Highly [001]-oriented N-doped orthorhombic NbO microflowers with intercalation pseudocapacitance for lithium-ion storage.

Orthorhombic NbO (T-NbO), a typical intercalation pseudocapacitor, is favorable for realizing high power and energy density for lithium-ion batteries; furthermore, the 2D layered channels perpendicular to the [001] direction facilitate fast Li intercalation in T-NbO. Herein, N-doped T-NbO microflowers (N-NbO) assembled from highly [001]-oriented nanoflakes are rationally synthesized using NHF as the nitrogen source and capping agent. It is found that NH can adsorb on the O-terminated (010) plane of T-NbO N-H⋯O hydrogen bonds, which is highly conducive to the generation of 1D nanorods and the subsequent fusion of the nanorods into highly [001]-oriented nanoflakes. The special growth orientation of the T-NbO nanoflakes endows them with abundant available Li intercalation channels; moreover, the bandgap of N-NbO is narrowed (∼2.91 eV) owing to the doping of N atoms, and the intrinsic electronic conductivity is improved. Accordingly, the intercalation pseudocapacitive behavior of N-NbO is notably promoted and N-NbO exhibits superior Li storage properties, including large discharge capacity (214.7 mA h g at 1C), excellent rate capability (203.7 and 174.6 mA h g at 1 and 20C), and superior cyclic stability (150.7 mA h g at 10C after 1000 cycles). In addition, the LiNiMnCoO//N-NbO full cell delivers outstanding Li storage performance, especially in terms of long-term cycling (126.2 mA h g at 10C after 3500 cycles).