PVC–PMMA composite electrospun membranes as polymer electrolytes for polymer lithium-ion batteries

Composite nanofibrous membranes based on poly (vinyl chloride) (PVC)?Cpoly (methyl methacrylate) (PMMA) were prepared by electrospinning and then they were soaked in liquid electrolyte to form polymer electrolytes (PEs). The introduction of PMMA into the PVC matrix enhanced the compatibility between the polymer matrix and the liquid electrolyte. The composite nanofibrous membranes prepared by electrospinning involved a fully interconnected pore structure facilitating high electrolyte uptake and easy transport of ions. The ion conductivity of the PEs increased with the increase in PMMA content in the blend and the ion conductivity of the polymer electrolyte based on PVC?CPMMA (5:5, w/w) blend was 1.36?×?10^?3 S cm^?1 at 25?°C. The polymer electrolyte based on PVC?CPMMA (5:5, w/w) blend presented good electrochemical stability up to 5.0?V (vs. Li/Li⁺) and good interfacial stability with the lithium electrode. The promising results showed that nanofibrous PEs based on PVC?CPMMA were of great potential application in polymer lithium-ion batteries.     

Novel electrospun PAN�CPVC composite fibrous membranes as polymer electrolytes for polymer lithium-ion batteries

Composite fibrous membranes based on poly(acrylonitrile)(PAN)-poly(vinyl chloride)(PVC) have been prepared by electrospinning. The fibrous membranes are made up of fibers of 850- to 1,300-nm diameters. These fibers are stacked in layers to produce a fully interconnected pore structure. Polymer electrolytes were prepared by immersing the fibrous membranes in 1 M LiClO₄-PC solution for 60 min. The condition of pure PAN polymer electrolytes is jelly, which has poor mechanical performance and cannot be used. But when PVC with a good mechanical stiffener was added to PAN, the condition of composite PAN?CPVC polymer electrolytes becomes free-standing. In addition, the optimum electrochemical properties have been observed for the polymer electrolyte based on PAN?CPVC (8:2, w/w) to show ionic conductivity of 1.05?×?10^?3 S cm^?1 at 25 °C, anodic stability up to 4.9 V versus Li/Li⁺, and a good compatibility with lithium metal resulting in low interfacial resistance. The promising results showed that fibrous PEs based on PAN?CPVC (8:2, w/w) have good mechanical stability and electrochemical properties. This shows a great potential application in polymer lithium-ion batteries.     

A twins-structural Sn@C core–shell composite as anode materials for lithium-ion batteries

In this paper, we report a facile method to prepare a twins-structural Sn@C core–shell composite that is used as anode materials for lithium-ion batteries. Its surface morphology and microstructures were characterized by the scanning electron microscope, X-ray diffraction, and transmission electron microscope. The electrochemical performances of Sn@C were measured by charge–discharge tests, cyclic voltammogram, and electrochemical impedance spectra. It is shown that such a composite exhibits a high initial specific capacity of 970 mA h g^?1 and a capacity retention of 400 mA h g^?1 after 50 cycles at the current density of 100 mA g^?1.     

Effect of mixed cations in synergizing the performance characteristics of PVA-based polymer electrolytes for novel category Zn/AgO polymer batteries—a preliminary study

Thin films of polymer electrolytes comprising of PVA and KOH (A) with and without the addition of zinc salts, viz., zinc acetate (B) and zinc triflate (C) as mixed cations were prepared via. solution casting method. The thermal stability and ionic conductivity of PVA–KOH solid polymer electrolyte (A) were improved by the partial substitution of KOH with zinc salts. Among the two salts, zinc triflate was found to improve both the physical as well as electrochemical properties of the PVA–KOH films more significantly than zinc acetate. An attempt to optimize the ratio of various components of polymer electrolytes, viz., polymer: KOH: zinc salt was also made, based on the dimensional stability and ionic conductivity values. Finally, the select category polymer film containing PVA–KOH–zinc triflate (C) in an optimum ratio of 40:35:25 was deployed in coin cell fabrication and subjected to charge–discharge studies with a view to demonstrate the possible electrochemical reversibility characteristics. Based on the encouraging results obtained from the cycling study, C type films [PVA–KOH–zinc triflate] qualify themselves as potential polymer electrolytes for use in rechargeable Zn/AgO polymer batteries.     

Two-dimensional PC_3 as a promising anode material for potassium-ion batteries: First–principles calculations

With the diversified development of the battery industry, potassium-ion batteries(PIBs) have aroused widespread interest due to their safety and high potassium reserves on earth. However, the lack of suitable anode materials limits their development and application to a certain extent. Based on first-principles calculations, we investigate the possibility of using PC_3 monolayer as the anode material for PIBs. PC_3 sheet has excellent electrical properties and meets the prerequisite of anode materials. The storage capacity of potassium is as high as 1200 m Ah·g~(-1), which is better than many other reported potassium-ion anode materials. In addition, the outstanding advantages of PC_3 sheet, such as low diffusion barrier and moderate open-circuit voltage, make it a potential anode candidate for PIBs.     

Crystalline Sb–Cu alloy films as anode materials for Li-ion rechargeable batteries

A crystalline Sb–Cu alloy is investigated for use in Li-ion rechargeable batteries, and its structural, electrochemical and thermal properties are characterized. A pulse electrodeposition method is used to prepare Sb–Cu alloy film on Cu foil as a negative electrode. The structure of the alloy film electrode is characterized using XRD, FE-SEM and EDX. The electrochemical behavior of the Sb–Cu alloy film is investigated at the current rate of 0.1C to the cut-off potential range of 1.8 and 0.01 V vs. Li/Li⁺. Our experimental results demonstrate that the initial discharge capacity is 850 mAh g^?1 and that the discharge capacity increases to 1034 mAh g^?1 at the end of the 30th cycle with a stable cycle life. The Coulombic efficiency is approximately 83.5% with good cyclability. Moreover, the crystalline Sb–Cu alloy film has relatively low exothermic properties, and it may be an interesting candidate for use in the negative electrodes of Li-ion batteries.     

Weighted-density approaches for polymer structure at solid–polymer interfaces

Weighted-density approximations (WDAs), which are based on the weighting function for the second-order direct correlation functions (DCFs) of the uniform polymeric fluids, have been developed to investigate the structural and thermodynamic properties of polymer melts at interfaces. The advantage is the simplicity of calculation of the weighting functions and their accuracies in the applications. They were applied to study the local density distributions and adsorption isotherms of the freely jointed tangent hard-sphere chain, Yukawa chain, and hard-sphere chain mixture in slit pores. The polymer reference interaction model (PRISM) integral equation with the Percus–Yevick (PY) closure has been used to calculate the second-order DCF of the polymeric fluids required as inputs. The mean-field approximation (MFA) has been used to calculate the weighting function for the attractive contribution of a freely jointed tangent Yukawa chain fluid, having attraction among the beads. The calculated results show that (i) for the freely jointed tangent hard-sphere chain, the present theory is in excellent agreement with the computer simulations over a wide range of chain lengths and bulk densities, (ii) the WDA approach for the attraction provides an accurate method for the local density distributions of a freely jointed tangent Yukawa chain fluid, and that (iii) the present theory also yields a reasonably good result for the structural properties of the freely jointed hard-sphere chain mixtures composed of the chain and monomer.     

Fabrication of ceramic oxide-coated SWNT composites by sol–gel process with a polymer glue

The functional copolymer bearing alkoxysilyl and pyrene groups, poly[3-(triethoxysilyl)propyl methacrylate]-co-[(1-pyrene-methyl) methacrylate] (TEPM₁₃-co-PyMMA₃), was synthesized via atom transfer radical polymerization. Attributing the π–π interaction of pyrene units with the walls of single-walled carbon nanotubes (SWNTs), this polymer could disperse and exfoliate SWNTs in different solvents through physical interaction as demonstrated by TEM, UV/Vis absorption, and FT-IR analysis. The alkoxysilyl groups functionalized SWNTs were reacted with different inorganic precursors via sol–gel reaction, and, as a results, silica, titania, and alumina were coated onto the surface of SWNTs, respectively via copolymers as a molecular glue. The nanocomposites of ceramic oxides/SWNTs were characterized by SEM analysis. Dependent upon the feed, the thickness of inorganic coating can be tuned easily. This study supplies a facile and general way to coat SWNTs with ceramic oxides without deteriorating the properties of pristine SWNTs.     

A novel approach to a Brillouin–LIDAR for remote sensing of the ocean temperature

Ocean temperature profiles are of great importance in oceanography. For instance, an efficient remote sensing measurement technique of these profiles will facilitate climate studies and improvements in weather forecast. In this paper we describe developments towards a practical implementation of a Brillouin–LIDAR system capable of measuring temperature profiles in the ocean. In particular, we focus on our recent work on fiber amplifiers and a receiver unit based on a Faraday anomalous dispersion optical filter. PACS 42.79.Qx; 42.60.By; 42.62.Fi; 42.68.Xy; 42.50.Nn     

Novel silicon–oxygen–carbon composite with excellent cycling steady performance as anode for lithium-ion batteries

The novel anode material for lithium-ion batteries, silicon–oxygen–carbon (Si–O–C) composite, is prepared by a liquid solidification combined with following pyrolysis process, in which silicon dioxide (SiO₂) is used as an additive agent to enhance the electrochemical performance of the composite. While the structure of the composite is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectra (FT-IR), the morphology and microstructure were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. SEM and TEM observations reveal that the Si–O–C powders are about 1 μm in diameter, and there is a homogenous pyrolyzed carbon layer about 5 nm thick on the surface of the particle. The Si–O–C sample as anode material can deliver a high initial charge capacity of 753.4 mAh g^?1, and the capacity keeps above 500.0 mAh g^?1 after 40 cycles at 100.0 mA g^?1. The electrochemical impedance spectroscopy results show that the composite exhibits lower charge transfer resistance and higher lithium-ion diffusion rate compared with the Si–C anode, which indicates that the composite Si–O–C could be used as a promising anode material for lithium-ion batteries.

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Graphical Abstract SEM images of the Si-C (a) and Si-O-C (b) samples and the TEM (c) and HRTEM (d) image of the Si-O-C sample

     

A novel resource management scheme for virtualized cyber–physical–social system

Cyber–physical–social systems (CPSSs) can realize the coordination of the physical world, cyber space, and society. This article presents a virtualized CPSS architecture with a user incentive scheme. The proposal supports the dimension-extended resource management for virtualized CPSSs, where humans are viewed as an additional network resource to be jointly optimized with other resources, i.e., communication, caching, and computing resources. The proposal aims at maximizing the profit of the virtual CPSS operator based on the average spectrum efficiency and user reputation and capability evaluation. Simulation results indicate that the proposal can fully mobilize high-quality users and meanwhile provide superior services to them; thus it can motivate humans to regularize or modify their behaviors in the direction of improvement in overall revenue.     

A carbon–LiFePO<Subscript>4</Subscript> nanocomposite as high-performance cathode material for lithium-ion batteries

A cathode material of an electrically conducting carbon–LiFePO₄ nanocomposite is synthesized by wet ball milling and spray drying of precursor powders prior to a solid-state reaction. The structural characterization shows that the composite is composed of LiFePO₄ crystals and 4.8 wt.% amorphous carbon. Galvanostatic charge/discharge measurements indicate that the composite exhibits a superior high energy and high cycling stability. This composite delivers a discharge capacity of 159.1 mAh g⁻¹ at 0.1 C, 150.8 mAh g⁻¹ at 1 C, and 140.1 mAh g⁻¹ at 2 C rate. The capacity retention of 99% is achieved after 200 cycles at 2 C. The 18,650 cylindrical batteries are assembled using the composite as cathode materials and demonstrate the capacity of 1,400 mAh and the capacity retention of 97% after 100 cycles at 1 C. These results reveal that the as-prepared LiFePO₄–carbon composite is one of the promising cathode materials for high-performance, advanced lithium-ion batteries directed to the hybrid electric vehicle and pure electric vehicle markets.     

A terabit capacity passive polymer optical backplane based on a novel meshed waveguide architecture

An optical backplane based on a meshed polymer waveguide architecture enabling high-speed board-to-board optical interconnection is presented. This planar array of multimode polymer waveguides can provide passive strictly non-blocking links between server line cards fitted with optical transmitter and receiver arrays. This architecture offers a scalable and low-cost solution to the bandwidth limitations faced by electrical backplanes and is suitable for PCB integration. The reported backplane demonstrator uses a matrix of 100 waveguides each capable of 10 Gb/s operation to interconnect 10 cards for a total capacity of a terabit per second aggregate data rate in multicast mode. Characterisation of the backplane demonstrator reveals low link losses of 2 to 8 dB for a multimode fibre input and crosstalk values below −35 dB. Error free data transmission at 10 Gb/s is achieved with a power penalty of only 0.2 dB at a bit-error-rate of 10⁻⁹. Additionally, lossless operation of a Gigabit Ethernet link over the backplane is achieved even when using the worst-case highest loss links.     

NiFe LDH-CoPc/CNTs as novel bifunctional electrocatalyst complex for zinc–air battery

A new type of composite electrocatalyst was designed and prepared with NiFe layered double hydroxides (LDHs) for oxygen evolution reaction (OER) and CoPc for oxygen reduction reaction (ORR) supported on carbon nanotubes (CNTs). The NiFe LDH–CoPc/CNT composite exhibits higher electrocatalytic activity and stability than the commercial precious metal catalyst Pd/C + Ru/C in 6 M KOH electrolyte. The resulting rechargeable Zn–air battery showed high discharge voltage at 195 mW cm^?2. The discharge voltage is around 1.08~0.95 V and the charge voltage is lower, 2.07 V, after the cycle of 300 h at 80 mA cm^?2, indicating that zinc–air battery possessed high reversibility and durability over long charge and discharge cycles.     

A novel fluid–wall heat transfer model for molecular dynamics simulations

The ‘fluid–wall thermal equilibrium model’, to numerically simulate heating/cooling of fluid atoms by wall atoms, is used to compare molecular dynamics simulation results to the analytical solution of 1-D heat equation. Liquid argon atoms are placed between two platinum walls and simultaneous heating and cooling is simulated at the walls. Temperature gradient in liquid argon is evaluated and the results are found to match well with the analytical solution showing the physical soundness of the proposed model. Additional simulations are done where liquid argon atoms are heated by both the walls for two different channel heights and it is shown that in such cases, heat transfer occurs at a faster rate than predicted by heat equation with decreasing channel heights.     

A novel radiant source for infrared calibration by using a grooved surface

A radiant source with a large aperture at 5-95℃ in the wavelength bands of 8-12 μm for calibrating infrared imaging systems has been designed. The effective emissivity of its flat bottom with concentric V-grooves was evaluated by the Monte-Carlo method whose correctness was tested and accuracy was discussed. The structure of the source was completed by incorporating the simulation results with the blackbody cavity effect. The source was certificated via an optical measurement system. The source can provide a consistent radiant flux with temperature uniformity of ±0.1 ℃ over an area of diameter of φ80 mm.     

A novel polarization modulator for a moiré system with grating imaging

Displacement measurements and position sensing have been playing an important role in many fields such as fabrication, biophysics, and autocontrol. Interferome- try, laser triangulation, optical fiber sensing and moiré technique are common optical measuring methods[1-3]. Among these methods, moiré technique holds the most interest due to its high accuracy, large range, low cost, and other advantages. When a long working distance is required, or when space is not at a premium, a moiré sys- t…