Pomegranate-Like Silicon/Nitrogen-doped Graphene Microspheres as Superior-Capacity Anode for Lithium-Ion Batteries

Highlights: • Pomegranate-like Silicon/Nitrogen-doped graphene microspheres have been prepared. • The N-doped graphene provides enormous Li⁺ diffusion channels and active sites. • The wrapping graphene significantly enhances the conductivity of Si-based anode. • The PSNGM anode exhibits excellent electrochemical performance with high capacity. - Abstract: Herein, pomegranate-like Silicon/Nitrogen-doped graphene microspheres (PSNGM) constructed by individual Si nanoparticle core wrapped by flexible nitrogen-doped reduced graphene oxide nanosheets (NG) have been synthesized through a facile and industrially large-scale spray drying approach. The PSNGM anode delivers excellent electrochemical performance: the reversible specific capacity at 100 mA g⁻¹ remains as large as 1141.6 mAh g⁻¹ after 150 cycles, with a high capacity retention of 96.1% from 2nd to 150th cycle; the capacity at 100 mA g⁻¹ can recover back to ∼1340 mAh g⁻¹ even after suffering a high current density of 5000 mA g⁻¹. The excellent performance is attributed to the unique pomegranate-like structure, nanoparticlization of Si and nitrogen doping of graphene: the pomegranate-like skeleton forms a highly conductive network, in which each Si nanoparticle is homogenously wrapped by flexible and conductive N-doped graphene nanosheets; flexible porous pomegranate-like structure can effectively accommodate the large volume variation during cycling; the N-doped graphene matrix guarantees its high conductivity for better electron and ion kinetics. The presented spray drying strategy is facile, low-cost and effective for large-scale industrial production of Si/graphene composite anode, and it can also be extended to fabricating other high-capacity electrode materials with low conductivities and large volume expansion.