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.