Mg_2Ni系储氢合金电化学性能的研究

Study on Electrochemical Performances of Mg_2Ni System Hydrogen Storage Alloys

用固态扩散和机械球磨法制备出纳米级Mg2 Ni和Mg1 .7Al0 .3 Ni储氢合金 ,其电化学性能超过用传统方法制备的合金。充放电测试表明 :该合金放电电压平台 (电压超过 1 2V)较高 ;在 2 0 0mA/g放电电流密度下 ,合金充放电循环 50次 ,容量仍保持在 2 0 0mAh/g以上。X射线衍射分析表明 :随着球磨时间延长 ,衍射峰的宽化程度变大 ,强度逐渐减弱 ,1 2h后变化减缓。这是由于晶粒尺寸变小 ,缺陷及应力密度增加之故。合金电化学性质的改善与合金在机械研磨中的微结构变化有关 ,并且合金组成中铝部分取代镁对于延长合金的循环寿命有至关重要的作用。

The methods of solid state diffusion and mechanical grinding were used to prepare nanoscaled Mg 2Ni system hydrogen storage alloys. Their electrochemical behaviours are advantageous to those of alloys prepared bytraditional methods. Charge discharge test showed that the discharge plateau increased greatly; the cycle life of Mg 1.7 Al 0.3 Ni reached 50 cycles at the current density of 200 mA/g, meanwhile, its discharge capacity maintained over 200 mAh/g. X ray diffraction profiles indicated that with the increasing grinding time, the diffraction peak broadening became more serious, and it remained almost constant after grinding times longer than 12 h. This is because of the occurrence of defects and strains in the alloys. The improvements of electrochemical behaviours were ascribed to the microstructure changes of alloys during the grinding process and partial substitution of Al for Mg in Mg 2Ni.