bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Cathode Materials Based on Organic Couples for Lithium Batteries
Authors: Ravet N. , Michot C. , Armand M. 
Published: April 2011

ABSTRACTThe electrochemical reduction of the oxocarbons: squarate, croconate and especially rhodizonate lithium salts have been studied in all solid state lithium batteries. Lithium rhodizonate cells were tested on cycling in the 1.5 – 3.5 V potential range The reduction of lithium rhodizonate occurs in two waves of two electrons. The number of electrons transferred in reduction on the first cycle was around 3.5 based on a capacity of 515 mA.h.g−1 and a discharge depth of 87 %. This process is quite reversible but we observed a fast decline of the capacity on cycling. This loss of capacity may be attributed to residual water in the salt. The reduction of the lithium croconate occurs at a potential of 1.8 V in a quasi-irreversible process. We could not observe the reduction of lithium squarate which occurs in the potential range where the lithium is inserted in carbon black. We also report an investigation on rhodizonate salts of transition metals. The best results, in term of capacity, on the 1.5 – 3.5 V potential range, were obtained with copper rhodizonate which exhibits a capacity of 579 mA.h.g−1 on the first discharge.
Synthesis and Characterization of LiNiO2 as A Cathode Material for Pulse Power Batteries
Authors: Choe H. S. , Abraham K. M. 
Published: April 2011

ABSTRACTThe optimum conditions for preparing LiNiO2 with good electrochemical performance are presented. Three different methods were investigated:• LiOH and NiO at700°C in air(Batch A),• LiOH and NiO between 150 and 750 °C in oxygen (Batch B), and• LiNO3 and NiCO3 between 600 and 750 °C in oxygen (Batch C).Batch C exhibited the highest first discharge capacity of about 150 mAh/g between 2.0 and 4.0V with a solid state Li/LiNiO2 cell containing a PAN-based polymer electrolyte. Solid state carbon/LiNiO2 cells and two-cell bipolar batteries demonstrated high rate capabilities at room temperature with an ability to sustain pulsed discharge currents as high as 50 mA/cm2. About 22 500,13 000, and 1000 pulses were obtained at current densities of 10, 20, and 50 mA/cm2, respectively, with a 10 ms pulse width followed by a 50 ms interpulse rest period.
Hydrothermal Synthesis and Characterization of A Series of Novel Zinc Vanadium Oxides as Cathode Materials
Authors: Zhang Fan , Zavalij Peter Y. , Whittingham M. Stanley 
Published: April 2011

ABSTRACTWe report here the hydrothermal synthesis of a series of novel zinc vanadium oxides, using tetramethyl ammonium ion in order to stabilize the layered structure of vanadium oxide during electrochemical redox reactions with lithium. The compounds were synthesized by the reaction of zinc chloride, vanadium (V) oxide, and tetramethyl ammonium hydroxide at 165°C for 60 hours. Four new zinc vanadium oxide compounds were discovered, only one of which contained the organic cation; another was found to have a layered structure with bridging V-O-V groups analogous to that of beta alumina. These compounds were characterized by X-ray powder diffraction, and IR. Three of the compounds reacted readily with lithium, and their electrochemical behavior in lithium cells were determined.
Lithium Insertion Behaviour of Li1+xV3O8 Prepared by Sol-Gel Method in Methanol
Authors: Kawakita J. , Katayama Y. , Miura T. , Kishi T. 
Published: April 2011

ABSTRACTLi1+xV3O8 (LT-M form) was obtained by sol-gel method in CH3OH. This form, prepared at 350°C, possessed smaller grain size and better electrochemical performance than the HT form prepared by conventional high temperature synthesis. High discharge capacity (372 mAh·g−1: x = 4.0) and reversible discharge and charge cycle were attained. When heated at 200°C, CH3OH molecules remained in the compound and crystallinity became lower by lithium insertion over x = 2.0. The lithium de-intercalation was irreversible.
High Density Active-Site MnO2 Nanofibers for Energy Storage and Conversion Applications
Authors: Xiao T. D. , Reisner D. E. , Strutt P. R. 
Published: April 2011

ABSTRACTThis investigation involves the synthesis of MnO2 nanofibrous materials, via an aqueous chemical synthesis route. A critical step in the synthesis is the extended period of the refluxing of the reactive constituents, which enables the gradual transformation of the initial amorphous nanoparticles into a random-weave nanofibrous structure, in the form of a bird's nest superstructure. The bird's nest has a diameter of approximately 10 μm, which is an assemblage of many individual nanofibers with a diameter of about 15 nm, and a length up to 1 μm. Partial transformation of the nanostructured MnO2 realizes a novel bimodal morphology, which combines a high density of chemically active sites with an enhanced percolation rate. Characterization of these nanofibers include SEM, TEM, surface area, and chemical analysis. High resolution TEM observations reveals that the as-synthesized MnO2 nanofibers contain lattice defects, including molecular pores, meso- and micro-pores.
Amorphous and Nanocrystalline Oxide Electrodes for Rechargeable Lithium Batteries
Authors: Manthiram A. , Kim J. , Tsang C. 
Published: April 2011

ABSTRACTOxo ions (MO4)n- (M = V, Cr, Mn and Mo) have been reduced in aqueous solutions with potassium borohydride to obtain the binary oxides MO2+δ. While the vanadium and manganese oxides are nanocrystalline, the chromium and molybdenum oxides are amorphous. The nanocrystalline VO2 having a metastable structure and the amorphous CrO2 and MoO2.3 transform to the thermodynamically more stable phases upon heating above 300–400 °C. These metastable oxides after heating in vacuum at 200–300 °C to remove water show good electrode performance in lithium cells. VO2, CrO2 and MoO2.3 show a reversible capacity of, respectively, 290 mAh/g in the range 4–1.5 V, 180 mAh/g in the range 3.3–2.3 V, and 220 mAh/g in the range 3–1 V. MnO2 obtained by this process does not show good electrode properties.
Thermal Stability of Lithium Ion Battery Electrode Materials in Organic Electrolytes
Authors: Richard M. N. , Dahn J. R. 
Published: April 2011

AbstractThe technology of lithium ion batteries has been developed so that these systems can be used to power portable electronic devices. The next step is to increase the size of the batteries so that they power larger systems such as electric vehicles. However, before such a step can be taken the thermal stability of any materials placed in such a battery must be determined. Although the thermal properties of the materials are important for the small systems, which can reach high temperatures when abused, they become even more important in large systems where heat dissipation is more difficult because of the physical size of the system. This paper will discuss our approach, which uses an Accelerated Rate Calorimeter, to the study of the thermal behaviour of lithium ion battery electrode materials.
Lithium Ion Diffusion Through Glassy Carbon Plate
Authors: Inaba M. , Nohmi S. , Funabiki A. , Abe T. , Ogumi Z. 
Published: April 2011

ABSTRACTThe electrochemical permeation method was applied to the determination of the diffusion coefficient of Li+ion (DLi+) in a glassy carbon (GC) plate. The cell was composed of two compartments, which were separated by the GC plate. Li+ions were inserted electrochemically from one face, and extracted from the other. The flux of the permeated Li+ions was monitored as an oxidation current at the latter face. The diffusion coefficient was determined by fitting the transient current curve with a theoretical one derived from Fick's law. When the potential was stepped between two potentials in the range of 0 to 0.5 V, transient curves were well fitted with the theoretical one, which gaveDLi+ values on the order of 10−8cm2s−1. In contrast, when the potential was stepped between two potentials across 0.5 V, significant deviation was observed. The deviation indicated the presence of trap sites as well as diffusion sites for Li+ions, the former of which is the origin of the irreversible capacity of GC.
Strontium Ruthenate Perovskites with High Specific Capacitance for use in Electrochemical Capacitors
Authors: Wilde P. M. , Guther T. J. , Oesten R. , Garche J. 
Published: April 2011

ABSTRACTStrontium ruthenates with the perovskite type structure ABO3 have been shown to exhibit attractive capacitive properties. Doping on the A site with La lead to typical capacitance values of 21 F/g. These materials were synthesized by coprecipitating metal hydroxides from a stoichiometric salt solution and subsequent firing at 800 °C in air. In this paper we present a new procedure to synthesize the materials which are crystalline and nevertheless show appreciable capacitances in contrast to ruthenium dioxide material, which only works in a hydrated amorphous structure. The process basically consists in a pyrolysis of concentrated metal salt solutions of the respective chlorides and nitrates at 500 °C for several minutes. Excess soluble phases are removed by washing out with water. X-ray diffraction experiments revealed similar phase purity and crystallinity as known from the coprecipitated materials. However the measured capacitances of undoped perovskites reached high values of 200 F/g exceeding twenty times the value of respective coprecipitated materials. First experiments on doping the materials promise further progress. The new synthesis route introduces a higher surface area by leaving cavities from leached soluble phases and bulk defects into the crystal structure. The first effect increases the number of active sites in contact with the electrolyte while the latter enhances the protonie conduction which is necessary to keep the charge balance within the material during cycling.
Experimental Electrochemical Capacitor Test Results
Authors: Wright R. B. , Murphy T. C. , Rogers Susan A. , Sutula Raymond A. 
Published: April 2011

ABSTRACTVarious electrochemical capacitors (ultracapacitors) are being developed for hybrid vehicles as candidate power assist devices for the Partnership for a New Generation of Vehicles (PNGV) fast-response engine. The envisioned primary functions of the ultracapacitor are to level the dynamic power loads on the primary propulsion device and recover available energy from regenerative breaking during off-peak power periods. This paper will present test data from selected U.S. Department of Energy (DOE) supported ultracapacitor projects designed to meet the fast response engine requirements.This paper will address the temperature dependence of test data obtained from a set of three devices provided from Maxwell Energy Products, Inc. These devices are rated at 2300 F at 2.3 V. Constant-current, constant-power, and self-discharge testing as a function of temperature have been conducted. From these tests were determined the capacitance, equivalent series resistance, specific energy and power, and the self-discharge energy loss factor as a function of the device operating temperature.
Computational, Electrochemical and 7Li NMR Studies of Lithiated Disordered Carbons Electrodes in Lithium Ion Cells
Authors: Sandί G. , Gerald R. E. , Scanlon L. G. , Carrado K. A. , Winans R. E. 
Published: April 2011

ABSTRACTDisordered carbons that deliver high reversible capacity in electrochemical cells have been synthesized by using inorganic clays as templates to control the pore size and the surface area. The capacities obtained were much higher than those calculated if the resultant carbon had a graphitic-like structure. Computational chemistry was used to investigate the nature of lithium bonding in a carbon lattice unlike graphite. The lithium intercalated fullenere Lin-C60 was used as a model for our (non-graphitic) disordered carbon lattice. A dilithium-C60 system with a charge and multiplicity of (0,1) and a trilithium-C60 system with a charge and multiplicity of (0,4) were investigated. The spatial distribution of lithium ions in an electrochemical cell containing this novel disordered carbon material was investigated in situ by Li-7 NMR using an electrochemical cell that was incorporated into a toroid cavity nuclear magnetic resonance (NMR) imager. The concentration of solvated Li+ ions in the carbon anode appears to be larger than in the bulk electrolyte, is substantially lower near the copper/carbon interface, and does not change with cell charging.
Effects of Sc or Tb Addition on the Microstructures and Resistivities of Al Thin Films
Authors: Takayama Shinji 
Published: April 2011

ABSTRACTThe resistivities of Al thin films with added Sc or Tb largely decrease at over 350 °C. They reach to 5 -7 μΩcm after annealing at 450 °C, together with the segregation of fine Al3RE (RE = Sc or Tb) metallic compounds. However, the temperatures at which resistivity starts to decrease largely are much lower for Al-SC alloy films (150 °C) than for Al-Tb ones (250 °C). Furthermore, thermal defects of hillocks or whiskers start to appear on the film surface after annealing at 200 °C and 450 °C for Al-Sc and Al-Tb alloy films, respectively. It was revealed that the further addition of Zr to these binary alloy films largely retards a large decrease of resistivities on annealing and enhances the formation of hillocks or whiskers. On the contrary, the addition of Cu to Al-Tb or Al-Sc films significantly suppresses the formation of thermal defects and shows relatively low resistivities after annealing at 350 °C.
Application of Broad-Band Dielectric Spectroscopy for Investigations of Liquid Crystal - Porous Media Microcomposites
Authors: Sinha G. P. , Batalla B. , Aliev F. M. 
Published: April 2011

ABSTRACTWe applied ultra broad-band dielectric spectroscopy in the frequency range from 10–3 Hz to 109 Hz to investigate the effect of size, shape and volume fraction of the pores in the porous matrices on the dielectric properties of liquid crystals (LC) dispersed in these matrices. Measurements in such a broad frequency range make it possible to obtain detailed information on the important aspects of the electrical behavior of heterogeneous materials such as: conductivity, surface polarization, and influence of confinement on dynamics of molecular motion of polar molecules forming LC. We investigated alkylcyanobiphenyls in the isotropie, nematic and smectic phases dispersed in porous glasses (average pore sizes - 100 Å and 1000 Å) which have randomly oriented, interconnected pores, and anopore membranes (pore diameters - 200 Å and 2000 Å) with parallel cylindrical pores. Dispersion of LC resulted in qualitative changes of their dielectric properties. Analysis of broad-band dielectric spectra shows that in organic (LC) - inorganic (porous matrix) heterogeneous composites conductivity plays an important role at F <1 Hz. We observe the appearance of new dielectric modes: a very slow process with characteristic frequency ≃ (1 – 10) Hz and a second process in frequency range about (103 - 106) Hz. The slow process arises due to the relaxation of interfacial polarization at pore wall - LC interface. The origin of this could be due to absorption of ions at the interface. Another possibility is the preferential orientation of the permanent dipoles at pore surface. The second new mode is due to the hindered rotation of the molecules near the interface. Additionally we observed two bulk like modes due to the rotation of the molecules around their short and long axii which are modified.
The Dielectric Loss of Single Crystal and Polycrystalline TiO2
Authors: Wang Xiaoru , Templeton Alan , Penn Stuart J. , Alford Neil McN. 
Published: April 2011

ABSTRACTThe dielectric loss of single crystal and polycrystalline TiO2 has been studied. In polycrystalline TiO2 the dielectric loss is determined by both the microstructure and by the oxygen stoichiometry. Experiments have been carried out to determine the influence of both the microstructure (particularly porosity) and the oxygen stoichiometry. The TiO2 powder has been doped with partially stabilised zirconia, an oxygen ion conductor, in order to modify the oxygen stoichiometry. Sintered discs have been examined for loss as a function zirconia doping, pore volume and as a function of temperature. The behaviour of the doped and undoped titania powders is significantly different. Since many microwave dielectric materials contain Ti eg Ba-Ti-O, Ba-Nd-Ti-O, (Ba-RE-Ti-O, RE=Rare Earth), Zr-Sn-Ti-O etc it is essential to understand the role of the titanium, particularly as it can exist in mixed valence states, and the role of oxygen and its influence on the dielectric loss.
High Power Switching Behavior in Conductor-Filled Polymer Composites
Authors: Duggal Anil R. , Levinson Lionel M. 
Published: April 2011

ABSTRACTIt has generally been assumed that the switching properties of conductor-filled polymer composites are based on a positive temperature coefficient of resistance (PTCR) effect where, at a certain switch temperature, the material resistivity increases by orders of magnitude. Here we present studies of the electrical switching behavior at high current densities which demonstrate that, in the high power regime, the observed switching is not based on the PTCR effect. Instead, we show that this type of switching appears to be a general feature in conductor-filled polymer composite materials and a qualitative model for the switching phenomenon is proposed. These results suggest that conductor-filled polymer composite materials can provide a new non-mechanical way of rapidly limiting high power short circuit currents. This should have broad applications in the circuit protection industry.
Microstructural Correlation with Electrical Properties for Y2O3 Doped CeO2 Thin Films
Authors: Tian Chunyan , Chan Siu-Wai 
Published: April 2011

ABSTRACTHigh quality textured 0.58% Y2O3 doped CeO2 films with (001), (111)/(001) and (110) were prepared using an e-beam deposition technique on substrates of (001) LaAlO3, r-cut sapphire, and fused silica, respectively. The composition and stoichiometry of the films were verified by Rutherford backscattering spectroscopy analysis. Both x-ray diffraction and transmission electron microscopy analyses gave consistent microstructural information. Complex impedance measurements have been performed to study the electrical properties of these films as a function of temperature. The conductivities of the films were dominated by grain boundaries of high conductivities as compared to that of the bulk ceramic of the same dopant concentration. The activation energies for the film conductivities were only slightly higher than that for the bulk lattice conductivities, but much lower than that for the bulk grain boundary conductivity. These results have been discussed in terms of the differences of the grain size and grain boundary microstructures between the films and the bulk ceramics.
Correlation Between Electrical Properties and Composition / Microstructure of Si-C-N Ceramics
Authors: Haluschka C. , Engel C. , Riedel R. , Kleebe H.-J. , Franke R. 
Published: April 2011

ABSTRACTIn this paper we report on the measurement of electrical properties of multielement ceramics in the ternary Si-C-N system using the impedance spectroscopy. The results were correlated to the chemical composition, the hybridization state and the microstructural characteristics investigated by chemical analysis, X-Ray absorption near edge spectroscopy (XANES), Raman Spectroscopy, high resolution transmission electron microscopy (HRTEM) and X-Ray powder diffraction (XRD).
Low-Frequency Scanning Capacitance Microscopy
Authors: Lányi Š. , Hruškovic M. 
Published: April 2011

ABSTRACTThe operation principle and main properties of a Scanning Capacitance Microscope (SCM) are described. It is called low-frequency, because in its design typical low-frequency techniques are utilised. The main attention is focused on its lateral resolution, signal-to-noise ratio and the possibility to detect dielectric losses.Mapping the electrostatic field of a shielded microscope probe was used to calculate the stray capacitance, flux density, sensitivity and contrast obtained on a flat conducting surface, as well as on a surface covered by a thin dielectric film. The effect of dielectric losses, represented by a parallel conductance, on the detected capacitance and the resulting phase shift has been derived.Using the results of mapping, the requirements on a SCM input stage and the possible solutions are discussed. From the point of view of frequency range and noise the best is an electrometric input stage, with input impedance represented by its capacitance.The achieved signal-to-noise ratio of the low frequency Scanning Capacitance Microscope renders the extension of the working frequency range to lower frequencies. The input stage can be optimised for a frequency range from about 1 kHz to a few MHz, with the possibility to extend it to about 10 MHz at the cost of reduced sensitivity at the lowest frequencies.
Comparison of Techniques for Microwave Characterization of Percolating Dielectric -Metallic Media and Resolution of Discrepancies in Measured Data
Authors: Moore Rick , Lust Lisa , Hopkins Edward , Friederich Paul 
Published: April 2011

ABSTRACTThe measured microwave effective dielectric properties of metal-dielectric composites show discrepancies when data from free space, resonant cavity or transmission line measurements are compared. Discrepancies are especially evident for materials where the metallic concentration is near the percolation threshold. This paper presents theory and measured data which highlight and resolve these discrepancies. Electrical correlation length is the relevant parameter which must be considered in choice of measurement technique. Agreement between effective medium models and measurement are best when focussed beam measurement techniques are utilized so as to produce planar wave-fronts whose extent is 3–4 freespace wavelengths when incident on the sample.
Computer Simulation of Impedance for 2-D Conductor-Insulator Composite
Authors: Han Dae Gon , Choi Gyeong Man 
Published: April 2011

ABSTRACTUsing a computer simulation, impedance spectra of mixtures of conducting and insulating hard spheres which have random or regular arrangements of the components are studied. These simulations can be used to calculate the a.c. electrical properties of a multi-component composite using a personal computer. It is shown in this study that a.c. impedance spectra are sensitive functions of the filling fraction and the geometrical arrangement of the components, and especially, the impedance spectra of the composite show the abnormal arc originated from the isolated clusters in the composite.
Investigation of the Dopant Distribution in thin Epitaxial Silicon Layers by Means of Spreading Resistance Probe and Secondary Ion Mass Spectrometry
Authors: Karpov Ilya , Hartford Catherine , Moran Greg , Krishnakumar Subramania , Choma Ron , Linn Jack 
Published: April 2011

ABSTRACTIn this paper, we examine the dopant distributions in 1.8 to 4 micron-thick boron- and phosphorus-doped epitaxial silicon layers. These layers were grown by chemical vapor deposition (CVD) on arsenic-, antimony-, or boron-doped (100)- and (111)-oriented substrates. We performed doping profile studies by means of local resistivity measurements using a spreading resistance probe (SRP). Chemical profiles of the dopants were also obtained using secondary ion mass spectrometry (SIMS).