Meizhen Qu

Co3O4@graphene Composites as Anode Materials for High-Performance Lithium Ion Batteries

This paper reports on the synthesis of Co(3)O(4)@graphene composites (CGC) and their applications as anode materials in lithium ion batteries (LIBs). Through a chemical deposition method, Co(3)O(4) nanoparticles (NPs) with sizes in the range of 10-30 nm were homogeneously dispersed onto graphene sheets. Due to their high electrical conductivity, the graphene sheets in the CGC improved the electrical conductivity and the structure stability of CGC. CGC displayed a superior performance in LIBs with a large reversible capacity value of 941 mA hg(-1) in the initial cycle with a large current density and an excellent cyclic performance of 740 mA hg(-1) after 60 cycles, corresponding to 88.3% of the theoretical value of CGC, owing to the interactions between graphene sheets and Co(3)O(4) NPs anchored on the graphene sheets. This synthesis approach may find its application in the design and synthesis of novel electrode materials used in LIBs.

Superparamagnetic Fe3O4 nanocrystals@graphene composites for energy storage devices

In this paper, a Fe3O4 nanocrystals@graphene composite (FGC) was synthesized via a chemical deposition method by using graphene oxide as a precursor. We also investigate the structures, physicochemical properties and applications of FGCs, involving superparamagnetic performance, and use as supercapacitors and lithium ion battery (LIBs). The results showed that the Fe3O4 NCs were formed and incorporated onto the surface of the graphene sheets. The composite material FGC with a micrometre scale structure possessed similar size as the graphene sheets and exhibited superparamagnetic behavior at room temperature. The supercapacitance values of the FGC composites were enlarged compared with those of the graphene sheets or Fe3O4 NCs, which is attributed to the interaction between the Fe3O4 NCs and the graphene sheets. Meanwhile, a superior rechargeable stability of FGCs used as an anode material in LIBs can be observed.

Enhanced anode performances of the Fe3O4–Carbon–rGO three dimensional composite in lithium ion batteries

A three dimensional composite was constructed by anchoring Fe(3)O(4) nanoparticles encapsulated within carbon shells onto reduced graphene oxide sheets, which exhibited enhanced anode performances in lithium ion batteries with a specific capacity of 842.7 mAh g(-1) and superior recycle stability after 100 cycles.

Synthesis and superior anode performance of TiO2@reduced graphene oxide nanocomposites for lithium ion batteries

Herein, we report the synthesis of TiO2-reduced graphene oxide composite (termed as TGC) nanostructures using tetrabutyl titanate as the titanium source via a solvothermal route. The TGC nanostructures were characterized by transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and adsorption–desorption isotherms for nitrogen measurements. The TGC was used as the anode of lithium ion batteries for investigation. The hybrid nanocomposite exhibited remarkable improvement in lithium ion insertion/extraction behaviour compared with TiO2, which showed an initial irreversible capacity and a reversible capacity of 386.4 and 152.6 mAh g−1 for TGC after 100 cycles at a high charge rate of 5 C (1000 mA g−1), compared to 69.5 and 9.7 mAh g−1 for TiO2, respectively. The enhanced electrochemical performance of TGC is attributed to the increased conductivity in the presence of reduced graphene oxide in TGC, the small size of the TiO2 particles in TGC, which can shorten the transport paths for both Li+ ions and electrons, and the enlarged electrode–electrolyte contact area, leading to more electroactive sites in TGC.

Designed synthesis of SnO2-polyaniline-reduced graphene oxide nanocomposites as an anode material for lithium-ion batteries

Three dimensional SnO2-based nanocomposites, i.e., SnO2 nanoparticles anchored on polyaniline nanoplates@reduced graphene oxide nanosheets (SPG) viaπ–π stacking, present excellent cyclability and high capacity with a reversible storage capacity of 573.6 mA h g−1 accompanied by coulombic efficiency of 99.26% over 50 cycles when used as an anode in a lithium ion battery.

Improved performances of β-Ni(OH)2@reduced-graphene-oxide in Ni-MH and Li-ion batteries

Incorporation of reduced graphene oxide into β-Ni(OH)(2) presents high performances with specific discharge capacity of 283 mA hg(-1) after 50 cycles in Ni-MH batteries, and 507 mA hg(-1) after 30 cycles in Li ion batteries.

SnS2@reduced graphene oxide nanocomposites as anode materials with high capacity for rechargeable lithium ion batteries

Nanostructured electrode materials have been studied extensively with the aim of enhancing lithium ion and electron transport, lowering the stress caused by their volume changes during the charge/discharge processes of electrodes, and decreasing overpotential of the electrode reactions in lithium ion batteries. In this work, we develop a new synthetic route to high capacity “double-sandwich-like” SnS2-based nanocomposites (i.e., SnS2-reduced graphene oxide, termed as SSG) which can be used as an anode material in LIBs with improved electrochemical properties, such as large initial discharge capacity (1032 mA h g−1), high reversible discharge capacity (738 mA h g−1, or 1421 mA h cm−3 at 2nd cycle), and excellent cyclability (564 mA h g−1, or 1087 mA h cm−3 after 60 cycles, corresponding to ∼76.5% of the initial reversible capacity), with an excellent coulombic efficiency of ∼96.9%. The electrochemical reaction mechanism of SnS2 with lithium has been suggested to be the alloy-type storage lithium mechanism.

Enhanced anode performances of polyaniline-TiO2-reduced graphene oxide nanocomposites for lithium ion batteries.

Here, we report a three-layer-structured hybrid nanostructure consisting of transition metal oxide TiO(2) nanoparticles sandwiched between carbonaceous polymer polyaniline (PANI) and graphene nanosheets (termed as PTG), which, by simultaneously hindering the agglomeration of TiO(2) nanoparticles and enhancing the conductivity of PTG electrode, enables fast discharge and charge. It was demonstrated that the PTG exhibited improved electrochemical performance compared to pure TiO(2). As a result, PTG nanocomposite is a promising anode material for highly efficient lithium ion batteries (LIBs) with fast charge/discharge rate and high enhanced cycling performance [discharge capacity of 149.8 mAh/g accompanying Coulombic efficiency of 99.19% at a current density of 5C (1000 mA/g) after 100 cycles] compared to pure TiO(2). We can conclude that the concept of applying three-layer-structured graphene-based nanocomposite to electrode in LIBs may open a new area of research for the development of practical transition-metal oxide graphene-based electrodes which will be important to the progress of the LIBs science and technology.

Removal of some impurities from carbon nanotubes

Abstract A non-destructive mild oxidation method of removing some impurities from as-grown carbon nanotubes (CNTs), including single-wall carbon nanotubes (SWNTs) and multi-wall carbon nanotubes (MWNTs), by H2O2 oxidation and HCl treatment, has been investigated, and somewhat pure carbon nanotubes have been prepared. The CNTs from which some impurities were removed have been evaluated by transmission electron microscopy (TEM) and temperature programmed oxidation and gas chromatography (TPO–GC).

SnO2–carbon–RGO heterogeneous electrode materials with enhanced anode performances in lithium ion batteries

Anchoring SnO2 NPs encapsulated in carbon shells onto RGO exhibits superior anode performances in lithium ion batteries with specific capacities of 622 mA h g−1 after 100 cycles.