钇替代镧对La-Mg-Ni系储氢合金晶体结构及其电化学性能的影响

Effect of Substituting Yttrium for Lanthanum on Crystal Structure and Electrochemical Properties of La-Mg-Ni Hydrogen Storage Alloy

通过少量Y对La的取代,研究了La0.75-xYxMg0.25Ni3.17Al0.13和La0.75-xYxMg0.25Ni3.37Al0.13(其中x=0.00,0.05,0.10)体系中Y对合金晶体结构及电化学性能的影响。通过X射线衍射实验、电化学性能测试,结果表明上述两体系主相为Ce2Ni7相、Pr5Co19相。少量的取代对活化性能、最大放电容量影响不大,但对循环稳定性、放氢平台压影响显著,而且在不同主相结构中,影响效果不一样。当x从0.00增大到0.10时:主相为Ce2Ni7相La0.75-xYxMg0.25Ni3.17Al0.13的S80%由222周下降到112周,放氢平台压则由0.015 MPa上升到0.045 MPa;而主相为Pr5Co19相La0.75-xYxMg0.25Ni3.37Al0.13的S80%由172周下降到127周,放氢平台压则由0.019 MPa上升到0.076 MPa。

The effects of partially substituting Y for La on the crystal structure as well as on the electrochemical properties of the La0.75-xYxMg0.25Ni3.17Al0.13 and La0.75-xYxMg0.25Ni3.37Al0.13（x=0.00,0.05,0.10） were investigated by means of powder X-ray diffraction（XRD） and electrochemical measurements.The XRD results suggested that the La0.75-xYxMg0.25Ni3.17Al0.13 were mainly composed of Ce2Ni7-type structure,while the La0.75-xYxMg0.25Ni3.37Al0.13 were mainly composed of Pr5Co19-type structure.By the partially substitution,the activity times and discharge capacity were changed slightly.The Y substitution for La would deteriorate the cycle stability,but raise the desorbing plateau pressure,and the effects of those alterations were different in each structure.In La0.75-xYxMg0.25Ni3.17Al0.13（Ce2Ni7-type）,the S80% decreased from 222 cycles（x=0.00） to 112 cycles（x=0.10）,whereas the desorbing plateau pressure rose from 0.015 MPa（x=0.00） to 0.045 MPa（x=0.10） accordingly.In La0.75-xYxMg0.25Ni3.37Al0.13（Pr5Co19-type）,the S80% decreased from 172 cycles（x=0.00） to 127 cycles（x=0.10）,whereas the desorbing plateau pressure rose from 0.019 MPa（x=0.00） to 0.076 MPa（x=0.10） accordingly.