Electrochemical Performance of Graphitic Multi‐walled Carbon Nanotubes with Different Aspect Ratios as Cathode Materials for Aluminum‐ion Batteries

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 AlCl(4) (−) 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 AlCl(3)/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 AlCl(4) (−) 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 AlCl(4) (−) anions.