Swargam Sathyanarayana

Insoluble anode of α-lead dioxide coated on titanium for electrosynthesis of sodium perchlorate

Lead dioxide is an important electrode material due to its stability under aggressive conditions (such as acidity of the electrolyte and high anode potentials), high electronic conductivity and low cost of material. Two major areas of applications of lead dioxide are leadacid batteries and electrosynthesis. Lead dioxide exhibits different morphological forms of which the orthorhombic a-form and the tetragonal//-form have been extensively studied. Methods of preparation of these two forms of lead dioxide as well as their characteristics have been reviewed [1, 2]. Generally, the preferred form of this electrode material in lead-acid batteries, as well as for electrosynthesis applications, is the fl-form. In spite of the fact that a-PbO2 is superior to fi-PbO2 both in electronic conductivity [1] as well as electrochemical stability [3], no study appears to have been made to evaluate the suitability of a-PbO2 as an electrode material. In this paper we report our results on the preparation of an a-PbO2 electrode coated onto a titanium substrate (a-PbO2 (Ti)) and its use as an insoluble anode for the electro-oxidation of sodium chlorate to sodium perchlorate.

Impedance peaks of sealed nickel/cadmium cells at low states-of-charge

Abstract The impedance of sealed nickel/cadmium cells is measured at low states-of-charge that correspond to a cell e.m.f. range of 0.0 to 1.3 V. The results show that the impedance exhibits a pronounced maximum between 0.3 and 0.45 V. It is concluded that the impedance maxima are due to physicochemical processes taking place at the nickel oxide electrode. The impedance of the nickel oxide electrode is dominated by three different phenomena: (i) a Ni(II)/Ni(III) reaction between 1.3 and 0.8 V; (ii) a double-layer impedance between 0.8 and 0.3 V; (iii) a hydrogen evolution reaction between 0.3 and 0.0 V.

Impedance parameters of individual electrodes and internal resistance of sealed batteries by a new nondestructive technique

A new robust method for the nondestructive determination of impedance parameters of the individual electrodes of sealed batteries has been developed. In this method, a battery is discharged at a constant current of about 2000 h (or less) rate for a few seconds only. The discharge transient of voltage against time is analysed theoretically to give effective double layer capacitances and charge transfer resistances of battery cathode and anode separately, as well as the internal resistance of the battery. Experimental data from discharge transients are processed with a new procedure which is immune to normal measurement errors and which permits a resolution of the parameters of the anodic and cathodic relaxation processes even if their time constants are not far apart. The correctness of the method is verified by simulation studies, and applied to sealed recombinant type lead-acid batteries. Diffusion resistance is shown to be negligible under the test conditions. The effects of switching transients and any series inductance are eliminated by the method. The results are directly relevant to improved battery design and failure analysis.

Alternating-current impedance of magnesium/manganese dioxide dry cells in absence of anode-film breakdown

Alternating current impedance of magnesium/manganese dioxide dry cells has been measured under conditions that do not harm the protective passive film on the magnesium electrode. Several electrical equivalent-circuits for the cell have been theoretically analysed, and a comparison of theoretically derived criteria with experimental results has led to the choice of the most suitable model. In principle, the methodology of measurement and analysis can be applied to other battery systems that involve reactive metals covered by protective films, in order to obtain information on the electrochemical properties of the film-covered metal/solution interface under non-destructive conditions.

Experimental and theoretical investigation of voltage transients of magnesium/manganese dioxide dry cells in absence of anode-film breakdown

The film-covered anode/solution interface plays a crucial role in determining the performance of high-energy primary batteries based on lithium, magnesium, aluminium, etc. The present study describes improvements over earlier attempts to analyze voltage transients of magnesium/manganese dioxide

The influence of some fluoroanions on the anodic oxidation of chlorate ion to perchlorate ion at a lead dioxide electrode

(Mg/MnO_2)

Voltage delay during constant-current or constant-resistance discharge of Mg-MnO2 dry cells: A comparative study

dry cells for the non-destructive evaluation of the electrochemical properties of the film-covered magnesium/solution interface. Equivalent-circuit analogs for the anode/solution interface are proposed and the most plausible set of models identified. The anode-film resistance and its temperature dependence are evaluated. The technique developed for

Temperature dependence of hydrogen evolution reaction on nickel oxide electrode in sealed nickel/cadmium cells

Mg/MnO_2

Electrode kinetics of a nickel/cadmium cell and failure-mode prediction. Estimation of equivalent resistance of an internal short

cells can be extended, in principle, to other battery systems based on lithium, aluminium, calcium, etc., and can be exploited for quality control and design optimization of such cell.

Open circuit voltage recovery of discharged and shorted nickel-cadmium cells

Both NaF and