摘要
Rietveld全谱拟合表明,La_(0.7)Mg_(0.3)(Ni_(0.85)Co_(O.15)(x=2.5,3.0,3.5,4.0,4.5,5.0)型合金主相由(La,Mg)Ni_3和LaNi_5组成,随x的增加,(La,Mg)Ni_3相的丰度从48.4％(x=2.5)增加到78.2％(x=3.5)然后减小到12.2％(x=5.0);LaNi_5相的丰度当x=2.5—3.5时,保持基本不变(约20％),当x值增加到4.0时突然增加到71.9％,随着x增加,合金的吸氢量首先增加然后减小,合金放氢平台压力首先保持基本不变然后增加;合金电极的最大放电容量从228.3 mA·h/g(x=2.5)增加到395.6mA·h/g(x=3.5),然后又减小到226.8 mA·h/g(x=5.0),当放电电流密度I_d=1000 mA/g时,合金电极的高倍率性能从x=2.5时的53.5％提高到x=3.5时的85.8％然后又减小到x=4.5时的73.9％,随着x值的增加,合金电极的电化学反应动力学性能首先增加,达到一个最大值后,其动力学性能又有所下降。
XRD Rietveld analyses show that La0.7Mg0.3 (Ni0.85Co0.15)(x) (x = 2.5, 3.0, 3.5, 4.0, 4.5, 5.0) alloys are consisted of (La, Mg)Ni-3 phase and LaNi5 phase, and the (La, Mg)Ni3 phase content increases from 48.4% (x = 2.5) to 78.2% (x = 3.5) and then decreases to 12.2% (x = 5.0). The LaNi5 phase content maintains unchanged (about 20%) with increasing x from 2.5 to 3.5, and then increases to 71.9% with increasing x up to 4.0. The hydrogen storage capacity increases first and then decreases with increasing x, and the plateau becomes flatter and the plateau pressure first maintains almost unchanged and then increases with increasing x from 2.5 to 5.0. The electrochemical results show that the maximum discharge capacities of the alloy electrodes increase from 228.3 mA.h/g (x = 2.5) to 395.6 mA.h/g (x = 3.5), and then decrease to 226.8 mA.h/g (x = 5.0). Meanwhile, the high rate dischargeability (HRD) increases first and then decreases with increasing x from 2.5 to 4.5. Moreover, the electrochemical reaction kinetic of the alloy electrodes increases first to a maximum and then decreases with increasing x.
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2003年第6期666-672,共7页
Acta Metallurgica Sinica
基金
国家自然科学基金 50131040
关键词
镁基贮氢合金
结构特性
P—C—T曲线
电化学性能
Mg-based hydrogen storage alloy
structure characteristics
P-C isotherm
electrochemical property
