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.