Ionic liquid assist to prepare Si@N-doped carbon nanoparticles and its high performance in lithium ion batteries

Silicon is a potential next generation anode material for lithium-ion battery, however, its commercial application was hindered by its poor electronic conductivity and huge volume change upon lithiation. Herein, Si@N-doped carbon nanoparticles with commercial Si nanoparticle as the core and N-doped carbon as the shell were prepared by a facial, low-cost and scalable one-step method using ionic liquid (3-cyanopyridine/H2SO4) as both of the N and C sources. While using as anode material for lithium-ion batteries, Si@N-doped carbon exhibited a high reversible capacity of 725 mAh/g after 100 discharge/charge cycles at a current density of 420 mA/g, about twice higher than that of Si@C, a control sample prepared by a similar process using sucrose as the carbon precursor, which showed a capacity of 360 mAh/g after 100 cycles at 420 mA/g. The improved electrochemical performance could be ascribed to the stable core-shell structure of the nanocomposite and more importantly the doping of N element into the carbon shell. Furthermore, this work also provides a versatile strategy for preparation of core-shell N-doped carbon coated nanoparticles.