Mesoporous Si/C composite anode material: experiments and first-principles calculations

Carbon-coated and doped mesoporous silicon/carbon (m-Si/C) composites were successfully prepared via carbon coating and molten magnesiothermic reduction by using mesoporous silica (SBA-15) and dopamine as raw materials. Experimental results were theoretically verified by first-principles calculation. The obtained m-Si/C composites exhibited a high initial Coulombic efficiency of 73% at 0.1 A g−1 and an excellent cycling stability with 617.5 mAh g−1 capacity after 100 cycles at 0.1 A g−1. This excellent performance was attributed to the combination of carbon and the mesoporous structure of SBA-15 to form a mesoporous carbon framework which could improve the stability and conductivity of the material. The oxygen defects that formed after molten magnesiothermic reduction could effectively alleviate the change in the volume of the Si core and shorten the diffusion path of Li+ in the Si core. Graphene layers could effectively reduce the energy of the system and the band gap, the embedding of Li+ would lead to the expansion and distortion of Si, and the carbon layer with elasticity and hardness could buffer the volume expansion of m-Si/C composites. Consistent with experimental results, theoretical results demonstrated that graphene-coated composites positively affected the Li storage of Si.