N.A. Hampson

The impedance of electrical storage cells

A brief review of the theory pertaining to the impedance of electrolytic cells is presented. Differences between the operational representations of cell impedances in the fields of electrochemistry and electrical engineering are noted. The experimental data on the impedance of complete batteries, available from the literature, is critically reviewed. The results are discussed in terms of the generation of a nondestructive,in situ, state-of-charge test.

Fundamentals of lead-acid cells: Part XI. Phase formation at solid and porous lead electrodes

Abstract The development of lead sulphate on lead (charged) electrodes (massive and porous) has been examined by the potential-step technique. The behaviour of the solid electrode conforms to control by nucleation and growth processes. The exact form of the process is potential-dependent and becomes two-dimensional at more positive potentials. The behaviour of the porous electrode can be interpreted in terms of well-established theory for porous materials assuming that the same crystallisation processes are observed as for the case of solid electrodes.

The impedance of the Ledanch cell. I. The treatment of experimental data and the behaviour of a typical undischarged cell

The impedance spectrum of an undischarged commercial Leclanché cell (Ever Ready type SP11) is presented in the forms of the Sluyters plot and the modified Randies plot. The decomposition of the experimental cell impedances into the component parts has been achieved using a computer. The decomposition process and the component processes representing the overall cell behaviour are described.

Fundamentals of lead-acid cells. IX. The effect of alloying with antimony on the electrochemical properties of solid lead

The electrochemistry of the Pb-Sb (5 wt %)/H2SO4 system has been followed using linear sweep voltammetry and the data compared with that from the Pb/H2SO4 system. Pre-cast lead rods aged for more than a month were used throughout in an effort to follow established industrial practice. The two areas covered are: (a) The rate of attainment of constant response of the cycled electrodes, and (b) the behaviour of stabilized electrodes. The results show that antimonial lead is corroded to a much greater extent than pure lead. Active material retention is also discussed in view of the differences between antimonial and pure lead.

The impedance of the alkaline zinc-mercuric oxide cell. I. Cell behaviour and interpretation of impedance spectra

The impedances of small (2400 mA h) alkaline Zn-HgO cells have been measured in the range 10 kHz-0.001 Hz at various states of charge from fully charged to fully discharged. The behaviour of the cell conforms to that expected for rate control by charge transfer at the zinc electrode and diffusion in solution. At low frequencies there is a relaxation in the diffusive circuit elements which ultimately results in a complete suppression of the capacitative component of the impedance at zero frequency. The low-frequency behaviour is analogous to convective diffusion and is due to the effective distance between the electrodes being small compared with the characteristic length (D/ω)1/2. The magnitude of the charge transfer resistance is the best measure of the state of charge.

Fundamentals of lead-acid cells. XVII. The a.c. impedance of lead dioxide formed in sulphuric acid on some lead alloys

The impedances of PbO2 formed on lead and some lead alloys have been measured over a wide range of potential. Conditions were chosen so that well-defined electrode states were obtained. Considerable differences were observed in the behaviour of alloys containing antimony and bismuth. The latter alloying ingredient appears to contribute some semiconducting properties to lead sulphate films formed on PbO2 by polarizing them at potentials negative to the reversible potential in sulphuric acid.

The impedance of the Leclanché cell. III. The impedance of the cell at different stages of discharge and state-of-charge indication by the impedance method

The prediction of the residual capacity of some primary electrochemical storage cells has been investigated using the impedance technique over an extensive frequency range. The frequency responses of Leclanché cells in various states of charge are presented and it is shown that the gross changes in impedance which result from discharging provide an adequate parameter for state-of-charge prediction. The component factors of the whole-cell impedance have been investigated and the contributions of the various cell components to the resultant frequency-response (resistive and reactive) spectrum identified. A knowledge of these contributions is important for the development of a suitable device for the rapid testing of cell quality since in principle the examination of each mode of failure of each component demands a separate test. In practice the understanding of the frequency response of the cell has enabled us to construct a relatively simple instrument which gives an adequate estimate of cell condition for ordnance applications. A block schematic diagram is presented and the operation of the device is described in principle.

The impedance of the alkaline zinc-manganese dioxide cell. I. Variation with state of charge

The impedance spectra of undischarged commercial alkaline zinc-manganese dioxide cells (Mallory, type MN 1500) have been measured. Newly produced cells have different impedance characteristics from ones stored for periods of time (up to one year). The difference introduced by the ageing process is interpreted as the effect of Hg on the zinc particle electrode. The impedance behaviour of the cells is dominated by the zinc negative electrode which behaves as a relatively simple charge transfer and diffusion process. The porous nature of the particulate electrode has relatively little effect on the behaviour of the zinc which behaves as quasiplanar.On discharging, the frequency spectrum changes as does the open-circuit potential, the latter due to the progressive change in composition of the positive electrode. The former changes as a consequence of the negative electrode reaction.

Fundamentals of lead-acid cells: Part XII. The reduction of lead sulphate

Abstract The reduction of lead sulphate grown anodically on planar and porous electrodes has been studied by a potentiostatic step technique. Both “planar” and “porous” electrodes behave in a similar manner and indicate that the electrode reduction reaction has a finite depth of penetration into the electrode. The kinetics of the formation of metallic lead on both electrodes appear to be instantaneous nucleation and two-dimensional growth processes with subsequent current limitations due to overlap and lead sulphate depletion. The current limitation processes are very complex and it has not been found possible to fit a satisfactory mathematical model.

Fundamentals of lead-acid cells. X. The formation of PbO2 on lead and antimonial lead

The electrochemical oxidation of films of lead sulphate formed by the cyclic sweep method has been examined using the potential step technique. Gross differences in behaviour are observed between the lead and antimonial lead alloy, the most important being the appearance of an additional peak in the transient response of the antimony alloy. An interpretation is given in terms of the structure of the grown lead sulphate film. The oxidation behaviour of the lead sulphate deposits depends on the length of time the electrode is held potentiostatically controlled in the lead sulphate region before being stepped to the PbO2 region. The results can be readily interpreted in terms of the density of nucleation sites and the formation of the PbO2phase by the two-dimensional growth of instantaneously nucleated layers.