Construction of a Flexible Nb₂O₅/Carboxyl Multiwalled Carbon Nanotube Film as Anode for Lithium and Sodium Storages

Considering that Nb2O5 has good safety performance, high capacity, and rich redox couples (Nb5+/Nb4+ and Nb4+/Nb3+), it can be considered as a prospective anode material. However, the inherent poor conductivity of Nb2O5 and the structural damage caused by pulverization hinder their applications. Herein, we designed a flexible Nb2O5/carbon nanotube film (NCNTF) using Nb2O5-decorated carboxyl carbon nanotubes through a facile hydrothermal treatment and vacuum filtration process. Benefiting from its unique structural characteristics, the flexible composite film not only shortens the ions/electrons transmission paths, enhances conductivity, and structural stability but also relieves the large volume changes of Nb2O5 nanoparticles caused by Na+/Li+ insertion/extraction during charging and discharging. The binder-free NCNTF also has excellent electrochemistry storage performance based on simplifying the electrode preparation process. As for lithium-ion batteries, the NCNTF electrode delivers a specific capacity of 382 mAh g–1 after 100 cycles at 0.1 A g–1, and even at 1.0 A g–1, the capacity of 290 mAh g–1 can still be obtained. As for sodium-ion batteries, the NCNTF electrode shows a capacity of 220 mAh g–1 over the same number of cycles as above at 0.1 A g–1.