02593 Capacity loss in Ni-Cd pocket plate batteries. The origin of the second voltage plateau

06 Necfrical power supply and utilization (scientific, technical)

00102583 A review of state-of-charge indication of batteries by means of a.c. impedance measurements Rodrigues, S. Journal of Power Sources, 2000, 87, (I-2), 12-20. A non-destructive estimation of the state-of-charge (SoC) of batteries facilitates optimum utilization of the battery for a given application, as well as evaluation of its state-of-health. Among various methods, a.c. impedance spectroscopy over a wide range of frequencies provides a variety of parameters which are functions of the SoC of a given battery. These parameters and their variation with SoC depend on the type of battery and on the experimental conditions. The impedance data of sealed commercial cells are rather tedious to analyse since the results are generally the combined parameters of both the positive and the negative electrodes. Separation of the parameters which correspond to the individual electrodes involves assumptions, the validity of which is open to question. Nevertheless, systematic linear and reproducible variations of measurable or computable impedance parameters with battery condition are useful indicators of the SoC in a non-destructive way. The present review consolidates the literature on the prediction of the SoC of batteries by means of a.c. impedance measurements.

00102584 A semi theoretical approach of the second plateau a pearing during the discharge of aged nickel oxyhydroxide e Pectrodes Mancier, V. Journd o/Power Sources. 2000, 85, (2), 181-185. A semi theoretical explanation of the appearance of a second plateau during the discharge of overcharged nickel oxyhydroxide electrodes (NOHE) is proposed, based on transmission line models of the chargedischarge processes of the active matter. The model takes into account the double electronic and protonic conduction involved in nickel II a and 4 or nickel III B and 1 phases: electrons and protons reach the transformation front inside, the matter through the less resistive paths. The secondary plateau may occur when a resistive layer of fi (II) isolates the transformation front from the nickel electron sink. A Tabu search algorithm for maintenance scheduling 00102585 of generating units El-Amin, I. Elec. Power Sysr. RES., 2000, 54, (2), 91-99. A new heuristic algorithm based on the Tabu search has been proposed for the maintenance schedule (MS) of electric generation units. The algorithm was developed, implemented and tested on an integrated model for the MS problem. The model used two criteria: minimizing the total generator operating cost and levering the reserve. Each of the above criteria is used with the following constraints: maintenance completion, crew size, precedence, reserve and reserve constants. The performance of the Tabu search algorithm is promising. The Tabu search algorithm solved two power system problems, four units and 22 units. The implicit enumeration algorithm was used to check the validity and the quality of the Tabu search solution. 00/02586 Accelerating rate calorimetry study on the thermal stability of lithium intercalated graphite in electrolyte. I. Experimental Richard, M. N. and Dahn, J. R. J. Electrochemical Sm., 1999, 146, (6), 2068-2077. The thermal stability of a lithiated mesocarbon microbead (MCMB) material was measured by an accelerating rate calorimeter (ARC) in an electrolyte under adiabatic conditions. Measurements were carried out to determine the effects of the lithium content and surface area of the electrode as well as the effects of the electrolyte type and the initial heating temperature on thermal stability. MCMB electrodes with both high and low surface area were reacted electrochemically to three compositions: Lio.& (0.0 V), Lia&, (0.89 V), and Lia& (0.127 V) in LiPF6 ethylene carbonate/diethyl carbonate (EC:DEC) (33:67) electrolyte. The lowsurface-area MCMB samples were also lithiated in LiPFr, EC:DEC (5050) and LiBF4 EC:DEC (5O:SO) electrolytes. The results showed that self-heating of the MCMB samples depends on (i) the initial lithium content of the material, (ii) the electrolyte used, (iii) the surface area, and (iv) the initial heating temperature of the sample. Measurable self-heating in the LiPF6 EC:DEC (33:67) samples was detected at 80”, at 70” for MCMB in LiPF6 EC:DEC (l:l), and at 50” for MCMB in LiBFl EC:DEC (1:l). The initial self-heating rate for samples containing LiPFa EC:DEC (33:67) electrolyte could be fit by an Arrhenius relation with an activation energy of 1.4 eV. The conversion of metastable solid electrolyte interface accounted for the initial form of the self-heating rate profile.

Accelerating rate calorimetry study on the thermal 00/02587 stability of lithium intercalated graphite in electrolyte. II. Modeling the results and predicting differential scanning calorimeter curves Richard, M. N. and Dahn, J. R. J. Elecrrochemical Sot., 1999, 146, (6), 2078-2084. In this paper a mathematical model, based on the previously proposed mechanism, is developed in order to calculate self-heating rate profiles. The calculated self-heaiing rate profiles reproduce qualitatively the experimental measured trends. The mathematical model for the self-heating of this anode material in electrolytes can be used to calculate differential scanning calorimeter (DSC) profiles. Using adjustable parameters, determined and

fixed by comparisons to ARC experiments, the calculated DSC profiles approximate the measured DSC profiles, suggesting that the model has correctly represented the reaction kinetics. 00102588 An investigation on layered birnessite type manganese oxides for battery applications Renuka, R. Ramamurthy, S. Journal of Power Sources, 2000, 87, (I-2). 144-152. Layered birnessite-type manganese oxide was prepared by a simple redox sol-gel reaction involving hydroxylamine and permanganate in alkaline medium. IR, XRD, Auger electron spectroscopy, EPR, TGA and cyclic voltammetric characteristics of the birnessites are presented. The hirnessite was examined for its cathode performance in zinc-, magnesiumand lithium-based cells. Bismuth and lead exchange birnessite show superior battery performance when compared with sodium and potassium precursors. The magnetoresistance pattern of the discharged birnessite (in Mg/ Mg(Cl04)z) indicates a colossal magnetoresistance. This observation provides a scope for further studies of examming the applicability of magnetoresistance measurement in assessing the charge/discharge status of manganese oxides. Heat treatment of birnessite brings about distinct changes in the EPR and IR pattern. A correlation between the spectral features and electrochemical activity can be understood. 00/02589 An ultrasafe hydrogen generator: aqueous, alkaline borohydride solutions and Ru catalyst Amendola, S. C. Journal of Power Sources, 2000. 85, (2), l8&189. A novel, simple, convenient and safe chemical process generates high purity hydrogen gas on demand from stable, aqueous solutions of sodium borohydride, NaBH4 and ruthenium-based, catalyst. When NaBH.,, solution contacts the ruthenium catalyst, it spontaneously hydrolyses to form Hz gas and sodium borate, a water-soluble, inert salt. When Hz is no longer required, ruthenium catalyst is removed from the solution and Hz generation stops. Since this Hz generator is safer. has quicker response to Hz demand and is more efficient than commonly used Hz generators, it is ideal for portable applications. 00/02590 Analytical method of finite time thermodynamics about the physical and chemical performances of fuel cell Yuan, D. Huaxue Wuli Xuehao, 1999, 12. (I). 63-67. (In Chinese) The physical performances and the chemical performances of the fuel cell are studied (provided that the irreversibility of chemical reaction and thermal resistance are considered), using the method to combine electrochemical and non-equilibrium thermodynamics with finite time thermodynamics. Some new formulae of the performances limit and the formula of measuring electrochemical reaction rate are given. 00102591 Applications of damping torque analysis_to STATCOM control Wang, H. F. Electrical Power and Energy Sysrerm, 2000, 22, (3). 197-204. By applying the conventional technique of damping torque analysis, this paper investigates the effect of STATCOM AC and DC voltage regulator on power system oscillation damping and demonstrates the design of STATCOM damping controller by using the phase compensation method. The investigation reveals the negative influence of STATCOM AC and DC voltage regulator on power system oscillation damping which is confirmed by the results of eigenvalue computation and non-linear simulation of an example power system. The effectiveness of STATCOM damping controller designed by the phase compensation method to damp power system oscillations is also illustrated by the example power system. 00/02592 Calculation of ampacities for cables in trays using finite elements Hwang, C. C. Elec. Power Sysr. Res., 2000, 54, (2), 75-81. This paper describes a finite element method for calculating the ampacities of cables in a tray. The governing equation is solved using Galerkin’s procedure and the Newton-Raphson iterations is employed to solve nonlinear finite element equations as a result of the inclusion of radiation boundary conditions. The use of an equivalent thermal conductivity of cable mass in a tray is proposed. To determine the cable derating factor, both open-top and covered cable tray are employed in the analysed model. It can be seen that the cable derating factor is independent of the type cables filled in the tray. The numerical results of this method are good and comparison with other available values. 00/02593 Capacity loss in Ni-Cd pocket plate batteries. The origin of the second voltage plateau Ahlberg, E. Journal of Power Sources, 2000, 85, (2). 245.-253. Electrical testing of batteries, voltammetry and surfaces analysis by X-ray diffraction (XRD) and Fourier transformation infrared (FTIR) were used to investigate the origin of the second voltage plateau. The electrical testing results show that there is a direct coupling between graphite loss and the appearance of the second voltage plateau. The graphite loss was shown to increase for float charging at elevated temperatures and high potentials. The effect of graphite particle size distribution was also investigated. Voltammetry of discharged material, Ni(OH)z and charged material, 3NiOOH and r-NiOOH, in carbon paste showed that the second voltage plateau did not originate from the redox properties of the material, or the presence of carbonate in the material or in the electrolyte. Therefore, the

Fuel and Energy Abstracts

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06 Electrical power supply and utilization (scientific, technical)

second voltage plateau is believed to appear whenever an increased internal resistance arises, may it be due to graphite loss, swelling or some other factor. 00102594 Characteristics of vanadium based composite cathode for lithium secondary battery Kim, J. J. cl al. J. Korean Necrrochemical Sot., 1999, 2, (2) 62-65. (In Korean) This paper proposes a new treatment of LiVsOs for improving its electrochemical behaviour as a cathode material for secondary lithium batteries. LiVsOs can be prepared in a finely dispersed form by dehydration of aqueous lithium trivanadate gels. The ultrasonic treatment method for LiVsOs has been examined, in comparison with LiVsOs prepared by solution method. The ultrasonically treated products in water were characterized by X-ray diffractometry, TGA, and SEM. These measurements showed that the ultrasonic treatment process of aqueous LiVsOs caused a decrease in crystallinity and considerable increase in specific surface area and interlayer spacing. The product, ultrasonically treated in water for 2 h, showed a high initial discharge capacity and was chargedischarge cycled without large capacity loss. The ultrasonically treated LiVsOs can improve both the cycling behaviour and the specific capacity. 00/02595 Characterization of commercial Li-ion batteries using electrochemical-calorimetric measurements Al Hallaj, S. Journal q/Po~er Sources, 2000, 87, (l-2), 186194. Commercial Li-ion cells of Yype 18650 dimensions and prismatic designs from different manufacturers have been tested to evaluate their performance and to study their thermal behaviour using electrochemical-calorimetric methods. All cells tested in this work showed good performance and cyclability under normal operating conditions. The measured heat effect for the cells were exothermic during discharge and partially endothermic during charge. Cell impedance was measured for selected cells and showed some dependence on the state of charge or depth of discharge, with significant increase at the end of discharge due to concentration polarization. The entropy coefficient (dE,,/dT) for the A & T (18650) and Panasonic (CGR 18650) cells were measured using potentiometric methods at different depths of discharge (DOD). The measured values for both cells showed some dependence on the DOD with some perturbation near 4.0 V, where the measured dE,,/dT for Panasonic cell had an unexpected positive value. This was found to be consistent with the measured endothermic heat effect during discharge for the Panasonic cell near Ecq = 4.0 V. This may be related to a phase change in the LiCoOz cathode material, as reported in the literature and to structural transformation in the graphite used as anode material, in the Panasonic cell. 00/02596 Cleaner production options for lead-acid battery manufacturing industry Dahodwalla, H. and Herat, S. Journal of Clemer Producrion, 2000, 8, (2), 133-142. Various demonstration projects conducted around the world have indicated that the cleaner production approach is more beneficial than the end-ofpipe type solutions. This study demonstrates how cleaner production can be applied to the lead-acid battery manufacturing industry, with focus on reduction/prevention of lead wastes. Various cleaner production options are discussed in relation to their technical and environmental feasibility. The effectiveness of good housekeeping practices, changing manufacturing processes, better process control and on-site recycling of waste generated are discussed. On-site recycling of scrap plates was found to provide 49% reduction in the quantity of lead waste generated demonstrating that cleaner production does not necessarily need extensive changes in present practices. 00102597 Concrete decontamination and other D&D applications of electric pulse power technology Goldfarb, V. er al. Proc. ht. Conf. Decomm. Decontum. Nucl. Huzrrrd. Was/e Munuge, 1998, I, 140-147. Some developed and potential applications of pulsed electric discharges for treatment of nuclear and chemical contaminants in structures and materials are considered. This includes work conducted at Textron Systems, especially on the removal of surface layers of concrete contaminated by uranium using electric pulse (EP) breakdown through the concrete layer or electro-hydraulic (EH) through the Hz0 layer. Development and fieldtesting of a prototype unit are described. Expansion of this technology to other concrete-related decontamination issues are proposed. Experimental work at Textron related to waste prevention, treatment and immobilization includes also: the removal of organic contaminants from HzO, the preparation of coal/Hz0 slurries for clean coal combustion, the pulsed discharge application fuel injection for reduction of NO, in a gas turbine exhaust, the neutralization of the most dangerous wastes (land- and seabased mines). The authors also briefly discuss other applications of the far field (shock waves, UV radiation) and near field (direct plasma contact, cavitation) effects produced by electric pulses for D and D (deactivation, decontamination and decommissioning). OOlO2598 Correlation between the structure and electrochemical properties of carbon materials Qiu, W. er rrl. Solid Sfare Ionics, 1999, 121, (l-4), 73-77.

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A coke/graphite composite with a core-shell structure has been manufactured in this work. The disordered coke shell will protect the graphite core from exfoliation and improve the diffusion rate of lithium ions into the composite particles. In comparison with naked graphite anodes, this core/ shell composite carbon anode for lithium-ion batteries shows high capacity, excellent kinetics and good compatibility with electrolyte solutions. 00/02599 Crystal structure of positive material Ni(OH)* in Ni-MH battery Li, R. and Fu, J. Gongneng Cailim, 1998, 29, (Suppl.), 75c-751. (In Chinese) XRD and thermal analysis was used to study the effect of crystal type and structure of different Ni(OH)a on the electrochemical characteristics of positive electrodes. The positive material with excellent electrochemical characteristics could be correlated to &Ni(OH)z and smaller crystal size. In particular, it could be correlated to a lower crystallinity in carbon-direction and an unstable crystal structure. 00102600 Determination of reaction resistances for metalhydride electrodes during anodic polarization Wang, C. Journal of Power Sources, 2000, 85, (2). 212-223. Tile anodic polarization process in metal-hydride electrodes occurs via the following consecutive steps: (i) diffusion of absorbed hydrogen from the bulk to the surface of the electrode, (ii) hydrogen transfer from absorbed state to adsorbed state at the electrode surface and (iii) electrochemical oxidation of the adsorbed hydrogen on the electrode surface. A theoretical treatment is presented to account for the dependencies on these three consecutive steps, of the reaction resistances, anodic limiting current, cathodic limiting current and exchange current. The theoretical analysis predicts that the total resistances measured from linear micropolarization is the sum of the charge-transfer, hydrogen-transfer and hydrogen-diffusion resistances, which is in contradiction with the generally accepted idea that the resistance measured from linear micropolarization is only the chargetransfer resistance. For a metal-hydride electrode with a flat pressure plateau at a low state of discharge (SOD), the resistance measured from linear micropolarization is approximately equal to the sum of three resistances measured from AC impedance, namely, charge-transfer, hydrogen-transfer and hydrogen-diffusion resistances; however, when the SOD is high, the resistance measured from linear micropolarization is higher than total resistances measured from AC impedance. 00102601 Digital implementation of an advanced static compensator for voltage profile improvement, power-factor correction and balancing of unbalanced reactive loads Singh, B. N. Elm. Power Sysr. RES., 2000, 54, (2). 101-l Il. In this paper, a three-phase advanced static compensator (STATCOM) is proposed to compensate reactive power either for regulating ac supply voltage at a constant value or for unity power-factor and balancing of unbalanced reactive loads. An insulated gate bipolar transistor (IGBT) based current controlled pulse width modulated (CC-PWM) and voltage source inverter (VSI) is employed as the STATCOM. A TMS320C31 DSP is used to implement the control algorithm of the STATCOM. To regulate the instantaneous ac supply voltage across the load through shunt reactive power compensation, a sliding mode controller SMC over the amplitude of supply voltage is used to obtain a reactive component of the reference supply current in quadrature with the supply voltage. Another SMC over the voltage of a self-supporting dc bus of the STATCOM is used to compute an active component of reference supply current in-phase with the supply voltage. An indirect PWM current control over the reference (computed) and sensed supply current is employed to generate the gating pulses of the IGBTs of the STATCOM. Test results are presented and discussed in detail to demonstrate the reactive power compensation for terminal voltage regulation and power-factor correction along with load balancing capabilities of the proposed advanced STATCOM. 00102602 Dynamic output compensation between selected channels in power systems. Part 1. The framework Lefebvre, S. EIecrrical Power utzd Energy Syslems, 2000, 22, (3), 155-163. This paper presents a dynamic compensation framework for the design of a set of low order dynamic MIS0 controllers between selected input and output channels at each control site, or control agent, in power systems, The first step is to pick the best set of available measurements to feed in individual controllers at each control agent. The choice of measurements is made in conjunction with the control objectives in multiple time scales focusing on selected system modes. The measurements serve as controller inputs and are used for characterizing the system with low order models whose transfer matrices are good approximations of the full system. This step involves Hankel singular values analysis and balanced system representations. The second step is to design the controls. Two approaches are described. The idea of one method is to mimic the relevant dynamics of linear state feedback with a controller that takes into account structural constraints by separately designing each control input based on the best measurements available at each agent. Instead of retaining modes and mode shapes, as with projective control, this design method approximates the controller optimizing a time-domain performance index. While not as systematic as Hx? design or as optimization techniques, the approach yields practical designs, superior to state feedback and projective control in terms of robustness. Furthermore, iterative p-synthesis can be used as an alternate design if robustness is not sufticient. In Part 2 of the paper, examples are