Silicon/carbon composite microspheres with hierarchical core–shell structure as anode for lithium ion batteries

Silicon/carbon composite microspheres with hierarchical core–shell structure were prepared by spray drying polyvinyl alcohol (PVA) solution containing silicon (Si) nanoparticles, followed by surface coating with polyacrylonitrile (PAN) and heat treatment. For the hierarchical structure, the core section (Si/po-C) was composed of PVA-based porous carbon framework and the embedded Si nanoparticles, and the desired Si/po-C@C microspheres were formed by encapsulating the Si/po-C core with PAN-based carbon shell. The Si/po-C@C anode gave rise to stable cycling performances with high capacity and excellent rate capability attributed to the hierarchical structure. The compact PAN-based carbon shell was able to block electrolyte to contact with Si effectively, promoting the formation of stable solid-electrolyte interphase. The porous carbon framework could accommodate the volume change of embedded Si nanoparticles and enhance the internal conductivity.