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Abstract: A NiO–graphene hybrid film with 3D hierarchically porous structure has been rationally designed and constructed through a series of controlled fabrication processes. Multilayered porous graphene sheet network with the pore size of several micrometers is created via a so-called “on-water spreading” method, which is facile, economical, efficient and scalable. Then, the cross-like NiO nanoflakes film is uniformly grown onto the porous graphene sheet framework by a chemical bath deposition. The NiO–graphene hybrid film exhibits specific capacitance of 540 F g−1 at 2 A g−1 with 80% capacitance retention after 2000 cycles in 2 M KOH aqueous solution, which is much higher than that achieved from the bare NiO nanoflakes film (370 F g−1, with 66% capacitance retention). Moreover, chronoamperometry and electrochemical impedance spectroscopy measurements reveal that the NiO–graphene hybrid demonstrates enhanced reaction kinetics with about only 50% of respond time for NiO/NiOOH reaction and 79% of charge-transfer resistance compared with those of the bare NiO film. The proposed strategy could offer an effective way to fabricate graphene-based electrode materials for applications in various energy-storage devices. [Copyright &y& Elsevier]

Abstract: Carbon perfectly coated LiFePO4 cathode materials are synthesized by carbon-thermal reduction method using polystyrene (PS) spheres as carbon source. The PS spheres with diameters of 150–300nm used for the pyrolysis reaction not only inhibit the particle growth but also lead to uniform distribution of carbon coating on the surface of LiFePO4 particles. Rate capability and cycling stability of LiFePO4/C with the carbon contents ranging from 1.4wt% to 3.7wt% are investigated at −20°C. The LiFePO4/C with 3.0wt% C exhibits excellent electrochemical capability at low temperature, which delivers 147mAhg−1 at 0.1C. After 100 cycles at a charge–discharge rate of 1C, there is still 100% of initial capacity retained for the LiFePO4/C electrode at −20°C. According to the transmission electron microscope analysis and cyclic voltammetry measurement, this can be attributed to the good carbon coating morphology and optimal carbon coating thickness. [Copyright &y& Elsevier]

Graphical abstract Abstract Exploring high performance cathode materials is of great means for the development of bi-functional electrochromic energy storage devices. Herein, Nb-doped WO 3 mesoporous films as integrated high-quality cathode are successfully constructed via a facile sol-gel method. Chemical state and crystallinity of the WO 3 based films are significantly influenced by doping concentration. Compared with the pure WO 3 , the optimal Nb-doped film shows improved optical-electrochemical properties with high specific capacity (74.4 mAh g−1 at 2 A g−1), excellent high-rate capability, large optical contrast (61.7% at 633 nm), and ultra-fast switching speed (3.6 s and 2.1 s for coloring and bleaching process, respectively). These positive features suggest the potential application of Nb-doped WO 3 mesoporous cathode. Our research paves the way for the development of multifunctional photoelectrochemical energy devices. [ABSTRACT FROM AUTHOR]

Metal-doping is considered to be an effective way for construction of advanced semiconducting metal oxides with tailored physicochemical properties. Herein, Mo-doped WO 3 nanowire arrays are rationally fabricated by a sulfate-assisted hydrothermal method. Compared to the pure WO 3 , the optimized Mo-doped WO 3 nanowire arrays exhibit improved electrochromic properties with fast switching speed (3.2 s and 2.6 s for coloration and bleaching, respectively), significant optical modulation (56.7% at 750 nm, 83.0% at 1600 nm and 48.5% at 10 μm), high coloration efficiency (123.5 cm 2 C −1 ) and excellent cycling stability. In addition, as a proof of concept, the Mo-doped WO 3 nanowire arrays are demonstrated with electrochemical energy storage monitored by the electrochromism. This electrode design protocol can provide an alternative way for developing high-performance active materials for bi-functional electrochromic batteries. [ABSTRACT FROM AUTHOR]

The construction of advanced cathode materials is indispensable and vital for developing high-performance lithium–sulfur batteries. Herein, we develop a facile in-situ route to synthesize three-dimensional reduced graphene oxide supported Li 2 S/carbon composite (3D-rGO-Li 2 S/C). The Li 2 S/C nanoparticles are intimately anchored on the surface of 3D-rGO forming an integrated 3D porous composite. Due to the improved conductivity and reduced polysulfide dissolution, the 3D-rGO-Li 2 S/C cathode exhibits enhanced electrochemical performances with a high initial capacity of 819 mAh g −1 at 0.1C, as well as good cycling stability with a capacity retention of 415 mAh g −1 after 100 cycles at 1C. The integrated 3D conductive network is responsible for the enhancement of the electrochemical properties by providing fast ion/electron transfer and high mechanical stability. [ABSTRACT FROM AUTHOR]

Abstract: CoFe2O4 flower-like microspheres are prepared via a surfactant- and template-free method, involving the controlled hytrothermal synthesis firstly and a subsequent thermal decomposition treatment. The microspheres with diameters of 3–4 μm are characterized by the assembly of numerous porous and inter-connected lamella structures. Lithium-ion batteries electrodes based on the as-prepared CoFe2O4 microspheres show a high specific capacity of 733.5 mAh g−1 after 50 cycles at a current density of 200 mA g−1 and a good cyclic stability, as well as excellent rate capability. The enhanced electrochemical performance can be attributed to the hierarchical microsphere structure with high sufficient interfacial contact area between the microspheres and electrolyte, the short diffusion distance of Li+, better accommodation of structural stress and volume change with the lithiation/delithiation process. It is suggested that the CoFe2O4 microsphere is one of the most promising candidates for high-performance lithium-ion batteries. [Copyright &y& Elsevier]

Highlights: [•] Different metal sources are used to prepare Li[Li0.2Mn0.56Ni0.16Co0.08]O2 by sol–gel. [•] Porosity with surface area of 10.09m2 g−1 is only observed when nitrate is used. [•] High discharge capacity of 247.8mAhg−1 is obtained at 1°C for the porous oxides. [•] Porous morphology with good particle contact can efficiently reduce the impedance. [ABSTRACT FROM AUTHOR]

Abstract: LiF is successful used to modify the surface of layered LiNi1/3Co1/3Mn1/3O2 via a wet chemical method followed by an annealing process. The lattice structure of LiNi1/3Co1/3Mn1/3O2 is not changed distinctly after modification and part of F− dopes into the surface lattice of the oxide. The LiF-modified oxide exhibits capacity retentions of 97.5% at 0.1 C at room temperature and 93.5% at 1 C at 60 °C after 50 cycles, and delivers a high discharge capacity of 137 mAh g−1 at 10 C at room temperature. Furthermore, it has reversible capacities of 124.4 mAh g−1 at 1 C at 0 °C and 85.6 mAh g−1 at 0.1 C at −20 °C, respectively. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests show that the LiF-modified layer can reduce the dissolution of metal ions in the electrode and enhance the conductivity of the oxide surface through partly F-substitution. LiF modification will be promising for the application of layered oxide for lithium ion batteries. [Copyright &y& Elsevier]

Abstract: MgO-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 was synthesized via melting impregnation method followed by a solid state reaction. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) show that the MgO layer is well coated on the surface of the layered oxide particles. Although the initial discharge capacity of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 with proper MgO modification decreases compared to the bare one, the 2wt.% MgO coated cathode exhibits the excellent cycling stability with capacity retention of 96.4% at a current density of 200mAg−1 after 100 cycles at room temperature and 94.3% after 50 cycles at 60°C. Electrochemical impedance spectroscopy (EIS) shows that the thin MgO layer mainly reduces the charge transfer resistance and stabilizes the surface structure of active material during cycling. Melting impregnation method is promising for MgO coating to improving the cycling stability of Li-rich layered oxide cathode for Li-ion batteries. [Copyright &y& Elsevier]

Abstract: Porous Fe3O4/C core/shell nanorods have been prepared by a facile hydrothermal method using porous Fe2O3 nanorods as the precursor and glucose as the carbon source. The Fe3O4/C nanorods possess a uniform size with 50–80nm in diameter and 300–500nm in length, and are homogenously coated by amorphous carbon layer. The porous nanorods greatly increase the electrical contact, thus facilitating the Li-ion and electron transportation, and enhancing the reactivity of the electrode. Also, the carbon layer can effectively limit the volume expansion and detachment of Fe3O4, and thus increase its structure stability during cycling. In the context of lithium storage behavior, the Fe3O4/C nanorod electrode shows high capacity and good cycle stability, as well as enhanced rate performance. After 50 cycles, the reversible capacity of the porous Fe3O4/C nanorods is 762.1mAhg−1 at 0.1C and 597.2mAhg−1 at 0.5C, much higher than that of α-Fe2O3 nanorods (276.4mAhg−1) and Fe3O4 nanoparticles (307.9mAhg−1). At a high rate of 1C, the specific capacity of Fe3O4/C nanorods is still as high as 630.1mAhg−1. [Copyright &y& Elsevier]

Abstract: Rod-like LiV3O8 composites have been fabricated by using a carbamide-assisted rheological phase reaction method. The electrochemical performances of the LiV3O8 materials prepared under different conditions are investigated by cyclic voltammograms, galvanostatic charge–discharge tests and electrochemical impedance spectroscopy (EIS). The rod-like LiV3O8 calcined at 500°C has the optimal performance, delivering an initial discharge capacity of 273.6 and 250.4mAhg−1 between 2.0V and 4.0V at a current density of 50 and 120mAg−1, respectively. After 60 cycles by applying 50mAg−1, a discharge capacity of 213.0mAhg−1 is obtained, showing a good cycling performance. The EIS studies show that the 500°C-LiV3O8 electrode has very low impedance increase during 1st to 240th discharge-charge cycles. All these results indicate that the rod-like LiV3O8 compound has a promising application as the cathode material for rechargeable lithium batteries. [Copyright &y& Elsevier]

Abstract: Well-crystallized FeS2 powders are synthesized via solid state reaction. Influence of particle size on electrochemical performances has been conducted. Compared with other anode materials, FeS2 powder with mean particle size of 0.28μm exhibits high coulombic efficiency, initial discharge specific capacity, low polarization and enhanced electrode process kinetics. The enhanced electrochemical properties are attributed to the dense powder packing, better electrical contact and relative stable structure during cycling process. Smaller FeS2 particles (0.078 and 0.071μm) have difficulty in dispersing and mixing with carbon black and binder and less dense packing state, leading to a decrease of reactive contact surface area and poor electrochemical performance. [Copyright &y& Elsevier]

Abstract: Hexagonal structured WO3 films with tree-like morphology were synthesized on tungsten foils by a hydrothermal method. Each nanotree was composed of several (typically six) nanosheet-shaped “branches”. TEM examination revealed that the nanosheet was a single crystal and its long axis was oriented toward 〈001〉 direction. The WO3 nanotree films retain the hexagonal structure after being annealed up to 400°C for 2h, while they have a phase transition to monoclinic structure after being annealed at 500°C for 2h. Electrochromic (EC) performance of the films was examined in a propylene carbonate solution of 1M LiClO4 using an electrochemical workstation and an UV–Vis spectrometer. Due to the large tunnels of hexagonal structure and highly porous surface morphology, a large modulation of optical reflectance of WO3 nanotree films up to 30% and coloration efficiency of 43.6cm2 C−1 at 500nm were achieved by annealing the WO3 nanotree films at 400°C for 2h. [Copyright &y& Elsevier]