By means of linear polarization, Tafel polarization and galvanostatic discharge methods, the kinetic properties of MlNi4.3-XCoXAl0.7 (X=0.0, 0.3, 0.5, 0.7, 0.9, 1.1 and 1.3) hydride electrodes, including high rate dischargeability HRD, exchange current density I0, limiting current density IL, the symmetry factor β, and the apparent diffusion coecient of hydrogen in the a phase Da have been studied systematically. The results show that the HRD of the electrode with high Co content is lower than that with low Co content. For the MlNi4.3-XCoXA10.7 hydride electrodes, with Co content increasing from 0.0 to 1.3, the values of 10, IL, β and Da decreased from 395 to 33mA/g, 2263 to 308 mA/g, 0.85 to 0.43, 1.42×10-10 to 2.1×10-11cm2/s, respectively. In order to calculate the electrochemical polarization ηe and concentration polarization ηc based on anodic polarization curve, the experimental anodic polarization curve should be divided into three regions to discuss according to discharge current density Id, namely, Id<IP, IP<Id<If, and Id>If. The calculation of ηe and ηc should use di€erent formula in different regions. When discharge current density Id is smaller than Ip, the traditional equation used to calculate the electrochemical overpotential can not be used, when Ip is between Ip and If, both equations used to calculate the electrochemical overpotential and concentration overpotential can be used, and when Id is larger than If, because there exists absorption and adsorption of hydrogen, the traditional equation used to calculate concentration overpotential can not be used in the system of hydride electrodes.

This paper describes the effects of treating the alloy powder of an electrode with 6 MKOH solution containingy M KBH4 (y=0.0, 0.005, 0.01, 0.02 and 0.03) on the kinetic properties of the electrode, including high rate dischargeablilty HRD, exchange current density I0, symmetry factor β, limiting current density IL, diffusion coeffcient of hydrogen in the a-phase Da, and electrochemical polarization ηe and concentration polarization ηc. The results show that the kinetic parameters HRD, 10, IL and Daincrease markedly with the increase in the concentration of KBH4, the ηe and ηc decrease rapidly with increasing concentration of KBH4, but the symmetry factor β does not change.

In this paper, the influence of heat treatment on the electrochemical properties of La0.67Mg0.33Ni2.5Co0.5 alloy electrodes has been studied. The results show that, after heat treatment, the electrochemical properties including the discharge capacity, width of discharge plateau and cyclic stability have been improved markedly. The discharge capacity of the alloy annealed at 1123K is the highest and the cycle life of the alloy annealed at 1223K is the longest, respectively. In addition, the exchange current density I0 and the limiting current density IL of the alloy electrode both increase when annealed at 1123K and then decrease when the annealing temperature increases to 122 K.

In this paper, the degradation mechanism of the Ti-V-based multiphase hydrogen storage electrode alloys (Ti0.8Zr0.2) (V0.533Mn0.107Cr0.16-Ni0.2)x (x=2, 4, 6) during electrochemical cycling has been studied systematically by using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and electrochemical impedance spectroscopy (EIS). The reasons for the improvement in cycling stability of the electrodes with increasing x have also been discussed. The results show that the capacity degradation of the electrode is mainly caused by the following two reasons. The first one is the pulverization of the alloy particles during cycling, which leads to an increase in contact resistance and decrease in electric conductivity between alloy particles. The second one is the oxidation and corrosion/dissolution of the active alloy constituents in alkaline electrolyte during cycling, which leads to an increase in surface reaction resistance and decrease in discharge capacity of the alloy electrodes. With increasing x, the portion of stable and inactive hydride formed in the alloy during cycling decreases, and the pulverization resistance

In this paper, the structural and electrochemical properties of La0.7Mg0.3 (Ni0.85Co0.15)x (x=2.5, 3.0, 3.5, 4.0, 4.5, 5.0) hydrogen storage alloy electrodes were studied systematically. X-ray diffraction Rietveld analyses show that all these alloys consist of a (La, Mg) Ni3 phase with the PuNi3-type rhombohedral structure and a LaNi5 phase with the CaCu5-type hexagonal structure. The (La, Mg) Ni3 phase abundance first increases to a high percentage (～75%) and then decreases with increasing x. In contrast, the LaNi5-phase abundance first remains low and almost unchanged and then increases to a high percentage (～70%) with increasing x. The pressure-composition isotherms shows that for each isotherm the plateau region widens and the plateau pressure is maintained almost unchanged when x increases from 2.5 to 3.5. However, as x increases further, the plateau region is shortened and becomes flatter, and the plateau pressure increases with x. Electrochemical studies indicate that all important electrochemical properties, including the maximum discharge capacity, the high rate dischargeability, the exchange current density, and the limiting current density of the alloy electrodes increase as x increases from 2.5 to 3.5 and then decrease when x increases further from 3.5 to 4.5.