01773 Thermal batteries modeling, self-discharge and self-heating

01773 Thermal batteries modeling, self-discharge and self-heating

11 Engines (transport battery development) Transport battery development 06/01767 Effect of substrate pre-coating on adhesion of sintered nickel plaq...

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11 Engines (transport battery development)

Transport battery development 06/01767 Effect of substrate pre-coating on adhesion of sintered nickel plaques for electrode application in rechargeable batteries Chani, V. I. et al. Journal of Power Sources, 2005, 142, (1-2), 370-381. The battery industry sees a need to improve the adhesion strength between porous nickel plaques and substrates in sintered nickel electrodes in order to reduce the use of nickel and to achieve higher battery capacity. This paper reportS on the use of a thin buffer layer to enhance plaque/substrate adhesion. In particular, the authors have attempted to improve adhesion performance of conventional sintered plaques produced from filamentary Ni powders (INCO-255, particle size 2.2-2.8 gm) through the introduction of a thin, intermediate layer made of finer Ni powders (INCO Type 110 and INCO Type 210, particle size 0.8-1.5 gm and 0.5-1.0 ~tm, respectively). The process consists of two steps. First, a buffer layer was applied from a slurry containing the finer Ni powders. After drying, the substrate was coated again with a slurry containing standard Type 255 powder. A vertical coating apparatus with periodically contacting blades was designed to produce thin, uniform buffer layers with low surface density (1-10 mg cm-2). For adhesion testing, a tensile strength test specimen holder was modified to ensure planar loading of the interface. Significantly enhanced bonding between the plaque and substrate was observed due to the introduction of the buffer layer.

06/01768 Electrode surface modifications improve cathode hydrogen production and anode capacity in Ni-MH batteries Angelo, A. C. D. hlternational Journal of Hydrogen Energy, 2006, 31, (2), 301 302. This paper reports results from electrochemical evaluations of electrodes used as cathodes for a hydrogen evolution reaction and anodes in N i - M H batteries that had been surface-modified by microencapsulation, co-deposition and sol-gel methods. The surface modifications produced actual improvements in the corresponding electrochemical reactions by enhancing the performance and/or the mechanical stability of the electrode material.

06•01769 Government policy and the development of electric vehicles in Japan Ahman, M. Energy Policy, 2006, 34, (4), 433 443. The aim of this paper is to analyse the role that the Japanese Government has played in the development of alternatives to conventional vehicles, the effect of government programmes, and the importance of technical flexibility in government support schemes. The focus is on battery-powered electric vehicles (BPEVs), hybrid electric vehicles (HEVs), and fuel cell electric vehicles. The effects of government policy and the process of innovation are analysed from a systems approach drawing on the literature regarding technical change and innovation. The whole chain of government support, including the context in which these different policies have been implemented since the early 1970s, is studied. The Japanese Government has adopted a comprehensive strategy including R&D, demonstration programmes and market support guided by long-term strategic plans. The role of the Government has been that of a conductor in the development process supplying both R&D support and artificially created niche markets, and easing the way for targeted technologies by means of legislation and standards. Despite this, the targeted technology (the BPEV) has not been established on the market. However, the recent market success of the H E V can partly be attributed to the government support of the BPEV technology. The enabling component, the electric drivetrain, was developed for automotive use within the BPEV programmes offered by the MITI. This technology was later utilized in the HEV. The history of BPEVs in Japan demonstrates that "picking winners' in government policy is not easy. Despite a sustained and ambitious policy by the MITI, the development of alternative vehicles never unfolded according to plan. The success factors for policy seem more related to technology specific features than the particular policy style. The conclusion is that flexibility, adaptability and cooperation in terms of technical choice is necessary in policy. This increases the chances of a technology surviving the long journey from idea to competitive technology. Another conclusion is that market support, even in the early phases of development, is an important complement to R&D for gaining experience and building markets.

06/01770 Performance analysis of a tubular solid oxide fuel cell/micro gas turbine hybrid power system based on a quasi-two dimensional model Song, T. W. et al. Journal of Power Sources, 2005, 142, (1 2), 30-42. A quasi-two dimensional (quasi-2D) model is proposed as a tool to predict the performance of solid oxide fuel cell (SOFC) system composed of bundles of tubular SOFCs and internal reformers. The model is developed by considering heat and mass transfer character-


Fuel and Energy Abstracts July 2006

istics mainly along the longitudinal direction of the system, and the electrochemical reaction in its perpendicular direction. With this model, the temperature distribution in the fuel and the air streams along the longitudinal direction of the bundles of tubular SOFCs and internal reformers can be easily predicted. The predicted cell temperature along the longitudinal direction of the tubular SOFC shows important phenomena, which include the temperature rise near the entrance of the fuel cell by the electrochemical reaction and its decrease due to heat transferred from the fuel cell to the internal reformer that absorbs heat in reforming reactions. Also, it is found that different system arrangements and component characteristics influence significantly the heat-transfer characteristics, and possibly the system performance. The results from the quasi-2D model are applied to the performance analysis of a tubular SOFC/micro gas turbine (MGT) hybrid system.

06101771 Prediction of gas solubility in battery formulations Kolfir, P. et al. Fhdd Phase Equilibria, 2005, 228-229, 59-66. This paper describes the development of a thermodynamic model for predicting solubilities of nine gases (H2, N2, CO, Ar, O2, CH4, C2H4, C2H6, CO2) in battery electrolyte formulations composed of five organic carbonates (cyclic and linear) and lithium salts (LiPF6) between 283 and 363 K and <1 MPa. The PSRK equation of state was combined with the N R T L expression for activity coefficients from previos studies and used for correlating available gas solubility data. The prediction ability of the PSRK model was tested by correlating gas solubility data in propylene carbonate and predicting the gas Henry's constants in other carbonates. The PSRK predictions of missing combinations and multicomponent systems and were validated by experimental measurements, The PSRK model is shown to predict gas solubilities in ternary battery formulations with accuracy within 10%. The prediction of gas solubility was also tested using the quantum mechanical/COSMO-RS method. The COSMO-RS method did not require any prior experimental information and produced quantitatively correct results for binary gas + carbonate systems.

06•01772 The effect of temperature on capacity and power in cycled lithium ion batteries Belt, J. R. et al. Journal of Power Sources, 2005, 142, (1-2), 354-360. The Idaho National Laboratory (INL) tested six Saft America HP-12 (Generation 2000), 12-Ah lithium ion cells to evaluate cycle life performance as a power assist vehicle battery. The cells were tested to investigate the effects of temperature on capacity and power fade. Test results showed that five of the six cells were able to meet the power assist power and energy goals at the beginning of test and after 300,000 cycles using a battery size factor (BSF) of 44.3 cells. The initial static capacity tests showed that the capacities of the cells were stable for three discharges and had an average of 16.4 Ah. All the cells met the self-discharge goal, but failed to meet the cold cranking goal. As is typical for lithium ion cells, both power and capacity decreased during the low-temperature thermal performance test and increased during the high-temperature thermal performance test. Capacity faded as expected over the course of 300,000 life cycles and showed a weak inverse relationship to increasing temperature. Power fade was mostly a result of cycling while temperature had a minor effect compared to cycle life testing. Consequently. temperature had very little effect on capacity and power fade for the proprietary G4 chemistry.

06/01773 Thermal batteries modeling, self-discharge and self-heating Schoeffert, S. Journal of Power Sources, 2005, 142, (1 2), 361-369. First principal calculations made with the 'Ether' code appeared pessimistic when compared with results for batteries with a duration from 50 s upwards. Subsequent examination into the reason for this confirmed that 'Ether' predictions were correct in themselves, however a significant self-heating effect was necessarily taking place, this being reinforced by treatment of all the available information. The challenge for improved thermal battery modelling was then to determinate pertinent laws for this effect and to obtain accurate measurements of the phenomenon itself. An experimental method was used where the results obtained from reusable clamp stacks were subjected to mathematical treatment using 'Ether'. This has been successfully carried out in two similar cases and has clearly confirmed the ~remises: in these cases, the addition of a constant 400 W (kg of cells)- internal heat generation allows for a close matching between numerical and experimental results globally, up to the exhaustion of the electrochemically active products. Correlative on the electrochemical side, when compared to single-cell tests, extended self-discharge clearly takes place in clamp stacks. Thermal batteries modelling - which has already been very useful for years - progresses toward best and appears on the way to make accurate predictions through deep physical knowledge, although there is still significant work to do.