The Research For Al And Graphene Addition On Electrochemical Performance Of The La_1.4Mg_0.6Ni_6.4Co_0.6 Alloys

The alloys were prepared by the high frequency maglev induction furnace under argon atmosphere, then carried on the test of the phase structure, the absorption/desorption properties and the electrochemical performance. This paper mainly studied the effect on the hydrogen storage properties and the electrochemical performance of the alloys after substituting by Al element, adding graphene oxide and graphene.Through changing the relative contents of the Mg and Al to research the effect of after Al element substituting on the La1.4Mg0.6-xAlxNi6.4Co0.6 (x=0.00,0.05,0.10,0.15) alloys. The results show that only LaNi5 phase and La2Ni7 phase coexist in the original alloy, however, there are forming a new LaAlNi4 phase after substituting by Al element. The platform pressures of hydrogen absorption/desorption decrease with the increase of the Al content, at the same time, the maximum hydrogen absorption also shows a trend of degression. From the discharge curves of the alloy electrodes, we can see that the maximum discharge capacity decreases with the increase of Al content. After 80 times charging and discharging tests, the electric capacity retention S80 of the alloy electrodes increase from 56.1%(x=0.00) to 57.8%(x=0.15).Based on the investigation of Al element substituting, through adding different mass fraction of graphene oxide in the alloys to research the effect about graphene oxide adding on the properties of the alloys. It is indicated that the phases do not change when adding the graphene oxide in the alloys. As the increasing of graphene oxide content, the maximum hydrogen absorption amounts decrease, but the platform pressures of hydrogen absorption/desorption increase. We can see that the maximum discharge capacity decreases with the increase of graphene oxide content from the discharge curves of the alloy electrodes. After 80 times charging and discharging cycle tests, the electric capacity retention S8o for all the alloy electrodes are respectively 52.1%(x=0.0wt.%),51.1%(x=1.0wt.%),54.6%(x=2.0wt.%) and 58.9%(x=3.0wt.%), it can be seen that proper amount of graphene oxide can effectively improve the cycle stability of the alloys. The high rate discharge performance H1200 of the corresponding alloys are respectively 42.78%,45.40%, 63.29%and 65.56% under the big discharge current density of 1200mA/g.To research the effect of the graphene, the different mass fraction of graphene were added in the La1.4Mg0.5Al0.1Ni6.4Coo.6 alloys. It can be seen that the mainly phase are LaNi5 phase, La2Ni7 phase and LaAlNi4 phase when no graphene in the alloys, and there is a new C phase after adding the graphene in the alloys. As the increasing of the mass fraction of grapheme, the maximum hydrogen absorption amounts are no much changes for corresponding alloys, but the platform pressures of hydrogen absorption/desorption present a certain increase trend. There are more flocculent graphene between alloy particles with the increasing of grapheme content, which connects part of the alloy particles together. From the discharge curves of the alloy electrodes, we can see that the maximum discharge capacity decreases with the increase of graphene content. After 80 times charging and discharging cycle tests,the electric capacity retention S80 for all the alloy electrodes are respectively 52.1%, 51.6%,52.5% and 53.8%. As the increasing of graphene content, the corresponding high rate discharge performance H1200 of the alloys firstly increase from 42.78%(x=0.0wt.%) to 83.65%(2.0wt.%), and then drop to 59.99%(x=3.0wt.%)under the big discharge current density of 1200mA/g.