3D-0D Graphene-Fe₃O₄ quantum dot hybrids as high-performance anode materials for sodium-ion batteries

Huan Liu, Mengqiu Jia*, Qizhen Zhu, Bin Cao, Renjie Chen, Yu Wang, Feng Wu, Bin Xu*

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^–1at 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).