Hierarchical T-Nb2O5 nanostructure with hybrid mechanisms of intercalation and pseudocapacitance for potassium storage and high-performance potassium dual-ion batteries

Potassium-ion batteries (KIBs) are promising alternative energy storage devices to lithium-ion batteries owing to the natural abundance and low cost of potassium as well as the low potential of K/K+. However, the lack of suitable electrode materials with fast kinetics of the larger K+ hinders wide applications of KIBs. Herein, nanostructured T-Nb2O5 was firstly investigated as an anode material for KIBs. Owing to the intercalation-pseudocapacitive hybrid mechanisms with fast kinetics and the hierarchical nanostructure, the T-Nb2O5 nanomaterial achieves good rate and cycling performance with a capacity of 104 mA h g(-1) at 0.4 A g(-1) and low decay of 0.068% per cycle for 400 cycles. Furthermore, utilizing the T-Nb2O5 nanowires as the anode, a novel potassium dual-ion battery (KDIB) is fabricated, which exhibits high rate performance with 81 mA h g(-1) even at 30C (91% capacity retention), and also achieves excellent cycling stability with a capacity retention of 86.2% after 1000 cycles at 20C, which is the best result for KDIBs reported so far.