F-doped orthorhombic Nb2O5 exposed with 97% (100) facet for fast reversible Li+-Intercalation

Orthorhombic Nb2O5 (T-Nb2O5) is attractive for fast-charging Li-ion batteries, but it is still hard to realize rapid charge transfer kinetics for Li-ion storage. Herein, F-doped T-Nb2O5 microflowers (F-Nb2O5) are rationally synthesized through topotactic conversion. Specifically, F-Nb2O5 are assembled by single-crystal nanoflakes with nearly 97% exposed (100) facet, which maximizes the exposure of the feasible Li+ transport pathways along loosely packed 4g atomic layers to the electrolytes, thus effectively enhancing the Li+-intercalation performance. Besides, the band gap of F-Nb2O5 is reduced to 2.87 eV due to the doping of F atoms, leading to enhanced electrical conductivity. The synergetic effects between tailored exposed crystal facets, F-doping, and ultrathin building blocks, speed up the Li+/electron transfer kinetics and improve the pseudocapacitive properties of F-Nb2O5. Therefore, F-Nb2O5 exhibit superior rate capability (210.8 and 164.9 mAh g−1 at 1 and 10 C, respectively) and good long-term 10 C cycling performance (132.7 mAh g−1 after 1500 cycles).