N-doped carbon encapsulation of ultrafine silicon nanocrystallites for high performance lithium ion storage

A scalable method has been developed to encapsulate silicon (Si) nanocrystallites in a mesoporous N-doped carbon matrix for use as the anode in rechargeable lithium-ion batteries. The deliberate use of ionic liquid as the carbon source and pore size engineering of the SiO2 precursor in the synthesis not only produced the ultrafine Si nanocrystals and the mesoporous N-doped carbon matrix, but also their tight integration into a composite (IL-C-Si-MS) with mixed-conducting (ionic/electronic) properties and effective cushioning of the Si volume change during cycling. The good cyclability and rate performance of IL-C-Si-MS demonstrates the effectiveness of this N-doped carbon encapsulation technique for addressing the instability issues of Si-based anodes.