Oxygen-deficient polymorphic Nb2O5 micro/nanoscale three-dimensionally interconnected anodes with enhanced rate capability for lithium storage

Abstract

Niobium pentoxide (Nb 2 O 5 ) anodes have attracted much attention as a candidate for the next generation lithium-ion batteries (LIBs) due to the unique physical and chemical properties. However, some critical issues, like low electronic conductivity, inefficient ionic diffusion, must be addressed before practical applications. In this work, we employed a facile NaBH 4 engaged chemical reduction method to modify Nb 2 O 5 anodes. Microstructure and surface chemistry analysis indicated that the Nb 2 O 5 materials have micro/nanoscale three-dimensionally interconnected morphology, and contain three different phases (T-, M-, and H-Nb 2 O 5 ). More importantly, oxygen vacancies are introduced by the NaBH 4 reduction treatment, and the oxygen vacancy amount can be modulated by changing the NaBH 4 concentration. As anodes for LIBs, the optimized sample exhibited a reversible capacity of 252.2 mAh·g −1 after 100 cycles at a current density of 1 C, and a reversible capacity of 139.4 mAh·g −1 at a large current density of 10 C. The electrochemical performance enhancement can be attributed to the combination of multiscale structural design, i.e., oxygen vacancy, nanoscale phase interface, and micro/nanoscale three-dimension assembly. We expect the present synergistic strategy can be employed to manipulate the key structures in different functional materials for broader applications. ● Oxygen vacancies are generated in polymorphic Nb 2 O 5 anodes. ● The optimised anode shows excellent lithium storage performance. ● The improved performance is due to the synergistic multiscale structural design.