Encapsulating silicon particles in conductive layers has proven to be an effective route to retain the high capacity of silicon during cycling. Here, through a core-shell structural design of silicon-polytetrafluoroethylene (PTFE) energetic materials, we demonstrate a large-scale top-down approach for directly obtaining graphene nanosheets encapsulated Si nanoparticles (GrSiNPs) using micrometer-sized PTFE and Si particles as low-cost starting materials. Upon deflagration, high temperature and high pressure of the exothermic reaction between PTFE and Si lead to the fragmentation of the Si core into nanoscale particles, during which the concomitant coating of the Si nanoparticles with graphene nanosheets is achieved. Repeated cycling at a current density of 400 mA g−1 for 6 months, the GrSiNPs demonstrate a high specific capacity of 1613 mAh g−1 after 800 cycles and the average Coulombic efficiency is 101 ± 2%. Our study provides a promising route to the mass production of core-shell structured graphene-Si nanocomposites for high-performance lithium-ion batteries.