热处理对La-Mg-Ni系贮氢电极合金性能的影响(Ⅱ)贮氢及电化学性能

Effect of Heat Treatment on the Properties of La-Mg-Ni-System Hydrogen Storage Electrode Alloys (Ⅱ) Hydrogen Storage and Electrochemical Properties

用冷坩埚磁悬浮熔炼方法制备铸态La0.7Mg0.3(Ni0.81Co0.15Al0.04)3.4贮氢电极合金,并分别在1073、1173和1273K温度下热处理8h得到不同的热处理态合金,采用ICP-AES、三电极体系、显微硬度测试、XRD、SEM及EDS等研究合金的Mg含量、电化学性能、显微硬度及相应电极的表面状态。ICP-AES分析表明,合金的Mg含量随着热处理温度的升高而降低。P-C-T曲线显示随着热处理温度的升高,合金放氢平台的平台区域先变宽后变窄,平台压力先降低后升高再降低,平台先变得平坦后倾斜。电化学性能测试表明,合金电极的最大放电容量先增加后减小,循环稳定性先提高后有所降低;其中1173K,8h热处理态La0.7Mg0.3(Ni0.81Co0.15Al0.04)3.4合金具有良好的综合电化学性能,可以用作高容量电极材料。

The as-cast La0.7Mg0.3（Ni0.81Co0.15Al0.04）3.4 hydrogen storage electrode alloy has been prepared by cold crucible melting, and then heat-treated at 1073, 1173 and 1273 K for 8 h under argon atmosphere. The magnesium content and microhardness of alloys and the electrochemical properties and the surface condition of corresponding electrodes have been investigated by means of ICP-AES, tri-electrode system, microhardness, XRD, SEM and EDS. The ICP-AES analysis shows that the magnesium content of alloys decreases with increasing the heat treatment temperature. The pressure composition isotherms （P-C-T） curves show that the hydrogen-desorption plateau region broadens first then narrows, and the plateau pressure increases first then decreases, the plateau flattens first then bevels. The electrochemical results show that the maximum discharge capacity and the cyclic stability both are first improved, and then reduced. The La0.7Mg0.3（Ni0.81Co0.15Al0.04）3.4 alloy annealed at 1173 K for 8 h can be used as high capacity electrode materials due to the good overall electrochemical properties.