La0.7Mg0.3Ni3.4-x(Al0.3Co0.4)0.2+x(x=0~0.3)合金电极电化学性能研究

在氩气保护下,采用悬浮熔炼法制备La0.7Mg0.3Ni3.4（Al0.3Co0.7）x（x=0,0.2,0.4,0.6）储氢合金,用X射线衍射仪测试相组成,并用MDI Jade 5.0软件分析相组成和晶胞参数,用开口三电极法测试电极电化学性能。结果表明,合金相主要由LaNi5、LaMg2Ni9、La2Ni7和LaNi2.28相组成,随着合金中Al和Co含量的增加,合金放氢平台压下降,最大吸氢量为1.43%（x=0）,合金电极最大放电容量Cmax为381mA.h.g-1（x=0）,合金电极100个充放循环后的容量保持率S100从53.0%（x=0）增加到57.1%（x=0.3）,循环稳定性增强。当x=0.1时,合金电极的电化学动力学性能较好。

Study on the Electrochemical Properties of La0.7Mg0.3Ni3.4-x(Al0.3Co0.4)0.2+x (x=0~0.3) Hydrogen Storage Alloy Electrodes

The La0.7Mg0.3Ni3.4-x(Al0.3Co0.4)0.2+x(x=0~0.3) hydrogen storage alloys were prepared by magnetic levitation melting under Ar atmosphere,and the effects of Co and Al on the hydrogen storage and electrochemical properties were systematically investigated.X-ray diffraction(XRD) results showed that the alloy phases mainly consisted of LaNi5,LaMg2Ni9,La2Ni7 and LaNi2.28 phases.Electrochemical P-C isotherms indicated that,with increasing Co and Al contents in alloys,the equilibrium pressure decreased and the maximum hydrogen storage capacity was 1.43%(x=0).The electrochemical measurements showed that the maximum discharge capacity of the alloy electrodes reached to 381 mA·h·g-1(x=0).After 100 charge/discharge cycles,the capacity retention rate of the alloys enhanced from 53.0%(x=0) to 57.1%(x=0.3),and the cycling durability of the alloy electrodes improved with the increases of Co and Al contents.The high rate dischargeability of the alloy electrodes increased first and then decreased with increasing Co and Al contents in alloys.Moreover,the reaction resistance and polarization resistance decreased first and then increased whereas the exchange current density,anodic peak current density,limiting current density and the hydrogen diffusion coefficient first increased and then decreased,with increasing Co and Al contents.The La0.7Mg0.3Ni3.3(Al0.3Co0.4)0.3 alloy electrode possessed better electrochemical kinetic characteristic.