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 microspheres of the SiOx@SnO2@C ternary composite. Since lithiated SnO2 can significantly enhance the electrical conductivity of Si, SnO2 coating was constructed by growing SnO2 derived from hydrolyzed Na2SnO3in situ on the surface of nano silicon. Meanwhile, in the hydrolysis process of Na2SnO3, high amounts of OH− was generated, etching part of Si in SiO32−, which ultimately transformed to SiOx after the addition of citric acid. Compared with Si, the change in the volume of SiOx during the lithiation/delithiation process was smaller. After a simple hydrothermal treatment and subsequent carbonization, both SnO2 and SiOx nanoparticles were assembled into microspheres through Ostwald ripening. Thereby, the microspherical structure of the SiOx@SnO2@C ternary composite was formed, and the Si cores were uniformly embedded in the carbon layer containing SiOx and SnO2 with the carbon layer. Such a unique architecture that combines SiOx, SnO2 and amorphous carbon imparted great electrochemical properties. As a consequence, the SiOx@SnO2@C composite exhibited a reversible capacity of 796 mA h g−1 at a current density of 1 A g−1 even after 300 deep cycles, as well as a rate capacity of 515 mA h g−1 at a high current density of 4 A g−1.