Al替代Ni对A2B7型贮氢电极合金性能的影响

用冷坩埚磁悬浮熔炼方法制备La0.7Mg0.3（Ni0.85-xCo0.15Alx）3.4贮氢电极合金，采用XRD、三电极体系及SEM研究相结构、电化学性能及电极的表面状态。Rietveld法全谱拟合分析表明，该体系合金为多相结构，主相为ce2Ni7型六方相，还包括CaCu5型六方相、PuNi3型菱方相、MgCu2型立方相及BCr型正交相。Al元素为ce2Ni7型主相的有利形成元素，且Al替代Ni后，各组成相的晶胞体积均增加。P-C-T曲线显示随着Al替代量X的增加，合金放氢平台的平台区域变窄，平台压力降低，平台特性变差。电化学性能测试表明，随着X增加合金电极的最大放电容量降低，高倍率放电性能降低，循环稳定性明显提高。

Effects of Substitution of A! for Ni on Properties of A2B7-Type Hydrogen Storage Electrode Alloys

The La0.7Mg0.3(Ni0.85-xCo0.15Alx)3.4 hydrogen storage electrode alloys were prepared by cold crucible melting under argon gas atmosphere. The phase structure of these alloys and the electrochemical properties and surface of corresponding electrodes were investigated by means of XRD and tri-electrode test system and SEM. Rietveld analyses show that all these alloys consist of hexagonal Ce2Ni7-type main-phase,hexagonal CaCu5-type phase,rhombohedral PuNi3-type phase,cubic MgCu2-type Laves-phase and orthorhombic BCr-type phase. The Ce2Ni7-type main-phase content and the cell volume of all these phases increase with increasing of x. P-C isotherms show that hydrogen-desorption plateau region narrows,and the plateau pressure decreases and the plateau becomes steeper with increasing of x. The electrochemical results show that maximum discharge capacity and high-rate dischargeability decrease,cyclic stability is improved markedly with increasing of x.