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We have designed and synthesized a unique structured graphene/SnO2 composite, where SnO2 nanoparticles are inserted in between interconnected graphene sheets which form hollow spherical multilayers. The hollow spherical multilayered structure provides much flexibility to accommodate the configuration and volume changes of SnO2 in the material. When it is used as an anode material for lithium-ion batteries, such a novel nanostructure can not only provide a stable conductive matrix and suppress the mechanical stress, but also eliminate the need of any binders for constructing electrodes. Electrochemical tests show that the unique graphene/SnO2 composite electrode as designed could exhibit a large reversible capacity over 1000 mA h g−1 and long cycling life with 88% retention after 100 cycles. These results indicate the great potential of the composite for being used as a high performance anode material for lithium-ion batteries.

Water-enabled crystallization of amorphous anodic SnO2 is reported. After low-temperature water soaking for a short period of time (e.g., 60 °C for 2 h), mesoporous rutile SnO2 with a remarkably increased surface area is achieved (nearly 2-fold that of the as-anodized SnO2 and 3.3 times that of SnO2 annealed at high temperature). Closer examination reveals that the water-crystallized SnO2 possesses a hierarchical nanostructure that features 1D nanochannels (e.g., ∼30 nm in diameter) and thin channel walls (e.g., 20 nm thick) that are comprised of tiny nanoparticles (e.g., ∼4 nm big). The water-crystallized SnO2 directly grown on the copper foil can be directly applied as a novel type of binder-free electrode for sodium-ion storage, delivering a high reversible capacity of 514 mA h g−1 after 100 cycles at a current rate of 0.1C.

We have successfully assembled graphene nanosheets into spherical shells using polystyrene spheres as templates. Compared with stacked planar graphene, the as-prepared graphene spherical shells have more free space in between the spheres, which results in a larger accessible surface area for adsorption of electrolyte ions in supercapacitors. Electrochemical tests show that the graphene hollow spheres exhibit a high specific capacitance of 273 F g−1 and excellent electrochemical stability.