Elaboration and characterization of magnesium-substituted La5Ni19 hydride forming alloys as active materials for negative electrode in Ni-MH battery
Elaboration and characterization of magnesium-substituted La5Ni19 hydride forming alloys as active materials for negative electrode in Ni-MH battery
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DOI：
10.1016/j.electacta.2008.09.069
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发表时间：
2009-02
影响因子：
6.6
通讯作者：
Amélie Férey;F. Cuevas;M. Latroche;B. Knosp;P. Bernard
中科院分区：
文献类型：
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作者：
Amélie Férey;F. Cuevas;M. Latroche;B. Knosp;P. Bernard
测定了吸氢化合物La5Ni19和La4MgNi19的晶体结构、热力学和电化学性质。X射线衍射和微探针分析表明，无镁二元化合物只有一个六方相(p63/MMC)，而La4MgNi19只有一个成分，而有两种不同的晶体结构，即六方相(p63/MMC)和三方相(R-3m)。每个相可以描述为n[A2B4]/m[AB5]亚单位沿c轴的堆积，其中n=1，m=3，A=La，Mg；B=Ni。根据堆积顺序的不同，可以得到六方相或三方相。测量了这些化合物在碱性介质中的吸氢热力学性能(容量和平衡压力)和电化学性能(循环行为)，并比较了这些化合物加镁和不加镁的情况。结果表明，不含镁化合物的可逆氢容量远低于含镁化合物。然而，尽管容量较大，但后一种化合物在循环寿命方面仍有待优化。
The crystallographic structure as well as the thermodynamic and electrochemical properties of the hydrogen absorbing compounds La5Ni19and La4MgNi19have been determined. X-ray diffraction and microprobe analysis have shown the presence of a single hexagonal (P63/mmc) phase for the Mg-free binary compound whereas only one composition but two different crystallographic structures, hexagonal (P63/mmc) and rhombohedral (R-3m), are observed for La4MgNi19. Each phase can be described as the stacking along the c-axis of n[A2B4]/m[AB5] sub-units with n=1 and m=3 and A=La, Mg; B=Ni. Depending on the stacking sequence, either the hexagonal or the rhombohedral phase is obtained. Thermodynamic properties toward hydrogen uptake (capacity and equilibrium pressure) and electrochemical properties (cycling behavior) in alkaline medium have been measured and are compared for these compounds with and without magnesium. It is observed that the Mg-free compound exhibits a much lower reversible hydrogen capacity than the Mg-containing one. However, despite larger capacity, this latter compound remains to be optimized in term of cycle life.