低钴储氢合金Ml0．9Mg0．1Ni3．4Co0．3Al0．3电化学性能研究

为了降低AB5犁储氢合金的成本，对低钴的Ml0．9Mg0．1Ni3．4Co0．3Al0．3合金的组织结构和性能进行了研究，并与工业储氢合金MmNi3.55Co0.75Mn0.4Al0.3进行了对比。实验结果表明：此低钴合金是由LaNi5主相和LaNi3第二相构成。它们的储氢晕（ω,％）分别为1．36％和1．37％，最大放电容量分别为320mAh／g和324mAh／g，循环稳定性为：300次充放电循环后，2种合金剩余容晕都是88％。但Ml0．9Mg0．1Ni3．4Co0．3Al0．3的高倍率放电性能明显优于MmNi3．55Co0．75Mn0．4Al0.3合金。主要原因是由于LaNi3第二相的乍成不仪提高了合金颗粒表面的电化学催化活性，而且提高了结构韧性从而抵消了低钴合金颗粒粉化的不利影响。

Study on the Electrochemical Properties of Low-Cobalt Ml0.9Mg0.1Ni3.4Co0.3Al0.3 Hydrogen Storage Alloy

For decreasing the cost of AB_5-type hydrogen storage alloys, a low-cobalt Ml_(0.9)Mg_(0.1)Ni_(3.4)Co_(0.3)Al(0.3) alloy was investigated by examining the alloy structure, phase composition and some properties. Its properties were compared with those of a commercial alloy MmNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3). The experiments' outcome shows that the low-cobalt alloy is composed of Mg-free LaNi_5 phase as matrix and Mg-contained LaNi3 phase as secondary phase. The hydrogen storage capacity (1.36wt% and 1.37wt% respectively), the greatest discharge capacity (320 mAh/g and 324 mAh/g respectively) and cycling stability (the residual capacity of two alloys is all 88% ) of Ml_(0.9)Mg_(3.4)Ni_(3.4)Co(0.3)Al_(0.3) are as good as those of MmNi_(3.55)Co(0.75)Mn(0.4)Al_(0.3). However, after the discharge current density exceeds 300 mA/g, the high-rate discharge abilities (HRD) of Ml_(0.9)Mg_(0.1)Ni_(3.4)Co_(0.3)Al_(0.3) are apparently better than those of MmNi_(3.55)Co_(0.75)Mn_(0.4)Al_(0.3).It is because there exists Mg-contained LaNi_3 phase as secondary phase which improves the electrochemical catalytic activity of alloy particles surface and the structure toughness of alloy particles.