Effects of fluorination of AB(2)-type alloys and of mixing with AB(5)-typealloys on the charge-discharge characteristics

The effects of fluorination (F-treatment) of AB(2)-type Laves-phase Zr0.9Ti 0.1V0.2Mn0.6Co0.1Ni1.1 (AB(2)) alloys and of mixing with untreated AB(5)-ty pe MmNi(3.68)Co(0.78)Mn(0.36)Al(0.28) (AB(5)) alloys on their charge-discha rge characteristics were investigated. The F-treatment of the AB(2) alloy g reatly increased initial activation rate and discharge capacity and slightl y improved high-rate dischargeability. The mixing of the F-treated AB(2) al loy with untreated AB(5) (< 25 mum) alloy decreased somewhat the maximum di scharge capacity compared to the fluorinated AB(2) alloy but it greatly imp roved the high-rate dischargeability. In particular, the high-rate discharg eability for the AB(2)(F)-AB(5) (< 25 mum) mixture positively deviated from the estimated values based on the maximum discharge capacity for both allo ys and their content, suggesting that the AB(5) alloy can work as a catalys t for dehydriding the AB(2) alloy hydride besides as a hydrogen reservoir; a synergistic effect appeared by the mixing. (C) 2001 Elsevier Science ltd. All rights reserved.