Abstract
Sodium ion battery (SIB) is a promising candidate for large-scale and practical application because of its lower costs and widespread of sodium resource.1 However, for SIBs, the intrinsic difference between sodium and lithium (ca. 55% larger and 330% heavier) lead to slower kinetics and lower energy densities.1 Nevertheless, it is reported that the enhance SIBs performance could be obtained by introducing the proper sodium host.2 For example, recent advances indicated that the ordered mesoporous Nb2O5-C delivered a reversible capacity of ~175 mA h/g and excellent cycle stability (up to 300 cycles).3 However, the low rate performance (<100 mA h/g at rate of 1A/g) cannot meet the requirements of fast charge-discharge electrochemical devices. In this work, ultrafine Nb2O5 nanocrystal/reduced graphene oxide (Nb2O5/rGO) was demonstrated as a promising anode material for sodium ion battery with high rate performance and high cycle durability. The Nb2O5/rGO was synthesized by controllable hydrolysis of niobium ethoxide and following treated at high annealing temperature in forming gas. Transmission electron microscopy (TEM) showed that ultrafine Nb2O5 nanocrystal with average particle size of 3 nm was uniformly deposited on rGO. Highly conductive rGO network and ultrafine Nb2O5 not only can enhance charge transfer and buffer the volume change during sodiation/desodiation process, but also could provide more active surface area for sodium ion storage, resulting in superior rate performance and cycle performance. XPS and XRD analyses revealed that the sodium ion storage mechanism in Nb2O5 could be accompanied with Nb5+/Nb4+ redox reaction and the ultrafine Nb2O5 nanocrystal provide more surface area to finish the redox reaction. Reference: 1. N. Yabuuchi, K. Kubota, M. Dahbi and S. Komaba, Chemical Reviews, 2014, 114, 11636-11682. 2. Y.-U. Park, D.-H. Seo, H.-S. Kwon, B. Kim, J. Kim, H. Kim, I. Kim, H.-I. Yoo and K. Kang, Journal ofthe American Chemical Society, 2013, 135, 13870-13878. 3. H. Kim, E. Lim, C. Jo, G. Yoon, J. Hwang, S. Jeong, J. Lee and K. Kang, Nano Energy, 2015, 16, 62-70.
Published Version
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