Charge and discharge characteristics of sintered Mg2Ni
Journal of Alloys and Compounds, 293-295 (1999) 626-631
Kuniaki Watanabe, Wei Min Shu, Kenzo Mizukami, Kohji Kobayashi, Yuji Hatano, Shotaro Morozumi
Hydrogen Isotope Research Center, Toyama University, Gofuku 3190, Toyama 930-8555, Japan
Abstract
The effects of sample preparation of a Mg2Ni anode for a nickel/metal
hydride battery were studied with an open electrochemical cell.
The discharge capacity of sintered Mg2Ni increased initially with the charge/discharge cycles.
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℃.
It was also observed that slight pre-oxidation of the sample powder was effective in improving the CL.
Those effects were examined through the changes in the specific surface area and
the chemical composition. The sample sintered at 550℃ had the largest specific surface area,
and the segregation of Mg over the outside layer of samples was confirmed for those sintered at temperature
higher than 550℃.
The degradation after charge/discharge cycling was investigated with X-ray diffraction and scanning electron microscopy.
The XRD pattern showed a new phase of Mg(OH)2, besides the phase of Mg2Ni,
after charge/discharge cycling. This indicates that the formation of Mg(OH)2 on the outside
layer of the samples contributes to the degradation of the anode performance.
Keywords: Hydride; Battery; Mg2Ni; Cycle-life; Pretreatment