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Lithium–sulfur (Li–S) batteries are receiving significant attention as a new energy source because of its high theoretical capacity and specific energy. However, the low sulfur loading and large particles (usually in submicron dimension) in the cathode greatly offset its advantage in high energy density and lead to the instability of the cathode and rapid capacity decay. Herein, we introduce a one-step hydrothermal synthesis of three-dimensional porous graphene aerogels/sulfur nanocrystals to suppress the rapid fading of sulfur electrode. It is found that the hydrothermal temperature and viscosity of liquid sulfur have significant effects on particle size and loading mass of sulfur nanocrystals, graphitization degree of graphene and chemical bonding between sulfur and oxygen-containing groups of graphene. The hybrid could deliver a specific capacity of 716.2 mA h g−1 after 50 cycles at a current density of 100 mA g−1 and reversible capacity of 517.9 mA h g−1 at 1 A g−1. The performance we demonstrate herein suggests that Li–S battery may provide an opportunity for development of rechargeable battery systems.

Lithium-sulfur battery has attracted notable attention because of its high special capacity (1675 mAh g−1). However, polysulfide dissolution and low electronic conductivity of sulfur cathode usually cause significant capacity fading during cycling. In this paper, we introduce a double-shelled structure of reduced graphene oxide@polyaniline@sulfur (rGO@PANI@S) composite, which not only can prevent volume expansion at sulfur charge/discharge process, inhibit lithium polysulfides dissolution and shuttle in the electrolyte, and also ensure a good electro-conductibility for sulfur cathode materials. The microstructure and electrochemical performance of the rGO@PANI@S cathode are investigated systematically. The results show that polyaniline inner shell with thickness of about 27.5 nm is coated uniformly on the surface of S submicron particles and few-layered reduced graphene oxide sheets are chemically bonded at the outer surface with a high sulfur content (74 wt%). When used as cathode for lithium-sulfur battery, the rGO@PANI@S composite shows an initial capacity of 1482.7 mAh g−1 at a rate of 100 mA g−1 and retains reversible capacity of 812.1 mAh g−1 over 100 cycles. This all-solution-based process is scalable and the double-shell wrapping structure has promising candidate in designing rechargeable sulfur cathode for application.

We demonstrate in this paper the shape-controlled synthesis of α-Fe2O3 rhombohedra anchored graphene nanocomposites through a simple hydrothermal strategy by adopting inorganic species in the synthesis system. TEM investigations reveal that the rhombohedra with an average diameter of 80 nm is formed through oriented attachment of primary nanocrystals assisted by Ostwald ripening, and CH3COONa inorganic surfactant played an important role in control over the final morphology of the products. As high-performance anodes for lithium-ion batteries, the obtained Fe2O3 rhombohedra/graphene composite exhibits the first reversible capacity of 905.3 mAh g−1, and high capacity retention of 85.7% after 50 cycles. These values are much higher than those of bare Fe2O3 and Fe2O3 particle/graphene composites, indicating its excellent electrochemical stability. These results give us a guideline for the study of the morphology-dependent properties of functional oxide materials as well as further applications for magnetic materials, lithium-ion batteries, and gas sensors.

In this paper, an ultrathin layer of acid treated multiwalled carbon nanotubes (CNTs) are conformally wrapped on everyday cotton textiles for subsequently controlled electrodeposition of MnO 2 nanoflakes. The general morphology and detailed microstructure of the as-prepared composites are characterized and the formation mechanism is investigated by time-dependent experiments. Such conductive textiles show outstanding flexibility and strong adhesion between the CNTs and the textiles of interest. Supercapacitors made from these ternary conductive textiles show high specific capacitance up to 247 F·g −1 at 1 A·g −1 . A capacity retention of 94.7% can be maintained at 2000 continuous charge-discharge cycles, after which the textiles electrode essentially maintained its whole structural integrity. The discharge curves remain unchanged with a slight capacitance decrease even under vertical folding condition. All these demonstrate that hybrid flexible electrode of MnO 2 and conductive textile is an effective strategy towards high-energy supercapacitors and may provide a promising design direction for optimizing the electrochemical performance of insulating metal oxide based on electrode materials.

This article reports a facile preparation of NiO/graphene composite by the combination of a controlled refluxing method with water based solvent in the presence of cetyltrimethylammonium bromide and subsequent annealing. X-ray diffraction and scanning electron microscopy reveal that the graphene nanosheets are uniformly wrapped by hierarchical porous NiO spheres with three-dimension hierarchical structure in the product. The composite shows highly improved electrochemical performance as electrode material for supercapacitor. The three-dimension hierarchical structure NiO/graphene composite delivers a first discharge capacitance of 555 F g −1 and remains a reversible capacitance up to 504 F g −1 after 2000 cycles at a current of 1 A g −1 in three-electrode system. Contrarily, the pure NiO shows only a first discharge capacitance of 166 F g −1 and remains only a reversible capacitance of 107 F g −1 after 2000 cycles. The NiO/graphene composite also exhibits ameliorative rate capacitance of 402.9 F g −1 at the current density of 5 A g −1 . The enhanced electrochemical performances are ascribed to the higher surface area, the stable three-dimension hierarchical structure and the synergistic effects between the conductive graphene and porous NiO spheres.

The mesoporous and nanorods SnO2 are synthesized by controlling the state of SnCl2·2H2O precursor with SBA-15 as hard template, and the possible formation mechanisms at different assembling modes inside the ordered mesoporous silica templates are proposed. In addition, SnO2 nanoparticles are synthesized by hydrolysis depositing method. The electrochemical tests of as-prepared samples indicate that the reticular stacking structure of the nanorods would limit the Li+ ions to intercalate, but the effect of volume expansion in this case upon cycling is insignificant. The mesostructure SnO2 tends to be stable after partial structural collapse at first few cycles. And the Li+ ions can readily intercalate and de-intercalate into/from its ordered channels structure, which provides a high capacity and an improved cycle property. Although SnO2 nanoparticles deliver high capacity at an early stage, the agglomeration may induce the capacity to drop rapidly after a certain number of cycles.

In this study, a nanorod-like Fe2O3/graphene nanocomposite is synthesized by a facile template-free hydrothermal method and a following calcination in air at 300 °C for 2 h. The Fe2O3 nanorods with diameter of 15–30 nm and length of 120–300 nm are homogenous distributed on both sides of graphene. The morphologies of intermediates at different hydrothermal reaction times are investigated by transmission electron microscopy (TEM) characterization, and a possible growth mechanism of this one-dimensional structure is proposed. It is shown that the α-FeOOH rodlike precursors are formed through a rolling-broken-growth (RBG) model, then the α-FeOOH is transformed into α-Fe2O3 nanorods during calcinations, preserving the same rodlike morphology. Electrochemical characterizations demonstrate that the Fe2O3 nanorod/graphene composites exhibit a very large reversible capacity of 1063.2 mAh/g at the charge/discharge rate of 0.1 C.

Chemical lithiation of amorphous FePO4 with LiI in acetonitrile is performed to form amorphous LiFePO4. The amorphous FePO4·2H2O precursor is synthesized by co-precipitation method from equimolar aqueous solutions of FeSO4·7H2O and NH4H2PO4, using H2O2 (hydrogen peroxide) as the oxidizing agent. The nanocrystalline LiFePO4/C is obtained by annealing the amorphous LiFePO4 and in situ carbon coating with sucrose in a reducing atmosphere. The particle size of FePO4·2H2O precursor decreases with increasing reaction temperature. The final LiFePO4/C products completely maintain the shape and size of the precursor even after annealing at 700 °C for 2 h. The excellent electrochemical properties of these nanocrystalline LiFePO4/C composites suggest that to decrease the particle size of LiFePO4 is very effective in enhancing the rate capability and cycle performance. The specific discharge capacities of LiFePO4/C obtained from the FePO4·2H2O precursor synthesized at 75 °C are 151.8 and 133.5 mAh g−1 at 0.1 and 1 C rates, with a low capacity fading of about 0.075 % per cycle over 50 cycles at 0.5 C rate.