AB_2型LaMgNi_(3.7)M_(0.3)(M=Ni、Al、Mn、Co、Sn、Cu)贮氢合金的晶体结构及电极性能

Investigation on crystal structure and electrochemical properties of LaMgNi_(3.7)M_(0.3)(M=Ni,Al,Mn,Co,Sn,Cu) hydrogen storage alloys

系统研究了LaMgNi3.7 M0.3(M=Ni、Al、Mn、Co、Sn、Cu)合金的组织结构和电化学性能.XRD和电子探针显微分析(EPMA)结果表明:该系列合金主相均为LaMgNi4相,其中含Mn、Cu和Co元素在LaMgNi4合金相中有一定的固溶度,LaMgNi3.7Sn0.3合金中的Sn元素主要以LaNiSn相析出;XRD全谱拟合分析表明:LaMgNi3.7Al0.3中Al元素主要占据在LaNi5相的3g位置.合金化元素在LaMgNi4相中的固溶度从大到小的顺序是Mn＞Cu＞Co＞Al＞Sn.电化学实验表明,该系列合金经1～3次循环即可活化,最大放电容量由245.2mAh/g(M=Sn)变化至293.2mAh/g(M=Co),但合金电极的循环稳定性均较差.合金电极的高倍率放电性能(HRD900%)从大到小依次为Al＞Sn＞Cu＞Mn＞Ni＞Co,其中氢原子在合金中的扩散对合金电极的高倍率放电性能起主要作用.

In this paper, the structure and electrochemical properties of LaMgNi3.7M0.3 （M= Ni, Al, Mn, Co, Sn,Cu） were investigated in detail. It can be found that, by XRD and EPMA, the alloys consist mainly of LaMgNi, phase with the cubic MgCu4Sn structure and the Sn element in the LaMgNi3.7 Sn0.3 alloy emerged mainly with the LaNiSn phase. Rietveld analysis for LaMgNi3.7 A10.3 alloy indicate that substituted Al element primarily occupies 3g position in the LaNi5 phase. The solid solubility of the substituted elements in the LaMgNi4 phase are in sequence of Mn〉Cu〉Co〉Al〉Sn. The electrochemical measurements show that the maximum discharge capacity increases from 245.2mAh/g（M=Sn） to 293.2mAh/g （M=Co）, and the cycle stability are bad except LaMgNi3.7Sn0.3 alloy discharge capacity keep rate at 70% above after 50 cycle numbers. Meanwhile, the high rate discharge abilities of the alloy electrodes were in sequence of Al〉Sn〉Cu〉Mn〉Ni〉CO（Id =900mA/g）. The hydrogen diffusion velocity was controlling factor for the dynamics ability .