Characteristics of surface-modified metal hydride electrode with flake Ni by the ball-milling process

In order to improve the electrochemical cyclic durability of the Ti-based hydrogen storage alloy electrode, the ball-milling process was applied to the Ti-based alloy using flake Ni as a surface modifier. Flake Ni powder is a very useful material to modify the surface of metal hydrides. While the as-cast Ti-based alloy electrode is completely degraded within ten cycles, the ball-milled Ti-base alloy electrode using flake Ni as a surface modifier shows only 8% of capacity decay even after 180 cycles. It is also noticeable that the ball-milled alloy electrode shows just a little decreased discharge capacity (429 mAh/g) by ball-milling with flake Ni powder. These results are closely related to the higher strain and higher coverage area of flake Ni powder. The residual strain of flake Ni powder can promote the diffusion reaction in the impact event of ball-milling, Consequently, the flake Ni as a new surface modifier can modify the alloy surface without changing the bulk properties of the alloy, resulting in an effective surface coating within a shorter ball-milling time. (C) 2002 Published by Elsevier Science B.V.