Sn替代Ni对R-Mg-Ni基合金结构和电化学性能的影响

Structure and Electrochemical Properties of R-Mg-Ni-Based Alloys with Sn Substitution for Ni

采用元素替代的方法,研究了Sn元素部分替代Ni元素对La0.72Nd0.08Mg0.2Ni3.4-xSnxAl0.1（x=0-0.14）电极合金结构和电化学性能的影响。通过感应熔炼、退火处理、粉碎过筛后得到合金样品。X射线衍射（XRD）分析表明该合金为多相结构,包括（La,Mg）2Ni7（Gd2Co7型和Ce2Ni7型）、（La,Mg）5Ni19（Pr5Co19型）、（La,Mg）Ni3（Pu Ni3型）和La Ni5相（Ca Cu5型）。结构精修显示合金主相由Gd2Co7型（La,Mg）2Ni7相依次变化为（La,Mg）5Ni19,La Ni5相。恒电流充放电测试表明,合金放电容量最大值为387.4 m Ah·g-1。加入Sn后合金电极的放电容量下降,这与合金中相含量的变化是有关系的。Sn的加入导致合金中高吸氢相（La,Mg）2Ni7相的减少,而吸氢能力相对小的（La,Mg）5Ni19相和La Ni5相含量不断增加。高倍率放电测试表明随着Sn元素加入,高倍率放电性能下降。电化学循环稳定性测试表明随着Sn元素含量的增加,合金电极循环寿命先增加后下降。当Sn含量x=0.06时,在100次电化学循环后放电容量保持率达到最高水平83.8%。

With the method of element substitution, the effects of Sn substitution for Ni on the structure and electrochemical property of La0.72Nd0.08Mg0.2Ni3.4-xSnxAl0.1（x=0-0.14） electrode alloys were investigated. Alloy samples were prepared by induction melt- ing, annealing, pulverization and sieving. X-ray diffraction （XRD） analysis indicated that the alloys consisted of multi-phases, inclu- ding （ La, Mg） 2 Ni7 （ Gd2 Co7, Ce2 Si7 ）, （ La, Mg） 5 Ni19 （ Pr5 C019 ）, （ La, Mg） Ni3 （ PuNi3 ） and LaNi5 （ CaCu5 ）. Structural refine- ment indicated that the main phase varied from Gd2CoT-type （La, Mg）2Ni7 to （La, Mg）5Ni19 and LaNi5. The galvanostatic charge- discharge test indicated the maximum discharge capacity reached 387.4 mAh·g^-1 , and the discharge capacity decreased with the addi- tion of Sn, which was related with the change of phase contents. In fact, the amount of （La, Mg）2 NiT phase with good hydrogen stor- age ability deereased, and that of （La, Mg）5 Nil9 and LaNis phases with relatively worse hydrogen storage ability increased when Sn was introduced. High-rate discharge measurements indicated that the high-rate discharge ability decreased with Sn increasing. The cy- clle measurements indicated that cycle life firstly increased then decreased with the increase of Sn. When Sn content reached x = 0.06, the cyclic retention over 100 cycles was up to 83.8%.