K. Micka

Voltammetric study of an iron electrode in alkaline electrolytes

Abstract The electrochemical behaviour of a pure iron electrode was studied by cyclic voltammetry in solutions of KOH containing LiOH, Na 2 S or SeO 2 . The maximum charge delivered by the electrode in one cycle was observed in the concentration ranges 1.1 – 2.4 M KOH and 10 −4 – 10 −3 M Na 2 S. Sulphide ions enhance the anodic reaction, while LiOH enhances the cathodic reduction of Fe(OH) 2 . The effect of SeO 2 is similar to that of Na 2 S, but it is considerably weaker; its advantage compared to the sulphide is that the reduction of Fe(OH) 2 is better separated from the hydrogen evolution peak, thus improving the charging efficiency.

Study of iron oxide electrodes in an alkaline electrolyte

Abstract Electrodes were prepared by pressing a mixture of iron oxides with a conducting component and a plastic binder, and their electrochemical behaviour in aqueous KOH solution was studied with regard to the influence of doping agents, impurities, and other factors. The discharge capacity of the electrodes was substantially enhanced by adding a conducting component such as acetylene black, and decreased when impurities in the iron oxides, mainly manganese, were present. Of the doping agents, sulphide ions proved most effective in increasing the discharge capacity.

Theory of porous electrodes—XIV the lead-acid cell

Abstract Based on the theory of the positive and negative plates of the lead-acid battery, a system of six partial differential equations and one integral equation was derived describing the behaviour of the complete cell. The theoretical discharge behaviour of the plates either separately or in a cell was compared. The theoretical discharge capacity of a lead-acid cell at normal temperature and discharge rates is limited by the positive plate. The theory shows that a certain optimum plate distance exists at which the cell capacity is highest.

Influence of grid design on current distribution over the electrode surface in a lead-acid cell

The current distribution over the plate surface in lead-acid cells was determined by means of a newly proposed method based on electrical measurements on a model. The method, which is much simpler than mathematical analysis of model systems, can be used to find the optimum grid design. Six illustrative examples and mathematical formulae for two special cases are presented.

Current distribution over the electrode surface in a lead-acid cell during discharge

The current distribution over the plate surface in lead-acid cells in the course of discharge was determined mathematically by using the equivalent circuit method. The dependence of the internal cell resistance on the current and charge passed was determined by measurements on a laboratory cell. Six cell variants were considered differing by the location of tabs serving as current terminals. The results are presented in the form of 3D diagrams at various states of discharge. To make the current distribution nearly uniform, extended current tabs located at opposite ends of the plate electrodes were proposed.

Theory of porous electrodes—XVI. The nickel hydroxide electrode☆

Abstract A model of the positive plate of a nickel—cadmium accumulator is proposed, based on the known electrochemical behaviour of hydrated nickel oxides and on transport equations similar to those used previously for the cadmium electrode. The mathematical treatment of this model allows to predict the theoretical discharge characteristics, which are compared with those measured on a real electrode. A comparison of the calculated and measured discharge time suggests that the composition of the oxidised form is intermediate between NiO 1.5 and NiO 1.8 .

Plastic-bonded electrodes for nickelcadmium accumulators. X. The nature of the second discharge step of nickel oxide electrodes

Abstract The second discharge step of nickel oxide accumulator electrodes is suppressed in the presence of a Teflon binder and/or cobalt, cerium, or manganese hydroxide, whereas the first discharge step increases. This behaviour is discussed in terms of ohmic resistance effects and semiconducting properties of the active material.

Study of structural factors of lead-acid battery electrodes

Abstract The electrolyte conductivity in the pores, and the true and apparent densities of the active mass, were measured on electrodes of a starter-type lead-acid battery in various stages of discharge, and the porosity of the plates and the tortuosity factor of the pores were evaluated. The results suggest that the charged, cycled positive plates contain a certain fraction of lead dioxide of a lower density, probably amorphous, which is reduced preferentially. Transport restrictions are more important in positive than in negative plates. Volume changes of a negative plate during cycling were found to be reversible, while with a positive plate they were irreversible.

Comparative study of porous iron electrodes

Abstract Sintered porous iron electrodes prepared from various materials were tested and compared with similar electrodes from different manufacturers. The important role of sulfide ions as activating agent was substantiated. A common feature of the electrodes under study is a relatively high rate of self-discharge, which can only partly be attributed to the presence of impurities, mainly manganese, in the active material and/or in the current collector.

Plastic bonded electrodes for nickel-cadmium accumulators. III. Influence of active layer composition on galvanostatic and potentiostatic discharge curves

Abstract Studies on the addition of a conducting component (carbon black, graphite, carbonyl nickel) and poly(tetrafluoroethylene) as binder to the active material used in pocket-type nickel oxide electrodes have shown that the second discharge step, which is observed in the discharge curve of a pressed nickel oxide electrode in the potential range from −100 to −600 mV (Hg/HgO), can be markedly influenced or fully suppressed as in the case of a sintered nickel oxide electrode. The existence of this discharge step is attributed to differences in the ohmic contacts of the electroactive particles in the pressed electrode.