Facile preparation of Hollow Si/SiC/C yolk-shell anode by one-step magnesiothermic reduction

Silicon is a promising anodic material used in lithium-ion battery (LIB) to improve the specific energy. While the huge volume change during lithiation/delithiation and low intrinsic conductivity has been a bottle neck of silicon anode. For this sake, carbon shell was used to enhance the conductivity, and hollow structure to buffer the volume swelling/shrinking during cycles. In this work, we synthesized a hollow yolk-shell structure Si/SiC/C (SSC) anode by one-step magnesiothermic reductive reaction. At first, polydopamine (PODA) was used as carbon source to optimize the dosage of magnesium powder and reaction temperature. Then resorcinol formaldehyde (RF) resin was used as another carbon source to prepare several samples with different carbon shell thicknesses. A vital parameter, critical thickness, about 10nm of final shell was proposed to keep the hollow yolk-shell morphology. During this one-step exothermic reaction, Si and C spontaneously reacted and formed inter SiC layer with high modulus. The half-cell with SSC anode delivered a capacity of 505.8 mA h g^-1 after 220 cycles at a current density of 100 mA g^-1. This novel method is facile to realize and might be used in other fields like composite plating and material modification etc.