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 NCNAs anodes are firstly fabricated by self-polymerization of dopamine on cobalt hydroxide nanorods arrays as template. The NCNAs with diameters of 100-120 nm are grown vertically to Ni foam forming self-supported nanotube arrays. Such structure has attractive advantages including large porosity & surface area, good electrical conductivity & mechanical strength. Consequently, the NCNAs are demonstrated with excellent sodium storage performances with high capacity (335 mAh g-1 at 100 mA g-1), good rate capability (140 mAh g-1 at 2 A g-1) and superior capacity retention of 90.9 % after 500 cycles. Especially, high performance is verified in the assembled full cells by using NCNAs anode and Na3V2(PO4)3/C cathode. The developed synthetic strategy provides an effective approach for fabrication of advanced heteroatom-doped carbon-based electrodes for electrochemical energy storage.