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用冷坩埚磁悬浮熔炼方法制备La1-xMgxNi2.28(x=0.0～0.6)贮氢电极合金,采用FESEM,EDS,XRD,p-c-t测试及三电极电化学性能测试研究合金的相成分、相结构、p-c-t曲线和电化学性能。EDS结合XRD分析表明,LaNi2.28合金主相为四方结构的La7Ni16相;Mg替代量x为0.3时合金主相为MgSnCu4型的LaMgNi4相,还含有LaNi5和(La,Mg)Ni3相。p-c-t曲线显示,当Mg替代量x不超过0.2时,合金无放氢平台;x为0.3时合金出现明显平台;x为0.5时合金出现两个放氢平台,相应贮氢量达到1.24%(质量分数)。电化学性能测试表明,最大放电容量从100.2 mAh.g-1(x=0.0)增大到329.0 mAh.g-1(x=0.5),然后减小到207.8 mAh.g-1(x=0.6);活化性能改善;高倍率放电性能先降低后提高;循环稳定性S100从84.8%(x=0.0)提高到91.5%(x=0.2),然后降低到63.3%(x=0.5)。
The La1-xMgxNi2.28 (x = 0.0-0.6) hydrogen storage electrode alloy was prepared by cold crucible magnetic levitation melting method. The phase composition, phase structure, pct of the alloy were studied by FESEM, EDS, XRD, Curves and electrochemical properties. EDS combined with XRD analysis shows that the main phase of LaNi2.28 alloy is La7Ni16 phase with tetragonal structure. The main phase of Mg alloy is LaMgNi4 phase of MgSnCu4 and contains LaNi5 and (La, Mg) Ni3 phase when the amount of Mg substitution is 0.3. The pct curve shows that there is no de-hydrogenation platform when the Mg substitution amount x does not exceed 0.2; the obvious platform appears when x is 0.3; and the two hydrogen release platforms appear when x is 0.5, and the corresponding hydrogen storage capacity reaches 1.24% fraction). Electrochemical performance tests showed that the maximum discharge capacity increased from 100.2 mAh.g-1 (x = 0.0) to 329.0 mAh.g-1 (x = 0.5) and then decreased to 207.8 mAh.g-1 ); The activation performance is improved; the high rate discharge performance first decreases and then increases; the cyclic stability S100 increases from 84.8% (x = 0.0) to 91.5% (x = 0.2) and then decreases to 63.3% (x = 0.5).