One-Pot Synthesis of Pomegranate-Structured Fe₃O₄/Carbon Nanospheres-Doped Graphene Aerogel for High-Rate Lithium Ion Batteries

A unique hierarchically nanostructured composite of iron oxide/carbon (Fe₃O₄/C) nanospheres-doped three-dimensional (3D) graphene aerogel has been fabricated by a one-pot hydrothermal strategy. In this novel nanostructured composite aerogel, uniform Fe₃O₄ nanocrystals (5-10nm) are individually embedded in carbon nanospheres (ca. 50nm) forming a pomegranate-like structure. The carbon matrix suppresses the aggregation of Fe₃O₄ nanocrystals, avoids direct exposure of the encapsulated Fe₃O₄ to the electrolyte, and buffers the volume expansion. Meanwhile, the interconnected 3D graphene aerogel further serves to reinforce the structure of the Fe₃O₄/C nanospheres and enhances the electrical conductivity of the overall electrode. Therefore, the carbon matrix and the interconnected graphene network entrap the Fe₃O₄ nanocrystals such that their electrochemical function is retained even after fracture. This novel hierarchical aerogel structure delivers a long-term stability of 634mAhg^-1 over 1000 cycles at a high current density of 6Ag^-1 (7C), and an excellent rate capability of 413mAhg^-1 at 10Ag^-1 (11C), thus exhibiting great potential as an anode composite structure for durable high-rate lithium-ion batteries.