Eletrode characteristics of MmNi5-type alloys for nickel-metal hydride batteries

Negative electrodes of the nickel-metal hydride battery were made from hydrogen storage alloy Mm0.9Ni3.9Mn0.4Co0.4Al0.3 modified by coating with nickel and mixing with cobalt powder. When the 10wt% cobalt powder was mixed with this alloy, the discharge capacity increased from 262mAh/g to 300mAh/g at 300K. When the alloy was coated with 11wt% nickel and mixed with 10wt% cobalt powder, the discharge capacity decay for a sealed cell (AA size, 1 Ah) was only about 4% after 200 cycles.