Carbothermal synthesis of SnxSb anode material for secondary lithium-ion battery

SnxSb alloy powders were synthesized by carbothermal reduction from SnO2 and Sb2O3 in Ar atmosphere above 850 °C. The synthesis process of SnxSb powders was characterized by differential thermal analysis (DTA) and X-ray diffraction (XRD). The particle feature and electrochemical property of synthesized SnxSb powders were evaluated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and galvanostatical cycling tests. The results indicated that with the increase of SnO2 content in raw powders, the completely reduced temperature of SnO2 and Sb2O3 mixture increased. A certain amount of Sb was detected in 1000 °C-synthesized SnxSb powder with pre-designated SnO2/Sb2O3 molar ratio of 2:1, while only SnSb intermetallic peaks were shown in XRD pattern of 900 °C-heated SnxSb powders with pre-designated SnO2/Sb2O3 molar ratio of 4:1. This is some inconsistent with Sn-Sb binary phase diagram. The evaporation of SnO2 during the heating process is considered to be responsible to this illogicality. The naturally cooled sample showed more fragile and easily to be crushed to submicrometer powders due to the polycrystalline microstructure characteristics of its particles, while quenched sample appeared to be much rigid attributable to its single-crystal particle feature. The synthesized SnxSb powders showed a higher charge and discharge capacity during the first several cycles compared with carbonaceous material.