Functionalized N-Doped Carbon Nanotube Arrays: Novel Binder-Free Anodes for Sodium-Ion Batteries.

Boosting electrochemical sodium storage properties is achieved by utilizing functionalized N-doped carbon nanotube arrays (NCNAs) as anode materials. The NCNA anodes are first fabricated by self-polymerization of dopamine on cobalt hydroxide nanorod arrays as the template. The NCNAs with diameters of 100-120 nm are grown vertically to Ni foam, forming self-supported nanotube arrays. Such a structure has attractive advantages including large porosity and surface area, good electrical conductivity and mechanical strength. Consequently, the NCNAs are demonstrated to achieve excellent sodium storage performances with high capacity (335 mA h g at 100 mA g), good rate capability (140 mA h g at 2 A g), and superior capacity retention of 90.9% after 500 cycles. Especially, high performance is verified in the assembled full cells by using an NCNA anode and NaV(PO)/C cathode. The developed synthetic strategy provides an effective approach for the fabrication of advanced heteroatom-doped carbon-based electrodes for electrochemical energy storage.