Charge and discharge characteristics of sintered Mg2Ni

The effects of sample preparation of a Mg2Ni anode for a nickel/metal hydri de battery were studied with an open electrochemical cell. The discharge ca pacity of sintered Mg2Ni increased initially with the charge/discharge cycl es. The cycle life (CL) for sintered samples was much greater than that of un-sintered samples, and the largest CL appeared at a sintering temperature of 550 degrees C. It was also observed that slight pre-oxidation of the sa mple powder was effective in improving the CL. Those effects were examined through the changes in the specific surface are a and the chemical composition. The sample sintered at 550 degrees C had th e largest specific surface area, and the segregation of Mg over the outside layer of samples was confirmed for those sintered at temperatures higher t han 550 degrees C. The degradation after charge/discharge cycling was inves tigated with X-ray diffraction and scanning electron microscopy. The XRD pa ttern showed a new phase of Mg(OH)(2), besides the phase of Mg2Ni, after ch arge/discharge Cycling. This indicates that the formation of Mg(OH)(2) on t he outside layer of the samples contributes to the degradation of the anode performance. (C) 1999 Elsevier Science S.A. All rights reserved.