Si-based anode with hierarchical protective function and hollow ring-like carbon matrix for high performance lithium ion batteries

Si-based anode with hierarchical protective function and hollow ring-like carbon matrix has been successfully designed and prepared by a simple one-step spray drying method. Nano-Si particles are coated by carbon layer and then encapsulated in a strong carbon matrix with hollow ring-like structure composed of carbon nanotubes and wrinkled graphene sheets. The Si-based anode, nano-Si@carbon/carbon nanotubes@graphene sheets, exhibits excellent electrochemical performance including high initial coloumbic efficiency, favorable cyclic stability and outstanding rate capability. The composite delivers an initial discharge/charge capacity of 2891.7/2533.3 mAh g(-1) with a high initial coloumbic efficiency of 87.6%, high capacity of 1524.3 mAh g(-1) after 130 cycles with high capacity retention of 92.4% (vs. 1618.4 mAh g(-1) for the 100 cycles), and high capacity maintaining at 1073.2/1016.2 mAh g(-1) at a large current density of 1.6 A g(-1). Furthermore, the scanning electron microscopy and transmission electron microscopy images of the composite electrode after several operating cycles also indicate that composite electrode exhibits structural stability and nano-Si particles are still wrapped by the carbon matrix material. Therefore, the composite is very promising anode for lithium ion batteries.