TRANSMISSION ELECTRON MICROSCOPY STUDIES ON DEGRADATION OF ALLOY ELECTRODE IN NICKEL-METAL HYDRIDE BATTERY

储氢合金已在二次电池中得到应用。近年来，镍金属氢化物电池引起了人们的广泛关注。研究了LaNi5及其相关化合物的吸氢特性。有人认为，位错、反相界和结构无序等缺陷是由氢反应产生的，但尚未得到证实。用透射电子显微镜研究了吸氢对镁镍合金组织的影响。对快淬态的镁镍合金进行了退火热处理和脱水处理。用聚焦离子束(FIB)技术制备了透射电子显微镜样品。为了弄清影响电极性能的位错的性质，用透射电子显微镜观察了LaNi5合金的形变组织。LaNi5合金在高于850ﾟC的温度下可以变形，变形后引入大量的位错和亚晶。合金电极中的位错被认为是氢的捕获点，因此高密度的位错会影响电极的退化。

The hydrogen storage alloys have been applied to secondary batteries. Recently the nickel-metal hydride batteries catch much attention. The hydrogen absorption characterics of LaNi_5 and related compounds have been investigated. It has been suggested, but not proven, that defects such as dislocation, anti-phase boundary and structural disorder are produced by hydrogen reaction.The influence of hydrogen absorption on the microstructure of Mg-Ni alloys has been investigated by transmission electron microscopy (TEM). Rapidly-quenched Mg-Ni alloys were annealed and then dehydrided. TEM specimens were fabricated by focused ion beam (FIB) technique. Many cracks are evident in the specimen after 5 hydriding-dehydriding cycles.Deformation structures of LaNi_5 alloy have been observed using TEM in order to clarify the nature of dislocations which affect the degradation of the alloy electrode. LaNI_5 alloy is able to deform at temperatures higher than 850ﾟC.Many dislocations and subgrains are introduced after deformation. Dislocations in the alloy electrode are thought to be the trapped site of hydrogen, therefore high density of dislocation may affect the degradation of electrode.