Application of flake metal as a surface modifier for the hydrogen absorbing intermetallic electrode of an Ni–MH rechargeable battery

In order to improve the electrochemical cyclic durability of the Ti-based hydrogen storage alloy electrode, a ball-milling process is applied to the Ti-based alloy using the Ni flake as a surface modifier. Ni flake powders are a very useful material to modify the surface of metal hydrides. While the as-cast Ti-base alloy electrode was completely degraded within ten cycles, the ball-milled Ti-base alloy electrode using Ni flakes as a surface modifier showed 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−1) by modifying with Ni flake powders. These results are closely related with the higher strain and higher surface area of Ni flake powder. The residual strain of Ni flake powder can promote the diffusion reaction in the impact event of ball-milling. Consequently, the Ni flakes 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.