Hierarchical goethite nanoparticle and tin dioxide quantum dot anchored on reduced graphene oxide for long life and high rate lithium-ion storage

The synergetic effect between two or more electrochemically active materials usually leads to superior lithium-ion storage performance. This work demonstrates a straightforward and effective approach to synthesize a reduced graphene oxide (RGO) encapsulated larger goethite (FeOOH) nanoparticles and smaller tin dioxide (SnO₂) quantum dots hierarchical composite (SnO₂@FeOOH/RGO). The synthesized SnO₂@FeOOH/RGO composite exhibits encouraging lithium-ion storage capability than controlled SnO₂/RGO and FeOOH/RGO samples with a stable specific capacity of 638 mAh·g^-1 under a high current rate of 1000 mA·g^-1 for 2000 continual cycles and good rate performance. The redox reaction between reductive metal-atoms or metal-ions and graphene oxide (GO) sheets guarantees an effective immobilization of corresponding nano-sized metal oxide and hydroxide crystals by the RGO framework. Furthermore, the engineered larger FeOOH crystals engage in lithium-ion storage and perform an ideal spacer between the restacked RGO sheets. Therefore, smaller SnO₂ quantum dots' inherent excellent rate capability is extensively promoted due to the improvement of electrolyte diffusion and electron transfer condition. The sample design and fabrication method in this work might be developed for broader applications.