Crucial contact interface of Si@graphene anodes for high-performance Li-ion batteries

Closely wrapped Si@graphene structure with improved contacting interface were synthesized by a facile compression method. The improved contacting interface have greatly enhanced the positive effect of graphene sheets on restraining the volume change of Si nanoparticles and improving the electronic conductivity. The obtained composite sample shows significantly improved electrochemical performance as anode material for Li-ion batteries. [Display omitted] •Closely wrapped Si@graphene structure with improved contact interface was synthesized by a facile compression method.•The improved contact interface has enhanced the effect of graphene on restraining the volume change of Si nanoparticles.•The composite sample shows significantly improved cycling stability and rate performance. Despite their extremely high capacity (4200 mA h g−1), the practical application of silicon anodes is still frustrated by their poor cycling performance, resulting from severe volume changes and pulverization of the electrode material. Introducing graphene in silicon is an ideal approach for addressing these issues. Nevertheless, the large size difference between Si and graphene makes high-quality contact difficult to realize, which severely harms the electrochemical performance of Si/graphene composites. Herein, a unique Si@graphene layer structure (p-Si@GN) with an improved contact interface is fabricated by a facile high-pressure method, in which the surfaces of silicon particles are closely covered by graphene layers, restraining the volume changes from multiple angles. The superior structure of the layered p-Si@GN composite exhibits multiple desired features for high-performance Si-based anodes, such as high Li+ storage capacity resulting from high-capacity Si nanoparticles, outstanding electron conductivity due to the formation of a continuous graphene conductive network, and excellent structural stability due to the enhanced protective function of graphene layers with an improved contact interface. Due to these advantages, the p-Si@GN40 anode, prepared under 40 MPa pressure, exhibits a significantly improved capacity of 2096.9 mA h g−1 at a current density of 300 mA g−1, an enhanced rate capability of 706.4 mA h g−1 at 3000 mA g−1, and superior cycling performance with a high capacity retention of 82.6 % after 150 cycles.