Si Nanoparticles Coated with Co-Containing N-Doped Carbon: Preparation and Characterization as Li-Ion Battery Anode Materials.

Si nanoparticles uniformly coated with Co-containing N-doped carbon were investigated as an anode material for Li-ion batteries. The Si nanoparticle surfaces were modified with conductive and matrix, N-doped carbon and cobalt element and prepared by a simple pyrolysis process using an ionic liquid that contained nitrogen with metal complex. After a simple annealing process, the N-doped carbon containing cobalt element was uniformly coated onto the Si nanoparticles. The smooth carbon layer connected the Si nanoparticles without any morphological changes. Si nanoparticles containing 34 wt% N-doped carbon and cobalt element exhibited a stable electrochemical performance with a capacity of ~1133 mAh g and excellent capacity retention over 60 cycles. The high electrochemical performances was attributed to the synergistic effect by presence cobalt in N-doped carbon matrix, which alleviated the lithium-silicon alloying reaction-induced volume expansion and enhanced electrical conductivity during cycling.