. The results show that when aluminum foils were immersed in these electrolytes, acidic conditions damaged the natural oxide layer of aluminum foils, and this was more severe after cycling tests. The Al K-edge XAS and XPS spectra indicate the native oxide of Al foils was oxidized to amorphous aluminum oxide. After cycling, deposition of an oxidized layer occurred on the aluminum surfaces in basic conditions in which anions are incorporated into the oxide structure. This deposition was not observed on cycled Al in acidic electrolytes. The current work provides novel understanding of interfacial interaction between electrolytes and Al metal that can be a guideline to design non-aqueous AIBs with electrochemical stability.