Niobium Carbide as a Promising Pseudocapacitive Sodium-Ion Storage Anode

Niobium carbide (NbC) is used as anode material for sodium-ion batteries for the first time. Ball-milled NbC delivers an initial charge capacity of 242 mAh g −1 at 0.1 A g −1 and a capacity of 126 mAh g −1 after 1000 cycles at a high current density of 5 A g −1 without carbon coating. Cyclic voltammetry curves demonstrate that the pseudocapacitive Na + storage behavior dominates the electrochemical reaction, which is responsible for the good rate capability. Ex situ X-ray diffraction (XRD), transmission electron microscopy (TEM), and density functional theory (DFT) calculations show that the electrochemical reaction between NbC and Na is attributed to an adsorption mechanism.