Spherical nano-Sb@C composite as a high-rate and ultra-stable anode material for sodium-ion batteries

An aerosol spray pyrolysis technique is used to synthesize a spherical nano-Sb@C composite. Instrumental analyses reveal that the micro-nanostructured composite with an optimized Sb content of 68.8 wt% is composed of ultra-small Sb nanoparticles (10 nm) uniformly embedded within a spherical porous C matrix (denoted as 10-Sb@C). The content and size of Sb can be controlled by altering the concentration of the precursor. As an anode material of sodium-ion batteries, 10-Sb@C provides a discharge capacity of 435 mAh·g^–1 in the second cycle and 385 mAh·g^–1 (a capacity retention of 88.5%) after 500 cycles at 100 mAh·g^–1. In particular, the electrode exhibits an excellent rate capability (355, 324, and 270 mAh·g^–1 at 1, 000, 2, 000, and 4, 000 mA·g^–1, respectively). Such a high-rate performance for the Sb-C anode has rarely been reported. The remarkable electrochemical behavior of 10-Sb@C is attributed to the synergetic effects of ultra-small Sb nanoparticles with an uniform distribution and a porous C framework, which can effectively alleviate the stress associated with a large volume change and suppress the agglomeration of the pulverized nanoparticles during prolonged charge-discharge cycling.