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We used anionic sulfate surfactants to assist the stabilization of graphene in aqueous solutions and facilitate the self-assembly of in situ grown nanocrystalline TiO2, rutile and anatase, with graphene. These nanostructured TiO2-graphene hybrid materials were used for investigation of Li-ion insertion properties. The hybrid materials showed significantly enhanced Li-ion insertion/extraction in TiO2. The specific capacity was more than doubled at high charge rates, as compared with the pure TiO2 phase. The improved capacity at high charge−discharge rate may be attributed to increased electrode conductivity in the presence of a percolated graphene network embedded into the metal oxide electrodes.

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N anocomposites have attracted wide attention because of their potential to combine desirable properties of different nanoscale building blocks to improve mechanical, optical, electronic , or magnetic properties. 16 Most traditional synthesis approaches of nanocom-posites rely on mechanical or chemical mixing and produce a random distribution of the constitutive phases. To address these problems, several groups recently investigated layer-by-layer deposition and other techniques to prepare layered nanocom-posites with ceramics, clays, and graphite oxide nanoplatelets, 79 but these methods are lacking in nanoscale spatial precision and are time-consuming and difficult for bulk-materials synthesis. On the other hand, biological systems abound with nanocom-posites that possess well-controlled archi-tectures based on multiple scale and multi-functional building blocks. 10 One powerful approach to achieve similar control is to use amphiphilic polymer or surfactant to direct the self-assembly of nanostructured metal oxides, semiconductors, and polymer materials. 1115 There has been a growing interest in incorporating functional components , such as functional groups, polymers, and nanoparticles, into the self-assembled nanostructures, but success has been limited to two-phase organic/inorganic hybrid materials, nanoparticles, or polymer-based nanocomposites. 4,5,16,17 Recently, a range of nanoscale building blocks, including carbon nanotubes 1821 and graphene, 2224 have gained prominence. Graphene and graphene stacks (mul-tilayer graphene), potentially low cost alternative materials to single-wall or multiwall carbon nanotubes, have unique electronic conductivity and mechanical properties. 2527 Graphene-based nanocom-posites with polymer, metal, or metal oxides have also shown unique mechanical, electronic , and electrochemical properties. 23,2835 We focus on the nano-composites made of metal oxides (i.e., SnO 2 , NiO, MnO 2 , and SiO 2) that could have important applications for electrochemical energy storage. 36,37 The low conductivity and poor stability of such materials usually necessitate adding conductive phases to enhance electron transport and electrical contact of the active materials in the electrode of a Li-ion battery. In most of these studies, the approach used to prepare the composite materials has been mechanical mixing of metal oxides with conductive materials such as amorphous carbon, carbon nano-tubes, and graphene. 31,38 In spite of these studies, a well-controlled architecture of the conductive material and metal oxide is difficult to achieve because of improper ABSTRACT Surfactant or polymer directed self-assembly has been widely investigated to prepare nanostructured metal oxides, semiconductors, and polymers, but this approach is mostly limited to two-phase materials, organic/inorganic hybrids, and nanoparticle or polymer-based nanocomposites. Self-assembled nanostructures from more complex, multiscale, and multiphase building blocks have been investigated with limited success. Here, we demonstr...

Modification of the surface chemistry of nanocrystalline VN yields a new class of supercapacitors that deliver an impressive specific capacitance. The creation of surface nanolayers of VOx (poor electronic conductivity) on the electronically conductive nanocrystalline VN shown in the figure and on the cover gives rise to a series of reversible redox reactions that are thought to be responsible for the high capacitance. Application of the concept to other transition metals is expected to broaden the scope of supercapacitor materials.

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Room temperature sodium-ion batteries are of great interest for high-energy-density energy storage systems because of low-cost and natural abundance of sodium. Here, we report a novel phosphorus/graphene nanosheet hybrid as a high performance anode for sodium-ion batteries through facile ball milling of red phosphorus and graphene stacks. The graphene stacks are mechanically exfoliated to nanosheets that chemically bond with the surfaces of phosphorus particles. This chemical bonding can facilitate robust and intimate contact between phosphorus and graphene nanosheets, and the graphene at the particle surfaces can help maintain electrical contact and stabilize the solid electrolyte interphase upon the large volume change of phosphorus during cycling. As a result, the phosphorus/graphene nanosheet hybrid nanostructured anode delivers a high reversible capacity of 2077 mAh/g with excellent cycling stability (1700 mAh/g after 60 cycles) and high Coulombic efficiency (>98%). This simple synthesis approach and unique nanostructure can potentially be applied to other phosphorus-based alloy anode materials for sodium-ion batteries.