AC impedance behaviour and state-of-charge dependence of Zr<SUB>0.5</SUB> Ti<SUB>0.5</SUB>V<SUB>0.6</SUB>Cr<SUB>0.2</SUB>Ni<SUB>1.2</SUB> metal-hydride electrodes

Metal-hydride electrodes made of an AB2 alloy of the composition Zr0.5 Ti0.5 V0.6 Cr0.2 Ni1.2 are studied for AC impedance behaviour at several of their state-of-charge values. Impedance data at any state-of-chargecomprisetwo RC-time constants and accordingly are analysed by using a nonlinear-least-square-fitting procedure. Resistance of the electrode and frequency maximum (f∗) of the lowfrequency semicircle are found useful for predicting state-of-charge of the metalhydride electrodes

Electrochemical impedance studies of capacity fading of electrodeposited ZnO conversion anodes in Li-ion battery

Electrodeposited ZnO coatings suffer severe capacity fading when used as conversion anodes in sealed Li cells. Capacity fading is attributed to (i) the large charge transfer resistance, Rct (300-700 Ω) and (ii) the low Li+ ion diffusion coefficient, D+Li (10-15 to 10-13 cm2 s-1). The measured value of Rct is nearly 10 times higher and D+Li 10-100 times lower than the corresponding values for Cu2O, which delivers a stable reversible capacity. © Indian Academy of Sciences

On the performance of stabilized α-nickel hydroxide as a nickel-positive electrode in alkaline storage batteries

The internal resistance of a stabilized α-nickel hydroxide electrode is found to be lower than that of a β-nickel hydroxide electrode as shown from studies of the open-circuit potential-time transients at all states-of-charge. Nevertheless, the self-discharge rates of the former is higher. Gasometric studies reveal that the charging efficiency of the α-nickel hydroxide electrode is higher than that of the β-nickel hydroxide electrode. © 1995

An electrochemically impregnated sintered-nickel electrode

An electrochemically impregnated sintered-nickel porous electrode with a capacity of 225 ± 10 mAh per g of active material has been developed. This capacity is comparable with any state-of-the-art nickel hydroxide electrode reported in the literature, such as the stabilized α-nickel hydroxides that contain aluminium, iron and other trivalent cations. A technical update on various types of nickel positive electrodes is given

Electrochemically Impregnated Aluminum-Stabilized α-Nickel Hydroxide Electrodes

Nickel-positive electrodes obtained by electrochemical impregnation of aluminum-substituted α-nickel hydroxide are found to deliver a reversible discharge capacity of ca. 450 mAh/g. This is much higher than the capacity of β-nickel hydroxide electrodes 200 mAh/g: this work; 225 mAh/g: Dixit et al., J. Power Sources, 63, 167 (1996) prepared under identical conditions and pasted electrodes comprising cobalt-doped nickel hydroxide 345 mAh/g: Faure et al., J. Power Sources, 36, 497 (1991). These observations suggest that the theoretical target-capacity for high-performance nickel-positive electrodes must be revised from the currently accepted value of 289 mAh/g (1e exchange) to 491 mAh/g 1.7e exchange: Corrigan and Knight, J. Electrochem. Soc., 136, 613 (1989). © 1999 The Electrochemical Society. S1099-0062(98)08-044-4. All rights reserved

Porous flower-like α-Fe2O3 nanostructure: A high performance anode material for lithium-ion batteries

Porous flower-like α-Fe2O3 nanostructures have been synthesized by ethylene glycol mediated iron alkoxide as an intermediate and studied as an anode material of Li-ion battery. The iron alkoxide precursor is heated at different temperatures from 300 to 700 °C. The α-Fe2O3 samples possess porosity and high surface area. There is a decrease in pore volume as well as surface area by increasing the preparation temperature. The reversible cycling properties of the α-Fe2O3 nanostructures have been evaluated by cyclic voltammetry, galvanostatic charge discharge cycling, and galvanostatic intermittent titration measurements at ambient temperature. The initial discharge capacity values of 1063, 1168, 1183, 1152 and 968 mAh g−1 at a specific current of 50 mA g−1 are obtained for the samples prepared at 300, 400, 500, 600 and 700 °C, respectively. The samples prepared at 500 and 600 °C exhibit good cycling performance with high rate capability. The high rate capacity is attributed to porous nature of the materials. As the iron oxides are inexpensive and environmental friendly, the α-Fe2O3 has potential application as anode material for rechargeable Li batteries

Electrochemical impedance studies of a decade-aged magnesium/manganese dioxide primary cell

A Mg/MnO2 primary cell yields specific energy higher than a conventional Zn/MnO2 cell. Additionally, the shelf life of the Mg/MnO2 cell is extremely high. These cells, which were more than a decade old, were investigated for their discharge capacity, delay-time behaviour and impedance characteristics. The values of discharge capacity and the delay-time of an aged Mg/MnO2 cell were comparable to those of a fresh cell. The voltage dip on initiation of a galvanostatic current, however, was rather large. This was attributed to the presence of a thick, and highly resistive, surface passive film on theMg anode. The complex plane electrochemical impedance spectrum of a partially discharged cell consisted of two semicircles whose sizes decreased with decrease of state-of-charge of the cell. The a.c. frequency corresponding to the maximum value of the imaginary part of the high frequency semicircle was shown to be a useful parameter for estimation of the state-of-charge of the cell. The resistance parameters of a partially discharged Mg/MnO2 cell increased linearly with open circuit ageing time. This feature was attributed to growth of a passive surface layer on the Mg anode

Potentiodynamic behaviour of β-lead dioxide in neutral media at positive potentials

The behaviour of the PbO2 electrode in NaNO3, Na2SO4 NaClO4 and NaCl in the pH range 3.0–10.5 has been studied by cyclic voltammetry. When the electrode is cycled between 0.30 and 1.90 V, a large cathodic current peak appears in the negative scan; in the subsequent cycle, two anodic peaks appear. The addition of H2O2 at low concentrations to the electrolyte also results in two anodic peaks at the same potentials. A number of possible explanations for the appearance of the cathodic peak, and a mechanism for the oxidation of PbO to PbO2 through Pb3O4 corresponding to the two anodic peaks, are proposed