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Silicon oxycarbide (SiCO), made from the polymer route from siloxane-based precursors, has impressive capacity for serving as anodes in Li+ batteries. However, the voltage–charge cycle exhibits significant hysteresis: the magnitude of the insertion voltages is low, while the extraction voltages are high. Here, we present coulometric titration results on both traverses of the cycle that lead to a measurement of an intrinsic polarization within the half-cell. This polarization-potential, which is measured to be 250–500mV, is attributed to a differential between the potential of Li ions across the anode–electrolyte interface. In the second set of experiments the polarization was measured after coating the powders of the active anode material with a few monolayers of alumina by atomic-layer deposition (ALD). These results showed a shift of the hysteresis curve by ∼50mV, which is attributed to a space–charge double layer, most likely at the alumina–electrolyte interface. In the third result, the distribution of the “density of states” at different voltage levels where Li is inserted, and extracted, from SiCO is measured. The distribution is broad reflecting the amorphous nature of SiCO, and consistent with the strongly sloping behavior of the voltage–charge capacity profile of the charge–discharge cycle.
New ternary polymer electrolytes based on a commercial cross-linking resin dianol diacrylate (DDA), tetramethylene sulphone (TMS) as a compatibilizing solvent and ionic liquids (ILs) were prepared by in situ photopolymerisation. The electrolytes containing two polymer-to-TMS-to-IL ratios, 20:30:50 and 20:20:60 by weight, respectively and six various ILs were investigated. The obtained materials were flexible, self-standing with good mechanical properties and a long-term stability. They showed high ionic conductivities, in the range of ca. 7×10−3 to 3×10−2 Scm−1 at 25°C. A very important result is that the conductivities of all the prepared polymer electrolytes exceeded the conductivities of the corresponding neat ILs by 2–3.5 times. The temperature dependence of the ionic conductivity correlates with VTF equation. All the materials prepared were characterized by a broad electrochemical stability window (3.3–3.7V).
Carbon aerogel (CA) with ultra-low density and three dimensional network nanostructures is investigated as the electrocatalyst for tri-iodide (I3 −) reduction in dye-sensitized solar cells (DSSCs). The catalytic properties of CA and platinum (Pt) counter electrodes are analyzed and compared by electrochemical impedance spectroscopy (EIS) and Tafel polarization measurements. The devices applying CA counter electrode exhibit a lower charge-transfer resistance (1.60Ωcm2) and larger diffusion coefficient (3.39×10−6 cm2 s−1) compared to the devices with conventional Pt counter electrode. As a new kind of porous carbon materials, CA counter electrode has high active surface area and conductance. These factors improve the power conversion efficiency (η) up to 8.04%, which is better than that of the reference Pt based DSSC (6.79%). This paper indicates that carbon aerogel with good catalytic activity can potentially be used as a promising alternative to the expensive Pt counter electrode in a high-performance DSSC device design.
This paper presents small-signal modeling, analysis and closed-loop controller design guidelines for a distributed battery energy storage system with energy sharing controller which has recently been presented in the literature in order to achieve cell balancing with high cell balancing speed and energy efficiency. The derived small signal models provide deeper insight into the dynamics of the energy sharing controlled battery system under different operating modes, including discharge mode, constant current charging mode and constant voltage charging mode. Based on the derived small signal models, closed-loop controller design guidelines are provided based on rule-of-thumb frequency-domain design criteria. The small signal models and designed controllers are validated by MATLAB®/SIMULINK simulation and experimental prototype results.
This paper puts forward to Fuzzy Logic MPPT (Maximum Power Point Tracking) method applied photovoltaic panel sourced boost converter, under variable temperature (25–60°C) and irradiance (700–1000W/m2) after that the PI control was applied buck converter to behave as a charge controller. The voltage and current of PV panels are nonlinear and they depend on environmental conditions such as temperature and irradiance. Variable environmental conditions cause to change voltage, current and also cause to change maximum available power of PV panels. To increase efficiency and decrease payback period of the system, it needs to operate PV panels at maximum power point (MPP). Under any environment conditions there is unique MPP. To operate PV panels at that point (MPP) there are many MPPT method in literature, FLC MPPT method was preferred in this study because, its rapid response to changing environmental conditions and not affecting by change of circuit parameters. The accuracy of FLC MPPT method used in this system to find MPP changes, from 94.8% to 99.4%. To charge a battery there are two traditional methods which are constant current (CC), and constant voltage (CV) methods. For fast charging with low loss constant current and voltage source is a need. One of the methods providing constant is PI control which used in this study. PI control is not only well developed and a simple technique but also it provides satisfactory results. The goal of this study is operating PV panel at maximum power point under variable environment conditions to increase efficiency and reduce cost and also provide appropriate current and voltage for charging battery to charge quickly, reduce losses and also increase life cycle of battery. This system was established and analyzed in MATLAB/Simulink.
In this paper, we propose a Cooperative Energy-Efficient Localization Framework (CELF) for power saving in mobile long-thin networks (MLTNs). We use the cycling ad hoc network with fleet cyclists using mobile phones along a common cycling route as an example (our results could be applicable to other scenarios as well, such as the mountaineering party and army troops). As cyclists need to upload their position data and download global fleet information, all power-consuming GPS receivers have to be switched on for obtaining their current locations. In CELF, distributed localization among cyclists without central control is designed to minimize the energy consumption of positioning. To the best of our knowledge, CELF is the first distributed solution for localization which provides the following features: (i) CELF does not rely on costly roadside infrastructures but only employs cyclist-to-cyclist communications; (ii) CELF can supply group members with the up-to-date locations without activating GPS receivers; (iii) CELF can estimate member positions only based on single mobile anchor instead of multiple static anchors. Simulation and experimental results show that CELF outperforms existing works, which can significantly reduce the energy consumption for localization while keeping the positioning accuracy similar to GPS.
Room temperature rechargeable magnesium (Mg) batteries are constructed from Mg as a negative material, sulfur (S)-containing composite prepared from elemental sulfur and the bis(alkenyl) compound having a crown ether unit (BUMB18C6) or linear ether unit (UOEE) as a positive material and the simple electrolyte (0.7 mol dm−3 Mg[N(SO2CF3)2]2-triglyme (G3) solution). The reaction between molten S and the bis(alkenyl) compound (BUMB18C6 or UOEE) provides the sulfur-containing composite, S-BUMB18C6 or S-UOEE. Both of the sulfur-containing composites are electrochemically active in the Mg salt-based electrolyte, acetonitrile- or G3- Mg[N(SO2CF3)2]2 electrolyte. The first discharge capacity of the test cells with the sulfur-containing composite is 460 Ah kg−1 (per the weight of sulfur in the composite) with the S-BUMB18C6 electrode and 495 Ah kg−1 with the S-UOEE electrode. According to the continuous charge–discharge cycle tests (at 10th cycle), the discharge capacity of the test cell with the S-BUMB18C6 electrode (68.1 Ah kg−1) is higher than that with the S-UOEE electrode (0.18 Ah kg−1). The crown ether units in the S-BUMB18C6 composite may create ion-conducting paths in the cathode, prevent rise in the internal resistance of the cathode, and provide better cycle performance of the test cells with the S-BUMB18C6 composite electrode than that with the S-UOEE electrode.
Li1.3Ni x Co y Mn1−x−y O2.4 (typically Li1.3Ni1/6Co1/6Mn4/6O2.4, Li1.3Ni1/5Co1/10Mn7/10O2.4 and Li1.3Ni1/4Mn3/4O2.4) cathode materials have been synthesized by microwave irradiation at 800°C in a rapid calcination period of 1.5h. The influence of transition metal ratios on the structure and electrochemical performance of the samples have been carefully investigated by powder X-ray diffraction (XRD) together with Rietveld refinement, inductive coupled plasma (ICP), scanning electron morphology (SEM), galvanostatically charge/discharge test, cyclic voltammetry (CV) in conjunction with electrochemical impedance spectroscopy (EIS) measurements. The as-prepared Li1.3Ni1/6Co1/6Mn4/6O2.4, Li1.3Ni1/5Co1/10Mn7/10O2.4 and Li1.3Ni1/4Mn3/4O2.4 materials can deliver discharge capacities of 291, 287 and 217mAhg−1, respectively, at a charge/discharge current density of 12.5mAg−1 in the voltage range of 2.5-4.7V. These cathode materials have a relatively small initial irreversible capacity loss (around 50mAhg−1), comparing with the commonly reported values (70–100mAhg−1). When the charge/discharge current density increases to 50mAg−1, they have initial discharage capacities of 267, 236 and 166mAhg−1, which are 92%, 82% and 76% of the corresponding capacity values at 12.5mAg−1. The Li1.3Ni1/6Co1/6Mn4/6O2.4 cathode exhibits the largest discharge capacity value and best rate capability due to the highest hexagonal ordering, the lowest cation mixing, content of spinel impurity phase, and charge transfer resistance. The cobalt-free cathode material, Li1.3Ni1/4Mn3/4O2.4, shows better cycling performance than the cobalt-contained counterparts.
Nano γ-nickel oxyhydroxide (nano γ-NiOOH), intended as a new positive electrode material for alkaline Zn/Ni batteries, was synthesized by a sonochemical intercalation method. Using NaClO as oxidant, 5M NiCl2 solution was added dropwise to a concentrated alkaline solution of NaClO+NaOH, which allows all four elementary reactions (precipitation, oxidation, cation exchange, and water molecule intercalation) to proceed simultaneously under low-frequency ultrasonic irradiation. XRD, SAXS, TEM, SEM, AAS, IR, TG, CT (complexometric titration), cyclic voltammetry (CV), and a charge–discharge test of imitative cell have been used to characterize the microstructural characteristics, composition and electrochemical properties of the synthesized material. The results showed that the lattice parameters of nano γ-NiOOH are a =2.8256Å and c =20.7938Å. The average oxidation state of Ni in the sample is 3.65 as measured by an indirect iodine method. The alkali metallic Na+ ions and water molecules have been inserted into sites between NiO2 layers. The cyclic voltammogram of nano γ-NiOOH exhibited two cathodic peaks and two anodic peaks, which is in accord with the redox reaction between the various phases of Ni(OH)2 and NiOOH. The charge–discharge test of imitative cells revealed that nano γ-NiOOH exhibited a higher discharge capacity than spherical β-NiOOH.
Polyvinylpyrrolidone (PVP) is used with polyethylene oxide (PEO) as a mixed binder for mechanically milled Li2S. PVP demonstrates its advantage in terms of increasing the capacity of Li2S, but boosts the potential barrier at the beginning of the first charge. It is also revealed that PVP retards the charge-transfer kinetics of Li2S. In Li2S-C prepared by mechanical milling, carbon compensates for the electrochemical insulation of the PVP binder and improves the cycle stability. As a result, the Li2S-C-PVP electrode with 60 wt% Li2S content displays a low potential barrier at the onset of charge and a stable capacity of about 460 mAh g−1 at 0.1 C.
Metal binary sulfides (TiS2, FeS2), in either powder or thin film forms, were the first studied Li insertion electrodes for rechargeable lithium batteries, with thin films made mainly by sputtering. Here we exploit the equilibrium solubility of molecular sulfur into ionic liquids at its melting point (120°C), which we estimated to be at a maximum level of 80mM by both electrochemical and microwave studies, to prepare thin films of both Co9S8 and FeS x showing initial capacities of 559mAhg−1 and 708mAhg−1 versus lithium in coin cells, respectively. We demonstrate that the growth of Co9S8 films involves the reaction of soluble sulfur with the electrodeposited Co metallic layer, while the formation of FeS x films enlists a precipitation between the reduced Fe(II) cations and the electrochemically produced S x y− species in the ionic liquid bath. Such findings, namely the solubility of sulfur into ionic liquids, open opportunities to electrodeposit sulfur-based compounds as well as capture sulfur from various media enabling a better environment.
Umicore and Evonik plan to supply Li-ion batteries for electric vehicles. Umicore and Evonik Group subsidiary Evonik Litarion GmbH have formed a business relationship to supply lithium-ion cathode materials. Evonik has selected Umicore as the supplier of cathode materials for large-format Li-ion batteries that are used in electric vehicles and in energy storage systems for stationary applications. Evonik manufactures battery cell components for the batteries. Umicore's Cellcore MX, a Li-ion NMC (nickel, manganese, cobalt) cathode material, can help improve power, energy, safety and battery cycle life in electric vehicles, the company says. “Through its materials know-how, extensive production capacity, sustainable sourcing and manufacturing process, Umicore serves for us as an ideal partner for our business,” said Dr Henrik Hahn, spokesman of the board of management of Evonik Litarion GmbH. According toDr Kurt Vandeputte, senior business director for Umicore's rechargeable battery materials business unit: “We are delighted to be selected by a major producer in the emerging European market for large-format lithium-ion rechargeable batteries. This is a strong signal of recognition for our expertise, and it reinforces our long-term commitment towards Li-ion technology as an enabler for electrified transportation.”
Mesoporous Sn/SnO2/carbon composites with uniformly Sn/SnO2 embedded within the carbon pore walls have been rationally designed and synthesized. These nanocomposites have been characterized by XRD, SEM, TEM, XPS and tested as negative electrodes in a cell using lithium foil as the counter electrode. The inclusion of metallic Sn in SnO2/CMK-3 resulted in a unique, ordered structure and provided a synergistic effect which resulted in an impressive initial reversible capacity of 799mAhg−1. In addition, at a higher current of 800mAg−1, the heterostructure was able to provide a stable capacity of 350mAhg−1. Furthermore, a retention capacity of ∼670mAhg−1 was obtained after 60 cycles.
Uniform single-crystalline SnS nanobelts have been prepared via a simple wet-chemical route, in which SnCl2 was used as tin source and Na2S as sulfur source. Direct conversion of these SnS nanobelts with two pyramidal tips to porous-walled SnO2 nanocapsules was achieved by oxidizing in atmospheric ambient at 500–700°C. The formation mechanism of these porous nanocapsules is a combination of non-equilibrium interdiffusion, volume loss, and gas release. With these uniform SnS nanobelts as precursors, carbon-coated metal Sn nanorods (Sn@C core-shell structure) were also synthesized by decomposition of sulfide SnS nanobelts with carbon coatings in N2 atmosphere. A strong UV emission peak at 365nm is demonstrated for the SnO2 porous nanocapsules, which makes these promising materials for applications such as optical sensors. Furthermore, energy storage performances of these Sn-based nanomaterials (porous SnO2 nanocapsules and Sn@C core-shell nanocomposites) as anodes for Li-ion batteries were investigated in detail.
We demonstrate a facile hydrothermal synthesis of SnO2/MoO3-x nanocomposites with ultrafine SnO2 crystallites uniformly embedded into an amorphous MoO3-x matrix, which demonstrate superior electrochemical performance as anodes for lithium ion batteries, including long-term cycling stability (953mAh/g after 100 cycles at 200mA/g), high rate capability (668.0mAh/g after 1000 cycles at 1000mA/g) and high initial Coulombic efficiency (81.3% at 200mA/g). Synergistic effects of the both components SnO2 and MoO3-x on the lithium storage are revealed by electrochemical characterization and supported by TEM and XPS analysis performed at the different discharge/charge states of the respective electrodes. SnO2 nanocrystallites confined within the amorphous MoO3-x matrix efficiently buffer the volume changes of Li-Sn alloying-dealloying upon cycling, while the metallic Mo in situ generated by a conversion reaction of MoO3-x promotes the reversible reaction SnO2 +Li+ ↔Sn+Li2O. In addition, the amorphous MoO3-x with bulk or surface defects allows for a better lithium insertion and thus enhanced capacity.
This paper deals with the thermal modeling of a large prismatic Li-ion battery (LiFePO4/graphite). A lumped model representing the main thermal phenomena in the cell, in and outside the casing, is hereby proposed. Most of the parameters are determined analytically using physical and geometrical properties. The heat capacity, the internal and the interfacial thermal resistances between the battery and its cooling system are experimentally identified. On the other hand, the heat sources modeling is considered to be one of the most difficult task. In order to overcome this problem, a heat generation model is included. More specifically, the electrical losses are computed thanks to an electrical model which is represented by an equivalent electric circuit. A method is also proposed for parameter determination which is based on a quasi-steady state assumption. It also takes into account the battery heating during characterization which is the temperature variation due to heat generation during current pulses. This temperature variation is estimated thanks to the coupled thermal and heat generation models. The electrical parameters are determined as function of state of charge (SoC), temperature and current. Finally, the proposed coupled models are experimentally validated with a precision of 1 °C.
LiCoO2/mesocarbon microbeads (MCMB) batteries are over-charged to different voltage (4.4 V, 4.5 V, 4.6 V, and 4.7 V, respectively) for ten times, and then are cycled 1000 times for shallow depth of discharge. The morphology, structure, and electrochemical performance of the electrode materials were studied in detail in order to identify the capacity fading mechanism of over-charged battery after long-term cycling. The cycling performances of LiCoO2/MCMB batteries are gradually aggravated with the increase of over-charging voltage and the degradation mechanism is diverse upon the degree of over-charging. The capacity fading after long-term cycling of battery over-charged to 4.6 V or 4.7 V is mainly attributed to the cathodes. Soft X-ray absorption spectroscopy (XAS) demonstrates that the lower valence state of cobalt exists on the surface of the LiCoO2 after serious over-charging (4.6 V or 4.7 V), and cobalt is dissolved then deposited on the anode according to the result of energy dispersive spectrometry (EDS). However, after shallow over-charging (4.4 V or 4.5 V), the capacity deterioration is proposed as the loss of active lithium, presented by the generation of the SEI film on the anode, which is verified by water washed tests.
Palladium (Pd) incorporated poly (3,4-ethylenedioxythiophene) (PEDOT) films were synthesized through an electrochemical route and characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The electrochemical study showed catalytic oxidation of dopamine (DA) with optimum loading of Pd. DA and uric acid (UA) were detected using differential pulse voltammetry (DPV). In the presence of ascorbic acid (AA), DA-AA showed peak potential separation of 0.19 V while 0.32 V between UA-AA on Pd-incorporated PEDOT. These peak separations are large enough for sensing DA and UA in the presence of AA. DA and UA exhibited linear calibration plots and the minimum detection limits are 0.5 and 7 µM respectively. On Pd-PEDOT, the reversibility of DA oxidation was found to increase compared to bare glassy carbon electrode (GCE) and PEDOT modified GCE. Fouling effects were also found to be minimal making Pd-PEDOT composite suitable for electroanalysis.
Introduction Euxyl K400 is a widely used preservative in cosmetics, topical drugs, cutting fluids, etc. This antimicrobial product has two active components—methyldibromo glutaronitrile (MDGN), also known as 1,2-dibromo-2,4-dicyanobutane, and 2-phenoxyethanol, in a proportion of 1 to 4.The aim of this study was to assess the prevalence of sensitization to this preservative in cases in our dermatology department over a 5-year period. We also assessed the prevalence of sensitization to the two active components of Euxyl K400 and calculated the agreement with sensitization to Euxyl K400. Material and methods In this retrospective study, we analyzed the medical records of 1,092 patients attended in our skin allergy unit between January 2000 and December 2005.We undertook testing with a standard battery that included, in addition to the allergens recommended by the Spanish Group for Research Into Dermatitis and Skin Allergies (GEIDAC), 0.3% MDGN and 1% 2-phenoxyethanol in Vaseline (Trolab®). Results Only 15 patients developed a positive reaction to Euxyl K400. Of these, 11 were positive to MDGN and 2 to phenoxyethanol. Sensitization to Euxyl K400 was significantly more common in men. The agreement between sensitization to Euxyl K400 and MDGN was good (Kp = 0.68), whereas agreement between Euxyl K400 and phenoxyethanol was poor (Kp = 0.23). Conclusions The prevalence of Euxyl K400 sensitization in this study was 1.4%. Most cases of Euxyl K400 sensitization were associated with the MDGN component, as indicated by the good agreement between the two substances.
Graphene/metal oxide nanocomposites are promising electrode materials for lithium-ion batteries (LIBs), in which synergistic effects between the two components may benefit the overall capacity, rate capability and cycling stability. Here, we report a simple and easy scale-up method for the preparation of high-quality reduced graphite oxide-MoO2 (rGO-MoO2) nanobelt composites, which demonstrate attractive electrochemical performance as LIB anodes. MoO3 nanobelts are first prepared by a simple hydrothermal route and distributed homogeneously in water, and then graphite oxide (GO) is prepared by a modified Hummers method and introduced into the solution. Both materials slowly self-assemble to form GO-MoO3 nanocomposite in a surfactant-free manner. After thermal reduction, rGO-MoO2 nanobelt composites are obtained, as confirmed by FE-SEM and TEM. Using such composite as LIB electrodes, a reversible capacity of 754mAhg−1 is obtained after 80 cycles at 0.2Ag−1, and the electrode also demonstrates superior rate capabilities. These results are comparable to or even higher than those of other reported graphene-MoO2 composites, which are fabricated in more complicated fashions, thus rendering the current product as highly promising electrode materials for practical use.