Cadmium Electrode Research Articles

The origin of capacity loss in the pocket plate cadmium electrode

Electrical testing of negative limited mono-pocket plate cells, cyclic voltammetry and surface analysis by X-ray diffraction were used to investigate the origin of the second discharge plateau at the cadmium pocket plate electrode. The electrical testing results show that there is a direct coupling between the appearance of a second discharge plateau and a high carbonate concentration in combination with high discharge rates (1 C 5A). An exchange to a carbonate free electrolyte results in recovering of the cell. Voltammetric measurements show that the reduction of CdCO 3 takes place in the same potential region as the reduction of Cd(OH) 2. Thus, the presence of CdCO 3 in the discharged negative electrode cannot give rise to a second voltage plateau or capacity loss. However, a decrease in the hydroxide concentration results in a positive shift of the oxidation potential. These results are interpreted in the context of the porous structure of the pocket plate cadmium electrode. For a high carbonate concentration and large discharge rates, the hydroxide concentration within the pores are depleted leading to a positive potential shift and the appearance of a second discharge plateau.

Role of Heterophase Interactions between Cadmium and Nickel in Cadmium Electrode Activation

The structural and electrochemical characteristics of cadmium electrodes with nickel introduced in metallic state into the active material of the electrode by electroless plating were studied. The specific role played by heterophase interactions between nickel and cadmium in the mechanism of cadmium electrode activation was substantiated experimentally.

Influence of charge density and electrolyte concentration on the electrical double layer characteristics at rough cadmium electrodes

A new effective diffuse layer thickness dependent surface roughness model, based on the non-linear Poisson–Boltzmann theory, has been used for the interpretation of impedance data for rough cadmium electrodes. The so-called electrochemical roughness function values at various electrode potentials and surface charge densities have been calculated. It was found that the roughness function values, the inverse value of Parsons–Zobel plot, as well as the fitting coefficient in the Valette–Hamelin approach, obtained from the electrochemical impedance data, are effective (seeming) parameters and do not characterise the real geometrical structure of electrode surface. However, they characterise the deviation of real experimental system from ideally smooth (flat) surface. In the region of moderate rational electrode potentials 0≤| E|≤0.2 V and surface charge densities (1≤| a|≤4 μC cm −2) the roughness function rises with the decrease of the effective thickness of diffuse layer. At higher electrode potentials and surface charge densities the surface roughness function levels of to the constant value, i.e. to the so-called geometrical surface roughness value. The new effective diffuse layer thickness dependent surface roughness theory needs future corrections taking into account the role of crystallographic inhomogeneity of the geometrically rough electrode surface, i.e. the dependence of the local surface charge density on the crystallographic structure of energetically homogeneous regions exposed on the macro-polycrystalline electrode surface.

Silver based batteries for high power applications

The present status of silver oxide–zinc technology and applications has been described by Karpinski et al. [A.P. Karpinski, B. Makovetski, S.J. Russell, J.R. Serenyi, D.C. Williams, Silver-Zinc: status of technology and applications, Journal of Power Sources, 80 (1999) 53–60], where the silver–zinc couple is still the preferred choice where high specific energy/energy density, coupled with high specific power/power density are important for high-rate, weight or size/configuration sensitive applications. Perhaps the silver oxide cathode can be considered one of the most versatile electrode materials. When coupled with other anodes and corresponding electrolyte management system, the silver electrode provides for a wide array of electrochemical systems that can be tailored to meet the most demanding, high power requirements. Besides zinc, the most notable include cadmium, iron, metal hydride, and hydrogen electrode for secondary systems, while primary systems include lithium and aluminum. Alloys including silver are also available, such as silver chloride, which when coupled with magnesium or aluminum are primarily used in many seawater applications. The selection and use of these couples is normally the result of a trade-off of many factors. These include performance, safety, risk, reliability, and cost. When high power is required, silver oxide–zinc, silver oxide–aluminum, and silver oxide–lithium are the most energetic. For moderate performance (i.e., lower power), silver oxide–zinc or silver–cadmium would be the system of choice. This paper summarizes the suitability of the silver-based couples, with an emphasis on the silver–zinc system, as primary or rechargeable power sources for high energy/power applications.

Study of Cadmium Electrochemical Deposition in Sulfate Medium

The cadmium electrochemical deposition process from sulfate medium was studied by means of different electrochemical techniques in both stationary and nonstationary diffusion regimes. The kinetics of the electrochemical reduction of cadmium on solid cadmium electrodes was examined and the kinetic parameters are presented, as well as the diffusion coefficient derived from the different techniques. Temperature has an important effect on the cadmium reduction kinetics, and the activation energy of the process was evaluated. The electrochemical deposition of cadmium is a complex process due to the coexistence of adsorption and nucleation processes; the adsorbed electroactive species appears to be , and we propose a mechanism for cadmium electrodeposition on solid cadmium electrodes. © 2000 The Electrochemical Society. All rights reserved.

Electronic Network Modeling of Rechargeable Batteries: I. The Nickel and Cadmium Electrodes

This work introduces electronic network modeling as a new way of simulating battery behavior. Mathematical descriptions are given for the Ni and Cd electrode charge/discharge reactions. These mathematical descriptions are subsequently introduced in the form of electronic components, combined in an electronic network. The advantage of this way of modeling is that it provides a compact electronic model of a battery, which can be used in any electronic‐circuit simulation, providing a tool to develop new battery‐management systems. In addition, due to the discretization of the electrochemical reactions into separate electronic components, local currents and overpotentials occurring in the system can be studied. This information can be used to investigate the origin of certain battery behavior.

Surface roughness of bismuth, antimony and cadmium electrodes

Electric double layer properties of variously treated Bi, Sb and Cd electrodes were studied in terms of the Debye length dependent roughness theory, recently developed by Daikhin et al. The geometrical roughness factor, root mean square departure of the surface from flatness, height of surface roughness and the medium lateral correlation length values have been obtained. According to the experimental data and results of theoretical simulation the surface roughness rises in the order of Bi electrodes: electrochemically polished single crystal Bi(111) plane<cut at the temperature of liquid nitrogen Bi(111) plane<Bi solid drop electrode with additionally remelted surface<cut at the room temperature Bi(111) plane<electrochemically etched Bi(111) plane<chemically etched Bi(111) plane. This order of the electrode surface roughness was in agreement with the ex situ AFM data. At small electrolyte concentrations ( c el≤0.01 M) the deviation of experimental roughness function–inverse Debye length curves from the theoretically simulated ones has been observed, explained by the influence of energetic inhomogeneity of polycrystalline surfaces on the non-equal surface charge density at various homogeneous regions, exposed at the macro-polycrystalline electrode surface.

Activation Energy of Electron Transfer between a Metal Electrode and Reagents of Nonspherical Form and Complicated Charge Distribution. Cr(EDTA) Complexes

An approach is suggested in order to investigate the mechanism of interfacial electron-transfer processes with reagents of nonspherical form and complicated charge distribution. Chelate chromium(III) ethylenediaminetetraacetate (EDTA) complexes are regarded as a good model system. A series of SCF quantum chemical calculations at the ZINDO/1 level were performed for the systems Cr(EDTA)(H2O)n- (n = 0, 1, 2, 3, and 4). A quinquedentate complex Cr(EDTA)H2O- was found to be energetically more favorable compared to Cr(EDTA)-. The interaction of Cr(EDTA)- with a cadmium electrode (modeled as a 19-atomic planar cluster) was investigated as well. The analysis of both the potential energy surfaces and the partial charge transfer allows the explanation of the absence of “specific” interaction between Cr(EDTA)- complexes and mercury-like metals observed experimentally. A way to estimate the inner-sphere contribution (Ein) to reorganization energy is proposed. The inner-sphere asymmetry (nonequality of Ein values for reduction and oxidation) was found, which plays a significant role in the theoretical analysis of the activation energy. To obtain estimates of the solvent reorganization energy, the shape of reagents was approximated by ellipsoids. The detailed atomic charge distribution in oxidized and reduced complexes was employed to provide a “microscopic” description of electrical double layer effects. Additional ab initio SCF calculations with several basis sets of different quality were performed for the analysis of the charge distributions. The activation energies for several orientations of Cr(EDTA)- and Cr(EDTA)H2O- relative to the metal surface were calculated for two values of the electrode charge densities. It is concluded that a sufficient interpretation of relevant experimental data is not possible without calculations of the reaction pre-exponent.

ニッケル水素電池用負極材料の最近の進歩

Major activities in the direction of developing a commercial nickel-metal hydride rechargeable batteries occurred in the middle 1980s and some Japanese companies started to commercialize these batteries for small computer and electronic appliances in the early 1990s. For most of batteries, MmNi5 (Mm = misch metal) based alloys are exclusively utilized. As metal hydride electrodes could ideally replace the cadmium electrode of nickel-cadmium battery and had much higher electrode capacities, these batteries were easily accepted in commercial. After that, annual production of hydrogen-absorbing alloys has risen drastically. Main research and development for hydrogen-absorbing alloys used in commercial nickel-metal hydride batteries is now directed toward lower price and higher capacity. MmNi5-based alloys are still under development to improve their electrode performances and to reduce the cost of raw materials. Other hydrogen absorbing alloys with higher capacities such as Zr-Mn-Ni, Ti-V-Ni and Mg-Ni systems are also under investigation at both the fundamental and applied levels.

Adsorption of organic compounds and hydrophilicity of bismuth, cadmium and antimony electrodes

The adsorption behavior of various organic compounds at bismuth, antimony, cadmium, mercury and other “mercury-like” metals has been discussed. The systematic trends of the influence of the chemical nature of electrode metal and adsorbate to the molecular interaction parameter, a; limiting Gibbs adsorption, Γ A, max; and Gibbs energy of adsorption, Δ G A 0, have been analyzed. The ingredients of the total Gibbs energy of organic compounds adsorption have been found. A new more general method for obtaining the metal-water; interaction Gibbs energy has been worked out and used. It was found that the dependence of Gibbs energy of metal-water interaction on the chemical nature of metal and aliphatic organic compound studied is weak. Only in the case of chemically very different metals, for example for Sb and Zn, the difference of Gibbs energy of metal-water interaction values is somewhat higher than the exactness of the determination of the experimental values of Gibbs energy of organic compound adsorption.

Electrochemical synthesis of diethyl fluoromethanephosphonate

The electrochemical reduction of diethyl chlorofluoromethanephosphonate has been studied. It has been shown that, in mildly basic media (pH 7.5–8) of water-alcohol solutions, replacement of the chlorine of the starting compound by hydrogen occurs at lead, cadmium and zinc electrodes with high selectivity. The procedure affording diethyl fluoromethanephosphonate in a yield of 85%–90% has been elaborated.

Influence of surface pretreatment of bismuth and cadmium electrodes to the electric double layer and adsorption characteristics of organic compounds

Influence of the surface structure of electrodes on the electric double layer properties, as well as on the adsorption characteristics of various organic compounds has been investigated by cyclic voltammetry, impedance and electron microscopic methods at variously prepared Bi, Sb and Cd electrodes. The systematic trends of the influence of surface roughness and energetic inhomogeneity on the electric double layer characteristics (value of differential capacity, potential of diffuse minimum, Parsons-Zobel factor, inner layer capacity, roughness function) have been established. The dependencies of the shape of adsorption-desorption maxima of organic compounds and other adsorption parameters (values of attraction interaction, adsorption equilibrium constant, shape of adsorption isotherm) on the electrode surface structure have been investigated. The Debye-length dependent roughness function has been calculated. The approximate values of the linear parameter of homogeneous regions, which prevail at the surface of polycrystalline electrodes have been calculated using various theoretical models. The established values of linear parameters of homogeneous regions have been compared with the characteristics obtained from the electron microscopic studies.

Predictions from the Macrohomogeneous Model of an Aerospace Ni‐Cd Battery

The mathematical porous‐electrode model developed at Texas A&M University has been combined with a planar model for the surface active layer to formulate a pseudo two‐dimensional model for a sealed nickel‐cadmium cell. The porous electrode model is based on a macrohomogeneous description of the electrodes and takes into account various processes such as mass transport in the liquid phase and porosity and conductivity changes in the solid phase. The planar electrode model describes the processes occurring across the surface layer of active material, i.e., solid‐state diffusion of protons and conductivity changes in the nickel oxide, and the charge‐transfer across the film‐electrolyte interface. Also, various routines have been added to the pseudo two‐dimensional model thus integrated, to allow predictions for any nickel‐cadmium battery under any desired charge‐discharge schedule. From a comparison with the experimental data of an aerospace cell, the model parameters describing charge‐discharge behavior of a Ni‐Cd cell have been optimized to obtain a closer prediction with the experimental data. Upon optimizing the model parameters, the performance of the aerospace nickel‐cadmium cell has been simulated under various experimental conditions, i.e., at different rates and temperatures. Also, generic Ragone plots for the cell and typical Tafel plots for cadmium and nickel electrodes at different states of charge have been constructed from the simulations. Finally, this model has been made available for any interested user through COSMIC NASA's Computer Management and Information Center, along with documentation in six volumes describing the code, principles, and operating instructions.

Effect of Organic Additives on Cadmium Electrode in Nickel-Cadmium Batteries

The effect of some organic additives on the capacity performance of pressed pellet and sintered plate type cadmium electrodes has been studied. The additives under investigation are benzimidazole and polyvinyl alcohol. The organic electrode additives for the cadmium electrode of the nickel-cadmium battery is aimed mainly for increasing the discharge capacity and minimising the self discharge. It is found that pressed electrode can be used for low rates of discharge whereas the sintered electrodes can be used for both low and high rates of discharge. It is found that pressed electrode can be used for low rates of discharge whereas the sintered electrodes can be used for both low and high rates of discharge. The organic additive sources show better low and high rate performance for sintered cadmium electrodes.

Electrochemical behaviour of addition agents impregnated in cadmium hydroxide electrodes for alkaline batteries

The development of electrode additives for the cadmium electrode of the nickel/cadmium battery is aimed mainly at increasing the discharge capacity and minimizing self-discharge. The dissolution and passivation of porous cadmium electrodes containing hydroxide and the relative stability of oxides are of importance in understanding the reversible behaviour of the cadmium electrode. Under standard conditions, the equilibrium potential of Cd(OH) 2/Cd lies above the hydrogen-evolution reaction when the cell is not in use, and the active material of the cadmium electrode undergoes self-reductive dissolution (i.e., loss of active material) accompanied by oxygen evolution. The triangular potential sweep voltammetric technique is used to determine the reversibility of the cadmium electrode in alkaline solution. The role of additives such as Ni(NO 3) 2 (0.25–0.1 M) and FeSO 4 (0.1–0.4 M), TiO 2 (0.01–0.03 M) and Na 2S (0.01–0.03 M) in Cd(NO 3) 2 on the reversibility of the electrode are discussed. The effect of discharge rate on the cyclic efficiency is also investigated. Self-discharge currents are determined by potentiostatic polarization method.

Electrochemical approach to monitoring metal exchange reaction of acetylacetonate complexes with cadmium, copper and zinc ions

Metal exchange reactions of acetylacetonate complexes with Cd(II), Cu(II) and Zn(II) ions were investigated by using cadmium and copper ion selective electrodes. Changes in the electrode potential and pH of the solutions were monitored upon adding the pertinent metal Zn(II) of the acetylacetonate (AA) complexes. In the reverse system in which a stable Cu-AA complex exists in the solution prior to adding a secondary metal ion (Cd(II) or Zn(II)), no Cu(II) was replaced by either ion. In the systems containing Cd(II) and Zn(II) as a complexed form with AA or as free ions, the exchange reactions were not explained by considering the equilibrium stability constants of the Cd-AA and Zn-AA complexes.

Cerium Content and Cycle Life of Multicomponent AB 5 Hydride Electrodes

Multicomponent hydrides are attractive replacements for the cadmium electrode in nickel‐cadmium batteries. The archetype compound of the alloy class is , but in a typical battery electrode mischmetal is substituted for La and Ni is substituted in part by various metals. While the effects of Ni substitution have been widely studied, relatively little effort has been focused on the effect of La substitution. Cerium is the predominant rare earth in normal mischmetal, and this paper deals with the effect on cycle life and storage capacity due to the increasing presence of Ce in the alloy series. Alloys were characterized by the determination of pressure‐composition relationships, molar volume of H in the hydride phase and electrode cycle life. The effects due to lattice expansion are taken into account. It was concluded that the rate of loss of electrochemical capacity per charge‐discharge cycle due to electrode corrosion was significantly decreased by the presence of Ce.

Structural aspects of electrochemical adsorption on quasi-perfect silver and cadmium electrodes

The author's data about the adsorption of inorganic ions, neutral organic molecules and water dipoles on so-called quasi-perfect silver and cadmium electrodes are summarized and compared. The influences of electronic structure of metal adsorbent atoms ( ie chemical nature of the adsorbent) and of surface electrode structure ( ie crystallographic orientation and growth step density) are estimated. Conclusions are drawn about the importance of the electrode surface structure in the processes of electrochemical adsorption.

High performance nickel-cadmium cells for electric vehicles

A new concept of a cadmium electrode associated with a lighter nickel structure, a multi-cell module technology, allows the proposal of a very promisig alternative power source for electric vehicle (EV) batteries, the usable specific energy being 31% of the theoretical value. Every characteristic of this Ni-Cd module (i.e., specific energy and power, energy and power density, energy efficiency, life and reliability) gives the best performing EV battery, to date. Thus, with the efficient support of two major French car manufacturers and the French government, SAFT will launch, during Spring '95, the first pilot line of EV Ni-Cd module manufacturing.

Kinetics of the electroreduction of anodically formed cadmium oxide layers in alkaline solutions

The kinetics of the potentiostatic electroreduction of cadmium oxide layers on polycrystalline cadmium electrodes have been investigated in 0.01–1.0m NaOH solutions. The study was undertaken to determine the influence of passive film formation conditions on the electroreduction process of the anodically produced hydrous cadmium hydroxide-oxide layers. By properly adjusting the electroreduction conditions the cathodic potentiostatic current transients can be satisfactorily described by a nucleation and growth mechanism involving the participation of soluble Cd(II) and passivating anodic species. Experimental data were analysed by the application of non linear least squares fit routines. From the parametric identification procedure coherent potential dependencies of the corresponding fitting parameters as well as reasonable values of the physicochemical constants included in the reaction model, have been obtained. In this way it is possible to correlate kinetic data of the electroreduction process of the anodic oxide layers to make a discrimination between the different mechanistic contributions to this complex reaction involving several steps.