Fabrication of honeycomb-like amorphous carbon-encapsulated Si nanoparticles/graphene composite for superior lithium storage

Silicon (Si) anodes have great potential for high-energy lithium-ion batteries (LIBs). However, poor electrical conductivity, high cost and huge volume change during the (de)lithiation processes of silicon anodes hinder the practical application. Herein, we demonstrate a facile and scalable approach to fabricate a porous honeycomblike amorphous carbon-encapsulated Si nanoparticles/graphene composite via a sol-gel & CO2-introduced magnesiothermic reduction method. The greenhouse gas CO2 is efficiently transformed into carbon layers. Interconnected carbon network consisting of graphene sheets and amorphous carbon layers not only significantly improves the electrical conductivity and mechanical properties of the Si-based composites, but also provides the strong interaction between Si and carbon materials. Besides, both unique honeycomb-like porous structure and interconnected carbon network can butter large volume effects of Si nanoparticles. The as-prepared amorphous carbon-encapsulated Si/graphene anode with the carbon content of 8 wt% has excellent rate performance and outstanding cycling stability, delivering a high discharge capacity of 908 mAh g-1 with 65.9 % of capacity retention at 0.5 A g-1 after 200 cycles. Thus, such honeycomb-like amorphous carbon-encapsulated Si nanoparticles/graphene composite anode is highly promising for practical next-generation LIBs.