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Abstract: Co-precipitation method of SnCl2·2H2O and graphene oxide (GO) solution was performed to fleetly prepare graphene/SnO2 composite. The structure and composition of the nanocomposite were detected by means of XRD, SEM, TEM and FT-IR. The GO was reduced by bivalent tin ions to graphene nanosheet (GNS) via solution reaction and SnO2 nano-crystals with size of 4–6nm were homogeneously distributed on the matrix of GNS. It was found that the disorder degree of graphene in GNS/SnO2 composite prepared by the bivalent tin ion assisted reduction method was much lower than that of GNS obtained via pyrolysis reduction. The possible mechanism for this phenomenon was discussed in detail. The N2 adsorption tests showed an ink-bottle-like pore structure of GNS/SnO2 and the SnO2 nanoparticles were confined in the interlayer of GNS without agglomeration. These structural features were desirable and enabled GNS/SnO2 an excellent anode material in lithium ion battery. The electrochemical tests showed that the composite could deliver a reversible capacity of 775.3mAh/g and capacity retention of 98% after 50 cycles. [Copyright &y& Elsevier]

Abstract The reunion of Sn is always a troublesome issue when it's used as the energy storage materials, on the one hand it comes from the preparation process due to its low melting point, and on the other hand it comes from the Li-Sn alloying process because of its natural tendency of migration. The Sn/SnO 2 /spherical graphene composite prepared by one-step low temperature hydrothermal reduction method can effectively solve this problem. In the composite, Sn/SnO 2 tiny nanoparticles with average diameter of 5 nm distribute evenly between multilayers of graphene sheets presenting a hollow spherical structure. The introduction of SnO 2 can effectively restrain the agglomeration of Sn nanoparticles during alloying process since an amorphous Li 2 O matrix is formed to separate the adjacent active particles. The sandwich graphene hollow sphere skeleton effectively buffers the volume expansion of Sn/SnO 2 and further restricts their migration and agglomeration. Due to the above advantages, the nano-Li 2 O generating from the decomposition of SnO 2 can contact closely with excessive nano-Sn in restricted area, promoting facile conversed conversion reaction. Therefore, the composite exhibits high reversible capacity and excellent cycle performance. A stable and high specific capacity of 843.8 mAh g−1 is obtained after 100 cycles at 0.1 C. Graphical abstract Image Highlights • Tiny Sn/SnO 2 NPs sandwiching between SG is designed to solve Sn anode's problem. • Sn/SnO 2 /SG is prepared by one-step low temperature hydrothermal reduction method. • Li 2 O generated from SnO 2 acts as buffer matrix for Sn at subsequent alloy process. • Li 2 O and excess nano-sized Sn can react easily to reversibly transform into SnO 2. • Excellent cycle stability is presented in Sn/SnO 2 /SG composite. [ABSTRACT FROM AUTHOR]

Exploring versatile strategies for microstructural evolution and surface modification are of fundamental importance in the development of advanced electrode materials. In this work, we report that electron-beam irradiation is a facile approach to perform surface modification for the ultrathin cross-stacked graphene aerogels loaded with SnO 2 quantum dots, resulting in a remarkable modulation on the lithium storage performance. It is found that the as-synthesized SnO 2 /graphene aerogels composites irradiated at 280 kGy exhibit excellent high reversible lithium storage capacity, good rate capability and cycling stability, which retains a discharge capacity of 703 mAh g −1 after 50 cycles at 0.1 C rate. Microstructure analysis indicates that the enhanced electrochemical properties are mainly attributed to the exfoliation of graphene nanosheets, the increase of amorphization, disorder, defects and the removal of partial oxygen-containing functional groups on the surface of graphene nanosheets. The strategy presented here demonstrates that the electron-beam irradiation is a potential strategy to improve the electrochemical performance of graphene-based metal oxides. [ABSTRACT FROM AUTHOR]

Abstract: A new porous graphene/NiO has been prepared successfully by hydrothermal method with graphene oxide solution, Ni(NO3)2·6H2O and urea as raw materials. The as-prepared composite is characterized by X-ray diffraction, Raman, FT-IR, SEM, TEM and nitrogen adsorption/desorption. It is shown that graphene sheets are well decorated by the NiO nanoparticles to form a hierarchical nanostructures with rich porosity (ca. 2–5nm) and large specific surface area (174.1m2 g−1). Electrochemical characterization demonstrates that the mesoporous graphene/NiO are capable of delivering a specific capacitance of 429.7Fg−1 at the current density of 200mAg−1 and offer good capacitance retention of 86.1% at 1Ag−1 after 2000 continuous charge–discharge cycles. These rich and evenly distributed porosity could reduce the transportation distance and offer a robust sustentation of OH− ions due to its “ion-buffering reservoirs”, ensuring that sufficient Faradaic reactions can take place at the surfaces of electroactive NiO nanoparticles. It suggests that the hierarchical nanostructure is helpful in improving the electrochemical performance of the oxide. [Copyright &y& Elsevier]

Abstract: In this paper, graphene-modified Li3V2(PO4)3 composites have been developed as Li-ion battery cathode materials with high specific capacity and excellent cycling stability. The composites are prepared by spray–drying process using graphene oxide nanosheet and citric acid as carbon source. X-ray diffraction patterns demonstrate that the as-prepared samples are well crystallized with orderly monoclinic structures. SEM and TEM images reveal that the 3D network graphene and Li3V2(PO4)3 primary nanoparticles interlace with each other. The citric acid-derived amorphous carbon species interrupt the stacking of graphene sheets and minimize in-plane anisotropy of electronic migration within graphene layers, which would facilitate fast electron migration and Li+ diffusion throughout the micro-sized spherical secondary particles. The discharge capacity of the composite could respectively achieve 131.4 and 181.5mAhg−1 in the voltage range 3.0–4.3V and 3.0–4.8V at 0.1C discharge rate, which almost reach the theoretical capacity of the cathode material. Both of them nearly showed no capacity decay at 0.1C charging and discharging rate after long cycles. [Copyright &y& Elsevier]

• Graphene bubble film encapsulated Si@C hollow spheres is designed as LIB anodes. • Si hollow spheres are wrapped by interior CVD carbon shell and external GNS layers. • Carbon shell inhibits si particles agglomeration and detrimental interface reactions. • Graphene bubble film enhances structural stability and electronic conductivity. • Enhanced electrochemical performances are presented compared to H-Si@C and G/H-Si. Silicon-based composites have been proposed as the promising anode materials for Li-ion batteries. In order to avoid the operational problems of silicon-based anodes such as the low electric conductivity and huge volume expansion, we succeed in encapsulating Si@C hollow spheres into flexible graphene bubble film as a durable anode with enhanced lithium storage properties. In this design, sub-micrometer-sized Si hollow spheres are wrapped into accessible mesoporous carbon shells. Then, the Si@C hollow spheres are tightly wrapped with amino-functionalized graphene oxide nanosheets and followed by chemical reduction to form a bubble film composite structure. Such closely packed graphene bubble films encapsulating hollow Si@C macrostructure ensures uniform and aggregation-free distribution of silicon spheres in the dual conductive carbon network. This kind of graceful composite structure can not only suppress volume expansion and improve structural stability of the electrode material, but also facilitate the electron transfer and lithium ion migration by shortening the transportation channels. The as-prepared composite exhibits impressive Li storage performance with a high reversible capacity of 813.2 mAh g −1 after 100 cycles at 0.1C. This work offers an appealing strategy for high-performance Si-based anode materials in practical application. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Low reversion of Li 2 S and the Sn aggregation causing irreversible capacity loss are the primary cause of poor cycle performances in tin sulfide-based composites. These problems can be mitigated by confining SnS nanoparticles in sandwiched hollow-spherical graphene skeleton (Sandwich-SnS/GS), in which a large number of tiny SnS nanoparticles are inserted in between the interlayers of the sphere-like graphene shell with homogeneous distribution, while the spherical graphene interconnects each other forming a three-dimensional interconnected conductive network. This novel spherical graphene skeleton can immobilize the SnS and the lithiated products (Sn and Li 2 S) and suppress the local accumulation of metallic Sn at the largest extent, thus prompting the close contact of Sn/Li 2 S and their in-situ reverse transformation into SnS. In addition, the closed graphene sphere could inhibit the shuttle of lithium polysulfides derived from Li 2 S during charging, promote reversible transformation between Li 2 S and S 8 , providing an additional capacity contribution and ensuring the sustained capacity of the whole electrode without distinct decay. Thus, a high and stable reversible specific capacity of 756.7 mA h g−1 is retained in the Sandwich-SnS/GS composite after 200 cycles at 100 mA g−1, significantly higher than those of traditional hollow sphere and sandwich-like lamellar composite structures. [ABSTRACT FROM AUTHOR]