H-Nb2O5 wired by tetragonal tungsten bronze related domains as high-rate anode for Li-ion batteries

Nb-based oxide is a promising candidate of high-rate anodes to develop high power Li-ion batteries and Li-ion capacitors. Compared with metastable bronze phase T-Nb2O5 with remarkable intercalation pesudocapacitance, commercially available high-temperature phase H-Nb2O5 is still of low-rate performance in view of the absence of Nb-O pentagonal bipyramids, an important moieties to construct desired room-and-pillar framework with open interconnected channels. Here we introduce a small fraction of tetragonal tungsten bronze (TTB) related KNb6O15F as conductive wires into H-Nb2O5 by simply doping KF. These KNb6O15F nano-sticks with NbO5F2 pentagonal bipyramids are electrochemically robust and of high rate performance themselves, contributing significant gain on capacity retention, rate endurance and capacitance effect for H-Nb2O5. The resultant rate performance is extraordinary with reversible capacities of 120, 100 and 80 mAh/g at 5 C, 10 C and 20 C respectively. In-situ wiring by phase segregation within a compact space based on correlated phase diagram appears to be a good solution to boosting of electron (or ion) flux especially when the wires are electroactive in the similar voltage zone.