Three-dimensional porous carbon skeleton supporting Si nanosheets as anode for high-performance lithium ion batteries

Si nanosheets (NSs) are synthesized by the arc-discharge plasma and successfully anchored onto the surface of porous carbon (PC) substrate via physical adhesion assisted with ultrasonic blending. The PC matrix is obtained by high-temperature calcination of the mixture of glucose and calcium carbonate, followed by acid washing for removal of the oxidization products. The contents of Si NSs loaded are fixed at Si/PC = 1:9, 3:7, and 5:5 (in mass), respectively. It is found that the anode with the optimum composition of 30 wt% Si NSs exhibits the best electrochemical performances, owing to a homogeneous dispersion of Si NSs on the PC substrate without severe aggregation, typically a stable discharge specific capacity of 1252 mAh center dot g(-1) with the coulombic efficiency of 99.58% at the current density of 100 mA center dot g(-1) after 100 cycles while retains the capacity of 850 mAh center dot g(-1) even at a high current density of 1 A center dot g(-1) after 800 cycles. In comparison with the entire Si NSs electrode, the best Si/PC composite anode shows two times higher in the capacity retention ability and the excellent rate performance, due to the electrical contribution and large specific surface/pore volume of the PC matrix, which also plays positive roles in mass infiltration of electrolyte and rapid transport/diffusion of electrons/Li+ ions inside the electrodes.