Synthesis of the microspherical structure of ternary SiOx@SnO2@C by a hydrothermal method as the anode for high-performance lithium-ion batteries

Here, we report a simple and efficient hydrothermal approach to fabricate the ternary and microsphere structure of SiOx@SnO2@C composite. Since the lithiated SnO2 can significantly enhance electrical conductivity of Si, SnO2 coating is constructed by getting the SnO2, derived from hydrolyzed Na2SnO3, in-situ grow on the surface of nano silicon. Meanwhile, in the hydrolysis process of Na2SnO3, high amounts of OH- generate, etching part of the Si in SiO32-,which ultimately transforms to SiOx after adding citric acid. Compared to Si, the change in volume of SiOx during lithiation/delithiation process is smaller. After simple hydrothermal treatment and subsequent carbonization, both the SnO2 and SiOx nanoparticles are assembled into microspheres through Ostwald ripening. Thereby, the ternary and microsphere structure of SiOx@SnO2@C is formed, and Si cores have been uniformly embedded in the SiOx, SnO2 with carbon layer. Such unique architecture conbining SiOx, SnO2 and amorphous carbon together posesses greater electrochemical properties. As a consequence, the SiOx@SnO2@C composite exhibits a reversible capacity of 796 mAh g−1 at a current density of 1 A g−1 for 300th deep cycles, as well as a rate capacity of 515 mAh g−1 at a high current density of 4 A g−1.