Abstract Graphitic multi‐walled carbon nanotubes (MWCNTs) can function as high‐performance cathode materials for rechargeable Al‐ion batteries with well‐defined discharging plateaus and reasonable charge/discharge C‐rates. However, the main intercalation/deintercalation or adsorption/desorption path of AlCl4− anions into or onto G‐MWCNTs has not been elucidated. Herein, we used battery cells comprised of G‐MWCNTs with different aspect ratios, Al metal, and AlCl3/1‐ethyl‐3‐methylimidazolium chloride ionic liquid as the cathode, anode, and electrolyte, respectively. The electrochemical performance of the Al||G‐MWCNT cell increased as the aspect ratio of the G‐MWCNT cathode increased (i. e., longer and thinner). The degree of defects of the G‐MWCNTs was similar (0.15–0.22); hence, the results confirm that the main and alternate paths for the AlCl4− intercalation/de‐intercalation or adsorption/desorption into/from or onto/from the G‐MWCNT are the basal and edge planes, respectively. The step‐like structures of defects on the basal plane provide the main reaction site for AlCl4− anions.
