Construction of SiOx-SnO2 heterojunction and surface coating to achieve high-performance anode materials for lithium-ion batteries

Abstract

SiO_x (0 < x < 2) has been considered as one of the most promising anodes for lithium-ion batteries due to its high capacity and more stable cyclic charging and discharging performance, but it still has the drawbacks of lower intrinsic conductivity and larger volume expansion compared to graphite. For this purpose, Sn, a homologous element of Si, is selected in this paper, and the SiO_x@SnO₂ heterostructure is constructed on the SiO_x surface using simple solvothermal and calcination methods. The combination of DFT analysis and experimental results shows that the heterogeneous structure enhances the Si-O bond strength in SiO_x, and coupled with the localised stresses due to the lattice differences between SiO_x and SnO₂ alleviates the volume change of SiO_x during lithiation /de-lithiation. The reversible capacity was 536.8 mAh g^-1 after 300 cycles at 1C and 1152.4 mAh g^-1 after 200 cycles at 0.5C. The construction of SiO_x@SnO₂ heterojunction will also bring the Fermi energy levels into the valence band, which makes the material exhibit some metallic properties and improves the electrical conductivity enhancing the Li⁺ diffusion.