Metal Hydride Battery Electrodes for High Current Density

近年来，一些类型的金属氢化物电池已经实现了商业化。目前，要制造出性能更完善的金属氢化物电池，实现高电流密度的快速充放电，仍有许多材料问题需要解决。许多研究都指出在稀土-镍基合金中用各种元素取代稀土和镍的重要性。然而，每个取代元素在电极中的作用还不是很清楚。这主要是因为电极表面的电化学反应复杂，不易研究。在本工作中，我们试图对钴取代Ni在LaNi_5氢化动力学中的作用进行基础性研究。研究了LaNi_<2.5>Co_<2.5>合金在氢气气氛和KOH溶液中的活化行为。样品表面在6N-KOH溶液中353 K加热3小时预处理。Co取代有效地提高了初始活化，这可能是由于形成了相对稳定的氧化表面。LaNi_<2.5>Co_<2.5>合金也没有明显的粉化现象。钴的存在可以诱导相对较高的氧化物-金属界面，从而抑制循环过程中裂纹的产生。6N-KOH溶液在353 K下预处理后，LaNi_<2.5>Co_<2.5>合金的初始活化和后续循环氢化的潜伏期均缩短。

Recently, some types of Metal Hydride batteries have been commercialized. At present, there are still many material problems to be solved for manufacturing more improved Metal Hydride batteries which enable the rapid charge-discharge with high current densities. Many works point out the importance of substitutions of various elements for rare earths and Ni in the rare earth - Ni based alloys. However, the role of each substitutive elements in the electrodes is not well understood. This is mainly because of the complicated electrochemical reactions on the electrode surface which cannot be readily investigated.In this work, we tried to make an fundamental research to understand the roles of the cobalt substitution for Ni in hydriding kinetics of LaNi_5. Activation behaviors of LaNi_<2.5>Co_<2.5> alloys in hydrogen gas atmosphere and KOH solution were investigated. The samples surface were pretreated by heating in a 6N-KOH solution at 353 K for 3 hours.Co substitution shows an effective improvement in the initial activations, which may be explained by the formation of relatively stable oxidized surface. The LaNi_<2.5>Co_<2.5> alloy exhibits also no significant pulverization. The presence of cobalt may induce relatively high coherent oxide-metal interfaces which inhibits the generation of cracks in the cycling. After pretreatment of 6N-KOH solution at 353 K, LaNi_<2.5>Co_<2.5> alloy showed shortened incubation periods for both the initial activations and subsequent cyclic hydridings.