- Email: [email protected]
03182 A discussion and analysis of the voltage stability problems in Oman
06
Electrical power supply and utilization (scientific, technical)
avoids the problem of lithium dendrite formation and provides a big improvement in terms of cycleability and safety. This paper reviews the main achievements on the performance and understanding of chargedischarge mechanisms, resulting from the tremendous activity devoted to these systems in the past few years. The paper successively examines the electrochemical behaviour of the main families of materials, namely, natural and synthetic graphites, graphitizable carbons, low-temperature and non-graphitizing carbons and doped carbons.
Carbonaceous anode materials for secondary 99163176 lithium batteries Suzuki, K. and Sugiura, T. Jpn. Kokai Tokkyo Koho JP 10 326,611 [98 326,611] (Cl. HOlM4/02), 8 Dee 1998, JP Appl. 97/77,930, 28 Mar 1997, 9 pp. (In Japanese) Graphitized carbonaceous materials, obtained by oxidizing petroleum or coal derived coke under heating and graphitizing the oxidized substance, comprise the anode materials.
Characterization of microporous separators for 99i63177 lithium-ion batteries Venugopal, G. 1. Power Sources, 1999, 77, (l), 34-41. Several properties including porosity, pore-size distribution, thickness value, electrochemical stability and mechanical properties have to be optimized before a membrane can qualify as a separator for a lithium-ion battery. In this paper, results of characterization studies carried out on some commercially available lithium-ion battery separators are presented. The relevance of these results to battery performance and safety are also discussed. Porosity values were measured using a simple liquid absorption test and gas permeabilities were measured using a novel pressure drop technique that is similar in principle to the Gurley test. For separators from one particular manufacturer, the trend observed in the pressure drop times was found to be in agreement with the Gurley numbers reported by the separator manufacturer. Shutdown characteristics of the separators were studied by measuring the impedance of batteries containing the separators as a function of temperature. Overcharge tests were also performed to confirm that separator shutdown is indeed a useful mechanism for preventing thermal runaway situations. Polyethylene containing separators, in particular trilayer laminates of polypropylene, polyethylene and polypropylene, appear to have the most attractive properties for preventing thermal runaway in lithium ion cells.
Chitosan-lithium triflate electrolyte in secondary 99103176 lithium cells Morni, N. M. and Arof, A. K. J. Power Sources, 1999, 77, (l), 42-48. Films prepared from high molecular weight chitosan are shown to exhibit the highest electrical conductivity of 2.14 x lo-’ S cm~‘. The electrical conductivity is further enhanced to 1.03 x 10.’ S cm-’ when ethylene carbonate (EC) is used as a plasticizer. X-ray diffraction (XRD) shows that EC disrupts the crystalline nature of chitosan acetate. Infrared (IR) spectroscopy reveals a shift in the amide band from 1590 to 1575 cm- on addition of LiCF$03. A film with a (chitosan + 0.4 g EC) to LiCFsSO3 ratio of 80:20 gives the highest electrical conductivity of 3.0 x 10m4 S cm~‘. This film is used as an electrolyte for the fabrication of chitosan-based secondary cells such as, lithiumlchitosan-EC-LiCF3SOS/VZOS. The characteristics of the cells are presented in this paper.
Composition and performance modelling of 99103179 catalyst layer in a proton exchange membrane fuel cell Marr, C. and Li, X. J. Power Sources, 1999, 77, (l), 17-27. The composition and performance optimization of cathode catalyst platinum and catalyst layer structure in a proton exchange membrane fuel cell has been investigated by including both electrochemical reaction and mass transport process. It is found that electrochemical reactions occur in a thin layer within a few micrometers thick, indicating ineffective catalyst utilization for the present catalyst layer design. The effective use of platinum catalyst decreases with increasing current density, hence lower loadings of platinum are feasible for higher current densities of practical interest without adverse effect on cell performance. The optimal void fraction for the catalyst layer is about 60% and fairly independent of current density and a 40% supported platinum catalyst yields the best performance amongst various supported catalysts investigated. An optimal amount of membrane content in the void region of the catalyst layer exists for minimum cathode voltage losses due to competition between proton migration through the membrane and oxygen transfer in the void region. The present results will be useful for practical fuel cell designs.
The curing reaction study of the active material in 99103160 the lead-acid battery Laruelle, S. et al. J. Power Sources, 1999, 77, (l), 83-89. A study of the curing reaction involved in the positive plate of the lead-acid battery has been undertaken. The variation of the different parameters of the curing reaction has shown the possibility of changing the 4BS needles dimensions. In particular, the addition of a surfactant agent, namely the polyvinylpyrrolidone, to the reagents allows the obtention of tailor-made 4BS particles useable in the industrial preparation of the positive plates.
334
Fuel and Energy Abstracts
September
1999
99103161 Current collectors for a novel tubular design of solid oxide fuel cell Hatchwell, C. el al. J. Power Sources, 1999, 77, (l), 64-68. Current collection/interconnection of novel tubular solid oxide fuel cells (SOFCs) is achieved by means of alloy metal interconnects based on Ducrolloy (Cr.5FelYz03) coated with various electronically conductive coatings. Coatings applied to the metal interconnect improve cell performance. For example, at 900°C in air, a Ag-LaosSro ,Cr09 (AgLSC) coated interconnect is used in conjunction with an 8 mol% yttria stabilized zirconia (YSZ) tubular electrolyte based SOFC. At 0.7 V a cell performance of 40 mA/cm’ is achieved for the coated sample, compared with a lower performance of 16 mA/cm* attained with an uncoated interconnect. The thermal shock resistant properties of the tubes are not compromised by use of the metal interconnect. 99103162 A discussion and analysis of the voltage stability problems in Oman Khan, A. Z. Electric Power Systems Research, 1999, 49, (l), 31-36. The problems encountered in system voltages for a fast growing utility, i.e. the Ministry of Electricity and Water of the Sultanate of Oman in the Arabian Gulf, are discussed in this paper. In the summer, the utility has mostly air-conditioning load and the system encountered voltage stability problems during peak summer conditions. Detailed discussions are given on recommendations proposed to remedy the voltage problems. The most critical period for voltage problems during summer days and its effect on remote load buses in terms of voltage profile is discussed. System wide weak voltage buses have been identified. 99103163 Effects of different methods of cobalt addition on the performance of nickel electrodes Chang, Z. et al. J. Power Sources, 1999, 77, (l), 69-73. Cobalt is an effective additive which is widely used in nickel electrodes. Three kinds of nickel electrodes with various cobalt levels are made with different methods of cobalt addition. The electrochemical properties including charge-discharge characteristics of the nickel electrodes are investigated. It is found that the method used to add cobalt exerts a marked effect on electrode performance. Nickel electrodes with cobalt incorporated directly display excellent charge-discharge behaviour. By contrast, nickel electrodes co-precipitated with cobalt exhibit an adverse effect except at high-rate discharge. Effects of power system parameters on critical 99103164 clearing time: comprehensive analysis Khan, A. Z. Electric Power Systems Research, 1999, 49, (l), 37-44. Presented here are the effects of various power system parameters on the critical clearing time. The various parameters for which the analysis is presented include the machine parameters and system parameters. Various configurations of faults are also investigated. The simplest single machine infinite bus power system was simulated. Plots and relationships for each parameter are presented and conclusions are drawn from their behaviour. The paper is a comprehensive treatment of the time domain method to the single machine system and is particularly helpful to the utility power engineers and researchers in the electric machines area to comprehend the system behaviour for various system parameters. In addition, the results can be generalized to the large scale multi-machine power systems. 99103165 Electric double-layer capacitor using composites corn osed of hosphoric acid-doped silica gel and styreneethy Pene-buty Pene-styrene elastomer as a solid electrolyte Matsuda, A. et al. J. Power Sources, 1999, 77, (l), 12-16. Solid state electric double-layer capacitors have been fabricated using a composite composed of RsP04-doped silica gel and styrene-ethylenebutylene-styrene elastomer as the electrolyte. A composite hybridized with activated carbon powders (ACP) was the polarizable electrode. The cyclic voltammogram of the electric double-layer capacitor fabricated demonstrated that electric charge was stored in the electric double-layer at the interface between the polarizable electrode and the electrolyte. Resistance of the capacitor obtained from impedance plots in ambient air was smaller by three orders of magnitude than that of the capacitor in a dry argon atmosphere. The drastic decrease in the resistance should be ascribed to the increase in the proton conductivity of the composite due to the water adsorption in R3POd-doped silica gel in an ambient atmosphere. The value of capacitance of the capacitor in an ambient atmosphere was 10 F/(gram of total ACP), which was 10 times larger than that of the capacitor in a dry argon atmosphere. The large capacitance of the capacitor in an ambient atmosphere is attributable to the formation of electric double-layer with large electric charge at the interface between the composite and ACP in the capacitor due to the water adsorption. 99103166 Electrochemical behavior of nickel deposited on reticulated vitreous carbon Czerwinski, A. et al. 1. Power Sources, 1999, 77, (l), 28-33 The electrochemical performance of nickel deposited on reticulated vitreous carbon (RVC) has been investigated in solutions of KOH. For comparison, the study of sintered nickel and nickel deposited on gold wire behaviour were also included. Our results indicate that the RVC covered with nickel is a good carrier for Ni(OH)z/NiOOH, an electrode material,
Electrical power supply and utilization (scientific, technical)
avoids the problem of lithium dendrite formation and provides a big improvement in terms of cycleability and safety. This paper reviews the main achievements on the performance and understanding of chargedischarge mechanisms, resulting from the tremendous activity devoted to these systems in the past few years. The paper successively examines the electrochemical behaviour of the main families of materials, namely, natural and synthetic graphites, graphitizable carbons, low-temperature and non-graphitizing carbons and doped carbons.
Carbonaceous anode materials for secondary 99163176 lithium batteries Suzuki, K. and Sugiura, T. Jpn. Kokai Tokkyo Koho JP 10 326,611 [98 326,611] (Cl. HOlM4/02), 8 Dee 1998, JP Appl. 97/77,930, 28 Mar 1997, 9 pp. (In Japanese) Graphitized carbonaceous materials, obtained by oxidizing petroleum or coal derived coke under heating and graphitizing the oxidized substance, comprise the anode materials.
Characterization of microporous separators for 99i63177 lithium-ion batteries Venugopal, G. 1. Power Sources, 1999, 77, (l), 34-41. Several properties including porosity, pore-size distribution, thickness value, electrochemical stability and mechanical properties have to be optimized before a membrane can qualify as a separator for a lithium-ion battery. In this paper, results of characterization studies carried out on some commercially available lithium-ion battery separators are presented. The relevance of these results to battery performance and safety are also discussed. Porosity values were measured using a simple liquid absorption test and gas permeabilities were measured using a novel pressure drop technique that is similar in principle to the Gurley test. For separators from one particular manufacturer, the trend observed in the pressure drop times was found to be in agreement with the Gurley numbers reported by the separator manufacturer. Shutdown characteristics of the separators were studied by measuring the impedance of batteries containing the separators as a function of temperature. Overcharge tests were also performed to confirm that separator shutdown is indeed a useful mechanism for preventing thermal runaway situations. Polyethylene containing separators, in particular trilayer laminates of polypropylene, polyethylene and polypropylene, appear to have the most attractive properties for preventing thermal runaway in lithium ion cells.
Chitosan-lithium triflate electrolyte in secondary 99103176 lithium cells Morni, N. M. and Arof, A. K. J. Power Sources, 1999, 77, (l), 42-48. Films prepared from high molecular weight chitosan are shown to exhibit the highest electrical conductivity of 2.14 x lo-’ S cm~‘. The electrical conductivity is further enhanced to 1.03 x 10.’ S cm-’ when ethylene carbonate (EC) is used as a plasticizer. X-ray diffraction (XRD) shows that EC disrupts the crystalline nature of chitosan acetate. Infrared (IR) spectroscopy reveals a shift in the amide band from 1590 to 1575 cm- on addition of LiCF$03. A film with a (chitosan + 0.4 g EC) to LiCFsSO3 ratio of 80:20 gives the highest electrical conductivity of 3.0 x 10m4 S cm~‘. This film is used as an electrolyte for the fabrication of chitosan-based secondary cells such as, lithiumlchitosan-EC-LiCF3SOS/VZOS. The characteristics of the cells are presented in this paper.
Composition and performance modelling of 99103179 catalyst layer in a proton exchange membrane fuel cell Marr, C. and Li, X. J. Power Sources, 1999, 77, (l), 17-27. The composition and performance optimization of cathode catalyst platinum and catalyst layer structure in a proton exchange membrane fuel cell has been investigated by including both electrochemical reaction and mass transport process. It is found that electrochemical reactions occur in a thin layer within a few micrometers thick, indicating ineffective catalyst utilization for the present catalyst layer design. The effective use of platinum catalyst decreases with increasing current density, hence lower loadings of platinum are feasible for higher current densities of practical interest without adverse effect on cell performance. The optimal void fraction for the catalyst layer is about 60% and fairly independent of current density and a 40% supported platinum catalyst yields the best performance amongst various supported catalysts investigated. An optimal amount of membrane content in the void region of the catalyst layer exists for minimum cathode voltage losses due to competition between proton migration through the membrane and oxygen transfer in the void region. The present results will be useful for practical fuel cell designs.
The curing reaction study of the active material in 99103160 the lead-acid battery Laruelle, S. et al. J. Power Sources, 1999, 77, (l), 83-89. A study of the curing reaction involved in the positive plate of the lead-acid battery has been undertaken. The variation of the different parameters of the curing reaction has shown the possibility of changing the 4BS needles dimensions. In particular, the addition of a surfactant agent, namely the polyvinylpyrrolidone, to the reagents allows the obtention of tailor-made 4BS particles useable in the industrial preparation of the positive plates.
334
Fuel and Energy Abstracts
September
1999
99103161 Current collectors for a novel tubular design of solid oxide fuel cell Hatchwell, C. el al. J. Power Sources, 1999, 77, (l), 64-68. Current collection/interconnection of novel tubular solid oxide fuel cells (SOFCs) is achieved by means of alloy metal interconnects based on Ducrolloy (Cr.5FelYz03) coated with various electronically conductive coatings. Coatings applied to the metal interconnect improve cell performance. For example, at 900°C in air, a Ag-LaosSro ,Cr09 (AgLSC) coated interconnect is used in conjunction with an 8 mol% yttria stabilized zirconia (YSZ) tubular electrolyte based SOFC. At 0.7 V a cell performance of 40 mA/cm’ is achieved for the coated sample, compared with a lower performance of 16 mA/cm* attained with an uncoated interconnect. The thermal shock resistant properties of the tubes are not compromised by use of the metal interconnect. 99103162 A discussion and analysis of the voltage stability problems in Oman Khan, A. Z. Electric Power Systems Research, 1999, 49, (l), 31-36. The problems encountered in system voltages for a fast growing utility, i.e. the Ministry of Electricity and Water of the Sultanate of Oman in the Arabian Gulf, are discussed in this paper. In the summer, the utility has mostly air-conditioning load and the system encountered voltage stability problems during peak summer conditions. Detailed discussions are given on recommendations proposed to remedy the voltage problems. The most critical period for voltage problems during summer days and its effect on remote load buses in terms of voltage profile is discussed. System wide weak voltage buses have been identified. 99103163 Effects of different methods of cobalt addition on the performance of nickel electrodes Chang, Z. et al. J. Power Sources, 1999, 77, (l), 69-73. Cobalt is an effective additive which is widely used in nickel electrodes. Three kinds of nickel electrodes with various cobalt levels are made with different methods of cobalt addition. The electrochemical properties including charge-discharge characteristics of the nickel electrodes are investigated. It is found that the method used to add cobalt exerts a marked effect on electrode performance. Nickel electrodes with cobalt incorporated directly display excellent charge-discharge behaviour. By contrast, nickel electrodes co-precipitated with cobalt exhibit an adverse effect except at high-rate discharge. Effects of power system parameters on critical 99103164 clearing time: comprehensive analysis Khan, A. Z. Electric Power Systems Research, 1999, 49, (l), 37-44. Presented here are the effects of various power system parameters on the critical clearing time. The various parameters for which the analysis is presented include the machine parameters and system parameters. Various configurations of faults are also investigated. The simplest single machine infinite bus power system was simulated. Plots and relationships for each parameter are presented and conclusions are drawn from their behaviour. The paper is a comprehensive treatment of the time domain method to the single machine system and is particularly helpful to the utility power engineers and researchers in the electric machines area to comprehend the system behaviour for various system parameters. In addition, the results can be generalized to the large scale multi-machine power systems. 99103165 Electric double-layer capacitor using composites corn osed of hosphoric acid-doped silica gel and styreneethy Pene-buty Pene-styrene elastomer as a solid electrolyte Matsuda, A. et al. J. Power Sources, 1999, 77, (l), 12-16. Solid state electric double-layer capacitors have been fabricated using a composite composed of RsP04-doped silica gel and styrene-ethylenebutylene-styrene elastomer as the electrolyte. A composite hybridized with activated carbon powders (ACP) was the polarizable electrode. The cyclic voltammogram of the electric double-layer capacitor fabricated demonstrated that electric charge was stored in the electric double-layer at the interface between the polarizable electrode and the electrolyte. Resistance of the capacitor obtained from impedance plots in ambient air was smaller by three orders of magnitude than that of the capacitor in a dry argon atmosphere. The drastic decrease in the resistance should be ascribed to the increase in the proton conductivity of the composite due to the water adsorption in R3POd-doped silica gel in an ambient atmosphere. The value of capacitance of the capacitor in an ambient atmosphere was 10 F/(gram of total ACP), which was 10 times larger than that of the capacitor in a dry argon atmosphere. The large capacitance of the capacitor in an ambient atmosphere is attributable to the formation of electric double-layer with large electric charge at the interface between the composite and ACP in the capacitor due to the water adsorption. 99103166 Electrochemical behavior of nickel deposited on reticulated vitreous carbon Czerwinski, A. et al. 1. Power Sources, 1999, 77, (l), 28-33 The electrochemical performance of nickel deposited on reticulated vitreous carbon (RVC) has been investigated in solutions of KOH. For comparison, the study of sintered nickel and nickel deposited on gold wire behaviour were also included. Our results indicate that the RVC covered with nickel is a good carrier for Ni(OH)z/NiOOH, an electrode material,