Nanoscale Phase Engineering in Two-Dimensional Niobium Pentoxide Anodes toward Excellent Electrochemical Lithium Storage

Niobium pentoxide (Nb2O5) material is a promising anode for lithium-ion batteries (LIBs) due to the outstanding cycle performance and rate capability. However, the relatively low capacity severely limits the comprehensive performance. Generally, nanoscale engineering of the morphology and chemical composition of Nb2O5 anodes is employed to improve electrochemical lithium storage. In this work, we promote the reservable capacity of a sheetlike Nb2O5 anode by designing nanoscale phase interfaces between the nanodomains of T-Nb2O5, M-Nb2O5, and H-Nb2O5 phases, which are generated by good control over the calcination of Nb3O7F precursor at high temperatures. Microstructural and chemical analyses show that the sample calcined at 750 °C (Nb2O5-750) has optimized structural advantages to efficiently store lithium ions. When evaluated as anodes for LIBs, the Nb2O5-750 sample shows excellent lithium storage properties. In specific, the Nb2O5-750 electrode delivers a reversible capacity of 270.4 mAh g-1 at 1C after 200 cycles. At a high rate of 5C, the Nb2O5-750 electrode has a reversible capacity of 174 mAh g-1 after 800 cycles. This work provides an alternative way to improve the ion storage in the electrodes with intrinsic polymorphic structures.