Fabrication of Si Nanoparticles Encapsulated into Porous N-Doped Carbon for Superior Lithium Storage Performances

To improve lithium storage performances of Si anode for lithium-ion batteries, Si nanoparticles encapsulated into porous N-doped carbon (Si@PNC) was devised and prepared by metal nitrate accelerated polymer blowing process. The Si@PNC composites have large specific surface area of 221.7 m² g^-1 and possess a great deal of mesopores and micropores, which are attributed to the carbonization of PVP and etching metallic nanoparticles. As anode for lithium ion battery, the initial discharge capacity of Si@PNC composites is high to 1626 mA h g^-1, and the specific capacity still retains 1030 mA h g^-1 after 200 cycles at 200 mA g^-1. Meanwhile, remarkably improved rate capability is achieved with an excellent reversible specific capacity of 375 mA h g^-1 at 5.0 A g^-1. The excellent lithium storage performances benefit from the unique porous core-shell structure of Si@PNC composites, which improve electroconductivity, reduce volume dilatation and accelerate lithium ion transmission.