Integration of individual two-dimensional graphene sheets into macroscopic structures is essential for the application of graphene. A series of graphene-based composites and macroscopic structures have been recently fabricated using chemically derived graphene sheets. However, these composites and structures suffer from poor electrical conductivity because of the low quality and/or high inter-sheet junction contact resistance of the chemically derived graphene sheets. Here we report the direct synthesis of three-dimensional foam-like graphene macrostructures, which we call graphene foams (GFs), by template-directed chemical vapour deposition. A GF consists of an interconnected flexible network of graphene as the fast transport channel of charge carriers for high electrical conductivity. Even with a GF loading as low as ∼0.5 wt%, GF/poly(dimethyl siloxane) composites show a very high electrical conductivity of ∼10 S cm(-1), which is ∼6 orders of magnitude higher than chemically derived graphene-based composites. Using this unique network structure and the outstanding electrical and mechanical properties of GFs, as an example, we demonstrate the great potential of GF/poly(dimethyl siloxane) composites for flexible, foldable and stretchable conductors.

We report a facile strategy to synthesize the nanocomposite of Co3O4 nanoparticles anchored on conducting graphene as an advanced anode material for high-performance lithium-ion batteries. The Co3O4 nanoparticles obtained are 10−30 nm in size and homogeneously anchor on graphene sheets as spacers to keep the neighboring sheets separated. This Co3O4/graphene nanocomposite displays superior Li-battery performance with large reversible capacity, excellent cyclic performance, and good rate capability, highlighting the importance of the anchoring of nanoparticles on graphene sheets for maximum utilization of electrochemically active Co3O4 nanoparticles and graphene for energy storage applications in high-performance lithium-ion batteries.

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There is growing interest in thin, lightweight, and flexible energy storage devices to meet the special needs for next-generation, high-performance, flexible electronics. Here we report a thin, lightweight, and flexible lithium ion battery made from graphene foam, a three-dimensional, flexible, and conductive interconnected network, as a current collector, loaded with Li 4 Ti 5 O 12 and LiFePO 4 , for use as anode and cathode, respectively. No metal current collectors, conducting additives, or binders are used. The excellent electrical conductivity and pore structure of the hybrid electrodes enable rapid electron and ion transport. For example, the Li 4 Ti 5 O 12 / graphene foam electrode shows a high rate up to 200 C, equivalent to a full discharge in 18 s. Using them, we demonstrate a thin, lightweight, and flexible full lithium ion battery with a high-rate performance and energy density that can be repeatedly bent to a radius of 5 mm without structural failure and performance loss.flexible device | full battery T he development of next-generation flexible electronics (1), such as soft, portable electronic products, roll-up displays, wearable devices, implantable biomedical devices, and conformable health-monitoring electronic skin, requires power sources that are flexible (2, 3). Similar to conventional energy storage devices, flexible power sources with high capacity and rate performance that enable electronic devices to be continuously used for a long time and fully charged in a very short time are very important for applications of high-performance flexible electronics (4-7). Lithium ion batteries (LIBs) have a high capacity but usually suffer from a low charge/discharge rate compared with another important electrochemical storage device, supercapacitors. Therefore, it is highly desired to fabricate a flexible electrochemical energy storage system with a supercapacitor-like fast charge/discharge rate and battery-like high capacity. However, the fabrication of such an energy storage device remains a great challenge owing to the lack of reliable materials that combine superior electron and ion conductivity, robust mechanical flexibility, and excellent corrosion resistance in electrochemical environments.Using nano-sized materials to prepare electrodes is one of the most promising routes toward flexible batteries. Metal oxide nanowires (8, 9) and carbon nanomaterials such as carbon nanotubes (6, 10-12) and graphene paper (13) have been recently demonstrated for use in flexible LIBs. However, electron transport in these electrodes is slow because of the relatively low quality of nanomaterials (such as chemically derived graphene) and/or high junction contact resistance between them. As a consequence, only a moderate charge/discharge rate has been obtained in these flexible batteries. It is generally believed that the charge/discharge rate of a LIB depends critically on the migration rate of lithium ions and electrons through the electrolyte and bulk electrodes into active electrode materials. Strategies to inc...

We developed a hydrogen arc discharge exfoliation method for the synthesis of graphene sheets (GSs) with excellent electrical conductivity and good thermal stability from graphite oxide (GO), in combination with solution-phase dispersion and centrifugation techniques. It was found that efficient exfoliation and considerable deoxygenation of GO, and defect elimination and healing of exfoliated graphite can be simultaneously achieved during the hydrogen arc discharge exfoliation process. The GSs obtained by hydrogen arc discharge exfoliation exhibit a high electrical conductivity of ϳ2 ؋ 10 3 S/cm and high thermal stability with oxidization resistance temperature of 601 °C, which are much better than those prepared by argon arc discharge exfoliation (ϳ2 ؋ 10 2 S/cm, 525 °C) and by conventional thermal exfoliation (ϳ80 S/cm, 507 °C) with the same starting GO. These results demonstrate that this hydrogen arc discharge exfoliation method is a good approach for the preparation of GSs with a good quality.