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Improving the insulating nature of sulfur and retaining the soluble polysulfides in sulfur cathodes are crucial for realizing the practical application of lithium–sulfur batteries ...(LSBs). Biomass-based carbon is becoming increasingly popular for fabricating economical and efficient cathodes for LSBs owing to its unique structure. Herein, we report a facile strategy to transform bovine bone with an organic–inorganic structure into cellular hierarchical porous carbon via carbonization and KOH activation, followed by CoS2 modification through hydrothermal treatment. The synthesized composite can load abundant sulfur and produce a dual effect of “physical confinement and chemical entrapment” on polysulfides. The conductive carbon frame with the developed porous structure provides adequate space to accommodate sulfur and physically suppress the shuttle effect of polysulfides. The embedded half-metallic CoS2 sites can chemically anchor the polysulfides and enhance the electrochemical reaction activity as well. Owing to the multifunctional structure and dual restraint effect, the designed electrode exhibits enhanced electrochemical properties including high initial capacity (1230.9 mAh g−1 at 0.2 C), improved cycling stability and enhanced rate capability.
Macroporous Li1.2Mn0.54Ni0.13Co0.13O2 cathode materials with high crystallinity and hexagonal ordering are synthesized by aerogel template followed by solid state reaction. High discharge capacities ...of 244.0 mA h g−1 and 153.9 mA h g−1 are obtained for the Li-rich layered oxide synthesized at 800 °C at current densities of 200 mA g−1 and 2000 mA g−1 between 2.0 V and 4.8 V. Increasing the synthesis temperature to 900 °C, the macroporous Li1.2Mn0.54Ni0.13Co0.13O2 delivers a high discharge capacity of 220.2 mA h g−1 at a current density of 200 mA g−1 with a capacity retention of 89.1% after 50 cycles, 129.8 mA h g−1 at a current density of 2000 mA g−1 and almost no capacity fading after 120 cycles. The diffusion coefficients of Li+ in the Li-rich layered oxide determined by galvanostatic intermittent titration technique are in the range of 5.0 × 10−18−8.0 × 10−14 cm2 s−1. Electrochemical impedance spectroscopy indicates that the macroporous structure with good particle contact of the layered oxide can improve its rate capability and cyclic stability.
•Macroporous LiLi0.2Mn0.54Ni0.13Co0.13O2 is synthesized via aerogel template.•High discharge capacity of 244.0 mA h g−1 is obtained at 1 C for LMNCO-800.•For LMNCO-900, 220.2 mA h g−1 is obtained at 1 C with enhanced cycle stability.•Capacity of 129.8 mA h g−1 is obtained at 10 C without any fading after 120 cycles.
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Exploring high performance cathode materials is of great means for the development of bi-functional electrochromic energy storage devices. Herein, Nb-doped WO3 mesoporous films as ...integrated high-quality cathode are successfully constructed via a facile sol-gel method. Chemical state and crystallinity of the WO3 based films are significantly influenced by doping concentration. Compared with the pure WO3, 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 WO3 mesoporous cathode. Our research paves the way for the development of multifunctional photoelectrochemical energy devices.
Surface modified-LiV3O8 cathode materials with Al2O3 are successfully synthesized via a facile thermolysis process. The 0.5 wt.% Al2O3-coated LiV3O8 exhibits an enhanced cyclic stability at various ...charge-discharge current densities. At a current density of 100 mA ga1, it delivers an initial specific discharge capacity of 283.1 mAh ga1 between 2.0 and 4.0 V. Moreover, high capacities of 139.4 and 118.5 mAh ga1 are obtained at the 100th cycle at current densities of 2000 and 3000 mA ga1, respectively. The improved electrochemical performance is attributed to the Al2O3 coating, which can hinder the irreversible phase transformation and act as a protective layer to prevent the active material from direct contact with electrolyte. Furthermore, the formation of a LiaVaAlaO solid solution at the LiV3O8/Al2O3 interface provides a fast Li+ diffusion path which is of benefit to the electrochemical behaviors.
Highly porous nickel oxide thin films were prepared on ITO glass by a simple chemical bath deposition (CBD) method in combination with a following heat-treatment process. XRD analysis revealed that ...the as-deposited precursor film contained
β-Ni(OH)
2 and
γ-NiOOH, and they changed to cubic polycrystalline NiO after annealing. The FTIR results showed presence of free hydroxyl ion and water in the NiO thin films. The electrochromic properties of NiO thin films were investigated in an aqueous alkaline electrolyte (1
M KOH) by means of transmittance, cyclic voltammetry (CV) and chronoamperometry (CA) measurements. The NiO thin film annealed at 300
°C exhibited a noticeable electrochromism and good memory effect. The coloration efficiency was calculated to be 42
cm
2
C
−1 at 550
nm, with a variation of transmittance up to 82%. The porous NiO thin films also showed good reaction kinetics with fast switching speed, and the coloration and bleaching time were 8 and 10
s, respectively.
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.
CoFe2O4 flower-like microspheres were synthesized by a controlled AA-assisted hydrothermal process and subsequent annealing. The discharge capacity and cycle stability were greatly enhanced. Display omitted
•We prepared CoFe2O4 flower-like microspheres via a AA-assisted method.•The microspheres are assembled by numerous porous and inter-connected lamella structures.•The electrode shows high capacity, good cycle stability and enhanced rate performance.
Vertically aligned hierarchical WO3 nano-architectures on transparent conducting substrate (3×2.5cm2 in size and sheet resistance Rs=10Ω) are produced via a template-free solvothermal method. The ...nanostructured array films with thicknesses of about 1.1μm show remarkable enhancement of the electrochromic properties in visible spectrum and infrared region. In particular, a significant optical modulation (66.5% and 66.0% at 633nm, 73.8% and 53.9% at 2000nm, 57.7% and 51.7% at 8μm), fast switching speed (4.6s/3.6s and 2.0s/3.4s), high coloration efficiency (126 and 120cm2C−1 at 633nm) and excellent cycling stability (maintained 77.5% and 81.7% of the initial optical modulation after 4500-cycles) are achieved for the nanotree and nanowire arrays, respectively. The improved electrochromic properties are mainly attributed to the vertically aligned structure and the porous space among the nanotrees or nanowires, which make the diffusion of H+ in these arrays easier and also supply larger surface area for charge-transfer reactions.
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•Vertically aligned WO3 nano-architectures are produced via a solvothermal method.•WO3 nano-architectures exhibit significant optical modulation and fast switching speed.•High coloration efficiency and excellent cycling performance are achieved for the nano-architectures.
In this paper, the effect of constraint induced by the crack depth on creep crack-tip stress field in compact tension (CT) specimens is examined by finite element analysis, and the effect of creep ...deformation and damage on the Hutchinson–Rice–Rosengren (HRR) singularity stress field are discussed. The results show the constraint induced by crack depth causes the difference in crack-tip opening stress distributions between the specimens with different crack depth at the same
C*. The maximum opening stress appears at a distance from crack tips, and the stress singularity near the crack tips does not exist due to the crack-tip blunting caused by the large creep deformation in the vicinity of the crack tips. The actual stress calculated by the finite element method (FEM) in front of crack tip is significantly lower than that predicted by the HRR field. Based on the reference stress field in the deep crack CT specimen with high constraint, a new constraint parameter
R is defined and the constraint effect in the shallow crack specimen is examined at different distances ahead of the crack tip from transient to steady-state creep conditions. During the early stages of creep constraint increases with time, and then approaches a steady state value as time increases. With increasing the distance from crack tips and applied load, the negative
R increases and the constraint decreases.
In this paper, we report a facile method to produce large-area periodical bowl-like cobalt oxide (Co3O4) array films based on a self-assembled monolayer polystyrene sphere template and ...electrodeposition. After the template is removed, the resulting Co3O4 films consist of periodic, interconnected networks of monodisperse submicrometer pores with a diameter of 1 μm. Moreover, the individual bowl contains a large number of pores with a diameter of 50 ± 20 nm and the interstices between bowls are filled with Co3O4 nanoflakes. As a preliminary test, the electrochromic properties of the Co3O4 macrobowl arrays have been investigated and it is found that the film annealed at lower temperature exhibits better electrochromic performance. The Co3O4 array film annealed at 200 °C exhibits good electrochromism with color changes from dark gray to pale yellow and fast response times. The coloration efficiency is calculated to be 29 cm2 C−1 at 633 nm, with a variation of transmittance up to 33%.
A three-dimensional (3D) porous nano-Ni supported Si composite film is successfully fabricated by the combination of hydrogen bubble template electrodeposition of porous nano-Ni film and ...radiofrequency magnetron sputtering amorphous silicon. As anode for lithium-ion batteries, the 3D porous Ni/Si composite film shows noticeable electrochemical performance with high capacity of 2444mAhg−1 at a current density of 0.84Ag−1, superior capacity retention of 83% after 100 cycles, as well as excellent rate capability with 1420 and 1273mAhg−1 at charge–discharge current densities of 4.2Ag−1 and 8.4Ag−1 after 100 cycles, respectively. The enhanced electrochemical performance is mainly attributed to the highly porous conductive architecture, which provides good mechanical support and electron conducting pathway for active silicon and alleviates the structure degradation caused by volume expansion during the cycling process.
► We synthesize a unique 3D porous nano-Ni supported Si composite film. ► A high capacity of 2444mAhg−1 can be obtained at 0.84Ag−1. ► 83% of capacity is retained after 100 cycles at 0.84Ag−1. ► The film shows excellent rate capability at 4.2Ag−1 (1420mAhg−1) and 8.4Ag−1 (1273mAhg−1).
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