摘要
合金结构研究表明，La2-xMxNi7（x=0．3-0．8）主要由Ce2Ni7，Gd2C07，PuNi3型物相组成。合金中Mg含量对合金相结构有着重要影响，主相的晶胞参数随Mg含量（x）的增加呈线性减小，合金的吸放氢平台也随之升高。电化学测试表明，随合金中Mg含量的增加，合金电极的放电容量先增大后减小，合金电极的循环稳定性呈恶化趋势，La1.4M0.6Ni7合金电极具有最高的电化学放电容量（378mAh·g^-1），La1.6M04Ni7合金电极具有最佳的循环稳定性（S270=81％）。合金电极的高倍率放电性能（HRD）随Mg含量的增加而增大。当合金中Mg含量较低时（x≤0．5），合金电极反应速度控制步骤为氢在合金体相中的扩散；当Mg含量较高时（x≥0．5），合金电极反应速度控制步骤转变为电极表面的电荷转移。
Investigation of alloy structure shows that La2-xMgxNi7（x = 0.3 - 0.8） alloys are mainly composed of Ce2NiT-type, Gd2Co7-type and PuNi3-type phase. The influence of Mg content in alloys on the phase structure is great, resulting in a linear decrease of the unit cell parameters of main phases and increase of hydrogen absorption/desorption plateau as Mg content increases. Electrochemical measurements show that as the Mg content increases, the discharge capacity of alloy electrodes first increases and then decreases. The cyclic stability presents a deteriorative trend,Lal.4Mg0.6 NiT alloy electrode exhibits the maximum electrochemical discharge capacity （378 mAh· g^- 1 ）, and the La1.6Mg0.4Ni7 alloy electrode shows the best cyclic stability （S270 = 81%）. The high rate dischargeability increases with the increase of Mg content. When the Mg content （x） is lower than 0.5, the rate-determining step of the electrode reaction is the diffusion of hydrogen in bulk. When the Mg content （x） is higher than O. 5, the control progress of the electrode reaction is converted to charge-transfer on the alloy surface.
出处
《中国稀土学报》
CAS
CSCD
北大核心
2006年第5期592-598,共7页
Journal of the Chinese Society of Rare Earths
基金
国家自然科学基金资助项目(50171021)
关键词
贮氢合金
A2B7型
P-C-T曲线
电化学性能
稀土
hydrogen storage alloy
A2BT-type
P-C-T isotherm
electrochemical properties
rare earths
