Si–carbon core–shell composite anode in lithium secondary batteries

A Si–carbon core–shell powder was prepared via resorcinol-formaldehyde (RF) microemulsion polymerization in the presence of hydrophobized Si nano-particles and subsequent carbonization. The Si nano-particles were completely encapsulated by amorphous carbon shell. With this core–shell approach, the anodic performance of Si electrode for lithium cells has been improved on aspects of Si utilization and cycle retention, which seems to be indebted to the formation of stable electronic conductive network by an intimate contact between Si core and carbon shell. The capacity delivered by this electrode is, however, smaller than that of bare Si due to the presence of RF-derived carbon and electrochemically inactive silicon oxide that was generated during the carbonization process by a reaction between Si and oxygen from the RF gel. The evolution of cracks in the carbon shell after cycling is additional problem to be solved.