Crystal structure, hydrogen absorbing and electrode properties of Sc-based Laves phase alloy (ScB2, B2 = Ni1.1Co0.2Mn0.5 Cr0.2) were studied by X-ray powder diffraction, pressure-composition isotherm and electrochemical measurements. Substitution effects of Zr and Y for Sc (Sc0.6Zr0.4B2 and Sc0.6Y0.4B2) on these properties were also studied. ScB2 and Sc0.6Zr0.4B2 contained a C15 Laves phase and a small amount of BCC phase. Sc0.6Y0.4B2 was composed of two kinds of C15 Laves phases with slightly different lattice parameters and orthorhombic phase with YNi-type structure. ScB2 absorbed a large amount of hydrogen up to a hydrogen to metal ratio (H/M, M: total metal) of 0.98 under hydrogen pressure of 4 MPa at 313 K. The hydrogen absorbing capacity was decreased by the substitution of Zr and Y for Sc in ScB2. The ScB2 anode showed a discharge capacity of more than 400 mAh g-1 at initial cycle, but the capacity rapidly decreased with increasing number of charge-discharge cycles. The substitution of Zr and Y for Sc in ScB2 led to the decrease of the discharge capacity, but improved the durability of the electrode.
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