Sandwich-like structure C/SiO_x@graphene anode material with high electrochemical performance for lithium ion batteries

Silicon suboxide (SiO_x, 0 < x < 2) is recognized as one of the next-generation anode materials for high-energy-density lithium ion batteries (LIBs) due to its high theoretical specific capacity and abundant resource. However, the severe mechanical instability arising from large volume variation upon charge/discharge cycles frustrates its electrochemical performance. Here we propose a well-designed sandwich-like structure with sandwiched SiO_x nanoparticles between graphene sheets and amorphous carbon-coating layer so as to improve the structural stability of SiO_x anode materials during cycling. Graphene sheets and carbon layer together construct a three-dimensional conductive network around SiO_x particles, which not only improves the electrode reactions kinetics, but also homogenizes local current density and thus volume variation on SiO_x surface. Moreover, Si–O–C bonds between SiO_x and graphene endow the strong particle adhesion on graphene sheets, which prevents SiO_x peeling from graphene sheets. Owing to the synergetic effects of the structural advantages, the C/SiO_x@graphene material exhibits an excellent cyclic performance such as 890 mAh/g at 0.1 C rate and 73.7% capacity retention after 100 cycles. In addition, it also delivers superior rate capability with a capacity recovery of 886 mAh/g (93.7% recovery rate) after 35 cycles of ascending steps at current range of 0.1–5 C and finally back to 0.1 C. This study provides a novel strategy to improve the structural stability of high-capacity anode materials for lithium/sodium ion batteries.