Abstract:

Sodium-ion batteries (SIBs) have recently garnered considerable attention because of the greater abundance, wider distribution, and lower cost of Na compared to Li. However, the investigation is insufficient, mainly because Na⁺ is larger and heavier than Li⁺, thereby limiting the Na⁺ insertion and extraction ability from the host materials. Anodes with alloying reactions such as Sn, Ge, and Sb have been considered for SIBs owing to their high gravimetric and volumetric specific capacities. In this study, we devised a one-pot reaction strategy for the in-situ fabrication of a spherical porous nano-SnSb/C composite by employing aerosol spray pyrolysis, and subsequently applied it as an anode in SIBs. The products of spray pyrolysis generally feature three-dimensional spherical hierarchical structures, which are considered to be relatively stable and also act as high-packing-density electrode materials. Additionally, they can be easily handled during the fabrication of the electrode. By adjusting the precursor concentration of SnCl₂·2H₂O and SbCl₃, different sizes for SnSb nanoparticles (10 and 20 nm) were obtained. The crystal structures and morphologies of the as-prepared samples were characterized using X-ray diffraction, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. Thermal gravimetric analysis was carried out to analyze the carbon content of SnSb/C composites by using a TG-DSC analyzer with a heating rate of 5 ℃·min^-1 in air from 25 ℃ to 600 ℃. The specific surface areas of the microspheres were determined by Brunauer-Emmett-Teller analysis. X-ray photoelectron spectroscopy and Raman spectroscopy were used to investigate the studied materials. The micro-nanostructured composite is composed of SnSb nanoparticles (10 and 20 nm); moreover, the carbon content and size of SnSb nanograins could be controlled by altering the reaction conditions. Owing to its unique structure, the obtained nano-composite displays stable cycle performance and high rate capability as the anode for SIBs. The specific capacity of 10-SnSb/C was 722.1 mAh·g^-1 at the first cycle, and the coulombic efficiency of the first cycle was 86.3%. The 10-SnSb/C was stable at different current densities of 100, 1000, and 3000 mA·g^-1, and exhibited specific capacities of 607.7, 645.4 and 452.2 mAh·g^-1, respectively. The reversible capacity reached 623 mAh·g^-1 after 200 cycles at a current density of 1000 mA·g^-1, and the capacity retention rate was 95%. The outstanding performance of SnSb/C was due to its distinctive nanostructure, which could effectively improve the utilization rate of active materials, facilitate the transportation of Na⁺ ions, and prevent the nanoparticle pulverization/agglomeration upon prolonged cycling. The facile synthesis technique and good performance would shed light on the practical development of SnSb/C nanocomposites as high rate capability and long cycle life electrodes for SIBs.

Key words: SnSb alloy, Sodium-ion battery, Anode material, Spray pyrolysis