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

Abstract

Here, we report a simple and efficient hydrothermal approach to fabricate microspheres of the SiO_x@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 SiO_x after the addition of citric acid. Compared with Si, the change in the volume of SiO_x during the lithiation/delithiation process was smaller. After a simple hydrothermal treatment and subsequent carbonization, both SnO₂ and SiO_x nanoparticles were assembled into microspheres through Ostwald ripening. Thereby, the microspherical structure of the SiO_x@SnO₂@C ternary composite was formed, and the Si cores were uniformly embedded in the carbon layer containing SiO_x and SnO₂ with the carbon layer. Such a unique architecture that combines SiO_x, SnO₂ and amorphous carbon imparted great electrochemical properties. As a consequence, the SiO_x@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.