The effect of ZnO addition on the electrochemical properties of the LaNi3.55Mn0.4Al0.3Co0.2Fe0.55 electrode used in nickel–metal hydride batteries

"The original publication is available at www.springerlink.comInternational audienceThe studied electrochemical properties of the LaNi3.55Mn0.4Al0.3Co0.2Fe0.55 alloy showed a rather poor performance. To improve them, ZnO, a doping agent at different small amounts (0, 1, or 2.5 wt%), was added to this base alloy. Then, the prepared electrodes were investigated by various electrochemical techniques. The maximum discharge capacity, obtained after the activation procedure, increased with the rise in ZnO content. The activation, as well as the reversibility of the hydrogen absorption/desorption process, were significantly improved with the addition of ZnO. It was observed that the latter did not affect considerably the stability and the cycling lifetime if added to the electrodes. After 30 charge/discharge cycles, the diffusion coefficients were estimated to be 1.55 × 10−11, 1.30 × 10−11, and 6.05 × 10−11 cm2 s−1, respectively, for ZnO containing 0, 1, and 2.5 wt%. The ZnO catalyzed the kinetics of hydrogen absorption and desorption process thanks to capacity change before and after activation

Kinetic and thermodynamic studies of hydrogen storage alloys as negative electrode materials for Ni/MH batteries: a review

International audienceThis paper reviews the present performances ofintermetallic compound families as materials for negativeelectrodes of rechargeable Ni/MH batteries. The performanceof the metal-hydride electrode is determined by both thekinetics of the processes occurring at the metal/solutioninterface and the rate of hydrogen diffusion within the bulkof the alloy. Thermodynamic and electrochemical propertiesfor each hydride compound family will be reported. The stepsof hydrogen absorption/desorption such as charge-transferand hydrogen diffusion for evaluating the electrochemicalproperties of hydrogen storage alloys are discussed. Exchangecurrent density (I 0) and hydrogen diffusion coefficient (DH)are the two most important parameters for evaluating theelectrochemical properties of metal hydride electrode. Thevalues of the two parameters for a number of hydrogen storagealloys are compared. The relationship between alloycomposition and electrochemical properties is noted andevaluated

The effect of the temperature on the electrochemical properties of the hydrogen storage alloy for nickel-metal hydride accumulators

International audienceThe electrochemical properties of The LaNi3.55Mn0.4Al0.3Co0.75 alloy as a negative electrode material of a nickel-metal hydride accumulator have been investigated at different temperatures. The Activation of the alloy becomes faster with an increasing temperature. The enthalpy, the entropy and the apparent activation energy of the LaNi3.55Mn0.4Al0.3Co0.75Hx hydride formation are evaluated. The calculated results show that the enthalpy change, the entropy change and the activation energy are (29 kJ mol1), (26.5 JK1 mol1) and (24.6 kJ mol1), respectively. The corrosion current density increases with increasing the temperature and the corrosion potential becomes more positive and increases linearly with the temperature. This result is confirmed by the values of corrosion film resistance and the corrosion film capacitance determined through the electrochemical spectroscopy impedance modeling