Effects Of Double Doped CNTs And Ni On The Structure And Electrochemical Properties Of Magnesium-based Hydrogen Storage Materiale

Magnesium based hydrogen storage alloy is one of the most promising hydrogen storage materials because of its hydrogen storage capacity which is up to 7.2wt.%,low price and abundant reserves.However,there are some limitations in the application of magnesium based hydrogen storage materials,such as the high occurrence temperature of hydrogen storage suction and drainage,the poor hydrogen absorption kinetics,poor cyclic stability and many other problems,which limit the application of the material in the hydrogen energy field.In this paper,magnesium based hydrogen storage alloy Mg₂Ni is used as the basis,and carbon nanotubes?CNTs?and Ni are doped to improve the hydrogen absorption and emission performance and cycle stability of magnesium based materials.At the same time,a series of valuable results are obtained by systematic analysis of its mechanism.1.Doped with Ni elements of different proportions in Mg₂Ni-CNTs composite hydrogen storage alloy,the composite material samples doped with 3 wt.%Ni elements and 10 wt.%CNTs reached the maximum discharge capacity of 318.5 mah/g in the LAND cycle test after 5 h vacuum ball grinding.With the increase of Ni elemental doping ratio,the maximum discharge capacity of alloy decreased,but the capacity retention rate of the alloy was positively correlated with the content of Ni elemental.When x=9,the capacity retention rate of the alloy in the electrode reached10%.The doping of Ni elements did not significantly promote the self-discharge performance of the alloy,but the charge retention rate?CRT?of the alloy decreased with the increase of the doping amount of Ni elements.2.The electrochemical performance of 10 wt.%CNTs+3 wt.%Ni+Mg₂Ni alloy electrode was studied with the change of ball grinding time,the results showed that the discharge capacity of 10 wt.%CNTs+3 wt.%Ni+Mg₂Ni alloy electrode gradually increased with the increase of ball grinding time,but the capacity retention rate gradually decreased.The alloy electrode with ball grinding 20h has the maximum discharge capacity of 344 mAh/g,The alloy electrode with grinding 5h has the best capacity retention rate of 5%.3.The high rate discharge?HRD?performance of 10 wt.%CNTs+3wt.%Ni+Mg₂Ni alloy electrode was studied.It was found that the HRD of the alloy electrode increased first and then decreased with the increase of ball grinding time.The alloy electrode HRD of ball grinding for 10 h was the highest.With the increase of discharge current,HRD decreased rapidly.The alloy of ball grinding for 10h decreased from 76.7%of 120 mAh/g to 34.5%of 300mAh/g,with the most obvious decline trend.4.The maximum discharge capacity of the alloy electrode prepared by dry ball grinding method is much higher than that of the electrode prepared by wet ball grinding,reaching 344 mAh/g.The discharge platform of the dry grinding alloy is higher,and the discharge platform of the hydrogen storage alloy prepared by dry grinding method is gradually improved with the increase of ball grinding time.