One-Dimensional Yolk-Shell Sb@Ti-O-P Nanostructures as a High-Capacity and High-Rate Anode Material for Sodium Ion Batteries.

Development of high energy/power density and long cycle life of anode materials is highly desirable for sodium ion batteries, because graphite anode cannot be used directly. Sb stands out from the potential candidates, due to high capacity, good electronic conductivity, and moderate sodiation voltage. Here, one-dimensional yolk-shell Sb@Ti-O-P nanostructures are synthesized by reducing core-shell Sb2O3@TiO2 nanorods with NaH2PO2. This structure has Sb nanorod as the core to increase the capacity and Ti-O-P as the shell to stabilize the interface between electrolyte and electrode material. The gap between the core and the shell accommodates the volume change during sodiation/desodiation. These features endow the structure outstanding performances. It could deliver a capacity of about 760 mA h g-1 after 200 cycles at 500 mA g-1, with a capacity retention of about 94%. Even at 10 A g-1, the reversible capacity is still at 360 mA h g-1. The full battery of Sb@Ti-O-P//Na3V2(PO4)3-C presents a high output voltage (∼2.7 V) and a capacity of 392 mA h g-1anode after 150 cycles at 1 A g-1anode.