Nickel/metal hydride batteries using microencapsulated hydrogen storage alloy

Abstract Fine particles of M m Ni 5 (M m : abbreviation for mischmetal) multicomponent hydrogen storage alloys were encapsulated with a thin layer of nickel about 0.5 μm thick using a special chemical plating method. With the alloy as an anode material, metal hydride electrodes and sealed nickel/metal hydride ( Ni MH ) batteries of AA size were made. The electrode has a higher discharge capacity and a longer cycle life than that using the bare (uncoated) alloy. A battery discharge capacity of 1200 mAh is obtained, which is equivalent to 60 Wh kg −1 (180 Wh 1 −1 ). After 1000 complete charge-discharge cycles, the battery capacity is only reduced by 5%. SEM analysis, X-ray diffraction patterns and corrosion measurement are used to show how the microencapsulation of the alloy is effective in improving the performance of the battery.