With the rapid growth in various advanced technologies such as microelectronics, development of high energy and high power energy storage devices is very essential to power portable electronic devices and the the demand is even more pressing to meet the higher end energy needs for vehicular and large-scale grid storage applications. Lithium ion batteries continue to serve as an excellent choice amongst electrochemical energy storage devices for several decades. However, because of the low abundance and increasing demand for lithium metal, a competent alternative for lithium-ion batteries is being sought after, for quite some time now. Among these alternatives, sodium ion battery (SIB) turns out to be a wise choice, owing to the high abundance of sodium on Earth’s crust, suitable redox properties and similar electrochemical behaviour as that of lithium.^[1] Though research on SIBs have started in 1970’s, increasing interest on these systems gained attention over the last few years. Several novel cathode materials have been studied for SIBs in recent years,^[2] however, development of efficient anode materials remain a big challenge for the successful implementation of Na-ion battery technology. In the continued search for anodes for SIBs, metal and metal-oxide materials are of great interest because of their potential to deliver high, and stable specific capacities. In particular, antimony-based materials (Sb, Sb₂O₃) have attracted recent attention due to their high theoretical capacities (660 mAh/g for Sb)^[3]. Antimony trioxide (Sb₂O₃), compared to other metal oxides is unique in such a way that the typical volume expansion issue occurring due to sodiation, gets addressed by the formation of a Na₂O ‘buffer matrix’ during the coupled conversion-alloying reaction^[4]. Herein, we have synthesized Sb₂O₃ microstructures that exhibits a unique star-shaped morphology, through hydrothermal method. As-synthesized Sb₂O₃ has been characterized by using powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Detailed studies on its electrochemical performance as anode material for sodium ion batteries have been carried out by using cyclic voltammetry (CV), galvanostatic charge/discharge cycling and electrochemical impedance spectroscopy (EIS) vs. sodium metal electrode in a standard electrolyte of 1 M NaClO₄ in propylene carbonate (PC). The as-synthesized Sb₂O₃ electrode delivered a stable specific capacity of 510 mAh/g for 30 cycles, at a current rate of 50 mA/g. In order to enhance both the specific capacity and the cycling stability, a graphene network that completely encapsulates Sb₂O₃ microstructures, forming a 3D interconnected network around it, has also been synthesized and tested as anode for sodium-ion batteries. The composite electrode of graphene-Sb₂O₃ hydrogel, prepared through simple hydrothermal route, showed excellent rate performance owing to the synergistic effects of highly conducting and interconnected graphene networks along with the pristine high capacity Sb₂O₃microstructures. The results are discussed and the key challenges will be addressed. The whole approach appears to be quite promising towards fabricating high performance anodes for Na-ion batteries.

References

 

[1] N. Yabuuchi, K. Kubota, M. Dahbi, and S. Komaba. Chem. Rev., 114, 11636 (2014).

[2] D. Buchholz, A. Moretti, R. Kloepsch, S. Nowak, V. Siozios, M. Winter,

      and S. Passerini, Chem. Mater., 25, 142 (2013).

[3] N. Li, S. Liao, Y. Sun, H. W. Song, and C. X. Wang. J. Mater. Chem. A, 3, 5820 (2015).

[4] M. Hu, Y. Jiang, W. Sun, H. Wang, C. Jin, and M. Yan, ACS Appl. Mater. Interfaces, 6, 19449  

     (2014).