| Zr-based AB2-type Laves phase hydrogen storage alloys are promising materials for use as a negative electrode material in MH/Ni batteries due to their higher discharge capacity, higher energy density and better cyclic durability in compared with commercially used AB5-type rare earth based alloys. However, Zr-based Laves phase alloy electrodes exhibit in general very slow activation behavior, poor high-rate dischargeability and low-temperature electrochemical characteristics. For improving electrode characteristics of Zr-based Laves phase alloy electrodes, the effects of the various stoichiometric ratios, the additive elements and the formation of composite alloy with AB5-type rare earth based alloys on the microstructure and electrochemical characteristics of AB2-type Laves phase alloys have been studied, and the significant results are achieved in this paper.The crystal structure, the phase composition and the electrochemical characteristics of Zr0.9Ti0.1(Ni0.55Mn0.35V0.10)2X (x=0.90, 0.95, 1.00, 1.05) alloys were investigated by means of XRD, SEM, EDS and electrochemical measurements. It was shown that all alloys are multiphase with C15 Laves phase as a main phase along with C14 phase and some Zr-Ni phases, and the amounts of the C14 phase and Zr-Ni phases in the four alloys increases with decreasing x. The results indicated that the various stoichiometric ratios have great effects on the electrochemical characteristics for AB2X (x=0.90, 0.95, 1.00, 1.05) alloys, the maximum discharge capacity increases with increasing x, and discharge rate capability increases with decreasing x. The C14 phase and Zr-Ni phases seem to improve discharge rate capability of the alloys.For examining effects of the additive elements on the characteristics of AB2-type Laves phase alloys Zr0.9Ti0.1Ni1.1Mn0.7V0.3M0.1 (M= None,Ni,Mn,V,Co,Cr,Al,Fe,Mo,Si,C,Zn,Cuå’ŒB), the phase structure, high rate dischargeability, charge retention, cyclability, high-temperature and low-temperature dischargeability of the alloys were investigated. The XRD results showed that all alloys consisted of a large amount of the hexagonal C14 Laves phase along with a small level of the cubic C15 Laves phase and some non-Laves phases. The addition of V and Mn increased the discharge capacity of the AB2 alloy electrodes. The high rate dischargeability and low-temperature dischargeability of the alloy was dramatically increased with B or Mn addition, and the Zr0.9Ti0.1Ni1.1Mn0.7V0.3B0.1 exhibited the discharge capacity of 200mAh/g at discharge current of 1320 mA.g-1. It was found that a small addition of Al,C,Si and Co greatly improved the cycle life of the AB2 alloy electrodes, but addition of Mn,V,Ni,Fe,Cu,Mo and B decreased the cyclability in some extent, especially additive Mn resulted in decreasing of the cyclability drastically, and addition of Si,Mo,V,Cr and Al was useful to improve self-discharge characteristics of the AB2 alloy. Considerable improvement in the high-temperature dischargeability was observed by addition of Si,Cr and V, and the discharge capacity was up to 210mAh/g at 338K for Zr0.9Ti0.1Ni1.1Mn0.7V0.3Si0.1 alloy electrode. Si addition greatly improved high temperature electrochemical characteristics of non-stoichiometric Zr0.9Ti0.1Ni1.0Mn0.7V0.3Six (x=0.05, 0.10, 0.15, 0.20) alloys. For example,the discharge capacity of Zr0.9Ti0.1Ni1.0Mn0.7V0.3Si0.10 alloy reached 249mAh/g, and the charge retention was 94.20% for 24h, and the capacity retention for 300 charge/discharge cycles was 45.17% at 338k. At high temperature, the main cause of further decreasing of cyclability may be due to the corrosion and the oxidizing deterioration on alloy surface.On the basis of the experimental factors that the discharge capacity and cycle life of AB2-type Laves phase alloy is superior to AB5-type rare earth alloy, but the activation and high rate dischargeability of AB5 alloy is superior to AB2-type Laves phase alloy, we proposed a new idea to combine the advantages of them by preparing a composite alloy electrode materials deri...
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