Simple synthesis of a porous Sb/Sb2O3 nanocomposite for a high-capacity anode material in Na-ion batteries

High-capacity anode materials are highly desirable for sodium ion batteries. Here, a porous Sb/Sb2O3 nanocomposite is successfully synthesized by the mild oxidization of Sb nanocrystals in air. In the composite, Sb contributes good conductivity and Sb2O3 improves cycling stability, particularly within the voltage window of 0.02-1.5 V. It remains at a reversible capacity of 540 mAh.g(-1) after 180 cycles at 0.66 A.g(-1). Even at 10 A.g(-1), the reversible capacity is still preserved at 412 mAh.g(-1), equivalent to 71.6% of that at 0.066 A.g(-1). These results are much better than Sb nanocrystals with a similar size and structure. Expanding the voltage window to 0.02-2.5 V includes the conversion reaction between Sb2O3 and Sb into the discharge/charge profiles. This would induce a large volume change and high structure strain/stress, deteriorating the cycling stability. The identification of a proper voltage window for Sb/Sb2O3 paves the way for its development in sodium ion batteries.