We describe a graphene and single-walled carbon nanotube (SWCNT) composite film prepared by a blending process for use as electrodes in high energy density supercapacitors. Specific capacitances of 290.6 F g⁻¹ and 201.0 F g⁻¹ have been obtained for a single electrode in aqueous and organic electrolytes, respectively, using a more practical two-electrode testing system. In the organic electrolyte the energy density reached 62.8 Wh kg⁻¹ and the power density reached 58.5 kW kg⁻¹. The addition of single-walled carbon nanotubes raised the energy density by 23% and power density by 31% more than the graphene electrodes. The graphene/CNT electrodes exhibited an ultra-high energy density of 155.6 Wh kg⁻¹ in ionic liquid at room temperature. In addition, the specific capacitance increased by 29% after 1000 cycles in ionic liquid, indicating their excellent cyclicity. The SWCNTs acted as a conductive additive, spacer, and binder in the graphene/CNT supercapacitors. This work suggests that our graphene/CNT supercapacitors can be comparable to NiMH batteries in performance and are promising for applications in hybrid vehicles and electric vehicles.

To investigate the relationship between the oxygenic-containing functional groups of graphene and the stability of supercapacitor, reduced graphene oxide (rGO) containing different oxygenic functional groups were prepared by varying the reduction time of GO using hydrazine as the reducing agent. The TEM, XRD, Raman, and XPS characterization revealed that, as the reduction time increased, the sp² structure in the rGO sheet was restored and the obtained rGO had good crystallinity accompanied by removal of the oxygenic functional groups. The analysis of the content of the different functional groups also suggested that the reduction rate of the oxygenic functional group was C-O > C=O > O-C=O. The supercapacitive performance of rGO showed that the oxygenic functional groups contributed to some pseudocapacitance and resulted in larger specific capacitance. At the same time, however, it is also accompanied by poorer rate performance and durability, which will be improved by removing the oxygenic functional groups by extending the reduction time. With an optimized reaction condition of reduction time of 24 h, the obtained rGO exhibited excellent stability in floating tests at 3.0 V and 45 °C for 60 days. These findings pave the way for development of high quality graphene materials for cost-effective and practical graphene supercapcitors.

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.

The MnCO ₃ /Mn ₃ O ₄ /reduced graphene oxide ternary composites which exhibit excellent electrochemical performance are synthesised via a green and facile method.

A LaB₆ nanoneedle that is fabricated using a focused ion beam shows a high reduced brightness, small energy spread, and especially high emission stability. It can now be used practically as a next-generation field-emission point electron source.

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.