快速凝固MlNi_(4.0)Co_(0.2)Mn_(0.40)Al_(0.30)Cu_(0.10)低Co贮氢合金的相结构和电化学性能

Phase Structure and Electrochemical Properties of the Rapidly Solidified Low Co-containing MlNi_(4.0)Co_(0.2)Mn_(0.40)Al_(0.30)Cu_(0.10) Hydrogen Storage Alloys

系统研究了单辊快淬快速凝固处理对低Co贮氢合金MlNi4.0Co0.2Mn0.40Al0.30Cu0.10的相结构和电化学性能的影响。XRD分析表明,铸态和快凝合金均为单相CaCu5型结构,但快凝合金的成分和结构均匀性得到明显改善,并具有较低的吸氢体积膨胀率(ΔV/V)。电化学测试表明,快速凝固处理后合金的活化性能不变,循环稳定性得到显著改善,但其放电容量和高倍率放电性能有所降低。研究发现,快速凝固低Co合金循环稳定性能的改善主要归结于快凝合金具有较低的吸氢体积膨胀率和较好的成分均匀性,而快凝合金电极的电催化活性以及氢在合金中的扩散速率较铸态合金有所减小是导致其高倍率放电性能降低的主要原因。

The phase structure and electrochemical properties of the low Co-containing MlNi4.0Co0.2Mn0.40Al0.30Cu0.10 hydrogen storage electrode alloys prepared by both conventional casting and melt-spinning processes at different cooling rate were studied comparatively. XRD analyses indicated that both as-cast and melt-spun alloys were of the CaCu5-type structure single phase, but the crystallizability and composition homogeneity of the melt-spun alloys were improved. The electrochemical tests indicated that the melt-spun alloys showed a good activation property and much better cycling stability, but a lower discharge capacity and high-rate discharge ability in comparison with the as-cast alloy. It is found that the improved cycling stability of the melt-spun alloy is mainly due to their lower volume expansion on hydride and more uniform composition, and the decrease in both the electro catalytic activity and the diffusion rate of hydrogen in alloy bulk is the main reason for their relatively lower high-rate discharge ability.