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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Raman spectral observation of a new phase observed in nickel electrodes cycled to failure

A ‘new phase’ is reported in nickel electrodes from Ni/H2 boilerplate cells which were cycled to failure in electrolyte of variable KOH concentration (21–36%). Raman spectra clearly show the presence of this phase, and these spectra have been used to estimate the amounts present on these electrodes. Ten of twelve electrodes examined contain this new phase. The cycle life at higher KOH concentrations (31 and 36%) was greatly reduced, and nickel electrodes from these cells exhibited extensive amounts of this new phase. The presence of this ‘new phase’ correlates with cell failure defined by low end of discharge voltages. It is proposed that the lowered capacity and failure of these electrodes was caused by loss of active mass and formation of a phase with reduced electrochemical activity. These results indicate that formation of this new phase is accelerated at higher KOH concentrations.

Patricia L Loyselle↗
NASA NTRS1984

Past developments and the future of nickel electrode cell technology

The nickel hydroxide electrode has evolved over nearly 100 years from the pocket electrode structure through to the present design of a light weight, porous, plaque structure. Before discussing the historical aspects, it would be helpful to point out that there are basically two parts to the electrode: the active material and the current (electron) collector. Together they provide the essential properties for storing and converting the chemical energy into electrical energy and vice versa. The electrical energy is stored in the nickel hydroxide active material during charge, in which the electrode is oxidized. The chemical energy is converted back to electrical energy during discharge. The active material is itself initially non-conductive. Therefore it must be housed in a high conductivity metallic structure which serves as the current collector. This is, in turn, connected to another high conductivity metallic structure called the terminal.

Halpert, G.↗
NASA NTRS1986

A point defect model for nickel electrode structures

The Raman spectra for nickel electrode active mass indicate a single formula-unit crystallographic unit cell of the layered NiOOH-type. Empirical stoichiometric formulas require that extensive point defects, cation dopants and nickel vacancies, be incorporated on nickel sites. Structural differences between the alpha/gamma and beta/beta cycles, and the influence of cobalt addition on the structure will be discussed in terms of the point defect model. Other empirical data supporting the point defect model will be considered.

Loyselle, Patricia L.↗
NASA NTRS1996

High Performance Nickel Electrodes for Space Power Applications

Performance characteristics such as efficiency, specific energy density and power density of nickel electrodes are generally limited by the electrode microstructure and nature of the active material within the electrode matrix. Progress is being made in our laboratory in a collaborative effort with NASA-Lewis Research Center to develop lighter weight, mechanically stable and highly efficient nickel electrodes for aerospace applications. Our approach is based on an electrode microstructure fabricated from a mixture of nickel fibers as small as 2 microns diameter and cellulose fibers. Performance data in flooded cell tests and cycle life data are presented. Performance characteristics are compared to other electrode microstructures such as the Fibrex Fiber mat and the Fibrex Powder substrate. The flexibility of our electrode microstructure and the significant advantages it offers in terms of weight and performance are demonstrated, in particular, its ability to accept charge at high rates and to discharge at high rates.

Adanuvor, Prosper K.↗
NASA NTRS1989

Advances in lightweight nickel electrode technology

Studies are currently underway to further the development of lightweight nickel electrode technology. Work is focused primarily on the space nickel-hydrogen system and nickel-iron system but is also applicable to the nickel-cadmium and nickel-zinc systems. The goal is to reduce electrode weight while maintaining or improving performance thereby increasing electrode energy density. Two basic electrode structures are being investigated. The first is the traditional nickel sponge produced from sintered nickel-carbonyl powder and the second is a new material for this application which consists of a non-woven mat of nickel fiber. Electrodes are being manufactured, tested and evaluated at the electrode and cell level.

Coates, Dwaine↗
NASA NTRS1989

Advances in lightweight nickel electrode technology

Studies are currently underway to further the development of lightweight nickel electrode technology. Work is focused primarily on the space nickel-hydrogen system and nickel-iron system but is also applicable to the nickel-cadmium and nickel-zinc systems. The goal is to reduce electrode weight while maintaining or improving performance, thereby increasing electrode energy density. Two basic electrode structures are being investigated. The first is the traditional nickel sponge produced from sintered nickel-carbonyl powder. The second is a new material for this application which consists of a non-woven mat of nickel fiber. Electrodes are being manufactured, tested, and evaluated at the electrode and cell level.

Coates, Dwaine↗
NASA NTRS1985

Raman structural studies of the nickel electrode

Raman spectroscopy is sensitive to empirically controlled nickel electrode structural variations, and has unique potential for structural characterization of these materials. How the structure relates to electrochemical properties is examined so that the latter can be more completely understood, controlled, and optimized. Electrodes were impregnated and cycled, and cyclic voltammetry is being used for electrochemical characterization. Structural variation was observed which has escaped detection using other methods. Structural changes are induced by: (1) cobalt doping, (2) the state of change or discharge, (3) the preparation conditions and type of buffer used, and (4) the formation process. Charged active mass has an NiOOH-type structure, agreeing with X-ray diffraction results. Discharged active mass, however, is not isostructural with beta-Ni(OH)2. Chemically prepared alpha phases are not isostructural either. A disordered structural model, containing point defects, is proposed for the cycled materials. This model explains K(+) incorporation. Band assignments were made and spectra interpreted for beta-Ni(OH)2, electrochemical NiOOH and chemically precipitated NiOOH.

Cornilsen, B. C.↗
NASA NTRS1991

Raman Spectral Observation of a "New Phase" Observed in Nickel Electrodes Cycled to Failure

A "new phase" is reported in nickel electrodes from Ni/H boilerplate cells which were cycled to failure in electrolyte of variable kOH concentration. Raman spectra clearly show the presence of this phase, and these spectra have been used to quantify the amounts present in these electrodes (in the volume sampled by the laser beam) Raman spectroscopy has been found to be capable of differentiating the various phases which can be present in nickel .This differentiation is possible because of the structural variation observed for these phases. Ten of twelve electrodes examined contain at least some of this new phase. The presence of this "new phase" correlates with cell failure, and it is proposed that the presence of this phase may play a role in early electrode failure.

Loyselle, P. L.↗
NASA NTRS1989

Electrochemical behavior of heavily cycled nickel electrodes in Ni/H2 cells containing electrolytes of various KOH concentrations

A study has been made of charge and discharge voltage changes with cycling of Ni/H2 cells containing electrolytes of various KOH concentrations. A study has also been made of electrochemical behavior of the nickel electrodes from the cycled Ni/H2 cells as a function of overcharge amounts. Discharge voltages depressed gradually with cycling for cells having high KOH concentrations (31 to 36 percent), but the voltages increased for those having low KOH concentrations (21 to 26 percent). To determine if there was a crystallographic change of the active material due to cycling, electrochemical behavior of nickel electrodes was studied in an electrolyte flooded cell containing either 31 or 26 percent KOH electrolyte as a function of the amount of overcharge. The changes in discharge voltage appear to indicate crystal structure changes of active material from gamma-phase to beta-phase in low KOH concentrations, and vice versa in high KOH concentration.

Lim, H. S.↗
NASA NTRS1980

Nickel electrode plate thickening study

The rate of thickening of the nickel electrode with cycling, under geochronous conditions, was investigated. The experimental procedures used to study the effects of various operational parameters on the rate of the thickness growth are outlined. The parameters included temperature, electrolyte composition, manufacturing lot, cycle parameters, and reconditioning methods.

Bernhardt, M.↗
NASA NTRS1987

Structural models for nickel electrode active mass

Raman spectroscopic data allow one to distinguish nickel electrode active mass, alpha and beta phase materials. Discharges active mass is not isostructural with beta-Ni(OH)2. This is contrary to the generally accepted model for the discharged beta phase of active mass. It is concluded that charged active mass displays a disordered and nonstoichiometric, nonclose packed structure of the R3 bar m, NiOOH structure type. Raman spectral data and x ray diffraction data are analyzed and shown to be consistent with this structural model.

Cornilsen, Bahne C.↗
NASA NTRS1988

Structural models for nickel electrode active mass

Raman spectroscopic data allow one to distinguish nickel electrode active mass, alpha and beta phase materials. Discharges active mass is not isostructural with beta-Ni(OH)2. This is contrary to the generally accepted model for the discharged beta phase of active mass. It is concluded that charged active mass displays a disordered and nonstoichiometric, nonclose packed structure of the R3 bar m, NiOOH structure type. Raman spectral data and X ray diffraction data are analyzed and shown to be consistent with this structural model.

Cornilsen, B. C.↗
NASA NTRS1996

Mathematical models for electrochemical impregnation of nickel electrodes

Single step and two-step tetramer precipitation models for electrochemical impregnation of nickel electrodes are presented. The objectives for developing the impregnation model are: to predict the impregnation conditions for uniform loading, to develop quality control tools for electrode manufacturing, and to use it as basis for predicting the performance of batteries with non-uniform loadings. This paper, with the help of graphs and charts, discusses the development and application of the impregnation model.

Ho, Chien-Hsien↗
NASA NTRS1998

Lightweight Nickel Electrode Development Program

Because of its relatively high specific energy and excellent cycling capability, the nickel-hydrogen (Ni-H2) cell is used extensively to store energy in aerospace systems. For the past several years, the NASA Lewis Research Center has been developing the Ni-H2 cell to improve its components, design, and operating characteristics. The battery size and weight are crucial parameters in aerospace and spacecraft power systems for applications such as the International Space Station, space satellites, and space telescopes. The nickel electrode has been identified as the heaviest and most critical component of the Ni-H2 cell. Consequently, Lewis began and is leading a program to reduce the electrode's weight by using lightweight plaques.

Britton, Doris L.↗
NASA NTRS1982

Effects of the mode of storage on the capacity fading of the sintered nickel electrodes

A systematic investigation of the effect of temperature and two conditions of storage, shortened and open circuit, on the capacity fading of sintered nickel electrodes in NiCd batteries was conducted. All testing was done on sintered electrodes in flooded cells. Cycling tests to measure the capacity were performed at room temperature. The capacity out to one volt, a capacity useful for satellite applications. Test results indicated that: the shortened electrode showed a higher rate of loss than the open circuit electrodes; there was an increase in both modes with an increase in temperature; there was a loss of capacity with time of storage; a general degradation was observed as a function of time; shortened electrodes showed a higher end of charge than the open circuit ones; and at room temperature there was a lower loss in the open circuit electrode than in the shortened one.

Vyes, B.↗
NASA NTRS1983

Reconditioning and the nickel electrode

This effects of reconditioning on the performance of NiCd batteries are reviewed. These effects are correlated with cell experiments and individual electrode investigations. The effects of reconditioning on the positive electrode performance are found to be significant. A mechanism is proposed that rationalizes the operation of the nickel electrode and suggests that reconditioning minimizes depth of discharge stress during use and maintains uniformity of the active material.

Zimmerman, A. H.↗
NASA NTRS1986

Improvement of the process for electrochemical impregnation of nickel hydroxide electrodes

Nickel hydroxide electrodes containing 11g/dsqm hydroxide, with capacities of 3.6 to 3.8 Ah/dsqm were prepared at 353 K by electrochemical impregnation. The reproducibility of the results is obtained by readjusting the pH before each preparation. The control of each electrode is done during two cycles of charge and discharge following the manufacture by a potential relaxation method.

Comtat, M.↗