La_(0.8)Nd_(0.2)Ni_(3.55)Mn_(0.4)Al_(0.3)Co_(0.75)合金在充放电循环下的微结构研究

氢化物电极的循环寿命是ＭＨ－Ｎｉ电极能否实用化的主要性能指标之一，它主要取决于电极材料本身，如何提高材料在充放电循环过程中的使用寿命，仍然是人们普遍关注和有待深入研究的课题之一。本文通过Ｘ射线衍射分析、透射电镜直接观察以及电化学测量，研究了Ｌａ０．８Ｎｄ０．２（ＮｉＭｎＡｌＣｏ）５贮氢合金在充放电循环过程中显微结构的变化。研究结果表明：该合金电极的循环寿命不仅与合金成分有关，而且与合金的组织结构有关。电极循环寿命衰减的主要原因是合金在碱液中的氧化腐蚀，使负极活性物的有效部分减少；而合金的粉化，增加了粉末的表面积，加速了氧化腐蚀，因而表现出容量的衰减。电极循环寿命的衰退是合金在碱液中氧化腐蚀及合金微粉化的协同效应。

Study on microstructures of La0.8Nd0.2Ni3.55Co0.75Mn0.4Al0.3alloy during the charge-discharge cycle process

The cycle life of the metal hydride electrode which depending on electrode materials itself is one of the most important properties in nicked-metal hydride batteries. The performance depends on the mi- crostructure of the alloy composition. In this paper , the particle morphology which experienced different charge-discharge cycles was ohserved using transmission electron microscopy. It can be seen clearly that oxidation-pulverization-reoxidation phenomenon exists during charge-discharge cycle process. By using X- ray diffraction phase analysis and line broadening analysis , the particle pulverization of the hydride elec- trode was demonstrated further. We concluded that the degradation of cycle life of electrode was due to co- operation effect of oxidation corrosion and pulverization of the hydrogen storage alloy.