3D-0D Graphene-Fe₃O₄ Quantum Dot Hybrids as High-Performance Anode Materials for Sodium-Ion Batteries

Transition metal oxides can be considered as appealing candidates for sodium ion battery anode materials because these low-cost materials possess high capacity and enhanced safety. However, the practical application of these materials is usually limited by their low electronic conductivity and serious volume change during the charging-discharging process. Herein, we report the fabrication of 3D-0D graphene-Fe₃O₄ quantum dot hybrids by a facile one-pot hydrothermal approach as anode materials for sodium-ion batteries. Fe₃O₄ quantum dots with an average size of 4.9 nm are anchored on the surface of 3D structured graphene nanosheets homogeneously. Such unique hierarchical structure are advantageous for enlarging the electrode/electrolyte interface area and enhancing the electrochemical activity of the hybrid materials, inhibiting particle aggregation of Fe₃O₄ and accommodating their volume change during the charging-discharging process as well as enabling fast diffusion of electrons and rapid transfer of electrolyte ions. Consequently, the 3D-0D graphene-Fe₃O₄ quantum dot hybrids exhibit ultrahigh sodium storage capacity (525 mAh g^-1 at 30 mA g^-1), outstanding cycling stability (312 mAh g^-1 after 200 cycles at 50 mA g^-1) and superior rate performance (56 mAh g^-1 at 10 A g^-1).