Charging and discharging of the electrochemically swelled, aligned carbon nanotube fibers

•ACNT fibers subjected to negative potentials undergo the process of swelling.•As a result of swelling, the dimension and active surface area of ACNTs are expanded.•Swelling can be associated with the accumulation of ions similar to intercalation.•The swollen ACNT fibers can be charged multiple times.•Manipulation with charging potentials allows one to tailor the discharging process.

Aligned carbon nanotube fibers are macroscopic materials with remarkable properties, such as high specific strength, stiffness, extreme flexibility as well as electrical and thermal conductivity. It is demonstrated that when subjected to negative potentials, these structures undergo the process of swelling in which the increase of their external dimension is observed. Swelling is believed to be caused by cation insertion in the process similar to intercalation. The efficiency of swelling was determined both in organic and aqueous solutions of different pH. Chronocoulometry was used as the technique to monitor the charging-discharging processes of swollen ACNT fibers in a presence of different electrolytes, i.e. LiCl, NaCl and KCl. The possibility of performing the charging-discharging cycles multiple times indicates that the swollen ACNT fibers can be considered as an advantageous material for electrodes in ion batteries and supercapacitors.